JPH07110492A - Spatial optical modulation element and its production - Google Patents

Abstract

PURPOSE:To provide the spatial optical modulation element which cannot stably operate even if reading-out is executed with reading-out light of high intensity. CONSTITUTION:A transparent conductive electrode 102, a photoconductive layer 101 and island-shaped light reflection mirrors 103 are laminated on a glass substrate 106. The photoconductive layer 101 between these island-shaped light reflection mirrors 103 is removed by a half or more by etching to form hole parts. Al light shielding films 114 are formed on a part of the bases and flanks of these hole parts and high polymers contg. red pigments are packed into the hole parts to form light absorption layers 104; thereafter, a polyimide oriented film 109 subjected to a rubbing treatment is laminated thereon. A ferroelectric liquid crystal layer 105 having a thickness of 1 to 2mum is held between such substrate and a glass substrate 108 laminated with a transparent conductive electrode 107 consisting of ITO and the polyimide oriented film 115.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spatial light modulator used for an optical arithmetic unit, a projection display and the like and a method for manufacturing the same.

[0002]

2. Description of the Related Art The basic structure of an optical address type spatial light modulating element using a liquid crystal layer (hereinafter, spatial light modulating element refers to this optical addressing type unless otherwise specified) is a photoconductive layer. A liquid crystal layer whose light transmittance changes by application of a layer and an electric field is sandwiched between two transparent conductive electrodes facing each other. This element is driven by applying a voltage from the outside between both transparent conductive electrodes. And
When the photoconductive layer is irradiated with writing light in this state, the electric resistance of the photoconductive layer changes, the voltage applied to the liquid crystal layer changes, and the reading light passing through the liquid crystal layer changes depending on the magnitude of this voltage. Modulate.

By using this operation, functions such as optical threshold processing, wavelength conversion, incoherent / coherent conversion, and image memory can be realized. Therefore, the spatial light modulator is a key device for optical information processing. Is positioned as. In addition, it can also be used as a projection display because it can realize a light amplification function by making read light with high light intensity incident from the direction opposite to the write light and reading the written content in a reflective type. You can In this projection display, the spatial light modulation element is expected to obtain a brighter screen with higher resolution than that of an active matrix type liquid crystal light valve, and therefore, there are great expectations.

A problem in applying the spatial light modulator to a projection display is that it is necessary to devise so that the read light having high intensity does not leak to the photoconductive layer on the write side. Therefore, it has been reported that a large number of dielectric mirrors in which dielectrics having different refractive indexes are alternately laminated with a film thickness of ¼ wavelength are formed between a liquid crystal layer and a photoconductive layer (for example, , JP-A-1-315723). The use of a dielectric mirror is effective because it can suppress leakage of read light. However, when the device is operated, charges are trapped in the dielectric mirror and accumulate with time, so the voltage applied to the liquid crystal layer becomes unstable, and the operating conditions of the device change and afterimages occur. There is a problem of doing.

In order to solve the problems of such a dielectric mirror, it has been reported that an island-shaped metal reflective film arranged in a two-dimensional array is formed instead of the dielectric mirror (for example, a special feature). (Kaisho 62-40430). In this case, the readout light leaks to the photoconductive layer in the portion where the island-shaped metal film is not present, and therefore, as shown in FIG. 7, the light absorption layer 407 is filled with a high molecular polymer in which a black pigment is dispersed. In FIG. 7, 401 and 408 are glass substrates,
2, 406 are transparent conductive electrodes, 403 is a photoconductive layer, 40
Reference numeral 4 is an island-shaped metal film, and 405 is a liquid crystal layer.

[0006]

However, in general,
High-intensity light sources such as halogen lamps, metal halide lamps, and xenon lamps are used for the readout light, but these light sources include infrared light, which is partially removed by an infrared cut filter. It can be done, but it cannot be completely removed. Therefore, the spatial light modulator is inevitably irradiated with infrared light. In the spatial light modulation element of FIG. 7 given as a conventional example, a high molecular polymer in which a black pigment is dispersed is used to shield the reading light, but infrared light is also absorbed here and the liquid crystal layer of the liquid crystal layer is absorbed. The temperature rises. There is a problem that the liquid crystal undergoes a phase transition when the temperature rises, making it impossible to perform a desired operation. Therefore, there are problems that the intensity of the reading light cannot be increased and a large-scale cooling device is required.

On the other hand, in the photoconductive layer of the spatial light modulator, hydrogenated amorphous silicon (hereinafter abbreviated as a-Si: H) is used.
Thin films are most commonly used. The forbidden band width of the a-Si: H film is 1.7 to 1.8 eV (The forbidden band width of a thin film such as a-Si: H is usually obtained by the hν- (αhν) ^1/2 plot. Is a Planck's constant, ν is the frequency of light, and α is an absorption coefficient.) It is small and absorbs the entire visible light range from blue to red. Therefore, in order to prevent light from leaking to the photoconductive layer made of a-Si: H, it is unavoidable to use a black one, and absorption of infrared light at that portion is unavoidable. A-S to transmit red light
Although it is possible to increase the band gap of the i: H film by increasing the hydrogen content, it is a conventional practice to use a gas obtained by diluting SiH ₄ with H ₂ or He or Ar to a concentration of 10 to 80%. In the plasma CVD method of (1), the photoconductivity of the film is generally remarkably lowered when the hydrogen content is increased, so that it cannot be used as the photoconductive layer of the spatial light modulator.

In order to enhance the function of the photoconductive layer,
Hydrogenated amorphous germanium nitride (hereinafter a-Ge _1-x N
_x : H) may be stacked in a narrow band gap, but normally, in order to form such a nitride film, plasma C using a mixed gas of GeH ₄ and N ₂ is used.
The VD method is adopted. However, since N ₂ is more difficult to decompose than GeH ₄ , a film containing nitrogen cannot be obtained unless a large high-frequency power is applied, and a is not formed on the photoconductive layer such as a-Si: H. When an attempt is made to stack a —Ge _1-x N _x : H film, ions with high energy are a-Si: H.
There has been a problem that the layer is collided and damaged, many defects that act as carrier traps are generated in the film, and the photoconductivity of a-Si: H is deteriorated.

In order to solve the above-mentioned problems of the prior art, the present invention provides a spatial light modulation element that does not cause malfunction of the element or malfunction due to temperature rise even when reading with high intensity reading light. Manufacture of a spatial light modulator capable of producing an a-Si: H film as a photoconductive layer having a wide band gap and excellent photoconductivity and a nitride film without damaging the photoconductive layer The purpose is to provide a method.

[0010]

To achieve the above object, the spatial light modulator of the present invention transmits red light to a region sandwiched by two transparent insulating substrates having transparent conductive electrodes. A spatial light modulator having at least a photoconductive layer having a wide band gap, a liquid crystal layer, and a plurality of island-shaped light reflecting mirrors provided in the same plane between these layers, A hole is provided in the photoconductive layer between the island-shaped light reflecting mirrors, and the hole is filled with a light absorption layer that transmits infrared light and absorbs visible light.

In the above structure, it is preferable that the photoconductive layer has a rectifying property. Further, in the above structure, the photoconductive layer is preferably made of an amorphous semiconductor layer containing silicon as a main component.

Further, in the above structure, the band gap of the photoconductive layer is preferably 2.0 eV or more. In the above structure, between the photoconductive layer and the island-shaped light reflecting mirror,
It is preferable that an intermediate layer having a conductivity smaller than the band gap of the photoconductive layer and having a large conductivity is interposed. In this case, it is preferable that the intermediate layer is made of germanium nitride or silicon germanium nitride.

Further, according to the first method of manufacturing a spatial light modulator of the present invention, a band gap for transmitting red light is provided in a region sandwiched between two transparent insulating substrates having transparent conductive electrodes. A method for manufacturing a spatial light modulator comprising at least a wide photoconductive layer, a liquid crystal layer, and a plurality of island-shaped light reflecting mirrors provided in the same plane between these layers, wherein at least silicon is used. A mixed gas obtained by diluting a compound gas containing as a main component with helium to 1% or less is introduced into a vacuum container, an electric field is applied to the mixed gas to generate plasma, and the compound gas is decomposed to form a photoconductive layer. A liquid crystal layer is formed after the formation.

Further, according to the second method of manufacturing the spatial light modulator of the present invention, the forbidden band width for transmitting red light is provided in the region sandwiched between the two transparent insulating substrates having the transparent conductive electrodes. A wide photoconductive layer, a liquid crystal layer, and at least a plurality of island-shaped light reflecting mirrors provided in the same plane between these layers, and between the photoconductive layer and the island-shaped light reflecting mirrors. A method for manufacturing a spatial light modulator in which an intermediate layer made of germanium nitride or silicon germanium nitride intervenes, wherein a compound gas containing at least germanium as a main component is replaced with nitrogen gas.
% Of the mixed gas is introduced into a vacuum container, an electric field is applied to the mixed gas to generate plasma, the compound gas is decomposed to form an intermediate layer, and then a liquid crystal layer is formed. Characterize.

[0015]

According to the structure of the present invention, even if the readout light leaks from between the island-shaped light reflecting mirrors to the photoconductive layer, the infrared light passes through the light absorption layer and the photoconductive layer, so that the device It is not absorbed within. Therefore, the temperature of the device does not rise and the liquid crystal in the liquid crystal layer does not undergo a phase transition to cause a malfunction. In addition, when visible light leaks into the photoconductive layer, the electric resistance of the photoconductive layer decreases and the liquid crystal layer switches, which causes a problem. It is the red light that leaks into the photoconductive layer as it is absorbed by.

However, since the photoconductive layer does not absorb and transmits red light, the electric resistance of the photoconductive layer is hardly affected. Therefore, there is no possibility that the liquid crystal layer is switched by the leaked light of the reading light. From the above, the spatial light modulation element of the present invention can provide a bright image without causing malfunction of the element or malfunction due to temperature rise even when reading with a high intensity read light.

Next, according to the first method of the present invention, why is it possible to obtain an a-Si: H film having a wide bandgap for transmitting red light and having high photoconductivity? Will be described.

Generally, an amorphous semiconductor thin film such as a-Si: H is produced by a plasma CVD method. a-S
In the case of i: H, SiH ₄ which is a source gas is diluted with H ₂ or Ar and introduced into a vacuum container. SiH ₄ dissociates into intermediate species SiH, SiH ₂ , SiH _{3 and the} like in plasma. The a-Si: H film is formed by these intermediate species arriving on the substrate by diffusion and causing an adsorption reaction on the surface.

Therefore, the bonding state of silicon atoms and hydrogen atoms in the film and the hydrogen content strongly depend on the kind of intermediate species contributing to film formation and the state of the film growth surface. It is known that the intermediate species diffusing to the film growth surface is mainly SiH ₃ having a long life.

In a normal plasma gas phase, the secondary reaction between intermediate species cannot be ignored, and a plurality of Si
It is known that there exists a high-order intermediate species composed of atoms, and that when SiH ₄ is diluted with a large amount of hydrogen, a film of only SiH ₃ is formed. Noble gases such as He and Ar have a high excitation energy level without being bonded to intermediate species or atoms forming the film.

Therefore, if the SiH ₄ concentration is made extremely small by diluting the rare gas, the secondary reaction in the gas phase is reduced due to the reduction in the concentration of the intermediate species and the electron temperature in the plasma is increased, thereby contributing to the film formation. The intermediate species to be used also have a short life such as SiH and SiH _2, but it is considered that the intermediate species will have a large energy.

Therefore, if the heating temperature of the substrate is made relatively low and the thermal desorption of hydrogen from the film is suppressed, the hydrogen content in the film is carried to the film growth surface by the intermediate species at most. A stable atomic network having a large binding energy can be formed by the incoming energy, and a defect-free high-quality film in which electrons can be smoothly moved can be formed. That is, when the plasma CVD method in which the source gas is diluted with a large amount of rare gas is adopted, an a-S having a high hydrogen content, a wide band gap, and excellent photoconductivity is obtained.
An i: H film can be obtained.

Next, the reason why it becomes possible to form a nitride film without damaging the photoconductive layer according to the second method of the present invention will be described. a-Ge _1-x N
A nitride film such as _x : H is also produced by the plasma CVD method similarly to a-Si: H. Since GeH ₄ is more easily decomposed than N ₂ , even if a low-power high-frequency wave of the same degree as when a-Si: H is deposited is applied, N ₂ is not decomposed and only GeH ₄ is decomposed, and most of the nitrogen is decomposed. The a-Ge: H film, which does not contain it, grows.

However, if the GeH ₄ concentration is reduced by diluting the nitrogen so that the GeH ₄ is almost decomposed even at low power, the decomposition of N ₂ proceeds and nitrogen is taken into the film. Therefore, a-Ge
_-1-x N _x: H to a film can be formed by application of a low power radio frequency. Therefore, even in the case of stacking on a-Si: H, it is possible to form a film without damaging a-Si: H as in the conventional case.

[0025]

EXAMPLES The present invention will be described in more detail below with reference to examples. FIG. 1 is a sectional view showing an embodiment of the spatial light modulator according to the present invention.

As shown in FIG. 1, the transparent insulating substrate 106.
A transparent conductive electrode (for example, a conductive oxide such as ITO (indium-tin oxide), ZnO or SnO ₂ ) 102 and a photoconductive layer 101 having a rectifying property are provided on (for example, a glass substrate). It is sequentially laminated. The island-shaped light reflecting mirror 103 and the liquid crystal layer 10 are provided on the photoconductive layer 101.
Alignment film 109 for orienting 5 is sequentially arranged. An alignment film 115 is also uniformly formed on the transparent conductive electrode 107 on the opposite side. In FIG. 1, 108 is a transparent insulating substrate (for example, a glass substrate).

The spatial light modulator is driven by externally applying a voltage between the transparent conductive electrodes 102 and 107. When the photoconductive layer 101 is irradiated with the writing light 110 in this state, the voltage applied to the liquid crystal layer 105 in the portion irradiated with the light is increased, and the alignment state of the liquid crystal molecules is increased according to the magnitude of this voltage. Changes. This change in the alignment state is caused by the optical system in which the polarizer 111 and the analyzer 112 are combined, and the read light 113 is incident from the direction opposite to the write light 110, whereby the reflected light from the island-shaped light reflecting mirror 103 is reflected. Can be observed as.

Materials used for the liquid crystal layer 105 include nematic liquid crystal, super twist nematic liquid crystal,
There are ferroelectric liquid crystals, antiferroelectric liquid crystals, dispersion type liquid crystals in which liquid crystals are dispersed in a polymer, and the like. When the ferroelectric liquid crystal or the anti-ferroelectric liquid crystal is used, the thickness of the liquid crystal layer 105 can be reduced, so that the electric impedance can be reduced and the thickness of the photoconductive layer 101 can be set thin. This is useful because it enables high-speed response and has a memory function. Further, the transmission characteristic of the ferroelectric liquid crystal has a steep threshold characteristic with respect to the voltage, and is therefore an optimal material for performing threshold processing on input light. On the other hand, when the dispersion type liquid crystal is used, the polarizer 111,
There is an advantage that the analyzer 112 and the alignment films 109 and 115 are unnecessary, the output light is bright, and the element and the optical system are simple.

When a liquid crystal material other than the dispersion type liquid crystal is used, the liquid crystal layer 105 is sealed with a resin, and a spacer (not shown in FIG. 1) is used to adjust the layer thickness. It is mixed in 105. As the spacer, beads of alumina or quartz or powder of glass fiber is usually used. Further, these spacers are also mixed in the resin that seals the liquid crystal layer 105. The alignment films 109 and 115 for aligning the liquid crystal are S
It is composed of an iO _x oblique deposition film or a thin film of an organic polymer such as polyimide or polyvinyl alcohol subjected to a rubbing treatment.

As the material used for the photoconductive layer 101,
Those having a transmittance of 90% or more for red light of 650 nm to 800 nm are preferable. For example, more forbidden band width 2.0eV of a-Si: H, a- Si 1-x C x:
Hydrogenated amorphous semiconductors such as H, a-Ge _1-x C _x : H (hydrogenated amorphous germanium carbide), amorphous selenium, Bi ₁₂ SiO ₂₀ and the like. It should be noted that halogen atoms such as F and Cl may be added to the hydrogenated amorphous semiconductor in the same manner as hydrogen in order to effectively reduce the dangling bonds that act as carrier traps, and / or a minute amount. (For example, 0.1 to 10 atom%) oxygen atoms may be contained. Among these, a-Si: H obtained by a plasma CVD method in which a source gas is diluted with a rare gas has the highest photoconductivity and is useful because it can increase the sensitivity of the device.

In order to impart rectifying property to the photoconductive layer 101, a p / i, i / n, p / i / n structure may be formed inside (however, the i layer means an undoped layer). . In the case of the hydrogenated amorphous semiconductor, the p-type impurity is an element such as B, Al, or Ga, and the n-type impurity is N, P, or the like.
Elements such as As, Sb, and Se may be added. further,
In the case of the rectifying photoconductive layer formed of the hydrogenated amorphous semiconductor, p / i, i from the transparent conductive electrode 102 side is used.
When / n or p / i / n is set, the migration distance of holes having low mobility is reduced, and thus photosensitivity can be further increased. Further, when the liquid crystal layer 105 is made of a ferroelectric liquid crystal that responds at high speed in the order of μs, it is necessary to flow a large forward current in order to maintain the response speed of the liquid crystal. In an amorphous semiconductor containing a large amount of hydrogen, hydrogen is bonded so as to inactivate the impurities even if the impurities are added, so that the effect of adding the impurities is not remarkable, and a necessary forward current is applied. May not be possible.

In such a case, a-Ge _{1 -x} N _x : H having a narrower band gap than the photoconductive layer 101 instead of the n layer is used.
(Provided that x ≦ 0.5) or hydrogenated amorphous silicon germanium nitride (a-Si _1-xy Ge _x N _y : H, provided that
0.5 ≦ x, y ≦ 0.5) is inserted as the intermediate layer 116 between the photoconductive layer 101 and the island-shaped light reflecting mirror 103 (see FIG. 2), the leak light of the read light 113 can be efficiently emitted. It is more preferable because it absorbs. In addition, a-Ge _1-x N _x :
There is no problem if H and a-Si _1-xy Ge _x N _y : H contain oxygen atoms to the extent that the band gap does not widen.

Specifically, O / Ge ≦ 30% and O / (Si + Ge) ≦ 30%, respectively. Also, a-Ge
_1-x N _x : H and a-Si _1-xy Ge _x N _y : H have a conductivity of 10 ⁻⁸ Ω / cm or more in the undoped state, which is higher than that of a-Si: H, and thus the A large forward current can be passed in the photo structure and the photoconductive layer 1
It does not impede the movement of the optical carrier moving in the 01. Further, even if visible light enters, the density of free carriers thermally excited with respect to the photo-generated carriers is high, so that even if leaked light of the reading light 113 enters, the liquid crystal layer does not malfunction. It is very effective.

The island-shaped light reflecting mirror 103 has a large reflectance A.
It is composed of a metal thin film such as 1, Ag, Mo, Ni, Cr, or Mg, and is arranged in a two-dimensional matrix or mosaic. Further, the photoconductive layer 101 between the island-shaped light-reflecting mirrors 103 must be removed by etching at least the n-layer portion or the intermediate layer for the purpose of preventing lateral diffusion of carriers and improving the resolution of the device. There is. As a result, the diffusion of carriers between the island-shaped light reflecting mirrors 103 can be suppressed, and the resolution of the device can be increased. However, if this is left as it is, the read light 113 enters the photoconductive layer 101 from the gap between the island-shaped light reflecting mirrors 103 when reading with high intensity light, causing a malfunction, so that the hole portion formed by the etching is further added. The blue absorbed by the photoconductive layer 101
A light absorbing layer 104 that absorbs green light (for example, a high molecular polymer mixed with a red pigment is applied, or formed by an inorganic red filter or red aC: H or a-Si: H) is formed. There is a need. In addition, the reading light 11
In order to make the shading of 3 more perfect, Al, Ag,
A metal light-shielding film 114 such as Mo, Ni, Cr, or Mg may be formed on the bottom of the hole and a part of the side surface.

Incidentally, TaO is used instead of the island-shaped light reflecting mirror 103.
₂ , a thin film with a large refractive index such as Si and MgF, SiO
It may be used a small thin film of refractive index alternately multilayered dielectric mirror laminated on the multilayer as _2.

A-Si having a forbidden band width of 2.0 eV or more, which is suitable for the photoconductive layer 101 and has excellent photoconductivity:
The H film can be produced using a plasma CVD apparatus as shown in FIG. The power supply 201 is direct current, high frequency (1 kHz to 100 MHz) or microwave (1 GHz).
The above power source is connected to the electrode 203 in the vacuum container 202 through the matching circuit 204 (however,
In the case of direct current, the matching circuit 204 is unnecessary). Electrode 20
3 has a large number of holes like showers, and the raw material gas cylinder 205 and the rare gas cylinder 20 are passed through these holes.
6. The raw material gas, the rare gas, and the impurity gas in the impurity gas cylinders 207 and 208 are introduced into the vacuum container 202.
In addition, each gas is a mass flow controller 209, 21
A predetermined flow rate is adjusted by 0, 211 and 212.
The substrate 213 for forming the film is placed on the heater 214 and heated to a predetermined temperature. 215 in FIG.
Is a vacuum pump and 216 is a valve.

The film forming procedure will be described below. First, a source gas and a rare gas (if necessary, an impurity gas) having a predetermined flow rate are introduced into the vacuum container 202 that has been evacuated to a high vacuum, and a predetermined pressure is set by the vacuum pump 215 and the valve 216. Then, an electric field is applied between the electrode 203 and the grounded substrate 213 to generate plasma, and an a-Si: H film having a predetermined thickness is formed on the substrate 213.

The source gas used for forming the a-Si: H film must contain hydrogen atoms in the gas molecules, which have the function of terminating dangling bonds.
Specifically, SiH ₄ , Si ₂ H ₆ , Si ₃ H ₈ , Si
₄ H ₁₀ , SiH _{4 -n} F _n , SiH _{4 -n} Cl _n (where n = 1,2,
Mixed gas consisting of one of the above 3 or a combination thereof, or these gases and SiF ₄ , Si ₂ F ₆ and SiC
Examples of the gas include a gas of 1 ₄ or a mixture of 2 or more thereof. He, Ne, Ar, Kr, Xe, etc. are used as a rare gas for diluting these gases.

In order to change the electric conductivity of the film,
To add impurities, in the case of n-type conduction, P, A
In order to add impurities such as s, Sb, and Se, PH₃, P
F₃, PF_Five, PCl₂F, PCl₂F₃, PCl₃, PBr
₃, AsH₃, AsF₃, AsF_Five, AsCl₃, AsB
r₃, SbH₃, SbF₃, SbCl₃, H₂Gas such as Se
Can be mixed with the above-mentioned raw material gas and diluent gas,
In the case of conduction, impurities such as B, Al, Ga, In are added.
For B₂H₆, BF₃, BCl₃, BBr₃, (CH₃) ₃
Al, (C₂H_Five)₃Al, (iC_FourH₉)₃Al, (C
H₃)₃In, (CH₃)₃Ga, (C₂H_Five)₃In, (C₂
H_Five)₃Gas such as Ga is mixed with the above-mentioned raw material gas and rare gas.
Just match.

Incidentally, a-G used as the intermediate layer 116
Also for e _1-x N _x : H, it is possible to form a film by using the plasma CVD apparatus shown in FIG. However, in this case, the gases introduced into the vacuum container 202 are GeH ₄ , Ge ₂ H ₆ , Ge ₃ H ₈ , and Ge.
_{F 4, GeCl 4, GeBr 4} , GeI 4, GeF 2, Ge
_{Cl 2, GeBr 2, GeI 2} , GeHF 3, GeH 2 F 2,
GeH ₃ F, GeHCl ₃ , GeH ₂ Cl ₂ , GeH ₃ C
l, GeHBr ₃ , GeH ₂ Br ₂ , GeH ₃ Br, GeH
One of I ₃ , GeH ₂ I ₂ , and GeH ₃ I, or a mixed gas of two or more thereof, and N ₂ . In addition, a-Si
_{When a 1-xy} Ge _x N _y : H film is formed, these gases may be mixed with the above silicon compound gas.

The present invention will be described below with reference to specific examples.
Will be described in detail. (Example 1) As shown in FIG.
ITO is deposited on the lath substrate 106 by the sputter deposition method.
Transparent conductive electrode with a film thickness of 0.05 to 0.2 μm
102 was formed. Then, this is the plasma shown in FIG.
It is moved to the inside of the CVD device and the inside of the vacuum container 202 is set to 1 × 10. ^-6T
After exhausting to below orr, the heater 214
Heated to 0-200 ° C. Then the concentration diluted with He
10 ppm B₂ H₆ : 100 sccm and SiH_Four :
0.05-1 sccm is introduced into the vacuum vessel 202, and
After adjusting the force to 0.5 to 1.0 Torr, the electrode 203
Apply 13.56MHz, 10 ~ 20W high frequency power to
Then, plasma is generated and the p-type a-Si: H layer is exposed to 0.0
It was formed with a film thickness of 1 to 0.1 μm.

Next, the inside of the vacuum container 202 was once evacuated to a high vacuum, and then He: 100 sccm and SiH ₄ : 0.0
5-1 sccm was introduced into the vacuum container 202, an i-type undoped a-Si: H layer was formed in a thickness of 1 to 2 μm in the same manner, and the inside of the vacuum container 202 was evacuated again. Then, PH ₃ diluted with He at a concentration of 10 ppm: 100 s
ccm and SiH _4: vacuum the 0.05~1sccm container 2
02, and in the same manner, an n-type a-Si: H layer having a thickness of 0.
A photoconductive layer 101 was formed by stacking layers with a film thickness of 1 to 0.5 μm. Then, an Al film was formed on the surface of the photoconductive layer 101 by a resistance heating vapor deposition method or the like, and an island-shaped light reflecting mirror 103 was formed by a photo-etching method (however, the island-shaped light reflecting mirror 103 was formed.
Can be formed not only by photolithography but also by lift-off method). Here, the island-shaped light reflecting mirror 103 is 1000 × 2
The size of one island is 23 μm × 23 μm, and the pitch between islands is 25 μm.

Next, half or more of the photoconductive layer 101 between the island-shaped light reflecting mirrors 103 was removed by etching to form holes. Next, an Al light-shielding film 114 is formed on the bottom and part of the side surface of the hole, and a high molecular polymer containing a red pigment is filled in the hole to form the light absorption layer 104, and then a rubbing-treated polyimide is applied. The alignment film 109 was laminated. 1 is provided between this and a glass substrate 108 on which a transparent conductive electrode 107 made of ITO and a polyimide alignment film 115 are laminated.
A spatial light modulator (1) was produced by sandwiching a ferroelectric liquid crystal layer 105 having a thickness of ˜2 μm.

Separately from this, B ₂ H ₆ : 100 sccm and SiH ₄ : 100 ppm with a concentration of 100 ppm diluted with He.
10 sccm and p-type a-Si: H layer, He:
I using 100 sccm and SiH ₄ : 10 sccm
Type undoped a-Si: H layer diluted with He to a concentration of 1
00ppm of PH _3: 100sccm and SiH _4: 10
sccm and n-type a-Si: H are formed to have the same film thickness as in the case of the spatial light modulator (1) to form the photoconductive layer 101, which is used to form the spatial light modulator ( 1)
A spatial light modulator (2) was produced in exactly the same manner as. That is, the photoconductive layer 101 of the spatial light modulator (1) is made of Si.
H ₄ concentration {= SiH ₄ / (SiH ₄ + He)} is 500
Although produced in the range of ppm to 1%, the spatial light modulator (2) was produced with a SiH ₄ concentration of 10%.

An AC voltage waveform (V _p shown in FIG. 4 is generated between the transparent conductive electrodes 102 and 107 of these spatial light modulators.
= 2 to 10 V, T _p : T = 1: 10, T = 333 μs)
Is applied, an Ar ion laser (488 nm) is used as the writing light 110, and He- as the reading light 113.
The operation was investigated using a Ne laser (633 nm). Here, the operation of the device will be briefly described with reference to FIG. However,
The applied voltage was set so that the transparent conductive electrode 107 became +. The writing light 110 is emitted when the + pulse for reverse biasing the photoconductive layer 101 is applied, whereby the voltage applied to the liquid crystal layer 105 is increased, the liquid crystal is switched from the off state to the on state, and the output light by the reading light 113 is output. Is output. After that, when the pulse of − which is forward biased to the photoconductive layer 101 is applied, the liquid crystal layer 105 is switched to the off state regardless of the irradiation of the writing light 110.

Under these operating conditions, the spatial light modulator (1) has a photosensitivity of 70 μW / cm ² , a rise time of 30 μs, and a fall time of 60 μs.
The spatial light modulator (2) had a photosensitivity of 90 μW / cm ² , a rise time of 50 μs, and a fall time of 60 μs.

Further, the i layer used in the spatial light modulators (1) and (2) is formed on a quartz substrate to have a film thickness of about 1 μm,
The optical forbidden band width and the photoconductivity when irradiated with AM1 light having an intensity of 100 mW / cm ² were examined. As a result, the optical bandgap of the spatial light modulator (1) is 2.05
2.36 eV, the spatial light modulator (2) is 1.87 e
The spatial light modulator (1) has a photoconductivity of 1.0 × 10 ^{−5 to} 3.2 × 10 ⁻⁵ Ω / cm, and the spatial light modulator (2) has a higher photoconductivity. It was 5.7 × 10 ⁻⁶ Ω / cm.

Next, these spatial light modulators (1),
(2) 301 and CRT as writing light source 302
Using a (cathode ray tube), a xenon lamp with a reflecting mirror as a light source for projection 303, a projection lens system 304, a polarization beam splitter 305, and a screen 306, a projection display device as shown in FIG. It was made. Then, both transparent conductive electrodes 102 of these elements,
The AC voltage waveform (V _p = 2 to 10) shown in FIG.
V, T _p : T = 1: 10, T = 333 μs) was applied. In this apparatus, when the image was enlarged and projected on the screen 306 with a projected light of 200 lumens, the image of the spatial light modulation element (2) was whitish and unclear, whereas that of the spatial light modulation element (1). One is the projected light 1000
Even in lumens, bright and clear images were output stably. In the spatial light modulator (2), the red component of the projected light leaked from the light absorption layer 104 to the photoconductive layer 101, and the liquid crystal layer 105 was switched. Further, the spatial light modulation element (1) did not show any operation failure due to the temperature rise of the element even after being used for a long time.

Example 2 In the spatial light modulator (1) manufactured in Example 1, the n-type aS of the photoconductive layer 101 was used.
The i: H layer was replaced with an a-Ge _1-x N _x : H intermediate layer 116, and a photoconductive layer 101 having a structure as shown in FIG. 2 was produced.
The a-Ge _1-x N _x : H intermediate layer 116 is produced by forming a p-i structure of a-Si: H using the plasma CVD apparatus shown in FIG. 3 and then forming GeH ₄ in the vacuum container 202. 0.
1 to ₁ sccm, N ₂ : 100 sccm was introduced, and
It was performed by forming a film with a film thickness of 1 to 0.5 μm. Using this photoconductive layer 101, a spatial light modulator (3) was produced in the same manner as in Example 1.

Further, the photoconductive layer 101 used for the spatial light modulator (3) was separately prepared in the same manner, and a-Ge _1-x N
_An Al electrode was formed on the _x : H layer, and the voltage-current characteristics of the photoconductive layer 101 were examined. The result is shown in FIG. The photocurrent has a wavelength of 450 from the ITO electrode 102 side under reverse bias.
It was obtained by irradiation with monochromatic light having a wavelength of 0.5 μW / cm ² and an intensity of 0.5 μW / cm ² . In this way, good photodiode characteristics could be confirmed.

A-Ge used for the spatial light modulator (3)
_{The 1-x} N _x : H film has a GeH ₄ concentration {= GeH ₄ / (GeH 4
₄ + N ₂ )} was produced in the range of 0.1 to 1%, and this film (A film) was deposited on a quartz plate and a crystalline Si wafer with a film thickness of about 1 μm, and The band gap and infrared absorption (IR) spectrum were measured, respectively. For comparison, GeH ₄ : 10 to 50 sccm, N
₂ : 100 sccm flow rate (GeH ₄ concentration is 10
The film (B film) produced under the conditions of ˜30% and the other conditions being the same) was also examined.

As a result, the optical band gap is 1.2 to 1.
6eV is (A layer) and 0.8~1.1eV (B film), the IR spectrum, A film absorption peak around 3300 cm ^-1 and 1150 cm ^-1 appears to be attributable to N-H bonds If, while the absorption band near 760 cm ^-1 and 1430 cm ^-1 appears to be due to the Ge-N bond is significantly observed, B films these peaks were obscured.

Next, when the high frequency power was quintupled under the manufacturing conditions of the B film, an a-G film having the same characteristics as the A film was obtained.
An e _1-x N _x : H film was obtained (this is referred to as C film). This C
A spatial light modulator (4) using the film as the intermediate layer 116 was produced.

When the operating characteristics of these spatial light modulators (3) and (4) were examined in the same manner as in Example 1, the optical sensitivity of the spatial light modulator (3) was 70 μW / cm ² , and the rise time was Although the fall time was 30 μs and the fall time was 30 μs, the photosensitivity of the spatial light modulator (4) was 95 μW / cm.
² , rise time is 45μs, fall time is 30
It was μs. The spatial light modulator (4) includes an intermediate layer 116.
It is considered that the defect was generated in the a-Si: H photoconductive layer 101 at the time of formation, and thus the characteristics were deteriorated as compared with the spatial light modulator (3).

Example 3 In the spatial light modulator (3) manufactured in Example 1, GeH ₄ : 0.1 to 1 sccm, instead of the a-Ge _1-x N _x : H film intermediate layer 116. S
iH _4: 0.1~1sccm, N _2: to introduce the 200sccm, forbidden band width is 1.4~1.8eV a-Si
A spatial light modulator (5) using a _1-xy Ge _x N _y : H film was produced. When this spatial light modulator (5) is arranged in the projection type display device of FIG.
It was confirmed that the image projected on the screen 2 was clearly magnified and projected on the screen 306 with high brightness similarly to the spatial light modulator (1). In addition, even after long-term use, no malfunction was observed due to the temperature rise of the element.

These manufactured spatial light modulators (1),
(3) and (5) also function as a spatial light modulator for displaying a dynamic hologram.

The liquid crystal layer, photoconductive layer, intermediate layer, and
The light absorption layer and the applied voltage waveform are the same as those in Examples 1, 2, 3
Needless to say, it is not limited to those listed in. In addition, in the projection system of FIG.
It goes without saying that a color image can be output on the screen by combining the three CRTs for G and B three-color display and the three spatial light modulation elements and incorporating the color separation optical system and the color synthesis optical system into the optical system. .

[0058]

As described above, according to the structure of the spatial light modulation element of the present invention, it is possible to provide the spatial light modulation element that can stably operate even if it is read by the read light having high intensity. it can.

Further, the first spatial light modulator according to the present invention
According to the manufacturing method of (1), a hydrogenated amorphous silicon (a-Si: H) film having a wide forbidden band and excellent photoconductivity can be produced. It can be used as a photoconductive layer.

The second embodiment of the spatial light modulator according to the present invention
According to the manufacturing method of ( ₁₎ , hydrogenated amorphous germanium nitride (a-Ge _1-x N) is obtained without damaging the photoconductive layer.
_{Since a} nitride film having a narrow bandgap such as _x : H) can be laminated on the photoconductive layer, the function of the photoconductive layer can be enhanced.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an embodiment of a spatial light modulator according to the present invention.

FIG. 2 is a sectional view of a photoconductive layer used in one embodiment of the spatial light modulator according to the present invention.

FIG. 3 is a schematic view of a plasma CVD apparatus used for manufacturing an embodiment of the spatial light modulator according to the present invention.

FIG. 4 is a timing chart of applied voltage, write light, and output light used in an embodiment of the spatial light modulator according to the present invention.

FIG. 5 is a configuration diagram of a projection type display device used in an embodiment of the spatial light modulator according to the present invention.

FIG. 6 is a voltage-current characteristic diagram of a photoconductive layer used in one embodiment of the spatial light modulator according to the present invention.

FIG. 7 is a sectional view of a conventional spatial light modulator.

[Explanation of symbols]

101 Photoconductive Layer 102, 107 Transparent Conductive Electrode 103 Island Light Reflector 104 Light Absorption Layer 105 Liquid Crystal Layer 106, 108 Transparent Insulating Substrate 109, 115 Alignment Film 110 Write Light 113 Readout Light 114 Light Shielding Film 116 Intermediate Layer 201 Power Supply 202 vacuum container 203 electrode 204 matching circuit 205 raw material gas cylinder 206 rare gas cylinder 207, 208 impurity gas cylinder 209, 210, 211, 212 mass flow controller 213 substrate 214 heater 215 vacuum pump 216 valve

Claims (8)

[Claims] 1. A photoconductive layer having a wide bandgap for transmitting red light, a liquid crystal layer, and a region between these layers in a region sandwiched between two transparent insulating substrates provided with transparent conductive electrodes. At least a plurality of island-shaped light reflecting mirrors provided in the same plane, holes are provided in the photoconductive layer between the island-shaped light reflecting mirrors, and infrared light is transmitted through the holes. A spatial light modulator comprising a light absorbing layer for absorbing visible light. 2. The spatial light modulator according to claim 1, wherein the photoconductive layer has a rectifying property. 3. The spatial light modulator according to claim 1, wherein the photoconductive layer is an amorphous semiconductor layer containing silicon as a main component. 4. The spatial light modulator according to claim 1, wherein the band gap of the photoconductive layer is 2.0 eV or more. 5. A spatial light modulator according to claim 1, wherein an intermediate layer narrower than the band gap of the photoconductive layer and having a high conductivity is interposed between the photoconductive layer and the island-shaped light reflecting mirror. . 6. The spatial light modulator according to claim 5, wherein the intermediate layer is made of germanium nitride or silicon germanium nitride. 7. A photoconductive layer having a wide bandgap for transmitting red light, a liquid crystal layer, and a space between these layers in a region sandwiched by two transparent insulating substrates provided with transparent conductive electrodes. A method of manufacturing a spatial light modulator comprising at least a plurality of island-shaped light reflecting mirrors provided in the same plane, wherein the compound gas containing at least silicon as a main component is 1% with helium.
After introducing the diluted mixed gas into a vacuum container and applying an electric field to the mixed gas to generate plasma, the compound gas is decomposed to form a photoconductive layer, and then a liquid crystal layer is formed. A method of manufacturing a featured spatial light modulator. 8. A photoconductive layer having a wide bandgap for transmitting red light, a liquid crystal layer, and a region between these layers, in a region sandwiched between two transparent insulating substrates provided with transparent conductive electrodes. At least a plurality of island-shaped light reflecting mirrors provided in the same plane, and spatial light in which an intermediate layer made of germanium nitride or silicon germanium nitride is interposed between the photoconductive layer and the island-shaped light reflecting mirrors. A method for manufacturing a modulation element, wherein a nitrogen-containing compound gas containing at least germanium as a main component is used.
% Of the mixed gas is introduced into a vacuum container, an electric field is applied to the mixed gas to generate plasma, the compound gas is decomposed to form an intermediate layer, and then a liquid crystal layer is formed. A method of manufacturing a featured spatial light modulator.