`
`United States Patent
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`
`
`Chen et al.
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`[19]
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`[11] Patent Number:
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`[45] Date of Patent:
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`4,511,430
`
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`Apr. 16, 1985
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`
`[56]
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`References Cited
`
`
`
`U'S' PATENT DOCUMENTS
`3,940,506
`2/1976 Heinecke ............................ .. 427/38
`
`
`
`
`4/1982 Vogel et a1.
`...................... .. 156/643
`4,324,611
`
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`
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`4,344,816
`8/1982 Craighead et a1.
`............... .. 156/643
`OTHER PUBLICATIONS
`
`
`J. Electrochem. Soc.: Solid—State Science and Technol-
`
`
`
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`
`
`
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`
`
`
`
`
`
`ogy, vol. 128, No. 2, Feb. 1981, Planarization of Phos-
`
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`
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`
`
`
`
`phorus—Doped Silicon Dioxide by A. C. Adams and C.
`D. Capio, Pp. 423—429.
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`
`
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`Prima Examiner—William A. Powell
`
`
`
`
`W
`Attorney, Agent, or Firm—Joseph E. Kieninger
`
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`ABSTRACT
`[57]
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`.
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`>
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`A method of controlling the etch rate who of 5102/—
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`photoresist (PR) in a quartz planarization etch back
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`process involves etching with a gaseous mixture con-
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`taining CF4 and either CHF3 or CxFy with x>1 or 02.
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`The preferred SiOz/PR ratio of 12:01 is obtained by
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`either adding CHF3 to decrease the etch rate of the PR
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`or by adding 02 to increase the etch rate of the PR.
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`6 Claims, 2 Drawing Figures
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`[54] CONTROL OF ETCH RATE RATIO OF
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`SIOz/PHOTORESIST FOR QUARTZ
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`PLANARIZATION ETCH BACK PROCESS
`
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`[75]
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`Inventors: Lee Chen; Gangadhara s_ Mathad,
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`both of PoughkeepSIe, N.Y.
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`[73] Assignee:
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`International Business Machines
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`Corporation, Armonk, NY.
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`[
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`21 A 1. N .: 575 118
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`]
`pp
`0
`’
`.
`[22] Filed:
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`Jan. 30, 1984
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`Int. Cl.3 ...................... .. B44C 1/22; C03C 15/00;
`CO3C 25/06; B29C 17/08
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`[52] US. Cl. .................................. .. 156/643; 156/646;
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`156/657; 156/659.1; 156/668; 204/192 E;
`252/791
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`[58] Field of Search .......... .. 156/643, 646, 657, 659.1,
`156/668; 252/79.1; 204/192 E; 427/38, 39
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`[51]
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`12
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`12
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`'//////
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`-m-m-I I1.
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`Page 1 0”
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`TSMC Exhibit 1036
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`TSMC v. IP Bridge
`IPR2016-01246
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`Page 1 of 4
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`TSMC Exhibit 1036
`TSMC v. IP Bridge
`IPR2016-01246
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`

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`US. Patent ,
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`Apr. 16, 1985
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`4,51 1,430
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`V
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`12
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`FIG.‘|
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` 12
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`10
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`12
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`.WIIAV/IIAI
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`10
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`FIG.2
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`Page 2, 0f 4
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`4,511,430
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`2
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`1
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`CONTROL OF ETCH RATE RATIO OF
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`SIOz/PHOTORESIST FOR QUARTZ
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`PLANARIZATION ETCH BACK PROCESS
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`DESCRIPTION
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`1. Technical Field
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`This invention relates to a semiconductor etch back
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`process and more particularly to a method of control-
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`ling the etch rate ratio of SiOz/photoresist in a quartz
`planarization etch back process.
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`2. Background Art
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`In large scale integration (LSI) logic products metal-
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`lurgy structures are positioned on several
`levels. In
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`order to accurately interconnect these multilevel metal-
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`lurgy structures, it is necessary to planarize each metal-
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`lurgical structure level. As a result, obtaining a planar
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`topography in multilevel metallization structures is a
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`problem. One way to remove the topography in order
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`to planarize a particular metallization level, is by the
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`etch back process. The etch back process requires an
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`etch rate ratio of SiOz/photoresist to be Iii-0.1. The
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`present etching techniques prior to this invention have
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`not been able to achieve the desired etch back ratio at
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`high etch rates and with tight tolerances.
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`D. C. Vogel, et al, US. Pat. No. 4,324,611 describes
`an etching process for etching silicon dioxide and/or
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`silicon nitride using a primary etching gas of CF4 and a
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`secondary gas of CHF3. The chamber pressure is on the
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`order or 1 to 3 torr when the primary gas is added. The
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`addition of the secondary gas adds an additional 0.5 to
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`1.5 torr of pressure to the system. A third gas, such as
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`helium,
`is added at a pressure of the order of 5 torr,
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`when it is desired to prevent photoresist breakdown.
`This patent does not suggest a planarization process
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`involving organic polymeric materials such as photore-
`sist and silicon dioxide.
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`Other US. patents, R. A. Heinecke, U.S. Pat. No.
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`3,940,506 and H. G. Craighead et al, US. Pat. No.
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`4,344,816, suggest the use of combinations of CF4 and
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`CHF3 gases but again not for the same purpose and not
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`at the same pressures and composition in the gaseous
`reactive plasma.
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`SUMMARY OF THE INVENTION
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`It is a primary object of this invention to provide an
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`improved quartz planarization etch back process.
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`It is another object of this invention to provide a
`method of controlling the etch rate ratio of Si02/-
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`photoresist (PR).
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`These and other objects are accomplished by a
`method that involves etching with a gaseous mixture
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`containing CF4 and either CHF3 or CxFy with x>1 or
`02. The preferred SiOz/PR ratio of 1
`is obtained by
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`either adding CHF3 to decrease the etch rate of the PR
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`or by adding 02 to increase the etch rate of the PR. In
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`one preferred embodiment using a single wafer reactor
`to etch SiO2 covered with a commercial photoresist
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`(AZ) a gaseous mixture containing 97.5% CF4, 2.5%
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`CHF3 and 0% oxygen provided an etch rate ratio of
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`1.096 whereas a gaseous mixture containing 97.0% CF4,
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`3% CHF3 and 0% oxygen yields an etch rate ratio of
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`1.196.
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`Other objects of this invention will be apparent from
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`the following detailed description,
`reference being
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`made to the following drawings in which a specific
`embodiment of the invention is shown.
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`Page 3 of 4
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`BRIEF DESCRIPTION OF THE DRAWINGS
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`FIG. 1 is a cross-sectional view of the SiOz/photore-
`sist system to be etched in accordance with this inven-
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`tion;
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`FIG. 2 is a cross-sectional view showing the plana-
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`rized structure obtained in accordance with the etching
`process of this invention.
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`DESCRIPTION OF THE PREFERRED
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`EMBODIMENT
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`The method of controlling the etch rate ratio of Si-
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`Oz/photoresist in a quartz planar etch back process
`includes the step of etching with a gaseous mixture
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`containing CF4 and either CHF3 or CXFy with x>1 or
`02. As shown in FIG. 1, topographical features 10, for
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`example a metal such as copper, aluminum and the like,
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`are covered with a rough substrate such as $02 12A.
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`The purpose of this invention is to planarize the surface
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`of the SiOz 12 that it is substantially planar or flat be—
`tween the metal features 10 as shown in FIG. 2.
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`The structure shown in FIG. 2 is obtained with a
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`process in accordance with this invention that involves
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`etching a layer 14 of a photoresist material, i.e. an or-
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`ganic polymer material, which is positioned over the
`Si02 layer 12 as shown in FIG. 1. It is desired to etch
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`uniformly through the resist layer 14 and the SiOz layer
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`12A with an etch rate ratio of 1.2:0.1 such that metal
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`just sticks out of the $02 surface. The etch rate ratio is
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`defined as the etch rate of the oxide, $02, over the etch
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`rate of the photoresist. When a calculated etch rate ratio
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`of 1.21:0.1 is obtained, then a planar structure such as
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`shown in FIG. 2 is produced. Since the etch rate of
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`different photoresists varies significantly, it is difficult
`to find one set of conditions that is suitable for more
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`than one photoresist. In addition, the etch rates of the
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`$02 and photoresist vary significantly depending upon
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`the apparatus and equipment used.
`In accordance with this invention an etch rate ratio of
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`1.2i0.1 is obtained by etching the structure shown in
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`FIG. 1 with a gaseous mixture at a pressure of not less
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`than 500 microns of mercury containing CF4 and either
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`CHF3 or or CxFy with x> 1 or oxygen. The composition
`of the gaseous mixture depends upon the etching char-
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`acteristics of the photoresist material used in layer 14.
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`The composition of the gaseous mixture contains an
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`etching gas, a polymerizing gas and an oxidizing gas to
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`achieve a balance between surface etching, gas phase
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`polymerization and surface oxidation reactions. The
`CF4 gas is the primary gas for etching $02. The CHF3
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`or CxFy with x> 1 gas is primarily added to decrease the
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`etch rate of the photoresist. The CHF3 or CxFy with
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`X>1 gas is a polymerizing gas for the control of gas
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`phase polymerization. The CxFy with x> 1 gas is unsatu-
`rated. Examples of such a gas are C2F4 and C2F6. The
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`02 gas is used primarily to increase the etch rate of the
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`resist. The oxygen gas is for controlling surface oxida—
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`tion of the polymer that is deposited by the second gas
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`(CHF3). The combination of these three gases provides
`a wide latitude in achieving etch rate ratios so that the
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`planarization objectives can be easily met even with
`varying photoresist properties.
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`The following examples illustrate the effect of CHF3
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`and 02 on the etch rate ratio.
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`Page 3 of 4
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`

`

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`4,511,430
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`4
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`l. A method for uniformly etching a surface which
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`includes both silicon dioxide and an organic polymer
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`material comprising the steps of
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`contacting said surface with a reactive etching
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`plasma which contains CF4 and a gas taken from
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`the group consisting of CHF3 and CXFy with x>1
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`to cause the structure formed by said etching step
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`to be substantially planar and have an etch rate
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`ratio of 1.2:0.1.
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`2. A method as described in claim 1 whereby said
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`etching plasma contains CHF3.
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`3. A method as described in claim 2 whereby the
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`gaseous mixture contains 0.5 to 5.0% CHF3.
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`4. A method as described in claim 1 including the step
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`of evacuating said structure to a pressure of not less
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`than 500 microns of mercury.
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`5. A method as described in claim 1 whereby said
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`reactive etching plasma contains oxygen.
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`6. A method as described in claim 5 whereby the
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`reactive etching plasma contains 0.5 to 10 volume %
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`Oz.
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`*
`*
`*
`*
`*
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`3
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`EX-
`Estimated
`AM-
`
`PLE
`Over All
`%
`Planarity
`
`
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`
`
`
`CHF3 02
`ERR
`Satisfactory
`No.
`c1=4
`PR
`
`
`
`
`
`o AZI3SOJ
`0.860
`1
`100.0
`0
`No
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`0 AZ 1350]
`2
`99.0
`1
`0.989
`NO
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`
`0 AZI3SOJ
`3
`98.5
`1.5
`1.017
`NO
`
`
`
`
`
`Yes
`0 AZI350}
`97.5
`2.5
`4
`1.096
`
`
`
`
`
`Yes
`97.0
`0 AZI3SOJ
`5
`3
`1.196
`
`
`
`
`
`0 AZI3SOJ
`6
`95.0
`5
`1.570
`No
`
`
`
`
`
`NO'
`HC
`7
`100.0
`0
`0
`0.95
`
`
`
`
`
`
`25
`HC
`8
`so
`20
`0
`No
`
`
`
`
`
`
`
`1.7
`HC
`0
`70
`9
`30
`No
`
`
`
`
`
`
`
`Yes
`1.3
`HC
`0
`so
`10
`20
`
`
`
`
`
`
`
`
`BC
`90
`1.2
`Yes
`11
`10
`0
`
`
`
`
`
`
`0 10 HC 0.29012 No
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`5
`
`10
`
`
`
`15
`
`
`
`Although preferred embodiments have been de-
`
`
`
`
`
`
`
`
`
`
`
`scribed, it is understood that numerous variations may
`
`
`
`
`
`
`be made in accordance with the principles of this inven- 20
`
`
`
`
`
`
`tion.
`
`We claim:
`
`
`
`
`25
`
`
`30
`
`
`
`35
`
`
`
`40
`
`
`45
`
`
`
`50
`
`
`
`55
`
`
`60
`
`
`
`65
`
`
`Page 4 of 4
`
`Page 4 of 4
`
`