JP3120486B2 - CCD linear sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a CCD linear sensor.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 4, a CCD linear sensor has a plurality of light receiving portions 3 corresponding to respective pixels partitioned by a channel stop region 1 and a light shielding layer 2 made of, for example, Al.
Are arranged in one direction, and a horizontal shift register section 6 having a CCD structure is arranged on one side of each charge storage area 4 including the light receiving section 3 via a readout gate section 5.

In this CCD linear sensor 7, the light receiving section 3
After the signal charge photoelectrically converted in accordance with the received light amount is accumulated in each charge accumulation unit 4 and the signal charge e is read out to the horizontal shift register unit 6 through the readout gate unit 5, 6 is transferred in the horizontal direction and output.

[0004]

The above-mentioned CC
The D linear sensor 7 has a configuration in which the charge storage unit 4 including the light receiving unit 3 is formed to be elongated (a width a is, for example, several μm, and a length b is, for example, about 200 μm) for a bar code reader or the like.

However, in the CCD linear sensor 7 in which the charge storage section 4 is elongated, there is a fear that the transfer efficiency of the signal charge from the charge storage section 4 to the horizontal shift register section 6 is low and an afterimage is generated. That is, in the charge storage unit 4, the read electric field is strong at both ends in the longitudinal direction due to the electric field from the channel stop region 1 and the read gate unit 5, but the read electric field is weak in the longitudinal middle part a. Therefore, the transfer of the signal charge cannot be performed sufficiently.

The present invention has been made in view of the above circumstances, and provides a CCD linear sensor capable of completely transferring signal charges from a light receiving section to a horizontal shift register section, shortening a reading time, and the like.

[0007]

According to the present invention, a charge accumulating section 4 is provided.
Are arranged in an example, and correspond to the pixels.
To transfer the signal charges read from the charge storage section 4.
Shift register unit 6, charge storage unit 4, shift register unit
6, the signal charge of the charge storage section 4 is shifted by a shift register.
The readout gate 5 for reading out to the star section 6 is not provided.
A CCD linear sensor, and a charge storage unit 4 for each pixel.
In the middle part a of the charge accumulation part 4 in the longitudinal direction.
A region having an impurity concentration different from that of the upper region 16.
17 are formed on both sides of the center line and shifted from the charge storage section 4.
In the direction of reading charges to the register section 6, impurities
The configuration is such that the potential difference is provided by changing the width W between the regions 17 having different densities .

[0008]

According to the present invention, an intermediate portion a of each charge storage portion 4 is provided.
The Oite, electricity from the charge accumulation unit 4 to the shift register section 6
Regions 1 with different impurity concentrations in the load readout direction
By changing the width between the gates 7, that is, the width W of the region 16, to give a potential difference, the read electric field at the intermediate part a is improved, and the signal charge from the charge storage part 4 to the shift register part 6 is transferred. Complete transfer is possible, and read time can be reduced.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.

In the embodiment of FIG. 1, similarly to FIG. 4, the channel stop region 1 and a light receiving section 3 which is a plurality of pixels partitioned by a light shielding layer 2 made of, for example, Al are arranged in one direction. A horizontal shift register section 6 having a CCD structure is arranged on one side of each charge storage section 4 including the section 3 via a readout gate section 5. Each charge storage section 4 is formed in a substantially rectangular shape whose length b is sufficiently larger than its width a.

FIG. 2 is a cross-sectional view of the charge storage section 4 including the light receiving section 3 taken along line AA of FIG. In this example, a second conductivity type, that is, a P-type well region 12 is formed on a first conductivity type, for example, an N-type semiconductor substrate 11, and the P-type well region 12 is formed.
An N-type region 3 is formed on the substrate to form a photodiode structure. The channel stop region 1 is composed of a high-concentration P-type region. Reference numeral 14 denotes an insulating film such as SiO ₂ .

Thus, in this embodiment, FIGS. 1 and 2
As shown in (1), a potential difference is formed toward the horizontal shift register section 6 on the intermediate portion where the read electric field of each charge storage section 4 is weakened. For this reason, except for the region 16 in which the width W is gradually increased toward the horizontal shift register 6 in the intermediate portion, other regions, that is, the channel stop region 1 on the opposite side of the horizontal shift register 6 to the charge storage 4 Is implanted, for example, with a low concentration of boron B to form an impurity introduction region 17 which is an N ⁻ region or a P region having an impurity concentration different from that of the region 16. In determining the shape of the impurity introduction region 17, points to be noted are that the charge accumulation portion 4 is line-symmetric with respect to the center line in the longitudinal direction, that a potential difference is provided near the intermediate point a, and that the read electric field is other than the intermediate portion. And the reduction of the amount does not increase.

According to the above-described structure, boron B is ion-implanted into the other portion in the middle portion of the charge storage portion 4 except for the region portion 16 gradually widening toward the horizontal shift register portion 6. By forming the impurity introduction regions 17 having different concentrations, the potential is shallow due to the influence of the electric field of the impurity introduction region 17 where the width W of the region 16 is small, and the impurity introduction region is large where the width W is large. The effect of the electric field 17 is weak and the potential is deep.
As a result, an inclined potential is generated in the intermediate portion such that the potential gradually increases in the charge readout direction , and the so-called readout electric field strength is improved.

For this reason, the deterioration of the charge transfer efficiency in the intermediate portion in the related art is improved, the signal charges can be completely transferred from the charge storage section 4 to the horizontal shift register section 6, and the read time can be reduced. .

In FIG. 1, a plurality of light receiving sections 3 are arranged in one direction.
CCD provided with one horizontal shift register section 6 on one side
Although applied to the linear sensor 18, as shown in FIG. 3, horizontal shift register sections 6A and 6B having a CCD structure are provided on both sides of a plurality of light receiving sections 3 arranged in one direction via readout gate sections 5A and 5B, respectively. The signal charge e ₁ of every other light receiving unit 3 is read out to the first horizontal shift register unit 6A, and the signal charge e ₂ of the other light receiving unit 3 is read out to the second horizontal shift register unit 6B. C to read
The same can be applied to the CD shift register 19. In this case, for example, boron having a low concentration is implanted by leaving a region 16 gradually widening toward the corresponding horizontal shift register units 6A and 6B at the intermediate portion of each charge storage unit 4 to implant impurity introduction regions 17. Are formed, and a potential difference is provided in each of the region portions 16. As a result, complete transfer of the signal charge, reduction of the read time, and the like can be achieved as in the case of FIG.

In the above example, the CC having the elongated light receiving portion
Although the D linear sensor has been described, the present invention can also be applied to a CCD linear sensor having a light receiving section of an appropriate shape.

[0017]

According to the present invention, it is possible to improve the electric field in the middle portion of the CCD linear sensor where the readout electric field is weak, without changing the shape of the charge storage portion in the pixel, that is, the charge storage portion thereof. . Therefore, it is possible to shorten the reading time from the charge storage unit to the shift register unit as a whole, to enable the complete transfer of the signal charge, and to prevent the occurrence of an afterimage. A CCD linear sensor capable of so-called high-speed sampling drive can be provided.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an example of a CCD linear sensor according to the present invention.

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is a configuration diagram showing another example of a CCD linear sensor according to the present invention.

FIG. 4 is a configuration diagram of a conventional CCD linear sensor.

[Explanation of symbols]

 Reference Signs List 1 channel stop region 2 light shielding layer 3 light receiving unit 4 charge storage unit 5, 5A, 5B read gate unit 6, 6A, 6B horizontal shift register 7, 18, 19 CCD linear sensor 16 region 17 impurity introduction region

Continuation of the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01L 27/148 H04N 5/335 H04N 1/028

Claims (1)

(57) [Claims] A plurality of pixels each having a charge storage section are arranged in a line.
Are arranged and read from the charge storage section in correspondence with the pixels.
A shift register unit for transferring the discharged signal charges,
Provided between the charge storage unit and the shift register unit;
Reads signal charges from the charge storage section into the shift register section
CCD linear sensor with read gate
A support, Oite an intermediate portion of the charge storage part of each pixel, impurities concentrated in the longitudinal direction of the center line region of the charge storage unit
Areas with different impurity concentrations from the center line on both sides of the center line.
Formed from the charge storage unit to the shift register unit.
Toward the charge read direction, CCD made with a potential difference by changing the width between different regions of the impurity concentration
Linear sensor.