JPH01186934A - Pattern forming method - Google Patents

Abstract

PURPOSE:To selectively absorb a silicon compd. and to form a pattern with high accuracy by setting the temp. of a silylation treatment at the glass transition point of a desired part or above. CONSTITUTION:The difference in the glass transition point between an exposed part 5 and unexposed part 5' is increased and the silylation treatment is executed at the temp. above the glass transition point of the part intended to be absorbed with the silicon compd. and below the glass transition point of the part intended not to be absorbed with the silicon compd. in the case of forming the pattern by a silylation process. The absorption of the silicon compd. at a high selection ratio is thereby enabled and the pattern of a high selection ratio is formed.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a method for forming a resist pattern used in a lithography process in the manufacturing process of semiconductor devices, and in particular a method for forming a pattern by a silylation process. Regarding.

(Prior Art) As semiconductor technology progresses, semiconductor devices, and even semiconductor elements, are becoming faster and more integrated. Along with this, the precision of pattern miniaturization is becoming increasingly high, and pattern dimensions are also required to be highly accurate. In the current process, the underlying thin film is etched by RIE using a photosensitive polymer (resist) pattern as a mask, so the ring graphie technology forms a fine resist pattern with a high aspect ratio and high dimensional accuracy on the surface of an element with steps. This is required. In photophosphorography technology, it is difficult for the conventional single-layer process to fully meet these demands, and the significance of multi-layer resist processes has become increasingly important.

The multilayer resist method is intended to divide the roles assigned to the resist by forming multiple layers. First 2~
A resist layer with a thickness of 3 μm is provided to flatten the steps on the element surface and absorb reflected light from the underlying layer. If a pattern is formed on this with a high-resolution resist, the exposure phenomenon can be performed under ideal conditions separated from the underlying layer, and a pattern with high resolution and good dimensional accuracy can be formed.

This is the basic idea of multilayer resist, but the specific methods vary depending on the number of layers and the method of pattern transfer to the underlying layer. A typical multilayer process is a three-layer resist method in which an intermediate layer is provided between upper and lower resist layers. Pattern transfer from the upper layer to the intermediate layer and from the intermediate layer to the lower layer is performed by two-step glue active-on-etching (RIE, hereinafter abbreviated as RIE). Here, the intermediate layer plays two roles: preventing interaction between the upper and lower resist layers and providing withstand voltage to the lower resist RIE. Therefore, the most commonly used material for the intermediate layer is S or OoG (Spin On Glass: organic silicon glass), which can be formed into a film by a spin coating method.

Although this method is a fairly stable process compared to other techniques, the process is quite complicated, including two RIE steps, and is not suitable for practical use for mass production. Therefore, simplification of the process has become a major issue, and various processes are being considered. One promising technology is one that realizes the functions of the above-mentioned 13-layer resist, and can be said to be the ultimate and ideal resist process.

According to JP-A No. 61-107346, a typical silylation process involves applying a photosensitive resin layer to a base material, then exposing it to an exposure beam such as ultraviolet light through a mask to create an exposed area. A silylated layer is created by selectively absorbing a silicon compound in the exposed areas, and the non-exposed areas are selectively removed by reactive ion etching to obtain a desired negative pattern.

(Problem to be Solved by the Invention) As a result of intensive research by the present inventors, it has been found that in the silylation process, the difference in silylation between exposed and unexposed areas is greatly influenced by the set temperature, and as a result, the pattern It was found that there was a change in the selectivity of

An object of the present invention is to provide a pattern forming method that controls silylation and provides high pattern selectivity.

[Structure of the Invention] (Means for Solving the Problems) The present invention provides that when a polymer reaches a temperature equal to or higher than its glass transition point,
Utilizing the fact that the diffusion coefficient increases compared to the state at a temperature below the glass transition point, by setting the temperature of the silylation treatment above the glass transition point of the target part, silicon compounds can be selectively absorbed. An object of the present invention is to provide a method for forming a pattern with high precision.

(Function) In the present invention, the silylation treatment is carried out at a temperature above the glass transition point of the portion where the silicon compound is absorbed, and further at a temperature below the glass transition point of the portion where the silicon compound is not absorbed.

Before and after exposure, the photosensitive resin undergoes a change in interaction or a change in structure, which can be seen as a structural change in the photosensitive agent. On the other hand, heat treatment also causes interaction changes or structural changes. This change occurs when the polymer and the photoactive substance undergo a degeneracy reaction or interaction such as esterification during exposure and heating during the silylation process. Alternatively, it occurs when the polymer undergoes crosslinking or main chain scission during exposure and heating during silylation treatment. This effect works in the direction of changing the glass transition point. The diffusion coefficient at temperatures above the glass transition point increases compared to the diffusion coefficient below the glass transition point. Therefore, it is easier to absorb silicon compounds at temperatures above the glass transition point, compared to when the temperature is below the glass transition point. In the present invention, the difference between the glass transition point of the exposed area and the unexposed area is increased, and the silylation treatment is performed to prevent the absorption of silicon compounds beyond the glass transition point of the area intended for absorption of silicon compounds. By carrying out the process at a temperature below the glass transition point of the part to be absorbed, it is possible to absorb a silicon compound with a high selectivity, and it is possible to form a pattern with a high selectivity.

(Example) Example 1 The present invention will be described in detail below using Examples.

A photosensitive resin was prepared by dissolving 8 g of novolak resin and 2 g of a photosensitizer containing naphthoquinone diazide in 23 g of ethyl cellosolve acetate. The silicon wafer (1) was exposed in advance to an atmosphere of hexamethyldisilazane for 120 seconds to perform surface modification to improve adhesion, and then 35,007 pffl of the photosensitive resin (2) was applied to the silicon wafer.
The film was spin-coded to a thickness of μm and baked at 90° C. for 5 minutes (Figure 2). This wafer was exposed to the g-line (4) of a mercury lamp through a mask (3). (Figure 3) The glass transition point of the exposed area (5) of this resin was 123°C, and the glass transition point of the unexposed area (5') was 138°C. Next, this wafer was placed in a chamber, and after replacing the inside air with nitrogen, it was heated to 127°C in a hexamethyldisilazane atmosphere.
silylation (Fig. 4). After the chamber was brought to atmospheric pressure, the silylated wafer was taken out, oxygen gas was introduced into the vacuum container, a high-frequency electric discharge was generated between the parallel plate electrodes, the oxygen gas was turned into plasma, and the sample was placed on the negative side. When a dry phenomenon was carried out by performing reactive ion etching, the silylated portion changed to SiO2(7), and the non-silylated portion was etched to 0.
A 5 μm pattern was obtained with good precision (Fig. 1). Thereafter, the substrate was etched using the pattern as a mask.

Example 2 A pattern was formed by the method shown in Example 1 using a resist using polyvinylphenol as a resin and naphthoquinobox diazide as a photosensitizer, and a 0.5 μm pattern was obtained with high accuracy.

Example 3 A polymer was prepared by converting some of the hydrogen atoms in the methylene groups of polymethyl methacrylate into hydroxyl groups, and the polymer was spin-coded onto a silicon wafer to a thickness of 1 μm, and baked at 180° C. for 60 minutes. Next, at an acceleration voltage of 50KV, 50μ
When C7c& was subjected to electron beam exposure and pattern formation was performed by the method shown in Example 1 below, a 0.2 μm pattern was obtained with high accuracy.

That is, for example, when hydroxyethyl methacrylate H3-O0-CH2-CH20H is exposed to electron beams or far ultraviolet rays, the main chain is cut, the molecular weight decreases, and the glass transition point of the exposed portion decreases. Next, when exposed to the vapor of a silicon compound such as hexamethyldisilazane double HN (St (CH3)3)2 at a temperature above the glass transition point of the exposed area and below the glass transition point of the non-exposed area, the glass transition point is Since the diffusion rate of hexamethyldisilazane in the exposed areas with low light is higher than that in the non-exposed areas, hexamethyldisilazane penetrates into the polymer more quickly in the exposed areas. Then, ammonia gas NH3 as shown below is generated and silylated.

0-CH2-CH2-OH H3 On the other hand, silylation does not occur in the non-exposed areas.

Next, when dry development is performed using plasma using 02 gas, the Si coupled in the exposed area reacts with oxygen to form SiO2 on the surface, which interacts with the 02 plasma mask to expose the non-exposed area. Only the hydroxyethyl methacrylate is dry developed to form a highly accurate pattern.

As described above, the photosensitive resin may be a polymer mixed or bonded with a photoactive substance or a polymer alone. In addition, exposure to visible light, ultraviolet light,
Radiation such as X-rays, or charged particle beams such as electron beams and ion beams can be used.

Further, as the photosensitive resin, a material that causes crosslinking during heating during photosensitization and silylation treatment, such as a copolymer of chloromethylated styrene and polyvinylphenol, may be used as the photosensitive resin.

[Effect of the invention] As explained above, the silylation treatment is carried out at a temperature higher than the glass transition point of the part intended to absorb silicon compounds, and at a temperature higher than the glass transition point of the part intended not to absorb silicon compounds. By carrying out the process at a temperature below the temperature point, it becomes possible to absorb the silicon compound with a high selectivity, and it is possible to form a pattern with a high selectivity.

[Brief explanation of the drawing]

Figure 1, Figure 2, Figure 3, jf! FIG. 4 is a sectional view of an embodiment of the present invention. 1... Base material, 2... Photosensitive resin, 3... Mask,
4... Ultraviolet rays, 5... Exposure rays, 6... Silylation region, 7... 5i02 region

Claims (2)

[Claims] (1) A process in which a photosensitive resin layer coated on a base material is selectively exposed to light to change the glass transition point to make it different from the unexposed area, and between the glass transition points in the exposed area and the unexposed area. A step of absorbing a silicon compound into the exposed area at a temperature of
A pattern forming method characterized by obtaining a desired pattern. (2) The pattern forming method according to claim 1, wherein the polymer undergoes crosslinking or main chain scission during exposure or heating during silylation treatment, resulting in a change in glass transition point.