JPH0545508A - Patterning method for diffraction grating - Google Patents

Abstract

PURPOSE:To form a diffraction grating having the bearing coincident with the bearing of the diffraction grating formed on one surface of a substrate on the other surface. CONSTITUTION:A reference substrate 12 formed with the diffraction grating is fixed on a rotary stage 11 and a laser beam 41 emitted from a laser beam source 40 for exposing is divided to 41a and 41b. The surface of this reference substrate 12 is irradiated with these beams. The interference fringes of the reflected and diffracted light and the reflected light by the diffraction grating are projected on a screen 50. The bearing of the diffraction grating and the bearing of the interference fringes by two optical fluxes 41a and 41b are aligned. The diffraction grating is irradiated with the bearing detecting light from a laser beam source 30 for bearing detection and the incident angle of the bearing detecting light 31 is adjusted by the position of the reflected and diffracted light captured by a position detector 33. A substrate 14 for processing is fixed in place of the reference substrate 12 on the rotary stage 11 in such a state and is irradiated with the bearing detecting light 31 from a laser beam source 30 for bearing detection. The bearing of the diffraction grating is then so adjusted as to maximize the intensity of the refracted and diffracted light.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for patterning a diffraction grating on a transparent substrate, and in particular, a diffraction grating having the same orientation as that of a diffraction grating formed on one surface of the transparent substrate is provided on the other side of the transparent substrate. A method of patterning a surface.

[0002]

2. Description of the Related Art In recent years, as a substitute for a polarization beam splitter used in various optical applications, a double-sided polarization diffractive element in which diffraction gratings are formed on both sides of a flat transparent substrate in the same orientation Being developed.

Such a double-sided polarization diffraction element may be manufactured by bonding two transparent substrates each having a diffraction grating formed on one side thereof to the surfaces of the substrates on which the diffraction grating is not formed. In this case, it is necessary to align each substrate so that the orientation of the diffraction grating of each substrate is in a predetermined state, and usually, the alignment marker provided on each substrate is observed with an optical microscope and each substrate is aligned. Must be aligned.

When forming a diffraction grating on a transparent substrate,
Normally, a method of mechanically forming with a cutter was adopted, but recently, in order to form a diffraction grating with high precision, a photoresist is applied to the surface of the substrate, and this photoresist is treated with a laser beam. A method of irradiating two coherent light fluxes so that interference fringes having a predetermined pitch are formed has also been developed.

[0005]

When manufacturing a double-sided polarization diffractive element, a method of bonding a pair of transparent substrates having a diffraction grating formed on one side to each other is used when the grating pitch of the diffraction grating is as narrow as the wavelength of light. However, the orientations of the diffraction gratings cannot be matched with high precision. Further, it is inevitable that an error will occur when the transparent substrates are attached to each other, and it is not easy to align the orientations of the diffraction gratings.

As described above, a method of forming diffraction gratings on both surfaces of a single transparent substrate has been developed in place of the method of bonding a pair of transparent substrates to each other. In this case, the first diffraction grating is formed on one surface of one transparent substrate, and then the second diffraction grating is formed on the other surface of the transparent substrate so that the azimuth coincides with this diffraction grating. Need to be formed. However, after forming the first diffraction grating on one surface of the transparent substrate, the second diffraction grating is formed on the other surface of the transparent substrate.
It is not easy to form the first diffraction grating in the same direction as that of the first diffraction grating, and therefore there is a problem that the double-sided polarization diffraction grating cannot be manufactured with high accuracy in a short time.

The present invention solves such a problem, and an object of the present invention is to provide a diffraction grating formed on one surface of a transparent substrate with a high-precision azimuth direction on the other side of the transparent substrate. Another object of the present invention is to provide a method of patterning a diffraction grating that can be formed on the surface of the substrate in a short time.

[0008]

In the method of patterning a diffraction grating according to the present invention, a photoresist is applied to the other surface of a substrate having a diffraction grating formed on one surface so that the azimuth coincides with that of the diffraction grating. A method of patterning a diffraction grating by irradiating the photoresist with two light fluxes so that interference fringes having a predetermined pitch are formed, wherein the two light fluxes are irradiated onto a surface of the substrate coated with the photoresist. hand,
Interference fringes of the diffracted light of one of the two light beams by the diffraction grating formed on the substrate and the reflected light of the other of the two light beams or the transmitted light of one of the two light beams and the diffracted light of the other diffraction grating of the two light beams. The step of matching the direction of the diffraction grating of the substrate with the direction of the interference fringes formed on the substrate by the two light fluxes, thereby achieving the above object.

Further, according to the method of patterning a diffraction grating of the present invention, a photoresist is applied to the other surface of a processing substrate having a diffraction grating formed on one surface thereof, and a predetermined pitch whose orientation matches that of the diffraction grating. Is a method of patterning a diffraction grating by irradiating the photoresist with two light fluxes so that interference fringes are formed. A reference having a diffraction grating similar to the diffraction grating to be formed on one surface. The step of irradiating the substrate with the two light fluxes, the diffracted light of one of the two light fluxes of the diffraction grating of the reference substrate and the reflected light of the other of the two light fluxes, or the transmitted light of one of the two light fluxes and the other of the two light fluxes. Matching the azimuth of the diffraction grating of the reference substrate with the azimuth of the interference fringes formed on the reference substrate by the two light fluxes, based on the interference fringe with the diffracted light by the diffraction grating,
The grating azimuth detection light is made incident on the diffraction grating of the reference substrate in the plane where the two light beams are located, and the grating azimuth with respect to the diffraction grating is based on the position of the diffracted light of the grating azimuth detection light from the diffraction grating. Adjusting the incident angle of the detection light, arranging the processing substrate so that the grating orientation detection light is irradiated, and irradiating the diffraction grating on the processing substrate with the grating orientation detection light, Adjusting the azimuth of the diffraction grating based on the diffracted light from (1), thereby achieving the above object.

[0010]

According to the method of patterning a diffraction grating of the present invention, when the diffraction grating is formed by the two-beam interference fringes on the other surface of the substrate having the diffraction grating formed on one surface thereof,
Using the luminous flux interference fringes, the azimuth of the interference fringes and the azimuth of the diffraction grating formed in advance are matched. Then, the two-beam interference fringes are applied to the photoresist on the substrate to pattern the diffraction grating.

Further, with the reference substrate on which a diffraction grating similar to the one to be formed is formed, the orientation of the diffraction grating and the two-beam interference fringes is aligned, and the grating orientation is detected on the diffraction grating of the reference substrate. The light is adjusted to have a predetermined incident angle. After that, the processing substrate instead of the reference substrate is irradiated with the grating orientation detection light, and the orientation of the diffraction grating is adjusted so that the diffraction angle of the processing substrate becomes a predetermined incident angle. In this state, the two-beam interference fringes
The diffraction grating is patterned by irradiating the photoresist applied on the processing substrate.

[0012]

EXAMPLES The present invention will be described below with reference to examples. The diffraction grating patterning method of the present invention is carried out when forming a diffraction grating having the same orientation as that of the diffraction grating on the other surface of the transparent substrate having the diffraction grating formed on one surface. The method according to the invention is carried out, for example, by the device whose plan view is shown in FIG. This device manufactures a diffraction grating by utilizing two-beam interference fringes. The exposure apparatus is supported by a base 10 and is movable in a direction indicated by an arrow A in FIG. 1, and a rotary stage 11 mounted on the movable stage 15 so as to be rotatable and adjustable in height. And have. A processing substrate 14 on which a diffraction grating is to be formed and a reference substrate 12 on which a diffraction grating is formed at a predetermined grating pitch are detachably fixed to the rotary stage 11.

An exposure laser light source 40 for forming two-beam interference fringes is disposed on the side of the rotary stage 11. The exposure laser light source 40 irradiates the reflection mirror 43 with the Ar laser light 41 as coherent light via the electromagnetic shutter 42. The beam expander 44 increases the diameter of the light flux of the laser light reflected by the reflection mirror 43 and irradiates the half mirror 45 with the light. The half mirror 45 divides the emitted laser light 41 into a transmitted light 41a and a reflected light 41b.
The transmitted light 41a is reflected by the first reflecting mirror 46 and is radiated onto the rotary stage 11. Further, the laser light 41b reflected by the half mirror 45 is also reflected by the second reflecting mirror 47 and irradiated on the rotary stage 11. The laser light reflected by each of the reflection mirrors 46 and 47 is applied to, for example, the reference substrate 12 or the processing substrate 14 fixed on the rotating stage 11 to form an interference fringe on the reference substrate 12 or the processing substrate 14. To do. In order that the interference fringes formed on the processing substrate 14 match the orientation of the diffraction grating to be patterned,
The relative position between the exposure laser light source 40 and the rotary stage 11,
It is adjusted by the reference board 12. When the processing substrate 14 coated with the photoresist is fixed on the rotary stage 11, interference fringes are formed on the photoresist to pattern the diffraction grating.

As described above, the laser beams 41a and 41b split by the half mirror 45 form interference fringes on the reference substrate 12 or the processing substrate 14 fixed on the rotating stage 11. Part of the light 41a or 41b is diffracted by the diffraction grating of the reference substrate 12 or the processing substrate 14.
At this time, as shown in FIG. 2, the reflected light 41a ′ of the one laser light 41a and the reflected diffracted light 41b ′ of the other laser light interfere with each other and are irradiated onto the reflection mirror 47, and the interference light is Two
The light is reflected by the reflection mirror 47 and is projected onto the screen 50 via the half mirror 45. Therefore, the screen 50
An interference fringe formed by the interference of the reflected light 41a ′ of the laser light 41a and the reflected diffracted light 41b ′ of the laser light 41b is projected on the top.

The rotating stage 11 is irradiated with He--Ne laser light 31 as azimuth detecting coherent light emitted from the azimuth detecting laser light source 30.
The grating azimuth detection light 31 emitted from the azimuth detection laser light source 30 is located in the same plane as the laser light 41a and 41b emitted from the exposure laser light source 40 and split by the half mirror 45, Laser light 31 is a half mirror
Reference substrate fixed on the rotary stage 11 through 32.
12 or the processing substrate 14 is irradiated.
The laser light source for azimuth detection 30 is adjusted so that the emitted grating azimuth detection light 31 enters the diffraction grating of the reference substrate 12 or the processing substrate 14 fixed on the rotating stage 11 at a Bragg angle. To be done. Reference board 12 or processing board 14
When the grating azimuth detection light 31 is incident on the diffraction grating of 1 at the Bragg angle, the reflected diffracted light follows the same optical path as the incident light. A half mirror 32 is interposed in the optical path of the grating azimuth detection light 31 emitted from the azimuth detection laser light source 30, and the reflected diffraction light by the diffraction grating of the reference substrate 12 or the processing substrate 14 is the half mirror. It is reflected by 32 and received by the position detector 33. The position detector 33
Is adapted to detect the position of the received laser light, and the direction of the emitted light by the azimuth detecting laser light source 30 is finely adjusted based on the position, and is a reference fixed on the rotary stage 11. The laser light 31 is made to enter the diffraction grating of the substrate 12 or the processing substrate 14 at a Bragg angle.

In general, as shown in FIG. 3A, the laser light 61 incident on the diffraction grating 63 is diffracted by the diffraction grating 63 and transmitted (diffracted light) 61a and transmitted light 61b.
It is divided into reflected diffracted light (reflected diffracted light) 61c and reflected light 61d.

As for the light transmitted through the substrate,
The diffraction direction of the diffracted light 61a is determined by the relative angle with respect to the azimuth of the diffraction grating 63 and the incident laser light 61.
As shown in (b), when the incident laser light 61 is located in a plane perpendicular to the direction of the diffraction grating 63, the diffracted light
61a and transmitted light 61b are located in the vertical plane. However, as shown in FIG. 3C, even if the incident laser light is in a state of being deviated from the vertical plane with respect to the azimuth of the diffraction grating 63, the diffracted light 61 a ′ is relative to the azimuth of the diffraction grating 63. Located in orthogonal planes. Regarding the light reflected on the substrate, the reflected diffracted light 61c corresponds to the diffracted light 61a, and the incident laser light 61 is reflected by the diffraction grating 63.
The reflected diffracted light 61c ′ is positioned in a plane orthogonal to the azimuth of the grating of the diffraction grating 63 even if the reflected diffracted light 61c ′ is displaced from the vertical plane with respect to the azimuth.

Therefore, when the incident laser beam 61 is in a plane deviated from the plane orthogonal to the azimuth of the diffraction grating,
The diffracted light 61a 'and the reflected diffracted light 61c' will change according to the deviation. This also applies to Bragg diffraction, and even if the incident laser light 61 is slightly deviated from the plane perpendicular to the grating direction of the diffraction grating 63, the direction of the light corresponds to the deviation.

The position detector 33 detects the position of the reflected diffracted light of the diffraction grating in the optical path of the light incident on the diffraction grating of the reference substrate 12, and therefore the position detector 33 Direction based laser light source based on the detection result of
It is possible to detect the deviation of the orientation of the diffraction grating with respect to the grating orientation detection light 31 emitted from 30.

A He--Ne laser beam 21 emitted from a tilt detecting laser light source 20 is provided on the rotary stage 11 in order to detect the tilt of the reference substrate 12 and the processing substrate 14 fixed on the rotary stage 11. Is being irradiated. The laser light 21 reflected by the reference substrate 12 or the processing substrate 14 is received by the tilt detector 22. The tilt detector 22 is a tilt degree of the received laser beam, that is, a reference substrate fixed on the rotary stage 11.
The tilted state of 12 or the processing substrate 14 is detected.

With such an apparatus, the method for forming a diffraction grating of the present invention is carried out. For example, when forming a diffraction grating having the same azimuth as that of the diffraction grating at the same pitch on the other surface of the processing substrate 14 having the diffraction grating formed on one surface, first, the processing substrate 14 is formed. A reference substrate 12 having a diffraction grating similar to a power diffraction grating is prepared. Then, as shown in FIG.
The surface on which is formed is fixed so as to be in close contact with the rotary stage 11. In this state, the exposure laser light source 40
When the laser light 41 is emitted, the two beams 41a and 41b split by the half mirror 45 are applied to the reference substrate 12 to form interference fringes (exposure pattern). At this time, the interference light between the reflected light 41a ′ of the one laser beam 41a by the diffraction grating 13 and the reflected diffracted light 41b ′ of the other laser beam 41b is
Interference fringes are formed on the screen 50 by being projected on the screen 50. The interference fringes formed on the screen 50 are the diffraction gratings previously provided on the reference substrate 12 and the reference substrate.
The reference substrate by the two laser beams radiated on 12
When the azimuths of the interference fringes formed on 12 coincide with each other, the striped pattern disappears. However, when the azimuths of the two are deviated, as shown in FIG. On arrow B
A striped pattern occurs in the direction of the lattice direction indicated by. Therefore, if the rotary stage 11 to which the reference substrate 12 is fixed is rotated so that interference fringes on the screen 50 are not generated, the diffraction grating 13 on the reference substrate 12 and the exposure laser light source
The azimuth of the interference pattern (exposure pattern) by the two laser beams that are irradiated from 40 and divided is in a state of being coincident with each other.

In this case, the accuracy of orientation adjustment is based on the reference substrate.
Although it depends on the size of the diffraction grating formed on the screen 12, one cycle of the interference fringes formed on the screen 50 corresponds to the shift of half the wavelength of the exposure laser light, and thus interference occurs within the range of 4 mm. By adjusting the stripes to be one cycle or less, the rotation angle of the reference substrate 12 is aligned within 20 ".

At this time, while the laser beam 41 is being emitted from the exposure laser light source 40, the laser light source for tilt detection is used.
He-Ne laser light 21 is emitted from 20. The laser light
21 is reflected by the reference substrate 12 and is captured by the inclination detector 22, and the inclination detector 22 detects the inclination state of the reference substrate 12.

FIG. 4B shows the case where the interference fringes formed on the screen 50 are formed along the grating direction B of the diffraction grating 13 of the reference substrate 12. In this case, the diffraction grating is formed. There is a pitch difference between 13 and the interference fringes of the two laser beams incident on the reference substrate 12, that is, the incident angle of the laser beam deviates from the Bragg angle. In such a case, the pitch difference becomes 1 angstrom or less by adjusting so that interference fringes of 1 cycle or less are formed within the range of 10 mm. By utilizing this fact, the deviation of the Bragg angle of the two laser beams incident on the reference substrate 12 from the exposure laser light source 40 can be checked by using the reference substrate 12 having the diffraction grating formed on one surface.

Based on the laser beam from the exposure laser light source 40, the orientation of the diffraction grating of the reference substrate 12 is brought into a state of being matched with the exposure pattern by the laser beam, and
When the tilt state of the reference substrate 12 is detected by the tilt detector 22, after that, from the azimuth detecting laser light source 30, the He-
The direction detection light 31 which is a Ne laser light is applied to the reference substrate 12 on the rotary stage 11. At this time, the direction detection light 31
Is adjusted based on the position of the reflected diffracted light detected by the position detector 33 so that it enters the diffraction grating 13 of the reference substrate 12 at the Bragg angle.

In this way, the orientation of the diffraction grating 13 of the reference substrate 12 is matched with the orientation of the interference fringes formed by the exposure laser light 41, and the tilt state is detected by the laser light source 20 for tilt detection. At the same time, the azimuth detecting light 31 emitted from the azimuth detecting laser light source 30 enters the diffraction grating 13 of the reference substrate 12 at a Bragg angle.

In this state, the reference substrate 12 is removed from the rotary stage 11, and the processing substrate 14 having a diffraction grating formed on one surface and a photoresist applied on the other surface is fixed. To be done. Then, the He-Ne laser light 21 is emitted from the laser light source 20 for tilt detection to the processing substrate 14, and the tilted state of the processing substrate 14 is the above-mentioned reference substrate.
The tilted state of the rotary stage 11 is adjusted based on the detection result of the tilt detector 22 so as to be equal to the tilted state of 12. In addition, the direction detection light is emitted from the direction detection laser light source 30.
The rotating stage 11 is rotated so that the intensity of the reflected diffracted light that is emitted from the processing substrate 14 and reflected by the diffraction grating of the processing substrate 14 and captured by the position detector 33 is maximized. As described above, the azimuth detection light emitted from the azimuth detection laser light source 30 is adjusted so that the azimuth detection light is incident on the diffraction grating of the reference substrate 12 fixed on the rotating stage 11 at a Bragg angle. Therefore, when the rotation stage 11 is rotationally adjusted based on the position on the position detector 33 of the reflected diffracted light of the processing substrate 14 fixed on the rotation stage 11 instead of the reference substrate 12,
The diffraction grating of the processing substrate 14 fixed on the rotary stage 11 matches the azimuth of the reference substrate 12 fixed to the rotary stage 11 in the previous step with respect to the grating azimuth detection light 31 of the azimuth detecting laser light source 30. It will be in the state of doing. As a result, the diffraction grating previously formed on the processing substrate 14 is the laser light source for exposure.
The azimuth coincides with the interference fringes of the exposure pattern of 40.

In this case, the laser light emitted from the azimuth detecting laser light source 30 and the tilt detecting laser light source 20 is a He—Ne laser light having a different wavelength from the Ar laser light emitted from the exposure laser light source 40. Because there is a processing substrate
There is no risk that the photoresist applied to 14 will be exposed to the He-Ne laser light.

In this way, when the processing substrate 14 is oriented in a predetermined direction on the rotary stage 11, laser light 41 is emitted from the exposure laser light source 40. The exposure laser light source
The laser beam 41 emitted from 40 is divided into two and emitted so as to form interference fringes on the reference substrate 12 and the processing substrate 14. At this time, since the azimuth of the diffraction grating previously formed on the processing substrate 14 is in a state of being matched with the azimuth of the interference fringes formed on the processing substrate 14, the interference fringes are processed. By irradiating the photoresist applied on the substrate 14 for use, the diffraction grating whose azimuth coincides with that of the previously formed diffraction grating is patterned.

In the above embodiment, the laser light source for exposure is used.
When adjusting the orientation of the exposure pattern by 40, a reference substrate on which a predetermined diffraction grating is formed in advance is used, and after adjusting the orientation of the exposure pattern, the processing substrate 14 is fixed on the rotary stage 11. However, instead of using such a reference substrate 12, the processing substrate 14 on one side of which the diffraction grating is formed in advance may be directly used while the photoresist is applied on the other side thereof. In this case, when adjusting the orientation of the exposure pattern and the diffraction grating formed in advance, part of the photoresist is affected by the projection of the exposure pattern, but the orientation of the diffraction grating is adjusted by the reference substrate. Since it is not necessary to form the diffraction grating, the formation of the diffraction grating is facilitated, and the accuracy of alignment of the diffraction grating is also improved.

Note that these adjustments are not limited to the light emitted in the reflection direction of the front surface of the substrate. The same can be done by utilizing the light emitted to the rear side (transmission direction side) of the transparent substrate.

[0032]

As described above, according to the method of patterning a diffraction grating of the present invention, the azimuth of the diffraction grating formed on the substrate and the azimuth of the interference fringe are directly positioned by using the interference fringe that is the exposure pattern. Since they are aligned with each other, the diffraction grating having the same orientation can be patterned on the other surface with high accuracy and in a short time on the substrate having the diffraction grating formed on one surface.

[Brief description of drawings]

FIG. 1 is a schematic plan view of an apparatus used for carrying out the method for forming a diffraction grating of the present invention.

FIG. 2 is a sectional view for explaining a diffraction state of a reference substrate used in the manufacturing apparatus.

FIG. 3A is a sectional view for explaining states of incident light, diffracted light, and transmitted light with respect to a diffraction grating. FIG. 6B is a plan view for explaining states of diffracted light and transmitted light when incident light is located in a plane perpendicular to the diffraction grating.
FIG. 7C is a plan view for explaining states of reflected light and transmitted light when incident light is not located in a plane perpendicular to the diffraction grating.

4A and 4B are diagrams showing an example of interference fringes projected on a screen.

[Explanation of symbols]

 10 Base 11 Rotating stage 12 Reference substrate 14 Processing substrate 20 Laser light source for tilt adjustment 30 Laser light source for orientation detection 33 Position detector 40 Laser light source for exposure 50 Screen

Front page continued (72) Inventor Yukio Kurata 22-22 Nagaikecho, Abeno-ku, Osaka

Claims (2)

[Claims] 1. A photoresist is applied on the other surface of a substrate having a diffraction grating formed on one surface thereof so that interference fringes having a predetermined pitch whose orientation matches that of the diffraction grating are formed.
A method of patterning a diffraction grating by irradiating the photoresist with a light beam, the method comprising: irradiating the surface of the substrate on which the photoresist is coated with the two light fluxes to form a diffraction grating formed on the substrate. Based on the interference fringes of the diffracted light of one of the light fluxes and the reflected light of the other of the two light fluxes or the transmitted light of one of the two light fluxes and the diffracted light of the other diffraction grating of the two light fluxes, A method of patterning a diffraction grating, including the step of matching the azimuth with the azimuth of interference fringes formed on the substrate by the two light fluxes. 2. A photoresist is applied to the other surface of a processing substrate having a diffraction grating formed on one surface thereof so that interference fringes having a predetermined pitch whose direction matches that of the diffraction grating are formed. A method of patterning a diffraction grating by irradiating the photoresist with a light flux, the method comprising irradiating the reference substrate having a diffraction grating similar to a diffraction grating to be formed on one surface with the two light fluxes. An interference fringe of the diffracted light of one of the two light beams by the diffraction grating of the reference substrate and the reflected light of the other of the two light beams or the transmitted light of one of the two light beams and the diffracted light of the other diffraction grating of the two light beams. The step of matching the direction of the diffraction grating of the reference substrate with the direction of the interference fringes formed on the reference substrate by the two light beams, and the diffraction grating of the reference substrate in the plane where the two light beams are located. To A step of injecting the child azimuth detection light, and adjusting the incident angle of the grating azimuth detection light with respect to the diffraction grating based on the position of the diffraction light of the grating azimuth detection light from the diffraction grating; The processing substrate so that the processing substrate is positioned so that the diffraction grating on the processing substrate is irradiated with the grating orientation detection light, and the orientation of the diffraction grating is adjusted based on the diffraction light from the diffraction grating. And a diffraction grating patterning method including: