JPH04221814A - Pattern forming method - Google Patents

Abstract

PURPOSE:To put a high-sensitivity resist to practical use by preventing the variation of the resolution characteristic, such as sensitivity, etc., of the resist caused by the variation of the period the resist is left as it is after application and, at the same time, easily preventing the resist from reflecting light. CONSTITUTION:In the course of a pattern forming method which patterns a resist film of a chemically amplified resist, etc., formed on a substrate to be worked of semiconductor wafer, etc., the characteristic variation of the resist is prevented by forming a water-soluble high polymer film on the resist film or keeping the surface of the substrate to be worked in the atmosphere of <=40% in relative humidity until the exposure or development is performed after the resist film is formed.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pattern forming method, and more particularly to a pattern forming method in which a resist film is formed on a substrate to be processed and patterned. The present invention can be used as a pattern forming method in various fields, for example,
It can be applied to pattern forming materials in the electronic field (semiconductor device manufacturing field, etc.).

0002

BACKGROUND OF THE INVENTION Pattern formation in various fields is becoming increasingly finer. For example, the minimum processing dimensions of semiconductor integrated circuits are becoming finer year by year, and at the research and development level, they have reached the level of, for example, 0.35 μm, which is less than 0.5 μm. Along with this, it has become necessary to control fine dimensions with high precision even in the photolithography process. For this reason, attempts have been made to shorten the exposure wavelength. That is, if the exposure wavelength is shortened,
This is because the marginal resolution improves accordingly. Under these circumstances, KrF excimer laser lithography technology, which uses even shorter wavelengths, is attracting attention from conventional lithography technology that uses ultraviolet rays (wavelengths of 435 nm and 365 nm) such as G-line and I-line emitted from high-pressure mercury lamps. There is. This is because the KrF excimer laser has a short oscillation wavelength (25
0 nm), high resolution is expected.

[0003] Generally, it is desired that a resist used for pattern formation be highly sensitive, but a resist with particularly high sensitivity is required in the short wavelength region as described above. For this reason, a resist composition with higher sensitivity than before is required, and in this background, so-called chemically amplified resists, for example, are attracting attention. A chemically amplified resist is a resist in which a substance generated by light contributes to some kind of next reaction, such as initiating or promoting the next reaction such as polymerization. Such a chemically amplified resist has the advantage of providing high resolution and good resist shape.

[0004] Chemically amplified resists generally have a structure in which reactive substances such as acids and alkalis are generated by light, and the reactive substances cause crosslinking reactions and other reactions. For example, a so-called photoacid generator that generates an acid when exposed to light is typically used, and in the case of negative resists, the generated acid generally causes a crosslinking reaction and reduces the solubility of the area in the solvent (developer). In the case of positive resists, the generated acid generally acts to remove the protective groups of the resin and increase its solubility. Therefore, a negative chemically amplified resist usually consists of a three-component system of a base resin, a photoacid generator, and an acid crosslinking agent whose crosslinking progresses with acid. Alternatively, a functional group can be introduced into the base resin so that it can function as either of the other two components. In addition, positive chemically amplified resists usually consist of two essential components: a base resin and a photoacid generator. However, the base resin has a protective group introduced into it, or a compound that has a separate protective effect. , usually contains an acid-decomposed dissolution inhibitor that suppresses solubility. Among the above-mentioned positive-type chemically amplified resists, those containing a dissolution inhibiting agent are designed so that the acid generated by light cancels the dissolution inhibiting effect, and the areas irradiated with light can be dissolved by the solvent (developer). This is what I did.

However, high-sensitivity resists, such as chemically amplified resists, have a drawback in that their sensitivity changes depending on the time they are left standing from application to exposure.

On the other hand, for example, KrF excimer laser lithography technology is susceptible to reflection from the substrate when the substrate to be processed is a semiconductor substrate, so anti-reflection is required. Examples of anti-reflection technology include g
In line and i-line lithography techniques, a method called ARCOR method in which the surface of a resist is coated with an antireflection film is known. (Tanaka et al. “Proposal of ARCOR method for optical lithography” Proceedings of the 32nd Applied Physics Association Conference 29a-H-3 (293 pages), 19
Spring of 1985. "Proposal of ARCOR method for optical lithography (2)" Proceedings of the 46th Applied Physics Academic Conference, page 3
-9-5 (316 pages), Fall 1960). The excimer laser reroughing technique may also be applied, but there are problems in that the process is complicated, such as the need for peeling, and it has not always been suitable for application.

[0007]

[Problems to be Solved by the Invention] As mentioned above, in the prior art, high-sensitivity resists such as chemically amplified resists have the first problem that the sensitivity changes depending on the situation. Second, even if anti-reflection measures are attempted, there is a problem in that no appropriate measures are necessarily available, and this is a bottleneck in using highly sensitive resists for pattern formation.

Each of the inventions of the present application attempts to solve the above-mentioned problems, and by solving the first problem, each invention makes it possible to practically effectively perform pattern formation using a high-sensitivity resist. In particular, the invention of claim 1 can be configured to solve the second problem as well.

[0009]

[Means for solving the problem] The invention of claim 1 of the present application provides a pattern forming method in which a resist film is formed on a substrate to be processed and patterned, in which a water-soluble polymer film is formed on the resist film. This is a pattern forming method characterized in that patterning is carried out by performing patterning, thereby achieving the above object.

The invention according to claim 2 of the present application is a pattern forming method in which a resist film is formed on a substrate to be processed and then patterned. This is a pattern forming method characterized in that the pattern is formed in an atmosphere with a relative humidity of 40% or less, thereby achieving the above object.

In each invention, any resist material can be used to form the resist film. The present invention is particularly effective for pattern forming methods using highly sensitive resists, such as chemically amplified resists.

In the first aspect of the invention, various water-soluble polymer materials can be used as the material for the water-soluble polymer film formed on the resist film. In terms of the manufacturing process, it is preferable to use a polymeric material that can be formed into a film by spin coating on a substrate to be processed on which a resist film has been formed. Preferred water-soluble polymers are typically PVA (polyvinyl alcohol) and PVP (polyvinylpyrrolidone).
, polysaccharides (pullulan, cellulose, etc.), polyvinyl acetals, and styrene sulfonic acid compounds (for example, polystyrene sulfonate salts such as ammonium polystyrene sulfonate). can. PVA is desirable from the viewpoint of effectively shielding the resist film from the atmosphere.

In the invention of claim 1, the thickness of the water-soluble polymer film is determined by the refraction of the water-soluble polymer material at the wavelength of the exposure light used (for example, KrF excimer laser oscillation wavelength or ArF excimer laser oscillation wavelength). The film thickness can be set to meet the antireflection condition determined by the ratio.

[0014]

[Operation] According to the invention of claim 1, the resolution performance changes depending on the standing time from resist application to exposure or development.
In particular, sensitivity changes can be prevented. The effect of this invention is not necessarily clear. The present inventor presumes that changes in resolution performance, especially sensitivity fluctuations, due to variations in standing time are mainly due to the effects of contact of the resist with the atmosphere, probably due to the effects of oxygen and humidity. We thought that this problem could be solved by configuring it to cut off the contact with the resist, and after conducting various studies based on this point of view, we discovered that the problem could be solved by this invention, and completed the invention. That's what I came to do.

Further, the invention of claim 1 can be configured such that the thickness of the water-soluble polymer film is set to an anti-reflection condition determined by the refractive index of the material at the exposure wavelength used. It becomes possible to easily achieve antireflection without requiring the trouble of peeling off the upper layer, which is required in the method.

Therefore, the invention of claim 1 has the basic effect of being able to prevent fluctuations in resolution performance such as sensitivity, and thereby realizing good pattern formation without fluctuations in width, etc. of the finally formed pattern. have an effect.

[0017] Moreover, the invention of claim 1 can provide an effective anti-reflection effect more easily than the prior art by forming a water-soluble polymer film with a film thickness that satisfies the anti-reflection conditions.
Such anti-reflection also enables more stable pattern formation.

According to the second aspect of the invention, by leaving the substrate to be processed on which the resist film is formed in an atmosphere with a relative humidity of 40% or less, the resolution performance changes depending on the standing time from resist application to exposure or development. In particular, changes in sensitivity can be prevented. According to the present invention, by holding the substrate to be processed in a low-humidity atmosphere after resist coating, it is believed that changes in sensitivity and the like are suppressed. Therefore, according to the present invention, it is possible to prevent changes in sensitivity, etc., and to perform stable pattern formation that prevents pattern fluctuations.

[0019]

[Examples] Examples of each invention of the present application will be described below. However, it goes without saying that each invention is not limited to the examples described below.

Example 1 This example embodies the invention of claim 1.
In particular, when forming miniaturized and integrated semiconductor integrated circuit devices, the present invention is applicable when patterning is performed by forming a resist film using a chemically amplified resist, which is a highly sensitive resist, on a semiconductor substrate, which is a substrate to be processed. This is an example of application.

In this example, a film was formed by coating a chemically amplified resist and then spin-coating a water-soluble polymer material with an aqueous solvent.

As described above, various types of water-soluble polymer materials can be used, but PVA was used here. This is because PVA is suitable for carrying out the present invention because its molecules are easily aligned and its air permeability is low. More specifically, PV
As A, Nagase Sangyo Co., Ltd.'s product name Barrier Coat BC5
was used. In this example, KrF excimer laser light (wavelength 248 nm) is used as exposure light, so this PV
This is because A is preferred for this wavelength.

The implementation conditions were a KrF excimer stepper (N
A: 0.37) and chemically amplified S as a resist.
0.7 using AL601 ER7 (Shipley)
A resist film with a thickness of μm was formed, and a water-soluble polymer film was formed using the PVA described above to coat the resist film, and the resist film was exposed using the stepper described above.

Pre-baking before exposure was carried out at 90°C for 90 seconds, and baking after exposure (PEB) was carried out at 110°C for 90 seconds. Development was carried out for 10 minutes using MF622, a developer exclusively used for the resist used.

The following four experiments were conducted under the above conditions. That is, in both the first and second experiments (comparative experiments), no PVA film, which is a water-soluble polymer film, was formed. For the second time, a line and space pattern of 0.4 μm was formed for 80 minutes, and the width of the formed pattern was examined. The third and fourth experiments embody this invention, and in both cases, a PVA membrane was formed as a water-soluble polymer membrane (
The film thickness was set to provide the optimum anti-reflection condition by taking into account the refractive index of this PVA material with respect to KrF excimer laser light). A line and space pattern of 0.4 μm was formed for 80 minutes, and the width of the formed pattern was examined. The exposure dose was 60 mJ/cm 2 in both cases. The results are shown in the table below. Margin below

[Table 1]

As can be understood from the results in Table 1, Experiment N embodying the method of the present invention formed a water-soluble polymer film.
o. In cases 3 and 4, there was almost no change in the pattern width when the leaving time was set to 10 minutes or 80 minutes.
Therefore, it can be seen that pattern fluctuations due to the standing time are suppressed. On the other hand, comparative experiment No. In No. 1 and No. 2, the change in pattern width was large due to the change in the standing time. In addition, in this example, an antireflection effect could also be effectively obtained.

Example 2 This example embodies the invention of claim 2,
As in Example 1, when patterning is performed by forming a resist film using a chemically amplified resist, which is a highly sensitive resist, on a semiconductor substrate, which is a substrate to be processed, especially in forming a miniaturized and integrated semiconductor integrated circuit device. This is an example in which the present invention is applied to.

Specifically, the experiment was carried out under the following conditions. That is, as a semiconductor substrate to be processed, a 5-inch silicon wafer that had been dehydrated and baked at 200°C for 1 minute and then hydrophobized with hexamethyldisilazane vapor for 1 minute was treated with SAL601ER.
7 (chemically amplified resist manufactured by Shipley) was spin-coated and baked at 90° C. for 90 seconds to form a resist film with a thickness of 0.7 μm. This was stored under various conditions (Experiment Nos. (1) to (10)) listed in Table 2 below, and then exposed to light to form a 0.45 μm contact hole. The dimensions of the contact holes obtained in each experiment were measured at the same dose. The development conditions are developer MF-622 and 10
It was developed for 1 minute. The dose was 70 mJ/cm2, and the post-exposure bake (PEB) was performed at 110°C for 60 seconds. The results are shown in Table 2 below. Margin below

[Table 2]

As can be understood from Table 2, if the present invention is applied and the pattern is kept in an atmosphere with a relative humidity of 40% or less, there will be no problem with pattern dimension fluctuation even if it is stored for one day (24 hours). I understand.

[0030] Separately, a similar experiment was conducted using XP-8843 (Shipley Co., Ltd.) as a resist under exactly the same conditions as in this example, and similar effects were obtained.

[0031]

[Effects of the Invention] As mentioned above, according to each invention of the present application,
It is possible to solve the problem that resolution characteristics such as sensitivity fluctuate due to changes in circumstances, for example, changes in time from resist coating to exposure or development. Moreover, the invention of claim 1 can be easily configured to have an anti-reflection function to further suppress pattern fluctuations.

Claims (2)

[Claims] 1. A pattern forming method in which patterning is performed by forming a resist film on a substrate to be processed, the method comprising forming a water-soluble polymer film on the resist film and performing patterning. 2. In a pattern forming method in which a resist film is formed on a substrate to be processed and patterned, the substrate to be processed is placed in an atmosphere with a relative humidity of 40% or less after the resist film is formed and before exposure or development. A pattern forming method characterized by: