CA1263795A - Photopatternable dielectric compositions and method for making and using - Google Patents

Abstract

PHOTOPATTERNABLE DIELECTRIC COMPOSITIONS
AND METHODS FOR MAKING AND USING

ABSTRACT OF THE DISCLOSURE

A photosensitive polyamide acid composition consisting essentially of chemically combined units of the formula where R is a tetravalent organic radical or a tetravalent organosiloxane-containing radical, R1 is a divalent organic radical or a divalent organosiloxane-containing radical, and A
is a photoreactive acrylate, cinnamate or 2,3-diphenylcyclopro-penol ester containing radical.

Description

- lZ63795 PHOTOPATTERNABLE DIELECTRIC COMPOSITIONS
AND METHODS FOR MAKING AND USING
, Backgrnund of thP lnvention The present ;nvention relates to novel photoreslst composi-tions and methods of making and using such compositions. More particularly, the present invention provides photol~thographic methods for making photoresists by reacting a polyamic acid with a photoreactive compound, applying the photoreactive reac-tion product to a substrate and allow~ng ~t ~o dry, exposing the treated substrate while it ~s masked to a source of light so as to effect crossl~nk~ng of the photoreactive groups, and heating the resultlng crosslinked coatlng at a temperature effective for convert~ng the coating to a polyimide. The present invention also relates to novel polyimide precursor compositions and methods for making such compositions.

Prior to the present invention polyimides and polysiloxane imides were obta~ned by effectins reactlon between a carboxylic acld dianhydrlde and `a diamino compound and/or diaminopolysi-loxane to obtaln an init~al reaction product havlng the fonmula, for example, _ _ _ . , _ _ _ _ , . , .... ... . . ... .. .. . . . _ .... .. .

GLL:mz O O Q

_ - N - C ~ - C ~ , C - NH - R - ~
HO - C - ~ ~ C - OH n R = aliphatic and/or aromatic and/or siloxane Upon heating at a temperature of about l 50DC to 350C the poly-meric amido compound cyclized to y~eld an imidized composition of recurring units of the fonmula, for example, ~ O O o C 11 lCI ~
~N ~ ~ N - ~

Il 11 O O

R = aliphat~c and/or aromatic and/or s~loxane This method ~s descr1bed more fully in U.S. Pat. Nos. 3,325,450 and 3,553,282, among other patents and literature references.

( ~ --~Z6379~;

GLL:mz Photores~st materials which are based on a photoreactive precursor are described by Rubner et al. ln "Production of Highly-Heat Resistant Film Patterns from Photoreactive Poly-meric Precursors, Part I, General Principles ~Jan: 1976)~ and "Production of Highly-Heat Resistant Film Patterns from Photo-reactlve Polymerlc Precursors, Part 2, Polyimide Film Patterns (May 1976)". A photoreact~ve polyamide is made by initially e~fecting reactlon between an aromatic dianhydride, for example, pyromellitic dianhydride, and allyl alcohol. The resulting aromatic dicarboxylic acid diester is then converted to the correspond;ng aromatic dlacid chloride by reaction with thionyl chloride. The diacid chloride is further reacted with an aromatic diamine to produce a photoreactive aromatic poly-IS am~de ester. The aforementloned photoreactlve polyimide precursor is then applied to a substrate, for example by spln coating, and exposed to light with the aid of a mask, followed by developing the treated surface with an organic solvent to produce a photoreslst. The aromatic patterned polyamide ester is then heated to convert it to a patterned polyimide.
Although valuable results have been achieved with the aforementioned photoreactive aromatic polyamide ester, those skilled in the art recognize that the use of a chlorinating agent such as thionyl chlorlde to convert the aromat~c dicar-boxylic acid to the corresponding ac1d chloride prior to the polymerization reaction with aromatic diamine can result in the introductlon of residual chlorlde contam~natlon. Such chlorlde contaminatlon can lnterfere with the u~llity of the resulting aromatic polyimide as a dlelectric.

3 ~

GLL:mz 1 It is, therefore, des~rable to proYide a photosensittve polyamide acid useful and a photoresist and convertible to a patterned insulat~ng layer free of chloride contam~nation.

Summary of the Invention It is one object of the present invention to provide a method for pattern~ng an insulative polyimide or silicone-poly-imide layer on a substrate.

It is another object of the present invention to provide a photosensitive polyam~de acid or silicone-polyamide ac~d.

Another object of the present invent~on is to provide a method for making photosensitive polyamlde acids and silicone polyamide acids.

In accordance with the present invPntion a photosensitive polyamide acid useful as a photoresist and convertible to a patterned insulating layer free of chloride contamination can be made by reacting a dianhydr~de of the general formula C C
~ \ / \
0 R 0 (1) C C
Il 11 O O

~LZ63795 60SI-339/4617L
GLL:m~

1 with a diamine of the general fonmula H2N - Rl - NH2 (2~

to obtain a polyamide ac~d consisting essent~ally of chemically combined units of the formula O O ~
~ 11 li \
/ HO - C C - OH

- N C C - N - Rl ¦ (3 1¦ 10 \ H O O H

where R is a tetravalent organic radical or a tetravalent organosiloxane-containing radical and Rl is a d;valent organic radical or a divalent organosiloxane-containing radical.

The polyam;de acid of fonmula (3) is further reacted with a photosensitive acrylate, cinnamate or 2,3-diphenylcyclopropenol ester ~n order to provide a modified or photoreact~ve polyam~de acid consistlng essent~ally of chemically combined units of the fonmula

2 6~3~7~3~i GLL:mz O O
Il 11 ~
~. - O - C\ R ~ ~ - A ~ (4) / \ 1 \ N - C C - N - R ~ f-----where R and Rl are as previously defined and A is a photo-reactive acrylate, c~nnamate or 2,3-d~phenylcyclopropenol ester.

In another aspect of the present invention there is provi-ded a method for patterning an insulat~ve polylmide or 5s~licone-polyimide layer on a substrate which comprises:

(1) dissolving the photoreactive polyamide acid of fonmula (4) in an inert solvent;

(2) applying a coating of the solution of fonmula (4) to a substrate, for example,---by sp~n coating, in the~
10substantial absence of light;

(3) allow~ng the coated substrate to dry;

(4) exposing the coated substrate for a tlme sufficient to crosslink the desired photoreactive polyamide molecules;

~26:~7~S

(5) developing the resulting crosslinked polyamide acid coated substrate; and

(6) heating the developed crosslinked polyamide acid coated substrate at a temperature effective for converting the polyamide acid to a polyimide.

Description of the Invention In accordance with the present invention, a photosensitive polyamide acid useful as a photoresist and convertible to a patterned insulating layer free of chloride contamination is prepared by first reacting a dianhydride of formula (1) with a diamine of formula (2) to provide a non-photosensitive polyamide acid having the general formula (3).
Generally it is not critical what dianhydride and diamine are used and the skilled artisan can readily select those most suitable for his contemplated use.
The dianhydride has the general formula (l) where R is a tetravalent organic radical or a tetravalent organosiloxane-containing radical. Suitahle dianhydrides and their method of preparation are described in U.S. Pat. Nos. 3,553,282 to Holub and 4,030,948 to Berger.
Illustrative of the dianhydrides suitable for use in the present invention are pyromellitic dianhydride;
2,3,6,7-naphthalene tetracarboxylic acid dianhydride;
3,3',4,4'-diphenyl tetracarboxylic acid dianhydride;
1,2,5,6-naphthalene tetracarboxylic acid dianhydride;

, .,/
~,, 37~S ~

GLL:mz 2,2',3,3'-dfphenyl tetracarboxylic ac~d dfanhydr~de;
2,2-b~s (3,4-dlcarboxyphenyl)propane d~anhydrfde;
bfs (3,4-dfcarboxyphenyl) sulfone dianhydrfde;
3,4,3,10-perylene tetracarboxylic acfd dfanhydrfde;
bfs (3,4-dicarboxyphenyl) ether d~anhydride;
2,2-bis (2,3-dicarboxyphenyl) propane dfanhydrfde;
l,l-bfs (2,3-d~carboxyphenyl) ethane dianhydride;
bis (3,4-dicarboxypheny7 ~ methane dianhydride;
1 bfs (2,3-dicarboxyphenyl) sulfone dfanhydrfde; and benzophenone tetracarboxylfc acfd dianhydrfde.

Generally the preferred dfanhydrides of fonmula (1) are where R is a tetravalent C(6 303 aromatfc radical selected from ~' .

~ ~

O O
~ IC _ Q

and ~ - R5 -2~i3 7 9~; C ~

GLL:mz 1 where Q ~s a divalent radical having the fonmula - ZR6Z -where Z is selected from -O- and -NH-, and R5 and R6 are selected from C~2 13) organic radicals.

Also acyclic or cycllc aliphat~c dianhydr~des such as cyclopentane tetracarboxylic acid dianhydrfde, cyclohexane tetracarboxylic acid dlanhydride, butane tetracarboxylic ac~d dianhydride and the like are suitable for use ~n the present invention.

Organosiloxane-containing dianhydrides are also within the scope of the present invent~on and preferably have the general fonmula o~ 3 ~~s~

o o o where D is a di-nitrogen or di-oxygen tenminated siloxane.
Dianhydrides of formula (5) can be prepared by reacting trimel-litic chloride, ~.e.

Il ~ IC - Cl O O

~26379~

GLL:mz 1 with any diamine or dialcohol, preferably having siloxane linkages. Accordingly, siloxane-containing dianhydrides of the present invention have formulas such as, for example, ) ~ 3 L C N R3~ S~-R3- N - C~/>~

S and \ ~ G - oR3 ~ si-R3- o - C

where R3 is a subst~tuted or unsubstituted hydrocarbon radical, preferably haYing from 1 to 8 carbon atoms, and n has a value of from 1 to about 200 and preferably from 1 to about 100.

G G
1~379S

GLL:mz The most preferred dianhydr~des are pyromell~tic d~anhy-dride, benzophenone tetracarboxylic ac~d dianhydr~de and ~ ~0~ 0 Illustrative of the aminosiloxanes which can be reacted lS ~ith trimellitic chloride to obtain s~loxane-containing dian-hydrides are fH CH

H2~ CH2 ~ S~ - O - S~ CH2 ~ 2 ' ~Jhere n preferably equals 2 through 6 inclusive and most preferably equals 3. ~~ ~ ~~~ ~ ~~
l6H5 l6HS
H2N - C6H4 ~ C - li - C6H4 2 ~ c) 605I-33g/461 7L
GLL:mz H2N ~ 5l 0 -- S7 ~ ~ NH2 CH3 ~ CIH3 ~ IH3 H2N ~ cH2~ liO t li r 1~ ~ cH2~ NH2 CH3 ~ 3 J x 3 where n i5 aspreviously defined and I ~ IH
H2N ~ CH2)n- ji- ~ i~-t si ( CH2~n NH2 B ~ C2H4 ~ x P' 2~
B = CH3 and/or phenyl where n ~s as previously defined. Of course, dialcohol end-stopped compounds can be used in place of the diamino end-stopped compounds. In either case, the method for preparing the siloxane-containing dianhydrides is well known to those skilled in the arS.

J
2~;3 7 9~i GLL:mz 1 Generally Rl of the dlamlne of formula (2) has the formula ~r {~}~} Y ~}~ {~}' where Y is -S-, 5 or ~ 3 ~ z ~ 3 where Z is CH2, ~H3 or -0--C-~H3 R7 ~ R ~ R7 I \
- R7 - Si 0 Si / 0 Si - P~7 -R7 R7~ X R7 where R7 is a C(1,13) organic radical and x = 1 to about 200'.
Of course, other variations will be obvious to the skilled artisan.

G CJ
~1263~

GLL:mz D1amlnes wh1ch can be reacted w1th the forego1ng dianhy-dr1des to obtain non-photosens1t1ve polyamide acids are well known In the art and are also described in U.S. Pat. Nos.
3,553,282 and 4,030,948. D1amines within the scope of formula (2) include for example, n-phenylenediam1ne;
p-phenylenediamine;
4,4'-diaminodiphenylpropane;
4,4'-diaminodiphenylmethane;
benzidine;
4,4'-diaminodiphenylsulfide;
4,4'-diaminodiphenyl sulfone;
4,4'-diaminodiphenyl ether;
l,5-diaminonaphthalene;
3,3'-dimethoxybenzidine 2,4-bis IB-amino-t-butyl) toluene;
1,3-diamino-4-isopropylbenzene;
m-xylyened1amine;
p-xylenediamine;
2,2-d1methylpropylenediam1ne;
l,4-cyclohexanediamine; and bis (3-aminopropyl) sulfide.

This listing of suitable am1nes, as with the previous list-ing of su1table dianhydrides, is not intended to be exclusive as those skilled in the art recognize that a complete listing is not feas1ble. It should be noted that in add1tion to organ1c diamines, there are also 1nc1uded w1thin the scope of 3~ fonmula (2) di(aminoalkyl)polysiloxanes as disclosed herein-above for reaction with trimellitic chloride to obtain dian-hydrides.

G ~ J
~i3Y7~3~;

GLL:mz The react10n product of the dlanhydrlde and the dlamlne ~s a polyamlde-acid of chem~cally combined unlts of fonmula (3), i.e., ~ O O

/ HO - C C - OH

l \ /
R

-- ~ - C C - N - Rl /
\ I Ol 11 ~ H O O H ~

where R ls the tetravalent organic or organos~loxane-containing radical of the dianhydride and Rl ~s the divalent organic or organosiloxane-contalning radical of the dlam~ne.

In order to provide a photosensitive or modified polyamide acid, ~t has been found desirable to react the polyamide ac~d of formula (3) with a photosensit~ve acrylate, cinnamate or 2,3-diphenylcyclopropenol ester. So that the photosensitlve compound will reac~ wlth the polyamide acld of fonmula (3) to provlde the photosensltiYe modifled polyamide ac~d of formula (4) lt is necessary that the compound have a functlonal group which will replace the acid hydrogen of the polyamide acid, for examp1e, an epoxy contaln~ng group such as glycidyl.

G

GLL :mz In order that those skllled ~n the art wlll more clearly under-stand the react~on between the polyam~de acld and the photo-sensitlve compound the following ~llustrat~on ~s provided.
O O
HO - C C - OH

~ I 11 F~ I ~7L
H O O H
x OH O O OH

2 \ ~ 2 - B

N - C C - N - Rl /
1 11 11 1 ~
H O O H x ~Z6379~i 60SI-339/4~17L
GLL:mz where R is a divalent Cl 8 radical, B is ~ photosensltive acrylate, cinnamate or 2,3-diphenylcyclopropenol ester, R and Rl are as prev10usly defined, and x illustrates that substan-tially equimolar quantities of reactants are utilized.
Included among the su~table photosenslt~ve compounds are:

glycidyl methacrylate;
glycidyl cinnamate;
glycidyl-2,3-diphenylcyclopropenol glycidylallylphthalate glycidylallylether The most preferred photosensitive compounds are glycidyl methacrylate, glycidyl cinnamate, and glycidyl-2,3-diphenyl-cyclopropenol.

Modification of the polyamide acid or silicone-polyamide acid ~s effected by agitating a mixture of the acid and photo-sensitive compound in the substantial absence of light and in the presence of an appropriate organ~c solvent such as N-me~hyl pyrolidinone, dimethylacetamide, dimethylformamide dimethoxy-ethane, diethyleneglycoldlmethylether, and dimethylsulfoxide.

.

~2637~;

GLL:mz Generally the reactiDn mixture should be st~rred at room temperature for a per10d of from about 8 to about 24 hours.

After modifkation of the polyamide acid with the photo-sensitive compound, if desired, the resulting modified polymer can be sensitized wlth an appropriate photoinitiator. There can be util~zed from about O.lX to about lOX by weight of photoinitiator based on the we~ght of the mod~fied polyamide acid. Suitable photoinitiators or sensitizers are, for example, Michler's ketone, benzophenone, and 2,2-dimethoxy-2-phenylacetophenone, each with N-methyldiethanolamine.

Such modified or photoreactive polyamide acid compos~t~ons are useful as photoresists whkh are convert;ble to a patterned insulating layer in electronic devices, particularly integrated circuits. Accordingly, the present invention also provides a method for obtaining an insulative polyimide layer on a sub-strate such as a silicon wafer from the foregoing photosensi-t~ve polyamide acid composition.
Initial~y the photosensitive polyamlde acid composition is dissolved in a suitable ~nert solvent such as tetrahydrofuran, dimethylformamide, N-methylpyrrolidinone, dimethylsulfoxide and ethyleneglycoldimethoxyether.----The percent solids ~n -the solu-tion can range anywhere from about 5 to about 95 percent by weight sol~ds, but most preferably ranges from 5 to 25 weight percent solids.

G
i2~

GLL:mz The substrate surface, which typically is a s~licon wafer, must he properly cleaned to ensure adequate resist wetting and adhesion.
s There are several methods by which a substrate may be coated w~th the photores~st. The method chosen w~ll depend on the need for uniformity and the th1ckness of the coating deslred~ Spin coating ~s particularly advantageous in the microelectronics industry where a thin unifonm coating of a photoresist i5 applied to one side of a small part of the substrate and where a high degree of uniformity is desirable.
In spin coat~ng the thickness of the resulting film is controlled by adjusting the spinning speed and the solids content of the resist solution.

Other methods of applying the photores~st to the substrate are spray coating, dip coating and roller coating. Spray coating is probably the best way to apply a thick coat~ng, however, it results in waste of the photores1st mater~al. Dip coating provides the most uniform coatings but it is relatively slow and has llmitations in coating thickness. Roller coat~ng is a method of uniformly applying very thin coatings to rigid surfaces.
~5 After applying the photoresist to the substrate it ~s often desirable, though optional, to oven dry or pre-exposure bake the photores~st. This bake eliminates residual solvent, promotes adhesion, and hardens the res1st. Temperature and time depend upon the specific resist being used, but generally are from 70-90C and 10-30 minutes, respectively.

f~J
~2~:~9~

GL~:mz The photoresist 1s next exposed using a light source wh~ch provides optical energy over a wavelength band that is contained within the reslst absorption spectrum. Several techniques are known for carrylng out the exposure. The oldest and prnbably most widely used technique is contact pr~nting in wh~ch ~he wafer is pushed ~nto ~nt~mate contact w~th a mask and then the mask ~s f~ooded w~th l~ght. In proxim~ty pr~nt~ng the mask and wafer are separated by a gap, nominally from lO ts 25 mm. In project~on prin~ing a high quality lens or mirror system ls used to project the mask ~mage onto the wafer surface. The purpose of the exposure step is to crosslink the photoreact~ve portions of the photoreslst that were exposed to the light while the masked or unexposed portions rema~n uncrosslinked and hence soluble in selected solvents.

I5 Development of the photores~st ~nvolves contacting the exposed photoresist with a solvent wherein the crosslinked polyamide acid is insoluble but the uncrosslinked polyamide acid is dissolved thereln. Th~s leaves a tough, chemlcally resistant mask on the surface of the substra~e.
Finally, the developed photoresist ~s heated at a tempera-ture sufficient to convert the polyamide acid to a poly~mide.
Generally the temperature necessary to effect imidization ranges from about 200-C to about 300-C and the time req~ired ranges fnom about 30 to about 60 minutes.
In order that those skilled ~n the art will be better able to practice the invention, the following example ls given by way of illustration and not by way of limitation. All parts are by ~eight.

G C~
Z~3~
60SI~339/4517L
GLL:mz -Zl-1 Example A polymer was prepared by adm~x~ng 0.11 mole (22 grams~ of oxyd~an~line, 0.03 mole (7.44 grams) of bis-aminopropyltetra-methyldisiloxane and 150 ml tr~glyme ~n a 500 ml flask. There-after 74.0 grams ~0.144 mole) of bis-phenol A d~ankydr~de was added to the m~xture. This was followed by the addit~on of 90 ml tetrahydrofuran. The mixture was st~rred overn~ght and then 0.144 mold (20.5 grams) glycidoxy methacrylate was added. Such mixture was stirred an addit~onal 24 hours.

A 50 gra~ sample of the result~ng polymer was d~luterd to 10~ sol~ds with tetrahydr~furan. 3~ by we~ght of Irgacure ~51 photoinitiator was then added. The resulting solution was flow coated on an aluminum substrate. The solvent was removed by air drying for 30 minutes and thermally drying at 75-85nC for one hour. The aluminum substrate was partially masked and exposed for 10 seconds ~N2 atmosphere) to ultraviolet light.
The aluminum substrate was washed w~th tetrahydrofuran. The unexposed area dissolved in the solvent whereas the exposed area remained on the alum~num substrate.

Claims (13)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A photosensitive polyamide acid composition substantially free of chloride consisting essentially of chemically combined units of the formula where R is a tetravalent organic radical or a tetravalent organosiloxane-containing radical, R1 is a divalent organic radical or a divalent organosiloxane-containing radical, and A is a photoreactive acrylate, cinnamate or 2,3-diphenylcyclopropenol ester containing radical.

2. The composition of claim 1 wherein the photosensitive polyamide acid composition is prepared by reacting a polyamide acid consisting essentially of chemically combined units of the formula with a photosensitive compound of the formula where R is a tetravalent organic radical or a tetravalent organosiloxane-containing radical, R1 is a divalent organic radical or a divalent organosilcxane-containing radical, R4 is a divalent radical having from 1 to 8 carbon atoms and B is a photosensitive acrylate, cinnamate or 2,3-diphenylcyclopro-penol ester containing group.

3. The composition of Claim 1 wherein R of the photo-sensitive polyamide acid is a tetravalent C(6-30) aromatic radical selected from and where Q is a divalent radical having the formula where Z is selected from - O- and - NH -, and R5 and R6 are selected from C(2-13) organic radicals.

4. The composition of Claim 1 wherein R of the photo-sensitive polyamide acid has the formula where D is a di-nitrogen or di-oxygen terminated organosiloxane.

5. The composition of Claim 1 wherein R1 of the photo-sensitive polyamide acid is a divalent radical of the formula where Y is -S-, or where Z i s CH2, or -0- where R7 is a C(1-13) organic radical and x = 1 to about 200:

6. The composition of claim 1 wherein A
is a radical derived from glycidyl 2,3-diphenyl-cyclopropenol.

7. The composition of claim 1 wherein the photosensitive polyamide acid composition is dissolved in an inert solvent.

8. The composition of claim 7 wherein the solids content ranges from about 5 to about 95 percent by weight solids.

9. The composition of claim 1 further consisting essentially of an effective amount of sensitizer.

10. A method for patterning an insulative polyimide layer onto a substrate, comprising:
(a) dissolving a photoreactive polyamide acid composition substantially free of chloride consisting essentially of chemically combined units of the formula where R is a tetravalent organic radical or tetravalent organosiloxane-containing radical, R is a divalent organic radical or a divalent organosiloxane-containing radical, and A is a photoreactive acrylate, cinnamate or 2,3-diphenylcyclopropenol ester, in an inert solvent;

(b) applying a coating of the dissolved photoreac-tive polyamide acid composition to a substrate in the substantial absence of light;
(c) allowing the coated substrate to dry;

(d) exposing the coated substrate for a time suffic-ient to effect crosslinking of specified areas of the photoreactive polyamide acid;

(e) developing the resulting crosslinked polyamide acid coated substrate; and (f) heating the developed crosslinked polyamide acid coated substrate at a temperature effective for converting the polyamide acid to a polyimide.

11. The method of Claim 10 wherein step (d) is effected by contact printing.

12. The method of Claim 10 wherein imidization is effected by heating at a temperature of from about 200°C to about 300°C
for 30 60 minutes.

13. A method for making a photosensitive polyamide acid composition comprising agitating a mixture of a polyamide acid substantially free of chloride con-sisting essentially of chemically combined units of the formula with a photosensitive compound of the formula where R is a tetravalent organic radical or a tetra-valent organosiloxane-containing radical, R1 is a divalent organic radical or a divalent organosiloxane-containing radical, R4 is a divalent radical having from 1 to 8 carbon atoms and B is a photosensitive acrylate, cinnamate, or 2,3-diphenylcyclopropenol ester radical.