KR800000780B1 - Solid state image sensing device - Google Patents

Abstract

A device for increasing a light sensing sensitivity of short wavelength side, has a CTD(charge transfer device) with a frame transfer method and is composed of image part, accumulating part and shift register. Transfer electrodes(13) of the image part are deposited on the semiconductor surface(10) through the insulating filns. Windows(15), where intervaled between electrodes is more than 4μm, are formed on the one side of part to be a picture element.

Description

Solid State Imaging Device

1 is a block diagram of a solid state imaging device for explaining the present invention.

2 is a top view of an image portion of a conventional solid state imaging device.

3 is a cross-sectional view thereof.

4 is a cross-sectional view of another example of an image portion of a conventional apparatus.

5 is an enlarged top view of the main portion of an image portion of the solid-state imaging device according to the present invention.

6 is a cross-sectional view taken along line A-A.

7 and 8 are cross-sectional views taken along line B-B and line C-C of FIG.

9 is a manufacturing process diagram of the apparatus of the present invention.

Figure 10 is a voltage waveform diagram for explaining the operation of the apparatus of the present invention.

11 is a top view showing another example of the apparatus of the present invention.

12 is a cross-sectional view taken along line D-D thereof.

TECHNICAL FIELD The present invention relates to a solid state imaging device by a frame transfer method using a solid state imaging device, in particular, a charge transfer element (hereinafter abbreviated as CTD).

First, a solid state image pickup device using a frame transfer method will be described. The image pickup device includes an image portion 1 and an image portion 1 which obtain a charge pattern corresponding to an image pickup pattern, that is, a light reception amount, as shown in FIG. An accumulation unit 2 which accumulates the charge pattern from the image unit once, and a shift register 3 which sequentially transfers the signal from the accumulation unit 2 to the output terminal t. The image portion 1 is formed by arranging a plurality of CTDs 4, and the CTD 4 corresponding to the CTD of the image portion 1 is also arranged in the accumulation portion 2. The shift register 3 is also constituted by the CTD 4. In the image portion 1, a light receiving portion for obtaining a charge pattern in accordance with an optical image to be received is formed.

Now, an example of the configuration of the image portion 1 will be described with reference to FIGS. ₂ and 3, wherein an insulating film 6 made of SiO ₂ or the like is formed on the surface of a semiconductor gas having a low impurity concentration, for example, the silicon gas 5. ) Is formed, and the electrode 7 is deposited on the insulating film 6. The electrodes 7 are arranged with a distance of required G as a target for each CTD in common, and two electrodes 7 are connected to each other in common, so that the three-phase clocks ø ₁ , ø ₂ , ø ₃ is to be applied. Between each CTD 4, a high concentration channel stopper region 8 is formed on the surface of the semiconductor gas 5 as an object.

Then, the light receiving portion 9 is formed in the gap G between the electrodes 7 in each of the CTDs 4, and the charges corresponding to the amount of light received from the light receiving portion 9 are sequentially clocked ø ₁ , ø ₂ , ø _3. The transfer to the storage unit 2 is performed by transfer in the column direction, for example.

According to such a configuration, since the light receiving portion 9 is formed between the transfer electrodes 7, it is desired to select a large interval G for increasing the light receiving efficiency. There is a drawback that the transmission efficiency is lowered, and the light receiving efficiency and the transmission efficiency have a mutually incompatible relationship.

In addition, as another example of the CTD 4 for constructing such an image portion, as shown in FIG. 4, impurities are doped off at a high concentration on the insulating film 6 formed on the semiconductor substrate 5 so as to have a low specific resistance. The first transfer electrodes 7A made of a polycrystalline silicon layer made of (低 比 층) are arranged in a target with the required intervals, and the insulating film between these electrodes 7A and these electrodes ( 6) a second insulating film 6 'made of SiO ₂ on the entire surface is deposited, and the first electrode 7A formed by stacking the insulating films 6 and 6', for example, The first and second electrodes 7A and 7B are deposited on the second electrode 7B, for example, and electrically connected at one end thereof, respectively, so that the transfer electrodes are connected by the positive electrodes 7A and 7B, respectively. (7), every other electrode 7 is connected in common, and these two sets of electrodes (7) to take on a two-phase clock type CTD configuration by application of a clock ø _1, ø ₂ on the second to effect transfer of the electric charges between the

In such a two-phase clock type CTD, the light receiving portion 9 is formed between the electrode portions 7B of the electrodes 7.

In the case of using the CTD having such a configuration, a gap does not occur between the electrodes 7 in the charge transfer direction on the surface of the retardation 5, so that the transfer efficiency can be relatively improved. 9) polycrystalline silicon 7A is present, so that light reception is carried out through this polycrystalline silicon 7A, which causes a disadvantage that the light receiving sensitivity, in particular, the sensitivity at the short wavelength side is lowered. have.

The present invention is to provide a novel solid state imaging device which completely eliminates the above-mentioned defects in a solid state imaging device using a frame transfer method using CTD.

That is, in the present invention, in the solid state imaging device by the frame transfer method, the image part is made into a special structure.

An example of a solid-state imaging device according to the present invention, in particular an image portion, will be described in detail with reference to FIGS. 5 to 8. In the present invention, a low impurity concentration semiconductor substrate having a conductivity type of 1, for example, a silicon gas (10) is provided and arranged along the peripheral surface 10a of the channel stopper region 11 having a high impurity concentration at a predetermined interval, for example, in the column direction. On the surface 10a of the base 10, an insulating film 12 made of SiO ₂ or the like is deposited. On the insulating film 12, a first electrode portion 13A made of a transparent or opaque conductive layer such as polycrystalline silicon, or a metal such as aluminum or molybdenum is placed in the direction in which the channel stopper region 11 extends. The intervals are arranged in the object while maintaining the necessary intervals in the intersecting direction, that is, in the row direction. In addition, an insulating film 14 made of SiO ₂ is deposited between these electrode portions 13A and the surface of each electrode portion 13A, and a second electrode is formed between each of the first electrode portions 13A. The portion 13B is connected to the first electrode portion 13A and extends in the extending direction thereof so as to be deposited on both sides of the first electrode portion 13A through the insulating film 14. This second electrode portion 13B is also transparent or opaque, and the same material as that of the first electrode portion 13A can be used.

In this way, the CTDs are formed between the adjacent channel stopper regions 11 in the column direction, but in particular, between the channel stopper regions 11, i.e., a portion that becomes a picture element. Cutout portions of each of the electrode portions 13A and 13 (B) having a distance d between each of the electrode portions 13A and 13B at 4 占 퐉 or more at a position that is convenient on one axis or one side. Section 15 is formed. The cutout 15 can be formed on the channel stopper region 11 so as to extend to the center of its width.

Then, if necessary, an insulating film 17 made of SiO ₂ or the like is deposited on the entire surface by covering the electrode portion 13B, and a transparent electrode such as nesa 16 is deposited on the entire surface thereon.

The adjacent first and second electrode portions 13A and 13B are electrically connected to each other at, for example, their respective ends to form the transfer electrode 13, and every other transfer electrode ( 13) is used as a pair, and two-phase clocks ø ₁ and ø ₂ are applied between the electrodes 13 of each pair during transmission. In addition, the transparent electrode 16 is given a fixed potential equal to the ground potential.

Next, an example of the manufacturing method is explained based on FIG. 9 in order to make understanding of the structure of the solid-state imaging device by this invention mentioned above easy.

First, as shown in FIG. 9A, the semiconductor substrate 10 having the above-described channel stopper region 11 (not shown) is provided, and SiO ₂ is formed on the surface thereof, for example, by thermal oxidation to insulate the insulating film 12. ).

Next, as shown in FIG. 9B, a low resistivity silicon layer 20 in which the P-type or N-type impurities are doped off at a high concentration is formed in the polysilicon layer on the insulating film 12.

As shown in FIG. 9C, the polycrystalline silicon layer 20 is photoetched to remove the unnecessary portions, and the first electrode portion 13A is formed by this layer 20. As shown in FIG.

At this time, the notch 15 shown in FIG. 5 is simultaneously formed in the electrode portion 13A.

Next, as shown in FIG. 9D, the insulating film 14 made of SiO ₂ is formed on the entire surface by chemical vapor deposition or thermal oxidation.

Next, as shown in FIG. 9E, the polysilicon 21 in which P-type or N-type impurities are turned off at a high concentration is deposited on the insulating film 14.

As shown in Fig. 9F, the polysilicon layer 21 is subjected to photoetching to remove the unnecessary portions to form the second electrode portion 13B of the object.

Next, as in proportion to; shown in the Fig. 9g, at least it covers the electrode portion (13b) of the second to generate a SiO ₂ by thermal oxidation to shape the dielectric film.

Then, if necessary, a transparent electrode, for example, a nesa film 16, is deposited on the insulating foil 17 as shown in FIG. 9H.

Hageonde describes: the operation of the present invention configured described above, this is, the mage portion receiving section that is the section to be gained a charge pattern corresponding to an optical image that wishes to image pickup τ _1, 2 one electrode 13 of the filter is connected Article One electrode group is given a clock voltage, for example, -10V, as shown in FIG. 10A, and the other electrode group is set to 0V as shown in FIG. 10B. In this way, in the light receiving section τ ₁ , charges generated in the cutouts 15 of the electrodes 13 are diffused under each electrode 13 of the electrode group in which a potential well is formed by applying a voltage of −10 V. Accumulate here. Therefore, in the next transmission period τ ₂ , when the clock voltages ø ₁ and ø ₂ of two neighboring phases are applied, they are sequentially transmitted under the neighboring electrode 13 in one direction, and then transferred to the storage unit described in FIG. 1. Going. In this case, even when the cutout portion 15 extends over the channel stopper region 11, even this portion can be used as the light receiving portion.

According to the above-described configuration of the present invention, since the electrode 13 does not exist in the light-receiving portion, the light receiving sensitivity is not lowered or damaged by the electrode 13. In addition, in the portion other than the cutout portion 15 of each electrode 13, i.e., the portion that becomes the transfer channel, there is no gap between the electrodes 13, and therefore the transfer efficiency can be enhanced.

The relationship between the transfer efficiency of charge and the transfer channel width is not based on linear functional proportions, but the transfer efficiency decreases rapidly while the transfer channel width decreases. Since the notch 15 is conveniently provided between the channel stopper regions 11, the effective width of the transmission channel portion can be increased, and the transmission efficiency can be improved even at this advantage.

In addition, according to the configuration of the present invention, since the interval d between the electrodes 13 in the portion where the cutout portion 15 is present is selected to be 4 µm or more, the reverse flow at the time of transfer of charge through this portion is effectively It can be prevented.

In addition, in the above-mentioned example, although the case where it was set as the structure of the two-phase clock type was demonstrated, it can also be set as the structure of a three-phase clock type. An example of this case will be briefly described with reference to Figs. 11 and 12. In this example as well, on one main surface 10a of the semiconductor substrate 10 having the channel stopper region 11, it is described. An insulating film 12 such as SiO ₂ is deposited, but in this example, a high specific resistance, for example, intrinsic polycrystalline silicon layer 22 is formed on the insulating film 12 and selectively diffused thereon, for example. The electrode 13 is formed by doping off P-type or N-type impurities at a high concentration, and interposing a semi-insulating layer 23 formed as part of the intrinsic polysilicon 22 between the electrodes 13. Make it work. A part of the layer 22 is then removed by, for example, photoetching to form the cutout 15. In this case, every two electrodes 13 are electrically connected to each other, and three phase clocks? ₁ ,? ₂ ,? ₃ are applied to these three electrode groups at the time of transmission.

Even in the case of such a configuration, since the light reception is made through the notch 15 of the electrode 13, the light reception sensitivity is particularly short compared with the case where the light reception is performed through the electrode which is made of this polycrystalline silicon. The light reception sensitivity on the side can be raised. Since the semi-insulating layer 23 is interposed between the electrodes 13 in the other parts, there is no substantial gap between the electrodes 13.

Claims (1)

In the solid state image pickup device by the frame transfer method as shown in the figure and described above in the main text, one side of a portion of each pixel of a transfer electrode of an image deposited and deposited on the semiconductor surface through an insulating film. A solid state imaging device, characterized in that a cutout portion is provided in which a gap between the electrodes is 4 mu m or more.

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