Resist compositions including thermal crosslinking agents

Abstract

A method for forming a fine pattern in a semiconductor substrate, by coating a target layer to be etched on a semiconductor substrate with a resist composition including at least one compound capable of forming a photoresist pattern by a photolithography process, and a free radical initiator. The free radical initiator is capable of being decomposed by a thermal process at a temperature equal to or higher than the glass transition temperature of the at least one compound. A lithography process is performed on the resist compound layer to form a photoresist pattern. The resist compound layer having the photoresist pattern formed therein is heated to a temperature equal to or higher than the glass transition temperature of the at least one compound, and wherein a partial cross-linking reaction in the resist composition occurs.

Description

FIELD OF THE INVENTION The invention generally relates to methods for fabricating semiconductor substrates and compositions of matter employed in such methods. BACKGROUND OF THE INVENTION In a general process for forming patterns for semiconductor memory devices, after a photoresist pattern is formed on a predetermined target layer to be etched for forming patterns, the target layer is typically etched to a desired pattern using the photoresist pattern as an etching mask. Examples of target layers include silicon layers, insulating layers, or conductive layers. Because of the ever increasing integration of semiconductor devices, it is important to develop lithography technology to form contact holes in the semiconductor devices having smaller opening sizes or finer patterns having narrower spaces. Stated differently, it is believed important to develop design criteria for smaller critical dimensions (CD) in the devices. A photolithography technique employed for forming fine conta...

AI Technical Summary

Benefits of technology

It is an object of the present invention to provide methods for forming fine patterns through thermal flowing of photoresist patterns, in which distortion of the profile at the side walls of openings or spaces is minimized, leading to a further reduction in smaller feature size.

In one aspect, the invention provides methods for forming fine patterns in semiconductor substrates. The method first comprises coating a target layer to be etched on a semiconductor substrate with resist compositions. The resist compositions comprise compounds capable of forming a photoresist pattern by a photolithography process, and crosslinking agents. The crosslinking agents are those which are capable of causing partial crosslinking reactions at temperatures equal to or higher than the glass transition temperatures or the softening temperatures of the compounds. The coating steps result in forming resist compound layers comprising the compounds. Thereafter, lithography processes are performed on the resist compound layers to form photoresist patterns of at least one opening having a first width, wherein the target layer is exposed through the first width. Next, the resist compound layers having the photoresist patterns formed therein are heated to temperatures equal to or higher than the glass transition temperatures or the softening temperatures of the compounds, and partial cross-linking reactions in the resist compositions occur. Modified photoresist patterns result having at least one opening having a second width which exposes the target layer, wherein the second width is smaller than the first width. The methods of the invention are believed to be desirable in that the flow rates of the photoresist patterns may be controlled. Moreover, the methods are potentially simpler relative to conventional methods.

In another aspect, the invention provides resist compositions. The resist compositions comprise compounds capable of forming photoresist patterns by photolithography processes, and crosslinking agents. The crosslinking agents are capable of causing partial cross-linking reactions in the resist compositions to form resist compounds at temperatures equal to or higher than the glass transition temperatures or the softening temperatures of the compounds. The crosslinking agents are advantageous in that they may be employed with a number of compounds without adversely affecting the performance of the resist compositions.

In addition to the above, the invention is potentially advantageous in that the distortion of the profile at the side walls of contact holes is minimized, thus allowing for the formation of vertical sidewall profiles. In addition, fine openings which go beyond the wavelength limits in general photolithography technologies can be formed in the photoresist patterns.

Problems solved by technology

In particular, the method employing the exposure tool of shorter wavelength is believed to be disadvantageous in that it is material-intensive and thus relatively expensive to implement.

Moreover, a method that utilizes the half-tone phase shift mask is believed to possess limitations in mask manufacturing technology and resolution.

Accordingly, it may be difficult to obtain contact holes smaller than 150 nm.

Notwithstanding any possible advantages, the above procedure is potentially disadvantageous in that the flow rates in the upper and middle parts of the photoresist pattern are often different.

Due to the difficulty in controlling the flow rate of the photoresist pattern by employing conventional resist flow technology, it is often extremely difficult to reduce the CD of the photoresist pattern while maintaining a vertical pattern profile.

Potential problems may be associated with the '802 patent.

In general, the degree of tapering at the side walls of the opening tends to vary among the openings, thereby undesirably causing different critical dimensions to a plurality of holes formed in the target layer over the entire wafer surface.

As such, it is typically difficult to obtain a good sidewall profile in a flowed photoresist pattern employing conventional technology.

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