JP3064966B2 - Pattern exposure method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lithography technique for fabricating a semiconductor device, and more particularly to a pattern exposure method effective as a technique for exposing a reproduced image of a holographic pattern to a resist on a semiconductor substrate. is there.

[0002]

2. Description of the Related Art In patterning a resist by light exposure, a pattern on a mask (reticle) is irradiated with light, and the pattern on the mask is reduced to one-fifth or one-fourth, or the resist is reduced by a factor of one. A desired pattern was formed thereon.

[0005] However, it is difficult to form a fine pattern of 1 μm or less in the 1 × exposure, and it is easy to form a fine pattern of 1 μm or less in the reduced exposure of the mask pattern. Dust on the mask has come to be a major cause of a reduction in yield due to deformation or disappearance of the resist pattern.

In order to solve such a problem, a monthly Semiconductor World June 1995 issue (Monthly Semico
A method using a hologram described on page 123 as a mask is known.

In this method, a hologram dry plate 42 is placed on a prism 41 as shown in FIG.
A transmissive mask 43 to be transferred is placed at a distance of m. Next, the reference light 44 is irradiated from the left side, and the object light 45 coherent to the reference light 44 is irradiated from behind the transmission mask 43 to form an interference pattern between the object light 45 and the reference light 44 on the hologram dry plate 42. Then, a hologram pattern 46 is formed.

[0009] Next, as shown in FIG.
The resist 8 is placed with the resist 47 facing the hologram dry plate 42, and illumination light 48 having the same wavelength as the reference light 44 is irradiated from the right side to form a reproduced image of the hologram pattern 46 on the resist 47. Even if dust is present on the hologram pattern 46 produced in this manner, the dust is hardly affected by the properties of the hologram.

[0007]

As described above, the formation of a resist pattern by exposure using a hologram is characterized by being less susceptible to dust. Since parallel light is used, only equal-magnification exposure can be performed, and it is difficult to form a fine pattern. Further, in the equal-magnification exposure, defects such as dust existing on the mask at the time of producing the hologram pattern are transferred as they are, so that there is a problem that a defect standard in a fine pattern becomes strict.

[0008] The present invention provides a technique that enables a reduction exposure in a hologram mask.

[0009]

According to the first aspect of the present invention, there is provided:
The point is that the reproduced image of the hologram
In pattern exposure method that exposes resist on substrate
By changing the magnification of the reproduced image,
Pattern exposure characterized by exposure by correcting expansion and contraction
Be in the way. The gist of the invention described in claim 2 is that
Wave of illumination light irradiating the holographic pattern
Changing the magnification of the reproduced image by changing the length
The pattern exposure method according to claim 1, wherein
You. The gist of the invention described in claim 3 is that the hologram
The surface of the ramified pattern and the resist on the semiconductor substrate
The magnification of the reproduced image by changing the distance from the
2. The pattern exposure according to claim 1, wherein
Be in the way. The gist of the invention described in claim 4 is that
Wave of illumination light irradiating the holographic pattern
The length, the surface of the holographic pattern and the semiconductor
To change both the distance to the resist surface on the body substrate
Therefore, the magnification of the reproduced image is changed.
Item 1 is a pattern exposure method. Claim 5
The gist of the invention described in the above is that the holographic pattern
The illumination light that irradiates the tunable laser
The pattern exposure method according to claim 2 or 4, wherein
Exists. In the present invention, in a method of exposing a reproduction image of a hologram-formed pattern to a resist on a semiconductor substrate, the reproduction image of the hologram-formed pattern is reduced,
A method of exposing a resist on a semiconductor substrate was used. On the spot
In this case, set the image reproduction light source to a finite distance
It is also possible to use a means to diverge light from the light source.
You. In addition, a beam expander is used as a means to generate divergent light.
It can also be used. In addition, the reproduction light source and the hologram
By changing the relative position with respect to the
The reduction ratio of the raw image can also be changed. Also, the image
Laser light and X-rays can be used as raw light sources.
it can.

In the present invention, in hologram formation and image reproduction, reduced exposure is made possible by using a laser beam from a light source finite distance from the printing plate. As for the principle, for example, as shown in FIG. 7, the light intensity I on the hologram dry plate M is S, the distance from the object B to the dry plate M is R, and the distance from the irradiation light source s to the dry plate M is R. The light aexpik reflected by the object B
It is represented by an interference pattern between S and the light expikR emitted from the light source s. I = | expikR + aexpikS | 2 = 1 + 1 + a + aexpik (SR) + aexp (-ik) (SR) (1 formula) When this hologram is reproduced from a light source L at a distance R1 at a different wavelength, the hologram passes through the dry plate. The complex amplitude U of the light
It is known that U = (1 + a) 2expik1R1 + aexpik (SR) .expik1R1 + aexp (-ik) (SR) expik1R1 (Equation 2). Therefore, the following equation approximately holds for the position of the reproduced image. 1 / λ ′ / (z1) −1 / λ (yB) = 1 / λ ′ / (R1) + 1 / λ / R (3) y1 / yB = z1 / zB (λ ′ / λ) (4) (Expression) x1 = 0 (Equation 5) From the above expression, setting the wavelength ratio λ '/ λ and the light source distance ratio R1 / R so that the reproduced image has a magnification of m times the original object. And a reduced exposure on the hologram is made possible. The magnification can be considered as follows. A mask pattern to be a hologram pattern is placed at the point B, and a dry plate M coated with a resist sensitive to laser light is placed at the point O. Then
A reference light having a wavelength λ is irradiated onto the plate M from the position of the distance R, and at the same time, a part of the reference light (object light) is irradiated onto the mask pattern at the point B.
A hologram pattern is formed on the resist by causing interference with the reference light. Develop the exposed resist on the dry plate M,
A hologram pattern is formed on the dried plate M. Then, at a position at a distance R 'from the hologram pattern dry plate M', to irradiate the hologram dry plate M 'with reproduction light having a wavelength λ' different from the reference light to form a m-fold reproduction image. , (4), m = y1 / yB = z1 / zB (λ ′ / λ) (6). If λ ′ / λ = n, then R ′ is obtained from (3). / R = mzB / mnzB-nR (1-m) (7) The reproduced image at the magnification m is determined by the light source position R 'so that
It can be formed at the position of z1.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of the present invention will be described below with reference to FIGS. 1 and 2
FIGS. 3A and 3B are explanatory diagrams illustrating a method of performing a hologram reduction exposure using a laser light source according to the first embodiment. FIGS. 3 and 5 are diagrams illustrating a method of performing a hologram reduction exposure using a soft X-ray source according to the second embodiment. 5, FIG. 5 and FIG. 6 are views for explaining a method of producing a hologram by the laser light source according to the third embodiment and performing a reduced exposure of the hologram by the soft X-ray source.

(Embodiment 1) First, as shown in FIG. 1, a resist 10 (for example, a resist TD manufactured by Tokyo Ohka Chemical Co., Ltd.)
UR-P007) is placed on a hologram position O (for example, a quartz plate whose surface under the resist is chrome-coated), and then the mask 12 on which the pattern 121 to be transferred is formed is placed on the lithographic position O (For example, −30 cm), and a light (for example, krypton fluoride (KrF) laser light having a wavelength of 248 nm) from the laser light source 13 at a position (for example, 100 cm) that is separated from the dry plate 11 by a distance R (for example, 100 cm). ) Through the divergent light (beam expander) 131 and the half mirror 14
And the mask 12 are simultaneously irradiated to form a latent image of the hologram pattern of the mask 12 on the resist 10 on the dry plate 11.

Next, the dry plate 11 is developed to form a hologram resist pattern, and chromium is dry-etched using the resist as a mask to expose the quartz surface.
To form

Next, as shown in FIG. 2, the dry plate 11 'on which the hologram pattern 15 has been formed is placed at a position O, and a resist 16 (for example, a resist KRF-
L2G) Semiconductor substrate 1 formed on workpiece layer 17
8 with the resist 16 facing the dry plate 11 '
To z1 (e.g., -7.5 cm), and then at a distance R 'from the plate 11' (e.g., 9.0).
9 cm) from the laser light source 19 (for example, wavelength 24
8 nm KrF laser beam) to beam expander 19
Irradiating through the semiconductor substrate 1 by the equation (7)
The resist 16 is formed on the resist 8 as a latent image.

Next, the resist 16 is developed, the object layer 17 is processed by etching using the resist 16 as a mask, and the remaining resist 16 is peeled off to form a desired reduced pattern 122 on the semiconductor substrate 18. Can be formed. Further, in the present embodiment, the pattern reduction magnification is 0.25. However, in order to obtain a reduction magnification of 0.2, from equation (7), set n = 1 and set the reproduction image laser distance R ′. = 6.97 (cm), reproduced image position z1 = -6 (c
m).

(Embodiment 2) An embodiment in which a light source is a soft X-ray having a wavelength of 10 to 40 nm will be described with reference to FIGS.

First, as shown in FIG. 3, a resist 20 (for example, polymethylmethacrylate: PMM)
A) is applied to a dry plate (for example, a silicon (Si) substrate having a layer structure of silicon nitride (SiN) and silicon oxide coated with gold on the lower surface of the resist) 21 at a hologram position O.
Then, the mask 22 on which the pattern 221 to be transferred is formed is placed at a position (for example, −30 cm) away from the printing plate position O by zB, and further, at a position (for example, 100 cm) that is separated from the printing plate 21 by a distance R. Soft X-ray source 23
(For example, xenon (Xe) laser plasma excitation light having a wavelength of 13 nm) from the beam expander 231
And the mask 22 are irradiated simultaneously through the half-mirror 24 and the dry plate 21 and the mask 22.
A latent image of the second hologram pattern is formed.

Next, the dry plate 21 is developed to form a hologram resist pattern, gold is milled and etched using the resist as a mask to expose the silicon surface, the resist is peeled off, and a hologram pattern 25 of gold metal is formed. Form.

Next, as shown in FIG. 4, the dry plate 21 'on which the hologram pattern 25 is formed is placed at a position O, and a resist 26 (for example, PMMA) is formed on a semiconductor substrate 28 on which a work layer 27 is formed. 26 resists on the dry plate 2
1 ′, the position of z1 from the dry plate 21 ′ (for example, −
7.5 cm) and then a distance R 'from the plate 21'.
Soft X-ray source 2 at a remote position (for example, 9.09 cm)
9 (for example, laser plasma excitation light of xenon (Xe) having a wavelength of 13 nm) through the beam expander 291 to obtain the pattern 2 by the equation (7).
A quarter reduced pattern 222 of 21 is formed as a latent image on the resist 26 on the semiconductor substrate 28.

Next, the resist 26 is developed, the object layer 27 is processed by etching using the resist 26 as a mask, and the remaining resist 26 is peeled off to form a desired reduced pattern 222 on the semiconductor substrate 28. Can be formed.

In this embodiment, the pattern reduction magnification is 0.25. However, in order to obtain a reduction magnification of 0.2, from equation (7), set n = 1 and set the reproduction image laser. Distance R '= 6.97 (cm), Reconstructed image position z1 = -6 (c
m).

In this embodiment as well as in the case of X-rays, reduction exposure can be performed without making an optical system such as a complicated lens system or a reflection mirror system.

(Embodiment 3) An embodiment in which a hologram producing light source and an image reproducing light source are different will be described with reference to FIGS.

First, as shown in FIG. 5, in order to produce a hologram dry plate, a dry plate coated with a resist 30 (for example, a resist TDUR-P009 manufactured by Tokyo Ohka) (for example, the surface under the resist is made of tungsten (W ) Coated quartz plate) 31 is placed at the hologram position O, and then the mask 32 on which the pattern 321 to be transferred is formed is placed at a position zB away from the plate position O (for example, -30 cm).
Further, a position (for example, 1
00 cm) from the laser light source 33 (for example, wavelength 2
48 nm krypton fluoride (KrF) laser light)
Is simultaneously irradiated on the dry plate 31 and the mask 32 via the beam expander 331 and the half mirror 34 to form a latent image of the hologram pattern of the mask 32 on the resist 30 on the dry plate 31.

Next, the dry plate 31 is developed to form a hologram resist pattern. Tungsten (W) is dry-etched using the resist as a mask to expose the quartz surface. A pattern 35 is formed.

Next, as shown in FIG. 6, the dry plate 31 ′ on which the hologram pattern 35 is formed is placed at a position O, and a resist 36 (for example, PMMA) is formed on the semiconductor substrate 38 on the work layer 37. The resist 36 surface dry printing 3
1 ′, the position of z1 from the printing plate 31 ′ (for example, −1
43 cm), and then apply light (for example, xenon (Xe) laser plasma excitation light having a wavelength of 13 nm) from the soft X-ray source 39 at a position (for example, 173 cm) away from the printing plate 31 'by a distance R'. By irradiating the dry plate 31 ′ via 391, a quarter reduced pattern 322 of the pattern 321 is formed as a latent image on the resist 36 on the semiconductor substrate 38 by (Equation 7).

Next, the resist 36 is developed, the object layer 37 is processed by etching using the resist 36 as a mask, and the remaining resist 36 is peeled off, so that a reduced desired pattern 322 is formed on the semiconductor substrate 38. Can be formed.

In this embodiment, the reduction ratio of the pattern is 0.25. However, in order to obtain a reduction ratio of 0.2, according to the equation (7), n = 13/248 = 0.0524. It is sufficient that the reproduced image laser distance R '= 133 (cm) and the reproduced image position z1 = -114.5 (cm).

As described above, by setting the wavelengths of the hologram producing light source and the image reproducing light source to be different from each other, the image reproducing position can be arbitrarily adjusted.

Further, according to the above-described embodiment, it is possible not only to perform a much larger reduction compared to the reduction exposure using a conventional stepper or the like, but also to form a highly accurate pattern by using a short wavelength. be able to.

Further, at the time of image reproduction, for example, by using a tunable laser (variable wavelength), the magnification can be freely changed. Therefore, the correction of the chip magnification due to expansion and contraction of the semiconductor substrate (wafer) is performed by changing the laser wavelength. Can also be done. In this case, the relative distance can be changed independently or in combination.

In the above-described embodiment, an actual mask putter is formed for a hologram pattern. However, a hologram pattern (computer-added hologram: CAH) formed by computer calculation is formed on a hologram dry plate. A dry plate may be used for forming a reproduced image. Also, examples of the reduction ratios of 0.25 and 0.2 have been described, but other reduction ratios can be selected and enlargement is possible.

[0033]

In the hologram formation and image reproduction,
By using divergent laser light from a light source finite distance from the plate, a reduced image of the hologram reproduction image can be exposed on the resist on the semiconductor substrate, and the mask pattern can be enlarged to a desired exposure pattern. Therefore, the requirements for the manufacturing accuracy and the defect size are not strict, and the mask can be easily manufactured.

Also, in the case of X-ray exposure, reduced exposure is possible without requiring a complicated optical system such as a lens system and a mirror system other than a half mirror.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a method for performing a hologram reduction exposure using a laser light source according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram of a method for performing holographic reduction exposure using a laser light source according to the first embodiment of the present invention.

FIG. 3 is an explanatory diagram of a method for performing a hologram reduction exposure using a soft X-ray source according to a second embodiment of the present invention.

FIG. 4 is an explanatory diagram of a method for performing a reduced exposure of a hologram using a soft X-ray source according to a second embodiment of the present invention.

FIG. 5 is an explanatory diagram of a method for producing a hologram with a laser light source according to Embodiment 3 of the present invention and performing a reduced exposure of the hologram with a soft X-ray source.

FIG. 6 is an explanatory diagram of a method for producing a hologram using a laser light source according to Embodiment 3 of the present invention and performing a reduced exposure of the hologram using a soft X-ray source.

FIG. 7 is a conceptual diagram illustrating reduction exposure of a hologram according to the present invention.

FIG. 8 is an explanatory diagram showing a conventional example.

FIG. 9 is an explanatory diagram showing a conventional example.

[Explanation of symbols]

 REFERENCE SIGNS LIST 10 resist 11 dry plate M 12 mask 121 pattern 13 laser light source λ 122 reduction pattern 131 beam expander 14 half mirror 15 hologram pattern 11 ′ dry plate M ′ 16 resist 17 workpiece layer 18 semiconductor substrate 19 laser light source (λ ′ = λ ) 191 beam expander 20 resist 21 dry plate M 22 mask 221 pattern 23 soft X-ray source λ 222 reduced pattern 231 beam expander 24 half mirror 25 hologram pattern 21 ′ dry plate M ′ 26 resist 27 workpiece layer 28 semiconductor substrate 29 Soft X-ray source (λ ′ = λ) 291 Beam expander 30 Resist 31 Dry plate M 32 Mask 321 Pattern 33 Laser light source λ 322 Reduction pattern 331 Beam expander 34 Half mirror 3 The hologram pattern 31 'dry plate M' 36 resist 37 to be processed layer 38 semiconductor substrate 39 soft X-ray source lambda '391 beam expander

──────────────────────────────────────────────────続 き Continued on front page (51) Int.Cl. ⁷ Identification code FI H01L 21/30 529 531

Claims (5)

(57) [Claims] 1. A reproduced image of a hologram-formed pattern is
For pattern exposure method to expose resist on semiconductor substrate
And Changing the magnification of the reproduced image expands and contracts the semiconductor substrate.
Pattern exposure method characterized by correcting and exposing
Law. 2. Irradiating the hologram pattern
The reproduction image by changing the wavelength of the illumination light to be reproduced.
2. The pattern according to claim 1, wherein the rate is changed.
Exposure method. 3. The surface of the hologram pattern
Changing the distance from the surface of the resist on the semiconductor substrate
The magnification of the reproduced image is changed by
The pattern exposure method according to claim 1. 4. Irradiating the hologram-formed pattern
The wavelength of the illumination light to be applied and the holographic pattern
Both the distance between the surface of the resist and the surface of the resist on the semiconductor substrate
2. The pattern exposure method according to claim 1 , wherein the magnification of the reproduced image is changed by changing the magnification . 5. Irradiating the hologram pattern
The illuminating light is a tunable laser.
5. The pattern exposure method according to claim 2, wherein: