JP4848837B2 - Comb-shaped electrode exposure method and exposure apparatus - Google Patents

Description

  The present invention relates to a comb electrode exposure method and an exposure apparatus for exposing a comb electrode pattern on a sensitive substrate.

Surface acoustic wave devices have a variety of applications, but typical applications include high-frequency filters (surface acoustic wave resonator type filters) used in small mobile communication devices such as mobile phones. .
The surface acoustic wave device basically has comb-shaped electrodes patterned in a line-and-space pattern on a piezoelectric thin film. In particular, a surface acoustic wave resonator type filter (hereinafter referred to as a SAW filter) is required to reduce the pitch of comb-shaped electrodes in order to increase the frequency of signals, and in the near future a line and space with a pitch of 100 nm or less. It is expected that a pattern of shapes will be required.
JP 2000-223400 A

For patterning with such dimensions, it is conceivable to use an electron beam exposure apparatus or a nanoimprint patterning apparatus, but there are significant problems in processing speed, cost, and the like.
The present invention has been made to solve such a conventional problem, and an object of the present invention is to provide a comb electrode exposure method and exposure apparatus capable of easily and reliably exposing a comb electrode pattern. .

  According to a first aspect of the present invention, there is provided a comb-type electrode exposure method comprising: a first exposure step of exposing a first line-and-space pattern on a sensitive substrate with a pattern image of two-beam interference fringes having a predetermined pitch; And a second exposure step of exposing a second line-and-space pattern on the sensitive substrate with a pattern image of two-beam interference fringes having a double pitch.

The comb electrode exposure method according to a second aspect of the invention is characterized in that in the comb electrode exposure method of the first aspect, the first exposure step and the second exposure step are performed simultaneously.
The comb electrode exposure method according to a third aspect of the present invention is the comb electrode exposure method according to the first or second aspect of the invention, wherein the line end portion of the first line and space pattern and the second line and space are the same. The exposure is performed so that the end of the line of the pattern overlaps.

The comb electrode exposure method according to a fourth aspect of the present invention is the comb electrode exposure method according to the third aspect of the present invention, wherein the exposure of the first line and space pattern or the exposure of the second line and space pattern is a line. It is characterized in that it is performed a plurality of times while shifting in the direction.
According to a fifth aspect of the present invention, there is provided a comb electrode exposure method according to any one of the first to fourth aspects of the invention, wherein the outer ends of the lines of the second line and space pattern are connected. It has the 3rd exposure process which exposes a connection pattern, It is characterized by the above-mentioned.

An exposure apparatus according to a sixth aspect of the invention includes a first optical system that generates a pattern image of two-beam interference fringes having a predetermined pitch and exposes a first line and space pattern on a sensitive substrate, and twice the pitch. And a second optical system for generating a pattern image of two-beam interference fringes having a pitch of 2 and exposing the second line and space pattern on the sensitive substrate.
An exposure apparatus according to a seventh aspect is the exposure apparatus according to the sixth aspect, further comprising a light-shielding pattern that divides a region exposed by the first optical system and a region exposed by the second optical system. It has a light-shielding plate.

  An exposure apparatus according to an eighth invention is characterized in that, in the exposure apparatus according to the sixth or seventh invention, the exposure apparatus further comprises a moving means for moving the sensitive substrate in a line direction of the first line and space pattern.

  In the present invention, the pattern of the comb electrode can be easily and reliably exposed.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
(First embodiment)
FIG. 1 shows a first embodiment of the exposure apparatus of the present invention.
The exposure apparatus has a first optical system 11 and a second optical system 13.
The first optical system 11 generates a pattern image of two-beam interference fringes having a pitch P. Then, as shown in FIG. 2, the first line and space pattern 15 having a pitch P is exposed on the sensitive substrate 17. The second optical system 13 generates a pattern image of two-beam interference fringes having a pitch of 2P. Then, as shown in FIG. 2, the second line and space pattern 19 having a pitch of 2P is exposed on the sensitive substrate 17.

  In the first optical system 11, the light from the light source 21 enters the half mirror 25 through the collimator lens 23. The first light beam 21 </ b> A reflected by the half mirror 25 is bent in a direction parallel to the paper surface by the mirror 27, then reflected by the mirror 29, passes through the light shielding plate 31, and is disposed on the stage 33. Is incident at an angle of θ. On the other hand, the second light beam 21 </ b> B that has passed through the half mirror 25 is bent by the mirror 35 in a direction parallel to the paper surface, then reflected by the mirror 37, passes through the light shielding plate 39, and is placed on the stage 33. The incident angle is incident on the substrate 17 at −θ degrees. Thereby, a pattern image of a two-beam interference fringe with a pitch P is formed.

  In the second optical system 13, the first light beam 21 </ b> A reflected by the half mirror 25 is bent by the mirror 41 in the front-rear direction of the paper surface, then reflected by the mirror 43, passes through the light shielding plate 45, and is on the stage 33. The incident angle is incident at Arcsin (sin θ / 2) degrees with respect to the sensitive substrate 17 disposed in the position. On the other hand, the second light beam 21B that has passed through the half mirror 25 is bent in the front-rear direction of the paper surface by the mirror 47, then reflected by the mirror 49, passes through the light shielding plate 51, and is disposed on the stage 33. 17 is incident at an incident angle of −Arcsin (sin θ / 2) degrees. Thereby, a pattern image of a two-beam interference fringe with a pitch of 2P is formed.

In the vicinity above the sensitive substrate 17, a light shielding plate 53 for limiting the exposure area is disposed.
FIG. 3 shows details of the light shielding plate 53. The light shielding plate 53 is formed with a light shielding pattern for partitioning the region R1 exposed by the first optical system 11 and the region R2 exposed by the second optical system 13. Specifically, an opening 53 a that limits the region R <b> 1 exposed by the first optical system 11 is formed at the center of the light shielding plate 53. Moreover, the opening part 53b for restrict | limiting area | region R2 exposed by the 2nd optical system 13 is formed in the both sides of this opening part 53a. The illumination light from the first optical system 11 and the illumination light from the second optical system 13 are incident in a state larger than the openings 53a and 53b, as indicated by dotted lines in FIG. , 53b are limited to a predetermined size.

In this embodiment, as shown in FIG. 3B, the exposure light from the second optical system 13 is incident obliquely. Thereby, as shown in FIG. 3C, the exposure region R2 of the second optical system 13 slightly overlaps the exposure region R1 of the first optical system 11. Further, the distance between the light shielding plate 53 and the sensitive substrate 17 is, for example, 50 μm.
Hereinafter, a method for exposing a comb electrode using the above-described exposure apparatus will be described. Before describing the exposure method, a SAW filter having a comb-shaped electrode will be described.

  FIG. 4 shows a SAW filter. This SAW filter has comb-shaped electrodes 59 in the signal input portion 55 and the signal output portion 57. The input signal input to the signal input unit 55 is converted into mechanical vibration of the piezoelectric thin film 63 by the comb electrode 59 of the signal input unit 55, and the vibration propagates as a surface acoustic wave. On the other hand, the surface acoustic wave that propagates and reaches the signal output unit 57 becomes mechanical vibration of the piezoelectric thin film 63 and is converted into an electric signal by the comb-shaped electrode 59 of the signal output unit 57. The surface acoustic wave has a feature that it is excited greatly only in a limited frequency band near the resonance frequency, and only a signal near the resonance frequency among the input signals can pass through the SAW filter, and thus acts as a bandpass filter.

  In general, a surface acoustic wave device such as a SAW filter has a relationship of f = V / λs, where V is the propagation velocity of the surface acoustic wave, λs is the wavelength, and f is the frequency. Here, V is a value specific to the material of the substrate on which the surface acoustic wave propagates. Therefore, in order to increase the frequency f, it is necessary to reduce the wavelength λs of the surface acoustic wave. Further, in order to efficiently excite the surface acoustic wave, the pitch P of the comb-shaped electrode 59 needs to coincide with ½ of the surface acoustic wave wavelength λs.

  In particular, in the SAW filter, there is a strong demand for higher frequency in small mobile communication devices such as mobile phones, and a frequency of several tens of GHz is expected to be required in the future. For example, when the surface acoustic wave has a propagation velocity of 4000 m / sec and a surface acoustic wave having a frequency of 20 GHz is excited, the surface acoustic wave has a wavelength of 200 nm and the pattern pitch P of the comb-shaped electrode 59 is 100 nm.

FIG. 5 shows an exposure method for the comb-shaped electrode 59.
In this embodiment, first, as shown in FIG. 5A, the first line and space pattern 15 and the second line and space patterns 19A and 19B are simultaneously exposed on the sensitive substrate 17. The first line and space pattern 15 is exposed by an interference fringe pattern image of a two-beam interference fringe by the first optical system 11. The pitch P between the lines of the first line and space pattern 15 is P = λi / sin θ, where λi is the wavelength of light from the light source. The second line and space patterns 19 </ b> A and 19 </ b> B are exposed by the interference fringe pattern image of the two-beam interference fringes by the second optical system 13. The pitch between the lines of the second line and space patterns 19 </ b> A and 19 </ b> B is twice the pitch of the first line and space pattern 15.

  Then, one second line and space pattern 19A is connected in a state where one line is placed at the end of the line of the first line and space pattern 15 so as to match. The other second line and space pattern 19B is connected to the opposite end of the first line and space pattern 15 in a state shifted from the second line and space pattern 19A by a pitch P. . Note that a piezoelectric thin film layer that is a material of the comb-shaped electrode 59 is formed in advance on the sensitive substrate 17 by vapor deposition or the like, and a photosensitive agent layer is formed on the upper surface of the piezoelectric thin film layer. Then, the first line and space pattern 15 and the second line and space patterns 19A and 19B are exposed to the photosensitive agent layer.

  Next, as shown in FIG. 5B, the connection pattern 63 that connects the outer ends of the second line and space patterns 19A and 19B is exposed, and as shown in FIG. 5C. The exposure of the comb-shaped electrode 59 having a different shape is completed. Since the connection pattern 63 formed in the exposure process has a large size and a large positional error and a large tolerance, a primitive exposure method such as a proximity exposure method may be used. The sensitive substrate 17 thus exposed is developed by a known method, and then the piezoelectric thin film layer is etched to produce a comb-shaped electrode.

  When exposure is performed by the above-described exposure method, a comb-like electrode pattern of surface acoustic waves having a pitch of 100 nm or less can be easily obtained even when a commonly used argon fluoride (ArF) excimer laser light source (wavelength 193 nm) is used as the light source. Can be formed. It is also possible to form a pattern with a pitch of about 80 nm by a method using a fluorine (F2) laser (wavelength 157 nm) having a shorter wavelength or a method of filling the sensitive substrate 17 with a liquid having a high refractive index.

  In the embodiment described above, the first line and space pattern 15 is exposed on the sensitive substrate 17 by the pattern image of the two-beam interference fringes having the predetermined pitch P, and the two-beam interference fringes having a pitch twice the pitch P. Since the second line and space patterns 19A and 19B are exposed on the sensitive substrate 17 by the pattern image, the pattern of the comb-shaped electrode 59 can be easily and reliably exposed.

  Further, since it becomes possible to use a two-beam interference type exposure apparatus, the exposure apparatus can be made simple, small and inexpensive. More specifically, a projection optical system, an exposure master, an exposure master stage, an alignment optical system, and the like necessary for an exposure apparatus of an imaging projection exposure system can be eliminated. Further, since no aberration of image formation occurs, it is possible to expose a wide area at once, and patterning with high throughput becomes possible.

  Further, in the above-described embodiment, as shown in FIG. 3, the exposure light from the second optical system 13 is incident obliquely, and the exposure region R2 of the second optical system 13 is slightly changed from the first optical system. Since it overlaps with the exposure region R1 of the system 11, the line of the first line and space pattern 15 and the lines of the second line and space patterns 19A and 19B can be reliably connected.

That is, when the exposure is performed without overlapping the region R1 exposed by the first optical system 11 and the region R2 exposed by the second optical system 13, as shown in FIG. Since blur occurs due to diffraction at the edge portion E1 of the region R1 of the system 11 and the edge portion E2 of the region of the second optical system 13, a large change in illuminance occurs in the boundary region, and the line width of the line varies greatly. . However, as shown in FIG. 6B, when the region R1 exposed by the first optical system 11 and the region R2 exposed by the second optical system 13 are overlapped and exposed, the illuminance of the connection portion is set. The line width of the connection portion can be suppressed to the minimum. In addition, FIG. 6 has shown the result of having calculated the illumination intensity of the boundary part of an area | region based on the Fresnel diffraction theory.
(Second Embodiment)
In the second embodiment, as shown in FIG. 7, the sensitive substrate 17 is moved in the line direction (Y direction) of the first line and space pattern 15 by the stage 33 (shown in FIG. 1). The line and space pattern 15 is exposed so that the end of the line overlaps the end of the second line and space pattern 19A, 19B (see FIG. 3C).

FIG. 8 shows a method for exposing a comb electrode according to this embodiment.
In this embodiment, first, as shown in FIG. 8A, the first line and space pattern 15 is exposed on the sensitive substrate 17. This exposure is performed with the sensitive substrate 17 positioned at a position as shown in FIG. Then, double exposure is performed by moving the sensitive substrate 17 by a small distance in the front-rear direction of the line by the stage 33. By this double exposure, variation in illuminance due to light diffraction can be reduced.

  Next, as shown in FIG. 8B, the second line is formed such that the end of the second line and space pattern 19A overlaps one end of the line of the first line and space pattern 15. The and space pattern 19A is exposed. This exposure is performed with the sensitive substrate 17 positioned at the position shown in FIG. Then, double exposure is performed by moving the sensitive substrate 17 by a small distance in the front-rear direction of the line by the stage 33. By this double exposure, variation in illuminance due to light diffraction can be reduced.

  Next, as shown in FIG. 8C, the second line is formed so that the end of the second line and space pattern 19B overlaps the other end of the line of the first line and space pattern 15. The and space pattern 19B is exposed. This exposure is performed with the sensitive substrate 17 positioned at the position shown in FIG. Then, double exposure is performed by moving the sensitive substrate 17 by a small distance in the front-rear direction of the line by the stage 33. By this double exposure, variation in illuminance due to light diffraction can be reduced.

Next, as shown in FIG. 8D, the connection pattern 63 that connects the outer ends of the second line and space patterns 19A and 19B is exposed. Thereby, the exposure of the comb-shaped electrode 59 having the shape as shown in FIG.
In this embodiment, when the second line and space patterns 19A and 19B are exposed, the end portions of the second line and space patterns 19A and 19B overlap the end portions of the lines of the first line and space pattern 15. Since the stage 33 is moved, the first line and space pattern 15 and the second line and space patterns 19A and 19B can be reliably connected.

In addition, when the first line and space pattern 15 and the second line and space patterns 19A and 19B are exposed, the stage 33 is moved by a minute distance in the front-rear direction of the line so that double exposure is performed. Variations in illuminance due to diffraction can be reduced.
That is, when double exposure is not performed, as shown in FIG. 9A, the edge portion E1 of the region of the first optical system 11 and the edge portion E2 of the region of the second optical system 13 are The line width of each line varies due to diffraction. However, when performing double exposure, as shown in FIG. 9B, it is possible to minimize the variation in the line width of the connecting portion. FIG. 9 shows the result of calculating the illuminance at the boundary of the region based on the Fresnel diffraction theory.

FIG. 10 shows the principle of reducing illuminance variation by double exposure. That is, when the region R1 exposed by the first optical system 11 and the region R2 exposed by the second optical system 13 are exposed once, in the vicinity of the boundary portion of the exposure region as shown by a thin line in FIG. In this case, the illuminance distribution is greatly waved due to the diffraction, and the illuminance variation as shown in FIG. On the other hand, after exposing each region R1, R2 once, the stage 33 is shifted by half the wavelength of the illuminance distribution wave, and further exposure is performed, as shown by the solid line in FIG. The waviness of the illuminance distribution due to diffraction is reduced, and variation in illuminance can be reduced as shown in FIG.
(Supplementary items of the embodiment)
As mentioned above, although this invention was demonstrated by embodiment mentioned above, the technical scope of this invention is not limited to embodiment mentioned above, For example, the following forms may be sufficient.

(1) In the above-described second embodiment, the example in which the second line and space patterns 19A and 19B are exposed after the first line and space pattern 15 is exposed has been described. The first line and space pattern may be exposed after exposure.
(2) In the above-described embodiment, an example in which the positions of the openings 53a and 53b of the light shielding plate 53 for limiting the exposure region or the vicinity thereof is set as the interference position of the two light beams 21A and 21B has been described. It is also possible to cause the two light beams to interfere with each other at the previous interference position of the optical system and expose the interference fringe pattern on the sensitive substrate through the projection optical system.

It is explanatory drawing which shows 1st Embodiment of the exposure apparatus of this invention. It is explanatory drawing which shows the line and space pattern formed with the exposure apparatus of FIG. It is explanatory drawing which shows the detail of the light-shielding plate of FIG. It is explanatory drawing which shows a SAW filter. It is explanatory drawing which shows 1st Embodiment of the exposure method of the comb-shaped electrode of this invention. It is explanatory drawing which shows the detail of a pattern when the edge part of the 1st line and space pattern and the 2nd line and space pattern are accumulated and exposed. It is explanatory drawing which shows the movement of the sensitive board | substrate in 2nd Embodiment of the exposure method of the comb-shaped electrode of this invention. It is explanatory drawing which shows 2nd Embodiment of the exposure method of the comb-shaped electrode of this invention. It is explanatory drawing which shows the detail of the pattern when a sensitive board | substrate is moved minutely and exposed. It is explanatory drawing which shows the principle of FIG.

Explanation of symbols

11: first optical system, 13: second optical system, 15: first line and space pattern, 17: sensitive substrate, 19, 19A, 19B: second line and space pattern, 33: stage, 53 : Light shielding plate, 59: comb-shaped electrode, 63: connection pattern.

Claims (8)

A first exposure step of exposing a first line and space pattern on a sensitive substrate with a pattern image of two-beam interference fringes having a predetermined pitch;
A second exposure step of exposing a second line and space pattern on the sensitive substrate with a pattern image of two-beam interference fringes having a pitch twice the pitch;
A method for exposing a comb-shaped electrode, comprising: In the exposure method of the comb-shaped electrode according to claim 1,
A comb electrode exposure method, wherein the first exposure step and the second exposure step are performed simultaneously. In the exposure method of the comb-shaped electrode according to claim 1 or 2,
An exposure method for a comb-shaped electrode, wherein exposure is performed so that an end of a line of the first line and space pattern and an end of a line of the second line and space pattern overlap. In the exposure method of the comb-shaped electrode according to claim 3,
A comb-shaped electrode exposure method, wherein the exposure of the first line and space pattern or the exposure of the second line and space pattern is performed a plurality of times while being shifted in a line direction. The comb-shaped electrode exposure method according to any one of claims 1 to 4,
A comb electrode exposure method comprising a third exposure step of exposing a connection pattern that connects outer ends of lines of the second line and space pattern. A first optical system for generating a pattern image of two-beam interference fringes having a predetermined pitch and exposing a first line and space pattern on a sensitive substrate;
A second optical system for generating a pattern image of two-beam interference fringes having a pitch twice the pitch and exposing a second line and space pattern on the sensitive substrate;
An exposure apparatus comprising: The exposure apparatus according to claim 6.
An exposure apparatus comprising: a light shielding plate having a light shielding pattern that partitions an area exposed by the first optical system and an area exposed by the second optical system. In the exposure apparatus according to claim 6 or 7,
An exposure apparatus comprising: moving means for moving the sensitive substrate in a line direction of the first line and space pattern.

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