JP2695983B2 - Solid-state imaging device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial applications]

The present invention relates to a solid-state imaging device, and more particularly to an interline transfer CCD (charge transfer device) type solid-state imaging device.

[Prior art]

Generally, this type of interline transfer CCD type solid-state imaging device is configured as shown in FIG. A P ^- type well 22 having a low impurity concentration is provided on a surface 21a of an N-type semiconductor substrate 21. In the P ^- type well 22, a plurality of photoelectric conversion units 202 including N-type impurity regions 28 are provided at equal intervals. ing. Further, a transfer unit 201 is provided adjacent to each of the photoelectric conversion units 202 with the P ⁺ type pixel isolation region 25 interposed therebetween.
Each transfer unit 201 includes an N ^- type transfer channel 24, a gate insulating film 26.
And a gate electrode 27. Each photoelectric conversion unit 202
And a transfer unit 201 adjacent thereto constitute one column 200, respectively. Then, the photoelectric conversion units 202 in each column 200 convert the incident light into signal charges, and the generated signal charges are transferred by the transfer units 201 in the above-mentioned column 200, respectively. Conventionally, the P ^- type well 22 is in a state of peeping on the substrate surface 21a of the gap 30 between each row 200, and the gate electrode 2 of the transfer unit 201 is
7 extends over this gap 30. Each column 200 is electrically separated by the electric field at the end 27a of the gate electrode 27. 23 and 29 indicate P-type impurity layers, respectively. Two
9 can be omitted.

[Problems to be solved by the invention]

By the way, in recent solid-state imaging devices, the size of a lens used tends to be reduced from 1/2 inch to 1/3 inch, and further down to 1/4 inch.
It is desired to reduce the size of 21 (chip size). Here, reducing the size of the transfer unit 201 and the photoelectric conversion unit 202 is not preferable because performance such as the maximum signal charge amount and sensitivity is reduced. Therefore, in order to reduce the chip size without deteriorating the performance, the gap 3 between each row 200 is required.
It is necessary to make 0 narrow. However, if the gap 30 between the columns 200 is simply narrowed, a short channel effect occurs, making it difficult to control the threshold value Vth.
The separation cannot be performed with good controllability. Therefore, an object of the present invention is to provide a solid-state imaging device that can suppress the occurrence of the short channel effect even if the gap between the columns is narrowed, and can therefore reduce the chip size without lowering the performance. .

[Means for Solving the Problems]

In order to achieve the above object, the present invention provides a semiconductor substrate or a well, in which a plurality of columns each having a photoelectric conversion unit and a transfer unit arranged adjacent to each other are arranged at a predetermined distance from each other, and In a solid-state imaging device in which the gate electrode of the transfer unit is extended over a gap between the columns and the columns are electrically separated by the electric field of the gate electrode, on the entire surface of the substrate or well, The semiconductor device is characterized in that an impurity layer having a conductivity type opposite to that of the signal charges generated in the photoelectric conversion portion and a higher concentration than the substrate or the well is provided.

[Action]

When an impurity layer having a conductivity type opposite to that of the signal charge and a higher concentration than the substrate or the well is provided on the surface of the substrate or the well in the gap between the columns, the gap between the columns is unlikely to be inverted. Therefore, even if the gap between the rows is narrowed, the short channel effect is suppressed from occurring, and the rows are separated from each other with better control compared to the related art. Therefore, the chip size can be reduced without lowering the performance.

【Example】

Hereinafter, a solid-state imaging device according to the present invention will be described in detail with reference to the illustrated embodiments. As shown in FIG. 1, the solid-state imaging device, like the conventional, a low impurity concentration on the surface 11a of the N-type semiconductor substrate 11 P ^-
A mold well 12 is provided. In the P ^- type well 12, a plurality of photoelectric conversion units 102 each including an N-type impurity region 18 are provided at equal intervals. Further, a transfer unit 101 is provided adjacent to each of the photoelectric conversion units 102 with the P ⁺ type pixel isolation region 15 interposed therebetween. Each transfer unit 101 includes an N ⁻ type transfer channel 14, a gate insulating film 16, and a gate electrode 17. Each photoelectric conversion unit
102 and one adjacent transfer unit 101 each have one column 10
0 is configured. Further, the surface of the substrate 11 (which is also the surface of the P ^- type well 12) 11a including the gaps 20 between the rows 100 is provided.
P-type impurity layer with a higher impurity concentration than P ^- type well 12 on the entire surface
40 is provided shallower than the other layers. Gap 20 between each row 100
The gate electrodes 17 of the transfer units 101 in each column extend above. Reference numerals 13 and 19 denote P-type impurity layers formed below the transfer channel 14 and on the N-type impurity region 14, respectively. When there is incident light, the photoelectric conversion units 102 in each row 100 convert the incident light into signal charges, as in the related art. Then, the generated signal charges are transferred by the transfer units 201 of the column 100, respectively. The columns 100 are electrically separated from each other by the electric field at the end 17a of the gate electrode 17 extending over the gap 20 from each column. Here, since the P-type impurity layer 40 having a higher concentration than the P ⁻ -type well 12 is provided in the gap 20 between each row 100,
20 is less likely to be inverted than before. Therefore, even if the gap 20 is narrowed, the short channel effect can be suppressed from occurring, and each row 100
The separation can be performed with good controllability. Therefore, the chip size can be reduced without lowering the performance.

【The invention's effect】

As is clear from the above, the solid-state imaging device according to the present invention has a P-type or N-type on the surface of the substrate or well in the gap between each row, which includes the photoelectric conversion unit and the transfer unit and transfers signal charges.
Since the P type impurity layer is of a conductivity type opposite to that of the signal charge and has a higher impurity concentration than the substrate or the well, a short channel effect occurs even if the gap between the columns is narrowed. Can be suppressed. Therefore, the chip size can be reduced without lowering the performance.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing the configuration of a solid-state imaging device according to an embodiment of the present invention, and FIG. 2 is a cross-sectional view showing the configuration of a conventional interline transfer CCD type solid-state imaging device. 11 ... N-type semiconductor substrate, 12 ... P ^- type well, 13,19 ...
P-type impurity layer, 14 ...... N ^- -type transfer channel, 15 ...... P ⁺ -type element isolation region, 16 ...... gate insulating film, 17 ...... gate electrode,
18 N-type impurity regions, 20 gaps, 40 P-type impurity layers, 100 columns, 101 transfer units, 102 photoelectric conversion units.

Claims (1)

(57) [Claims] 1. A plurality of rows each having a photoelectric conversion unit and a transfer unit arranged adjacent to each other and separated by a predetermined distance on the surface of a semiconductor substrate or a well, and the transfer unit is disposed in a gap between the rows. In the solid-state imaging device in which the gate electrodes of the portions are extended to electrically separate the columns by the electric field of the gate electrodes, the photoelectric conversion portions are generated on the entire surface of the substrate or the well. A solid-state imaging device, which is provided with an impurity layer having a conductivity type opposite to that of signal charges and a higher concentration than the substrate or the well.