US006063710A
`6,063,710
`(114) Patent Number:
`United States Patent 55
`Kadomuraet al.
`[45] Date of Patent:
`May16, 2000
`
`
`[54] METHOD AND APPARATUS FOR DRY
`ETCHING WITH TEMPERATURE CONTROL
`
`[75]
`
`Inventors: Shingo Kadomura; Tomohide Jozaki;
`*
`*
`shinsuke Hirano,all of Kanagawa,
`apan
`
`[73] Assignee: Sony Corporation, Tokyo, Japan
`
`[21] Appl. No.: 08/804,412
`
`[22]
`
`Filed:
`
`Feb. 21, 1997
`
`[30]
`
`Foreign Application Priority Data
`
`Feb. 26, 1996
`Mar. 4, 1996
`
`[IP]
`[JP]
`
`Japan vccsscsssssetescsscsssssseeeseesss 8-037691
`Japan wo. cess seeeneeeee 8-045868
`
`Tint, Cdn eeeeeccceeeeecccesnneeeceeeeeseeene HO1L 21/302
`[SL]
`[52] U.S. Che occ eeceeeeseeseenteees 438/715; 438/733
`[58] Field of Search occ 438/695, 696,
`438/714, 715, 733, 738
`
`[56]
`
`References Cited
`U.S. PATENT DOCUMENTS
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`4,971,653
`5,320,982
`5,584,971
`5,605,600
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`11/1990 Powell et al. oe eeeeees 216/59
`«. 437/228
`6/1994 Tsuboneet al.
`.
`
`12/1996 Komino wcscecsssecssssesssseessseeeeenee 216/59
`2/1997 Muller et al. oe 216/67
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`5,681,780 10/1997 Mihara et al.
`....scsssssssssssesseee 437/228
`5,711,851
`1/1998 Blalock et al.
`.
`.. 156/643.1
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`5,900,105
`5/1999 Toshima vsccsessessssssssssseseeen 156/345
`
`
`2oebed
`5)909 pewahara et al
`eed
`TANKNET oo. eeeeeeetceecenceeeeeee
`3928,
`5,981,913
`11/1999 Kadomura et al. sesso 219/444.1
`
`6,004,882 12/1999 Kim et al.
`cececcccccscccsssesseseeeeee 438/706
`12/1999 Kumihashiet al. oe 216/67
`6,008,133
`FOREIGN PATENT DOCUMENTS
`
`4302141A 10/1992
`
`Japan .
`
`Primary Examiner—Randy Gulakowski
`Assistant Examiner—Anita Alanko
`
`Attorney, Agent, or Firm—Hill & Simpson
`
`[57]
`
`ABSTRACT
`
`Amethod of dry etching treatment capable of attaining both
`high selectivity and fine fabrication at a high accuracy
`simultaneously is provided, in which an etching treatment
`comprising a plurality of steps are applied to a specimen W
`in one identical processing apparatus, and the temperature of
`the specimen is changed between etching of one step and
`etching of another step succeeding thereto, among the plu-
`rality of the steps, thereby applying etching at temperatures
`different between the one step and the step succeeding
`thereto.
`
`16 Claims, 4 Drawing Sheets
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`POOPOTPOTPITS
`KSXNSAANSSSAASSO
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`Page | of 12
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`Samsung Exhibit 1005
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`Page 1 of 12
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`Samsung Exhibit 1005
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`U.S. Patent
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`May16, 2000
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`Sheet 1 of 4
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`6,063,710
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`FIG.1A
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`6,063,710
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`U.S. Patent
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`May16, 2000
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`Sheet 3 of 4
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`6,063,710
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`FIG.
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`3A
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`52
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`50
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`50a
`53
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`52
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`FIG.
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`3B
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`FIG.
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`3C
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`U.S. Patent
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`May16, 2000
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`Sheet 4 of 4
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`6,063,710
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`FIG. 4
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`6,063,710
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`2
`Thatis, if a bias applied to a substrate is lowered in order
`to ensure the selectivity relative to the underlying material,
`since the side wall protection film is thin and, accordingly,
`weak, occurrence of side etch or notching is inevitable. On
`the other hand, if the applied bias is increased in order to
`ensure the shape, selectivity relative to the underlying mate-
`rial is deteriorated.
`
`10
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`15
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`As a technique capable of overcoming the problem that
`the selectivity and the shape are in a trade-off relation and
`capable of attaining both the selectivity and the anisotropic
`shape simultaneously, a so-called low temperature etching
`technique of cooling the wafer to a temperature lower than
`0° C. during etching has been proposed.
`The low temperature etching technique has been
`disclosed,
`for example, as an invention made by K.
`Tsujimoto in Proceedings of Symposium of Dry Process
`(Oct. 24-25, 1988, Tokyo), p.p. 42-49.
`In this technique, radical reaction is suppressed by low-
`ering the specimen temperature, so that anisotropy can be
`ensured even under a low substrate bias.
`
`1
`METHOD AND APPARATUS FOR DRY
`ETCHING WITH TEMPERATURE CONTROL
`
`BACKGROUND OF THE INVENTION
`
`1. Field of the Invention
`
`The present invention concernsa dry etching method used
`mainly for the production of semiconductor devices and,
`more in particular, it relates to a method and an apparatus for
`dry etching providing compatibility for anisotropic fabrica-
`tion and highselectivity.
`2. Description of the Related Art
`In recent years, a demandfor fine fabrication in super LSI
`has become severer and it is indispensable, for example, in
`etching treatment, a processing method of providing com-
`patibility for fine fabrication at high accuracy with mini-
`mized dimensional conversion tolerance and high selectivity
`to underlying material.
`However,in a case of plasma etching materials other than
`oxide films, an anisotropic shape has been ensured as is
`well-knownby the presence of a so-called side wall protec-
`tion film. The side wall protection film is formed by the
`deposition, on the side wall of a pattern of various deposits
`including organic polymers which are formed whenreaction
`products formed during plasmaetching are dissociated again
`in the plasmas andthey serve to protect the side wall of the
`pattern and prevent the side wall from being etched.
`By the way, since the side wall protection film is formed
`by the deposits from the reaction products, when a pattern
`formed by etching is convex andif the width of the pattern
`is fine,
`the thickness of the side wall protection wall is
`relatively increased excessively, making the width of the
`entire pattern larger than a desired width. In the same
`manner, when a pattern formed by etching is of a concave
`recess and if the width is narrow, the thickness of the side
`wall protection film is relatively increased excessively, mak-
`ing the entire pattern width narrower than a desired width.
`Accordingly, as various kinds of patterns have been made
`finer and the with of the pattern is madefiner (narrowed) as
`described above, the dimensional accuracy of the obtained
`pattern is lowered when if it
`is intended to ensure the
`anisotropy of etching by utilizing the side wall protection
`film.
`
`Page 6 of 12
`
`However, even the low temperature etching technique has
`the following disadvantages.
`At first, fabrication is difficult to a material such as W
`polyside in which vapor pressures of reaction products are
`different. This is because the vapor pressure of reaction
`products such as WCL, and WO,Cl, formed uponetching of
`WSi, is low, etching for WSi, can not be applied if the
`temperature of the specimen is lowered to such a tempera-
`ture as convenient for etching the polysilicon.
`Secondly, deltaT (difference between a temperatureset for
`a specimen stage and a wafer temperature) is increased upon
`etching. That is, although temperature loweringis effective
`for ensuring the selectivity relative to the underlying Si, for
`example, in the fabrication of contact holes, since tempera-
`ture lowering results a contact hole of a tapered shape due
`to deposition of an excessive polymer, so that setting for the
`low temperature condition is difficult as described above
`and, in addition, incident energy has to be increased inevi-
`tably in order to disconnect Si—O bondsin the fabrication
`of contact holes, which results in the increase of deltaT.
`Accordingly, because of the disadvantage described
`above, even the low temperature etching can be applied
`actually only at a halfway temperature. In order to overcome
`such a disadvantage, it may be considered to vary the setting
`temperature for a specimen comprising, for example, a
`wafer between etchings for materials having different vapor
`pressures of reaction products or between just etching and
`overetching. However, the temperature can not be changed
`within a short time in an existent cooling system by a chiller
`using a liquid such as fluorinate as a coolant and,
`accordingly, existent low temperature etching can not be
`practiced at a temperature to provide a sufficient effect
`inherent
`to the low temperature etching technique as
`described above.
`
`SUMMARYOF THE INVENTION
`
`35
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`45
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`60
`
`In order to overcome such a disadvantages,it has recently
`been attempted andattracted attention to apply etching while
`conducting exhaustion at high speed thereby ensuring a
`dimensional accuracy.
`In the high speed exhaustion process, a pump of a higher
`exhaustion speed than that of existent etching apparatus is
`attached, and conductanceof the etching gas is improvedto,
`whereby the residence time of an etching gas during etching
`is shortened and dissociation of the reaction products in
`plasmasis suppressed during etching. According to the high
`speed exhaustion process, since the amount of deposits by
`redissociation of the reaction products can be decreased
`significantly, the absolute value for the dimensional conver-
`sion tolerance and variation thereof can be suppressed
`It is an object of the present invention to provide a dry
`extremely effectively.
`etching method capable of attaining both high selectivity
`However, in the high speed exhaustion process described
`and fine fabrication at high accuracy simultaneously, as well
`above, since the reaction products are exhausted rapidly, a
`as an apparatus for manufacturing a semiconductor device
`supply source for the side wall protection film is decreased
`capable of actually putting the low temperature etching
`and the side wall protection film of a satisfactory thickness
`technique into practical use.
`is not formed, the anisotropic shape can not be ensured
`65
`
`enough, so that it results in an additional problem that the In accordance with a dry etching methodasafirst aspect
`configurational accuracy of the pattern obtained upon apply-
`of the present invention, the foregoing object can be attained
`ing overetching is worsened.
`by applying an etching treatment comprising a plurality of
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`Page 6 of 12
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`6,063,710
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`3
`steps to a specimen within an identical processing apparatus,
`wherein the temperature of the specimenis changed between
`etching in one step and etching in the succeeding step,
`thereby applying etching at temperature different between
`the one step and the succeeding step.
`That is, according to the dry etching method, since the
`specimen temperature is changed between the etching in one
`step and etching in the succeedingstep, if a main etching as
`the one step is applied at a normal
`temperature, and
`overetching as the succeeding step is conducted at a low
`temperature for instance, since radical reaction can be sup-
`pressed during overetching by temperature lowering even if
`the thickness of the formed side wall protection film is thin,
`so that
`it can endure resultant excessive radical attack.
`Accordingly, due to the radical reaction suppressing effect
`by the temperature lowering, even if the bias applied to the
`specimen is lowered, formation of undercut or notching can
`be prevented.
`Further, since each of the etching treatments is conducted
`within an identical processing apparatus, the time for the
`change of the specimen temperature between the steps can
`be shortened.
`
`the foregoing object can be attained in a dry
`Further,
`etching method in accordance with the second aspect of the
`present invention by applying an etching treatment compris-
`ing plurality of steps repeatedly to a plurality of specimens
`respectively in a dry etching method, wherein the method
`comprises changing the temperature of a specimen by
`changing the temperature of a specimen stage supporting the
`specimen between etching in the initial step and etching in
`the final step of the steps described above, applying etching
`at different temperatures betweenthe initial step andthe final
`step, and changing the temperature of the specimenstage to
`a setting temperature for the specimen in the etching at the
`initial step after the completion of the etching at the final
`step and before putting of a next specimen into the process-
`ing apparatus.
`According to the dry etching method, since the etching
`treatment is conducted at temperatures different between the
`etching atthe first step and etching atthe final step, the same
`effect as in the first feature of the present invention can be
`obtained and, since the temperature of the specimenstage is
`changed to the setting temperature for the specimen in the
`etching at the initial step after the completion of the etching
`at the final step and before putting the next specimen in the
`identical processing apparatus, the time from the completion
`of etching for a specimen tothe start of etching for the next
`specimen can be shortened.
`Further, the foregoing object can be solved by an appa-
`ratus for producing a semiconductor device in accordance
`with third aspect of the present invention, having a vacuum
`chamber in which a specimen stage equipped with a cooling
`means is disposed at the inside and a plasma generation
`means disposed in the vacuum chamber for generating
`plasmas for processing a semiconductor substrate by gen-
`erating plasmas while controlling the temperature of a
`semiconductor substrate placed on the specimen stage by
`cooling the specimen stage by the cooling means, wherein
`the cooling meansusesa liquefied gas or a gas as a coolant,
`a flow channel of the coolant is formed by disposing in
`parallel a plurality of pipelines of different diameters at a
`position before flowing to the specimen stage, and the
`specimen stage is cooled by flowing the coolant through the
`pipelines to the specimen stage, and the cooling means has
`a control meansdisposed for controlling the flow rate of the
`coolant to each of the plurality of pipelines.
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`4
`In the apparatus for producing the semiconductor device,
`since the temperature of the semiconductor substrate on the
`specimen stage is controlled (cooled) by using a coolant
`comprising a liquefied gas or a gas, more rapid cooling is
`possible as compared with an existent cooling method using
`a liquid as the coolant. That is, while it is basically desirable
`to supply a great amountof coolants at a temperature as low
`as possible for rapid temperature lowering, if the liquid is
`used for the coolant as usual, it is difficult to supply a great
`amountof the coolant since the viscosity thereof is increased
`at a low temperature failing to attain sufficient heat
`exchange. Onthe other hand,in the present invention, since
`a liquefied gas or gas is used as the coolant as described
`above in the present invention, supply of a great amount of
`the coolant is not inhibited by the increase of the viscosity,
`so that the coolant can be supplied in a sufficient amount to
`enable rapid cooling to a desired temperature.
`to the
`Further, since the flow channel of the coolant
`specimenstage is formed by arranging in parallel a plurality
`of pipelines of different diameters and the flow rate of the
`coolant to each of the pipelines is controlled by the control
`means, a desired flow rate can be controlled reliably and
`briefly, for example, by selecting a pipeline for flowing the
`coolant
`in accordance with a required flow rate and,
`accordingly, the flow can be controlled at a higher accuracy
`thereby enabling finer temperature control compared with a
`case of forming the flow channel by one pipeline and
`controlling the degree of cooling by adjusting the flow rate
`of the coolant flowing through the pipeline.
`In the dry etching method as defined in thefirst feature of
`the present invention, since the specimen temperature is
`changed between etching in one step and etching in a
`succeeding step, when the main etching is conducted as one
`step at a normal temperature, while overetching is conducted
`as the succeeding step at a low temperature for instance,
`since radical reaction can be suppressed in the overetching
`even if the thickness of the formed side wall protection film
`is thin the radical reaction can be suppressed as described
`above by the temperature lowering, it can withstand exces-
`sive radical attack resulted. Accordingly, due to the effect of
`suppressing the radical reaction by the temperature
`lowering, evenif the bias applied to the specimenis lowered,
`formation of undercut or notching can be prevented. Thus,
`it is possible to attain both the high selectivity and ensurance
`of anisotropic shape,thatis, fine fabrication at high accuracy
`simultaneously.
`Further, since each of the etching treatments is conducted
`in the identical processing apparatus, the time for the chang-
`ing the specimen temperature between the steps can be
`shortened. Accordingly, if the change of the specimen tem-
`perature is conducted about within a time required for a
`series of operations, for example, interruption of electric
`discharge or alternation of etching gases betweenthe steps,
`dry etching treatment comprising a plurality of steps can be
`applied without deteriorating the throughput.
`In the second feature of the method of dry etching
`accordingto the present invention, since etching treatmentis
`conducted at different temperatures between the etching of
`the initial step and the etching of the final step, the same
`effect as that in the first feature can be obtained. Further,
`whenthe etching ofthe final step has been completed, since
`the temperature for the specimen stage is changed previ-
`ously to a setting temperature for the specimenin the etching
`of the initial step, before putting the next specimen in the
`identical processing apparatus, the time from the completion
`of etching for one specimento the time starting the etching
`for the next specimen can be shortened, by which the
`productivity can be improved.
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`6,063,710
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`5
`Further, in the apparatus for producing the semiconductor
`device according to the present invention, since the coolant
`comprising a liquefied gas or a gas which can be supplied in
`a great amounteasily is used as the coolant, by which the
`semiconductor substrate (specimen) on the specimenstage is
`cooled,
`the semiconductor substrate can be cooled more
`rapidly compared with the existent cooling method using the
`liquid as the coolant and, accordingly, the semiconductor
`substrate can be controlled to a desired temperature in a
`short period of time.
`Furthermore, since the temperature for the semiconductor
`substrate can be controlled in a short period of time, it is
`possible to attain both the high selectivity and ensurance of
`the anisotropic shape,that is, fine fabrication at high accu-
`racy simultaneously by applying twostep etching treatment,
`that is, main etching at a normal temperature and overetch-
`ing at a low temperature also, for example, to W polycide
`having different vapor pressures for reaction products. In
`addition, since the temperature of the semiconductor sub-
`strate can be changed rapidly in a short period of time
`between the steps, the temperature can be changed about
`within a time required for a series of operations such as
`interruption of electric discharge or alteration of etching
`gases between the steps and, accordingly, the dry etching
`treatment comprising a plurality of steps can be conducted
`rapidly without lowering the throughput.
`Further, since the flow channel for the coolant to the
`specimenstage is formed by arranging in parallel a plurality
`of control pipelines of different diameters and adjusting the
`flow rate of the coolant to each of the pipelines by a control
`means,if the control degree of the control meansis control,
`for example, by disposing a feed back control meansor data
`base control means, the flow rate of the coolant supplied to
`the specimen stage can be controlled reliably and instanta-
`neously to a desired amountand, accordingly, the flow rate
`can be controlled at a higher accuracy compared with a case
`of forming the flow channel with one pipeline and control-
`ling the cooling degree by adjusting the flow rate of the
`coolant flowing through the pipeline, by which finer tem-
`perature control is possible to enable higher accuracy for the
`etching fabrication.
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`FIGS. 1A-1C are cross sectional side elevational views
`
`for a main portion for explaining a first embodimentof a dry
`etching method according to the present invention in the
`order of processing;
`FIGS. 2A-2C are cross sectional side elevational views
`for a main portion for explaining a second embodiment of
`the dry etching method according to the present invention in
`the order of processing;
`FIGS. 3A-3C are cross sectional side elevational views
`
`for a main portion for explaining a third embodimentof the
`dry etching method according to the present invention in the
`order of processing;
`FIG. 4 is a schematic constitutional view illustrating one
`embodiment of applying the apparatus for producing the
`semiconductor device according to the present invention to
`a plasma etching apparatus; and
`FIG. 5 is a schematic constitutional view for a cooling
`control section and a periphery thereof.
`DETAILED DESCRIPTION OF THE
`PREFERRED EMBODIMENTS
`
`A dry etching method according to the present invention
`will be explained more in details.
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`6
`Atfirst, a first embodiment of the dry etching method
`according to the present invention will be explained with
`reference to FIGS. 1A-IC.
`
`This method is an example of applying the method
`according to the present invention to a methodoffabricating
`a W polycide by a two step etching treatment. That is, as
`shown in FIG. 1A in this embodiment, a W polycide
`comprising a polysilicon layer 32 and a WSi, layer 33 is
`formed on a SiO,film 31 on a silicon substrate 30, on which
`a photo-resist pattern 34 is further formed to prepare a
`specimen W. The W polycide of the specimenis fabricated
`by etching into a pattern shape corresponding to the photo-
`resist pattern 34,
`in which main etching is applied at a
`normal
`temperature as the first step and overetching is
`applied at a low temperature as the succeeding secondstep.
`
`Atfirst, main etching of the first step is applied at a normal
`temperature (20° C.) under the following conditions to
`remove the WSi, layer 33 and the polysilicon layer 32 by
`etching to a state of partially leaving the polysilicon layer 32
`as shownin FIG. 1B.
`
`First Step (Main Etching)
`Etching gas: Cl,0, 50/10 SCCM
`Pressure: 5 mTorr
`Source power-1 (RF antenna 4): 2500W (13.56 Hz)
`Source power-2 (RF antenna 3,3): 2500W (13.56 Hz)
`RFbias: 100W
`Specimen temperature: 20° C.
`For the control of the specimen temperature in this
`embodiment, a heater (not illustrated) of an electrostatic
`chuck provided to a stage 12 to be described later and
`cooling by a chiller 17 are applied in combination, and the
`specimen temperature is controlled finely by the cooling
`control of a control device 23.
`
`Then, for applying overetching of the second step suc-
`ceeding to the first step, electric discharge in the etching
`device is once disconnected, and gases remaining in a
`diffusion chamber 2 are exhausted. Then, an etching gas
`used in the second step to be describedlater (a gas identical
`with that in the first step is used in this embodiment) is
`introduced into the diffusion chamber, and the gas is stabi-
`lized and the inside of the diffusion chamber2 is controlled
`
`to a constant pressure. Further, during a series of such
`operations,
`that
`is, directly after the completion of the
`etching of the first step, an electronic control valve 22 for a
`by-pass pipeline 21 in the cooling system by the chiller 17
`is wholly closed, and an electronic control valve 20 for the
`coolant pipeline 15 is opened wholly, and the gas coolant at
`-140° C. from the chiller 17 is supplied to the stage 12 to
`rapidly cool the specimen W.
`Then, the temperature of the specimen W reached —30°
`C., which is an etching temperature to be described later
`within a short period of time of about 30 sec by such rapid
`cooling. In this case, since the series of operations described
`above,
`that,
`is a series of operations of interrupting
`discharge, exhausting remaining gases in the diffusion
`chamber 2 and, further, introducing and stabilizing a fresh
`etching gas take a time equal with or more than the time
`required for rapid cooling, the time required for the rapid
`cooling does not constitute a factor of delaying the time
`required for the etching treatment of the specimen W.
`Successively, discharging is applied again to conduct
`overetching of the second step at a low temperature (-30°
`C.) under the following conditions, and a portion of a
`polysilicon layer remaining being disposed on the Si02 film
`32 is removed by etching as shown in FIG. 1C.
`
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`6,063,710
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`7
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`Second Step (Overetching)
`Etching gas: Cl,0, 50/10 SCCM
`Pressure: 5 mTorr
`Source power-1 (RF antenna 4): 2500W (13.56 Hz)
`Source power-2 (RF antenna 3): 2500W (13.56 Hz)
`RF bias: 20W
`Specimen temperature: —30° C.
`Whenthe overetching is thus applied, since the etching is
`a treatment under the low temperature, radical reactions can
`be suppressed by the temperature lowering even if the
`formed side wall protection film is thin and, accordingly,it
`is possible to withstand excessive radical attack and sup-
`press the occurrence of undercut or notching even if the bias
`applied to the specimen is lowered from 100W in the first
`step to 20W. Accordingly, sufficient anisotropic shape can be
`ensured as shown in FIG. 1C while keeping selectivity to
`higher than 100 with no effect on the shape even under 100%
`overetching.
`In the dry etching method described above, it is possible
`to attain both the high selectivity and ensurance for the
`anisotropic shape, that is, fine fabrication at high accuracy
`and, in addition, the temperature for the specimen can be
`changed easily and in a short period of time by conducting
`each of the steps in one identical etching device, so that the
`temperature can be changed about within a period of time
`required for a series of operations such as interruption of
`discharge or alteration of etching gases between the steps
`and, accordingly, the dry etching treatment comprising a
`plurality of steps can be applied rapidly without lowering the
`throughput.
`After completing the two steps of etching as described
`above, when the sametreatmentis applied continuously and
`repeatedly in the identical processing device to a next
`specimen, the stage 12 is controlled to a setting temperature
`for the specimen in the initial step, the first step in this
`embodiment after the completion of the second step and
`taking out the specimen and before putting the next speci-
`men into the diffusion chamber. That is, while the specimen
`is set to a temperature of —30° C. in the second step in the
`first embodiment, the stage 12 is heated by a heater of an
`electrostatic chuck (not illustrated) and, further, the degree
`of cooling by the chiller 17 is adapted such that the stage is
`heated rapidly by a method of wholly opening the electronic
`control valve 22 of the by-pass pipeline 21 while wholly
`closing the electronic control valve 20 of the coolant pipe-
`line 15, thereby interrupting the supply of the gas coolant
`from the chiller 17 to the stage 12.
`Then,it is possible to shorten the time after the comple-
`tion of the etching treatment
`for one specimen to the
`initiation for the etching treatment for a next specimen.
`Particularly, if the temperature can be changedto a setting
`temperature for the specimen in the stage 12 about approxi-
`mately within a period of time till the new specimen is
`transported in the diffusion chamber 2,
`the dry etching
`treatment comprising a plurality of steps can be applied
`without lowering the throughput, that is, while ensuring a
`sufficient productivity.
`Then, a second embodiment of the dry etching method
`according to the present invention using an etching device 1
`shown in FIG. 4 will be explained with reference to FIGS.
`2A-2C.
`
`This method is an example of applying the method of the
`present invention to the fabrication of a contact hole by
`etching. That is, in this embodiment, an SiO, layer 41 of a
`specimen W in which a photoresist pattern 42 is formed on
`an SiO, layer 41 on a silicon substrate 40 is etched and
`fabricated into a pattern shape corresponding to the photo-
`
`wn
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`55
`
`60
`
`65
`
`8
`resist pattern 42 as shown in FIG. 2A.In this method, just
`etching is applied at a normal temperature as the first step
`(main etching) and then overetching is applied at a low
`temperature as the succeeding secondstep.
`Atfirst, just etching of the first step is applied under the
`following conditions and the SiO, layer 41 is removed by
`etching to a state of leaving a portion to form a thin film as
`shown in FIG. 2B.
`First Step (Just etching)
`Etching gas: CL,F,0, 50/10 SCCM
`Pressure: 5 mTorr
`Source power-1 (RF antenna 4): 2500W (13.56 Hz)
`Source power-2 (RF antenna 3,3): 2500W (13.56 Hz)
`Pulse: ON/OFF; 10 msec/30 msec
`RF bias: 500W
`Specimen temperature: —20° C.
`Also in this embodiment, the specimen temperature is
`controlled by the combineduseofa heater of an electrostatic
`chuck equipped in the stage 12 (notillustrated) and cooling
`by the chiller 17 in the same mannerasin the first embodi-
`ment and, particularly, the specimen temperature is finely
`controlled by cooling control by the control device 23
`described above.
`
`Then, for applying overetching of the second step suc-
`ceedingto the first step, discharging in the etching device 1
`is once interrupted and the gases remaining in the diffusion
`chamber 2 are exhausted from the exhaust port 13. Then, an
`etching gas used for the second step described later (gas
`identical with that
`in the first step is used also in this
`embodiment) is introduced into the diffusion chamber2, and
`the gas is stabilized to adjust the inside of the diffusion
`chamber2 to a constant pressure. Further, during a series of
`operations described above, that is, immediately after the
`completion of the etching of the first step, the electronic
`control valve 22 of the bypass pipeline 21 is wholly closed
`and the electronic control valve 20 of the coolant pipeline 15
`is wholly opened in the cooling system by the chiller 17, to
`supply the gas coolant at -140° C. from the chiller 17 to the
`stage 12 to rapidly cool the specimen W.
`Then, the temperature of the specimen W reaches —50° C.
`which is an etching temperature to be described later within
`a short period of time of about 30 sec by such rapid cooling,
`like that in the first embodiment. Accordingly, since a series
`of operations of exhausting remaining gases in the diffusion
`chamber 2 after the interruption of discharge and further
`introducing and stabilizing a fresh etching gas takes a longer
`time than that required for rapid cooling also in this second
`embodiment, the time required for the rapid cooling does not
`constitute a factor of delaying the time required for the
`etching of the specimen W.
`Successively, overetching of the second step at a low
`temperature (-50° C.) is applied under the following con-
`ditions by conducting discharging again, and a portion of the
`SiO,
`layer 41 remaining being exposed on the silicon
`substrate 40 is removed by etching to form a contact hole 43
`as shownin FIG. 2C.
`Second Step (Overetching)
`Etching gas: CL,F,0, 50/10 SCCM
`Pressure: 5 mTorr
`Source power-1 (RF antenna 4): 2500W (13.56 Hz)
`Source power-2 (RF antenna 3,3): 2500W (13.56 Hz)
`Pulse: ON/OFF; 10 msec/30 msec
`RFbias: 200W
`Specimen temperature: —50° C.
`Whenthe overetching is thus applied, since the etching is
`a treatment under cooling to a low temperature, radical
`reaction can be suppressed by the temperature lowering even
`
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`6,063,710
`
`10
`of the polysilicon layer 51 formed therein is greater than that
`of other positions, a stringer (etching residue) 53 not
`removed by etching is formed.
`The specimen temperature is controlled in this embodi-
`ment in the same mannerasthat in the secondstep ofthefirst
`and the second embodiment.
`Then, for applying overetching of the second step suc-
`ceeding to the first step,
`the control mechanism for the
`cooling means and the heater disposed to the stage 12 are
`controlled to rapidly heat the specimen W.
`Then, the temperature of the specimen W reaches 50° C.
`which is an etching temperature to be described later within
`a short period of time of about 50 sec. Accordingly, also in
`the third embodiment, the time required for the rapid heating
`does not form a factor for delaying the time required for the
`etching treatment of the specimen W.
`Successively, discharging is conducted again to apply
`overetching of the second step at a high temperature (50° C.)
`under the following conditions, and a stringer (etching
`residue) 53 formed at the step 50a of the SiO, layer 50 is
`removed as shown in FIG. 3C.
`Second Step 1 (Overetching)
`Etching gas: Cl, 100 SCCM
`Pressure: 10 mTorr
`
`9
`if the formed side wall protection film is thin, and
`accordingly,
`it
`is possible to withstand excessive radical
`attack and suppress the occurrence of undercut or notching
`even if the bias applied to the