JP2002252340A - Solid-stage imaging element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a decrease in yield due to insulation faults between a reading electrode 4 and a wiring film 8 for transmitting a transfer pulse intersecting in a three-dimensional manner via an interlayer insulating film 10 and a breakdown voltage fault in a solid-stage imaging element of a type having the film 8 for transmitting the transfer pulse to transmit the pulse between transfer electrodes of an adjacent transfer register 5, as shown in Figs. 4 and 5. SOLUTION: The solid-stage imaging element comprises the interlayer insulating film 10 for interlayer insulation between the reading electrode 4 and a transfer drive wiring film 8 and having an insulating film 10a thicker than the insulating film covering photodetectors 2 completely for the part intersecting the electrode 4 with the film 8 in a three-dimensional manner.

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, in particular, an image pickup section having a light receiving element disposed in one direction on a semiconductor substrate, and a light receiving element disposed in parallel to one side thereof. A transfer register driven by a transfer electrode made of first-layer and second-layer polysilicon, which transfers the signal charge of the second direction to the charge detection section along the one direction. A plurality of light-receiving lines, which are provided between the light-receiving elements and read out from the respective light-receiving elements to the transfer register by being driven by a readout electrode made of a first-layer polysilicon, are provided in parallel; A solid-state imaging device used as a linear sensor.

[0002]

2. Description of the Related Art FIG. 3 is a schematic plan view showing one conventional example of a color linear sensor comprising a solid-state image sensor. 1
R, 1G and 1B are light receiving lines, which are provided in parallel to a straight line (the direction of this straight line is referred to as “X direction” for convenience), 1R is for red detection, 1G is for green detection, and 1B is for blue detection. And each light receiving line has the same structure. 2,
Numerals 2,... Are light receiving elements formed of photodiodes, which receive light from the object side and perform photoelectric conversion. The light receiving elements are arranged in the X direction and constitute light receiving lines 1R, 1G, and 1B. Reference numerals 3, 3,... Denote readout units, which are controlled by the first-layer polysilicon transfer electrode 4 on the semiconductor substrate to describe signal charges from the respective light receiving elements 2, 2,. It plays the role of reading to the transfer register (5).

A transfer register 5 has the same structure as that of a horizontal transfer register of an area sensor type CCD solid-state image pickup device, and has the same operating principle. Here, an area sensor type CCD solid-state imaging device is a device in which light receiving elements forming the core of a pixel are arranged vertically and horizontally, and a vertical transfer register is provided corresponding to each vertical column of the light receiving elements. A CCD type solid-state imaging device in which a horizontal transfer register for transferring the signal charge from the light receiving element in the horizontal direction is provided by a register, and a charge detection unit for converting the signal charge into a voltage is provided on the transfer destination side of the horizontal transfer register Say.

In the horizontal transfer register, transfer sections and storage sections having different impurity concentrations are alternately arranged on the surface of the substrate along the transfer direction of signal charges, and the transfer section and the transfer section are adjacent to the transfer destination side. This is a register that constitutes one bit with the storage unit to be transferred, and is transferred by a two-phase transfer pulse by a transfer electrode made of, for example, polysilicon formed on a semiconductor substrate via a gate insulating film. The transfer electrode that drives the transfer unit and the transfer electrode that drives the storage unit that constitutes one bit by the transfer unit are different from each other in the polysilicon film (the first polysilicon film 1st-Po).
ly and the second-layer polysilicon film 2nd-Poly), and receive the same (the same phase) transfer pulse as each other. In FIG. 3, the transfer electrode is not shown. Reference numeral 6 denotes a transfer pulse applying electrode which receives a two-phase transfer pulse from outside the solid-state imaging device and transmits the transfer pulse to the transfer electrode, and is made of, for example, aluminum. The electrodes are shown as if they were one for convenience, but there are two, and two-phase pulses are transmitted to the transfer electrodes. In this conventional example, the transfer pulse applying electrode 6 is provided with red, green, and blue light receiving lines 1R, 1R,
One set was provided for each of G and 1B.

[0005] Reference numerals 7, 7, and 7 denote charge detectors provided on the transfer destination side of each transfer register 5, and convert signal charges from the respective light receiving elements 2 transferred from the transfer register 5 into voltages. The insulating film covering the substrate surface of the CCD type solid-state imaging device of the linear sensor type has a three-layer structure including a silicon oxide film, a silicon nitride film and a silicon oxide film in order to stabilize transfer characteristics on the transfer register 5. (That is, the transfer register has a MONOS structure), and the portion where the light receiving element 2 is provided is made of only one silicon oxide film in order to secure transparency and improve sensitivity. I have. In addition, the portion that becomes the gate insulating film of the transistor that forms the charge detection section also includes only one silicon oxide film.

FIG. 4 is a schematic plan view schematically showing another type. This solid-state imaging device is different from FIG. 1 in that the transfer pulse applying electrode 7 is not provided for the green light receiving line 1G, but the transfer of the light receiving line 1B from the transfer pulse applying electrode 6 corresponding to the blue light receiving line 1B. The two-phase transfer pulse is transmitted to the transfer electrode of the green light receiving line 1G via the transfer electrode of the register 5 (the transfer electrode made of polysilicon of the second layer) and the transfer pulse transmission wiring film 8. The transfer pulse transmission wiring film 8 is made of a second-layer polysilicon. In the red light receiving line 1R, the arrangement order of the light receiving element 3, the readout section 3, the transfer register 5, and the transfer pulse applying electrode 6 is opposite to that of the conventional example shown in FIG. Other than these differences, there is no difference between the one shown in FIG. 3 and the one shown in FIG.

In the solid-state image pickup device shown in FIG. 4, the dimension in the direction perpendicular to the X direction (signal charge transfer direction) of the CCD type solid-state image pickup device constituting the color linear sensor shown in FIG. It is something which raised. That is, by not providing the transfer pulse applying electrode 5 for the green light receiving line 1G, the dimension in the X direction is correspondingly reduced.

FIG. 5A is an enlarged plan view showing a green light receiving line 1G and a blue light receiving line 1B in the solid-state imaging device shown in FIG. 4, and FIG. The transfer pulse transmission wiring films 6, 6,... Of the solid-state imaging device shown in FIG.
FIG. 4 is an enlarged plan view showing the vicinity thereof. In the figure, reference numerals 2g and 2b denote regions where the green and blue light receiving elements 2 are provided. As described above, in these regions 2g and 2b, the surface of the semiconductor substrate is composed of only one silicon oxide film. , Sensitivity is ensured. Specifically, after the formation of the three-layered interlayer insulating film, the upper two layers of the film, that is, the silicon oxide film and the silicon oxide film are selectively removed by etching, whereby the thickness of the interlayer insulating film is reduced. Is selectively thinned. Reference numeral 4 denotes a read electrode made of polysilicon of the first layer, 5a and 5b denote transfer electrodes made of polysilicon for driving the transfer register 5, and 5a denotes a second electrode.
The layer 5b is made of the first-layer polysilicon. Reference numeral 8 denotes the above-described transfer pulse transmission wiring film, which is made of polysilicon of the second layer. The transfer pulse transmission wiring film 8 includes the transfer electrode 5a of the register 5 of the blue light receiving line 1B and the green light receiving line 1G. And the transfer electrode 5a of the register 5 is integrally formed, and the space therebetween is integrally connected.

Incidentally, the solid-state imaging device shown in FIGS. 4 and 5 has a structure as shown in FIGS. 6A and 6B in the related art. FIG. 6A is an enlarged plan view showing a conventional planar structure of the region shown in FIG.
(B) is a sectional view taken along line YY '. In FIG. 6, 9L indicates that an interlayer insulating film between a first polysilicon layer and a second polysilicon layer is a silicon oxide film,
A boundary between a portion 10a having a three-layer structure composed of a silicon nitride film and a silicon oxide film and a portion 10b composed of only one silicon oxide film, the boundary 9L being formed on a straight line extending in the X direction, 4 and the portion between the transfer pulse transmission wiring films 8. That is,
The interlayer insulating film 10 that insulates between the read electrode 4 and each transfer pulse transmission wiring film 8 has a thick portion 10a and a thin portion 10b.

Conventionally, this is done to improve the sensitivity of each light receiving element 1. That is, the thick portion 10a of the interlayer insulating film 10 is
The area to be thinned so as not to cover the
Above, in order to ensure clearance in consideration of dimensional variations, they are overlapped.
Numeral 11 is the overlap portion.

[0011]

FIGS. 4 and 5 show an embodiment of the present invention.
In the solid-state image pickup device of the type shown in FIG. 6, since the conventional structure shown in FIGS. 6A and 6B has been used at the portion where the readout electrode and the transfer pulse transmission wiring film cross three-dimensionally, the interlayer insulation failure has occurred. There was a problem that it was easy to get up. That is,
Insulation failure and breakdown voltage failure may occur in the thin portion 10b of the interlayer insulating film 10 that insulates between the readout electrode 4 and each transfer pulse transmission wiring film 8, resulting in a decrease in yield.

The present invention has been made to solve such a problem, and a transfer pulse transmitting wiring film for transmitting a transfer pulse between transfer electrodes of adjacent transfer registers as shown in FIGS. In the type of solid-state imaging device having
An object of the present invention is to reduce the defective rate of insulation failure and breakdown voltage failure between a readout electrode and a transfer pulse transmission wiring film that three-dimensionally intersects via an interlayer insulating film, and improve the yield.

[0013]

According to a first aspect of the present invention, there is provided a solid-state imaging device comprising an interlayer insulating film for interlayer insulation between a read electrode and a transfer drive wiring film, and the read electrode and a transfer pulse transmission wiring film. It is characterized in that the three-dimensionally crossing portions are all thicker than the insulating film covering the light receiving element.

Therefore, according to the solid-state imaging device of the first aspect, the portion of the interlayer insulating film where the readout electrode and the transfer pulse transmission wiring film three-dimensionally cross each other is thicker than the insulating film covering the light receiving element. As a result, the rate of occurrence of insulation failure and breakdown voltage failure between the readout electrode and the transfer pulse transmission wiring film can be reduced. Thus, the yield of the solid-state imaging device can be improved.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention basically has a type having a transfer pulse transmission wiring film for transmitting a transfer pulse between transfer electrodes of adjacent transfer registers as shown in FIGS. , And in general, a solid-state imaging device used as a color linear sensor. In the illustrated embodiment described later, the present invention is applied to a solid-state imaging device using a primary color (red, green, blue) filter, but the scope of the present invention is not necessarily limited thereto. The present invention can be applied to a solid-state imaging device using a complementary color filter.

[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 show a main part of a first embodiment of a solid-state imaging device according to the present invention. FIG. 1A shows a solid-state imaging device of the type shown in FIGS. 4 and 5A. FIG. 5B is an enlarged plan view of a region indicated by A in FIG. 5B of the solid-state imaging device forming the color linear sensor, and FIG. 1B is a cross-sectional view taken along line YY ′.
A plan view showing a schematic configuration of the present solid-state imaging device is omitted because it is the same as FIG. 4, and a green light receiving line 1G and a blue light receiving line 1B in the solid-state imaging device shown in FIG. FIG. 5A is the same as FIG. 5A, and the enlarged plan view of the portion shown in FIG. 5A is the same as FIG. 5B.

In FIG. 1, reference numeral 9L denotes a three-layer insulating film formed of a silicon oxide film, a silicon nitride film and a silicon oxide film between the first polysilicon layer and the second polysilicon layer. A boundary between a portion 10a having a layer structure and a portion 10b composed of only one silicon oxide film,
As shown in FIGS. 1A and 1B, the boundary 9L bypasses the portion where the readout electrode 4 and the transfer driving wiring film 8 intersect three-dimensionally. The overlap 11 is formed as shown in FIG.

That is, a thin portion of the insulating film 10 (specifically, two layers (a silicon oxide film and a silicon nitride film) on an insulating film having a three-layer structure composed of a silicon oxide film, a silicon nitride film, and a silicon oxide film. ) Is removed by selective etching to leave only the lowermost silicon oxide film) 10b overlaps not only on the light receiving elements 2, 2,...
In the related art, the transfer driving wiring film 8 overlaps the read electrode 4 even at a portion where the transfer driving wiring film 8 crosses three-dimensionally. However, in the present solid-state imaging device, the boundary 9L is bypassed so that such overlap does not occur at a portion where the transfer driving wiring film 8 crosses the readout electrode 4 three-dimensionally. This is the difference between the present solid-state imaging device and the conventional solid-state imaging device shown in FIG.

Therefore, according to the solid-state imaging device shown in FIG. 1, the insulation failure and the breakdown voltage failure due to the interlayer insulating film 10 at the portion where the transfer drive wiring film 8 crosses the read electrode 4 three-dimensionally are less likely to occur. , And the yield is improved. Specifically, it has been confirmed that the yield is improved by 5% or more.

FIG. 2 is a process chart showing a process flow from the formation of the insulating film covering the surface of the semiconductor substrate to the formation of the transfer electrode. First, a first silicon oxide film is formed on a substrate, then a silicon nitride film is formed thereon, and a silicon oxide film is further formed thereon. The reason why the three-layer insulating film is formed is to make the transfer register have a MONOS structure (a MONOS structure process under a transfer section).

Next, a transfer electrode 5b (see FIG. 5) made of first layer polysilicon and a read electrode 4 are formed (transfer section / read electrode formation (1st-Poly)).
Specifically, a polysilicon film is formed by CVD, and thereafter, the film is patterned. Next, an interlayer insulating film for interlayer insulation between the electrode made of the first layer of polysilicon and the electrode made of the second layer of polysilicon is formed (formation of an insulating oxide film between the first Poly and the second Poly).

Next, the MOS transistor (M
The silicon oxide film and the silicon nitride film of the insulating film on the OS transistor) forming portion and the light receiving elements 2, 2,... Are removed (removal of the MOS transistor portion + the oxide film and the nitride film of the light receiving portion). At the time of this removal, in the case of the present solid-state imaging device,
By changing the pattern of the region to be removed as described above, the portion where the readout electrode 4 and the transfer driving wiring film 8 cross three-dimensionally is not removed.

Next, an oxide film for a MOS transistor is formed (formation of an oxide film). Specifically, C of the silicon oxide film
It is formed by VD formation and its selective etching. Then, the transfer electrode 5a made of the second-layer polysilicon, the transfer drive wiring film 8, and the MOS of the detection unit (output unit)
Form gate electrodes of transistors (transfer section / transfer drive wiring film, output section MOS transistor gate section formation (2
ndPoly)). Specifically, the polysilicon film is
It is formed by a method D, and thereafter, the polysilicon film is selectively etched.

Incidentally, this series of steps is basically the same as the conventional one. However, the pattern for removing the silicon oxide film and the silicon nitride film is different (there is a difference between FIG. 1A and FIG. 6A).

[0025]

According to the solid-state imaging device of the present invention, the portion of the interlayer insulating film where the read electrode and the transfer pulse transmitting wiring film cross each other in three dimensions is thicker than the insulating film covering the light receiving element. Therefore, the rate of occurrence of insulation failure between the readout electrode and the transfer pulse transmission wiring film can be increased. Thus, the yield of the solid-state imaging device can be improved.

[Brief description of the drawings]

FIGS. 1A and 1B show a main part of a first embodiment of a solid-state imaging device according to the present invention, and FIGS. 1A and 4A are FIGS.
5B is an enlarged plan view of a region indicated by A in FIG. 5B of the solid-state imaging device shown in FIG. 5B, and FIG. 5B is a cross-sectional view taken along line YY ′ of FIG.

FIG. 2 is a view sequentially showing a part of a manufacturing process of the solid-state imaging device.

FIG. 3 is a plan view showing one schematic configuration of a conventional example of a solid-state imaging device.

FIG. 4 is a plan view illustrating a schematic configuration of a solid-state imaging device of a type to which the present invention is applied.

5A and 5B are plan views of the solid-state imaging device shown in FIG. 4; FIG. 5A is an enlarged plan view of a green light receiving line and a blue light receiving line; FIG. 2 is an enlarged plan view showing a part shown in FIG.

6 (A) is a plan view, and FIG. 6 (B) is a cross-sectional view taken along line YY ′ of FIG. 6 (A), showing a main part of a conventional example of a solid-state imaging device of the type shown in FIGS. It is.

[Explanation of symbols]

4 ... readout electrode, 5 ... transfer register, 5a
..Transfer electrodes made of second layer polysilicon, 5b
..Transfer electrodes made of first-layer polysilicon, 6
・ Transfer pulse application electrode, 8 ... Transfer drive wiring film, 9
L: Boundary between thinned portion and thickened portion of insulating film, 10: insulating film, 10a: non-thinned portion of insulating film (thick portion), 10b: thinned portion of insulating film .

Claims (1)

[Claims] An image pickup section having a light receiving element disposed in one direction on a semiconductor substrate, and an image pickup section disposed in parallel to one side of the imaging section, and detecting signal charges from each of the light receiving elements along the one direction. A transfer register driven by a transfer electrode made of first-layer and second-layer polysilicon, and a first-layer polysilicon provided between the transfer register and the imaging unit. A plurality of light receiving lines, each of which is constituted by a reading section driven by a read electrode and reading data from each of the light receiving elements to the transfer register, are provided in parallel with each other; Does not have a transfer pulse applying electrode corresponding to itself, and the transfer electrode is connected to the transfer electrode and transfer pulse transmitting wiring from the transfer pulse applying electrode for the transfer register of another light receiving line. Receiving the transfer pulse via the semiconductor substrate, and the insulating film on the semiconductor substrate and the interlayer insulating film between the first and second polysilicon layers are connected to the light receiving element of each light receiving line and the charge detection. In the solid-state imaging device made thinner than the other parts on the part, the part of the interlayer insulating film in which the readout electrode and the transfer drive wiring film three-dimensionally cross each other is the insulating film covering the light receiving element and the charge detecting part. A solid-state imaging device characterized in that the thickness is also increased.