United States Patent
`
`[19]
`
`5,226,056
`Kikuchi et al.
`Jul. 6, 1993
`[45] Date of Patent:
`
`IlllllllllllllllllllllIllllllllllllllHilllllllllllllllllllllllllllllllllll
`US005226056A
`
`[11] Patent Number:
`
`[54] PLASMA ASHING METHOD AND
`APPARATUS THEREFOR
`
`[56]
`
`References Cited
`U.S. PATENT DOCUMENTS
`
`[75]
`
`Inventors: Masashi Kikuchi, Fujisawa;
`Toshinari Takata, Chigasaki; Tokuo
`Watanabe, Yokosuka, all of Japan
`
`[73] Assignee:
`
`Nihon Shinku Gijutsu Kabushiki
`Kaisha, Chigasaki, Japan
`
`[21] App]. No.: 462,380
`
`[22] Filed:
`
`Jan. 9, 1990
`
`_
`‘Foreign Application Priority Data
`[30]
`Jan. 10, 1989 [JP]
`Japan ...................................... 1-2042
`Jan. 10, 1989 [JP]
`Japan . .. . .
`. . . . .. 1-2043
`
`.. . . .. 1-2044
`Jan. 10, 1989 [JP]
`Japan . . . ..
`Japan .................................... .. 1-2045
`Jan. 10, 1989 [JP]
`
`Int. Cl.5 ............................................. .. H04B 7/00
`[51]
`[52] U.S. Cl. ...................................... .. 373/18; 373/62;
`156/345; 156/643; 156/646; 204/164;
`204/192.1; 219/121.11; 219/121.36;
`219/121.37; 219/121.4; 219/390
`[58] Field of Search ............. .. 156/643, 646, 668, 345;
`204/192 E, 164, 298; 373/40, 18, 22, 62;
`219/10.55 E, 10.55 M, 10.67, 121.43, 390,
`121.11,121.36,121.37,12l.4, 121.41, 383
`
`7/1985 Fujiyama et al.
`.
`-
`.... .. 156/643
`4,529,474
`
`. . . . .. 219/390
`8/1985 Shimizu . . .. .. .. .
`4,533,820
`.... .. 156/643
`4.96l,8l2 10/1990 Baerg et al.
`
`.... .. 156/643
`4,983,254
`1/1991 Fujimura et al
`7/1991 Sato ................................... .. 156/643
`5,034,086
`
`Primanz Examiner—Bruce A. Reynolds
`Assistant Examiner—-Tu Hoang
`Attorney, Agent, or Firm-—Armstrong & Kubovcik
`
`[57]
`
`ABSTRACT
`
`In a method for plasma ashing a resist film coated on a
`substrate, the temperature of the substrate is controlled
`initially at temperatures below that at which explosion
`of the resist film occurs until a surface portion of a resist
`film has been removed. Thereafter, the substrate tem-
`perature is increased to remove the remaining portions
`of the resist film. An apparatus for conducting the
`method includes a plurality of supports, which may be
`movably disposed within a vacuum treatment chamber
`for moving the substrate away from a source of heat and
`for moving the substrate into contact with the heating
`source.
`
`8 Claims, 10 Drawing Sheets
`
`
`
`Intel Corp. et al. Exhibit 1004
`
`Intel Corp. et al. Exhibit 1004
`
`

`
`U.S. Patent
`
`July 6, 1993
`
`Sheet 1 of 10
`
`5,226,056
`
`F|G,|
`
`PRIOR ART
`
`
`
`F l G.2
`
`PRIOR ART
`
`L.
`
`
`
`
`57.2
`-1-1
`
`
`2b
`
` 200°C
`
`l.|.l
`
`...5.5
`'2 <
`1: E
`|-- I41
`co 0-
`2 E
`en 9-
`
`— — -— -. - -—~
`
`
`200‘C
`
`In
`
`.. g
`E <
`Q5 0:
`l-- N
`en 0-
`*3 5.
`en I-
`
`TIME
`
`.
`
`TIME
`
`PRIOR ART
`
`PRIOR ART
`
`Intel Corp. et al. Exhibit 1004
`
`Intel Corp. et al. Exhibit 1004
`
`

`
`U.S. Patent
`
`July 6, 1993
`
`Sheet 2 of 10
`
`5,226,056
`
`was
`
`PRIOR ART
`
`n\
`
`“O
`
`In}
`
`5'
`
`I:
`
`I0
`
`I b
`
`I
`
`Ii.'o?;§T
`
` .
`
`I-'|G.7
`
`PRIOR ART
`
`'4
`
`3
`
`so
`
`V[d5")'}’I’a".i
`_,
`I I
`‘ I
`
`I
`
`(pm/min)
`
`2
`
`'
`
`\\ \ Q
`I
`
`I.I.|
`Ia
`% I
`? '3
`E
`lb
`I
`% o
`"
`"
`<
`
`F I G 9
`
`PRIOR ART
`
`-
`
`I
`:
`I
`'
`I
`.
`'
`,
`'
`'
`
`9
`-75
`.75
`mm
`
`I
`CENTER OF SUBSTRATE
`
`F I G
`PRIOR ART
`
`Intel Corp. et al. Exhibit 1004
`
`Intel Corp. et al. Exhibit 1004
`
`

`
`U.S. Patent
`
`July 6, 1993
`
`Sheet 3 of 10
`
`5,226,056
`
`
`
`
`F'''''"'
`2.4-7-—n\‘ \‘1:\' \i:r:‘
`
`200'C
`
`Lu
`g
`‘+1’:
`<
`1%
`|-
`u>0-
`(1.12
`::Lu
`U)|-
`
`200°C
`
`3un-
`
`3:‘
`EB
`<4
`mm
`IL!
`"0.
`mg
`‘nu,
`
`TIME
`
`Intel Corp. et al. Exhibit 1004
`
`Intel Corp. et al. Exhibit 1004
`
`

`
`U.S. Patent
`
`July 6, 1993
`
`Sheet 4 of 10
`
`5,226,056
`
`Intel Corp. et al. Exhibit 1004
`
`Intel Corp. et al. Exhibit 1004
`
`

`
`U.S. Patent
`
`July 6, 1993
`
`Sheet 5 of 10
`
`5,226,056
`
`Intel Corp. et al. Exhibit 1004
`
`Intel Corp. et al. Exhibit 1004
`
`

`
`U.S. Patent
`
`July 6, 1993
`
`Sheet 6 of 10
`
`5,226,056
`
`F%|G.2|
`
`1
`
`'-II|rifl1—-_‘-|.l1|llll!lll!!|
`
`I-I.-II _
`
`-
`
`7_
`
`-
`
`.
`
`Intel Corp. et al. Exhibit 1004
`
`Intel Corp. et al. Exhibit 1004
`
`

`
`> U.S. Patent
`
`July 6, 1993
`
`Sheet 7 of 10
`
`5,226,056
`
`F|G.24
`
`N C
`
`‘!
`
`9 u
`
`.
`
`Intel Corp. et al. Exhibit 1004
`
`Intel Corp. et al. Exhibit 1004
`
`

`
`U.S. Patent
`
`July 6, 1993
`
`Sheet 8 of 10
`
`5,226,056
`
`
`
`230(23b)
`
`
`
`
`
`V‘
`
`y.
`
`, :.
`,
`500
`
`E-§\l.\\\\§§/2'
`
`
`
`
`.
`
`
`
`__._.__..___________.___-.__.-_--_.i N2nu‘-!'g1‘ .
`‘
`gop:¢q2:~——v—-
`
`'IIA
`
`;
`
`I
`
`E
`
`r
`
`I
`
`______
`53k€\\\\"9
`
`4_¢—.—.____.._.
`
`?/5
`
`~\:a
`
`
`EE-E‘..2‘.
`I 2»
`
`
`"‘ ‘ ’\\\\\\\\\\'- -
`{'11.-jvl!
`
`4-wa--—.-—..—.__—_.J
`
`Intel Corp. et al. Exhibit 1004
`
`
`
`Intel Corp. et al. Exhibit 1004
`
`

`
`U.S. Patent
`
`July 6, 1993
`
`Sheet 9 of 10
`
`5,226,056
`
`
`
`--..._mH|:.l.ml.H
`
`...“‘CL«“\\..mI’D
`
`
`
`W/./¢Vu2.,»
`
`.....m
`
`M
`
`..NW0_mmm./\s#.r|..w.‘~“N.._II.._I.I\\.
`...ale.Ihlu
`
`
`
`........——Ll$WI--______._—_,
`
`
`
`.9...3.
`
`
`
`can.WrI.4_a
`
`cm
`
`can
`
`Intel Corp. et al. Exhibit 1004
`
`Intel Corp. et al. Exhibit 1004
`
`
`
`
`
`

`
`U.S. Patent
`
`July 6, 1993
`
`Sheet 10 of 10
`
`5,226,056
`
`F|G.28
`
`4
`
`/Ill
`_
`I \ I I I I‘. 5
`qr
`
`
`
`3.3warns.7-can - -
`
`I
`
`01Nl
`
`%g»3 I I
`
`
`1‘
`
`2'.‘x(i\‘ -.\\\\‘. m\\"s" 1I.\
`S’/‘VIII; VIIIIJE 'Ilfi€§iE‘
`§ 5 llfilifl‘hr -IIINI
`
`9 =.\\‘7n7llIIII4_nv4 i E
`
`5}’-‘ii’ _
`
`9
`
`
`
`
`
`
`
`.\\\
`
`—
`
`
`
`‘;
`
`7AI""IIlI.;_I_+;|:§l
`ET-;T_
`IIIIIII |ll'lIIll!IlIII.-_--_-;-
`
`
`
`
`
`
` E 5a
`
`
`
`
`Ina!
`- - 1.155;I VJZJJJJ4E ‘@114 _ — »
`
`(Ila llllll 7Il£i';!
`
`(Br//1
`I913’
`
`§A\\V
`. %,
`EEEEI
`
`@.m\1,~,uN
`V a‘
`
`$4
`
`
`
`
`
`I
`
`D.
`
`
`
`”
`
`‘
`
`nu ‘
`
`‘
`\
`
`
`
`,7’
`
`__
`
`
`
`
`L..- 3,1 39°
`
`
`7AD'|ITII.IAj-;j|jE—j£
`-¥T'—'i’—‘
`IllllllmInlgrglnnn-5--Er
`
`
`
`
`39.,
`
`F|G.29
`
`Intel Corp. et al. Exhibit 1004
`
`Intel Corp. et al. Exhibit 1004
`
`

`
`1
`
`5,226,056
`
`PLASMA AS]-IING METHOD AND APPARATUS
`THEREFOR
`
`DETAILED DESCRIPTION OF THE
`INVENTION
`
`1. Field of the Invention
`
`5
`
`10
`
`15
`
`20
`
`2
`- 10 seconds as shown by the curve B in FIG. 4. The hot
`plate 7 is maintained at a constant temperature by means
`of a thermocouple-type thermometer 10.
`Another example of the conventional dry treatment
`apparatus is shown in FIG. 7.
`In the arrangement
`shown in FIG. 7 a vacuum exhaust port 3 is provided
`directly under a substrate 1. In this construction, just
`like in the above-described example, the substrate 1 is
`placed on a hot plate 7; oxygen radicals or radicals of a
`reactive gas are generated by discharging of a micro-
`wave discharging member 2a connected to a micro-
`wave power source 13, to generate radicals of oxygen
`gas or the reactive gas obtained by mixing oxygen gas
`with a small quantity of CF4, N2, and H2. The gas is
`introduced from a reactive gas source 2b connected to
`an introduction port 2; the radicals react with a resist
`film on the heated substrate 1, and then the resist film is
`decomposed and evacuated and discharged by a vac-
`uum pump 14 via the vacuum exhaust port 3.
`As circuits become finer, it has become frequent prac-
`tice to utilize a resist film coated on a substrate 1 as a
`mask for locally doping impurities, by ionization, on the
`surface of the substrate 1. In this case, as shown in FIG.
`5, the surface layer portion 11a of resist film 11, utilized
`as a mask, is affected and hardened b.y.ion beams, and
`stresses are concentrated inside the surface layer. It is
`difficult to remove the resist film 11 by ashing in the
`above-described dry treatment method and if an at-
`tempt is made to remove the resist film 11 the surface
`layer 11a of resist film 11 may explode due to sudden
`thermal stresses. The flakes of the resist film 11 gener-
`ated by the explosion would remain on the substrate 1
`or inside the vacuum treatment chamber 4 as dust parti-
`cles or residual matter and become an obstacle to the
`
`This invention relates to a method and an apparatus
`for removing a resist film coated on a semiconductor
`substrate by ashing utilizing plasma.
`2. Background of the Invention
`In order to fabricate minute integrated circuits, a
`resist film having a circuit pattern is placed on the sur-
`face of a semiconductor substrate. The substrate is then
`etched, using the resist film as a template and then the
`resist film is removed.
`Methods of removing the resist film can be divided
`into two groups (i.e., a wet treatment method in which
`chemicals such as hydrogen peroxide, organic solvents,
`and the like are used and a dry treatment method in
`whichthe resist film is ashed by an oxygen plasma).
`Many of the chemicals used in the wet treatment
`method are harmful to humans and it is necessary to
`monitor the safety precautions used and the amount of
`pollution caused by waste liquids. Further, the cherni- 25
`cals used contain impurities which will cause voids in
`and contamination of the patterns of semiconductor
`circuits. Such chemicals are therefore not suitable to the
`fabrication, on a very large—scale, of integrated circuits.
`In the dry treatment method, a resist film of CXH yNz
`coated on the substrate is caused to react with oxygen
`radicals generated in an oxygen plasma so as to remove
`the resist film by decomposing and evaporating the film
`into CO2, N02 and H20. This method does not generate
`substances which are harmful to the human body and
`does not contain impurities, and it
`is suitable to the
`hyperfine fabrication of integrated circuits.
`A specific example of the conventional dry treatment
`method is shown in FIGS. 1 and 2. A substrate 1 coated
`with a resist film is placed either above or on heating
`means 51 inside a vacuum treatment chamber 4. The
`heating means may be an infrared lamp 5 as shown in
`FIG. 1 or a hot plate 7 provided with a thermally con-
`trolled cast-in heater 6 as shown in FIG. 2. The vacuum
`treatment chamber 4 contains a reactive gas introduc-
`tion port 2 and a vacuum exhaust port 3. Oxygen gas or
`a reactive gas obtained by mixing oxygen gas with a
`small quantity of CF4, N2 or H; to be introduced from
`the reactive gas introduction port 2 is converted to
`plasma by a plasma applicator 50 comprising a micro-
`wave discharging member 2a. The oxygen radicals or
`the radicals of the reactive gas are caused to react with
`the resist film on, the heated substrate 1. The resist film
`decomposes and evaporates and then is discharged from
`vacuum treatment chamber 4 by a vacuum pump.
`In the example shown in FIG. 1, the substrate I,
`placed on a rack 8 inside the vacuum treatment chamber
`4, is heated by the infrared lamps 5 to a predetermined
`temperature in about 5 seconds as shown by the curve
`A in FIG. 3. The temperature of the substrate 1 is con-
`trolled by an infrared thermometer 9 which detects the
`infrared rays emitted from the surface of the substrate 1.
`The output signal of the thermometer 9 is fed back to
`the power source of the lamp 5 to maintain the tempera-
`ture constant by controlling the electric power.
`In the example shown in FIG. 2, the substrate 1 is
`supplied with heat by thermal contact with the hot plate
`7, and is heated to a predetermined temperature in about
`
`30
`
`35
`
`45
`
`50
`
`55
`
`65
`
`hyperfine fabrication of the substrate 1.
`According to findings of the inventors, the lower
`limit of temperature of explosion of the resist film 11
`varies with the conditions of ion doping and the type of
`resist, but it has been found that by lowering substrate
`temperatures in the range of about 70° to 160° C. the
`surface layer portions of the resist film lla are removed
`during plasma ashing without causing the resist film to
`explode. The inventors have also observed that the
`wider the resist film 11, the more likely an explosion
`will occur.
`
`The apparatus shown in FIGS. 1, 2 and 7 is called a
`downstream-type ashing apparatus because the radicals
`of the reactive gas are generated outside the vacuum
`treatment chamber and flow from an upper portion
`along the surface of the substrate together with the
`reactive gas, and are discharged from the vacuum ex-
`haust port in a lower portion of the vacuum treatment
`chamber. This apparatus is advantageous in that the
`electrically charged particles do not strike the substrate
`and therefore the circuit pattern formed on the substrate
`is not damaged. However, as can be seen in FIGS. 8 &
`9, it is difficult to coat the resist film 11 only on the front
`surface 1a of the substrate, which is a requirement of a
`hyperfine circuit, as the film is often deposited on the
`rear surface lb of the substrate 1. There is a disadvan-
`
`tage in that if the substrate 1 is heated in contact with
`the hot plate 7, to remove the resist film 11 by ashing,
`the reactive radicals are prevented by the hot plate 7
`from working on that resist film 11 which is present on
`the rear surface lb, and the resist film 11 partly remains
`as shown in FIG. 9. If the resist film 11 which remains
`
`on the rear surface lb of the substrate 1 is peeled off in
`
`Intel Corp. et al. Exhibit 1004
`
`Intel Corp. et al. Exhibit 1004
`
`

`
`5,226,056
`
`3
`the following processes of fabrication, it will contami-
`nate the semiconductor manufacturing apparatus which
`should remain clean. Poor quality integrated circuits
`through adhesion of the peeled particles on the hyper-
`fine circuits are also produced
`Furthermore, in the apparatus as shown in FIGS. 1, 2
`and 7, the downward stream of the reactive gas flows
`along the surface of the substrate 1, from one side
`towards the other side, to ash the resist film 11. As can
`be seen from the ashing speed distribution shown by the
`curve A of FIG. 10, the ashing speed of the resist film
`on the upstream side of the reactive gas flow is consid-
`erably slower than that on the downstream side. There
`is, therefore, a disadvantage in that it takes a long time
`to complete the ashing process.
`A first object of this invention is to provide a method
`in which a resist film can be removed by ashing without
`an accompanying explosion of the resist.
`A second object of this invention is to provide an
`apparatus in which a resist film can be removed from
`not only the front surface but also the rear surface of the
`substrate.
`
`Another object of this invention is to provide an
`apparatus in which a resist film whose surface layer has
`been affected and hardened can be removed by ashing,
`and to remove the resist film by ashing without damag-
`ing the substrate.
`A still further object of this invention is to provide an
`apparatus in which the time required for finishing the
`ashing is shortened by making the ashing speed uniform.
`BRIEF SUMMARY OF THE INVENTION
`
`In this invention, as a method of attaining the above-
`described first object, there is provided a method which
`comprises the steps of:
`providing inside a vacuum treatment chamber a sub-
`strate coated with a resist film;
`ashing the resist film with an oxygen plasma while
`heating the substrate to remove the resist film;
`controlling the temperature of the substrate at a low
`temperature until the surface layer of the resist film has
`been removed; and
`increasing the temperature thereafter to a high tem-
`perature to remove remaining resist film.
`In order to solve the second object as described
`above,
`there is proposed a plasma ashing apparatus
`which comprises:
`a vacuum treatment chamber for receiving a substrate
`coated with a resist film, the vacuum treatment chamber
`having a vacuum exhaust port, heating means for heat-
`ing the substrate, and an inlet port for a reactive gas, the
`inlet port being provided with a plasma applicator to
`thereby remove the resist film on said substrate by ash-
`ing with radicals of a reactive gas to be introduced from
`the inlet port,
`wherein a plurality of pins are provided inside the
`vacuum treatment chamber to support the substrate at a
`distance from the heating means by supporting the rear
`surface of the substrate.
`In the proposed apparatus, it is preferable to dispose
`the plurality of pins movably between an advanced
`position and a retracted position, the advanced position
`being such that a distance is formed between the rear
`surface of the substrate and the heating means, and the
`retracted position being such that the rear surface of the
`substrate contacts the heating means.
`Further, as a plasma ashing apparatus capable of
`removing a resist film which has been affected and
`
`4
`hardened on its surface layer, and capable of removing
`the resist film by ashing without damaging the substrate,
`there is proposed a plasma ashing apparatus which in-
`corporates a vacuum treatment chamber for receiving a
`substrate coated with a resist film, the vacuum treat-
`ment chamber having a vacuum exhaust port, heating
`means for heating the substrate, and a reactive gas intro-
`duction port provided with a plasma applicator to
`thereby remove the resist film on the substrate by ash-
`ing;
`wherein a front electrode is disposed in front of the
`substrate in an opposed relationship thereto at a distance
`capable of generating plasma;
`a rear electrode is disposed on the rear side of the
`substrate in an opposed relationship thereto at a narrow
`distance incapable of generating plasma; and
`each of the electrodes is selectively connected to a
`high-frequency power source and ground respectively.
`In this embodiment it is preferable that the front elec-
`trode, which is disposed in an opposed relationship to
`the substrate, be comprised of a planer plate having a
`multitude of perforations.
`An object of shortening the time required for com-
`pleting the ashing by making the ashing speed, uniform,
`can be attained by a plasma ashing apparatus which
`includes:
`a vacuum treatment chamber for receiving a substrate
`coated with a photoresist film on a surface thereof, the
`vacuum treatment chamber having therein heating
`means to heat the substrate,
`a reactive gas introduction pipe for flowing a reactive
`gas to the vacuum treatment chamber and having in an
`intermediate portion thereof a plasma applicator to
`generate a plasma of the reactive gas,
`a vacuum exhaust pipe connected to a vacuum pump,
`the introduction pipe and the vacuum exhaust pipe
`being connected to the vacuum treatment chamber,
`whereby the reactive gas to be introduced from the
`reactive gas introduction pipe in an ionized condition is
`caused to flow along the surface of the substrate to ash‘
`the resist film on the surface thereof;
`wherein the inside of the vacuum treatment chamber
`is divided into two chambers by a shower plate, the
`shower plate having a perforated plate provided along
`the surface of the substrate;
`the vacuum exhaust pipe is connected to that side of
`the two chambers in which the substrate is located; and
`the reactive gas introduction pipe is connected to the
`other side of the two chambers.
`In this case, it is preferable that the shower plate be
`provided with small holes on the entire,, surface
`thereof, and a hole of relatively large diameter be
`formed in a position facing the central portion of the
`surface of the substrate. A vacuum exhaust pipe is con-
`nected to the vacuum treatment chamber such that it
`opens into a position facing the rear surface of the sub-
`strate, and a thermometer is provided to measure the
`temperature of the surface of the substrate through the
`relatively large diameter hole of the shower plate.
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`10
`
`l5
`
`20
`
`25
`
`30
`
`35
`
`45
`
`50
`
`55
`
`FIGS. 1 and 2 are sectional side views showing a
`conventional ashing method.
`FIG. 3 is a diagram showing the temperature changes
`of the substrate shown in FIG. 1.
`
`65
`
`FIG. 4 is a diagram showing temperature changes of
`the substrate shown in FIG. 2.
`
`FIG. 5 is an enlarged sectional view of a resist film.
`
`Intel Corp. et al. Exhibit 1004
`
`Intel Corp. et al. Exhibit 1004
`
`

`
`5
`FIG. 6 is also an enlarged sectional view of a resist,
`the surface thereof being heated to temperatures caus-
`ing the upper portion thereof to explode.
`FIG. 7 is a sectional side view of a conventional
`ashing apparatus.
`'
`FIG. 8 is a sectional view of a substrate coated with
`a resist film.
`FIG. 9 is a sectional view of a conventional substrate
`which has been treated by ashing showing remnants of
`the resist film.
`FIG. 10 is a diagram showing the distribution of the
`ashing speed of the apparatus shown in FIG. 2.
`FIG. 11 is a sectional side view showing one embodi-
`ment of the method of this invention.
`FIGS. 12 and 13 are diagrams showing the tempera-
`ture changes of the substrate in the embodiments of the
`present invention.
`_
`FIGS. 14 through 16 and FIG. 19 are sectional side
`views of embodiments of this invention.
`FIG. 17 is a plane disk-shaped front electrode having
`a multitude of perforations.
`FIG. 18 is a perspective view showing the support for
`the substrate in the embodiment of FIG. 16.
`FIGS. 20 through 29 are further concrete embodi-
`ments of this invention wherein:
`FIG. 20 is a front view with part of the apparatus cut
`away;
`.
`FIG. 21 a sectional side view taken along the line
`XXII—XXIl of FIG. 21;
`FIG. 22 is a sectional plan view taken along the line
`XXIII—XXIIl of FIG. 20;
`FIG. 23 is a perspective view of a cassette case;
`FIG. 24 is an enlarged view of a transfer apparatus;
`FIG. 25 is an enlarged sectional side view of a plasma
`applicator;
`FIG. 26 is a right-hand side view of FIG. 25; and
`FIGS. 27 through 29 are enlarged sectional side
`views of a vacuum treatment chamber.
`
`10
`
`I5
`
`20
`
`25
`
`30
`
`35
`
`DETAILED DESCRIPTION OF THE
`INVENTION
`
`In order to remove a resist film coated on the surface
`of a substrate the, is placed inside a vacuum treatment
`chamber and oxygen plasma is introduced into the
`chamber while heating the substrate to ash the resist
`film. In this case the generation of flakes by explosion of
`the resist film can be prevented by maintaining the sub-
`strate temperature initially at temperatures lower than
`conventionally used at the beginning of the ashing pro-
`cess, and then raising the temperature. In the first low-
`temperature condition, the surface layer of the resist
`film which has been affected and hardened by radiation
`of the ion beams is removed without generating sudden
`thermal stresses (i.e., without exploding the resist film).
`Then the inner portion of the resist film is rapidly
`heated to a high temperature and ashed at a high speed.
`The ashing of the resist film is performed by introduc-
`ing a reactive gas in which radicals are generated
`through electric discharging with a plasma applicator,
`from the reactive gas introduction port into the vacuum
`treatment chamber, causing the radicals of the reactive
`gas to chemically react with the resist film of the sub-
`strate, and thus decomposing and evaporating it and
`removing it via the exhaust port. If the rear surface of
`the substrate is in contact with a heating means the resist
`film adhered to the rear surface thereof is not ashed. But
`by holding the substrate with a plurality of pins at a
`distance away from the heating means the radicals of
`
`45
`
`50
`
`55
`
`65
`
`5,226,056
`
`6
`the reactive gas can enter the space defined by the dis-
`tance to thereby ash the resist film on the rear surface of
`the substrate.
`
`When the surface portion of the resist film coated on
`the surface of the substrate is affected and hardened
`through radiation by ion beams, the substrate is placed
`inside the vacuum treatment chamber. The reactive gas
`is caused to flow from the reactive gas introduction port
`towards the exhaust port. A rear electrode which faces
`the rear surface of the substrate is connected to a high-
`frequency power source, and a front electrode which is
`disposed in front of the substrate is grounded. Since the
`distance between the substrate and the rear electrode is
`set at a distance too narrow for plasma to be generated,
`the substrate becomes substantially equal
`in electric
`potential to that of the rear electrode, and since it be-
`comes negative in electric potential by the addition of
`high-frequency electric potential from the high-fre-
`quency power source, -plasma discharging starts be-
`tween the substrate and the front electrode which is
`grounded. The ions in the plasma are moved by the
`aitraction of the electric potential of the substrate and
`strike the front surface of the substrate. The resist film
`coated on the surface of the substrate is sputtered by the
`striking ions, and the surface layer portion which has
`been affected and hardened can be physically peeled off
`and removed.
`After the removal of the affected and hardened sur-
`face layer portion is completed, the substrate is heated
`by the heating means and the connection to the rear
`electrode is changed from the high-frequency power
`source to the ground, and the plasma applicator means
`is operated. Then, the reactive gas to be introduced
`from the introduction port to the vacuum treatment
`chamber is exited by the plasma and the generated radi-
`cals of the ‘reactive gas are caused to chemically react
`with the resist film which remains on the substrate. The
`remaining resist film is ashed and is rapidly removed
`from the surface of the substrate. The decomposed and
`evaporated compositions are removed via the exhaust
`port.
`In case damage to the surface of the substrate is
`feared, the high-frequency power source is connected
`to the front electrode and the rear electrode is
`grounded. In this case, since the front electrode be-
`comes negative in electric potential and the substrate is
`grounded, the ions of plasma to be generated therebe-
`tween gently strike the surface of the substrate and do
`not damage it, and the resist film on the substrate is
`gently sputtered. When the affected and hardened sur-
`face portion of the resist film has been peeled off by
`sputtering, the substrate is heated by the heating means.
`The connection to the front electrode is changed from
`the high-frequency power source to ground, and the
`plasma applicator is operated to rapidly remove the
`remaining resist film by ashing with the radicals in the
`reactive gas which is introduced into the vacuum treat-
`ment chamber.
`The radicals of the reactive gas flow towards the
`front side of the substrate through the perforations in
`the front electrode, thereby uniformly ashing the entire
`resist film.
`The narrow distance between the rear electrode and
`the rear surface of the substrate is set, for example, to 1
`mm at which no plasma is generated.
`In another embodiment the inside of the vacuum
`treatment chamber is divided into two chambers by a
`shower plate. The shower plate comprises a perforated
`
`Intel Corp. et al. Exhibit 1004
`
`Intel Corp. et al. Exhibit 1004
`
`

`
`7
`plate having a large-diameter hole in its center and
`small-diameter holes about the periphery of the large-
`diameter hole; the shower plate is disposed in front of
`the substrate which is disposed inside the vacuum treat-
`ment chamber. Also in this construction, the vacuum
`exhaust pipe is connected to that side of the two cham-
`bers in which the substrate is located, and the reactive
`gas introduction pipe is connected to the other side of
`the two chambers. Reactive gas introduced into the
`vacuum treatment chamber contacts the entire resist
`
`film through the plurality of perforations all at once
`creating a shower effect. The resist film decomposes
`and evaporates at a number of locations simultaneously
`through contact with the radicals of the reactive gas
`and can be removed uniformly at a rapid ashing speed.
`By providing a hole with large diameter in the center of
`the perforated plate, ashing can be performed with
`better uniformity.
`Embodiments of this invention are explained in ac-
`cordance with the accompanying drawing FIG. 11. In
`this drawing reference numerals 1 through 13, 50 and 51
`denote the same elements as those of reference numerals
`1 through 13 and 50 and 51 of FIGS. 1 and 2.
`A first embodiment of the present invention incorpo-
`rates a semiconductor substrate 1 constituted by a sili-
`con wafer coated with a resist and supported by a rack
`8 above a heating means 51 which has an infrared lamp
`5 inside a vacuum treatment chamber 4 which is pro-
`vided with a reactive gas introduction port 2 and a
`vacuum exhaust port 3.
`FIG. 11 shows another embodiment in which a sub-
`strate 1 coated with a resist is disposed on a heating
`means 51 which incorporates a hot plate 7.
`In any of the embodiments the reactive gas introduc-
`tion port 2 is provided with a plasma applicator 50 for
`converting the reactive gas to plasma, the plasma appli-
`cator comprising an electric discharging means such as
`a microwave discharging member 2a, RF coil, and the
`like. Thus, oxygen gas or a reactive gas obtained by
`mixing oxygen gas with CF4, N2 or H2 is excited by
`plasma and is introduced into the vacuum treatment
`chamber 4. The vacuum exhaust port 3 is connected to
`an appropriate vacuum pump to exhaust the vacuum
`treatment chamber 4 to maintain an atmosphere below
`l0"4 Torr, for example.
`The apparatus of the first embodiment of the present
`invention is similar
`to the conventional apparatus
`shown in FIG. 1. However, the substrate 1 has a resist
`film 11 with a surface layer 11::
`represented by
`CXI-I yN2 which has been affected and hardened as
`shown in FIG. 5. The reactive gas excited by oxygen
`plasma and the like which is introduced from the reac-
`tion gas introduction port 2 is caused to act on the resist
`film 11 without switching on the infrared lamp 5 at the
`beginning. When the surface layer portion He has been
`removed by decomposition and evaporation through
`chemical reactions with oxygen radicals or radicals of
`the reactive gas, the lamp 5 is activated to heat the
`substrate 1 and accelerate the chemical reactions with
`oxygen radicals or radicals of the reactive gas to rapidly
`remove the resist film 11. The temperature of the sub-
`strate in this process is controlled as shown by the curve
`C shown in FIG. 12; lamp 5 is activated after a lapse of
`time t1, which is required for removing the surface layer
`portion 11a, and the substrate reaches 200° C. in about
`5 seconds, as in the conventional process, to rapidly
`remove the resist film 11.
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`45
`
`50
`
`55
`
`60
`
`65
`
`5,226,056
`
`8
`In the apparatus shown in FIG. 11, a plurality of pins
`16 are connected to and moved up and down by a lifting
`apparatus 15 which encompasses an air cylinder located
`outside the vacuum treatment chamber 4. When pins 16
`are lowered the substrate 1 is placed on the hot plate 7.
`If the apparatus in FIG. 11 is used to remove the resist
`film 11 the temperature change of the substrate is shown
`by curve D in FIG. 13. When the time t1 required for
`removing the surface layer portion 11a is over,
`the
`substrate 1 is lowered onto the hot plate 7; the substrate
`then reaches 200° C. in about 10 seconds, as in the heat-
`
`ing step of an apparatus having a conventional hot plate.
`After heating the removal of the remaining resist film 11
`is performed.
`In the apparatus of each of the embodiments dis-
`cussed above, since the resist film 11 is removed by first
`removing the surface layer portion lla at a low temper-
`ature and then the remaining portion at a high tempera-
`ture, the resist is removed without exploding the inter-
`nally stressed resist film 11. It is therefore possible to
`prevent the vacuum treatment chamber from being
`contaminated with flakes of the resist film 11, and fabri-
`cation of accurate and hyperfine circuits can be per-
`formed.
`Two further embodiments are shown in FIGS. 14 and
`15. In these figures reference numerals 1 through 16, 50
`and 51 denote the same elements as those shown in
`FIGS. 1, 2, and 11.
`'
`In the embodiment shown in FIG. 14 a plurality of
`pins 16 are provided inside a vacuum treatment cham-
`ber 4 such that they project upwards through a heating
`means 51 which incorporates a plurality of infrared
`lamps 5. A vacuum exhaust port 3 is provided below the
`heating means. The rear surface of a substrate 1 is sup-
`ported by the tips of the pins 16 so that a distance 17 is
`formed between the substrate 1 and heating means 51.
`In the embodiment shown in FIG. 15, a plurality of
`pins 16 penetrate a heating means 51 (in the direction
`shown) which encompasses a hot plate 7. As a result the
`pins are introduced into the vacuum treatment chamber
`4 from the outside thereof through a chamber wall 4a.
`Each pin 16 is connected to a lifting apparatus 15 which
`includes a cylinder provided outside the vacuum treat-
`ment chamber 4 such that it is freely movable in the
`upward and downward directions. A vacuum exhaust
`port 3 is provided below the heating means. Through
`the movement of the lifting apparatus 15, the substrate
`1, supported on the end of pins 16,
`is made to move
`between a retracted position at which the substrate 1
`contacts heating means 51 and an advanced position at
`which a distance is formed between the rear surface of
`the substrate 1 and heating means 51. Reactive gas to be
`sent from a reactive gas source 2b to the inside of the
`vacuum treatment chamber 4 is oxygen gas or a gas
`obtained by mixing oxygen gas with a small quantity of
`CF4, N2, or H; and H2 is preferable.
`In the embodiment shown in FIGS. 14 and 15 the
`resist film 11 on the substrate 1 is removed by heating
`the substrate 1 to, for example, 200' C. by heating means
`51; introducing the reactive gas in which radicals are
`generated by the operation of a plasma applicator,