JPH07120781A - Production of optical writing type spacial optical modulating element - Google Patents

Abstract

PURPOSE:To obtain a reproduced picture of high picture qualities without irregu lar sensitivity or resolution by forming a hydrogenated amorphous silicon film on a transparent substrate by plasma CVD method, grinding the surface of the hydrogenated amorphous silicon film deposited on the transparent substrate to obtain a parallel plane of the film to the substrate plane, and then using the obtd. film. CONSTITUTION:A hydrogenated amorphous silicon film is formed on a substrate by plasma CVD method at specified substrate temp. under conditions of 15 sccm SiH4 gas, 60 sccm H2 gas, <=1.0PPm flow rate ratio of SiH4 gas to B2F6 gas, and 133 Pa gas pressure. The substrate used is a transparent substrate on which a transparent electrode is formed. The transparent substrate is a glass plate having both surfaces optically flat and parallel to each other and having an almost same coefft. of thermal expansion as the coefft. of thermal expansion of the hydrogenated amorphous silicon film. Further, the hydrogenated amorphous silicon film formed on the substrate is ground to have a parallel plane to the substrate plane.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing an optical writing type spatial light modulator used as a constituent element in a display device, an image pickup device, an optical computer and the like.

[0002]

2. Description of the Related Art For example, in order to obtain image information having high definition in a display device or an image pickup device, it is necessary to obtain high resolution image information as a constituent element of the display device or the image pickup device. It is necessary to use a constituent element that can be used, but as one of the elements that can obtain the high-resolution image information, an optical writing type spatial light modulator is drawing attention. FIG. 1 shows the above-mentioned optical writing type spatial light modulator SL.
1 shows an example of the structure of the M. The optical writing type spatial light modulator SLM shown in FIG. 1 includes a transparent substrate BP1, a transparent electrode Et1, a photoconductive layer member PCL, a dielectric mirror DML.
, Light modulation material layer member PML, transparent electrode Et2, transparent substrate BP
It is configured by stacking 2 and.

The transparent electrodes Et1 and Et2 are composed of a thin film of a transparent conductive material, and the photoconductive layer member PCL is composed of a material exhibiting photoconductivity in the wavelength range of the light used, and further, a dielectric. As the body mirror DML, a well-known type configured as a multilayer film so as to be able to reflect light of a predetermined wavelength band can be used, and further, the light modulation material layer member PML.
Is a light modulator (for example, nematic liquid crystal, lithium niobate, which changes the state of light (state of polarization of light, state of rotation of light, state of scattering of light) according to the strength of the applied electric field.
BSO, PLZT, polymer-liquid crystal composite film, etc.). Reference numeral E in FIG. 1 denotes a power source for applying a predetermined voltage between the transparent electrodes Et1 and Et2, and this power source E is shown as an AC power source in the figure, but the power source E of the light modulation material layer member PML is shown. Depending on the constituent material, it can be used as a DC power supply or an AC power supply.

Further, WL in the drawing is the writing light which is incident from the substrate BP1 side in the optical writing type spatial light modulator SLM and is condensed on the photoconductive layer member PCL, and this writing light WL is the object of display. The intensity is modulated according to the information stored in. The writing light WL whose intensity is modulated by image information is incident from the transparent substrate Et1 side of the optical writing type spatial light modulator SLM in which a predetermined voltage is supplied from the power source E between the transparent electrodes Et1 and Et2, and is transparent. Through the substrate BP1 and the transparent electrode Et1, the photoconductive layer member P
When the light is condensed on CL, the electric resistance value of the photoconductive layer member PCL at the part where the writing light WL is condensed changes according to the amount of the irradiated light, and both ends of the light modulation material layer member PML are changed. An electric field showing an electric field intensity distribution corresponding to the above-mentioned image information is applied to.

Therefore, the optical writing type spatial light modulator SLM is used.
When the read light RL is made incident from the transparent substrate BP2 side in the above, the read light RL is changed to the transparent substrate BP2 → the electrode Et2 →
The light modulation material layer member PML → reaches the dielectric mirror DML by the path of the dielectric mirror DML and is reflected there, and the reflected light of the read light is the dielectric mirror DML → light modulation material layer member PML.
The light is emitted from the optical writing type spatial light modulator SLM along the path of the electrode Et2, the transparent substrate BP2, and the like. The light flux emitted from the optical writing type spatial light modulator SLM as described above is applied with an electric field having an electric field intensity distribution corresponding to the image information of the writing light WL. Since the light flux is a light flux that travels back and forth through the member PML, the light flux of the read light has its light state changed corresponding to the image information of the writing light.

The constituent material of the light modulation material layer member PML in the optical writing type spatial light modulation element SLM is such that (1) the scattering state of light passing therethrough is changed according to the electric field strength applied thereto. If there is, the reflected light flux of the reading light emitted from the optical writing type spatial light modulator SLM as described above is in a state in which the intensity of the light changes corresponding to the image information of the writing light. In addition, the constituent material of the light modulating material layer member PML in the optical writing type spatial light modulating element SLM is (2) the polarization state of light passing therethrough according to the electric field strength applied thereto, Alternatively, when the state of birefringence is changed, the reflected light flux of the reading light emitted from the optical writing type spatial light modulator SLM as described above corresponds to the image information of the writing light. The state of polarization, Alternatively, the state of the polarization plane is changed. In the case of the above (2), the light flux emitted from the optical writing type spatial light modulator SLM is passed through the analyzer (the same applies to the polarization beam splitter PBS) to emit the optical writing type spatial light modulator SLM. The reflected light flux of the reading light can be in a state in which the light intensity changes corresponding to the image information of the writing light.

[0007]

By the way, the characteristics of the photoconductive layer member PCL used as a constituent member of the above-mentioned optical writing type spatial light modulator SLM are as follows.
This greatly affects various characteristics such as sensitivity and resolution of the optical writing type spatial light modulator SLM. As described above, the photoconductive layer member PCL provided in the optical write type spatial light modulator SLM has an electric resistance value that changes according to the intensity distribution of the write light incident on the optical write type spatial light modulator SLM. By this, the electric field intensity distribution corresponding to the intensity distribution of the writing light can be given to the light modulation material layer member PML. Although a material having high sensitivity must be selected and used, the photoconductive layer member PCL should have a structure showing high sensitivity and high resolution characteristics. Causes an increase in sensitivity and a decrease in resolution, and conversely to the above, when the film thickness thereof is reduced, a decrease in sensitivity and an improvement in resolution occur.

The photoconductive layer member PCL as described above
Since the change in the film thickness changes the sensitivity and the resolution, if there is unevenness in the thickness of the photoconductive layer member PCL provided in the photo-writing type spatial light modulator SLM, the unevenness in thickness is dealt with. Then the sensitivity and resolution will change,
The image read from the optical writing type spatial light modulator SLM has shading in both brightness and definition. Therefore, in the construction of the photoconductive layer member PCL in the photo-writing type spatial light modulator SLM, it is necessary to select and use a photoconductive material exhibiting high sensitivity so as to make the entire thickness thereof constant. The photoconductive layer member PC of the above-mentioned optical writing type spatial light modulator SLM
In order to make L highly sensitive, in recent years, a photoconductive layer member PCL has been made of a hydrogenated amorphous silicon film.

By the way, when the highly sensitive photoconductive layer member PCL is made of the hydrogenated amorphous silicon film as described above, the temperature of the transparent substrate during the deposition of the hydrogenated amorphous silicon film is set to a predetermined high temperature. It is necessary to keep it. After the step of depositing and forming the hydrogenated amorphous silicon film on the transparent substrate in the predetermined high temperature state as described above, the temperature of the transparent substrate and the hydrogenated amorphous silicon film is lowered to room temperature. However, since the optical glass BK7 has been conventionally used as the transparent substrate, the coefficient of thermal expansion of the optical glass BK7 used as the substrate (1 degree Celsius)
80 times 10 minus 7 powers per degree) and the thermal expansion coefficient of the hydrogenated amorphous silicon film deposited on the transparent substrate (36 times 10 minus 7 powers per degree Celsius)
Therefore, if the plate thickness of the transparent substrate is large, the hydrogenated amorphous silicon film may peel off from the transparent substrate. Although used, when the above-mentioned transparent substrate is thin, both of them may be bent together with the hydrogenated amorphous silicon film attached to the transparent substrate.

As described above, the coefficient of thermal expansion of the transparent substrate,
When the hydrogenated amorphous silicon film deposited on the transparent substrate has a large coefficient of thermal expansion, and the hydrogenated amorphous silicon film is deposited on the thin transparent substrate, the temperature changes and the two bend together. The problem is
For example, as disclosed in Japanese Unexamined Patent Publication No. Hei 3-261918, for example, by applying a polishing means or a heating molding means, to a curved shape generated on the transparent substrate and the hydrogenated amorphous silicon film when the temperature changes. Then, a proposal is made to prepare a transparent substrate which is bent in the opposite shape in advance, and deposit the hydrogenated amorphous silicon film by heating the transparent substrate to a predetermined high temperature. There is. According to the proposal disclosed in the above publication, the temperature of the transparent substrate and the temperature of the hydrogenated amorphous silicon film are lowered to room temperature in the state where the hydrogenated amorphous silicon film is attached to the transparent substrate. In this state, the surfaces of the transparent substrate and the hydrogenated amorphous silicon film can be flattened. However, even if the above-mentioned proposal is carried out, the flatness of the transparent substrate obtained by the proposal has a limit, for example, 50 m.
0.5 μm for a glass substrate with m-square and thickness of 1 mm
There is a problem that it is difficult to stably obtain the following flatness.

Further, when the hydrogenated amorphous silicon film is deposited on the transparent substrate, the film thickness of the hydrogenated amorphous silicon film deposited on the surface of the transparent substrate is not uniform over the entire surface, and is, for example, 50 mm. When a hydrogenated amorphous silicon film having an average film thickness of 20 μm is adhered and formed on a square glass plate, the film thickness variation is 1
Exists at μm or more. If there is variation in the film thickness distribution of the hydrogenated amorphous silicon film deposited and formed on the transparent substrate, uneven sensitivity and uneven resolution occur due to the reasons described above. Even if the reading light is made incident and the image information is read, a high-quality reproduced image cannot be obtained, so an improvement measure for it is required.

[0012]

According to the present invention, there is provided an optical writing type in which a plurality of members including at least a photoconductive layer member and a light modulation material layer member are laminated between transparent substrates having transparent electrodes attached thereto. In manufacturing a photo-writing type spatial light modulator in which a hydrogenated amorphous silicon film is used as the photoconductive layer member in the spatial light modulator, the substrate on which the hydrogenated amorphous silicon film is to be deposited is set to a predetermined temperature, 15 sccm of SiH4 gas and 60 sccc of H2 gas
m, flow rate ratio of B2H6 gas to SiH4 gas is 1.0P
When a hydrogenated amorphous silicon film is formed on the above-mentioned substrate by a plasma CVD method in an atmosphere of Pm or less and a gas pressure of 133 Pa, the both sides of the substrate are parallel optical planes, and
A transparent substrate made of glass having a thermal expansion coefficient similar to that of the hydrogenated amorphous silicon film is used, and a transparent electrode is attached to the transparent substrate.
Provided is a method of manufacturing an optical writing type spatial light modulator, which comprises a step of polishing the surface of a hydrogenated amorphous silicon film deposited on a substrate so as to be parallel to the surface of the substrate.

[0013]

[Function] SiO2 is 80.9 wt%, B2O3 is 12.7 wt%
%, Al2O2 is 2.3 wt%, Fe2O3 is 0.03 wt%
%, Na2O is 4.0 wt% and K2O is 0.04 wt%, an electrode made of a transparent conductive film is attached on one surface of a transparent substrate, which is an optical plane whose front and back surfaces are parallel to each other. . The transparent substrate is heated to 220 degrees Celsius and kept at that temperature, and the SiH4 gas is 15 scc.
m, H2 gas is 60 sccm, B2H for SiH4 gas
Flow rate ratio of 6 gas is less than 1.0PPm, gas pressure is 133Pa
In the atmosphere, the hydrogenated amorphous silicon film having a film thickness of 20 μm is formed by the plasma CVD method. There is a large difference between the coefficient of thermal expansion of a transparent substrate made of glass having the above-mentioned composition and the coefficient of thermal expansion of a hydrogenated amorphous silicon film having a thickness of 20 micrometers deposited and formed on the transparent substrate under the above conditions. Therefore, even if the transparent substrate on which the hydrogenated amorphous silicon film is adhered and formed is brought to room temperature, both front and back surfaces remain parallel planes. Next, the surface of the hydrogenated amorphous silicon film adhered and formed on the transparent substrate is polished in parallel with the surface of the transparent substrate by the pitch polishing method using cerium oxide as abrasive grains and pitch as a polisher. As a result, the hydrogenated amorphous silicon film deposited and formed on the transparent substrate has a uniform film thickness distribution, which eliminates uneven sensitivity and uneven resolution.
When read light is made incident on the optical writing type spatial light modulator to read the image information, a reproduced image of high quality can be obtained.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The concrete contents of the method for manufacturing the optical writing type spatial light modulator of the present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 is a side cross-sectional view showing an example of the structure of an optical writing type spatial light modulator, and FIG. 2 is a difference between the coefficient of thermal expansion of a glass substrate to which a hydrogenated amorphous silicon film is attached and the coefficient of thermal expansion of a hydrogenated amorphous silicon film. FIG. 4 is a diagram showing the relationship between the hydrogenated amorphous silicon film and the flatness of the hydrogenated amorphous silicon film. In the method of manufacturing the optical writing type spatial light modulator of the present invention, first, SiO 2 is 8
0.9 wt%, B2O3 12.7 wt%, Al2O2 2.
3wt%, Fe2O3 0.03wt%, Na2O 4.0
A transparent substrate (corresponding to the transparent substrate BP1 in FIG. 1) in which both front and back surfaces are parallel optical planes is made from a glass plate having a composition of wt% and K2O of 0.04 wt%. As described above, the transparent substrate having the front and back surfaces as parallel optical planes has a SiO2 content of 80.9 wt% and a B2O3 content of 12.7 wt%.
%, Al2O2 is 2.3 wt%, Fe2O3 is 0.03 wt%
%, Na2O is 4.0 wt% and K2O is 0.04 wt%. Good results can be obtained by polishing the surface of the glass plate by the pitch polishing method, using cerium oxide as the abrasive grains and pitch as the polisher, and performing the polishing step.

Next, a transparent electrode made of a transparent conductive film on one surface of the transparent substrate (corresponding to the transparent electrode Et1 in FIG. 1).
Make something with attached. As the transparent electrode, for example, an ITO film can be formed on the transparent substrate surface by applying a vacuum deposition method or a sputtering method. As described above, the transparent substrate in which the transparent electrode made of the transparent conductive film is attached to one surface of the transparent substrate is placed in a vacuum container, and the inside of the vacuum container is evacuated to a predetermined vacuum degree. Then, the transparent substrate was heated to 220 ° C. and kept at that temperature, and then 15 sccc of SiH 4 gas was added to the vacuum vessel.
m, H2 gas is 60 sccm, B2H for SiH4 gas
The hydrogenated amorphous silicon film with a thickness of 20 μm was formed on the transparent substrate by plasma CVD in an atmosphere in which the gas was flowed at a flow rate ratio of 6 gas of 1.0 PPm or less and the gas pressure was 133 Pa. To form. To deposit and form a hydrogenated amorphous silicon film on a transparent substrate, a plasma CVD device (model number PED301) manufactured by Nichiden Anelva Co., Ltd. was used. When a hydrogenated amorphous silicon film was formed on the top, a hydrogenated amorphous silicon film with good sensitivity could be obtained.

When the distance between the electrodes is set to 25 mm, which is shorter than 35 mm, using the plasma CVD apparatus described above, the temperature of the transparent substrate is set to 180 ° C., which is lower than 220 ° C., and SiH 4 gas is placed in the vacuum container. Is 15 scc
m, H2 gas is 60 sccm, B2H for SiH4 gas
The hydrogenated amorphous silicon film with a thickness of 20 μm was formed on the transparent substrate by plasma CVD in an atmosphere in which the gas was flowed at a flow rate ratio of 6 gas of 1.0 PPm or less and the gas pressure was 133 Pa. However, the hydrogenated amorphous silicon film obtained in this case is more sensitive than the hydrogenated amorphous silicon film manufactured under the condition that the distance between the electrodes is 35 mm and the temperature of the transparent substrate is 220 ° C. as described above. Was low. The true stress considered to be generated in the process of forming the hydrogenated amorphous silicon film can be brought close to 0 by optimizing the film forming conditions. Therefore, the true stress at the interface between the transparent substrate and the hydrogenated amorphous silicon film is By making the generated internal stress close to 0, the curvature (warpage) can be suppressed to 0.1 μm or less regardless of the thickness of the transparent substrate, and the hydrogenated amorphous silicon film can be prevented from peeling off. .

As described above, the transparent substrate on which the hydrogenated amorphous silicon film having a predetermined thickness of 20 μm is adhered is gradually cooled and then taken out into the atmosphere and polished. In the polishing step, for example, cerium oxide is used as abrasive grains, pitch is used as a polisher, and the surface of the hydrogenated amorphous silicon film adhered and formed on the transparent substrate by the pitch polishing method is used. Polishing parallel to the surface gives good results. The thickness variation of the hydrogenated amorphous silicon film due to the above-mentioned polishing step is about 1 μm which was present before the polishing was performed, and the thickness variation of the hydrogenated amorphous silicon film was about 0 μm after the polishing step. The variation is improved to 3 μm or less. In the optical write type spatial light modulator shown in FIG. 1, the hydrogenated amorphous silicon film corresponding to the photoconductive layer member shown as PCL has the sequential constituent members shown in FIG. By stacking the dielectric mirror DML, the light modulation material layer member PML, the transparent electrode Et2, and the transparent substrate BP2, an optical writing type spatial light modulation element is manufactured. In the optical writing type spatial light modulator illustrated in FIG. 1, the light shielding layer for preventing the writing light from going to the reading side is not provided, but the light shielding layer may be provided. Further, when the light modulation material layer member PML in the optical writing type spatial light modulation element illustrated in FIG. 1 is formed by using, for example, liquid crystal, an alignment layer is provided or a seal member is provided. Needless to say. When the optical writing type spatial light modulating element manufactured according to the manufacturing method of the present invention is compared with the conventional optical writing type spatial light modulating element, the differences shown in Table 1 below are obtained.

[0018]

[Table 1]

In the conventional optical writing type spatial light modulator shown in Table 1, the glass used as the transparent substrate is the optical glass BK7, and its thermal expansion coefficient (1 degree Celsius).
80 times 10 minus 7 powers per degree) is the coefficient of thermal expansion of the hydrogenated amorphous silicon film deposited on the transparent substrate (36 times 10 minus 7 per degree Celsius).
The difference between the transparent substrate made of the optical glass BK7 and the hydrogenated amorphous silicon film used as the photoconductive layer member PCL is large as shown in FIG. The stress is generated, and the transparent substrate 2
A large curvature (warp) of 4 μm occurs. Further, in the conventional optical writing type spatial light modulator, since the thickness of the hydrogenated amorphous silicon film attached to the transparent substrate varies by about 1 μm, a large curvature of 2 to 4 μm existing on the transparent substrate. Along with (warpage), large shading occurs in the reproduced image.

Looking at the contents of "Table 1" showing the comparison result of the optical writing type spatial light modulating element manufactured according to the manufacturing method of the present invention and the conventional optical writing type spatial light modulating element, It is apparent that the optical writing type spatial light modulator manufactured by the manufacturing method of 1. has excellent characteristics as compared with the conventional optical writing type spatial light modulator. In the optical writing type spatial light modulator manufactured according to the manufacturing method of the present invention, there is no difference between the coefficient of thermal expansion of the transparent substrate and the coefficient of thermal expansion of the hydrogenated amorphous silicon film deposited and formed on the transparent substrate. Even if the temperature of the transparent substrate on which the hydrogenated amorphous silicon film has been adhered and formed is lowered to room temperature, both the front and back surfaces are parallel flat surfaces. Since the film thickness distribution of the hydrogenated amorphous silicon film is made uniform by polishing, unevenness in sensitivity and unevenness in resolution do not occur, and therefore a high-quality reproduced image with no shading can be obtained. The element can be easily manufactured.

[0021]

As is clear from the above description, in the method for manufacturing the optical addressing spatial light modulator of the present invention, SiO2 is 80.9 wt%, B2O3 is 12.7 wt%, A
2.3 wt% of l2O2, 0.03 wt% of Fe2O3, Na
An electrode made of a transparent conductive film is attached to one surface of a transparent substrate, which is an optical plane whose front and back surfaces are parallel to each other, by using glass having a composition of 2O 4.0% by weight and K 2 O 0.04% by weight. An atmosphere in which the transparent substrate is heated to 220 degrees Celsius and kept at that temperature, the SiH4 gas is 15 sccm, the H2 gas is 60 sccm, the flow rate ratio of the B2H6 gas to the SiH4 gas is 1.0 PPm or less, and the gas pressure is 133 Pa. In the above, after the hydrogenated amorphous silicon film is formed by the plasma CVD method, the surface of the hydrogenated amorphous silicon film adhered and formed on the transparent substrate is polished in parallel with the surface of the transparent substrate described above. By configuring the optical writing type spatial light modulator using the above, the coefficient of thermal expansion of the transparent substrate made of glass having the above-mentioned composition and the above Since there is no great difference in the coefficient of thermal expansion of the hydrogenated amorphous silicon film having a film thickness of 20 micrometers deposited and formed on the transparent substrate depending on the circumstances, it is transparent in the state where the hydrogenated amorphous silicon film is deposited and formed. Even if the temperature of the substrate is lowered to room temperature, both front and back surfaces are parallel flat surfaces, and the film thickness distribution of the hydrogenated amorphous silicon film deposited and formed on the transparent substrate is constant. It is possible to easily manufacture an optical writing type spatial light modulator that can obtain a high-quality reproduced image by causing read light to enter without causing uneven sensitivity or uneven resolution.

[Brief description of drawings]

FIG. 1 is a side sectional view showing an example configuration of an optical writing type spatial light modulator.

FIG. 2 is a diagram showing the relationship between the difference between the coefficient of thermal expansion of a glass substrate having a hydrogenated amorphous silicon film attached thereto and the coefficient of thermal expansion of a hydrogenated amorphous silicon film and the flatness of the hydrogenated amorphous silicon film. .

[Explanation of symbols]

SLM ... Optical writing type spatial light modulator, BP1, BP2 ... Transparent substrate, Et1, Et2 ... Transparent electrode, PCL ... Photoconductive layer member, DML ... Dielectric mirror, PML ... Light modulator material layer member,
E ... Power supply, WL ... Write light, RL ... Read light,

Claims (1)

[Claims] 1. A spatial light modulator of the optical writing type, wherein a plurality of members including at least a photoconductive layer member and a light modulator layer member are laminated between transparent substrates to which transparent electrodes are attached. When manufacturing a photo-writing type spatial light modulator in which a hydrogenated amorphous silicon film is used as a photoconductive layer member, the substrate on which the hydrogenated amorphous silicon film is to be deposited is set to a predetermined temperature, and SiH4 gas is supplied at 15 sc.
cm, H2 gas is 60 sccm, B2 for SiH4 gas
H6 gas flow rate ratio is less than 1.0PPm, gas pressure is 133P
When a hydrogenated amorphous silicon film is formed on the above-mentioned substrate by the plasma CVD method in the atmosphere of a, the above-mentioned hydrogenated amorphous silicon is used as the above-mentioned substrate while the front and back surfaces are parallel optical planes. Using a structure in which a transparent electrode is attached to a transparent substrate made of glass having a thermal expansion coefficient similar to that of the film, and the surface of the hydrogenated amorphous silicon film attached and formed on the substrate is A method for manufacturing an optical writing type spatial light modulator, comprising a step of polishing so as to be parallel to the surface of the substrate.