Radiation imagery chemistry: process – composition – or product th – Imaging affecting physical property of radiation sensitive... – Radiation sensitive composition or product or process of making
Reexamination Certificate
2001-07-17
2003-07-01
Ashton, Rosemary (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Imaging affecting physical property of radiation sensitive...
Radiation sensitive composition or product or process of making
C430S313000, C430S326000, C430S905000, C526S266000, C526S279000, C526S319000
Reexamination Certificate
active
06586156
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to photolithography, and more specifically to a chemically amplified (CA) photoresist system wherein a terpolymer containing ketal, phenol and silicon based side chains is utilized. Among other things, the terpolymers of the present invention provide for improved bake technologies. In another aspect, the present invention relates to a process for lithographic treatment of a substrate by means of ketal/phenolic/silicon-based compositions and corresponding processes for the production of an object, particularly an electronic component.
2. Description of the Prior Art
In recent years, resolution capacity that can be obtained with conventional deep-UV microlithography has reached its limits. Normally, it is no longer possible to produce conventional structures on a substrate with dimensions of less than 0.25 &mgr;m, as is required for the production of particularly highly integrated electronic components that have been targeted recently. Such conventional structures have minimal dimensions down to approximately 0.10 &mgr;m. In order to be able to resolve sufficiently, in an optical manner, such fine structural elements, short wave radiation must be utilized which generally has a wavelength between 126 and 260 nm.
Chemically amplified (CA) resists have multifarious commercial applications, many of which predominate in the semiconductor industry. There, CA resists are used inter alia for lithographic procedures occurring at 248 nm or less wherein the chemistry is not driven directly by photons absorbed in the exposure step, but rather by an acid formed during exposure of a photo-acid generator (PAG) which catalyzes chemical changes in the resist during a bake step immediately following exposure. Since the reaction is catalytic, the acid is regenerated after each chemical reaction; the same acid molecule can participate in further reactions.
The biggest advantage of a CA system is in its speed. These materials further express high contrasts and typically have very high resolution, with gamma values of 5-10 vs. 2-3 for novolak resists (Seeger, David “Chemically Amplified Resists for Advanced Lithography: Road to Success or Detour?”
Solid State Technology;
June 1997; pp.115-121). However, the catalytic nature of the CA process makes reproducibility an important concern. Should the catalytic chain be interrupted unexpectedly, many lithographic important reactions would not take place, thereby resulting in catastrophic resist failures. The most common interruptions occur when an airborne base penetrates into the photoresist and quenches the photo-generated acid, resulting in skins on the surface of the resist which prevent clean development from occurring.
U.S. Pat. Nos. 6,156,682; 6,146,793; and 5,985,524 all discuss bilayer resists wherein a base underlayer material is etched with oxygen. After the resist image is developed in tetramethylammonium hydroxide the polymeric underlayer is then oxygen etched and the image is transferred. Thus the etched out polymeric underlayer becomes an etching mask, which is sufficiently thick so as to be able to withstand most etching processes. However these materials are not suitable for chrome mask making due to their thickness.
Unfortunately, the prior art materials currently in use for chrome mask making remain extremely problematic. Prior art mask making materials are awkward in reactive ion etching. In order to transfer the image from a chrome resist, one must etch the chrome via the conversion of chrome to chrome chloride and combine it with ions for release from the surface, thereby etching the resist down to the glass. This etched region thus becomes a transparent region within the chrome layer. The chrome etch process utilizes chlorine and oxygen gases to form the chrome chloride whereby the chrome material is literally sputtered away to form the non-volatile species, chrome chloride. Thus a great deal of ion bombardment becomes necessary to assist the sputtering or displacement of the chrome oxide from chrome chlorides from the surface. In performing such high ion bombardment, the photoresistant film of carbon also sputters and bombards away, thereby losing more than half the thickness of the film material. This loss of material causes an alignment variation of the final etch chrome feature. Since these resists are very thin to begin with, measuring merely 2,000-3,000 angstroms each, and wherein the chrome layer is approximately 1,200 angstroms thick, the conventional photoresist will lose more than 1500 angstroms of its thickness during such a chrome etch process. Preferably, a material which is capable of resisting chlorine will be developed that can be incorporated into conventional resist compositions.
U.S. Pat. No. 6,187,505 discloses a negative bilayer variation of a silicon oxygen type of polymer backbone which has a phenol OH group attached to a silicon what is commonly referred to as a network lattice. However, to synthesize this polymer a siloxane monomer or a silicon trichloride derivative must be added to an acid or base thereby resulting in a very wide variety of products of that reaction. The use of varied products makes such a synthesis very difficult to reproduce on a large scale.
The kinetics of the catalytic reaction are also important. Careful control of temperature uniformity and bake time must be maintained. Similar to the problems encountered with chrome etching, any nonuniformities will change the critical dimension (CD) on the wafer. The CD variations are a direct effect of variant bake temperatures in so much as the actual bake temperature depends upon the temperature uniformity of the bake plate and the bake latitude of the resist. Even the very best resist systems require a hot plate uniformity on the order of 0.1° C. in order to meet the desired line width control for 0.1-&mgr;m lithography. Since this control is a resist limitation and is beyond current specifications for hot plate uniformities, more advanced lithographies will require improvements to the bake technologies.
U.S. Pat. No. 5,886,119 discloses a terpolymer for use in chemically reinforced photoresists wherein multilayering techniques are desirable. However, these materials further require the bake steps as previously discussed.
U.S. Pat. No. 5,976,759 discloses polymer compositions and resist materials further requiring the contested bake steps.
Unfortunately, the development of a heating system with such high precision uniformly across the plate would cost the industry upwards of close to a million dollars. Thus it becomes clear there is a definitive need in the art for chemically amplified resist materials which do not necessitate a bake step, thereby negating the inconsistency effects of hotplates. Such a material would preferably not require post exposure baking but rather would be reactive at room temperature. Furthermore, there is a need in the industry for a material which will improve the mask making process by providing both very good resistance to chlorine or oxygen type etching gases.
SUMMARY OF THE INVENTION
The present invention is directed to a class of terpolymers and the use of such terpolymers in chemically amplified resists. Particularly, the present invention provides a terpolymer comprising the general structure:
wherein:
a is from about 5 to about 70;
b is from about 3 to about 35;
c is from about 0 to about 92;
R
1
is H, C
1
-C
4
alkyl, aryl, CN, or a halogen, preferably R
1
is H or —CH
3
;
R
2
is H or C
1
-C
4
alkyl, preferably R
2
is H or —CH
3
;
R
3
is a protective room temperature reactive group selected from the group consisting of silylethers, acetals and ketals;
R
4
is an alkyl, hydrogen, halogen, aromatic or another cyclic alkyl group;
R
5
is a silicon-oxygen group maintained thereon;
n is 1, 2, 3, 4, 5, or 6, preferably n is 2 or 3; and
a+b+c=100%.
As will be made clearer herein, the terpolymers of the instant invention unexpectedly manifest significantly lower activation energies as compared to the te
Angelopoulos Marie
Huang Wu-Song
Junyan Dai
Kwong Ranee W.
Lang Robert N.
Ashton Rosemary
Capella Steven
International Business Machines - Corporation
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