JPH10153868A - Pattern forming method for positive photoresist material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a photoresist pattern which has excellent performance such as profile, resolution and production of scum and which does not produce bubbles even when the resist film is made thick, by leaving the resist to stand for a while after exposure and before the post exposure baking process. SOLUTION: The resist film having >=3μm thickness is formed on a substrate by using a positive photoresist material having naphthoquinone diazide groups as photosensitive groups, and prebaked. Then the resist film is exposed, subjected to PEB and exposed. After the exposure and before the PEB process, the resist is left to stand at preferably 10 to 70 deg.C, especially 15 to 40 deg.C. By this method, production of bubbles in the succeeding PEB process can be suppressed. The resist is left to stand for preferably >=1min and <=48 hours, more preferably >=1min and <=24 hours, and further more preferably >=1min and <=12 hours. Thereby, a resist pattern profile with large thickness (>=3μm) can be formed with good reproducibility.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a positive photoresist material having a naphthoquinonediazide group as a photosensitive group, a resist film having a thickness of 3 .mu.m or more formed and prebaked, and after exposure, post exposure bake (Post exposure bake).
The present invention relates to a method for forming a pattern of a positive photoresist material to be subjected to Exposure Bake (PEB) and development, and particularly to a pattern forming method for preventing foaming in a PEB process.

[0002]

2. Description of the Related Art A positive photoresist material is usually composed of a novolak resin soluble in an alkaline solution and a radiation-sensitive compound containing a quinonediazide group called a photosensitizer.
When the quinonediazide group in the radiation-sensitive compound is decomposed by irradiation with light having a wavelength of 300 to 500 nm to generate a carboxyl group, the photoresist material changes from alkali-insoluble to alkali-soluble. Such a positive resist material has a feature that resolution is superior to that of a negative resist material.

However, when a positive photoresist material is used with a film thickness of 3 μm or more, there is a problem that the rectangularity of the profile is remarkably deteriorated due to the bubbling of nitrogen generated during exposure in the PEB process. This PEB step is an essential step in consideration of the occurrence of resolution, scum, etc., and the problem of foaming is important because a thicker film and a finer resolution, so-called high aspect ratio resist films are preferred. is there.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and when a positive type photoresist material having a naphthoquinonediazide group as a photosensitive group is used, foaming is caused even when the resist film thickness is increased. Profile
It is an object of the present invention to provide a pattern forming method for providing a photoresist pattern excellent in various performances such as resolution and generation of scum.

[0005]

Means for Solving the Problems and Embodiments of the Invention The present inventor has conducted intensive studies to achieve the above object, and as a result, a positive photoresist material having a naphthoquinonediazide group as a photosensitive group has been used for a silicon wafer or the like. Apply to the substrate,
A resist film is formed, which is pre-baked, exposed, and
When performing patterning by EB and further development, there is no particular problem if the resist film is thin.
When the resist film is formed thicker than the above, foaming occurs in the resist film.
In particular, when performing after-exposure (LAE), especially when the drawing is performed for 1 minute or more and 48 hours or less, the foaming phenomenon is suppressed, and all properties such as resolution, profile shape, and scum are excellent. It has been found that a pattern profile of a resist film having a large thickness (3 μm or more) can be manufactured with good reproducibility, and the present invention has been accomplished.

Accordingly, the present invention provides a method of forming a resist film having a thickness of 3 μm or more on a substrate using a positive photoresist material having a naphthoquinonediazide group as a photosensitive group, pre-baking, then exposing and post-exposure baking. A method of forming a pattern of a positive photoresist material, the method including a step of exposing; and performing the drawing after the exposure.

Hereinafter, the present invention will be described in more detail. The positive photoresist material of the present invention comprises an alkali-soluble resin and a quinonediazide ester compound as a photosensitizer as main components.

Here, examples of the alkali-soluble resin include a novolak resin, polyhydroxystyrene or a derivative thereof, and polyvinylphenol. Specific examples of the novolak resin include phenol, o-cresol, m-cresol, p-cresol, o-ethylphenol, m-ethylphenol, p-ethylphenol, 2,3-xylenol, 2,4-xylenol,
2,5-xylenol, 3,4-xylenol, 3,5
-Xylenol, 2,3,5-trimethylphenol,
p-phenylphenol, hydroquinone, catechol,
Resorcinol, 2-methylresorcinol, pyrogallol, 4-tert-butylphenol, 2-tert
-Butylphenol, 3-tert-butylphenol, α-naphthol, β-naphthol, bisphenol A, o-nitrophenol, m-nitrophenol, p
-A resin obtained by using one kind of phenols such as nitrophenol alone or in combination of two or more kinds and polycondensing the phenols with aldehydes by an ordinary method is preferably used. The weight average molecular weight of the alkali-soluble resin is usually 1,000 to 40,000, particularly 1,500 to 40,000 in terms of polystyrene.
A range of 20,000 is preferred.

As the photosensitive agent, for example, esters of naphthoquinonediazide compounds such as 1,2-naphthoquinonediazide-4-sulfonic acid ester and 1,2-naphthoquinonediazide-5-sulfonic acid ester can be used. As the core of the photosensitive agent, an alkali-soluble resin such as the above novolak resin is used, and a naphthoquinonediazide group is directly introduced into a part or all of its hydroxyl groups, or a naphtho group is used as a phenol compound as exemplified below. It is preferred to use those having a quinonediazide group introduced.

[0010]

Embedded image

In the resist composition of the present invention, the ratio of the naphthoquinonediazide group to 100 parts by weight of the alkali-soluble resin is preferably 5 to 50% by weight, more preferably 5 to 30% by weight.

The resist material of the present invention may optionally contain a phenol compound represented by the following general formula (1).

[0013]

Embedded image (Wherein, X ^{1 to} X ⁵ are each a hydrogen atom, an alkyl group or a hydroxyl group, and at least one is a hydroxyl group. R ^{1 to} R ³ are each a hydrogen atom, an alkyl group or a substituted or unsubstituted group. An aryl group, at least one of which is a substituted or unsubstituted aryl group.)

In the above formula (1), X ^{1 to} X ⁵ are:
For example, a hydrogen atom, a methyl group, an ethyl group, a butyl group and the like, preferably an alkyl group having 1 to 4 carbon atoms or a hydroxyl group, etc., and at least one is a hydroxyl group. R ^{1 to} R ³ are each a hydrogen atom, preferably an alkyl group having 1 to 4 carbon atoms;
A phenyl group, a tolyl group, a naphthyl group, or the like, or a substituted or unsubstituted aryl group having preferably 6 to 12 carbon atoms, in which a part of the hydrogen atoms of these groups is substituted with a hydroxyl group, a methyl group, an amide group, a carboxyl group, or the like. is there.

Specific examples of such a phenol compound of the above formula (1) include the following compounds.

[0016]

Embedded image

The phenol compounds of the above formula (1) can be used singly or as a mixture of two or more.

The amount of the phenol compound of the formula (1) is from 0 to 45% by weight of the alkali-soluble resin, especially from 0 to 45% by weight.
Preferably it is 30% by weight. If the content exceeds 45% by weight, microgrooves may be generated, resolution may be reduced, heat resistance may be reduced, and the like.

The positive photoresist material of the present invention includes:
It is desirable to use a solvent. Examples of the solvent include ketones such as methyl ethyl ketone, 4-ethoxy-2-
Ketoethers such as butanone, alcohol ethers such as ethylene glycol monomethyl ether, ethers such as dioxane, cellosolve esters such as methyl cellosolve acetate and ethyl cellosolve acetate, carboxylic acid esters such as ethyl lactate and butyl acetate, dimethylformamide and the like Are preferred, and one of these can be added alone or as a mixture of two or more.

The amount of the solvent used is not particularly limited as long as the film can be formed so as not to cause holes, striations, uneven coating, etc., but the solid content concentration of the alkali-soluble resin and the quinonediazide compound is 10 to 60% by weight. Especially 20-50
It is preferable to use it within the range of weight%.

Further, in addition to the above components, the resist composition of the present invention may further comprise, as other optional components, nonionic surfactants such as polyoxyethylene alkyl ethers and polyoxyethylene alkyl phenyl ethers for improving coating properties. , Various surfactants such as fluorine-based surfactants,
A sensitizer for improving the sensitivity to radiation, a dye or pigment for making the formed image more visible, an adhesion aid for improving the adhesiveness, a storage stabilizer and the like can be added.
In addition, the addition amount of these optional components can be a usual amount as long as the effect of the present invention is not hindered.

According to the pattern forming method of the present invention, a resist film is formed on a substrate such as a silicon wafer by using the above positive photoresist material. In this case, as a method of applying the resist material, a known method such as spin coating can be adopted.

Here, the thickness of the resist film is 3 μm or more,
Preferably 3 to 20 μm, more preferably 3 to 15 μm
And If the thickness is less than 3 μm, the nitrogen generated by the exposure escapes immediately, so that it is not necessary to perform the LAE. When the thickness is more than 20 μm, disadvantages such as poor uniformity of the coating film occur.

Next, the resist film can be pre-baked according to a conventional method. The conditions are appropriately selected, but are preferably from 60 to 130 ° C. for 30 to 300 seconds, particularly from 70 to 12 ° C.
It is preferable that the conditions are 0 ° C. and 50 to 250 seconds.

After prebaking in this manner, exposure is performed according to a conventional method. In this case, the wavelength, exposure dose, and the like are appropriately selected, but the resist material is sensitive to radiation such as ultraviolet rays, far ultraviolet rays (including excimer lasers, etc.), electron beams, ion beams, and X-rays, and is usually 300 to 500 nm. Of light. The smaller the exposure, the better the throughput is. From the viewpoint of throughput, the optimum exposure for each resist varies depending on the process conditions such as baking conditions and the developing method, but is usually preferably 100 to 1000 mJ / cm ² .

Here, when a quinonediazide ester compound is used as a photosensitive group, nitrogen is generated when the resist film is exposed. This nitrogen is a cause of foaming during PEB, and when the resist film is formed with a thickness of 3 μm or more, P
If a certain amount of nitrogen has not been removed before EB, nitrogen is suddenly generated by heating, so that the formed pattern is distorted.

Therefore, in the present invention, after the above exposure,
Before the PEB step, preferably 10 to 70 ° C, especially 15 to 70 ° C.
Leave the exposed resist film at 40 ° C (LAE)
This suppresses foaming in the PEB in the next step.

The post-exposure (LAE) time before PEB differs depending on the thickness of the resist, the conditions of pre-bake / PEB, the type of the resist solvent, and the resist material.
More effect will be obtained by leaving at least 1 minute or more. The method comprises a naphthoquinonediazide group,
Conditions under which nitrogen generated from the applied resist film is difficult to escape (for example, a thick film; nitrogen generated depending on the type of solvent is easily dissolved in the residual solvent; PEB temperature is high;
Under such conditions that the solvent remaining on the surface of the resist film evaporates due to rapid heating and only the surface is hardened, the effect is always exerted. However, the minimum required LAE time differs depending on the ease with which the generated nitrogen escapes from the resist film.
Although a more preferable LAE time cannot be limited, when the holding time (LAE) is longer than 48 hours, the probability of deterioration of the applied resist film and a change in pattern dimension based on the deterioration is increased. Time is 48
It is preferable to be within hours. In addition, the minimum required LA
E time is most affected by film thickness. For example,
If the minimum LAE time is 1 minute at 6 μm, 1 at 10 μm
5 minutes, 30 minutes at 15 μm, and a longer LAE time is required as the thickness increases. This relationship depends on the process conditions.

Therefore, the LAE time is preferably from 1 minute to 48 hours, more preferably from 1 minute to 24 hours.
The time is within 1 hour, more preferably 1 minute or more and 12 hours or less.

After the LAE step, a PEB step is performed according to a conventional method. This PEB condition is also appropriately selected and usually performed under the same or higher conditions as the pre-bake condition.
To 140 ° C, 30 to 300 seconds, especially 70 to 130 ° C, 5
It is preferably 0 to 250 seconds in terms of pattern formation, scum, resolution, dimensional controllability, adhesion and the like.

After the PEB step, development is carried out by an ordinary method using an aqueous alkali solution such as tetramethylammonium hydroxide.

The pattern obtained by the above method has no foaming, has excellent characteristics such as resolution, profile shape and scum, and can form a thick (3 μm or more) resist pattern profile with good reproducibility. It is.

[0033]

According to the method for forming a pattern of a positive photoresist material of the present invention, foaming during PEB does not occur.
A resist pattern excellent in various performances such as a resist pattern profile, scum, and resolving power can be obtained.
It is suitable for producing an integrated circuit.

[0034]

EXAMPLES The present invention will be described in detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

Examples and Comparative Examples 1,2-Naphthoquinonediazidochloride was reacted with a phenol novolak resin having a weight average molecular weight shown in Table 1 according to a conventional method.
A part of the hydroxyl group of the novolak resin was esterified with a 1,2-naphthoquinonediazide group (NQD group). On this occasion,
The content of the NQD group was adjusted to the ratio shown in Table 1. This was dissolved in a solvent shown in Table 1 so as to have a solid content of 30 to 50% by weight, and filtered using a microfilter having a pore size of 0.1 μm. 1-5 photoresist materials were prepared.

A tetranuclear p-cresol is reacted with 1,2-naphthoquinonediazidochloride to partially esterify the hydroxyl group, and the resulting ester and phenol novolak resin are reacted with a novolak resin by a photosensitive group. Used in such a manner that the content of a certain NQD group is as shown in Table 1, dissolved in a solvent shown in Table 1 so as to have a solid content concentration of 30 to 50% by weight, and filtered using a micro filter having a pore size of 0.1 μm. No. 6-9 photoresist materials were prepared.

[0037]

[Table 1] EL: Ethyl lactate BA: Butyl acetate ECA: Ethyl cellosolve acetate

Next, the obtained photoresist material was spin-coated on a silicon wafer vapor-treated with hexamethyldisilazane using an auto coater, followed by pre-baking to obtain a film having a thickness of 6 to 15 μm. This resist-coated wafer is subjected to a reduction projection exposure apparatus (Nikon Corporation, NSR 1
755i7A), and exposed through a mask pattern. Thereafter, after leaving for 0 to 72 hours, post-exposure bake (PEB), develop with a 2.38% aqueous solution of tetramethylammonium hydroxide for 50 seconds × 4 times, wash with water and dry (by an auto developer) A resist pattern was obtained.

Table 2 shows the process conditions (resist film thickness, pre-bake (PB) temperature and time, PEB temperature and time, and holding time).

[0040]

[Table 2]

The obtained resist pattern was observed with a scanning electron microscope, and the presence or absence of foaming, the presence or absence of scum, the resolution, and the dimensional controllability were evaluated. The results are shown in Tables 3 to 6. Sensitivity: The exposure amount when the line and space image dimensions of the mask pattern and the resist pattern reproduce 1: 1 (± 10% tolerance) was defined as the sensitivity. Resolution: The minimum dimension at the above exposure amount was displayed.

[0042]

[Table 3]

[0043]

[Table 4]

[0044]

[Table 5]

[0045]

[Table 6]

FIGS. 1 and 2 show the results of the presence / absence of bubbling of the resist film when the bubbling and leaving time and the resist film thickness are changed. From this result, it was found that foaming did not occur under the process conditions on the right side of the line in FIG. That is,
It was recognized that the longer the film thickness, the longer the time required for the withdrawal.

From the results shown in Table 4, it was found that this method of carrying out the retention was effective for foaming regardless of the type of the photosensitive agent and the content of the NQD group in the resist.

As can be seen from Table 5, the resist material which could not be subjected to PEB because of the problem of foaming can now be subjected to PEB by using this method of depositing, so that the resolving power is improved, It can be seen that the scum has also disappeared.

When the pre-baking, PEB, and film thickness are set to the conditions shown in Table 6, the line width of the pattern tends to be narrow when the laying time is long, and there is a problem in dimensional controllability when the time exceeds 48 hours. Is recognized. However, when the conditions of the baking and the film thickness are changed, the dimensional controllability tends to decrease when the laying time is too long, though not necessarily the same tendency as the example.

From these results, it was confirmed that the method for forming a pattern of a positive photoresist material of the present invention gave a resist pattern excellent in pattern profile, scum, and resolution by performing proper withdrawal.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the presence / absence of bubbling of a resist film, a withdrawal time, and a resist film thickness.

FIG. 2 is a partially enlarged view of the graph.

Claims (2)

[Claims] 1. A step of forming a resist film having a thickness of 3 μm or more on a substrate using a positive photoresist material having a naphthoquinonediazide group as a photosensitive group, pre-baking, exposing, post-exposure baking, and exposing. A method of forming a pattern of a positive type photoresist material, comprising: performing the drawing after the exposure. 2. The pattern forming method according to claim 1, wherein the leaving time is 1 minute to 48 hours.