JPS6034275B2 - charge transfer device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Technical field of the invention 'a' The present invention relates to a parallel serial out type
The present invention relates to an infrared detection type charge transfer device (abbreviated as SO), and particularly relates to an improvement in the structure of its charge input section.

{b' Background of the technology In recent years, as the application of infrared rays has become popular, CCDs have been used as multiplexers for multi-element infrared sensing elements (hereinafter referred to as photodetecting elements), but recently PISO There is a growing demand for uniformity of the amount of charge flowing into the input section of an infrared detection type charge transfer device, particularly at the input gate section.

[c - Prior art and problems At present, high-sensitivity light-receiving elements used as photoelectric conversion elements include, for example, indium antimony (lnSb), daily tin tellurium (PnTe), mercury cadmium tellurium (H
The signal processing section, which mainly consists of a CCD as a multiplexer, is made of silicon (Si).
) is used as a substrate, a so-called hybrid method is being explored.

FIG. 1 is a plan view of main parts showing the structure of a conventional infrared detection type charge transfer device, in which the left side of the chain line O is a light receiving section, and the right side is a signal processing section.

In this figure, D represents a photodetector, ID represents an input diode, and i and i+1 represent the i-th and i+
This is a subtitle indicating the first. Further, 1 is a strip-shaped input gate, 2 is an accumulation gate, and 3 is a strip-shaped transfer gate, which are successively arranged adjacent to the input diode and constitute a charge input section. A CCD having a transfer electrode 4 is arranged adjacent to this charge input section. Light receiving element D
The charges generated by photoelectric conversion at i and Di+1 flow in the direction of arrow A and flow into input diodes mf and IDi, respectively, passing directly under input gate 1 and reaching the potential created in advance immediately below storage gate 2. (hereinafter simply referred to as wells).

Among these accumulated charges, upward charges based on the observation object flow in the direction of the arrow through the transfer gate 3 and flow into the well directly below the transfer electrode 4 of the CCD, and the remaining downward charges due to the background are discharged. It is designed to be discharged from a drain (not shown).

The charges introduced in parallel from each charge input section directly below the transfer electrode 4 of the CCD are then transferred, for example, in the two directions of the arrows, and read out as time-series signals from output diodes (not shown).

Once all of these charges have been read out, the same sequence is repeated again. By the way, in conventional infrared detection type charge transfer devices, the input gate is made of sufficiently low resistance, and a voltage is applied from one end of the input gate to cause charges to flow from all input diodes into the well directly below the storage gate 2. was the usual method. However, this input gate 1 forms a so-called MIS structure with an insulator and a semiconductor substrate directly below it, and this MIS
At present, the so-called effective threshold voltage VT exhibited by the structure is not necessarily constant depending on the location, and has some degree of variation in waves. In addition, since the light-receiving elements in the light-receiving section also have variations in their photoelectric conversion characteristics, the variation in the light-receiving elements arranged in an array and the interference exhibited by the input gate 1,
If the variation in value voltage and the variation in value voltage are totaled, the result will be observed as variation in the amount of charge inflow as expressed by a polygonal line approximation along the longitudinal direction of the input gate 1.

For this reason, variations occur in the amount of charge flowing directly under the storage gate 2 and therefore directly under the transfer electrode of the CCD.
When a video signal captured by such a charge transfer device is reproduced, the image quality is poor.
'd' Purpose of the Invention The present invention has been made in view of the above-mentioned drawbacks of the conventional art.The present invention has been made by modifying the configuration of the charge input section so that the amount of charge flowing from the input diode is uniform in all parts of the input gate. The purpose is to provide a charge transfer device.

'e} Structure of the Invention According to the present invention, the object is to provide an input diode that introduces charges generated by photoelectric conversion in a light receiving element, and a strip-shaped input gate and an accumulation gate that are sequentially arranged adjacent to the input diode. In the configuration including a charge input section mainly consisting of a charge input section and a charge transfer section adjacent thereto that outputs charges transferred from the charge input section as a time-series signal, the strip-shaped input gate is made of a high-resistance material. This is achieved by forming a voltage applying electrode for adjusting the potential of each part of the input gate at a distance corresponding to a predetermined number of stages of the charge transfer part on the input gate.

'f} Embodiments of the Invention Hereinafter, embodiments of the charge transfer device according to the present invention will be described in detail with reference to the drawings.

FIG. 2 is a configuration diagram (plan view) showing an embodiment of the charge transfer device according to the present invention, particularly focusing on the charge input section,
Components equivalent to those in FIG. 1 are designated by the same reference numerals.

The difference between the present invention and the conventional one shown in FIG. 1 is that the input gate 1 is formed of a material with high and low resistance so that the potential in the longitudinal direction has a gradient, and the number of CCD stages is, for example, 5 or 10. This is because a voltage applying electrode W is provided to this input gate for each stage.

Incidentally, each of the voltage application electrodes W is provided with a voltage application lead-out terminal 10, and each has a slightly different correction voltage V. is applied. The reason for taking this measure is that, as mentioned above, the input gate, the insulating film underneath it, and the semiconductor substrate directly below it constitute a strip-shaped MIS structure in the longitudinal direction. This is because the so-called threshold voltage VT in the portion is not constant, but changes in a gentle wave in the longitudinal direction.

For this reason, as mentioned above, variations occur in the amount of charge flowing in, but the voltage applied to each extraction terminal 101 is
If expressed as G, the above problem, including variations in the light receiving elements, can be solved by making the amount of IVG-VTI substantially the same at each part of the input gate.

Therefore, now, the value of the correction voltage Vo is changed little by little so that the value of IVG-VTI is constant in each part, and one voltage is applied to each terminal. In this way, the effective threshold voltage, which is changing in a wavy manner as described above, is corrected, and the input characteristics are corrected along the longitudinal direction of the input gate, so to speak, using a polygonal line approximation. The amount of charge supplied from the light receiving section to the signal processing section is approximately equalized, the device characteristics are greatly improved, and the quality of the reproduced image is therefore significantly improved. (g) Effects of the Invention As explained in detail above, in the charge transfer device of the present invention, in the structure of the charge input section, the substantial IVc/VTI values directly under each portion of the input gate are approximately equalized. As a result, a remarkable improvement effect on device characteristics is observed, and great practical effects can be expected.

[Brief explanation of the drawing]

Figure 1 is a plan view of the main part showing the structure of the secondary charge transfer device;
FIG. 2 is a plan view of essential parts showing an embodiment of the charge transfer device according to the present invention. D...Photodetector, ID...Input diode, 1...
...Input gate, 2...Storage gate, 3.
...Transfer gate, 4...Transfer electrode. Figure 1 Figure 2

Claims (1)

[Claims] 1. A plurality of input diodes that introduce charges generated by photoelectric conversion in a light-receiving element, a charge input section mainly consisting of a band-shaped input gate and an accumulation gate sequentially arranged adjacent to the input diodes, and In the configuration including a charge transfer section adjacent to the input section and outputting the charges transferred from the charge input section as a time-series signal, the strip-shaped input gate is formed of a high-resistance material, and the input gate is made of a high-resistance material. In the charge transfer device, voltage application electrodes for voltage adjustment of each part of the input gate are provided at distances for each predetermined number of stages of the charge transfer part.