JPS6043031B2 - infrared detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an infrared detection device in which an infrared detection element and a charge transfer element are combined, and to a structure of a region formed between the two elements for accumulating signal charges from the infrared detection element.

Since charge transfer devices made of silicon (Si) have almost no sensitivity to infrared rays, infrared detection devices that combine an infrared detection device made of a multi-component semiconductor and a charge transfer device made of 51 have already been developed. It is well known.

The above-mentioned infrared detection device photoelectrically converts the temperature difference in the target object to be detected, that is, the difference in the radiant energy from the target object, and converts it into electrical energy, but generally it detects the amount of background radiation other than the target object. is very large,
When the energy resulting from such background radiation is photoelectrically converted and the charge obtained by photoelectric conversion is transferred to a charge transfer device, the shape of the transfer gate electrode of the charge transfer device is changed due to the large amount of transferred charge. If the transfer gate electrode is made large in this way, it becomes difficult to process signals at high speed.

The conventional structure of a charge storage region of an infrared detection device and the structure of a charge transfer element, which emit carriers due to the amount of background radiation, are shown in FIGS. 1 and 2 as a plan view and a sectional view.

As shown in FIGS. 1 and 2, on a P-type Si substrate 1, there is an input diode 2 that inputs the charge photoelectrically converted by the infrared sensing element to the charge storage region, and the input diode and the infrared sensing element are connected. An electrode 3 is formed of S on the Si substrate.
It is formed with an i-oxide film 4 interposed therebetween.

The charge accumulation region is formed on the P-type Si substrate, and is provided with a channel stop to prevent signal charges input from one infrared detection element from mixing with signal charges input from other infrared detection elements. 5 surrounds the charge storage region.

This channel stop is formed as a highly doped diffusion layer having a P-type conductivity type by diffusing boron or the like. Further, a drain region 6 is formed in the charge storage region for discharging charges caused by the background radiation. This drain region is formed by diffusing phosphorus, etc.
It is formed as a diffusion layer having the same conductivity type. Further, an S1 oxide film is formed to insulate the various electrodes formed on each charge storage region and the drain region, and an input charge is provided on the oxide film for inputting the input charge from the infrared sensing element to the charge storage region. The gate electrode 7 and the output gate electrode 8, which transfers the accumulated charge to the charge transfer element, are made of a conductive material such as aluminum. Similarly, the reset gate electrode 9 for applying voltage when discharging charges to the drain region 6 and the storage gate electrode 10 for accumulating the signal input from the infrared sensing element are made of a conductive material such as polysilicon. It is formed by Furthermore, Si is formed on the drain region 6 and the reset gate electrode 9.
A drain bus wiring 11 and a reset gate buzz wiring 12 are formed by vapor deposition of aluminum through an oxide film. Furthermore, transfer electrodes 13, 14, 15, and 16 for transferring signals sent to the charge transfer device by the output gate electrodes to the output section of the charge transfer device are formed on the silicon substrate by vapor deposition of aluminum. It is formed through a silicon oxide film.

The operation of the charge storage region of the infrared detection device having such a structure will be explained using FIGS. 3 to 6.

First, as shown in FIG. 3, the charge 21 input to the input diode 2 applies a voltage to the input gate electrode 7 to open the gate, and at the same time applies a voltage to the storage gate electrode 10 to open the potential well. By forming this, the charge 21 is stored under the storage gate electrode 10. Next, as shown in FIG. 4, by applying a voltage to the output gate electrode 8 to open the gate, a part of the charge 22, that is, the charge due to the amount of radiation from the object, is transferred toward the charge transfer element. be transferred. The charges transferred in this way are transferred to the transfer electrodes 13, 14, 15, and 16 of the charge transfer element with φ
Transfer voltages of 2, φ3, φ4, and φ1 are sequentially applied to form potential wells under the S1 substrate to form a charge transfer element, and the potential wells are transferred in the direction of the arrow. then the fifth
Close the output gate as shown in the figure.

Furthermore, as shown in FIG. 6, a voltage is applied to the reset gate electrode 9 to open the gate and discharge charges caused by the amount of background radiation to the drain 6 as shown by the arrow. Conventionally, as shown in Fig. 1, such a charge accumulation area is one area for each input diode into which the signal charge from one infrared sensing element is input within the area defined by the channel stop.
Two drain regions 6 are formed.

As described above, this drain region is formed by diffusing phosphorus into a P-type Si substrate to form an n-type diffusion layer. The channel stop mentioned above is formed by diffusing boron into a P-type substrate to form a P-type high concentration layer, and the distance A between the drain region and the channel stop is set as shown in Figure 1 when phosphorus is diffused. 10 to 15 .mu.m is required at the minimum since it spreads in the lateral direction. Also, the width B of the drain region is at least 10 to 15 μm depending on the amount of signal to be processed.
rank is necessary. Therefore, the distance between the channel stops that defines the path of the signal charge from each infrared sensing element (
A thickness of approximately 50 μm was required for the removal +B). In the case of the above-mentioned infrared detecting device, as many infrared detecting elements as possible are coupled to the charge transfer device formed in one chip to increase the density, and to transmit as many signals as possible in one chip. It is desirable to process the amount. The present invention aims to increase the density of the above-mentioned infrared detection device, and has a plurality of infrared detection elements, and a charge storage device that introduces signal charges photoelectrically converted by each infrared detection element through an input diode. a charge transfer device for introducing signal charge from the charge storage region through an output gate, and a channel stop defining a path for signal charge from each infrared sensing element from each input diode region to the charge transfer device. In the infrared detection device provided across the corresponding bits, one drain region is provided for each two adjacent storage regions at the boundary of both charge storage regions, and
It is an object of the present invention to provide a novel infrared detection device characterized in that a loop-shaped reset gate electrode is provided to control the amount of charge released from the two charge storage regions to the drain region.

An embodiment of the present invention will be described in detail below with reference to the drawings.

FIG. 7 is a plan view of the infrared detection device according to the present invention,
FIG. 8 is a sectional view taken along YY'' in FIG. 7.

As shown in these figures, the detection device is formed on a P-type Si substrate 31, and includes input diodes 32 and 33 into which charges photoelectrically converted by an infrared detection element are input.
is formed as an n-type diffusion layer in which phosphorus is diffused into the above-mentioned P-type Si substrate. Further, an electrode 34 connecting the input diode 32 and the infrared detecting element is formed of nitrogen on the Si substrate with a Si oxide film 35 interposed therebetween. In addition, in order to prevent the signal charges input to the input diodes 32 and 33 from being mixed with each other when transferred to the storage region, the channel stop 36 is formed of a high concentration diffusion layer having a P-type conductivity by diffusing boron or the like. It is formed as. In addition, as shown in FIG. 7, a channel is formed from the center of two sides of the reset gate electrode 37, which is formed of conductive polysilicon on the Si oxide film and to which a voltage is applied when discharging charges to the drain region 38. A portion of the stop 36 is shaped so as to protrude into the vicinity of the input diodes 32, 33 and the charge transfer device. Further, in order to discharge charges caused by background radiation, a drain region 38 is formed as an n-type diffusion layer in the S1 substrate by diffusion of phosphorus so as to be common to adjacent charge storage regions.

This drain region is formed in the shape of an island at the center of the reset gate electrode 37, as shown in FIG.
That is, a loop-shaped reset gate electrode 37 is formed around the drain region 38 . Further, on the Si oxide film 35, there is an input gate electrode 39 for inputting the signal charge from the infrared sensing element to the charge storage section, and an output gate electrode 4 for transferring the input charge to the charge transfer device.
0 is formed by vapor deposition of Al.

Further, a storage gate electrode 41 for storing signal charges from the infrared sensing element is formed of conductive polysilicon on a silicon substrate with a silicon oxide film interposed therebetween. Further, on the reset gate electrode and drain region, a reset gate electrode bus wiring 42 and a drain region bus wiring 43 are formed via a Si oxide film. Further, a transfer electrode 44 for transferring signal charges sent to the charge transfer device to the output section of the charge transfer device is formed of A1 on the Si substrate via a Si oxide film. The operation of the infrared detection device having such a structure will be explained.

The signal charge photoelectrically converted by the infrared detection element is sent to the input diode 32 defined by the channel stop, and then a voltage is manually applied to the gate electrode 39 to open the gate and simultaneously apply a voltage to the storage gate electrode 41. By forming a potential well under the storage gate electrode, the potential is stored under the storage gate electrode. Further, the voltage applied to the input gate electrode 39 is returned to the original value to close the input gate.

Next, a desired voltage is applied to the output gate electrode 40 to open the gate and send out a portion of the accumulated charge, that is, the charge caused by the amount of radiation of the target object, to the charge transfer device. As shown in FIG.
Transfer voltages of 3, φ4, and φ1 are sequentially applied to form a potential well under the Si substrate forming the charge transfer device, and the potential well is transferred toward the output part of the charge transfer device. In this way, the signal charge caused by the radiation of the target object from the infrared detection element input to the input diodes 32, 33 is transferred to the charge transfer device without being mixed by the channel stop and reset gate electrodes. be done.

Next, a mechanism will be described in which, after transferring the required signal charges to the charge transfer device, the charges stored under the storage gate, mainly due to the amount of background radiation, are released to the drain region.

As shown in FIG. 9, below the storage gate 41, which is divided into two by the channel stop and reset gate regions, there is a signal charge that is mainly caused by the amount of background radiation after the desired charge is released from among the signal charges input from the infrared detection element. signal charge 5
1A and signal charge 51B are stored. 51 above
The charge A is the charge input from the input diode 33 in FIG. 7, and the charge 51B is the charge input from the input diode 32. Next, as shown in FIG. 10, a voltage is applied to the reset gate electrode 37 to open the gate and release the signal charge to the common drain region 38 as indicated by the arrow. As described above, by providing a drain region that can commonly discharge the charge caused by background radiation among the input signals from the two infrared detection elements, the degree of integration of the charge storage section of the infrared detection device is improved. . Incidentally, in the conventional charge storage section, the input diode that inputs the signal of one infrared sensing element is defined within a channel stop with a width of about 50 μm, whereas according to the present invention, the input diode that inputs the signal of one infrared sensing element is defined within a channel stop with a width of about 50 μm. The width of the input diode is approximately 35μ.
m channel stops, and the degree of integration is improved by about 1.3 times.

Further, with such a structure, the number of drain region contact holes and reset gate electrode contact holes to be formed is significantly reduced, facilitating manufacturing and improving yield.
Furthermore, by applying a small voltage to the reset gate electrode other than when discharging charges to the drain and maintaining it at a certain level, it is also possible to have a function of preventing blooming.

[Brief explanation of drawings]

1 and 2 are a plan view and a sectional view of a charge storage section of a conventional infrared detection device, and FIGS. 3 to 6 are explanatory views of the operation of the above-mentioned infrared detection device. 7 and 8 are a plan view and a sectional view of the charge storage section of the infrared detection device according to the present invention, and FIGS. 9 and 10 are
The figure is an explanatory diagram of the operation of the infrared detection device according to the present invention.
1: Silicon substrate, 2: Input diode, 3: Connection electrode, 4: Silicon oxide film, 5: Channel stop, 6:
Drain region, 7: input gate electrode, 8: output gate electrode, 9: reset gate electrode, 10: storage gate electrode,
11: Drain region bus wiring, 12: Reset gate electrode bus wiring, 13, 14, 15, 16: Transfer electrode, 21
: Accumulated charge, 22: Charge caused by radiation from the object, 31
: Silicon substrate, 32, 33: Input diode, 34:
connection electrode, 35: silicon oxide film, 36: channel stop, 37: reset gate electrode, 38: drain region, 39: input gate electrode, 40: output gate electrode, 4
1: Storage gate electrode, 42: Reset gate electrode bus wiring, 43: Drain region bus wiring, 44, 45, 46,
47: Transfer electrode, 51A, 51B: Charge caused by background radiation, A: Distance between channel stop and drain, B: Drain region width φ1, φ2, φ3, φ4: Transfer voltage.

Claims (1)

[Claims] 1 A charge storage region that has a plurality of infrared sensing elements and introduces signal charges photoelectrically converted by each infrared sensing element through an input diode, and a charge storage region that introduces signal charges from the charge storage region through an output gate. In the infrared sensing device, the infrared sensing device is provided with a charge transfer device introduced as a charge transfer device, and a channel stop is provided extending from each input diode region to a corresponding bit of the charge transfer device to define a path for signal charges from each infrared sensing device. One drain region is provided for each charge storage region at the boundary between both charge storage regions, and a loop-shaped reset gate electrode is provided to commonly control the amount of charge released from the two charge storage regions to the drain region. An infrared detection device featuring: