JP3518212B2 - Solid-state imaging device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid-state image pickup device, and more particularly to a CCD solid-state image pickup device.

[0002]

9 and 10 show an example of the configuration of a conventional CCD solid-state image pickup device, particularly a unit cell portion. Conventional C
As shown in FIG. 9, the CD solid-state image pickup device 1 includes a plurality of sensor units 2 arranged in a matrix, and a vertical transfer register 3 having a CCD structure provided on one side of each sensor unit row. The transfer electrode 4 of the vertical transfer register 3 is connected to each sensor unit 2
The first electrode 5 and the second
So that the second electrode 6 made of polysilicon layer corresponds to
The first electrode 5 and the second electrode 6 are repeatedly arranged in the vertical direction. Further, the first electrode 5 and the second electrode 6 are commonly formed in each vertical transfer register 3 so as to pass between the sensor units 2 which are vertically adjacent to each other.

A read gate portion 7 having a gate electrode, for example, the second electrode 6, is provided between the sensor portion 2 and the vertical transfer register 3 corresponding thereto, that is, for reading signal charges from the sensor portion 2 to the vertical transfer register 3. A read gate portion is formed. Further, a channel stop region 8 is formed between the vertical transfer registers 3 on the opposite side of the sensor unit 2.

FIG. 10 shows a semiconductor structure in a cross section taken along the line AA of FIG. In this semiconductor structure, a first well region 12 of a second conductivity type, for example, p type is formed on a silicon substrate 11 of a first conductivity type, for example, n type, and a sensor section 2 and a sensor section 2 are formed in the first p type well region 12. An n-type transfer region 13 forming the vertical transfer register 3 and a p-type channel stop region 8 are formed respectively. The sensor portion 2 has a high-concentration p-type well region 12, an n-type impurity region 15 formed therein, a charge storage layer formed on the surface of the n-type impurity region 15, and a hole storage layer in this example. The p-type impurity region 16 constitutes a so-called hole-accumulated sensor. In the read gate section 7, p ⁻ region 1
7 is formed. A second p-type well region 18 is formed below the n-type transfer region 13.

Then, the gate insulating film 19 is formed over the n-type transfer region 13 and the p ⁻ region 17 of the read gate portion 7.
A transfer electrode 4 made of polysilicon is formed through the interlayer insulating film 20, and an interlayer insulating film 20 is formed on the entire surface including the transfer electrode 4, and an entire surface except the opening 22 corresponding to the position directly above the sensor unit 2 is formed on the transfer electrode 4. A light-shielding film 21 made of, for example, Al is formed on the surface.

In this CCD solid-state imaging device 1, when a voltage is applied to the second electrode 6 of the transfer electrode 4, the signal charge photoelectrically converted and accumulated in the sensor section 2 is read out as shown by an arrow a in FIG. It is read out to the vertical transfer register 3 through the unit 7. Further, the transferred signal charges are transferred in the vertical direction in the vertical transfer register 3 by driving the transfer electrodes 4.

[0007]

By the way, the conventional CC
In the D solid-state image sensor 1, the opening 22 of the light shielding film 21 is formed.
Of the transfer electrode 4 of the light-shielding film 21 in order to reduce the occurrence of smear when light enters from the edge of the light-shielding film and is multiply reflected between the light-shielding film 21 and the silicon substrate and enters the vertical transfer register 3.
A measure is taken to lengthen the portion from the end position on the sensor unit 2 side to the opening 22 (hereinafter referred to as an overhang).

However, in the CCD solid-state image pickup device 1 described above, the width of the sensor portion 2 is the interval between the transfer electrodes 4 sandwiching the sensor portion. Or blooming is worse, it is difficult to reduce the width of the read gate portion 7,
In addition, the device characteristics were deteriorated and smear was deteriorated.
Therefore, it is difficult to form the opening 22 of the light-shielding film 21, and the miniaturization of the unit cell size has reached a ceiling of about 5 μm square.

In view of the above points, the present invention provides a solid-state image sensor capable of miniaturizing a unit cell and capable of frame reading and field reading.

[0010]

A solid-state image pickup device according to the present invention is constructed so that signal charges are read from each sensor unit to a vertical transfer register through a sensor unit on one side.

According to this structure, the conventional read gate portion is omitted, and the unit cell size can be miniaturized accordingly. In addition, because the read gate section is omitted,
Since the light-shielding film is directed toward the sensor unit side, smear can be reduced. Between vertical sensor parts
At the sensor section next to the read gate section in the vertical direction
The distance between the region under the second electrode and the charge storage layer
Signal charge becomes the total distance from the protrusion to the protrusion.
Leakage of charge to the adjacent sensor part in the vertical direction when reading
However, it can be blocked more reliably. Furthermore, since the signal charges are read out between the sensor units on one side, both frame reading and field reading are possible.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION A solid-state image sensor according to the present invention comprises a plurality of sensor sections and a vertical transfer register corresponding to each sensor section row, and a transfer electrode of the vertical transfer register is opposed to each sensor section. The first electrode and the second electrode are formed by repeating the electrode and the second electrode, and are continuously formed between the sensor units that are vertically adjacent to each other.
2 vertically in the vertical direction so that the
Each sensor part is formed to divide the charge accumulation on the surface.
Read gate between the sensor sections on each side having layers
Charge is accumulated for the required distance along the entire circumference of other parts except the part that contacts the part
It is formed inward of the layer, and the signal of each sensor unit is read out under the first electrode between the sensor units on one side.

According to the present invention, in the above solid-state imaging device, the sensor section is separated from the vertical transfer register by a predetermined distance (so-called offset), and the channel is formed under the first electrode except at least the read gate section between the sensor sections on one side. The structure is such that a stop region is formed.

According to the present invention, in the above solid-state image pickup device, a channel stop region is formed under the first electrode and under the second electrode except for the reading section between the sensor sections on one side.

According to the present invention, in the above solid-state image pickup device, the charge storage layer of the sensor section having a charge storage layer on the surface thereof also serves as a channel stop region between the sensor section and the vertical transfer register.

According to the present invention, in the above solid-state image pickup device, an edge of one side of the sensor section between the sensor sections is separated from the first electrode except the read gate section, and the read gate section of the sensor section is excluded. A charge storage layer on the surface of the sensor portion that also serves as a channel stop region is formed around the portion.

Embodiments of the present invention will be described below with reference to the drawings.

FIGS. 1 to 3 show an embodiment of a CCD solid-state image pickup device according to the present invention, and particularly show only a 2-unit cell portion thereof. CCD solid-state image sensor 31 of the present embodiment
As shown in FIG. 1, a plurality of sensor units 32 are arranged in a matrix, and a vertical transfer register 33 having a CCD structure is provided on one side of each sensor unit row. The transfer electrodes 34 of the vertical transfer registers 33 are the first electrodes such that the first electrode 35 made of the first-layer polysilicon and the second electrode 36 made of the second-layer polysilicon correspond to each sensor section 32, for example. 35 and the second electrode 36 are repeatedly arranged in the vertical direction. The first electrode 35 and the second electrode 36 are formed in common in each vertical transfer register 33 by passing between the sensor units 32 that are vertically adjacent to each other. At this time, between the sensor portions 32, the first electrode 35 and the second electrode 36 are formed in an upper half and a lower half so as to bisect each in the vertical direction.

In each sensor section 32, a part of the upper end in the vertical direction, that is, the upper end of the left half in FIG. 1 closer to the vertical transfer register 35 on the side where the signal charge is read is the first section between the sensor sections 32. The other periphery, that is, the right half of the upper end, both side ends facing the vertical transfer register 37, and the lower end while being adjacent to the electrode 35 is a predetermined distance d from the transfer electrode 34.
It is formed by being offset by ₁ and d ₂ .

Further, in this example, a portion 38 serving as a read gate portion of the first electrode 35 is provided between the sensor portions 32.
In FIG. 1 except for FIG. 1, a diagonally shaded channel stop region 39 is formed in the right half portion and below the second electrode 36. still,
The channel stop region 39 below the second electrode 36 can be omitted.

FIG. 2 shows a semiconductor structure taken along the line BB of FIG. 1, and FIG. 3 shows a semiconductor structure taken along the line CC of FIG. This semiconductor structure has a first conductivity type, for example, n-type silicon semiconductor substrate 41, and a second conductivity type, for example, p-type first well region 42.
Are formed, and an n-type transfer region 43 forming the vertical transfer register 33 is formed in the first p-type well region 42. A second p-type well region 44 is formed immediately below the n-type transfer region 43. A transfer electrode 34 including a first electrode 35 and a second electrode 36 made of polysilicon is formed on the n-type transfer region 43 via a gate insulating film 47.

Further, a charge storage layer forming the surface of the sensor portion 32 is formed by self-alignment by ion implantation using the transfer electrode 34 as a mask, and in this example, a high-concentration p-type impurity region 45 serving as a hole storage layer is formed. To be done. Furthermore, the first
The p-type well region 42, the distance d ₁ from the transfer electrodes 34
And d ₂ are offset by ion implantation through a photoresist mask so that the n-type impurity region 46 is formed at a position corresponding to the p-type impurity region, that is, below the hole accumulation layer 45.
The first p-type well region 42, the n-type impurity region 46, and the hole accumulation layer 45 form the sensor portion 32, which is a so-called hole-accumulated sensor.

Further, in the first p-type well region 42, a p-type channel stop region 39 is formed in a region extending from a part of the first electrode 35 between the adjacent sensor portions 32 in the vertical direction to the second electrode 36. To be done. Further, a low concentration P-type region 40 is formed in the region forming the read gate portion.

Then, an interlayer insulating film 48 is formed on the entire surface including the transfer electrode 34, and further, for example, Al is formed on the entire surface except the opening 49 corresponding to the upper position of the sensor section 32.
The light shielding film 50 is formed by the above.

Between the sensor section 32 and the transfer electrode 34, an area offset by the distances d ₁ and d ₂ (that is, a separated area between the sensor section 32 and the transfer electrode 34).
The hole accumulating layer 45 on the surface of the sensor portion 32 extending in the area also serves as a channel stop region.

The vertical transfer register 33 is driven by a four-phase drive pulse in this example. The signal charges read out to the vertical transfer register 33 are transferred in the vertical direction in the vertical transfer register 33 by driving the transfer electrodes 34.

According to the CCD solid-state image sensor 31 having such a configuration, by applying a high level voltage to the first electrode 35 of the transfer electrode 34, the signal charge photoelectrically converted and accumulated in the sensor section 32 is As indicated by an arrow b in FIG. 1, the data is read out to the corresponding one of the vertical transfer registers 33 through the read gate portion 38 formed by the first electrode 35 between the one or upper sensor portions 32. At this time, since the channel stop region 39 is provided under the right half portion of the first electrode 35 between the upper sensor units 32, the signal charges of the sensor unit 32 are read out to the vertical transfer register 33 on the opposite side. Never be

Further, since there is an area offset by the distance d ₁ between the vertical transfer registers 33 on both sides of the sensor section 32, the signal charge does not leak between them.

Further, since the channel stop region 39 is formed under the second electrode 36 between the sensor portions 32 which are vertically adjacent to each other, the signal between the sensor portions 32 which are vertically adjacent to each other can be more reliably provided. No charge leakage occurs. That is,
Each sensor section 32 is certainly separated from the other section and is in an independent state. Therefore, the read gate section provided between the conventional sensor section and the vertical transfer register is omitted, and the unit cell size can be miniaturized accordingly. At the same time, a sufficient protrusion length of the light shielding film 50 can be obtained,
Smear can be reduced.

When the positional relationship between the opening of the sensor section 32 and the vertical transfer register 33 is the same as in the conventional example,
Since the conventional read gate portion is omitted, the light shielding film 5 is provided.
The length of protrusion of 0 to the sensor unit side can be increased, and smear can be further reduced. On the contrary, since the opening of the sensor unit 32 can be widened by omitting the conventional read gate unit, the sensitivity can be improved.

Since the signal charge of each sensor section 32 is independently read out through the read gate section 38 by the first electrode 35 between the one sensor section 32, both the frame read operation and the field read operation are possible.

That is, in the frame reading operation, after the signal charges (first field) of the sensor units on the odd lines are read, the signal charges (second field) of the sensor units on the even lines are read next. In the field read operation, the signal charges of each sensor unit are once read to the vertical transfer register 33, and then the signal charges of two vertically adjacent pixels in the vertical transfer register 33 are mixed to form a first field. The signal charges of the respective sensor units are read out again and read to the vertical transfer register 33 again, and the signal charges of the other two pixels adjacent in the vertical direction in the vertical transfer register are mixed and read out as the second field.

4 to 6 show another embodiment of the solid-state image pickup device according to the present invention. The solid-state imaging device 52 of this example has a configuration similar to that of FIG. 1 except that the channel stop region 39 is omitted in the configuration of FIG. 1 described above. Portions corresponding to those in FIG. 1 are designated by the same reference numerals and duplicate description will be omitted.

That is, the sensor part 32 has a rectangular shape in which the left half of the upper end projects, and the protruding left half of the upper end is adjacent to the first electrode 35 between the sensor parts 32, and the other edge, that is, the upper part. The right half of the end, both side ends facing the vertical transfer register 33, and the lower end are offset from the transfer electrode 34 by predetermined distances d ₁ and d ₂ . Then, as shown by the diagonal lines in FIG. 4, the hole accumulation layer 45 of the extended sensor portion 32 is also used as the channel stop region in the offset region.

According to this structure, the sensor section 32 is separated from the entire circumference of the sensor section 32 except the read gate section 38 by the hole accumulation layer 45 which also serves as an offset region and a channel stop region. Therefore, the first of the transfer electrodes 34
By applying a high level voltage to the electrode 35, the signal charges photoelectrically converted and accumulated in the sensor unit 32 are stored in one of the upper sensor units 3 as shown by an arrow b in FIG.
Read gate portion 38 formed by the first electrode 35 between the two
Through the corresponding vertical transfer register 33.

At this time, looking at the potential on the line FF along the first electrode between the sensor portions 32, the narrow channel is formed in the right half region because it is sandwiched by the hole accumulation layers 45 which also serve as channel stop regions. As a result, as shown in FIG. 7, the potential 54 is raised, and a potential gradient is generated such that the potential becomes deeper from the vertical transfer register 33 on the right side to the vertical transfer register 35 on the left side from which charges should be read. As a result, the sensor unit 32
The signal charge from the vertical transfer register 3 on the opposite side (right side)
No data will be erroneously read.

Therefore, also in the configuration of FIG. 4, the same effect as in the case of FIG. 1 can be obtained. At the same time, since the separately provided channel stop region 39 is omitted, the structure can be simplified and the manufacturing process can be reduced accordingly.

In the example of FIG. 4, the upper end of the sensor portion 32 is formed in a stepped shape. However, as shown in FIG. 8, the upper end of the sensor portion 32 is oblique from the portion in contact with the read gate portion 38. The shape may be slanted so as to recede, and in this case also, the same effect as in FIG. 4 is obtained.

[0039]

According to the solid-state image pickup device of the present invention, the read gate section between the sensor section and the vertical transfer register is omitted, and the signal charge from the sensor section is read out to the vertical transfer register through the sensor section. The unit cell size can be further reduced. The smear can be further reduced when the length of the light-shielding film protruding toward the sensor portion is increased by the amount of the readout gate portion omitted. On the contrary, the omitted part of the read gate portion,
The sensitivity can be further improved when the opening of the sensor unit is widened.

Signal charge from the sensor section to the vertical transfer register
When reading, read between adjacent sensor units in the vertical direction.
The distance between the output gate unit and the sensor unit that is vertically adjacent to
2 Total distance between the area under the electrode and the overhang of the charge storage layer
Therefore, the leakage of electric charge to the vertically adjacent sensor section
Can be prevented more reliably. Then, since the signal charge of each sensor unit is independently read out to the vertical transfer register through one of the sensor units, either the frame read operation or the field read operation is possible.

When the charge storage layer on the surface forming the sensor section is also used as the channel stop region between the sensor section and the vertical transfer register, the structure can be simplified and the manufacturing process can be reduced.

An edge of one side of the sensor section on the side between the sensor sections is separated from the first electrode except for the read gate section, and the sensor section also serving as a channel stop region around the other section of the sensor section except the read gate section. When the surface charge storage layer is formed, the signal charge from the sensor part is prevented from being erroneously read out to the vertical transfer register on the opposite side between the sensor parts due to the narrow channel effect of the charge storage layer. The signal charge can be reliably read to the vertical transfer register.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a main part showing an embodiment of a solid-state imaging device according to the present invention.

FIG. 2 is a sectional view taken along line BB in FIG.

3 is a cross-sectional view taken along the line CC of FIG.

FIG. 4 is a configuration diagram of a main part showing another embodiment of the solid-state imaging device according to the present invention.

5 is a cross-sectional view taken along the line D-D in FIG.

6 is a cross-sectional view taken along the line EE of FIG.

FIG. 7 is a potential diagram on line FF in FIG.

FIG. 8 is a configuration diagram of a main part showing another embodiment of the solid-state imaging device according to the present invention.

FIG. 9 is a configuration diagram showing a conventional solid-state imaging device.

10 is a cross-sectional view taken along the line AA of FIG.

[Explanation of symbols]

31 CCD solid-state image sensor, 32 sensor unit, 33 vertical transfer register, 34 transfer electrode, 35 first electrode, 36
Second electrode, 38 readout gate section, 39 channel stop region, 45 hole accumulation layer on sensor section surface

Claims (5)

(57) [Claims] 1. A plurality of sensor parts and a vertical transfer register corresponding to each sensor part row are provided, and a transfer electrode of the vertical transfer register is formed by repeating a first electrode and a second electrode corresponding to each sensor part. The first electrode and the second electrode are formed continuously between the vertically adjacent sensor units, and the first electrode and the second electrode are vertically adjacent sensor units.
In the vertical direction so that they partially overlap each other
Each sensor section has a charge storage layer on its surface , and each sensor section has one side.
Except for the part in contact with the readout gate between the sensor parts of
Part entire circumference is formed inward than the required distance charge storage layer, the signal readout of each sensor unit is characterized by comprising taking place through under the first electrode between the sensor portion of each said one side of the Solid-state image sensor. 2. The sensor section is separated from the vertical transfer register by a predetermined distance, and a channel stop region is formed under at least a first electrode between the sensor sections on one side except at least a read gate section. The solid-state image sensor according to claim 1. 3. The solid-state imaging device according to claim 2, wherein a channel stop region is formed under the first electrode and under the second electrode except the read gate portion between the sensor portions on the one side. element. 4. The charge storage layer of the sensor unit having a charge storage layer on the surface thereof also serves as a channel stop region between the sensor unit and the vertical transfer register. The solid-state image sensor according to claim 1. 5. An edge of the sensor section on the inter-sensor section side of the one side is separated from the first electrode except the read gate section, and is provided around the other section of the sensor section except the read gate section. 2. The solid-state image pickup device according to claim 1, wherein a charge storage layer on the surface of the sensor portion that also serves as a channel stop region is formed.