Page 1 of 8
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`Samsung Exhibit 1008
`Samsung Electronics Co., Ltd. v. Daniel L. Flamm
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`U.S. Patent
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`MM
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`39912:
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`Sheet 1 of 2
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`H 0,001,145
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`Page 2 of 8
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`_ U.S. Patent
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`Mar. 2, 1993
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`Sheet 2 of2
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`H 0,001,145
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`W.
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`““““““““““““““
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`Page 3 of 8
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`1
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`RAPID TEMPERATURE RESPONSE WAFER
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`CHUCK
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`a total power input of nearly 1500 watts. To maintain
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`the wafer at the desired process temperature requires
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`this amount of heat energy be removed from the wafer
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`during the process. Thus, a substantial difference in
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`temperature (AT) between the wafer and the chuck
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`must be maintained in order to realize the required heat
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`energy extraction from the wafer.
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`In a prior art system utilizing the circulation of cool-
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`ing water, a considerable amount of cooling water flow
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`must be maintained in order to dissipate the heat gener-
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`ated by such energy input. For example, an 1800 W
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`energy input system would require approximately 0.5
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`liter/second (6.6 gallons/minute) flow of cooling water
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`having a AT value of 1” C. from inlet to outlet. Thus,
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`considerable amount of cooling water must be circu-
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`lated in order to dissipate the required energy. Al-
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`though it is possible to substitute other cooling fluids to
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`reduce the required volume of flow of the coolant,
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`significant amount of liquid is still needed and the liquid
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`must be maintained in a closed system for recirculation.
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`In many instances condensation or other processes for
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`reclaiming the liquid is needed within the closed system.
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`Furthermore, with most prior art closed loop sys-
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`tems, fluid passages are typically present within the
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`wafer chuck to circulate the cooling fluid in order to
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`dissipate the heat from the chuck. Additionally,
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`closed loop system, the temperature of the circulating
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`fluid will typically need to be controlled. In some in-
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`stances where an expansion chamber is used, such as in
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`a system utilizing liquid gas which is expanded to re-
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`move the heat, a sophisticated closed loop system must
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`be present in order to control the temperature of the
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`chuck, as well as maintaining the proper flow of a spe-
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`cially designated coolant, other than water, to the wafer
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`In those special processes, such as plasma etch and
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`ECR-CVD processes, additional temperature control
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`problems are encountered. These processes deposit
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`substantial amounts of energy into the wafer and the
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`water must be cooled by the wafer chuck to keep it at
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`the selected process temperature. For example, in one
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`CVD-Si02 deposition process, the temperature of the
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`chuck is controlled to a value in the range of 65' to 90'
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`C. by circulating thermostated liquid through the base
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`of the chuck. If a cold (room temperature) wafer is
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`loaded onto the chuck, the wafer will be heated to the
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`temperature of the chuck within a few seconds. The
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`wafer temperature, however, is still 200'- to 400° C.
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`below the optimum deposition temperature. If the film
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`deposition is begun before the wafer is at this tempera-
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`ture, the quality of the initial layer of the film will be
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`inferior to that deposited at the optimum process tem-
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`perature. Alternatively, with no silane flow into the
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`reactor the plasma can be used to heat the wafer with-
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`out deposition, but at the cost of an additional 15 to 20
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`seconds added to the process. For a 120 second process
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`that represents an increase in process time of about 16%
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`or a proportional decrease in yield in the number of
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`wafers that can be processed per hour.
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`For maximum throughput of the tool in certain high
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`energy processes, such as plasma processes, it is impera-
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`tive that the wafer be brought up to its operating tem-
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`perature as quickly as possible and once the operating
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`temperature has been reached, to remove the process
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`generated heat from the wafer in a controlled manner.
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`_ In order to provide these objectives, it is preferred that
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`a chuck be designed to accommodate the thermal shock
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`of drastic temperature changes of the order of 200°
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`5
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`This application is a continuation of application Ser.
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`No. 587,718, filed on Sep. 25, 1990, now abandoned.
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`BACKGROUND OF THE INVENTION
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`1. Field of the Invention
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`The present invention relates to the field of semicon- 10
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`ductor manufacturing devices and, more particularly, to
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`chucks for controlling water temperature.
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`2. Prior Art
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`In the manufacture of semiconductor integrated cir-
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`cuit devices, various circuit elements are formed in or 15
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`on a base substrate, such as a silicon substrate. Gener-
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`ally, the process of forming these various circuit ele-
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`ments starts from a base wafer, which is typically flat
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`and is circular in shape. On each of these flat circular
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`wafers, a number of integrated circuit devices, typically
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`known as “chips” are formed by the use of various
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`well-known techniques,
`including photolithography,
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`doping, depositing, etching, and annealing techniques,
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`just to name a few.
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`In performing some of these steps, a wafer is placed in
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`a chamber in order for the wafer to undergo a necessary
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`processing step, such as deposition or etching. When
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`these wafers are loaded into a given chamber, the wafer
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`is placed on a wafer chuck, which is a type of semicon-
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`ductor platen. These platens, or chucks, are used to
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`control the wafer temperature during a given process
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`cycle. Because the wafer resides on the platen, by con-
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`trolling the temperature of the platen, wafer tempera-
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`ture can be controlled. Accordingly, elaborate mea-
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`sures have been devised to address the various means
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`available for controlling the temperature of the platen.
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`Some of these prior art techniques are described in U.S.
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`Pat. Nos. 3,501,356; 4,496,609; 3,669,812; 4,542,298;
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`4,628,991;
`4,671,204;
`4,457,359;
`4,282,924;
`and
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`3,835,061. These patents teach a technique of cooling
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`the wafer by circulating liquids, such as water. Either
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`the cooling of the apparatus as a whole is provided by
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`the circulating cooling water, or in more sophisticated
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`systems, channels or passages are provided in the base
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`of the chuck to directly cool the wafer chuck.
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`Another prior art device is described in U.S. Pat. No.
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`in which heat created inside the wafer is
`4,274,476,
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`transferred to an expandable heat pipe, wherein the heat
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`causes the fluid in the heat pipe to boil and vaporize.
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`The vaporizable liquid is inside the cavity for expanding
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`the heat pipe when heated and for transferring heat
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`from one plate to the other. Furthermore, another
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`scheme is described in U.S. Pat. No. 3,724,536, in which
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`a fluid coolant, such as carbon dioxide, undergoes a
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`rapid expansion upon entering an expansion chamber,
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`thereby cooling the conductive element and conse-
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`quently the device under control.
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`In practice, the temperature of the chuck must fre-
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`quently be controlled at a temperature substantially
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`below that of the wafer process temperature, especially
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`when there is substantial energy input into the wafer.
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`Substantial energy input to the wafer will usually occur
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`when processing techniques such as plasma etch, chemi-
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`cal vapor depositions (CVD), and electron cyclotron
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`resonance-chemical vapor deposition (ECR-CVD), just
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`to name a few, are used. In some of these processes, the
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`power input to the water can be as much as 8 W/crnz.
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`As an example, for a 6-inch wafer, this is equivalent to
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`Page 4 of 8
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`3
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`C./sec and yet maintain the ability to dissipate heat
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`energy in order to control the temperature of the wafer.
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`’ In such a design, it is preferable to design an economi-
`cal, yet efficient system, to reach the desired objectives.
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`SUMMARY OF THE INVENTION
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`A wafer chuck which utilizes the latent heat of va-
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`porization of water or other liquids to extract heat to
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`cool the wafer is described. The chuck has a substan-
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`tially flat upper surface for the placement of a semicon-
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`ductor wafer, but the chuck is substantially hollow in
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`the interior. At the lower portion of the chuck, spray
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`mechanisms are positioned into the cavity for spraying
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`liquid in the cavity. The nozzles spray a mist of liquid to
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`the underside surface of the chuck having the wafer 15
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`residing thereon. Upon contact the liquid vaporizes if
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`the chuck temperature is greater than the boiling point
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`of the liquid. Heat extraction from the wafer is en-
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`hanced by using the latent heat of vaporization of the
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`liquid. The operating temperature of the chuck can be
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`established by the selection of a liquid of suitable boiling
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`point. A central exhaust opening is also provided at the
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`lower portion of the chuck to remove vapor from the
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`cavity. When water is used, the steam can be readily
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`exhausted into the air. For other fluids, an external
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`condenser can be used to recycle the fluid.
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`An insulated heater is provided on the upper surface
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`of the chuck, disposed between the chuck and the wa-
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`fer, in order to raise the temperature of the wafer to its
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`operating range. Thus, the wafer can be rapidly brought
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`up to its operating temperature, prior to the commence-
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`ment of the wafer process cycle.
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`BRIEF DESCRIPTION OF THE DRAWINGS
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`FIG. 1 is pictorial view of a wafer chuck of the pres- 35
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`ent invention.
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`FIG. 2 is a cross-sectional view of the wafer chuck of
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`FIG. 1.
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`FIG. 3 is a drawing of the wafer chuck of the present
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`invention, showing the placement of various inlet and 4-0
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`exhaust openings.
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`DETAILED DESCRIPTION OF THE
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`P_REFERRED EMBODIMENT
`A wafer chuck for using the vaporization of water to
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`remove excess heat energy from a semiconductor wafer
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`is described. In the following description, numerous
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`specific details are set forth, such as specific shapes,
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`materials, etc., in order to provide a thorough under-
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`standing of the present invention. It will be obvious,
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`however, to one skilled in the art that the present inven-
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`tion may be practiced without these specific details. In
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`other instances, well-known techniques have not been
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`described in detail in order not to unnecessarily obscure
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`the present invention.
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`The present invention provides for a wafer chuck
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`which is to be utilized in processing wafers in a temper-
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`ature range of -150’ to +500” C. It is especially de-
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`signed for use with processes where substantial energy
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`input to the wafer is encountered, such as during plasma
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`etch, CVD and ECR-CVD depositions, but not neces-
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`sarily limited to these. Although the present invention is
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`described in reference to its use in a plasma environ-
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`ment, it is to be noted that the present invention can be
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`used in non-plasma environment as well.
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`In a typical plasma process a given semiconductor
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`wafer is loaded into a chamber and onto a chuck which
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`is most likely at or near room temperature. Then some
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`H1145
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`4
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`form of heating means will be required to raise the
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`temperature of the wafer to the desired operating point
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`if it is above room temperature. Conversely, if the de-
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`sired operating point is below room temperature, then
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`some form of cooling means, typically that provided by
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`a lower boiling point liquid, will lower the temperature
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`of the wafer below room temperature.
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`Usually, the operating point falls within a tempera-
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`ture range of — 150° to + 500“ C. Some finite amount of
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`time is required to change the wafer temperature from
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`room temperature to the operating temperature. If, in a
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`plasma system, plasma is used to heat the wafer to raise
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`it to the operating temperature, a significant portion of
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`the total process time may be devoted to changing (rais-
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`ing the temperature in this instance) the temperature of
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`the wafer to the desired operating temperature. For
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`process efficiency it is desirable to reach this operating
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`temperature in the minimum amount of time possible, so
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`that critical processing time is not utilized in the prepa-
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`ration stage, but instead is used in the actual plasma
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`processing stage for etching or depositing. However,
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`once the operating temperature has been reached, the
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`temperature of the wafer will continue to rise unless the
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`chuck is capable of dissipating the process generated
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`heat in order to maintain the wafer at a controllable
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`operating temperature. Thus, for an efficient plasma
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`processing operation, the wafer is brought to the oper-
`ating temperature as rapidly as possible by electrical
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`heating. Once the operating temperature has been
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`reached, the plasma process is switched on, the electri-
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`cal heater is switched off and the liquid spray is started
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`to provide cooling of the chuck in order to maintain the
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`wafer at
`the desired operating temperature. When
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`water is used as the cooling liquid, a cooling rate of
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`greater than 200° C./sec can be realized.
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`The wafer chuck of the present invention provides
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`for rapid cooling to quickly change the chuck tempera-
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`ture to maintain the wafer at the desired operating tem-
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`perature when the plasma is switched on in a plasma
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`etching or deposition reactor chamber. Optionally, the
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`chuck of the present invention provides a means for
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`heating the chuck and the wafer by introducing heat
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`energy by the use of an electrical heater to bring the
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`wafer quickly up to its operating temperature. In order
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`to provide for the desired rapid heating and/or the
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`rapid cooling of the chuck, the chuck must be capable
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`of withstanding the severe thermal shock (temperature
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`change per unit time) that the chuck will necessarily
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`undergo during the cooling and heating cycles. The
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`wafer chuck of the present invention provides for these
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`requirements.
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`Referring to FIGS. 1, 2, and 3, a wafer chuck 11 of
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`the present invention is shown. Chuck 11 is a three-di-
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`meusional disk which is circular in shape and substan-
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`tially flat on its upper surface to accommodate a typical
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`circular semiconductor wafer 20. The interior of chuck
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`11 is substantially hollow, thereby forming a cavity 12
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`within. At the lower surface 18 of chuck 11, a plurality
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`of inlet openings 21 are disposed at various predeter-
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`mined locations. Also along the bottom surface 18 of
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`chuck 11, an outlet opening 25 is located. In the pre-
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`ferred embodiment, outlet opening 25 is centrally dis-
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`posed while inlet openings 21 are distributed concentri-
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`cally and having equidistant separation. The actual
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`number and position of the openings 21 are a design
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`choice as long as the cooling constraints below are met.
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`Furthermore, it is to be noted that although the present
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`invention is described in terms of using water as the
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`Page 5 of 8
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`

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`H1145
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`S
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`5
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`cooling liquid, various other liquids ca be readily used
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`without departing from the spirit and scope of the pres-
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`ent invention.
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`A liquid mist spray mechanism 22, such as a means
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`having a jet or a spray nozzl_e 23, is inserted into each of
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`the inlet openings 21. Nozzle (jet) 23 of each spray
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`means 22 can reside within opening 21 without pene-
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`trating into cavity 12 or, alternatively, it can actually
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`penetrate into and reside within the region of cavity 12,
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`as is shown in FIG. 2. The actual height of the penetra-
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`tion of each nozzle 23 into cavity 12 (as well as the
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`number and positioning of tlie nozzles) is a design
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`choice, as long as the liquid mist spray from all nozzles
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`23 covers substantially all of the underside surface area
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`16 of chuck 11. The other end of each spray mechanism
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`22, which end is external to cavity 12, is coupled to a
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`pressurized liquid source. The exhaust opening 25 is
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`coupled to an exhaust pipe 26 which provides a passage
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`for the exhaust gas to an exhaust opening 27.
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`In operation, the pressurized liquid causes each spray
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`mechanism 22 to spray liquid in form of a mist to the
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`underside 16 of chuck 11. If the chuck 11 is above the
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`liquid temperature,
`the liquid will vaporize upon
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`contact. The vaporization causes heat to be extracted
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`from chuck 11. The cavity 12 provides for the expan-
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`sion to take place when liquid is vaporized to gas. The
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`gas is then exhausted through opening 27 without the
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`use of forced exhaust and/or vacuum. In the preferred
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`mode, water is expanded and exhausted as steam.
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`The actual number and placement of the spray mech-
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`anisms 22,
`is a design choice, as long as the spray 24
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`from nozzles 23 are capable of spraying all of the under-
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`side surface 16 of chuck 11. As shown in FIG. 3, the
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`preferred embodiment has eight openings 21 disposed
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`radially in a circular pattern about the center of chuck
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`11. Each of the nozzles 23 cover a certain predeter-
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`mined area of the underlying surface 16, such that all of
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`the eight nozzles 23 are capable of spraying, substan-
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`tially all of the underlying surface 16 of chuck 11.
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`The chuck 11 of the preferred embodiment is con-
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`structed from stainless steel. The other associated ele-
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`ments 22, 23, and 26 are also constructed from stainless
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`steel in order to have the same expansion properties as
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`chuck 11. For operation below room temperature, alu-
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`minum alloys or copper can be used. Two factors affect
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`the choice of materials for the body of the chuck. The
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`material of the chuck must be compatible with the
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`chosen fluid over the temperature range of operation.
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`For example, aluminum and water may not be a com-
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`patible combination at higher temperatures. The second
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`factor is the thermal expansion coefficient of the chuck
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`material. The thermal expansion of the chuck materials
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`must match closely the thermal expansion coefficient of
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`55
`the insulating materials bonded to the top of the chuck.
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`Overlying the upper surface of chuck are two insulat-
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`ing layers 13 and 14 having a heating layer 15 dispose
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`there between. A wafer 20 is then positioned onto the
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`upper insulating layer 14. The purpose of the insulating
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`layers 13 and 14 is to provide insulation between the
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`heater element 15 and the chuck 11, as well as the heater
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`element 15 and wafer 20.
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`The purpose of the heater element 15 is to rapidly
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`heat the wafer 20 to raise the temperature of the wafer
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`from room temperature to the operating temperature as
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`rapidly as possible prior to the turning on of plasma
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`energy. The preferred embodiment uses electrical en-
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`ergy, wherein heater element 15 converts this electrical
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`6
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`energy to heat energy. A variety of well-known materi-
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`als can be readily used for element 15. Some of these are
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`described below. The insulating layers 13 and 14 of the
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`preferred embodiment are constructed from a cermet
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`material. Cerment materials are used because of the
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`property of readily transferring heat, while providing
`the necessary insulation of the electric heater element
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`15.
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`Some of the heater/cermet combinations are tungsten
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`electrode embedded in a Ti-Alumina cermet, platinum
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`with a Pt—Alumina cermet, or Nichrome (or Ni-Cr al-
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`loy) with Cr-Alumina cermet. A critical consideration
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`is to match the coefficient of thermal expansion of the
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`heater material and the associated cermet. A desirable
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`feature of the heater material is to have a low tempera-
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`ture coefficient of resistance. It is to be noted that other
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`combinations can be readily used.
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`When the process temperature is above room temper-
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`ature, the present invention provides for the wafer 20 to
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`be rapidly heated to the process operating temperature
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`and once that temperature is reached, it provides for the
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`extraction of excess heat energy when the plasma is
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`turned on. In practice, the preferred embodiment
`is
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`capable of heating the chuck 11 from room temperature
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`to an operating temperature of 100° to 500° C.
`in a
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`matter of seconds, due to the low thermal mass heater
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`employed. Then, once the plasma is switched on, the
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`present invention is capable of quickly lowering the
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`chuck temperature by the use of latent heat of vaporiza-
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`tion of liquid.
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`The cooling means takes advantage of the large latent
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`heat of vaporization of the liquid applied as a mist (i.e.,
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`suspension of tiny liquid droplets). The quantity of liq-
`uid vaporized in g/s for a unit heat input per unit area (1
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`_ W/cm?) is
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`40
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`L".
`I
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`___ _g_
`)1‘;
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`(Equation 1)
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`where m is the mass of the liquid vaporized in grams, t
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`is the time in seconds, q is the heat input per unit area
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`per second (W/cm2=J/s—cm2), and hp is the heat of
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`vaporization of the liquid in Joules/Swhi. The volume
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`flow of liquid that is vaporized by the unit heat input
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`per unit area is
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`(Equation 2)
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`where p is the density of the liquid at 25° C. in g/cm3.
`The volume of gas exhausted to the atmosphere (press-
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`ure=l atm) at ambient temperature ('1' =25’ C. or 298
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`K) is
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`V“, =
`-3- x 0.0B2T x so
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`(5‘l““‘°“ 3)
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`where M is the molecular weight in g/mol, 0.082 is the
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`gas constant in liter-atm/mol-K, T is the temperature in
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`K, and 60 converts the flow rate tk standard liters per
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`minute (SLM). As an example, four liquids of different
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`boiling points that might be used as the liquid for the
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`wafer chuck of the present invention is provided in
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`Table 1 below. The last two columns of Table 1 give the
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`volumes of gas for two different heat
`inputs of 1
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`W/cm? and 8 W/cm? for a 150-mm-diameter wafer.
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`Page 6 of 8
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`

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`H1145
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`Boiling
`Point
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`('0)
`
`— 196
`— 40
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`100
`
`I97
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`Heat of
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`Vaporization
`
`(J/g)
`
`199
`232
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`2260
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`800
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`Liquid
`
`Nitrogen
`Freon TM —R-22
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`Water
`
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`Ethylene glycol
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`TABLE 1
`
`Volume of
`
`Liquid for
`
`
`1 W/cmz
`
`
`(cm3)
`
`6.2 E-03
`3.6 15-03
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`
`4.4 E—O4
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`1.1 E-03
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`Volume of
`Gas for
`
`
`l W/cmz
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`(SLM)
`
`2.6 13-01
`7.3 E-02
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`3.6 15-02
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`29 E02
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`V (gas SLM)
`for 150-mm Wafer
`
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`
`
`@ 8 W/cmz
`@ 1 w/cm!
`
`
`47.9
`383.1
`106.4
`13.3
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`6.5
`52.5
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`5.4
`3.0
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`Since, for water
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`h,=226O j/gm
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`(Equation 4)
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`with a heat energy input (q;,,) of 8 w/cmz into a 150 mm
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`diameter wafer is:
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`9In=14l3.7 watts (j/s)
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`(Equation 5)
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`This will be balanced by the heat extracted (qom) by
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`the vaporizing the water, which is defined by:
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`qin - 9014! = 0
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`and
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`LL
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`9aut = by 1
`
`(Eql-"‘“i°" 6)
`
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`(Equation 7)
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`To extract this quantity of heat will require:
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`(Equation 8)
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`signifying the
`In calculation m/t=O.626 _gm/s,
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`amount of water required to extract heat. Since the
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`density of water p is 1 gm/cm3, the volume of liquid
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`water evaporated and, therefore, which must be sup-
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`plied is (m/t)/p=0.627 cm3/s.
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`For a 120 second plasma process, the volume of
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`40
`water required to maintain the chuck temperature at
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`100° C. is 75.3 cm3.
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`The volume of gas (steam) that will be generated by
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`the vaporization of 75.3 cm3 of water can be readily
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`calculated. The number of moles of vaporized liquid is:
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`0.626 gm/18 gm/mol=3.48 X 104 rnols/s
`(Equation 9)
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`cool the chuck temperature. It is the latent heat of va-
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`porization of water which provides the rapid cooling.
`For certain liquids, such as water or nitrogen, no spe-
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`cialized reclamation process and/or system is needed
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`(although one can be utilized) and the converted gas
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`can be readily exhausted to the atmosphere. Thus, a
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`closed loop system need not be required.
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`However, with certain liquids, recovery may or will
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`be necessary. For example, because of the expense and
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`possible environmental problems with exhausting Fre-
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`ons TM or ethylene glycol to the atmosphere, at recov-
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`ery condenser and recycling system will prove most
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`practical. Although specific examples are detailed in
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`Table 1, other liquids can be used to practice the present
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`invention. Water is particularly desirable because of its
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`large heat of vaporization,
`it is inexpensive and it is
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`environmentally acceptable to exhaust
`to the atmo-
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`sphere as steam.
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`Further, it is to be appreciated that a variety of heat-
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`ing and insulating elements can be used for the elements
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`13-15 of the present invention for heating the chuck to
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`rapidly raise the temperature of the wafer to its process
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`operating temperature. Due to properties exhibiting
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`good thermal shock resistance, as well as good electri-
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`cal resistance, cermet materials are recommended.
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`Thus, a rapid temperature response wafer chuck is
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`described.
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`I claim:
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`1. An apparatus for cooling a semiconductor wafer
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`disposed thereon comprising:
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`a body for having said semiconductor wafer reside
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`thereon and said body having a hollow cavity
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`therein;
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`spray means coupled to said body and disposed
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`within said cavity for spraying a liquid to at least a
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`portion of an interior surface of said cavity which
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`is proximal
`to said semiconductor wafer, but
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`wherein said liquid is prevented from physically
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`contacting said wafer;
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`said liquid for extracting heat from said wafer by the
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`use of latent heat of vaporization of said liquid
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`when said liquid is sprayed onto said portion of said
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`interior surface of said cavity and is vaporized
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`upon contact with said interior surface of said cav-
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`ity, such that said wafer is maintained at a predeter-
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`mined temperature;
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`exhaust means coupled to said cavity of said body for
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`exhausting vaporized liquid from said cavity.
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`2. The apparatus of claim 1 further including heating
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`means coupled to a surface of said body upon which
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`said semiconductor wafer resides, wherein said semi-
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`conductor wafer is disposed onto said heating means
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`and said heating means is utilized to rapidly heat said
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`semiconductor wafer to a predetermined temperature.
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`3. The apparatus of claim 1 wherein said apparatus
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`utilizes wafer as said liquid.
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`Using the perfect gas law
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`(Equation 10)
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`where R=0.082 liter-atm/mole-K,
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`T=373.l5K (100° C.), and P=l atm,
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`V
`so that V=849 std. cm3/s,
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`which is approximately 51 standard liters/min.
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`By the application of the above formulated steps, the
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`amount of liquid input, as well as the resultant gas ex-
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`haust, can be readily calculated for various temperature
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`differences. The particular exampl