JPH1010736A - Positive photoresist coating film, positive photoresist composition and pattern forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a positive photoresist coating film which gives a wide range of focus depth for practical use when the film is used in a contact hole process with using a halftone phase shift mask, to provide a positive photoresist compsn. to form the coating film, and to provide a pattern forming method which uses this compsn. SOLUTION: This resist coating film has such properties that when the film is exposed to 45% of the light quantity of Eth for development at 23 deg.C with 2.38wt.% soln. of tetramethylammonium hydroxide, the average developing rate in 0 to 60 seconds is <=25Å/sec. The positive photoresist compsn. to form the coating film above described is applied on a substrate, and the obtd. film is heat treated to remove the solvent and then exposed. Or, if necessary, the substrate with the coating film is heat treated and exposed, and then the coating film is brought into contact with a developer to dissolve and remove the exposed part to form a pattern.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photoresist coating film suitable for fine processing required for the production of a semiconductor device, a positive photoresist composition for providing the coating film, and a pattern formation using the coating film. About the method.

[0002]

2. Description of the Related Art In recent years, fine processing technology represented by the manufacture of integrated circuits has been increasingly improved in processing accuracy. For example, in the case of dynamic random access memory (DRAM), sub-micron processing technology is now available. Has been established as a mass production level technology. The g-line (436 nm), i-line (365 nm),
A photolithography technique using light having a short wavelength such as KrF excimer laser light (248 nm) is used. In these photolithography techniques, a photoresist composition is used, and this photoresist composition has been continuously improved, and various high-performance compositions have been proposed (for example, JP-A-59-45439, JP 62
JP-A-136637, JP-A-62-153950, JP-A-4-136860, JP-A-4-136
No. 941).

In recent years, there has been a limit to shortening the wavelength of the above-mentioned exposure light, and for the purpose of expanding the application limit of the photolithography technique, specific applications of super-resolution techniques such as a phase shift method and a modified illumination method have been proposed. Investigations are being made vigorously (for example, Nikkei Microdevices, May 1989, 67-69).
page. Ibid., July 1990, pp. 108-114. Same, 1
April 992, pages 22-40). Among them, the phase shift method inverts the phases of the adjacent mask transmission portions to obtain a high contrast. Various methods have been reported. From the viewpoint of mask production, etc., a contact hole process and the like were performed using a halftone phase shift mask in which the transmittance of the light-shielded region was controlled to 5 to 15% and the phase difference was controlled to 180 degrees. Recently, a method for obtaining a wide depth of focus by applying the method to the above has been attracting attention.

However, when this halftone phase shift mask is used for a positive photoresist coating film and applied to a hole pattern, the light contrast is improved,
Although the depth of focus at which the hole opens increases, the light-shielding portion is translucent (having a transmittance of 5 to 15%), so the original film thickness called a side lobe or dimple is reduced (part of the resist film is dissolved during development. There is a problem that the film thickness is also reduced in portions that should not be reduced.
For this reason, there has been a demand for a positive photoresist coating film having a large dimple margin with a large depth of focus at which a hole is opened and a small decrease in the film thickness of a light shielding portion.

[0005]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and has as its object the problem of using a halftone phase shift mask and applying it to a contact hole process or the like. Positive photoresist coating film that not only increases the depth of focus where holes and the like are opened, but also has a large dimple margin for film reduction and provides a wide focal depth in practical use, and a positive photoresist composition that provides this coating film And a pattern forming method using the coating film.

[0006]

Means for Solving the Problems The present inventors have conducted intensive studies in order to solve the above-mentioned problems, and as a result, the relationship between the dissolution rate of an exposed photoresist coating film and the amount of exposure has been determined. The present inventors have found that a photoresist coating film having a special dissolution behavior is suitable for a halftone phase shift mask, and have completed the present invention.

That is, the present invention provides: Eth when developing at 23 ° C. using a 2.38% by weight aqueous solution of tetramethylammonium hydroxide in a positive photoresist coating film applied to the substrate
2. The positive photoresist coating film according to item 2.1, wherein the average developing speed in a development time of 0 to 60 seconds at an exposure amount of 45% is 25 ° / sec or less. Positive photoresist composition that gives 3. A step of applying a positive photoresist composition on a substrate, a step of heat-treating the obtained coating film to remove a solvent,
A pattern forming method including a step of exposing the heat-treated coating film, a step of heat-treating the substrate with the coating film as necessary, and a developing step of contacting the exposed coating film with a developing solution to dissolve and remove the exposed portion. 4. A pattern forming method characterized by using the positive-type photoresist coating film described in item 2. or the positive-type photoresist composition described in item 2. Hereinafter, the present invention will be described in detail.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, a method for measuring the dissolution rate of a photoresist coating film and data obtained will be described. The dissolution rate is measured, for example, by a dissolution rate measuring device (Development) sold by PerkinElmer.
(Rate Monitor: DRM) or a lithography simulator sold by Lithotech Japan. A specific method of the measurement is performed, for example, in the following procedure. First, a photoresist composition is applied to a bare silicon wafer or the like according to a standard method. Next, the wafer is heat-treated (prebaked) for the purpose of removing the solvent. This heat treatment is usually 70
A method is adopted in which a wafer is placed on a hot plate heated to １３０130 ° C. and heated for 30 to 120 seconds. Next, using a stepper or the like, the exposure time is changed to a plurality of predetermined portions and exposure is performed for the plurality of exposure times. If necessary, a heat treatment (PEB) similar to the pre-bake is performed after the exposure. Next, the wafer is immersed in a developer, each exposed portion is irradiated with a laser beam, and the reflected light is measured to measure the rate of reduction of the photoresist film by the developer. Usually, an aqueous solution of 1 to 3% by weight, preferably 2 to 2.5% by weight of tetramethylammonium hydroxide (TMAH) is used for development.

FIG. 1 shows an example of the obtained data. The vertical axis indicates the photoresist coating film thickness, and the horizontal axis indicates the development time. The plurality of curves are lines obtained from each exposure unit, and correspond to each exposure amount. As a matter of course, the photoresist film decreases at a short exposure amount (it takes a long time for the photoresist film thickness to become zero), and the photoresist film decreases at a long exposure amount. Is large (the photoresist film thickness becomes zero in a short time). Incidentally, Eth defined in the photolithography process is required for a photoresist film thickness to become zero within a development time (for example, 60 seconds) set in the process in a large exposure pattern such as a 2 mm square. Although defined by the minimum exposure, this can also be said to be the exposure that reaches the point of the intercept with the x-axis corresponding to the set development time in FIG.

The data shown in FIG. 1 further includes an average development speed until the photoresist film thickness becomes zero (average speed between the time of development 0 seconds and the point where the photoresist film thickness becomes zero) and an exposure for giving the speed. Expressed as a relationship diagram with quantity (Fig. 2)
Attempts to grasp the relationship between the line inclination on the low-exposure portion side and the resist performance and reflect the relationship in the photoresist material design were common (for example, Nikkei Microdevice, 199).
May 2013, p. 73). That is, it has been considered that the larger the inclination, the higher the performance, and the same design concept is applied to a photoresist composition for a halftone phase shift mask.

The data as shown in FIG. 1 obtained by DRM did not change significantly depending on the photoresist composition, and the slope of the line generally varied depending on the exposure dose. That is, generally, a photoresist composition giving data as shown in FIG. 1 was generally used (for example, Semicon).
NEWS, December 1988, p. 63). The present inventors conducted data analysis based on FIG. 1 instead of the conventional data arrangement as shown in FIG. 2 and used a photoresist composition which gives a dissolution behavior, which was not known before, for a halftone phase shift mask. The study was conducted based on the material design concept that a suitable photoresist composition was obtained.

That is, in FIG. 1, a photoresist coating having a performance in which the initial dissolution rate is extremely reduced at a low exposure dose (the development rate is extremely low in the early stage of development: hereinafter also referred to as induction). Materials were selected based on the new concept of obtaining a film, a photoresist coating film having the desired dissolution behavior as shown in FIG. 3 was obtained, and its performance was confirmed. As a result, it was found that it was suitable for a halftone phase shift mask. This has led to the present invention.

For a photoresist having such an induction, usually after the induction (when the dissolution rate starts to increase), the average development speed of the entire conventional photoresist film is measured without much difference from the normal speed. In other words, it cannot be identified in FIG. 2 and does not serve as an index for material design. That is, a 2.38% by weight aqueous solution of tetramethylammonium hydroxide (TMAH) was used at 23 ° C. for a positive photoresist coating film applied to a substrate.
The average development speed (DR1) for a development time of 0 to 60 seconds at an exposure amount of 45% of Eth when developing at
It has been found that a positive photoresist coating film characterized by being at most 5 ° / sec satisfies the object.
Eth is determined by the TMAH concentration of the developing solution, the developing temperature, etc.
Therefore, in the present invention, DR1 is defined as the speed under the above development conditions.

It goes without saying that the exposure amount and dissolution rate of 45% of Eth vary depending on the development conditions. If the dissolution rate is too high, the dimple margin decreases, which is not preferable, and is usually 23 ° / second or less, preferably 20 ° / second or less. It should be noted that if this induction is too much, there is an adverse effect, and at an exposure amount of 45% of Eth, the average dissolution rate (DR2) from the start of development to 60 seconds after the start of development until the photoresist film thickness becomes 0 is (DR1) It is necessary that the ratio be larger than that, and (DR2) / (DR1) is usually 1.1 or more, preferably 1.3 or more, more preferably 1.5 or more. Since the preferred absolute value of (DR2) varies depending on (DR1), it cannot be specified unconditionally, but it is usually 10 ° / sec or more, preferably 13 ° / sec or more, and more preferably 15 ° / sec or more. In addition, induction at low exposure is preferable because it meets the purpose of the present invention, but at high exposure, less induction is preferable,
For example, the average developing speed for a developing time of 0 to 30 seconds at the exposure amount of Eth is 50 ° / sec or more, preferably 70 ° / sec.
/ Sec or more, more preferably 100 ° / sec or more.

As the photoresist composition, various conventionally known radiation-sensitive compositions can be used. For example, conventional g-line, i-line, excimer laser light (248n
m, 193 nm) can be used. As a specific positive photoresist composition, a composition obtained by dissolving a 1,2-quinonediazide compound and an alkali-soluble resin in an organic solvent (for example, Journal of the Society of Synthetic Organic Chemistry, Vol. 42, No. 11, p. 979) , JP 6
JP-A-2-136637, JP-A-62-153950, etc.), a so-called chemical amplification type in which depolymerization by an acid or a base generated by light irradiation, or decomposition and elimination of a protective group to exhibit radiation-sensitive performance. And positive photoresist compositions (for example, JP-A-59-45439).

Examples of the 1,2-quinonediazide compound used in the positive photoresist composition include a 1,2-benzoquinonediazide-4-sulfonate derivative of a compound having a phenolic hydroxyl group, and 1,2-naphthoquinonediazide. -4-sulfonic acid ester derivatives,
1,2-naphthoquinonediazide-5-sulfonic acid ester derivatives and the like. Compounds having a phenolic hydroxyl group constituting this ester include 2, 3, 4
Polyhydroxybenzophenones such as trihydroxybenzophenone; polyhydroxybenzoic esters such as ethyl gallate; polyphenols such as bisphenol A produced from phenols and carbonyl compounds; and novolak resins. Examples of the alkali-soluble resin include a novolak resin obtained by polycondensation of a phenol and an aldehyde, and a polymer obtained by (co) polymerizing acrylic acid, cinnamic acid, styrene, maleic acid, and derivatives thereof. .

The photoresist composition of the present invention can be prepared by irradiating a resin having an acid-labile group such as poly (p-tert-butoxycarbonyloxy) styrene with light irradiation such as triphenylsulfonium hexafluoroarsenate. Examples include a photoresist composition comprising a compound that generates an acid and in which a light-irradiated portion is solubilized in a developer (for example, JP-A-59-45439). The photoresist composition usually contains an organic solvent. Examples of the organic solvent include aromatic hydrocarbons such as toluene and xylene; acetates such as ethyl acetate; mono- or dialkyl mono- or diethylene glycol such as ethyl cellosolve. Ethers; mono- or di-alkyl ethers of mono- or di-propylene glycol such as propylene glycol monomethyl ether; alkyl cellosolve carboxylate esters such as propylene glycol monomethyl ether acetate; esters such as ethylene carbonate, γ-butyrolactone; methyl ethyl ketone, 2-heptanone, cyclo Ketones such as pentanone; and hydroxy, alkoxy or alkyl oxyalkylcarboxylates such as ethyl lactate, methyl 3-methoxypropionate and ethyl pyruvate. These solvents are appropriately selected in consideration of the solubility of the resin and the photosensitizer, the stability of the photoresist composition, and the like.

Further, these photoresist compositions include:
If necessary, a surfactant for improving coating properties and a sensitizer for improving sensitivity can be contained. The method of preparing the composition having the dissolution pattern of the present invention using the above-mentioned raw materials will be described below, for example, using the above-mentioned composition as an example. It is known that the effect of suppressing the dissolution of a photosensitizer in a novolak resin or the effect of accelerating the dissolution of a resist film after exposure varies greatly depending on the type of photosensitizer (Honda, et al., SPIE'S 1991).
Symposium on Microlithogr
aphy vol. 1262, MAR. 1991. Kameyama, et al., Mitsubishi Kasei R & D Review, 3 (1), 50
(1989)). Among these photosensitive agents, the effect of suppressing the dissolution of the photosensitive agent in the novolak resin is large, and
The composition of the present invention can be obtained by selecting a photosensitive agent having a large dissolution accelerating effect after exposure and preparing the composition.

Specific examples of such a photosensitive agent include:
For example, 1,2 of oligomers obtained from cresols and formaldehyde and / or acetaldehyde
-Benzoquinonediazide-4-sulfonic acid, 1,2-
Examples include naphthoquinonediazide-4-sulfonic acid and sulfonic acid esters of 1,2-naphthoquinonediazide-5-sulfonic acid. Conventionally, generally used 1,2-benzoquinonediazido-4-sulfonic acid, 1,2-naphthoquinonediazido-4-sulfonic acid of polyhydroxybenzophenones such as 2,3,4-trihydroxybenzophenone, The sulfonate of 1,2-naphthoquinonediazide-5-sulfonic acid is not preferable because the performance of the present invention cannot be obtained. These sensitizers are
The performance varies greatly depending on the esterification ratio of the phenolic hydroxyl group substituted by the sulfonate, but in the present invention, the esterification ratio is appropriately changed and a photosensitive agent suitable for the present invention is selected. It is also preferable to add an additive that meets the purpose of the present invention, such as triphenylmethanol.

The substrate on which the photoresist composition is applied is not particularly limited, but a substrate for IC production such as a silicon substrate or a gallium arsenide substrate is generally used. An ordinary method can be applied to the pattern forming method using the positive photoresist coating film. That is, a step of applying a positive photoresist composition on a substrate and a step of heating (prebaking) the obtained coating film to remove the solvent are performed according to a standard method. Prebake is usually performed using a convection oven or a hot plate, for example, at 70 to 13 minutes.
Performed at 0 ° C. for 30-120 seconds. The thickness of the photoresist film is usually about 0.3 to 5 μm. Exposure is performed using a stepper or the like according to a standard method.
Line (436 nm), i-line (365 nm), KrF excimer laser light (248 nm), ArF excimer laser light (193 nm), and the like are used. Further, the exposed wafer may be subjected to post-exposure baking (PEB) as necessary. This PEB condition is performed according to the above-described pre-bake. Next, a developing step of dissolving and removing the exposed portion by contacting with a developing solution is performed. This developing is usually performed using an organic amine aqueous solution, and is usually performed using tetramethylammonium hydroxide (TM).
An aqueous solution of 1 to 3% by weight of AH) is used. A surfactant, alcohol, and the like can be added to the developer as needed. The development time is preferably about 30 to 180 seconds, and the development temperature is preferably about 15 to 30 ° C.

Although the photoresist composition of the present invention can be suitably used for contact holes, it can also be suitably used for ordinary line-and-space or trench patterns. In addition, the present photoresist composition is suitably used for photolithography using a halftone phase shift mask, but it is preferable that the photolithography using another phase shift mask, the photolithography using modified illumination, and the conventional method not using these are used. Can also be suitably used for lithography.

[0022]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, which should not be construed as limiting the scope of the present invention. In the following examples, the handling of the photoresist composition was performed in a class 100 clean room using a fluorescent lamp that shielded light of 500 nm or less, unless otherwise specified.

Example 1 A cresol-based novolak synthesized from a mixture of m-cresol, p-cresol and 2,5-xylenol (molar ratio = 5: 4: 1) and formaldehyde and acetaldehyde (molar ratio = 8: 2) 13.82 g of resin (N1) (average molecular weight 4,000), a novolak resin (average molecular weight 1,000) synthesized from m-cresol and acetaldehyde, and 1,2-naphthoquinonediazide-
4.05 g of a photosensitizer (P1) (average esterification rate 40%) obtained by reacting 5-sulfonic acid chloride with m
A photosensitizer (P2) obtained by reacting a novolak resin (average molecular weight 1,100) synthesized from cresol and acetaldehyde with 1,2-naphthoquinonediazide-5-sulfonic acid chloride (average esterification rate 25%) 4 .
69 g and triphenylmethanol (A1) 0.24 g
And novolak resin (N2) (average molecular weight 950) 1.2 g synthesized from m-cresol and acetaldehyde / p-hydroxybenzaldehyde (molar ratio = 5: 5)
Was dissolved in a mixture of 68.4 g of ethyl lactate and 7.6 g of butyl acetate. Furthermore, 100% of a fluorine-based surfactant is used.
ppm, and the mixture was filtered through a membrane filter having a pore size of 0.2 μm to prepare a positive photoresist composition A.

The positive photoresist composition A was applied by a spin coater, and baked on a hot plate at 90 ° C. for 60 seconds to form a 1.07 μm thick photoresist coating film. This wafer was prepared using an i-line stepper (Nikon Corporation, NA = 0.5).
Except for using a halftone mask (with a transmittance of 8%), exposure was performed according to a conventional method, and then post-exposure baking was performed on a hot plate at 110 ° C. for 60 seconds. Next, the wafer was immersed in an aqueous solution of 2.38% by weight of tetramethylammonium hydroxide at 23 ° C. for 60 seconds to perform development.

The exposure amount (E) at which a hole pattern having a mask size of 0.4 μm is finished to 0.35 μm on the wafer.
The cross-sectional shape of the pattern formed in h) was observed using an electron microscope. In addition, the depth of focus of the same pattern at the same exposure amount (Eh) (the focus shift range where the resist is dissolved and removed up to the hole base (a hole is opened) and there is no film loss like a dimple pattern) was evaluated. Table-Results
It is shown in FIG. Further, the dissolution rate of the coating film obtained in the same manner at each exposure amount in a developing solution was measured using a lithography simulator (Model) manufactured by Lithotech Japan Co., Ltd.
-780 MkII). The results are shown in Table 1.

Example 2 In Example 1, cresol-based novolak resin (N3) (average molecular weight: 3,500) obtained in the same manner instead of (N1), and 1,2-bis instead of (A1) A positive photoresist composition was prepared in the same manner except that (p-methylphenyl) -1,2-diphenylethanediol (A2) was used. In the same manner as in Example 1,
Each performance was evaluated. The results are shown in Table 1.

Example 3 In Example 1, the solvent of ethyl lactate and butyl acetate was
(N3) 15.0 as a component other than the fluorinated surfactant
Novolak resin (N2) (average molecular weight: 950) synthesized from 2 g, 3.75 g of (P2), m-cresol and acetaldehyde / p-hydroxybenzaldehyde (molar ratio: 5: 5), and 1,2-naphthoquinonediazide-5
-Photosensitizer (P) obtained by reaction with sulfonyl chloride
3) (Average esterification rate 42%) 4.87 g, (A1)
A positive photoresist composition was prepared in the same manner except that 0.36 g was used. Each performance was evaluated in the same manner as in Example 1. The results are shown in Table 1.

Comparative Example 1 In Example 1, 15.85 g of a cresol-based novolak resin (N4) (average molecular weight: 3,800) obtained in the same manner instead of (N1), 7.91 g of (P3), and (A)
1) A positive photoresist composition was prepared in the same manner except that 0.24 g was used. Each performance was evaluated in the same manner as in Example 1. The results are shown in Table 1.

Comparative Example 2 In Example 1, the solvent of ethyl lactate and butyl acetate was
As components other than the fluorine-based surfactant, a mixture of m-cresol, p-cresol and 2,5-xylenol (molar ratio = 4: 5: 1), and a cresol-based novolak resin (N5) synthesized from formaldehyde (Average molecular weight 6,500) 17.06 g and 2,3,4,4'-
2. Photosensitizer (P4) obtained by reacting tetrahydroxybenzophenone with 1,2-naphthoquinonediazido-5-sulfonic acid chloride (average esterification rate 98%)
A positive photoresist composition was prepared in the same manner except that 65 g was used. Each performance was evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0030]

[Table 1] * 1: Average dissolution rate of the photoresist film when the development time is 0 to 60 seconds at an exposure amount of 45% of Eth. * 2: At a exposure amount of 45% of Eth, the development time is 60 seconds and the photoresist film becomes zero. * 3: Average dissolution rate of the photoresist film when the developing time is 0 to 30 seconds at the exposure amount of Eth * 4: The film loss has already occurred in the hole opening. Was.

[0031]

The positive photoresist coating film of the present invention has a special dissolution behavior in relation to the dissolution rate of the exposed coating film and the amount of exposure, so that a halftone phase shift mask is used. When applied to a contact hole process or the like, not only can the depth of focus at which a hole or the like is opened be increased, but also the dimple margin for film reduction is large, and a wide focal depth can be provided in practical use. Therefore, the photoresist composition of the present invention can be suitably used for photolithography for contact holes or using a halftone phase shift mask.

[Brief description of the drawings]

FIG. 1 is a diagram showing the relationship between the thickness of a conventional photoresist coating film and the development time.

FIG. 2 is a view showing a relationship between an average developing speed and an exposure amount until the thickness of a conventional photoresist coating film becomes zero. Thus, it can be seen that the resolution of the g-line resist has been increased by increasing the gradient of the dissolution rate curve from the first generation to the fourth generation (NIKKEI MICRODE).
VICES May 1991).

FIG. 3 is a diagram showing the relationship between the thickness of a photoresist coating film of the present invention and the development time.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical indication H01L 21/30 569E 569F (72) Inventor Shin Ikemoto 1-1 Kurosaki Castle Stone, Yawata-Nishi-ku, Kitakyushu-shi Mitsubishi Chemical Kurosaki Development Laboratory Co., Ltd.

Claims (4)

[Claims] 1. An exposure amount of 45% of Eth when a positive photoresist coating film applied on a substrate is developed at 23 ° C. using a 2.38% by weight aqueous solution of tetramethylammonium hydroxide. Development time 0-6
A positive photoresist coating film, wherein the average developing speed in 0 second is 25 ° / sec or less. 2. A positive photoresist composition which provides the positive photoresist coating film according to claim 1. 3. An average dissolution rate (DR2) for a time period from 60 seconds after the start of development until the photoresist film thickness becomes 0 at an exposure amount of 45% of Eth and an average development rate for a development time of 0 to 60 seconds (DR2). DR1), DR2 / DR1
The positive photoresist coating film according to claim 1 or ≧ 1.1, or the positive photoresist composition according to claim 2. 4. A step of applying a positive photoresist composition on a substrate, a step of heat-treating the obtained coating film to remove a solvent, a step of exposing the heat-treated coating film, and, if necessary, a coating film. 4. A positive photoresist coating film according to claim 1 or 3, wherein the pattern forming method comprises a step of heat-treating the coated substrate and a developing step of bringing the exposed coating film into contact with a developing solution to dissolve and remove the exposed portion. Item 4. A pattern forming method using the positive photoresist composition according to Item 2 or 3.