JPH06342214A - Fine resist pattern forming method - Google Patents

Abstract

PURPOSE:To perform improvement so that the resolution of a resist pattern can be enhanced. CONSTITUTION:A resist film 2 contg. a naphthoquinonediazido deriv. and novolak resin is formed on a semiconductor substrate 1 and an image is formed in the resist film 2 by selectively irradiating the resist film 2 with light. The resist film 2 is half developed with an alkali developer and the half developed resist film 2 is heated and subjected to 2nd-stage development with an alkali developer to complete the objective resist pattern 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention generally relates to a method for forming a fine resist pattern, and more particularly, it is possible to form a fine resist pattern improved so that the resolution of the resist pattern can be improved. Regarding the method.

[0002]

13 is a partial cross-sectional view of a semiconductor device in each step of the order of a conventional resist pattern forming method.

Referring to FIG. 13A, a resist film 2 containing a naphthoquinonediazide derivative (photosensitizer) and a novolac resin is applied onto a semiconductor substrate 1.

Referring to FIG. 13B, the resist film 2
Is prebaked at 80 to 100 ° C., whereby the solvent contained in the resist film 2 is evaporated.

Referring to FIG. 13C, the photomask 3
Is used to selectively irradiate the resist film 2 with light to form an image in the resist film 2.

Referring to FIG. 13D, a heat treatment (Post Exposure Bake: PEB) after exposure is performed at a temperature of 100 to 130 ° C.
To do. The PEB process evaporates the solvent in the resist film 2 and diffuses the photosensitizer into the resist film 2.

Referring to FIGS. 13D and 13E, the resist film 2 is developed with an alkali developing solution to form a positive resist pattern 4 from which the exposed portion is removed.

[0008]

The conventional method of forming a resist pattern is performed as described above, and there is no problem when the size of the resist pattern is large. However, as the resist pattern becomes finer, it becomes impossible to satisfy the requirement for the depth of focus. That is, as the resist pattern becomes finer, a problem arises that the fluctuation of the focus of the optical system during exposure cannot be ignored.

Since the requirement for the depth of focus is not satisfied, there is a problem even when the step 5 exists on the surface of the semiconductor substrate 1 as shown in FIG. 14
For example, if the position A is focused, the positions B and C are out of focus. When the exposed resist film 2 is developed in such a state, as shown in FIG.
Referring to, a good resist pattern is generated at the position A, but a constriction 50 occurs at the position B, and a film reduction 60 occurs at the position C.

Further, according to the conventional method, as the size of the resist pattern becomes finer, the requirement for the margin of exposure energy cannot be satisfied. The margin of exposure energy is
It is represented by E ₀ / E _C with reference to FIGS.

The exposure amount E _C can be calculated by referring to FIG.
It represents the minimum exposure energy required to form a pattern. If the exposure energy is smaller than E _C , the resist film 2
, The resolution is poor and the pattern 4a and the pattern 4b cannot be separated.

The exposure dose E ₀ is the exposure energy required to form the resist pattern 4 in accordance with the target dimensions of the photomask, as shown in FIG. 16 (b). Normally, the exposure amount E ₀
Then, the resist film is exposed.

Since the exposure energy of the exposure machine fluctuates and the thickness of the resist film also fluctuates, it is preferable that the margin of exposure energy is large. However, as the resist pattern becomes finer, the margin of exposure energy becomes smaller. Getting smaller,
Consequently, there is a problem that a fine resist pattern cannot be stably formed.

The present invention has been made to solve the above problems, and an object thereof is to provide a method for forming a fine resist pattern which is improved so that the depth of focus can be increased.

Another object of the present invention is to provide a method of forming a fine resist pattern which is improved so that the margin of exposure energy can be expanded.

Still another object of the present invention is to provide an improved method of forming a fine resist pattern so that the resolution can be improved.

Still another object of the present invention is to provide a method for forming a fine resist pattern having L / S of 0.5 μm to 0.25 μm.

[0018]

In the method for forming a fine resist pattern according to the present invention, first, a photosensitizer containing a 0-quinonediazide compound and a polymer having a hydroxyl group and an aromatic ring are provided on a semiconductor substrate. A resist film containing is formed. Selectively irradiate the resist film with light,
An image is formed in the resist film. By the first development, the resist film is partially developed using an alkali developing solution. The resist film whose development has been stopped halfway is heat-treated, whereby the surface of the resist film and the alkali developing solution remaining on the surface of the resist film are chemically reacted. The resist film is developed a second time by using an alkali developing solution, thereby completing the resist pattern.

[0019]

According to the method of forming a fine resist pattern according to the present invention, the resist film is partially developed with an alkali developing solution, and then the resist film is heat-treated. By this heat treatment, the surface of the resist film is chemically reacted with the alkaline developer remaining on the surface of the resist film to form a dissolution promoting layer in the exposed portion and a poorly soluble layer in the unexposed portion. .

[0020]

Embodiments of the present invention will be described below with reference to the drawings.

Referring to FIG. 1A, a resist film 2 containing a naphthoquinonediazide derivative which is a photosensitizer and a novolac resin is formed on a semiconductor substrate 1.

Referring to FIG. 1B, the resist film 2 is
Pre-baked at a temperature of 80 to 100 ° C. to form a resist film 2
The solvent in is evaporated.

Referring to FIG. 1C, the resist film 2 is selectively irradiated with light using the photomask 3 to form an image in the resist film 2.

Referring to FIG. 1D, after exposure, the resist film 2 is heat treated at a temperature of 100 to 130 ° C. (PEB treatment).
Then, the solvent in the resist film 2 is evaporated and the photosensitive agent is diffused. The PEB process is performed for about 1 minute.

Referring to FIG. 1 (e), an alkali developing solution containing tetramethylammonium hydroxide was used to prepare about 2
The first development processing is performed by the paddle development method for 0 seconds. As a result, the resist film 2 is partially developed. The first development is preferably performed for 1/10 to 1/2 of the total development time, as described later.

FIG. 2 is a conceptual diagram for explaining the paddle developing method. The paddle developing device 7 includes a support 9 for supporting the semiconductor substrate 1 from below, a pipe 10 for supplying pure water, and a pipe 11 for supplying a developing solution.
The support base 9 rotates in the arrow R direction.

The operation of the first development will be described with reference to FIG. The semiconductor substrate 1 that has been subjected to PEB processing is placed on the support 9. Rotate the semiconductor substrate 1 (1000
The developing solution is supplied onto the semiconductor substrate 1 through the pipe 11 while being rotated at (rpm). Then, the rotation is stopped and the development is performed for about 20 seconds. Then, while rotating the semiconductor substrate 1,
Pure water is supplied onto the semiconductor substrate 1 through the pipe 10. Then, the semiconductor substrate 1 is dried.

Returning to FIG. 1F, the resist film 2 is heated at a temperature of 50 to 130 ° C., preferably about 100 ° C. for 1 minute.
To heat.

By this heat treatment, as shown in FIGS.
The surface of the resist film 2 reacts with the residual alkali developer according to the reaction formula shown in FIG. Since this heating is baking to accelerate the chemical reaction, this heating will be referred to as C below.
It is abbreviated as EB.

Referring to FIGS. 3 (a) and 1 (f), in the unexposed region, the naphthoquinonediazide derivative in the resist film and the novolak resin are bonded by azo coupling or azooxy coupling, and it is difficult. Solution layer 12
Is formed. The azo coupling and the azoxy coupling reaction proceed with the alkali remaining on the surface of the resist film as a catalyst.

On the other hand, referring to FIG. 3 (b) and FIG. 1 (f), in the exposed region, water is added to the ketene generated by the decomposition of the naphthoquinonediazide derivative to form an indenecarboxylic acid derivative. Consequently, the dissolution promoting layer 13 is formed.

With reference to FIGS. 1F and 2, the poorly soluble layer 1
The semiconductor substrate 1 including 2 and the dissolution promoting layer 13 is placed on the support 9. While rotating (1000 rpm) the semiconductor substrate 1, the developer is supplied onto the semiconductor substrate 1 through the pipe 11. After that, the rotation is stopped and the resist film 2 is set to 40
Develop for seconds.

As a result, referring to FIG. 1 (g), the development of the resist film 2 proceeds completely, and the resist pattern 4 is formed.
Is formed. With reference to FIG. 1F, since the dissolution promoting layer 13 is formed in the exposed portion and the hardly soluble layer 12 is formed in the unexposed portion, the contrast of dissolution is enhanced and the resist pattern 4 is high. Stable formation with high accuracy.

Further, referring to FIGS. 1 (f) and 4, due to the action of the dissolution promoting layer 13, the minimum exposure energy E _C becomes small, while the hardly soluble layer 1 formed on the side wall of the pattern.
By the action of 2, the exposure energy (E ₀ ) required to form the resist pattern in accordance with the target dimension of the photomask becomes large. Therefore, the margin of exposure energy (E ₀ /
E _C ) becomes larger.

Table 1 shows that the total development time (first development time + second development time) was 60 seconds, and the first development time was variously changed to obtain E ₀ / E _C. , The focus margin of the shape and the focus margin of the resist dimension are summarized. These were obtained for three types of L / S of 0.45 μm, 0.40 μm, and 0.35 μm.

In Table 1, as a reference example, data when the temperature of CEB treatment is 60 ° C. is also shown. In addition, the data obtained by performing the conventional development method in which the development is performed once is also described.

As is clear from Table 1, when the first development time is 10 seconds and the second development time is 50 seconds, the margin of exposure energy (E ₀ / E _C ) is the highest. The focus margin of shape and size was the largest.

Further, as a result of experiments, it was found that the first development was required for 1/10 or more of the total development time. When the first development time is less than 1/10 of the total development time, pattern 2 is not formed well with reference to FIG. Note that FIG. 5A is a cross-sectional view of the semiconductor device when the pattern 2 is normally formed. If the first development time is longer than ½ of the total development time, referring to Table 1, an image cannot be formed. From the above results, the first development is 1/10 to 1 of the total development time.
It is preferable to do this for a time of / 2.

[0039]

[Table 1]

FIG. 6 is a relationship diagram between the focus offset and the exposure energy margin (E ₀ / E _C ) when the CEB temperature is variously changed. The development was performed so that the first development time was 10 seconds and the second development time was 50 seconds. The evaluated pattern is 0.4
The pattern was μmL / S. As the temperature of CEB,
Three types of 85 ° C, 100 ° C and 120 ° C were selected. Note that FIG. 6 also shows data obtained by performing the conventional method (method without CEB treatment).

In FIG. 7, the CEB temperature is plotted on the horizontal axis and the value of E ₀ / E _c is plotted on the vertical axis, which is plotted. As is clear from FIGS. 6 and 7, it was found that the value of E ₀ / E _c was the largest when the CEB temperature was 100 ° C. Moreover, the preferable range of the CEB temperature is 85 ° C. to 12 ° C.
It was also revealed to be 0 ° C.

According to the present embodiment, referring to FIG. 8, when there is a step on the surface of the semiconductor substrate, not only the in-focus portion (A) but also the out-of-focus portion (B,
Also in C), a good resist pattern 4 is formed. That is, according to this embodiment, the depth of focus is greatly expanded.

FIGS. 9 and 10 show the matrix of the irradiation amount (expressed in irradiation time ms. The illuminance is 500 mW / cm ² ) and the focus offset (μm) for the 0.4 μmL / S pattern. FIG. 6 is a graph showing the relationship between the resist size and the focus offset at each irradiation amount when changed with. In these figures,
The dose increases from the upper curve to the lower curve.

FIG. 9 shows a conventional developing method, and the developing time was 60 seconds. The pattern is 0.40 μmL
/ S was selected. FIG. 10 shows the result of the present invention. The first developing time was 10 seconds, the second developing time was 50 seconds, and the CEB temperature was 100 ° C. A pattern of 0.40 μmL / S was selected. 9 and 10, the vertical axis represents the resist size, and the horizontal axis represents the focus offset value.

When the irradiation dose is small, the resist size is
It changes to a thick dimension in response to focus fluctuations. As the irradiation amount increases, the resist dimension changes to a smaller dimension with respect to the focus fluctuation. At the same time, the dimensional transition due to the focus variation of each irradiation amount becomes concave at a place where the irradiation amount is small, that is, the line and space tends to be connected due to defocus. On the other hand, in a place where the irradiation amount is large, the dimensional transition due to the focus variation of each irradiation amount becomes convex, that is, the line and space tends to be broken due to defocus.

The resist size is the mask design value (0.40 μ
Dimensional focus margin (resist dimension: 0.40 μm ± 0.05 μ) when finished as mL / S)
In the conventional developing method, m) is −0.3 μm to +0.6 μm (Ran by referring to the vicinity of the irradiation amount of 550 ms in FIG.
ge 0.9 μm). According to the present invention, when extrapolating and considering with reference to the vicinity of the middle of 575 ms and 600 ms in FIG. 10, the dimension focus margin is -0.7.
μm to +0.9 μm (Range 1.6 μm),
As a result, the focus margin is improved by 0.7 μm. It was also found that the focus margin of the convex portion where the irradiation amount was increased was also improved as a whole.

In the above examples, the novolac resin was used as the base polymer, but the present invention is not limited to this. That is, referring to FIG. 11, phenol 11 and cresol 1 belonging to the monomer group (a)
2, resorcinol 13, methylresorcinol 14,
Xylenol 15, catechol 16, hydroquinone 1
7, a monomer selected from phloroglucin 18, 1,2,4-benzenetriol, and formalin 20, acetaldehyde 21, acetone 2 belonging to the monomer group (b)
2, a copolymer with a copolymerization monomer selected from benzaldehyde 23 can also be preferably used.

In the above examples, the naphthoquinodiazide derivative was used as the photosensitizer. Specifically, referring to FIG. 12, 1,2-naphthoquinonediazide-4-sulfonic acid ester 24, 1,2-naphthoquinonediazide-5-sulfonic acid ester 25, 2,1-naphthoquinonediazide- 4-sulfonic acid eruter 26,2
1-naphthoquinonediazide-5-sulfonic acid ester 2
7 includes a photosensitizer in which the photosensitizer base 29 is bonded. Also,
A photosensitizer obtained by binding 1,2-benzoquinonediazide-4-sulfonic acid ester 24 to a photoconductor 29 is also preferably used.

[0049]

As described above, according to the method of forming a fine resist pattern according to the present invention, the resist film is partially developed with an alkali developing solution, and then the resist film is heat-treated (CEB). By this heat treatment,
The surface of the resist film and the alkaline developer remaining on the surface of the resist film chemically react with each other to form a dissolution promoting layer in the exposed portion and a poorly soluble layer in the unexposed portion. As a result, the depth of focus can be increased, the margin of exposure energy can be increased, and the resolution can be improved.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional view of a semiconductor device in each step of an order of a method for forming a fine resist pattern according to an embodiment of the present invention.

FIG. 2 is a diagram showing a method of paddle development adopted in the present invention.

FIG. 3 is a diagram showing a reaction formula of a reaction occurring on the surfaces of an unexposed region and an exposed region when a resist film developed halfway is subjected to CEB treatment.

FIG. 4 illustrates how E ₀ / E _c increases in the present embodiment.

FIG. 5 illustrates a state of a resist pattern when the first development time is short.

FIG. 6 is a relationship diagram between a focus offset and an exposure energy margin (E ₀ / E _C ) at various CEB temperatures.

FIG. 7 is a diagram showing a relationship between CEB temperature and E ₀ / E _C.

FIG. 8 is a sectional view of a resist pattern obtained by carrying out the present invention using a semiconductor substrate having a step portion.

FIG. 9 is a diagram showing the relationship between the focus offset and the size of the resist pattern when the conventional developing method is performed with various irradiation doses.

FIG. 10 is a relationship diagram between the focus offset and the size of the resist pattern when the developing method of the present invention is performed with various irradiation doses.

FIG. 11 is a diagram showing a chemical formula of a copolymerization monomer component of the polymer used in the present invention.

FIG. 12 is a diagram showing a chemical formula of a photosensitive component to be bonded to a photosensitive base of a photosensitive agent used in the present invention.

FIG. 13 is a partial cross-sectional view of the semiconductor device in each step of the order of the conventional resist pattern forming method.

FIG. 14 shows a case where a step exists on the surface of a semiconductor substrate,
It is the figure which showed the reason that defocus occurs.

FIG. 15 is a diagram showing a problem in the conventional method.

FIG. 16 is a diagram for explaining the concept of a margin of exposure energy (E ₀ / E _C ).

[Explanation of symbols]

 1 semiconductor substrate 2 resist film 3 photomask 4 resist pattern

Claims (4)

[Claims] 1. A step of forming, on a semiconductor substrate, a resist film containing a photosensitizer containing a 0-quinonediazide compound and a polymer having a hydroxyl group and an aromatic ring, and the resist film is selectively irradiated with light. Then, a step of forming an image in the resist film thereby, a first developing step of developing the resist film halfway with an alkali developing solution, and a heat treatment of the resist film whose development is stopped halfway The step of chemically reacting the surface of the resist film with the alkaline developer remaining on the surface of the resist film, and developing the resist film again with the alkaline developer, And a second developing step for completing the resist pattern by the step of forming a fine resist pattern. 2. The polymer includes novolac resin,
The method for forming a fine resist pattern according to claim 1. 3. The first development is 1/1 times the minimum development time required to complete a resist pattern.
The method for forming a fine resist pattern according to claim 1, wherein the method is performed in a time of 0 to 1/2. 4. The method for forming a fine resist pattern according to claim 1, wherein the heat treatment for causing the chemical reaction is performed at a temperature of 85 ° C. to 120 ° C.