JPS6118345B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to charge transfer imaging devices, and more particularly to charge transfer one-dimensional photosensitive devices.

A conventional device of this type has been proposed in which a photosensitive section and a charge transfer section for transferring signal charges are separated, and in particular, a one-dimensional charge transfer array is arranged above and below the one-dimensional photosensitive section array. However, in such conventional devices, if the number of picture elements in the photosensitive area is increased to a higher density, the drive frequency will inevitably increase, requiring a drive frequency of several megahertz for practical integration, and the transfer efficiency will decrease significantly. Therefore, high-density integration was difficult. As a result, the resolution was poor, making it impractical.

SUMMARY OF THE INVENTION An object of the present invention is to provide a charge transfer one-dimensional photosensitive device that eliminates such drawbacks.

According to the present invention, in a charge transfer device in which a large number of electrodes are provided on a semiconductor substrate via an insulator to constitute a photosensitive array section and a transfer array section, four transfer elements are provided for one photosensitive element. With the photosensitive element as the center, the transfer elements are arranged separately, two above and below, and a large number of each are arranged one-dimensionally to constitute one photosensitive array section and four transfer array sections, and each adjacent array a charge transfer one-dimensional photosensitive array section separated by a control electrode; a means for transferring and accumulating charges accumulated in the photosensitive array section to the transfer array section according to light intensity; and a means for transferring and accumulating charges in the transfer array section; A charge transfer one-dimensional photosensitive device characterized by comprising means for sequentially transferring the transferred charges along the transfer array section, means for reading the transferred charges, and means for taking out the read charges. can get. According to the present invention, high-density integration can be achieved while maintaining high transfer efficiency, and driving can be performed at a low frequency, so that the resolution of an imaging device can be significantly improved.

Next, the present invention will be explained using the drawings.

FIG. 1 is a plan view of a charge transfer one-dimensional photosensitive device showing an embodiment of the present invention, and FIGS. 2 and 3 are cross-sectional views taken along lines A'-B' and C'-D' in FIG. FIG. 3 is a diagram for explaining the operation.

In FIG. 1, the one-dimensional charge transfer photosensitive array section of the present invention (1) integrates signal charges generated by incident light into the charge medium 10 directly under the electrodes during the period when a pulse voltage is applied to the electrodes 12; One-dimensional photosensitive array section
S ₁ , S ₂ ...Sn, (2) control electrode sections 18, 18' for controlling the transfer of charges accumulated in the photosensitive array to transfer array regions 16, 16', 17, 17'; (3) control electrode sections 18, 18'; 1 transfer array section 16, 16' (4) second transfer array section 17, 17' (5) controls charge transfer and charge mixing between the first transfer array section and the second transfer array section Control electrode sections 19, 19' (6) means 20 for sequentially reading out the signal charges transferred from each continuous array; (7) means 21 for taking out the read charges; are the respective transfer electrodes 12a-n, 13a-n, 14 constituting the first transfer array section and the second transfer array section.
a~n, 15a~n, 12'a~n', 13a'~
n', 14a' to n', and 15a' to n' along the transfer array section. Next, a specific example of the operation of the present invention will be explained in detail using FIGS. 2 and 3.

For example, an n-type silicon substrate 1 is used as a charge storage medium.
0, a dielectric layer such as silicon dioxide 11 is coated on the surface of the substrate, and a photosensitive electrode 12, a transfer gate electrode 18, and a transfer electrode are formed on the silicon dioxide.
A ₂ and A ₄ (represented by lines A ₂ and A ₄ in FIGS. 2 and 3) transfer array separation control electrodes 19 are arranged, respectively. The solid line 22 and broken line ₂₃ shown in the substrate 10 in FIG. The closer it is, the higher the rank. Here, the structure is such that the first transfer array section 16 and the second transfer section 17 have different surface potentials directly under the transfer electrode _A2 . The reason for this will be explained later, but in order to make the surface potentials different under the same electrode, for example, there are known methods such as changing the thickness of the dielectric layer 11, or adding charges in the dielectric layer 11. This can be achieved by localizing the impurity, changing the impurity concentration in the substrate, or changing the concentration in the channel region using a charge-coupled device called a buried channel.

In Figure 2-a, when a pulse is applied to the photosensitive electrode 12, a potential well (solid line 2) appears in the substrate directly under the electrode.
2) is formed, and when light is irradiated, electron-hole pairs are generated, and the holes, which are minority charges, are accumulated in the potential well. Since a transfer pulse is always applied to the transfer electrode group during the period when information charges are accumulated in the photosensitive array, transfer control electrodes 18, It is controlled by a pulse voltage of the array separation control electrode 19. Although not shown in the figure, it is desirable that the surface on the light incident side, except for the photosensitive portion, be shielded from light.

In order to transfer information charges from the photosensitive section to the transfer section, the information charges are accumulated in the photosensitive array as shown in Figure 2- _b by applying overlapping pulses to each electrode in the order of electrodes 12 → 18 → 19 → A2. The information charges can then be transferred to the second transfer array section 17.

After transferring the information charges from the photosensitive section to the second transfer array section, the transfer gate 18 and the array separation control electrode 1
When the photosensitive array section and the transfer array section are separated by removing the applied pulse 9 and a pulse is applied to the photosensitive electrode again, the photosensitive section starts accumulating information charges again as shown in Fig. 2-c, and the charges in the second transfer array section are is sent to the readout section by applying a transfer pulse to the electrode group of the transfer array section. Figure 3 shows c'-- in Figure 1.
This is a diagram for explaining using the cross section of D', and information charges are accumulated in the potential well directly below the photosensitive area using the same procedure as explained in Fig. 2 (Figure 3-a). Electrode 1 for transfer to transfer section
When pulses are applied in the order of 2→18→19→ _A4 , the array separation control electrode 19 is
Since there is a channel separation zone 24 formed in the substrate immediately below by using means such as N ⁺ diffusion, the surface potential of this region is high regardless of the voltage of the control electrode 19. From this, it can be seen that the information charge from the photosensitive section is the third-b
The data is transferred to the first transfer array unit 16 as shown in the figure. After the information charges are transferred to the first transfer array section 16, as explained in FIG. As shown in Figure 1-c, the photosensitive section starts accumulating information charges, and the charges transferred to the first transfer array section are transferred to the reading means.

The operation immediately below the individual electrodes has been described in detail above, and the overall operation of the embodiment of the present invention shown in FIG. 1 will be further described.

Electrode groups 12a-n, 13a-n, 14a-n,
15a-n, 12a'-n', 13a'-n', 14a'-
n', 15a'-n' are lines A ₁ every 4 electrodes, respectively.
(12a, 12b, 12c, ......12n) Track
A ₂ (13a.13b,...13n, track A ₃ (14
a, 14b, ... 14n), track A ₄ (15a, 1
5b……15n) Similarly, the line A ₁ ′ (12a′,
......12n') Line A ₂ '(13a'...13n')
Line A ₃ ′ (14′...14n′) Line A ₄ ′15a′,
......15n'), forming a four-phase drive charge-coupled device. Here track A ₁ and
A ₁ ′, A ₂ and A ₂ ′, A ₃ and A ₃ ′, and A ₄ and A ₄ ′ apply the same pulse and are connected inside or outside the integrated device. In addition, transfer control electrodes 18 and 1
The 8' array separation control electrodes 19 and 19' also apply the same pulse and are connected in the same manner as described above. (Hereinafter, it is assumed that the above-mentioned connections are made when applying pulses to each line and electrode.) Furthermore, in the present invention, since the transfer section is vertically symmetrical with respect to the photosensitive array section, it is convenient for the following explanation. Regarding the transfer array section provided above the upper photosensitive array section, the transfer array section provided below the upper transfer array is expressed as a lower transfer array section.

Now, by applying a pulse to the photosensitive part electrode 12, a potential well is formed in the substrate of each photosensitive part (S ₁ , S ₂ , S ₃ . . . Sn) separated by the channel separation band 24, and each Minority charges generated by the amount of light irradiated onto the photosensitive area of the sensor are accumulated. After a certain period of time, the photosensitive part electrode 12 is used to transfer the accumulated information charge from the photosensitive part to each transfer array part.
Transfer control electrode 18 transfer line
When pulses are sequentially applied to the A ₂ and A ₄ transfer array separation control electrodes 19 so that the pulses overlap, the photosensitive area S ₁ is The information charge is transferred to the upper second transfer section 17' directly below the electrode 15a', and the information charge of the photosensitive section _S2 is transferred to the upper first transfer section 16' immediately below the electrode 13a'.
S' ₃ is sent to the lower first transfer section 16 directly below 15a, and S ₄ is sent to the lower second transfer section 17 directly below 13a. Information charges in the photosensitive array section are transferred every third to the transfer sections in four columns. be transferred. Here, the order of transfer from the photosensitive section to the transfer section is determined by the reading means, and the above case is one method. After the information charges in each photosensitive section are transferred to each transfer section, the pulses on the transfer control electrode 18 and the array separation control electrode 19 are removed, and each transfer section and photosensitive section are separated. For the charges transferred to each transfer section, pulses are first applied in the order of line A ₃ on → A ₂ off → A ₃ off, and the charges directly under lines A ₂ and A′ ₂ are transferred to only two electrodes in the transfer direction. The information charges are transferred under the common electrode of the first and second transfer sections, and pulses are applied in the order of lines A ₁ →A ₂ →A ₃ →A ₄ according to the concept of a four-phase drive charge-coupled device. As a result, the information charges transferred to the four columns of transfer sections are transferred in parallel to the reading means. . 4
The charges transferred in parallel in the column transfer arrays are read out using a readout array, such as 20, consisting of a four-phase drive charge coupling device similar to the transfer array section.
The signals are sequentially guided to the signal reading means 21.

The driving frequency of such a transfer array section may be 1/2 of the video frequency.

Although the present invention has been described above with reference to a four-phase drive embodiment, it can also be applied to, for example, a two-phase drive charge transfer device. By changing the structure, it can be applied to single-phase and three-phase drive charge transfer devices. Further, the structure of the present invention can also be realized by a surface channel, and can be realized by combining any means as long as they have the functions in each area of the present invention.

[Brief explanation of the drawing]

FIG. 1 is a plan view of an embodiment of the charge transfer one-dimensional photosensitive array of the present invention, and FIG.
Figure 3 is a diagram for explaining the operation using a sectional view taken along A'-B', and Figure 3 is a diagram used to explain the operation using a sectional view taken along C'-D' in Figure 1. be. 10 is a semiconductor substrate, 11 is an insulating film, 12 is a photosensitive electrode, 12a-n, 13a-n, 14a-n, 1
5a-n12a'-n', 13a'-n'14a'-n'15
a'-n' are transfer electrodes, 16, 16 are first transfer parts, 1
7 and 17 are second transfer parts, 18 and 18 are transfer control electrodes, 19 are transfer array separation control electrodes, 2
0 is a readout charge transfer means, 21 is a charge extraction means, and 22 and 23 are surface potential curves. _S1 , _S2 ...
...Sn indicates a photosensitive portion, and 24 indicates a channel separation region.

Claims (1)

[Claims] 1. In a charge transfer device in which a large number of electrodes are provided on a semiconductor substrate via an insulator to constitute a photosensitive array section and a transfer array section, four photosensitive elements are provided for one photosensitive element. The transfer elements are arranged separately, two above and below the photosensitive element, and a large number of each is arranged one-dimensionally to form one photosensitive array section and four transfer array sections, and there is a gap between each adjacent array section. A charge transfer one-dimensional photosensitive array separated by a control electrode; a means for transferring and accumulating charges accumulated in the photosensitive array section in accordance with light intensity to the transfer array section; A charge transfer one-dimensional photosensitive device comprising means for sequentially transferring the charges along the transfer array section, means for reading out the transferred charges, and means for taking out the read charges.