JP3026462B2 - Pattern formation method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

 [Object of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a pattern using a photosensitive composition which is sensitive to energy rays such as light, EB and X-ray.

[0002]

2. Description of the Related Art In the process of manufacturing a semiconductor device such as an LSI,
A microfabrication technique by photo etching is employed. In this technique, a photoresist film is formed on a substrate such as a silicon single crystal wafer by a spin coating method or the like, and after exposing the photoresist film, a process such as development and rinsing is performed to form a desired resist pattern. I do. Then, the exposed substrate is etched using the resist pattern as an etching mask to form fine-width lines and windows.

As a photoresist material used for forming the above-mentioned pattern, a photosensitive composition comprising an alkali-soluble resin such as a novolak resin and a naphthoquinonediazide compound as a photosensitive agent is widely known.

In the manufacture of such LSIs, finer processing techniques are required with the recent high integration of LSIs. In response to such demands, it is necessary to form a fine and good-shaped pattern for a resist pattern used as an etching mask as described above, and development of a process capable of forming such a pattern with high reliability has been required. It is currently being actively conducted.

For example, Watt et al. Report the effect of using a photosensitive composition comprising a novolak resin and a polyfunctional naphthoquinonediazide compound as a photoresist material and performing a heat treatment after exposing the photoresist film. (SPIE Vol. 631 Advanc
es in Resist Technology
d Processing III (1986);
260-266). That is, in such a pattern forming method, after forming and exposing a photoresist film on a substrate, by performing the above-described heat treatment and developing, the resolution at the time of forming a resist pattern is improved,
The adhesion between the substrate and the photoresist film is improved. However, the above-described pattern forming method has a problem that it is not practical because the sensitivity of the photosensitive composition is reduced by performing the above-described heat treatment.

[0006]

As described above, the conventional pattern forming method having a heat treatment step has a problem that the sensitivity of the photosensitive composition is reduced.

An object of the present invention is to solve such a problem and to provide a pattern forming method capable of forming a highly reliable resist pattern with excellent sensitivity and good resolution. [Configuration of the Invention]

[0008]

Means and operation for solving the problems] The present invention includes the steps of forming a photosensitive layer mainly composed of alkali-soluble resin and a photosensitive agent on the substrate, a step of exposing a desired area of the photosensitive layer, wherein a step of performing heat treatment on the photosensitive layer after exposure,
Developing the photosensitive layer after the heat treatment, wherein the alkali-soluble resin is
A polyamic acid, wherein a monofunctional naphthoquinonediazide compound represented by the following general formula [1] is used as the photosensitive agent. That is, the pattern forming method of the present invention contains polyamic acid as an alkali-soluble resin.
A photosensitive composition containing a monofunctional naphthoquinonediazide compound represented by the following general formula [1] is used as a photosensitive agent, and after exposing a photosensitive layer formed by such a photosensitive composition, It is characterized by performing heat treatment.

[0009]

Embedded image

(Wherein R _{1 to} R ₄ may be the same or different and each represents hydrogen, an unsubstituted or substituted alkyl group having 1 to 6 carbon atoms, a halogen element, an alkoxy group, a cyano group, Represents a nitro group, a carbonyl group or an aryl group, and R ₅ is a monovalent organic group.)

The present inventors have conducted research on the reason why the sensitivity of a photosensitive composition using a novolak resin is reduced by performing heat treatment after exposure of a photosensitive layer. It was found that the polyfunctional naphthoquinonediazide compound used as the above causes a crosslinking reaction during the heat treatment. Therefore, when a monofunctional naphthoquinonediazide compound is used as a photosensitizer, such a crosslinking reaction does not occur, and in the pattern forming method of the present invention, the sensitivity of the photosensitive composition decreases even when the above-described heat treatment is performed. Is suppressed. In general, when a monofunctional naphthoquinonediazide compound is used, the resolution is lower than when a polyfunctional naphthoquinonediazide compound is used. However, as a result of further study by the present inventors, 1 represented by the above general formula [1] is obtained.
It has been found that when a functional naphthoquinonediazide compound is used as a photosensitizer, a resist pattern can be formed with a sufficient resolution. Therefore, in the present invention, by using the above-mentioned specific naphthoquinonediazide compound as a photosensitizer, a resist pattern can be formed with good sensitivity and resolution even if a heat treatment is performed after forming and exposing a photosensitive layer.

Polyamic acid is used as the alkali-soluble resin used in the present invention . Also mixed with this
As a resin to be used, a carboxyl group or phenolic water
Desirably, a polymer having an acid group, specifically, phenol
Novolak resin, cresol novolak resin, xyreso
Lunovolak resin, vinylphenol resin, isopro
Phenylphenol resin, vinylphenol and acrylic
Acid, methacrylic acid derivative, acrylonitrile, styrene
Copolymers with derivatives, isopropenylphenol and
Acrylic acid, methacrylic acid derivative, acrylonitrile,
Copolymer with styrene derivative, acrylic resin, meta
Krill resin, acrylic acid or methacrylic acid and acrylonitrile
Tolyl, copolymer with styrene derivative, malonic acid and vinyl
Copolymers with thiol ethers, or these copolymers
Examples include those containing silicon. As further described above
Carboxyl groups or phenolic hydroxyl groups of
Protected by degradable or hydrolysable protecting groups, e.g.
For example, alkyl ether, allyl ether, benzyl ether
Ter, triaryl methyl ether, trialkyl silyl
Ether, tetrahydropyranyl ether, acetater
, Ketal, acetate, formate, substituted acetic acid
Ester, substituted benzoic acid ester, tiglic acid ester
, Carbonate, succinate, 3-benzoyl
Propionate, 1-adamantanecarboxylic acid
Stele, 3-phenylpropionate, benzyl
Oxycarbonyl derivative, benzenesulfonic acid ester
It may be.

The photosensitive agent used in the present invention is a monofunctional naphthoquinonediazide having one 1,2-naphthoquinonediazide-4-sulfonic acid group in a molecule represented by the above general formula [1]. Compound. Note that the above 1,2-
The naphthoquinonediazide-4-sulfonic acid group includes an unsubstituted or substituted alkyl group having 1 to 6 carbon atoms at the 5 to 8 position of the basic skeleton, a halogen element, an alkoxy group, a cyano group, a nitro group, a carbonyl group, an aryl group, and the like. May be introduced. Specifically, such naphthoquinonediazide compounds include:

[0014]

Embedded image

[0015]

Embedded image And the like.

The naphthoquinonediazide compound as described above can be easily obtained by reacting naphthoquinonediazidesulfonic acid chloride represented by the following structural formula with alcohols and phenols, followed by dehydrochlorination. be able to.

[0017]

Embedded image

In the present invention, the amount of the naphthoquinonediazide compound is preferably 1 to 50 parts by weight, more preferably 5 to 40 parts by weight, based on 100 parts by weight of the alkali-soluble resin. If the amount of the naphthoquinonediazide compound is too large, the photosensitive layer may be subjected to a heat treatment after exposure to cause a decrease in the sensitivity of the photosensitive layer, foaming or the like.
Conversely, if the blending amount of the naphthoquinonediazide compound is too small, the photosensitivity of the photosensitive layer is reduced, and the pattern forming ability is deteriorated. In the present invention, the alkali-soluble resin and the naphthoquinonediazide compound are usually methyl ethyl ketone, cyclohexane, acetate cellosolve,
It is used by dissolving in an organic solvent such as N, N-dimethylformamide, N-methyl-2-pyrrolidone, hexamethylphosphamide. Next, each step of the pattern forming method of the present invention will be described in detail.

First, the above-mentioned alkali-soluble resin and naphthoquinonediazide compound are dissolved in the above-mentioned organic solvent, and if necessary, fine impurities are removed by a method such as filtration to prepare a resist solution. Next, the resist solution is applied on a predetermined substrate by, for example, a spin coating method, and then dried to form a photosensitive layer according to the present invention. In the present invention, a silicon substrate doped with impurities, a semiconductor substrate provided with a conductive film such as a polycrystalline silicon film via a silicon oxide layer on the silicon substrate, a blank mask, or the like may be used as the substrate. .

Next, visible light, infrared light, ultraviolet light, EB and X are applied to the photosensitive layer through a photomask having a desired pattern.
A desired area of the photosensitive layer is exposed by irradiating an energy ray such as a ray. At this time, both exposure methods of contact and projection are possible.

Subsequently, the photosensitive layer is subjected to a heat treatment at a temperature of 100 to 170 ° C. using a hot plate, for example, and then left to cool. At this time, if the temperature of the heat treatment is too low, the resolution of the obtained pattern will be insufficient. Conversely, if the temperature of the heat treatment is too high, the solubility of the photosensitive layer in an alkaline solution will decrease, making development difficult. A more preferable heat treatment temperature is 140 to 160 ° C. The time of the heat treatment depends on the heat treatment temperature, but is usually about 0.5 to 60 minutes,
More preferably, about 1 to 5 minutes is desirable. If the heat treatment time is too short, the resolution of the resulting pattern will be insufficient, and if the heat treatment time is too long, development of the photosensitive layer will be difficult.

Thereafter, the heat-treated photosensitive layer is developed using an alkaline solution. At this time, the exposed or unexposed portions of the photosensitive layer are dissolved and removed, and a desired positive or negative pattern is formed. As the alkali solution, an organic alkali aqueous solution such as a tetramethylammonium hydroxide aqueous solution or an inorganic alkali aqueous solution such as potassium hydroxide or sodium hydroxide can be used. The development is performed by an immersion method, a spray development method, or the like.

In the pattern forming method of the present invention as described above, both the sensitivity and the resolution are good, and the obtained resist pattern has excellent adhesion to the substrate, and is obtained by PEP (Photo Engraving Pro).
ess), it has high reliability as an etching mask.

[0024]

The present invention will be described below in detail with reference to examples. Example 1

First, 0.7 mol of pyromellitic dianhydride, 0.3 mol of 3,3 ', 4,4'-benzophenonetetracarboxylic dianhydride, 0.9 mol of 4,4'-diaminodiphenyl ether and Bis (γ-aminopropyl)
0.1 mol of tetramethyldisiloxane is added to N-methyl-2.
-Dissolved in pyrrolidone and reacted at 0 ° C in a nitrogen atmosphere to synthesize polyamic acid as an alkali-soluble resin. The logarithmic viscosity of this polyamic acid / N-methyl-2-pyrrolidone mixture was measured at 30 ° C., and it was 0.65 dl / g.

Next, 100 parts by weight of the alkali-soluble resin (P-1) thus obtained and 34 parts by weight of a naphthoquinonediazide compound (PAC-1) shown below are dissolved in hexamethylphosphamide. A resist solution was prepared. Thereafter, the resist solution was applied on a silicon wafer with a spinner and dried at 90 ° C. for 10 minutes to form a photosensitive layer having a thickness of 2.5 μm. Next, a contact exposure machine using a mercury lamp as a light source (manufactured by Cobilit Corporation; CA80)
According to 0), the surface of the photosensitive layer was exposed through a quartz mask for resolution test. After exposure, 140 ° C
After a heat treatment for 5 minutes, the resist developing solution (tetramethylammonium hydroxide 1.
(19 wt% aqueous solution) for 25 seconds. As a result, the sensitivity of the photosensitive layer was 70 mJ.
/ Cm ² When a negative resist pattern was formed, and the cross section of this pattern was observed with an electron microscope,
1.5 μm lines and spaces were resolved, and high resolution was obtained. Further, the photosensitive layer is heated at 150 ° C.
For 1 hour at 320 ° C. for 5 hours to imidize the polyamic acid in the photosensitive layer, and then left at 120 ° C. for 24 hours in saturated steam at 2 atm. As a result, the photosensitive layer was not peeled 100/100, and it was confirmed that the adhesion to the silicon wafer was good.

[0027]

Embedded image Comparative Example 1

The alkali-soluble resin (P-1) and (PA
Table 2 shows the naphthoquinonediazide compounds of C-2).
Dissolved in each part by weight of hexamethylphosphamide shown in 1.
Then, a resist solution was prepared. In addition, it used in Table 1.
The abbreviation of (PAC-2) is naphthoquinonedia shown below.
2 shows a zide compound.

[0029]

Embedded image

[0030]

Next, in the same manner as in Example 1, the resist solution was
The photosensitive layer is formed by coating on a recon wafer, and
Exposure, heat treatment, and development of the photosensitive layer were performed under the conditions shown in
A strike pattern was obtained.

Regarding the obtained resist pattern,
The results of measuring the resolution by observing the cross section with a microscope are displayed.
Shown along with 1. As is clear from Table 1, Comparative Example 1
In this case, the sensitivity at the time of light irradiation is low, and the obtained resist pattern
The resolution of the pattern was also insufficient.

[0033]

[0034]

[0035]

[0036]

[Table 1]

[0037]

As described in detail above, according to the pattern forming method of the present invention, it is possible to form a highly reliable resist pattern with excellent sensitivity and resolution.

Continuation of the front page (56) References JP-A-3-204649 (JP, A) JP-A-4-21851 (JP, A) JP-A-61-97647 (JP, A) JP-A-60-39641 (JP, A) JP-A-1-163207 (JP, A) JP-A-2-166105 (JP, A) JP-A-1-501176 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB G03F 7/022 G03F 7/023 G03F 7/037 G03F 7/38 H01L 21/027

Claims (1)

(57) [Claims] Forming a photosensitive layer, a step of exposing a desired area of the photosensitive layer, the heat treatment on the photosensitive layer after the exposure is subjected to claim 1 an alkali-soluble resin on a substrate composed mainly of photosensitive agent a step, in the pattern forming method and a step of developing the photosensitive layer after the heat treatment, the a
A pattern forming method , wherein the alkali soluble resin is a polyamic acid, and the photosensitizer is a monofunctional naphthoquinonediazide compound represented by the following general formula [1]. Embedded image (Wherein, R _{1 to} R ₄ may be the same or different and each represents hydrogen, an unsubstituted or substituted alkyl group having 1 to 6 carbon atoms, a halogen element, an alkoxy group, a cyano group, a nitro group, It represents a carbonyl group, an aryl group, R ₅
Is a monovalent organic group. )