JPH0463590B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an improvement in an imaging device used for image detection. [Technical background of the invention and its problems] Recently, various semiconductor elements have been used in imaging devices that detect images. Conventional semiconductor devices capable of image detection accumulate signals from multiple photodetectors in an MIS structure coupled to these detectors,
A charge-coupled device (CCD) that sequentially transfers this to the adjacent MIS structure, a charge injection device (CID) that sequentially injects the charges accumulated in the MIS type photodetector into the substrate,
Directly connect a MOS transistor switch to the photodetection board, and sequentially switch the photodetection board with the switch.
MOS type sensors and the like are known. However, this type of device has the following problems. That is, in MOS type sensors and CIDs, since the switching element and the photodetector are directly connected, noise at the time of switching is likely to enter the signal line. Furthermore, CID has the disadvantage that the optical signal storage time for reading out the optical signal differs from element to element. On the other hand, although CCDs are superior to other devices in terms of noise, they have drawbacks such as the signal amount decreases as the transmission distance increases, random access is not possible, and a defect in one element becomes a line defect. . For this reason, MOS type sensors, CIDs, CCDs, etc. require complex signal processing circuits to alleviate the above-mentioned problems. In addition, CID requires a high-speed transfer circuit in order to reduce changes in storage time between elements. [Object of the Invention] An object of the present invention is to provide an imaging device that can increase the SN ratio, eliminate sensitivity changes between elements, and perform random access. [Summary of the Invention] The gist of the present invention is to add a readout switch element to a conventional CCD to realize a randomly accessible structure. That is, the present invention provides an imaging device used for image detection, in which a plurality of light receiving sections are arranged on a semiconductor substrate, and a plurality of MIS structures for accumulating and transferring charges of these light receiving sections are arranged adjacent to each light receiving section. A plurality of output parts into which charges transferred from these MIS structures are injected are provided adjacent to each structure, and gate control voltages of each of the MIS structures are switched respectively. A plurality of switch elements are provided to selectively control charge transfer to the output section. [Effects of the Invention] According to the present invention, the SN ratio can be made as high as that of conventional CCDs, and
Random access can be performed in the same way as . Furthermore, compared to CID, it is possible to obtain effects such as easier design of the drive circuit. Also, traditional
Since the transfer distance is shorter than that of CCD, the signal does not become smaller even if the transfer efficiency is low. High-density, high-sensitivity devices have become possible. [Embodiment of the Invention] FIG. 1 is a plan view showing one pixel portion of an imaging device according to an embodiment of the present invention, and FIG. 2 is a cross section taken along arrows A-A and B-B in FIG. and a diagram schematically showing a CC cross section. In the figure, 1 is a P-type Si substrate (semiconductor substrate), 2 is a gate oxide film, and Si substrate 1
An input diode (light receiving section) 3 that performs phosphorus diffusion is formed on the top. At a position adjacent to the input diode 3, there are transfer gates 4, 5, and 6.
A MIS structure section 7 is formed. This MIS structure section 7 accumulates and transfers photocharges detected by the input diode 3. On the opposite side of the input diode 3 adjacent to the MIS structure section 7 , an output diode (output section) 8 in which phosphorus is diffused is formed. This output diode 8 is a MOS transistor consisting of a gate 9, a source 10, and a drain 11.
Connected to gate 9 of transistor 12 . The drain 11 is connected to a signal line. On the other hand, the transfer gate 5 of the MIS structure section 7 is
D type dual gate consisting of gate 13, Y gate 14, drain 15 and source 16
It is connected to the drain 15 of the MOS transistor (switch element) 17 . MOS transistor 17
The source 16 of is connected to the ground line, and the drain 15
is connected to the power supply line via a resistor 18. In addition, each gate 13, 14 of the MOS transistor 17
are connected to address lines in the X direction and the Y direction, respectively. In addition, 21 in the figure is an overflow drain, 22
2 is an overflow gate, 23 is a reset gate, 24 is a reset drain, and 25 is a channel stopper. In addition, the input diode 3, the MIS structure section 7 , the output diode 8 and
One pixel section consists of MOS transistors 12 , 17 , etc.
A large number of them are two-dimensionally arranged on the Si substrate 1 in the X direction and the Y direction. Furthermore, MOS transistor
Each of the 17 gates 13 and 14 is connected to an intersection between an X-direction address line and a Y-direction address line arranged in a matrix. And X
The address lines in the direction and the Y direction are selected by an external selection circuit (not shown). The operation of this device configured in this way will be explained. First, it is assumed that no voltage is applied to the gates 4, 13, 14, 22, and 23. In this state, the MOS transistor 17 is turned off, and a voltage is applied to the gate 5 via the resistor 18.
Further, it is assumed that a voltage lower than that of the gate 5 is applied to the gate 6. The charge detected by the input diode 3 is transferred to the transfer gate 5 by applying a voltage to the transfer gate 4.
will be accumulated under. By removing the voltage applied to the transfer gate 4 and applying a voltage to the overflow gate 22, photocharges other than those during the accumulation time are discharged through the overflow drain 21. Next, each gate 13 of the MOS transistor 17 ,
When voltage is applied to 14, MOS transistor 17
It turns on, and the voltage applied to the transfer gate 5 is removed. When the voltage applied to the transfer gate 5 is removed, the charge under the transfer gate 5 is transferred by the transfer gate 6 to which a voltage lower than that of the gate 5 is applied, and the charge is injected into the output diode 8. The charge injected into the output diode 8 is then output to the signal line via the MOS transistor 12 . Thereafter, when a voltage is applied to the reset gate 23, the charge in the output diode 8 will be discharged through the reset drain 24. In this way, by applying a voltage to each gate 13, 14 of the MOS transistor 17 , that is, by specifying a specific X, Y using an external drive circuit, the signal of the pixel located at the specified X, Y can be read out. Become. In other words, random access becomes possible. Furthermore, by sequentially specifying X and Y, it is possible to read out an image. Note that the present invention is not limited to the embodiments described above. For example, as a means for extracting a signal from the output diode 8, a current amplifier 31 as shown in FIG. 3 may be provided in place of the MOS transistor 12 of the source follower, and the charge may be caused to flow directly from the output diode 8. Furthermore, instead of the output diode 8, a signal detection gate 32 and a transfer gate 33 may be provided as shown in FIG. 4, and changes in charge at the output section may be extracted as changes in capacitance. Moreover, instead of the input diode 14, a transparent electrode 34 is used as shown in FIG.
An MIS type light receiving section may be provided. In this case, by applying a voltage to the transparent electrode 34, Si
A potential well is created near the surface of the substrate 1, and charges generated by light incident from the transparent electrode are accumulated in this potential well. Further, as shown in FIG. 6, the input diode 3 may have a photodetector-semiconductor integrated circuit (PSID) structure in which a photoconductive element or photodiode film is deposited. In this case, by using PSID, it is possible to increase the ratio of the area of the photodetector (light receiver) to the element area. In addition, 35 in Figure 6
36 indicates a PSID lower electrode, 36 indicates an amorphous silicon photoconductive film, and 37 indicates a PSID upper electrode.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing one pixel portion of an imaging device according to an embodiment of the present invention, and FIG. 2 is a schematic cross-section taken along arrows A-A, B-B, and C-C in FIG. 2 and 3 to 6 are schematic cross-sectional views for explaining modified examples, respectively. 1... Si substrate (semiconductor substrate), 3... Input diode (light receiving section), 4, 5, 6... Transfer gate,
7...MIS structure section, 8...Output diode (output section), 12 ...MOS transistor, 17 ...Dial gate MOS transistor (switch element), 32
...Signal detection gate, 34...Transparent electrode, 36
...Amorphous asgyricon photoconductive film.

Claims (1)

[Scope of Claims] 1. Light receiving sections arranged two-dimensionally on a semiconductor substrate, and a plurality of MIS structures provided adjacent to these light receiving sections and accumulating and transferring charges in each light receiving section, A plurality of output parts are provided adjacent to each of these MIS structures and into which the charges transferred from each structure are injected, and are respectively connected to the gates of each of the MIS structures and switch the control voltage of each gate. An imaging device comprising a plurality of switch elements for switching an accumulation mode and a transfer mode of the structure, and enabling random access by selecting the switch elements. 2. The switch element is composed of a dual-gate MOS transistor, the source or drain of the transistor is connected to the gate of the MIS structure, and each gate of the transistor is connected to an X-direction address line and a Y-direction address line arranged in a matrix. The imaging device according to claim 1, wherein the imaging device is connected to each intersection of the direction address lines.