JP3134785B2 - Reflective image display - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reflection type image display device for displaying an image on a large screen, and has a problem that a part of readout light enters an active element substrate to adversely affect image display characteristics. It relates to a structural improvement to eliminate it.

[0002]

2. Description of the Related Art Recently, there has been an increasing demand for a projection type display device for displaying an image on a large screen, such as a display for outdoor public use or a traffic control operation, or a display for displaying a high-definition image such as a high definition image. ing. Projection display devices are roughly classified into a transmission type and a reflection type.The former is a method of projecting light transmitted through a liquid crystal panel in which pixels formed of thin film transistors and transparent electrodes are arranged in a matrix, The latter is a method of projecting the light reflected by the above-mentioned liquid crystal panel, but the most important issue in a projection display device is to display an image with high luminance.

The transmissive type has an advantage that the configuration of the optical system is relatively simple and can be manufactured at a low cost. However, when the display panel is miniaturized, the area occupied by the transistors and the wiring for controlling the voltage of the pixel electrode increases. Therefore, there is a disadvantage that the aperture ratio is reduced and the brightness of the image is reduced. on the other hand,
In the reflection type, a transistor and a wiring can be arranged below the reflective electrode layer. Therefore, the number of pixels can be increased without lowering the aperture ratio, and a high-luminance, high-resolution image can be displayed. Therefore, for an image display apparatus of the enlargement projection system, the reflection type system which is compact and capable of increasing the density is more suitable.

A reflection type image display device generally employs a structure as shown in FIG. In the figure, 1 is an active element substrate, 2 is a transparent substrate, 3 is an active element substrate 1
And a liquid crystal layer (light modulation layer) sandwiched between the transparent substrate 2 and. The active element substrate 1 has a matrix of active circuits for one pixel in which a MOS-FET 5 serving as a switching element and a reflective electrode layer 6 are connected to an output terminal (drain) thereof on the surface of a Si substrate 4. Each of the MOS-FETs 5 has a structure in which a signal line 7 and a scanning line 8 each formed of a conductor pattern are connected to a source and a gate of the MOS-FET 5, respectively. On the other hand, the transparent substrate 2
Has a structure in which a transparent common electrode film 10 is formed on one surface of a transparent glass substrate 9. Therefore, the entire device has an equivalent circuit as shown in FIG. 11, but by controlling the energization of the scanning signal to the scanning line 8 by the vertical address circuit 11 and the image signal to the signal line 7 by the horizontal address circuit 12, The potential difference applied between the reflective electrode layer 6 and the common electrode film 10 is controlled for each pixel, and the reading light incident on the glass substrate 9 is changed for each pixel based on a change in the light transmittance of the liquid crystal layer 3 due to the potential difference. The modulation is performed to obtain modulated reflected light corresponding to the field image signal as the whole panel. Incidentally, reference numeral 13 in FIG. 11 denotes an auxiliary capacitance formed between the reflective electrode layer 6 and the Si substrate 4. In some cases, the capacitance of the liquid crystal layer 3 alone is provided as an additional capacitance because the charge holding time is short. Many.

[0005] A more specific operation will be described as follows. First, the scanning signal is applied to the MOS-FET 5 through the scanning line 8.
When the MOS-FET 2 is turned on, the MOS-FET 2 is turned on. When the image signal of the signal line 7 is applied to the reflective electrode layer 6 from the source to the drain through the drain in this state, the liquid crystal layer 3 and the storage capacitor 13 are charged. Then, even if the scanning signal of the scanning line 8 becomes 0 level, the charged electric charge of the liquid crystal layer 3 and the auxiliary capacitance 13 is the potential of the reflection electrode layer 5 for a time determined by a time constant determined by the total capacitance and the discharge resistance. The time constant is set so that the holding time is longer than the field scanning time. Therefore, while sequentially scanning in the vertical direction with the scanning line 8 and writing an image signal from the signal line 7 in synchronization with the scanning, the potential difference between the common electrode film 10 and the reflective electrode layer 6 of each pixel is written. An image can be displayed with reflected light that changes in response to a signal and that modulates readout light on a pixel-by-pixel basis.

In the above-mentioned reflection type image display device, as shown in FIG. 10, since the reflection electrode layer 6 is separated for each pixel, a part of the readout light is generated by the gap between the reflection electrode layers 6. Penetrates into the Si substrate 1 to generate a large number of photocarriers (pairs of electrons and holes) in the Si substrate 1, and the photocarriers lower the potential of the reflective electrode layer 6 to cause deterioration of a displayed image. The problem of so-called "photoconduction" has been pointed out.

This photoconduction is described as follows. First, FIG. 12 is an enlarged cross-sectional view showing the structure of a pixel display unit according to the reflection type image display device. In FIG. 12, each component indicated by the same reference numeral as that used in FIG. 10 and FIG. Is equivalent to As shown in FIG. 12, the MOS-FET 5 has a source 5s and a drain 5d as an N-type diffusion layer on the surface of a P-type Si substrate 4 and an oxide film (SiO ₂ ) 14 formed on the surface. Is formed by forming a gate 5g. The signal line 7 is connected to the source 5s through the oxide film 14, and the scanning line 8 is connected to the gate 5g, but they are embedded in the insulator layer 15 covering the upper side of the oxide film 14. The flat reflective electrode layer 6 formed on the surface side of the insulator layer 15 and the drain 5d formed on the side of the Si substrate 4 have a columnar connection portion 16 penetrating the insulator layer 15 and the oxide film 14. It is made conductive and connected by.

As described above, since the reflective electrode layer 6 is formed in pixel units, there is a gap between the reflective electrode layer 6 and an adjacent reflective electrode layer, and as shown by a dotted line with an arrow in FIG. The projected read light is transmitted through the gap to the Si substrate 4.
To generate photocarriers. In this case, MOS
-Since the FET 5 is configured as an N-channel type with respect to the P-type Si substrate 4, the Si substrate 4 is maintained at the GND potential, and the drain 5d as the N-type diffusion layer is set at a positive potential corresponding to the image signal. Is done. That is, the PN junction surface between the Si substrate 4 and the drain 5d is in a reverse bias state. Therefore, the holes in the photocarriers are absorbed by the Si substrate 4 due to the GND potential, but the electrons flow into the drain 5d through the PN junction surface, and the holes in the reflective electrode layer 6 connected to the drain 5d. Reduce the potential. As a result, the potential difference between the reflective electrode layer 6 and the common electrode film 10 shifts from the normal potential difference corresponding to the image signal, causing a change in the light modulation effect of the liquid crystal layer 3 and causing deterioration in the displayed image.

Here, with respect to the above-mentioned photoconduction phenomenon, it will be specifically estimated how much potential drop occurs. Now, R in the reading light of intensity P [W / cm ² ]
[%] Enters the Si substrate 4, and the entering light generates photocarriers with a quantum efficiency of 100%. In this case, one pixel region [X] is generated in one field cycle [1/60 (sec)].
In * X (cm ² )] units, N electrons = P * X ² * (1/60) * (R / 100) * r / (h * c) are generated. Here, r is the wavelength of reading light [cm], h
Is Planck's constant [= 6.63 / 10 ³⁴ (J * sec)], c is the speed of light
[= 3 * 10 ¹⁰ (cm / sec)]. Assuming that the relative permittivity of the liquid crystal of the liquid crystal layer 3 is d and the thickness is L [cm], the capacitance of the liquid crystal per pixel is C [F] = s * d * (X ² / L). Where s is the dielectric constant of vacuum [= 8.85 / 10 ¹⁴ (F /
cm)]. Therefore, the potential of the reflective electrode layer 6 becomes dV [V] = (N * q) /C=1.51*10 ¹³ * P * r * (L / d) ... will decrease by Here, q is the electron charge amount [=
1.6 / 10 ¹⁹ (C)].

Therefore, as an example of operating conditions of a general reflection type image display device, P = 10 [W / cm ² ] and R = 0.00.
1 [%], r = 5000/10 ⁸ [cm], L = 5/10 ⁴ [cm],
Substituting d = 10 into the above equation gives dV = 37.8
[V] is obtained. Actually, as described above, the auxiliary capacitance 13 which is about 10 times that of the liquid crystal capacitance is added in parallel with the liquid crystal capacitance.
In that case, dV = 3.78 [V]. From the above results, even if a very small amount of light, 1/10 ^{4 of} the readout light, enters the Si substrate 4, the potential of the reflective electrode layer 6 shifts by several volts, and the effect of photoconduction cannot be ignored. Can understand.

On the other hand, the following various proposals have conventionally been made as countermeasures against photoconduction in a reflection type image display device. (1) On the surface of the active element substrate side, a multilayer reflective film in which amorphous Si and an insulating film are laminated is provided (Japanese Patent Publication No. 4-51070). In this proposal, unnecessary parasitic capacitance does not occur because a dielectric is used. (2) A low-reflectance film such as titanium is laminated on the surface of a wiring conductor such as a signal line to prevent irregular reflection of read light. A light-shielding layer made of a metal film is provided below the reflective electrode layer (Japanese Patent Publication No.
43712). (3) A region other than the switching element formation region of the semiconductor substrate is doped at a high concentration and the lifetime of the optical carrier is shortened, so that even if the optical carrier is generated, it is recombined before reaching the switching element. It will disappear (Japanese Patent Publication No. 4-34313). (4) A so-called “well structure” in which the upper layer and the lower layer of the semiconductor substrate are of the opposite conductivity type is applied, and one of the photocarriers is absorbed in the upper well and the other is absorbed in the lower substrate body (Japanese Patent Laid-Open No. 3-2).
88474).

[0012]

As described above, the occurrence of photoconduction in a reflection type image display device is a very important issue in maintaining a high quality display image, and various measures have been taken as described above. Proposed. However, these photoconduction measures also have the following problems. Regarding (1): This measure is to alternately stack two (or more) films with different refractive indices, and to construct an ideal reflection film as a whole by using multiple reflection at each interface. It is necessary to precisely control the film thickness and the refractive index of each film, thereby lowering the production yield and increasing the cost. B. In principle, the film that can reflect 100% is It is only light of a specific wavelength determined by the thickness and the refractive index. In the case of colorization, it is necessary to adjust the film thickness and the refractive index for each color, which causes an extremely difficult problem. There is a problem that the reflectivity decreases if there is a deviation or variation in the corners, and d. If the layer thickness of the multilayer reflective film increases, the potential difference applied to the liquid crystal layer decreases, requiring a higher driving voltage. Regarding (2): Only suppression of multiple reflection and scattered light in the active element portion cannot prevent light entering the semiconductor substrate, and is not a fundamental measure but an auxiliary measure. Regarding (3): In the manufacturing process of the device, complicated steps such as an epitaxial step are interposed, which causes a decrease in yield and an increase in cost.

Regarding (4); for example, as shown in FIG. 13, a P-type well 4a is formed on the surface side of an N-type Si substrate 4, and an N-channel type MOS-FET 5 is formed in the well 4a. The well 4a is set to the GND potential, the substrate body 4b is set to the positive bias potential, holes in the photocarriers generated below the bottom of the well 4a are set to the well 4a side, and electrons are set to the substrate body 4b. It is a method to make it absorb on the side. However, according to this method, as shown in FIG. 13, even though it is effective for light penetrating to the lower side of the well 4a, the optical carrier generated by the light absorbed by Si in the well 4a has Again, it is absorbed by the drain 5d. The amount of photocarriers reaching the drain 5d depends on the depth of the well 4a, but at a normal depth of the well 4a (for example, about 3 μm), a considerable percentage of photocarriers flow into the drain 5d. Resulting in. In particular, the shorter the wavelength of the light, the higher the ratio of absorption in the well 4a, and in this method, the degree of photoconduction is greater for blue light.

Accordingly, the present invention provides a structure of a reflection type image display device which enables a photo-conduction countermeasure without deriving a new problem as seen in the prior art,
It was created for the purpose of enabling higher quality image display.

[0015]

According to the present invention, a switching element, an insulating layer covering the switching element, a reflective electrode layer formed on the surface of the insulating layer, and a structure penetrating the insulating layer are provided on a substrate surface. A large number of active element circuits for one pixel, each of which is composed of a connection part for connecting the reflection electrode layer and the output terminal of the switching element, are arranged in a matrix, and the input terminal and the control terminal of each switching element are arranged in a matrix. An active element substrate having signal lines and scanning lines connected thereto, a transparent substrate having a transparent common electrode film formed on one surface, a reflective electrode layer side of the active element substrate, and a common electrode film of the transparent substrate And a light modulation layer sandwiched between the reflective electrode layer and the common electrode film in response to an input signal to an input terminal while controlling the on / off of the switching element. In the reflection type image display device in which light incident on the transparent substrate is modulated by the light modulation layer and reflected, the substrate on the active element substrate side is moved from the surface of the substrate to the depth Dw by the first conductivity type. A well structure composed of a layer of a second conductivity type semiconductor having a conductivity type opposite to that of the substrate body, which is a semiconductor, and each of the switching elements is formed in the well, and the well is formed at an intermediate position between the connection portions. In a plan view seen from the incident direction of the readout light, a flange-shaped light-shielding layer is formed integrally with the connection portion, the flange-like light-shielding layer greatly extending outside the output terminal formation region of each switching element by a distance X, and the depth Dw X / Dw ≧
The present invention relates to a reflection-type image display device characterized in that it is set to 0.2.

According to the present invention, a flange-shaped light-shielding layer is integrally formed at a part of a connecting portion for connecting the reflective electrode layer and the output terminal of the switching element, and covers just above the output terminal formation region of the switching element. Light that has entered through the gap between the reflective electrode layers is prevented from directly entering the output terminal of the switching element. Further, the active element substrate employs a well structure similarly to the device shown in FIG. 13. Even if light not blocked by the light shielding layer enters a position deeper than the well of the substrate body, the optical carrier due to the penetrated light is used. 13 does not flow into the output terminal of the switching element, and the condition of X / Dw ≧ 0.2 is set for the optical carrier generated in the well, which is a problem in the apparatus of FIG. By drastically reducing the probability of flowing into the switching element,
The effect of the optical carrier is prevented from appearing in the display image.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the "reflective image display device" of the present invention will be described below in detail with reference to FIGS. << Embodiment 1 >> First, FIG. 1 is an enlarged cross-sectional view of the structure of a pixel display unit according to the device of this embodiment, and FIG. 2 is a plan view of FIG. 1 taken along a line YY. Each component indicated by the same symbol as the symbol used in FIGS. 10 to 13 corresponds to the same element. The device of this embodiment has a Si substrate 4 having a well structure as in the device of FIG.
A P-type well 4a is formed on the surface side of an N-type Si substrate 4, and an N-channel MOS-FET 5 is formed in the well 4a. The well 4a is held at the GND potential, and the substrate body 4b side is set at the positive bias potential.

The features of this embodiment are as follows.
A flange-shaped light-shielding layer 20 is provided just above the oxide film 14 at the connection portion 16.
The constituent region of the light-shielding layer 20 has a drain 5d of the MOS-FET 5 in a plan view as viewed from the read light incident direction.
A distance X outside the formation region of
And when the depth of the well 4a is Dw, X / Dw ≧ D / Dw between the depth Dw and the distance X of the light shielding layer 20.
The point is that Dw and X are set so that the relationship of 0.2 is established. Although the light-shielding layer 20 covers the drain 5d with the above-mentioned spread in a plan view, when the whole is formed in a plate shape, the light-shielding layer 20 is formed on the gate 5g formed on the surface of the oxide film 14 or directly above the gate 5g. Since a region in which the scanning line 8 is formed is in contact with a region where the scanning line 8 is formed, a stepped portion is interposed therebetween so as to avoid the gate 5g and the scanning line 8 so as to cover the upper side thereof. Here, the light-shielding layer 20 is made of Al or an Al alloy such as AlSi or AlSiCu which is the same material as the reflective electrode layer 6 and the connection portion 16, and the sputtering method and the area setting mask are used in the manufacturing process similarly to the reflective electrode layer 6. Can be formed by etching or the like without using any special process.

Next, the relationship between the depth Dw of the well 4a and the distance X of the light-shielding layer 20 formed outside the region of the drain 5d will be considered. First, in the device of this embodiment, the read light that penetrates the liquid crystal layer 15 through the gap between the reflective electrode layers 6 and enters the Si substrate 4 side from the periphery of the drain 5d due to the interposition of the light shielding layer 20. Even if the light can penetrate only into a region as far as the distance X, and even if the penetrating light reaches deeply to the substrate main body 4b below the well 4a, the optical carrier generated in the substrate main body 4b will not Since the holes are absorbed by the well 4a and the electrons are absorbed by the substrate body 4b, the problem of photoconduction does not occur.

The problem is the photocarriers generated in the well 4a, but FIG. 3 shows a distance X from the periphery E of the drain 5d.
FIG. 3 is a schematic diagram when it is assumed that an optical carrier is generated at a position G separated only by a distance. The optical carrier is a well 4a having a depth of Dw.
Diffuses in a random direction, but passes through the lower side of the point E and flows directly into the peripheral surface of the drain 5d, and diffuses below the drain 5d and flows in from the lower side of the drain 5d. The electrons cause photoconduction. FIG.
Is a geometrical assumption diagram for calculating the probability that electrons flow into the drain 5d, and it is assumed that only those electrons that linearly diffuse and pass through the shaded region S flow into the drain 5d. Here, the height of the shaded region S is assumed to be half of the depth Dw of the well 4a (= Dw / 2) by averaging the inflow path to the drain 5d as described above, and the width is defined by the side and the point G. Is set to be the electron diffusion distance Ld.

In FIG. 4, the probability P (X) that electrons flow into the drain 5d is obtained by dividing the solid angle from the point G into the shaded area S by the total solid angle 4π, which is given by the following equation 1. .

[0022]

(Equation 1)

Where φ is the angle in the horizontal direction with respect to the perpendicular drawn from point G to the hatched area S in FIG. 4, α = X / D
w and φ0 are arccos (X / Ld).

Then, by substituting the typical values of Dw = 3 μm and Ld = 50 μm, the above equation 1 is calculated, and α is plotted on the horizontal axis.
When a graph was created by taking (= X / Dw) and logP (X) on the vertical axis, a result as shown in FIG. 5 was obtained. As is clear from the figure, under the condition of X / Dw ≧ 0.2, logP (X) ≦
−0.7, and P (X) can be suppressed to 0.2 or less, and if X / Dw ≧ 1, P (X) can be reduced to 0.1 or less.

Therefore, the area of the light-shielding layer 20 is defined as X / Dw ≧ 0.2.
If the photoconductor is designed under the conditions described above, the probability that photocarriers will flow into the drain 5d even if generated in the well 4a can be reduced to 20% or less, so that the display image of the reflective image display device is not substantially affected. , Which is an extremely effective countermeasure for photoconduction. The effect becomes more remarkable when the distance X is increased. However, the light-shielding layer 20 is formed in pixel units. There is a limit.

Further, according to this embodiment, since the light-shielding layer 20 extends around the drain 5d when viewed from the incident direction of the readout light, the capacitance between a part of the region and the well 4a is reduced by the liquid crystal layer 15 It can be configured as a parallel auxiliary capacitor 13.

Embodiment 2 FIG. 6 is an enlarged cross-sectional view of the structure of the pixel display unit according to the device of this embodiment, and FIG. 7 is a cross-sectional view taken along the line YY. As shown in the figures, the basic structure of this embodiment is the same as that of the first embodiment (FIG. 1), but the well 4a of the first embodiment has a depth D over the entire surface of the substrate body 4b.
w, whereas in this embodiment each MO
It is characterized in that it is formed separately for each formation region of S-FET5. That is, P-type wells 21 are individually formed for each pixel on the N-type Si substrate 4, and an N-channel type MOS-FET 5 for each pixel is formed in each well 21. During operation, each well 21 is set to the GND potential and the substrate body 4b is set to the positive bias potential, as in the first embodiment.

If the wells 21 are formed separately as in this embodiment, the light-shielding layer 20 covers the formation region of the well 21 on the drain 5d side in a plan view as seen from the incident direction of the readout light. The region where the readout light enters is only the N-type region outside the well 21. Electrons of photocarriers generated in the N-type region are absorbed by the substrate body 4b set to the positive bias potential, and the holes are GND. Well 21 set to potential
Is absorbed by Therefore, the generation of photocarriers in the well 21 can be prevented at a previous stage, and even if light enters the well 21, the flow of photocarriers into the drain 5 d can be suppressed according to the principle of the first embodiment. The potential shift of the reflective electrode layer 6 can be further reduced by a double photoconduction measure.

The wells 21 shown in FIGS. 6 and 7 are separated from each other for each pixel, but as shown in FIG.
The well 22 may be separately formed so as to collectively include the formation regions of the MOS-FETs 5 corresponding to the pixels in the row direction, or the formation regions of the MOS-FETs 5 corresponding to the pixels in the column direction (not shown) may be collectively formed. The same effect as described above can be obtained even if it is separated and formed so as to include.

In the first and second embodiments, the N-type Si substrate 4 is used.
Has been described, a P-type Si substrate may be used. In this case, the wells 4a and 21 are formed of N-type, the substrate body 4b side is set to the GND potential, and the wells 4a and 21 are formed.
At a positive bias potential.

<< Embodiment 3 >> FIG. 9 is an enlarged sectional view of the structure of the pixel display section according to the device of this embodiment. As shown in the drawing, this embodiment is different from the reflective electrode layer 6 and the connection portion 16 in FIG.
The structure of the light-shielding layer 20 and the well structure of the Si substrate 4 are the same as those of the first embodiment (FIG. 1), but the upper surface of the light-shielding layer 20 and the surface of the signal line 7 are made of a material having low surface reflectance. Coating23,24
The feature is that it is given. Here, as a material of the coatings 23 and 24, titanium, titanium oxide, titanium nitride, titanium oxynitride, or the like can be adopted. In the process of forming the light shielding layer 20 and the signal line 7, those metals are thinned by sputtering. It can be formed and etched by using the same pattern as the light shielding layer 20 and the signal line 7.

In the structure of FIG. 1, an adjacent reflective electrode layer
The readout light incident from the gap of No. 6 is transmitted to the Si substrate as described above.
In addition to directly penetrating into the Si substrate 4 side, multiple reflection occurs between the surface of the signal line 7 or the light shielding layer 20 made of aluminum or an aluminum alloy and the lower surface of the reflective electrode layer 6. There is also a path, and the photoconduction due to the multiple reflected light cannot be ignored.

According to this embodiment, the coating is formed as described above.
By performing the steps 23 and 24, the multiple reflection light can be attenuated in the reflection process, and the penetration of the multiple reflection light into the Si substrate 4 can be suppressed, so that a more detailed measure of photoconduction can be realized. In this embodiment, the coatings 23 and 24 are applied only to the light shielding layer 20 and the upper surface of the signal line 7. However, from the viewpoint of attenuating the multiple reflection light, the lower surface of the reflection electrode layer 6 and the scanning line 8 are not used. It is even more effective if a similar coating is applied to the upper side surface of the. Further, it goes without saying that this embodiment can be applied not only to the configuration of the first embodiment but also to the configuration of the second embodiment.

[0034]

The reflection type image display apparatus of the present invention has the following effects by having the above configuration. According to the first and second aspects of the present invention, a switching element of an active element substrate is formed in a well, and a flange-shaped light-shielding layer is provided at a connection portion connecting a reflective electrode layer and an output terminal of the switching element. By setting the relationship between the depth Dw and the spreading distance X of the light-shielding layer to the outside of the output terminal of the switching element to be X / Dw ≧ 0.2, photocarriers generated in the well flow into the output terminal of the switching element. Is suppressed within a range that does not substantially affect the quality of the displayed image, and extremely effective photoconduction measures can be taken. In particular, when readout light having a short wavelength is used, generation of photocarriers in the well becomes remarkable. However, the present invention can be rationally solved without intervening a particularly difficult step in manufacturing. According to the third aspect of the present invention, it is possible to configure a storage capacitor using a light shielding layer. According to the fourth aspect of the invention, the well is formed separately for each of the formation regions of the switching elements or for each of the alignment regions in the row direction or the column direction, so that the read light does not directly enter the well, thereby being more effective. Realizing photoconduction measures. According to the fifth and sixth aspects of the present invention, the light reflected by the light shielding layer is attenuated in the reflection process against the phenomenon of multiple reflections and entering into the substrate, thereby enabling more detailed measures for photoconduction. I do.

[Brief description of the drawings]

FIG. 1 is an enlarged cross-sectional view of a pixel display unit of a reflective image display device according to a first embodiment of the present invention.

FIG. 2 is a sectional view taken along the line YY in FIG.

FIG. 3 is a schematic diagram showing a state in which photocarriers are generated at a position separated by a distance X from the periphery of a drain.

FIG. 4 is a geometric assumption diagram for calculating a probability that electrons flow into a drain.

FIG. 5: X / Dw (X; constituent region of light shielding layer is MOS-FET
Distance extending outside the drain formation region, D
6 is a graph showing the relationship between w (well depth) and the probability (logarithm) of electrons flowing into the drain.

FIG. 6 is an enlarged cross-sectional view of a pixel display unit of the reflection type image display device according to the second embodiment.

FIG. 7 is a sectional view taken along the line YY in FIG. 6;

FIG. 8 is a cross-sectional view taken along the line YY in a case where a well is separately formed so as to collectively include a formation region of each MOS-FET corresponding to a pixel in a row direction in the second embodiment.

FIG. 9 is an enlarged cross-sectional view of a pixel display unit of a reflective image display device according to a third embodiment.

FIG. 10 is a perspective view (main part broken) showing a general structure of the reflection type image display device.

FIG. 11 is an equivalent circuit diagram on the active element substrate side.

FIG. 12 is an enlarged cross-sectional view of a pixel display unit of a reflection type image display device according to the related art.

FIG. 13 is an enlarged cross-sectional view of a pixel display portion when a Si substrate has a well structure in a reflection-type image display device according to a conventional technique.

[Explanation of symbols]

1 Active device substrate, 2 Transparent substrate, 3 Liquid crystal layer (light modulation layer), 4 Si substrate (substrate), 4a, 21, 22 well, 4b Substrate body, 5 MOS-FET (switching element ), 5s: source, 5g: gate, 5d: drain, 6: reflective electrode layer, 7: signal line, 8: scanning line, 9: glass substrate, 10: common electrode film, 11
... vertical address circuit, 12 ... horizontal address circuit, 13 ... auxiliary capacitance, 14 ... oxide film, 15 ... insulator layer, 16 ... connection part, 20 ... light shielding layer, 23, 24 ... film, E ... periphery of drain, G ... Position where photocarriers are generated, Dw ... Well depth, X ... Distance where the constituent region of the light-shielding layer extends outside the drain-forming region of the MOS-FET.

Continuation of the front page (56) References JP-A-58-2871 (JP, A) JP-A-63-63086 (JP, A) JP-A-8-6000 (JP, A) JP-A-8-76145 (JP, A) JP-A-9-203884 (JP, A) JP-A-55-95980 (JP, A) JP-A-55-9517 (JP, A) JP-A-57-66472 (JP, A) 57-20778 (JP, A) Japanese Utility Model Showa 60-8983 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) G02F 1/1368 G02F 1/1333 500

Claims (6)

(57) [Claims] 1. A switching element, an insulator layer covering the switching element, a reflective electrode layer formed on the surface of the insulator layer, and the reflective electrode layer penetrating the insulator layer on the substrate surface. A large number of active element circuits for one pixel, each of which is a connection unit for connecting the output terminal of the switching element, are arranged in a matrix, and the signal lines and the scanning lines respectively connected to the input terminal and the control terminal of each switching element. An active element substrate having lines formed thereon, a transparent substrate having a transparent common electrode film formed on one surface, and a transparent electrode layer sandwiched between the reflective electrode layer side of the active element substrate and the common electrode film side of the transparent substrate. A light modulation layer, and controls the on / off of the switching element to generate a potential difference between the reflective electrode layer and the common electrode film in response to an input signal to an input terminal. In a reflection type image display device in which incident light is modulated by a light modulation layer and reflected, the substrate on the side of the active element substrate is electrically conductive from a surface of the substrate to a depth Dw opposite to a substrate body which is a first conductivity type semiconductor. A well structure composed of a layer of a second conductivity type semiconductor that is a mold, and each of the switching elements is configured in the well;
A flange-shaped light-shielding layer, which is greatly expanded by a distance X outside the output terminal formation region of each switching element in a plan view seen from the incident direction of the read light at an intermediate position between the connection parts, is integrated with the connection part. Wherein the relationship between the depth Dw and the distance X is X / Dw ≧ 0.2. 2. The connection part and the light-shielding layer formed integrally therewith are made of aluminum or an aluminum alloy.
Reflective image display device. 3. The reflection-type image display device according to claim 1, wherein an auxiliary capacitance is formed between a portion of each light-shielding layer that extends outside an output terminal forming region of each switching element and a surface of the substrate body. 4. The reflection type according to claim 1, wherein the wells are formed separately for each of the formation regions of the switching elements or for each of the alignment regions of the switching elements in the row direction or the column direction. Image display device. 5. The reflection type image display device according to claim 1, wherein at least one surface of each light shielding layer is covered with a film having a low surface reflectance. 6. The reflection type image display device according to claim 5, wherein the coating having a low surface reflectance is any one of titanium, titanium oxide, titanium nitride and titanium oxynitride.