JP3727296B2 - Pattern formation method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a pattern forming method used in a semiconductor manufacturing process.
[0002]
[Prior art]
Along with the large integration of semiconductor integrated circuits and the downsizing of semiconductor elements, acceleration of development of lithography technology is desired. At present, pattern formation is performed by an optical lithography technique using a mercury lamp, a KrF excimer laser, an ArF excimer laser or the like as exposure light. In order to form a fine resist pattern having a pattern width of 0.1 μm or less, particularly 70 nm or less, vacuum ultraviolet rays such as an F ₂ laser (wavelength: 157 nm band) having a shorter wavelength than the exposure light, Application of ultraviolet rays (wavelength band: 1 nm band to 30 nm band) is being studied, and application of electron beam (EB) exposure such as EB projection exposure or Leapl exposure is being studied.
[0003]
In particular, EB projection exposure and leap exposure are expected to solve the low throughput, which is a problem of conventional EB exposure, in addition to the effect of high resolution by EB exposure.
[0004]
In these exposure methods, transfer is performed using a mask, but since a perforated mask called a stencil mask is used as the mask, the strength of the mask is small. For this reason, it is necessary to use a plurality of masks having a divided mask pattern obtained by dividing one mask pattern, and to connect patterns formed on the resist film by the plurality of masks.
[0005]
Hereinafter, a conventional pattern forming method disclosed in Japanese Patent Laid-Open No. 2000-124118 will be described with reference to FIGS. 3 (a) to 3 (d) and FIGS. 4 (a) and 4 (b).
[0006]
First, a chemically amplified resist material having the following composition is prepared.
[0007]
Poly ((1-ethoxyethyloxystyrene)-(hydroxystyrene)) (however,
1-ethoxyethyloxystyrene: hydroxystyrene = 40 mol%: 60 mol%) (base polymer) ………………………………………………………… 4.0 g
Diphenyldiazodisulfone (acid generator) ……………… 0.12g
Propylene glycol monomethyl ether acetate (solvent) 20g
[0008]
Next, as shown in FIG. 3A, the chemically amplified resist material is applied on the semiconductor substrate 1 to form a resist film 2 having a thickness of 0.4 μm.
[0009]
Next, as shown in FIG. 3B, the first electron beam projection exposure 3A is performed on the resist film 2 through the first mask 4 to perform the first pattern exposure. In this case, the exposure is performed under the conditions of beam blur: 20 nm and focal position: 2 μm. As a result, a first exposure portion (first pattern) 2 a is formed in the resist film 2. The beam blur is the degree of beam blur and can be set by adjusting the current density or the acceleration voltage.
[0010]
Next, as shown in FIG. 3C, a second electron beam projection exposure 3B is performed on the resist film 2 through the second mask 5 to perform a second pattern exposure. The exposure in this case is performed under the conditions of beam blur: 20 nm and focal position: 2 μm. In this way, a second exposure portion (second pattern) 2b is formed in the resist film 2.
[0011]
Next, as shown in FIG. 3D, the resist film 2 subjected to the first and second pattern exposures is subjected to PEB for 60 seconds at a temperature of 100 ° C. using a hot plate. Do. If it does in this way, in the 1st exposure part 2a and the 2nd exposure part 2b of the resist film 2, it will change to the solubility with respect to an alkaline developing solution by the effect | action of the acid generate | occur | produced from an acid generator.
[0012]
Next, when the resist film 2 subjected to PEB is developed with a 2.38 wt% tetramethylammonium hydroxide developer (alkaline developer), as shown in FIG. A resist pattern 6 made of the unexposed portion 2c of the film 2 and having a pattern width of 0.08 μm is obtained.
[0013]
[Problems to be solved by the invention]
However, as shown in FIG. 4 (b) representing the plane of the resist pattern 6, the first exposure portion (first pattern) 2a and the second exposure portion (second pattern) 2b are displaced from each other. Problem occurs.
[0014]
The problem of misalignment between the first exposure unit 2a and the second exposure unit 2b becomes more noticeable as the pattern width becomes finer, and the problem of misregistration occurs not only between the exposure units, It also occurs between unexposed areas.
[0015]
When etching or the like is performed using a resist pattern in which a positional deviation has occurred between the first pattern and the second pattern as a mask, a defect occurs in the obtained semiconductor element.
[0016]
In view of the above, the present invention provides a positional shift between the first pattern formed on the resist film by the first pattern exposure and the second pattern formed on the resist film by the second pattern exposure. The purpose is to reduce.
[0017]
[Means for Solving the Problems]
In order to achieve the above object, a first pattern forming method according to the present invention is configured to focus an electron beam on a resist film through a first mask on which a first mask pattern is formed. Performing a first pattern exposure by irradiating at a position, and a second mask pattern continuous with the first mask pattern formed on the resist film subjected to the first pattern exposure. Irradiating an electron beam at the second focal position through the second mask to perform the second pattern exposure, and developing the resist film on which the first and second pattern exposure has been performed. Forming a resist pattern.
[0018]
According to the first pattern forming method, since the first focal position in the first pattern exposure is different from the second focal position in the second pattern exposure, the pattern transfer position is different. The positional deviation between the first pattern obtained by this pattern exposure and the second pattern obtained by the second pattern exposure is reduced.
[0019]
In the first pattern forming method, the difference between the first focal position and the second focal position is preferably ± 50 μm or less.
[0020]
In the second pattern forming method according to the present invention, the resist film is irradiated with an electron beam with a first beam blur through the first mask on which the first mask pattern is formed. Through the second mask in which a second mask pattern continuous with the first mask pattern is formed on the resist film subjected to the first pattern exposure, Performing a second pattern exposure by irradiating a line with a second beam blur, and developing a resist film subjected to the first and second pattern exposures to form a resist pattern. I have.
[0021]
According to the second pattern forming method, since the first beam blur in the first pattern exposure is different from the second beam blur in the second pattern exposure, the pattern transfer position is different. The positional deviation between the first pattern obtained by this pattern exposure and the second pattern obtained by the second pattern exposure is reduced.
[0022]
In the second pattern forming method, the ratio of the difference between the second beam blur and the first beam blur to the first beam blur is preferably ± 100% or less.
[0023]
In the first or second pattern formation method, the acceleration voltage of the electron beam in the first and second pattern exposures is preferably 0.5 kV or more and 200 kV or less.
[0024]
DETAILED DESCRIPTION OF THE INVENTION
(First embodiment)
The pattern forming method according to the first embodiment of the present invention will be described below with reference to FIGS. 1 (a) to 1 (d) and FIGS. 2 (a) and 2 (b).
[0025]
First, a chemically amplified resist material having the following composition is prepared.
[0026]
Poly ((1-ethoxyethyloxystyrene)-(hydroxystyrene)) (however,
1-ethoxyethyloxystyrene: hydroxystyrene = 40 mol%: 60 mol%) (base polymer) ………………………………………………………… 4.0 g
Diphenyldiazodisulfone (acid generator) ……………… 0.12g
Propylene glycol monomethyl ether acetate (solvent) 20g
[0027]
Next, as shown in FIG. 1A, a chemically amplified resist material is applied on the semiconductor substrate 10 to form a resist film 11 having a thickness of 0.4 μm.
[0028]
Next, as shown in FIG. 1B, the first electron beam projection exposure 12A is performed on the resist film 11 through the first mask 13 on which the first mask pattern is formed. First pattern exposure is performed. The exposure in this case is performed under the conditions of beam blur: 20 nm and focal position: 2 μm. As a result, a first exposure portion (first pattern) 11 a is formed in the resist film 11.
[0029]
Next, as shown in FIG. 1C, a second electron beam projection exposure 12B is performed on the resist film 11 to form a second mask pattern that is continuous with the first mask pattern. The second pattern exposure is performed through the mask 14. In this case, the exposure is performed under the conditions of beam blur: 20 nm and focal position: 21 μm. As a result, a second exposure portion (second pattern) 11 b is formed in the resist film 11.
[0030]
Next, as shown in FIG. 1 (d), the resist film 11 subjected to the first and second pattern exposures is subjected to PEB for 60 seconds at a temperature of 100 ° C. using a hot plate. Do. If it does in this way, in the 1st exposure part 11a and the 2nd exposure part 11b of the resist film 11, it will change to the solubility with respect to an alkaline developing solution by the effect | action of the acid generated from an acid generator.
[0031]
Next, when the resist film 11 subjected to PEB is developed with a 2.38 wt% tetramethylammonium hydroxide developer (alkaline developer), as shown in FIG. A resist pattern 15 made of the unexposed portion 11c of the film 11 and having a pattern width of 0.08 μm is obtained.
[0032]
According to the first embodiment, since the focal position is changed between the first pattern exposure and the second pattern exposure, the distance between the first exposure unit 11a and the second exposure unit 11b is changed. Since the positional deviation is reduced, a resist pattern 15 having a high joining accuracy can be obtained as shown in the plan view of FIG.
[0033]
In the first embodiment, the difference between the first focus position and the second focus position is 19 μm. However, the difference is not limited thereto, and may be ± 50 μm or less. If it does in this way, position shift between the 1st exposure part 11a and the 2nd exposure part 11b can be reduced.
[0034]
(Second Embodiment)
The pattern forming method according to the second embodiment of the present invention will be described below.
[0035]
Since the second embodiment differs from the first embodiment only in the exposure conditions of the first pattern exposure and the second pattern exposure, only the exposure conditions will be described below.
[0036]
The first pattern exposure is performed under the conditions of beam blur: 20 nm and focal position: −3 μm.
[0037]
The second pattern exposure is performed under the conditions of beam blur: 35 nm and focal position: -3 μm.
[0038]
According to the second embodiment, since the beam blur is changed between the first pattern exposure and the second pattern exposure, the positional deviation between the first exposure unit and the second exposure unit. Therefore, a resist pattern with high joining accuracy can be obtained.
[0039]
In the second embodiment, the ratio of the difference between the first beam blur and the second beam blur to the first beam blur is 75%. However, the ratio is not limited to this and is ± 100% or less. If it is. If it does in this way, position shift between the 1st exposure part and the 2nd exposure part can be reduced.
[0040]
In the first embodiment and the second embodiment, the acceleration voltage of the electron beam in the first and second pattern exposures is preferably 0.5 kV or more and 200 kV or less.
[0041]
【The invention's effect】
According to the first or second pattern forming method of the present invention, the pattern transfer position is different between the first pattern exposure and the second pattern exposure. The positional deviation between the first pattern to be obtained and the second pattern obtained by the second pattern exposure is reduced.
[Brief description of the drawings]
FIGS. 1A to 1D are sectional views showing respective steps of a pattern forming method according to a first embodiment.
2A is a cross-sectional view showing one step of the pattern forming method according to the first embodiment, and FIG. 2B is a plan view showing one step of the pattern forming method according to the first embodiment. is there.
FIGS. 3A to 3D are sectional views showing respective steps of a conventional pattern forming method.
4A is a cross-sectional view showing one step of a conventional pattern forming method, and FIG. 4B is a plan view showing one step of a conventional pattern forming method.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Semiconductor substrate 11 Resist film 11a 1st exposure part 11b 2nd exposure part 11c Unexposed part 12A, 12B Projection exposure 13 1st mask 14 2nd mask 15 Resist pattern

Claims (4)

Irradiating an electron beam with a first beam blur to the resist film through a first mask on which a first mask pattern is formed, and performing a first pattern exposure;
Setting the second beam blur such that the difference from the first beam blur is a ratio of ± 100% or less with respect to the first beam blur;
With respect to the resist film subjected to the first pattern exposure, an electron beam is transmitted through the second mask in which a second mask pattern continuous with the first mask pattern is formed . Irradiating with the second beam blur different from the beam blur to perform a second pattern exposure;
And a step of developing the resist film on which the first and second pattern exposures have been performed to form a resist pattern.   The pattern forming method according to claim 1, wherein an acceleration voltage of the electron beam in the first and second pattern exposures is 0.5 kV or more and 200 kV or less. The pattern forming method according to claim 1, wherein the second beam blur is set so that a difference from the first beam blur is 75% with respect to the first beam blur. . 2. The pattern forming method according to claim 1, wherein a focal position at the time of exposure is the same in the first pattern exposure and the second pattern exposure.

Images