JPH1126746A - Solid-state imaging device - Google Patents

Abstract

[PROBLEMS] To effectively reduce dark current even in a solid-state imaging device or the like. SOLUTION: A hydrogen introduction window 1 is formed on a SiN film formed as an insulating film constituting a gate insulating film 9 on a semiconductor substrate 1.
4 are formed, and especially, on the semiconductor substrate 1,
The film 18 containing a large amount of hydrogen including at least the position corresponding to the hydrogen introduction window 14 is formed between the hydrogen introduction window 14 and only the insulating film that can transmit hydrogen.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a solid-state imaging device, and more particularly to a solid-state imaging device with improved dark current.

[0002]

2. Description of the Related Art In a silicon semiconductor substrate or the like, it has been known that by supplying hydrogen to the surface of the substrate, the interface state on the surface of the semiconductor substrate is reduced to reduce charge recombination on the surface. I have. Also in a solid-state imaging device having a CCD (charge coupled device) structure, it is desired that dark current be reduced by supplying hydrogen to the surface of a semiconductor substrate such as a Si substrate.

[0003] In particular, an FIT (frame interline transfer) type solid-state imaging device having an imaging section in which a large number of light receiving sections are arranged and a storage section for receiving and temporarily storing signal charges by receiving light, or Since it is necessary to hold the electric charge for a relatively long time in the storage section in an FT (frame transfer) type solid-state imaging device or the like, it is particularly desirable that hydrogen be supplied satisfactorily.

However, in this solid-state imaging device, the gate insulating film, that is, the insulating film formed on the surface of the semiconductor substrate is made of, for example, an SiO ₂ oxide film and an SiN film that cannot transmit hydrogen thereon. When a laminated structure is adopted, supply of hydrogen to the semiconductor substrate becomes a problem.

FIG. 1 is a schematic configuration diagram of an FIT type solid-state imaging device.
For example, an image pickup unit 2, a storage unit 3, a so-called storage unit, a horizontal shift register 4,
An output circuit 5 is formed.

In the image pickup section 2, a large number of light receiving sections 6 each having, for example, a photodiode configuration are arranged in the vertical and horizontal directions along the substrate surface, and are adjacent to the light receiving sections 6 arranged on a common vertical line. A vertical shift register 7 having a CCD configuration is arranged, and a signal charge generated in each light receiving unit 6 according to the amount of received light is taken out to the vertical shift register 7 and transferred to the storage unit 3. Has been made.

[0007] The storage unit 3 includes a vertical shift register 8 similarly arranged with a CCD and arranged corresponding to each vertical shift register 7 of the image pickup unit 2. And temporarily accumulates and holds the signal charge.

The horizontal shift register 4 also has a CCD structure, and charges the electric charges accumulated in the accumulation unit 3 for each horizontal line.
The data is transferred to the output circuit 5.

FIG. 4 shows a conventional FIT configuration or FT
FIG. 2 is a schematic cross-sectional view between adjacent vertical shift registers 8 in the storage unit 3 according to the configuration, in which a channel stop region CS is formed between the vertical shift registers 8 facing the surface of the semiconductor substrate 1. On the surface of the semiconductor substrate 1,
A gate insulating film 9 is formed. This gate insulating film 9
For example, S formed by thermally oxidizing the surface of the Si semiconductor substrate 1
An oxide film 10 of iO ₂ is formed, a SiN nitride film 11 is formed thereon by a CVD (chemical vapor deposition) method or the like, and a SiO ₂ oxide film 19 is further formed thereon.

The vertical shift register 8 includes a gate insulating film 9
Above, transfer electrodes 12 and 13 made of polycrystalline semiconductor layers to which clock voltages of two phases, four phases or the like are applied are alternately arranged in the transfer direction. These transfer electrodes 12 and 13 are arranged in common across all the vertical shift registers 8 so as to be arranged across the vertical shift registers 8, and FIG.
Shows a cross section at a portion laminated via the insulating layer 24.

In the image pickup section 3 as well, since the nitride film 11 for blocking the hydrogen constituting the gate insulating film 9 is formed as described above, for example, the channel stop region CS between the vertical shift registers 8 is formed. On the formation portion, a hydrogen introduction window 14 is formed in the nitride film 11 having a shielding effect on hydrogen. Then, an insulating film 15 serving as an interlayer insulating layer including the inside of the hydrogen introduction window 14 is formed. The insulating film 15 is made of, for example, PSG (phosphorus silicate glass) or BPSG (boron phosphorous silicate glass).
And the like, or by thermally oxidizing the surfaces of the transfer electrodes 12 and 13. The insulating film 15 having this configuration is formed as a film containing some hydrogen.

The interlayer insulating layer, that is, the insulating film 1
A light-shielding film 16 made of a metal film is formed on the entire surface of the light-receiving portion 5, and a light-receiving window 20 is opened on the light-receiving portion 6 shown in FIG. Further, a surface insulating layer 17 called a passivation film is formed on the entire surface. The surface insulating layer 17 is composed of a SiN film (hereinafter, referred to as P-SiN) formed by a plasma CVD method. This P-SiN film is an insulating film containing a large amount of hydrogen, and can be used as a supply source of hydrogen to the semiconductor substrate.

However, in the solid-state imaging device according to this configuration, since the light receiving window 20 is formed in the light shielding film 16 in the light receiving section 2,
Hydrogen can be introduced relatively satisfactorily. However, as is apparent from FIG. 4, in the accumulating portion 3, the insulating film 17 containing a large amount of hydrogen and the hydrogen introduction window 14
Since the light-shielding film 16 made of a metal film that hardly transmits hydrogen is present, the supply of hydrogen in the storage section 3 only receives the supply of hydrogen from the insulating film 15 and a P-SiN film containing a large amount of hydrogen. Supply of hydrogen from the surface insulating film 17 cannot be sufficiently received.

For this reason, this type of solid-state imaging device has a problem that the dark current cannot be sufficiently reduced.

[0015]

In the present invention, the dark current can be effectively reduced even in the above-mentioned FT type or FIT type solid-state image pickup device.

[0016]

A solid-state image pickup device according to the present invention has a structure in which a hydrogen introduction window is formed in a SiN film formed as an insulating film constituting a gate insulating film on a semiconductor substrate. A structure in which a film containing a large amount of hydrogen including a position corresponding to at least the hydrogen introduction window on the semiconductor substrate is formed between the hydrogen introduction window and the hydrogen introduction window only through an insulating film that can transmit hydrogen. . That is, specifically, an insulating layer containing a large amount of hydrogen is formed under the light-shielding film on a portion facing the hydrogen introduction window, and between this and the hydrogen introduction window, hydrogen is blocked. The structure does not pass through a layer, and thus, hydrogen can be effectively introduced into the semiconductor substrate through the hydrogen introduction window, so that the interface state can be effectively reduced, Therefore, the dark current can be reduced.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A solid-state imaging device according to the present invention has an effect of blocking hydrogen constituting a part of a gate insulating film on a semiconductor substrate in an imaging section of, for example, an FT-type or FIT-type solid-state imaging device. A hydrogen introduction window is formed in the SiN film having In particular, a film containing a large amount of hydrogen (hereinafter simply referred to as a hydrogen-containing film) including at least a position corresponding to the hydrogen introduction window on the semiconductor substrate, for example, P-SiN, that is, a film formed by a plasma CVD method. An SiN film is formed, and a metal film, for example, a light-shielding film made of Al or a refractory metal such as W, Ti, or Mo is formed on the SiN film. In this case, only the insulating film through which hydrogen can pass is interposed.

The insulating film through which hydrogen can pass is:
For example, one or more films of silicon oxide, phosphorus silicate glass, and boron phosphorus silicate glass.

Next, an example of the solid-state imaging device according to the present invention will be described in detail. This solid-state imaging device can be applied to, for example, the solid-state imaging device having the storage unit described with reference to FIG. As described above, this solid-state imaging device shows a schematic configuration diagram of an FIT-type solid-state imaging device. This solid-state imaging device includes a semiconductor substrate 1, for example, a Si semiconductor substrate, and mainly includes an imaging unit 2 and a storage unit 3. A so-called storage unit, a horizontal shift register 4, and an output circuit 5 are formed.

In the image pickup section 2, a large number of light receiving sections 6 each having, for example, a photodiode configuration are arranged in the vertical and horizontal directions along the surface of the base, respectively, and are adjacent to the light receiving sections 6 arranged on a common vertical line. A vertical shift register 7 having a CCD configuration is arranged, and a signal charge generated in each light receiving unit 6 according to the amount of received light is taken out to the vertical shift register 7 and transferred to the storage unit 3. Has been made.

The storage section 3 includes a vertical shift register 8 similarly arranged in a CCD and arranged corresponding to each vertical shift register 7 of the image pickup section 2. And temporarily accumulates and holds the signal charge.

The horizontal shift register 4 also has a CCD configuration, and transfers the electric charge accumulated in the accumulation section 3 to the output circuit 5 for each horizontal component.

FIG. 2 is a schematic sectional view of the vertical shift registers 8 adjacent to each other in the storage section 3. A channel stop region CS is formed between the vertical shift registers 8 facing the surface of the semiconductor substrate 1. ing. On the surface of the semiconductor substrate 1, a gate insulating film 9 is formed. As the gate insulating film 9, for example, an oxide film 10 of SiO ₂ formed by thermally oxidizing the surface of the Si semiconductor substrate 1 is formed, on which an SiN nitride film 11 is formed by a CVD method or the like, and further thereon. , SiO ₂ oxide film 19 is formed.

The vertical shift register 8 includes a gate insulating film 9
Above, transfer electrodes 12 and 13 made of polycrystalline semiconductor layers to which clock voltages of two phases, four phases or the like are applied are alternately arranged in the transfer direction. These transfer electrodes 12 and 13 are arranged in common across all the vertical shift registers 8 so as to be arranged across the vertical shift registers 8, and FIG.
Shows a cross section at a portion laminated via the insulating layer 24.

In the imaging section 3 as well, since the nitride film 11 for blocking the hydrogen constituting the gate insulating film 9 is formed as described above, for example, the channel stop region CS between the vertical shift registers 8 is formed. On the formation portion, a hydrogen introduction window 14 is formed in the nitride film 11 having a shielding effect on hydrogen. Then, an insulating film 15 serving as an interlayer insulating layer including the inside of the hydrogen introduction window 14 is formed. The insulating film 15 is made of, for example, PSG, BSG, or the like.
The transfer electrodes 12 and 1 may be formed by a VD method or the like.
3 can be formed by thermal oxidation.

Then, in the present invention, a hydrogen-containing film 18 containing a large amount of hydrogen, which functions as a hydrogen supply source, is formed on the interlayer insulating layer, that is, the insulating film 15. This hydrogen-containing film 18 can be constituted by a SiN film formed by a plasma CVD method.

Then, on this hydrogen-containing film 18, a metal film such as Al, or W, Ti, Mo of high melting point metal is formed.
A light-shielding film 16 is formed on the entire surface, and a light-receiving window 20 is opened on the light-receiving portion 6 shown in FIG. Further, a surface insulating layer 17 called a passivation film is formed on the entire surface.

In the solid-state imaging device having this configuration, only the insulating film 15 that transmits hydrogen is interposed on the hydrogen introduction window 14, and functions as a hydrogen supply source without an intervening layer that blocks hydrogen. Hydrogen-containing film 18 containing a large amount of hydrogen
Are arranged, hydrogen from the hydrogen-containing film 18 can be efficiently introduced into the storage section 3 through the hydrogen introduction window 14.

In the above-described solid-state imaging device shown in FIG. 2, the light shielding film 16 is formed only on the hydrogen-containing film 18, but as shown in FIG. An auxiliary light-shielding film 16S may be formed at a position other than on the hydrogen introduction window 14, that is, at a portion other than the portion facing the hydrogen introduction window 14, to enhance the light-shielding effect. Also in this case, only the insulating film 15 that transmits hydrogen is interposed on the hydrogen introduction window 14, and there is no intervening layer for shutting off hydrogen. Since the hydrogen-containing film 18 is disposed, hydrogen from the hydrogen-containing film 18 can be efficiently supplied to the hydrogen introduction window 14.
Through the target area, in this example, the storage unit 3. In FIG. 3, portions corresponding to those in FIG. 2 are denoted by the same reference numerals, and redundant description will be omitted.

The solid-state imaging device according to the present invention can be applied to not only the FIT-type solid-state imaging device but also the FT-type solid-state imaging device, and signal charges are accumulated as in such a solid-state imaging device. The present invention can be applied not only to the case where the hydrogen introduction window is formed in the storage unit but also to the solid-state imaging device having the hydrogen introduction window and the hydrogen introduction unit in a necessary part.

[0031]

As described above, according to the structure of the present invention, only the insulating film that transmits hydrogen is interposed on the hydrogen introduction window, and no hydrogen blocking layer is interposed. Since a hydrogen-containing film containing a large amount of functioning hydrogen is disposed, hydrogen from the hydrogen-containing film can be efficiently used,
The hydrogen can be introduced into the target semiconductor substrate through the hydrogen introduction window. Therefore, according to the configuration of the present invention, the interface state can be reliably reduced, and the dark current can be surely reduced.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an example of a solid-state imaging device to which the present invention is applied.

FIG. 2 is a schematic sectional view of a main part of an example of a solid-state imaging device according to the present invention.

FIG. 3 is a schematic sectional view of a main part of another example of the solid-state imaging device according to the present invention.

FIG. 4 is a schematic sectional view of a main part of a conventional solid-state imaging device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Semiconductor base, 2 ... Imaging part, 3 ... Storage part, 4 ... Horizontal shift register, 5 ... Output circuit,
6 ... light receiving section, 7 ... vertical shift register, 8 ...
.Vertical shift register, 9 ... gate insulating film, 10
... oxide film, 11 ... nitride film, 12, 13 ...
Transfer electrode, 14: hydrogen introduction window, 15: insulating film (interlayer insulating layer), 16: light shielding film, 17: surface insulating layer, 18: hydrogen-containing film containing a large amount of hydrogen , 19 ・
..Oxide film, 20 ... light receiving window, 24 ... insulating layer

Claims (4)

[Claims] 1. A semiconductor device comprising: a semiconductor substrate;
a hydrogen introduction window is formed in the SiN film, and a film containing a large amount of hydrogen including at least a position corresponding to the hydrogen introduction window on the semiconductor substrate is formed as an i. A solid-state imaging device formed between only the insulating films through which hydrogen can pass. 2. The solid-state imaging device according to claim 1, wherein the solid-state imaging device includes an imaging unit in which light-receiving units are arranged, and a storage unit that temporarily stores signal charges from the light-receiving units. The solid-state imaging device according to claim 1, wherein the solid-state imaging device is formed in a storage unit. 3. The film containing a large amount of hydrogen is plasma C
2. The solid-state imaging device according to claim 1, wherein the SiN film is formed by a VD (chemical vapor deposition) method. 4. The semiconductor device according to claim 1, wherein said insulating film through which hydrogen can pass is made of at least one of silicon oxide, phosphorus silicate glass, and boron phosphorus silicate glass.
3. The solid-state imaging device according to item 1.