JPH02106070A - Solid-state image sensing device - Google Patents

Abstract

PURPOSE:To realize high density, high sensitivity and high integration degree by connecting a photoconductive film turning to a photo detecting region with the gate region of a CMD constituting each picture element, and arranging the film on the upper part of the gate region. CONSTITUTION:A capacitor is constituted of a gate electrode 27, a transparent electrode 31 and a photoconductive film 30 sandwiched between them. The transparent electrode 31 constitutes charge modulation devices(CMD) and photo detectors in the form of a matrix, and constitutes row lines of a two-dimensional solid-state image sensing element. A source electrode 29 constitutes, in the similar manner, column lines of the solid-state element, thereby constituting a two dimensional CMD area sensor as a whole. As a result, photoelectric conversion is performed by a photoconductive film 30 formed on a gate electrode 27, so that spectral sensitivity all over the visible region is increased, and the aperture ratio of photo detecting part can be increased. Thereby high density, high sensitivity and high integration degree are realized.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a solid-state imaging device using a charge modulation element.

[Conventional technology]

Conventionally, as solid-state imaging devices, devices using charge transfer devices such as CODs and BBDs, devices using MOS transistors, and the like have been widely used. However, these solid-state imaging devices have problems such as charge leakage during charge transfer and low photodetection sensitivity.

In order to solve these drawbacks, the applicant has disclosed Japanese Patent Application Laid-Open No. 60-140752 and Japanese Patent Application Laid-Open No. 60-20606.
Publication No. 3 and Japanese Journal
of Applied Physics VOl, N
(L5 1985 'A NewMO5Photo
transistor operating in a
Non-Destructives Readout
The charge modulation element (Charge Mo
We have developed a solid-state imaging device using a dulatlon device (hereinafter abbreviated as CMD).

In these solid-state imaging devices using a CMD with an MIS gate structure, a readout method using a source-gate selection method is most promising in terms of pixel miniaturization.

Below, a light receiving element of an image device of a solid-state imaging device using a source-gate selection method using a CMD with a conventional MIS gate structure will be described.

FIG. 3 shows a cross-sectional view of each pixel of a CMD light-receiving element, which is a known solid-state imaging device proposed by Honkakuin. First, in this CMD light-receiving element, the structure, parameters, etc. explain. In Figure 3, I
I is a p-type doo> substrate, and the concentration of this substrate 11 is in the range of about 10'' to 10''cm-''. 12 is an n-type epitaxial layer deposited on the substrate 11 by an epitaxial method or the like. and forms an n-type channel region.The thickness of the n'' type epitaxial layer is about 5 to 10 μm.
The density is about 1 to 5×10 C14. On the surface of the n-type epitaxial layer, there are an n° type drain region 13 formed by a shallow diffusion layer, an n° type drain region 14 formed by a deep diffusion layer, and an n° source region 15 formed by a shallow expanded rP1FM. is provided. In this case, the n° type drain region 13 and the n° source region 15 are formed in a self-aligned manner with respect to a gate electrode, which will be described later.

The diffusion depth of the n'' drain region 13 is approximately 0.5a.
m or less. 16 is a gate insulating film formed on the surface of the n-type epitaxial layer, and its thickness is approximately 200 mm.
~1000λ. 17 is this gate insulating film 1
The gate electrode 17 is formed on the gate electrode 17, and the n° type drain region 13 and the n° source region 15 are formed in a self-aligned manner with respect to the gate electrode 17. Gate electrode 1
7 is made of, for example, polysilicon or the like and has a thickness of about 100 Å or less. 18 is an insulating film formed on the gate electrode 17, and 19 is a source electrode formed on the n° type source region 15.

Next, the operation of the CMD light receiving element will be briefly explained based on FIG. In the figure, a negative potential (not shown) is applied to the gate electrode 17.
Signal charges are generated by the incident light 20 incident from above, and the signal charges are accumulated on the surface of the n-type channel region 12 in the n-type epitaxial layer directly below the gate electrode 17. This accumulation of signal charges modulates the electron current flowing within the n-type channel region 12 between the n9-type source region 15 and the n-type drain regions 13 and 14.

[Problem to be solved by the invention]

In the conventional CMD, as shown in FIG. 3, the incident light 20 passes through the gate electrode i17 and enters the n-type channel region 12, so that all the incident light is
Due to this, the light intensity is attenuated before reaching the n-type channel region 12. This attenuation of light intensity results in a decrease in photosensitivity, which has the disadvantage that the decrease in blue sensitivity is particularly noticeable.

The second invention was made to eliminate the drawbacks of the conventional solid-state imaging device using a CMD, and aims to provide a solid-state imaging device using a CMD that is highly sensitive and easy to manufacture. It is.

[Means and effects for solving the problem] This invention has the following features:
A plurality of row lines to which a row selection signal is applied, a plurality of column lines to which a column selection signal is applied, one main electrode connected to the column line, and the other main electrode connected in common to the main electrode. CM consisting of a channel region and a gate region arranged
D, a capacitor connected between the gate region and the row line of the CMD, and a photoconductive film connected to the gate region, and the resistance value of the photoconductive film changes depending on the amount of incident light. Taking advantage of this, the gate potential of the CMD is changed to read the signal, thereby obtaining a video signal with high light receiving efficiency and high sensitivity over the entire wavelength range.

〔Example〕

Examples of the present invention will be described below.

FIG. 1(A) is a plan view showing the configuration of a first embodiment of a solid-state imaging device using a CMD according to the present invention as a light receiving element, and FIG. 1(B) is a cross-sectional view taken along the line xx'. It is a diagram.

Regarding this CMD light-receiving element, the structure, parameters, etc. of the device will be explained using an n-channel, similar to the one proposed by the applicant.

In FIGS. 1(A) and (B), 21 is P-type<1
00>, and the concentration of this substrate 21 is in the range of about 10'z to 10''cm-'.
This is an n-type epitaxial layer deposited on 1 by an epitaxial method or the like, and forms an n-type channel region. The thickness of the n-type epitaxial layer is about 5 to 10 μm, and the concentration is about 1 to 5×10'3 CI-3. Reference numeral 23 denotes an n° type source region formed on the surface of the n− type epitaxial layer. Reference numeral 24 denotes a P- type gate ion implantation region which is formed to surround this n'' type source region 23 and is slightly shallower than the source region.

This P-gate ion implantation region 24 is provided by a forming method already proposed by the applicant and disclosed in Japanese Unexamined Patent Publication No. 61-98764. 25 is n which is common to each pixel and is formed to separate the unit CMD constituting each pixel.
This drain region has a slightly deeper region than the P-gate ion implantation region 24.

26 is 3101% P S G (Phospho 5l
This is an insulating film made of licate glass or the like.

27 is a gate electrode made of metal such as molybdenum;
It is connected to the gate STI region 24 through a contact hole 28 formed in the insulating film 26. 29 is a source electrode connected to the source 23, and CM arranged in one direction.
The sources of group D are connected together. A photoconductive film 30 is formed on the gate electrode 27 and is made of amorphous silicon or a compound semiconductor such as Zn5e. Reference numeral 31 denotes a transparent electrode formed on the photoconductive film 30, and is arranged along a CMD group arranged in one direction perpendicular to the source electrode 29.

In the solid-state imaging device configured in this manner, the gate electrode 27, the transparent electrode 31, and the photoconductive film 30 sandwiched between them form a capacitor. Further, the transparent electrode 31 configures the CMD light receiving element in an I-IJ hook shape to configure the row lines of the two-dimensional solid-state image sensor, and the source electrode 29 similarly configures the column lines of this solid-state image sensor. , a two-dimensional CMD area sensor is constructed as a whole.

Next, the operation of the solid-state imaging device configured as described above will be explained.

First, when a voltage V, @ is applied to one row line 31, the pn junction between the gate and drain of the CMD connected to this row line is forward biased.

For this reason, gate electrode 27 - photoconductive film 30 - transparent electrode 3
A capacitor consisting of 1 is charged to a voltage (v#m-φB). Here, φB is the forward voltage of the pn junction. The above is the reset operation. After that, this line becomes 0■
Then, the voltage (v-m-φB) is maintained in the capacitor, and the potential of each gate of CMD is ■. is -(V, l-φB
).

In this state, if no light is incident, the gate potential V remains unchanged, but if light is incident, the resistance of the photoconductive film 30 decreases, the capacitor discharges, and the gate potential V6 increases. This potential increase is approximately proportional to the amount of light incident on each pixel. This is the accumulation operation.

In the read cycle, voltage 7 is applied to this row line.

Therefore, the gate potential of each CMD connected to this row line rises by an even greater amount. Therefore, as the column selection transistors are sequentially turned on by the column selection signal, a signal proportional to the incident light of each CMD is output from the video line C (not shown). An imaging operation is performed by repeating the reset, Na, and read operations.

As explained above, with the configuration shown in this example,
Although a solid-state imaging device capable of reading out video signals can be obtained,
According to this configuration, since photoelectric conversion is performed in the photoconductive film formed on the gate electrode, the spectral sensitivity is high over the entire visible range and has a desirable characteristic. In addition, the aperture ratio of the light-receiving portion is high (which makes it suitable for high density and high integration).

FIG. 2(A) is a plan view showing the configuration of still another embodiment, and FIG. 2(B) is a sectional view taken along the line xx'.

In this embodiment, an epitaxial layer 22 constituting a channel, a source region 23 of the CMD, and a P-type gate ion implantation region 24 are formed on a silicon substrate 21 constituting the back gate of the CMD. This is the same as the first embodiment.

In this embodiment, a thin St.
A region is formed in which a dielectric film 34 made of O, etc. and a capacitor electrode 35 are laminated. Then, each of these constituent parts P-type gate ion implantation region 24. dielectric 111
[34, The capacitor electrodes 35 form a capacitor, and the capacitor electrodes 35 arranged in one direction are connected to each other as shown in FIG. 2(A). The capacitor electrodes 35 are connected to each other as shown in FIG. 2(A). A gate electrode 27 is connected to the other part of the gate 9N region 24 through a contact hole 28.

The gate electrode 27 and the capacitor electrode 35 are connected to P
They are separated by a glabellar insulating film 36 made of SG or the like.

A photoconductive film 30 and a transparent electrode 3 are placed on the gate 1i pole 27.
1 is formed, but in this embodiment, the photoconductive film 30 and the transparent electrode 31 are formed in a negative pattern without forming a pattern. The capacitor electrode 35 and the source electrode 29 are configured to be orthogonal to each other and form a row line and a column line, respectively.

In the structure of the solid-state imaging device according to this embodiment, the capacitor electrodes 35 form row lines, the source electrodes form column lines, and each gate region 24 of the CMD forming each pixel is provided with a photoconductive film 30, a transparent A capacitor consisting of electrodes 31 is connected.

The uniformly formed transparent electrodes 31 constituting the external electrodes of these capacitors are connected to a target power supply ■
7 is connected.

Next, the operation of the solid-state imaging device having the circuit configuration as described above will be explained.

First, when a voltage v2 is applied to one row line, the pn junction between the gate and drain of the CMD of this line is forward biased, and the gate L fiJl region 24 - dielectric film 34 -
The capacitor consisting of the capacitor electrode 35 has (v pc
-φB). Next, this line is 0■
Then, the gate potential of each CMD becomes = (■2-φB). If light is incident after this, the resistivity of the photoconductive film 30 decreases, so the target power supply ■ is applied to the gate 6M region 24 of each CMD. 7 through the transparent electrode 31 and the photoconductor 130.
As the ice flows, the gate potential of each CMD rises. This potential increase is approximately proportional to the amount of light incident on each pixel.

After the read cycle, the voltage V# is applied to the row line.

is added, and the gate potential of each CMD further increases by V. Therefore, as the column selection transistors are sequentially turned on by the column selection signal, the CMD signal is output from the video line.

Thereafter, one screen of video signals is sequentially read out in the same manner.

This embodiment has the advantage of being easy to manufacture because it does not require patterning of the photoconductive film and the transparent electrode.

〔Effect of the invention〕

As explained in detail above, in this invention, the photoconductive film serving as the light receiving area is connected to and disposed above the gate area of the CMD constituting each pixel, so that even if the pixel size is miniaturized, It is possible to obtain a solid-state imaging device that has high light reception efficiency, can increase sensitivity over the entire wavelength range of visible light, and is suitable for high-density and high-sensitivity color imaging.

Further, in the imaging device according to the present invention, there is no signal mixing with other pixels, so that the effects of high resolution and no color mixture during color imaging can be obtained.

[Brief explanation of the drawing]

FIGS. 1(A) and 1(B) are a plan view and a sectional view showing an embodiment of a solid-state imaging device according to the present invention. FIGS. 2(A) and 2(B) are a plan view and a sectional view showing another embodiment of the solid-state imaging device according to the present invention. FIG. 3 is a sectional view of a conventional solid-state imaging device. 21--...------Silicon substrate 22-
・−・・−・・n− type channel region 23−・−
・−・・−・−n゛ type source region 24・−・・−・−
...--p-type gate, ion implantation region 25...-
・・−・−・・−n゛ type drain region 26−−−−−
−・・−・−・−・Insulating film 27・・−・・−・−・
-Gate electrode 30--1--Photoconductive film 31--Transparent electrode (B)

Claims (1)

[Claims] 1. A plurality of row lines to which a row selection signal is applied, a plurality of column lines to which a column selection signal is applied, and one main electrode connected to the column line are connected in common. a charge modulation element constituting a pixel including a channel region and a gate region disposed between the other main electrode; a capacitor connected between the gate region of the charge modulation element and the row line; A solid-state imaging device comprising: a photoconductive film connected to the gate region. 2. The solid-state imaging device according to claim 1, wherein the capacitor is constituted by the gate region, the row line, and a photoconductive film disposed between them. 3. The capacitor is composed of the gate region, the row line, and an insulating film disposed between them, and the photoconductive film connected to the gate region has a transparent electrode to which a target voltage is applied. 2. The solid-state imaging device according to claim 1, further comprising a solid-state imaging device.