Radiation sensitive silicon-containing resists

Details Radiation sensitive silicon-containing resists Radiation sensitive silicon-containing resists

1999-02-02

2001-02-13

Baxter, Janet (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

Reexamination Certificate

active

06187505

ABSTRACT:

DESCRIPTION
FIELD OF THE INVENTION
The present invention relates to high-performance radiation sensitive resist compositions and their use in multilayer lithography processes to fabricate semiconductor devices. Specifically, the present invention is concerned with negative-tone silicon-containing resist compositions based on an acid catalyzed crosslinking of aqueous base soluble silicon-containing polymers. The resist composition of the present invention can be used as the top imaging layer in a multilayer, including bilayer, technique to fabricate semiconductor devices using various irradiation sources, such as mid-ultraviolet (UV), deep-UV (for example 248 nm, 193 nm and 157 nm), extreme UV, X-ray, e-beam and ion-beam irradiation.
BACKGROUND OF THE INVENTION
In the manufacture of patterned devices such as semiconductor chips and chip carriers the steps of etching different layers which constitute the finished product are among the most critical and crucial steps involved.
In semiconductor manufacturing, optical lithography has been the main stream approach to pattern semiconductor devices. In typical prior art lithography processes, UV light is projected onto a silicon wafer coated with a layer of photosensitive resist through a mask that defines a particular circuitry pattern. Exposure to UV light, followed by subsequent baking, induces a photochemical reaction which changes the solubility of the exposed regions of the photosensitive resist. Thereafter, an appropriate developer, typically an aqueous base solution, is used to selectively remove the resist either in the exposed regions (positive-tone resists) or, in the unexposed region (negative-tone resists). The pattern thus defined is then imprinted on the silicon wafer by etching away the regions that are not protected by the resist with a dry or wet etch process.
The current state-of-the-art optical lithography uses DUV irradiation at a wavelength of 248 nm to print features as small as 250 nm in volume semiconductor manufacturing. The continued drive for the miniaturization of semiconductor devices places increasingly stringent requirements for resist materials, including high resolution, wide process latitude, good profile control and excellent plasma etch resistance for image transfer to substrate. Several techniques for enhancing the resolution, such as reduced irradiation wavelength (from 248 nm to 193 nm), higher numerical aperture (NA) of the exposure systems, use of alternate masks or illumination conditions, and reduced resist film thickness are currently being pursued. However, each of these approaches to enhance resolution suffers from various tradeoffs in process latitude, subsequent substrate etching and cost. For example, increasing NA of the exposure tools also leads to a dramatic reduction in the depth of focus. The reduction in the resist film thickness results in the concomitant detrimental effect of decreased etch resistance of the resist film for substrate etching. This detrimental effect is exasperated by the phenomenon of etch induced micro-channel formation during substrate etch, effectively rendering the top 0.2-0.3 &mgr;m resist film useless as an etch mask for substrate etching.
It would therefore be desirable to provide for enhanced resolution without experiencing drawbacks of the prior art.
Furthermore, bilayer imaging schemes have been suggested. In a bilayer imaging scheme, typically, images are first defined in a thin, usually 0.1-0.3 &mgr;m thick, silicon containing resist with a wet process on a relatively thick high absorbing organic underlayer. The images thus defined are then transferred into the underlayer through a selective and highly anisotropic oxygen reactive ion etching (O
2
RIE) where silicon in the top imaging layer is converted into nonvolatile silicon oxides, thus acting as an etch mask. To be effective as etch mask, the top imaging layer needs to contain sufficient silicon, usually greater than 10 wt %
The advantages of bilayer imaging over the conventional single layer imaging include higher resolution capability, wider process latitude, patterning high aspect ration features, and minimization of substrate contamination and thin film interference effects. Moreover, the thick organic underlayer offers superior substrate etch resistance. The bilayer imaging is most suitable for high NA exposure tools, imaging over substrate topography and patterning high aspect ratio patterns.
Various silicon-containing polymers have been used as polymer resins in the top imaging layer resists (see R. D. Miller and G. M. Wallraff,
Advanced Materials for Optics and Electronics, p.
95 (1994)). One of the most widely used silicon-containing polymers is polysilsesquioxane. Both positive-tone and negative-tone resists have been developed using an aqueous base soluble polysilsesquioxane: poly(p-hydroxybenzylsilsesquioxane). For positive-tone bilayer resists, poly(p-hydroxybenzylsilsesquioxane) was modified with a diazo photoactive compound or an acid sensitive t-butyloxycarbonyl (t-BOC) for I-line and chemically amplified DUV lithography, respectively [U.S. Pat. No. 5,385,804, U.S. Pat. No. 5,422,223]. Positive-tone resists have also been developed by using dissolution inhibitors [U.S. Pat. N. 4,745,169]. For negative-tone bilayer resists, an azide functional group was chemically attached to poly(p-hydroxybenzylsilsesquioxane). Exposure of the azide functionalized poly(p-hydroxybenzylsilsesquioxane) caused crosslinking in the exposed regions. Thus, negative-tone images resulted. However, these bilayer resists suffer from inadequate resolution, low sensitivity, and poor resist profile in some cases due to high optical density.
In view of the state of prior art resists, it is desirable to develop new bilayer resists with high resolution, high sensitivity, and good profile control for patterning semiconductor circuities. In particular, new negative-tone silicon-containing resists are desirable since negative-tone resists generally offer advantages of better isolated feature resolution, good thermal stability, small isolated and dense feature bias.
SUMMARY OF THE INVENTION
Accordingly, one object of the present invention is to provide a highly sensitive, high resolution negative-tone resist compositions with relatively high silicon content.
Another object of the present invention is to provide chemically amplified negative-tone silicon-containing resist compositions that can be used as top imaging layer resists in multilayer lithography for semiconductor manufacturing, and, in particular, in the patterning of semiconductor circuities.
These and other objects are achieved according to the present invention by an acid catalyzed, high contrast crosslinking of silicon-containing polymers bearing a phenolic moiety by using crosslinking agents that react with the hydroxyl group of the phenolic moiety in the silicon polymers (O-alkylation). These objectives are achieved also by using a bulky photo-generated acid to reduce acid diffusion for high resolution. More specifically, highly sensitive, high resolution chemically amplified negative-tone resists are obtained by acid catalyzed crosslinking of aqueous base soluble hydroxybenzylsilsesquioxane polymer via O-alkylation. These crosslinking agents include, but are not limited to, uril and melamine derivatives. The O-alkylation not only increases the molecular weight of the parent polymer but also converts the hydrophilic hydroxyl group in the parent polymer into a less hydrophilic phenolic ether group. Both lead to high contrast for the negative-tone resists.
Another aspect of the present invention is directed toward a silicon-containing negative-tone chemically amplified resist composition which comprises (a) an aqueous base soluble phenolic silicon-containing polymer or copolymer; (b) a crosslinking agent; (c) an acid generator; (d) a solvent for said polymer resin and crosslinking agent; and, optionally, (e) a photosensitizer that is capable of absorbing irradiation in the mid-UV, deep-UV (e.g. 248 nm, 193 nm and 157 nm), extreme-U

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