JP2000114505A - Ccd solid-state image sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the size of a CCD solid-state image in the longitudinal direction (vertical transfer direction) thereof by applying a DC bias to a transfer electrode by using a light shielding film as a bus line. SOLUTION: An Hϕ bus line 9 is connected electrically with respective horizontal transfer electrodes 5tp and 5sp through a contact hole 12. A light shielding film 13 above all wiring layers is made of aluminum and it is formed so as to cover an image sensing area and a horizontal transfer resistor 6 and the respective light receiving photodector are provided with light receiving windows to pass light. The light shielding film 13 is formed at ground level, and it is connected electrically with perpendicular transfer electrodes 5tg and 5sg subject to DC bias through a contact hole 14. Therefore, the respective vertical transfer electrodes 5tg and 5sg subjected to DC bias are connected with the light shielding film 13 through the contact hole 14, and the light shielding film 13 is formed at ground level and it is subject to DC bias at ground level.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a CCD solid-state imaging device, and more particularly, to a CCD having a transfer electrode to which a DC bias is applied and a transfer electrode receiving one or more transfer clock pulses as a horizontal transfer electrode for driving a horizontal transfer register. In addition, the present invention relates to a CCD solid-state imaging device in which a light-shielding film having a window for transmitting light to each light-receiving device is formed above the imaging region where the light-receiving device is provided.

[0002]

2. Description of the Related Art In general, a CCD solid-state image pickup device has light-receiving elements arranged in a matrix in an image pickup area, and transfers signal charges from the light-receiving elements in the column in the vertical direction corresponding to each light-receiving element column. A vertical transfer register, a horizontal transfer register for transferring the signal charges transferred vertically in a horizontal direction to a transfer destination side of the vertical transfer register, and a light receiving element. It has a configuration in which a light-shielding film made of, for example, aluminum having a window through which light passes for each light-receiving element is formed on the upper side, and a horizontal transfer register uses a horizontal transfer electrode that receives a two-phase clock pulse. Many are driven, but transfer electrodes receiving a one-phase clock and transfer electrodes receiving a transfer electrode receiving a DC bias pulse are alternately arranged so that transfer is performed in the horizontal direction. Some of which were so.

Such a type has an advantage that the number of pulse phases required for horizontal transfer can be reduced. 2A to 2C show such a type of CCD.
1A shows a solid-state imaging device, in which FIG. 2A is a cross-sectional structural view of a horizontal transfer register, and FIG.
FIG. 7C is a waveform diagram of the C bias, and FIG. 7C is a diagram showing a change in potential distribution for explaining transfer of signal charges.

In the drawings, reference numeral 1 denotes an N-type semiconductor substrate, 2 denotes a P-type well, 3 denotes an N-type channel, and 3t denotes that a portion of the surface of the N-type channel 3 to be selectively doped with an impurity is to be a horizontal transfer register. The N ^- type transfer portion 3s is a storage portion provided on the transfer destination side corresponding to each transfer portion in a portion serving as a horizontal transfer register on the surface portion of the N-type channel 3, and the N-type channel 3 (that is, doping of impurities for forming the transfer portion is not performed).

Reference numeral 4 denotes a gate insulating film made of silicon oxide formed on the surface of the semiconductor substrate 1. Reference numeral 5 denotes a horizontal transfer electrode for driving a horizontal transfer register. Reference numeral 5tg denotes a transfer portion which is DC-biased to a ground potential (GND). The driving horizontal transfer electrode 5sg is the storage unit driving horizontal transfer electrode 5sp which is also DC-biased to the ground potential.
Is a horizontal transfer electrode for driving the storage section which receives the horizontal transfer pulse Hφ, and 5tp is a horizontal transfer electrode for driving the transfer section. As described above, this type of CCD solid-state image pickup device has the DC-biased horizontal transfer electrodes 5tg, 5tg,
sg and horizontal transfer electrode 5t receiving horizontal transfer pulse Hφ
p and 5sp are alternately arranged along the horizontal transfer direction.

A DC bias of a ground level (GND) is applied to the horizontal transfer electrodes 5tg and 5sg, and a positive high voltage higher than the ground level by a certain voltage is applied to the horizontal transfer electrodes 5tp and 5sp. This is a one-phase pulse Hφ that changes at a fixed cycle between the level and a low level that is lower than the ground level by a certain voltage.

The horizontal transfer operation will be described with reference to FIG. At time t1 when the horizontal transfer pulse Hφ is at the high level, the portion controlled by the horizontal transfer electrodes 5tp and 5sp receiving the same has a deeper potential than the portion controlled by the horizontal transfer electrodes 5tg and 5sg receiving the DC bias. . At time t2 when the level of the horizontal transfer pulse Hφ changes from the high level to the low level and reaches the level equal to the ground level, the part controlled by the horizontal transfer electrodes 5tp and 5sp naturally receives the DC bias. The potential controlled by the electrodes 5tg and 5sg has the same depth.

At time t3 when the horizontal transfer pulse Hφ becomes low level, the horizontal transfer electrodes 5tp, 5s
The portion controlled by p has a shallower potential than the portion controlled by the horizontal transfer electrodes 5tg and 5sg receiving the DC bias, and the signal charge moves by one bit.

FIG. 3 is a plan view of a horizontal transfer register showing a conventional example of a CCD solid-state imaging device of the type receiving the DC bias described above. In the drawing, 5sg, 5tg, 5
sp and 5tp indicate horizontal transfer electrodes as in FIG. Reference numeral 6 denotes a horizontal transfer register, 7 denotes a vertical transfer register connected to the horizontal transfer register 6, and 8 denotes a vertical transfer electrode for driving the horizontal transfer register 6, which receives, for example, four-phase vertical transfer pulses. Reference numeral 9 denotes an Hφ bus line, and reference numeral 10 denotes a ground line. Both bus lines 9 and 10 are layers above the first polysilicon layer and the second polysilicon layer forming the horizontal transfer electrode 5 and the vertical transfer electrode 8. Of the wiring layers. The ground line 10 and each of the horizontal transfer electrodes 5tg and 5sg receiving the DC bias are electrically connected through a contact hole 11. The Hφ bus line 9 and each of the horizontal transfer electrodes 5tp and 5sp receiving the pulse Hφ are electrically connected through a contact hole 12.

Reference numeral 13 denotes a light-shielding film above any wiring layer.
It is made of aluminum, is formed so as to cover the imaging region and the horizontal transfer register 6, and has a light receiving window (not shown in the drawing) through which light passes on each light receiving element.

[0011]

By the way, in the conventional CCD solid-state image pickup device having the structure as shown in FIG. 3, two bus lines of an Hφ bus line 9 and a ground bus line 10 are used as horizontal transfer operation bus lines. Have
Restricting the size in the vertical direction (vertical transfer direction) was restricted. However, even in such a type of CCD solid-state imaging device, it is required to reduce the chip size, and such a restriction hinders meeting the demand for reducing the chip size.

The present invention has been made to solve such a problem, and receives a transfer electrode to which a DC bias is applied and a transfer clock pulse of one or more phases as a horizontal transfer electrode for driving a horizontal transfer register. In a CCD solid-state image sensor having a transfer electrode and a light-shielding film having a window through which light passes for each light-receiving element above the imaging region in which the light-receiving element is provided, a vertical direction of the CCD solid-state image sensor is provided. It is intended to reduce the size in the (vertical transfer direction).

[0013]

According to a first aspect of the present invention, there is provided a CCD solid-state imaging device, wherein a DC bias is applied to a transfer electrode to which a DC bias is applied by using a light shielding film as a bus line. Features.

Therefore, according to the CCD solid-state imaging device of the first aspect, since the DC bias is applied to the transfer electrode using the light-shielding film as the bus line, there is no need to provide a special DC bias bus line. Therefore, the size of the CCD solid-state imaging device chip in the vertical direction (vertical transfer direction) can be reduced, and the chip size, the set size, and the wafer theoretical yield can be increased. Also, D
Since the C bias bus line is unnecessary, the pattern shape required for the bus line is simplified, which leads to a reduction in the defective rate and a reduction in cost.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The CCD solid-state image pickup device of the present invention basically has a configuration in which light-receiving elements are arranged in a matrix in an image pickup area, and signals from the light-receiving elements in that column correspond to vertical columns of each light-receiving element. A vertical transfer register for transferring charges in the vertical direction is provided, and a horizontal transfer register for transferring the signal charges transferred in the vertical direction in the horizontal direction is provided on the transfer destination side of the vertical transfer register. It has a transfer electrode to which a DC bias is applied as a horizontal transfer electrode for driving a register and a transfer electrode for receiving a transfer clock pulse of one or more phases. The present invention relates to a CCD solid-state imaging device having a light-shielding film having a window through which light passes through. In such a CCD solid-state imaging device, a DC bias is applied to a transfer electrode to which the DC bias is applied. The application of the scan is made in the manner made using the light shielding film as a bus line.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the illustrated embodiments. FIGS. 1A and 1B are plan views of a horizontal transfer register showing another embodiment of the CCD solid-state imaging device of the present invention. Incidentally, the cross-sectional structure of the horizontal transfer register of each embodiment,
Changes in the DC bias, the transfer pulse Hφ, and the potential distribution are the same as those shown in FIG.

In the drawing, 5sg, 5tg, 5sp,
5tp indicates a horizontal transfer electrode as in FIG. Reference numeral 6 denotes a horizontal transfer register, 7 denotes a vertical transfer register connected to the horizontal transfer register 6, and 8 denotes a vertical transfer electrode for driving the horizontal transfer register, which receives, for example, four-phase vertical transfer pulses. Reference numeral 9 denotes an Hφ bus line, and the bus line 9 is a wiring layer (for example, polysilicon or polysilicon) above the first polysilicon layer and the second polysilicon layer forming the horizontal transfer electrode 5 and the vertical transfer electrode 8. (Metal wiring layer).

The Hφ bus line 9 and each of the horizontal transfer electrodes 5tp and 5sp receiving the pulse Hφ are connected to the contact hole 1
2 are electrically connected.

Reference numeral 13 denotes a light-shielding film above any wiring layer.
It is made of aluminum, is formed so as to cover the imaging region and the horizontal transfer register 6, and has a light receiving window (not shown in the drawing) through which light passes on each light receiving element. The light shielding film 13 is set to the ground level,
It is electrically connected to the biased vertical transfer electrodes 5tg and 5sg via the contact holes 14.

The vertical transfer electrodes 5tg and 5sg, which are DC-biased, are connected to the light-shielding film 13 through the contact holes 14, and the light-shielding film 13 is at the ground level. Be biased. Therefore, the ground bus line existing in the conventional CCD solid-state imaging device shown in FIG.
In the CCD solid-state imaging device shown in (B), it is not required and does not exist. Accordingly, the dimension of the CCD solid-state imaging device chip in the vertical direction (vertical direction) can be reduced accordingly, and the chip size, the set size, and the wafer theoretical yield can be increased. Further, since a DC bias bus line is not required, a pattern shape required for the bus line is simplified, which leads to a reduction in a defective rate and a reduction in cost.

The difference between the one shown in FIG. 1A and the one shown in FIG. 1B is that the contact positions of the contact holes 14 between the vertical transfer electrodes 5tg and 5sg which are DC-biased and adjacent to each other are on the same side ( Upper side)
It is formed at the end of the different side (upper and lower). As shown in FIG. 1B, when the contact holes 14 are not aligned, the size in the horizontal direction (horizontal transfer direction) can be easily reduced, so that the chip size can be more easily reduced.

[0022]

According to the first aspect of the present invention, the DC bias is applied to the transfer electrode by using the light-shielding film as a bus line, so that there is no need to provide a DC bias bus line. . Therefore, the size of the CCD solid-state imaging device chip in the vertical direction (vertical transfer direction) can be reduced, and the chip size, the set size, and the theoretical yield of the wafer can be increased. Further, since a DC bias bus line is not required, a pattern shape required for the bus line is simplified, which leads to a reduction in a defective rate and a reduction in cost.

[Brief description of the drawings]

FIGS. 1A and 1B are plan views showing a horizontal transfer register which is a main part of another embodiment of a CCD solid-state imaging device according to the present invention.

2 (A) to 2 (C) show a type C having a horizontal transfer electrode receiving a DC bias, which is an object of the present invention.
1A shows a cross-sectional structure diagram of a horizontal transfer register, FIG. 2B shows a waveform diagram of a horizontal transfer pulse and a DC bias, and FIG. 1C shows a potential distribution for explaining signal charge transfer. FIG.

FIG. 3 is a plan view of a horizontal transfer register showing a conventional example.

[Explanation of symbols]

5sg, 5tg: Horizontal transfer electrode receiving DC bias, 5sp, 5tp: Horizontal transfer electrode receiving vertical transfer pulse, 6: Horizontal transfer register, 9: Hφ bus line, 13: Light shielding Film, 14 ... contact hole.

Claims (1)

[Claims] 1. A light-receiving element is arranged in a matrix in an imaging region, and a vertical transfer register is provided corresponding to each vertical column of light-receiving elements, for vertically transferring signal charges from the light-receiving elements in the column, A horizontal transfer register for transferring the signal charges transferred in the vertical direction in the horizontal direction is provided on the transfer destination side of the vertical transfer register, and a DC bias is applied as a horizontal transfer electrode for driving the horizontal transfer register. Electrode and 1
Having a transfer electrode receiving a transfer clock pulse of more than one phase,
A CCD in which a light-shielding film having a window for transmitting light to each light-receiving element is formed above the imaging area where the light-receiving element is disposed.
A solid-state imaging device according to claim 1, wherein said DC bias is applied to said transfer electrode to which said DC bias is applied by using said light-shielding film as a bus line.