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`United States Patent 5
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`Chen et al.
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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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`3,940,506
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`4,324,611
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`4,344,816
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`[54]
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`CONTROL OF ETCH RATE RATIO OF
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`SIO2/PHOTORESIST FOR QUARTZ
`PLANARIZATION ETCH BACK PROCESS
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`[75]
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`Inventors:
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`Lee Chen; Gangadhara S. Mathad,
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`both of Poughkeepsie, N.Y.
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`[73]
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`Assignee:
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`International Business Machines
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`Corporation, Armonk, N.Y.
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`[21]
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`Appl. No.: 575,118
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`[22]
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`Filed:
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`Jan, 30, 1984
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`[51]
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`[52]
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`[58]
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`Int. C13 oeeeceesccesseeeees B44C 1/22; CO3C 15/00;
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`C03C 25/06; B29C 17/08
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`WLS. C1. ceceecccccseseeneneeeeesneees 156/643; 156/646;
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`156/657; 156/659.1; 156/668; 204/192 E;
`252/79.1
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`Field of Search............ 156/643, 646, 657, 659.1,
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`156/668; 252/79.1; 204/192 E; 427/38, 39
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`References Cited
`U.S. PATENT DOCUMENTS
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`2/1976 Heinecke osc eeenenes 427/38
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`4/1982 Vogel et al. woe 156/643
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`8/1982 Craighead et al. .......... 156/643
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`OTHER PUBLICATIONS
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`J. Electrochem. Soc.: Solid-State Science and Technol-
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`ogy, vol. 128, No. 2, Feb. 1981, Planarization of Phos-
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`phorus-Doped Silicon Dioxide by A. C. Adamsand C.
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`D. Capio, pp. 423-429.
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`Primary Examiner—William A. Powell
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`Attorney, Agent, or Firm—Joseph E. Kieninger
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`ABSTRACT
`[57]
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`A method of controlling the etch rate ratio of Si02/-
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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 CHF; or C,Fy with x>1 or Oo.
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`The preferred Si02/PR ratio of 1.2£0.1 is obtained by
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`either adding CHF; to decrease the etch rate of the PR
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`or by adding O2 to increase the etch rate of the PR.
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`6 Claims, 2 Drawing Figures
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`Page 1 of 4
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`TSMC Exhibit 1036
`TSMCv. 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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`U.S. Patent |
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`Apr. 16, 1985
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`4,511,430
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`Page 2of 4
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`Page 2 of 4
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`

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`CONTROL OF ETCH RATE RATIO OF
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`SIO2/PHOTORESIST FOR QUARTZ
`PLANARIZATION ETCH BACK PROCESS
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`BRIEF DESCRIPTION OF THE DRAWINGS
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`FIG. 1 is a cross-sectional view of the Si02/photore-
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`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-
`1. Technical Field
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`rized structure obtained in accordance with the etching
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`This invention relates to a semiconductor etch back
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`process of this invention.
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`process and moreparticularly to a method of control-
`DESCRIPTION OF THE PREFERRED
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`ling the etch rate ratio of SiO2/photoresist in a quartz
`EMBODIMENT
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`planarization etch back process.
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`2. Background Art
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`The method of controlling the etch rate ratio of Si-
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`In large scale integration (LSD) logic products metal-
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`O2/photoresist in a quartz planar etch back process
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`lurgy structures are positioned on several
`levels. In
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`includes the step of etching with a gaseous mixture
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`order to accurately interconnect these multilevel metal-
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`containing CF4 and either CHF3 or C,Fy with x>1 or
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`lurgy structures, it is necessary to planarize each metal-
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`O2. As shown in FIG.1, topographical features 10, for
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`lurgical structure level. As a result, obtaining a planar
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`example a metal such as copper, aluminum and thelike,
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`topography in multilevel metallization structures is a
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`are covered with a rough substrate such as SiO? 12A.
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`problem. One way to remove the topography in order
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`The purpose ofthis invention is to planarize the surface
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`to planarize a particular metallization level, is by the
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`of the SiOQ2 12 that it is substantially planar or flat be-
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`etch back process. The etch back process requires an
`tween the metal features 10 as shownin FIG. 2.
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`etch rate ratio of SiO2/photoresist to be 1.2£0.1. The
`The structure shown in FIG. 2 is obtained with a
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`present etching techniquesprior to this invention have
`not been able to achieve the desired etch back ratio at
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`process in accordancewith this invention that involves
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`etching a layer 14 of a photoresist material, i.e. an or-
`high etch rates and with tight tolerances.
`D. C. Vogel, et al, U.S. Pat. No. 4,324,611 describes
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`ganic polymer material, which is positioned over the
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`an etching process for etching silicon dioxide and/or
`SiO? layer 12 as shown in FIG.1. It is desired to etch
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`silicon nitride using a primary etching gas of CF, and a
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`uniformly through the resist layer 14 and the SiQ2 layer
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`12A with an etch rate ratio of 1.20.1 such that metal
`secondary gas of CHF3. The chamberpressure is on the
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`orderor | to 3 torr when the primary gas is added. The
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`just sticks out of the SiO2 surface. The etch rate ratio is
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`addition of the secondary gas adds an additional 0.5 to
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`defined as the etch rate of the oxide, SiO2, over the etch
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`1.5 torr of pressure to the system. A third gas, such as
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`rate of the photoresist. When a calculated etch rate ratio
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`helium,
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`of 1.2£0.1 is obtained, then a planar structure such as
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`whenit is desired to prevent photoresist breakdown.
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`shown in FIG. 2 is produced. Since the etch rate of
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`This patent does not suggest a planarization process
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`different photoresists varies significantly, it is difficult
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`involving organic polymeric materials such as photore-
`to find one set of conditions that is suitable for more
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`sist and silicon dioxide.
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`than one photoresist. In addition, the etch rates of the
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`Other U.S. patents, R. A. Heinecke, U.S. Pat. No.
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`SiO2 and photoresist vary significantly depending upon
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`3,940,506 and H. G. Craighead et al, U.S. Pat. No.
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`the apparatus and equipment used.
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`4,344,816, suggest the use of combinations of CF4 and
`In accordancewith this invention an etchrate ratio of
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`CHF;gases but again not for the same purpose and not
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`1.2+0.1 is obtained by etching the structure shownin
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`at the same pressures and composition in the gaseous
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`FIG.1 with a gaseous mixture at a pressure of notless
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`reactive plasma.
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`than 500 microns of mercury containing CF, andeither
`SUMMARYOF THE INVENTION
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`CHF;or or C,Fy with x> 1 or oxygen. The composition
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`of the gaseous mixture depends upon the etching char-
`It is a primary object of this invention to provide an
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`improved quartz planarization etch back process.
`acteristics of the photoresist material used in layer 14.
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`It is another object of this invention to provide a
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`The composition of the gaseous mixture contains an
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`method of controlling the etch rate ratio of SiO2/-
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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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`These and other objects are accomplished by a
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`polymerization and surface oxidation reactions. The
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`method that involves etching with a gaseous mixture
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`CF,gasis the primary gas for etching SiO2. The CHF3
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`containing CF4 and either CHF3 or C,Fy with x>1 or
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`or CxF, with x> 1 gas is primarily added to decrease the
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`O2. The preferred SiO2/PR ratio of 1
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`etch rate of the photoresist. The CHF3 or CxFy with
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`either adding CHF3 to decrease the etch rate of the PR
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`X>1 gas is a polymerizing gas for the control of gas
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`or by adding O2 to increase the etch rate of the PR. In
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`phase polymerization. The C,F, with x> 1 gas is unsatu-
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`one preferred embodiment using a single wafer reactor
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`rated. Examples of such a gas are C2F4 and C2F¢. The
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`to etch SiO2 covered with a commercial photoresist
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`Oz gas is used primarily to increase the etch rate of the
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`(AZ) a gaseous mixture containing 97.5% CF4, 2.5%
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`resist. The oxygen gasis for controlling surface oxida-
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`CHF;3and 0% oxygen provided an etch rate ratio of
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`tion of the polymer that is deposited by the second gas
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`1.096 whereas a gaseous mixture containing 97.0% CF4,
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`(CHF3). The combination of these three gases provides
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`3% CHF3 and 0% oxygen yields an etch rate ratio of
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`1.196.
`a wide latitude in achieving etch rate ratios so that the
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`planarization objectives can be easily met even with
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`Other objects of this invention will be apparent from
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`varying photoresist properties.
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`the following detailed description,
`reference being
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`The following examplesillustrate the effect of CHF3
`made to the following drawings in which a specific
`embodiment of the invention is shown.
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`and Q2on the etch rate ratio.
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`1
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`4,511,430
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`DESCRIPTION
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`4
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`1. 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 CF, and a gas taken from
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`the group consisting of CHF3 and C,Fy with x>1
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`to cause the structure formed bysaid etching step
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`to be substantially planar and have an etch rate
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`ratio of 1.20.1.
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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 methodas 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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`O2.
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`*
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`4,511,430
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`3
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`EX-
`Estimated
`AM-
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`Over All
`Planarity
`%
`PLE
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`ERR
`CF,
`Satisfactory
`PR
`CHF3 O2
`No.
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`0.860
`100.0
`No
`1
`0
`0 AZ1350J
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`0.989
`99.0
`No
`2
`0 AZ13505
`1
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`
`
`
`
`1.017
`98.5
`No
`1.5
`0 AZ13505
`3
`
`
`
`
`
`
`1.096
`97.5
`2.5
`Yes
`0 AZ13503
`4
`
`
`
`
`
`
`1.196
`97.0
`Yes
`0 AZ13503
`5
`3
`
`
`
`
`
`
`1.570
`95.0
`0 AZ13505
`6
`5
`No
`
`
`
`
`
`
`0.95
`100.0
`No:
`HC
`7
`0
`0
`
`
`
`
`
`
`
`80
`2.5
`0
`HC
`8
`20
`No
`
`
`
`
`
`
`
`70
`1.7
`HC
`0
`9
`30
`No
`
`
`
`
`
`
`
`20
`80
`10
`Yes
`HC
`0
`1.3
`
`
`
`
`
`
`
`1.2
`90
`Yes
`HC
`il
`10
`0
`
`
`
`
`
`
`
`90 0 10 HC 0.812 No
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`Although preferred embodiments have been de-
`
`
`
`
`
`
`scribed, it is understood that numerousvariations may
`
`
`
`
`
`
`
`
`
`
`be madein accordance with the principles of this inven-
`
`
`
`tion,
`
`Weclaim:
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`Page 4 of 4
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`Page 4 of 4
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`