JP2002208688A - Solid-state image pickup device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce failures in the breakdown voltage between a light-shielding film and a substrate, and at the same time, to reduce smearing. SOLUTION: This solid-state image pickup device has a light-receiving section that is formed near the surface of a semiconductor substrate for carrying out photoelectric conversion; a charge transfer section that is formed near the surface of a semiconductor substrate being different from the light-receiving section and at the same time, reads a signal charge from the light-receiving section for transferring; a transfer gate electrode section that is formed on the charge transfer section via a gate insulating film; a light-shielding section that is formed at the upper section of the transfer gate electrode section; and an insulating film, that is formed between the transfer gate electrode and light- shielding sections directly above the light-shielding section or directly above and below the light-shielding section. In the light-shielding section, a s metal film mainly made of Ti and high-melting-point metal film are laminated in this order.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid-state imaging device, and more particularly to a configuration of a solid-state imaging device capable of reducing smear.

[0002]

2. Description of the Related Art In recent years, the size of solid-state imaging devices (hereinafter, also referred to as CCDs) has been reduced, and the number of pixels of digital cameras capable of inputting images to personal computers and the like has been increased. FIG. 4 shows a configuration of an interline transfer type CCD as an example of a solid-state imaging device. In the figure, the image pickup portion of the CCD has two pixels in the vertical and horizontal directions.
A light receiving unit 1 composed of a plurality of photoelectric conversion elements arranged in a dimension and accumulating signal charges according to the amount of incident light, and the signal charges read out from these light receiving units 1 for each vertical column in a vertical direction (on the paper surface). A vertical shift register (vertical transfer unit) 2 for transferring the data in a downward direction is formed. An oxide film for element isolation is formed about 1 μm around the vertical shift register. And a wiring region of the same.

The signal charges of all pixels photoelectrically converted by the light receiving unit 1 are instantaneously read to the vertical shift register 2 for each vertical column during a part of the vertical blanking period. The signal charges transferred to the vertical shift register 2 are sequentially transferred to the horizontal shift register (horizontal transfer unit) 3 for each scanning line during the horizontal blanking period.
Moved to

The signal charges for one scanning line are sequentially transferred in the horizontal direction by the horizontal shift register 3. At the end of the horizontal shift register 3, an FDA (Floating Diffusion)
An output circuit unit 4 including an amplifier is provided. The output circuit unit 4 converts signal charges obtained by photoelectric conversion in the light receiving unit 1 into a voltage and outputs the voltage. Although not shown, a light-shielding film is provided in a vertical transfer portion, and the vertical shift register and the horizontal shift register constitute a charge transfer section. In FIG. 4, a wiring region 5 is formed around an active region such as a light receiving section.

In such a solid-state imaging device, in recent years, it has been required to reduce imaging defects particularly at the time of high luminance, and one of them is to reduce smear. Smear refers to a phenomenon in which, when strong light is applied to a solid-state imaging device, the incident light is caused by the light reaching the charge transfer section through a light-shielding film, and appears as a band-like imaging defect on a screen. In particular, in order to prevent light from leaking to the charge transfer section, a high melting point metal material or a silicide material thereof is generally used as a material of the light shielding film. For example, W, W / Si, Mo, Mo / Si
Etc. are used.

FIGS. 5 and 6 show a manufacturing process of a conventional solid-state imaging device. FIG. 7 is a cross-sectional view of the wiring region around the light receiving unit and the charge transfer region shown in FIG. 5 and 6 are cross-sectional views of the light receiving unit and the vertical shift register (vertical transfer unit) 2.

As shown in FIG. 5A, first, a predetermined shape is formed on an N-type silicon substrate 11 by photolithography, and a P ⁻ layer 12 is formed to a depth of about 5 μm by ion implantation and heat treatment. , The gate insulating film 16 having a thickness of 3
It is formed to about 5 nm. Next, using a predetermined mask, boron ions (B ⁺ ) are implanted below the position to become the vertical transfer section 14 by using a predetermined mask, and the P layer 13 is formed.
Is formed, and phosphorus is implanted using the same mask to form the vertical transfer section 14. After that, a channel stop portion 15 for pixel separation is formed by implanting boron ions into a part of the P ⁻ layer adjacent to the vertical transfer portion. Then, polysilicon to be a gate electrode is formed on these structures by LP-CVD.
A film is formed to a thickness of about 0 nm, and a first layer of vertical transfer gate electrode 17 is formed by predetermined photoetching.

Next, as shown in FIG. 5B, after an interlayer oxide film is formed on the first layer vertical transfer gate electrode 17 by thermal oxidation or the like, the second polysilicon film 18 is formed by LP-
A film having a thickness of 350 nm is formed by a CVD method or the like. Next, in the same manner as when the first-layer gate electrode 17 was formed, the second-layer vertical transfer gate electrode 18 was patterned by lithography and etched to form a gate electrode having a predetermined shape. Thereafter, a silicon oxide film 19 is formed on the second-layer vertical transfer gate electrode 18 using a CVD method or the like.

[0009] Next, as shown in FIG.
In order to form the photoelectric conversion region 20 to be formed near the surface of the P ⁻ layer, a predetermined patterning is performed after applying a resist, and phosphorus is injected into the P ⁻ layer. And then
High-concentration boron is implanted into the surface of the photoelectric conversion region 20 to form a high-concentration P ⁺ layer 21 (FIG. 5C).

Generally, a light shielding film (such as tungsten w) 23
Has poor adhesion to the insulating film (silicon oxide film 19). Then, before forming the light shielding film 23, the TiN film 22 is formed as a base of the light shielding film 23 by the PVD method (FIG. 5D). Next, the light-shielding film 23 is
A film having a thickness of about 0 to 200 nm is formed (FIG. 6E). At this time,
In the wiring region 5, as shown in FIG.
1 has an oxide film 19, a TiN film 22, and a light-shielding film 23 formed in this order.

Next, after patterning by lithography, the TiN film 22 and the light shielding film 23 on the photoelectric conversion region 20 are formed so that the pattern of the charge transfer portion and the light receiving portion 1 as shown in FIG. It is removed by etching (FIG. 6 (f)). When the light-shielding film 23 is processed in this manner, the wiring regions 5 having the same material as the light-shielding film 23 are simultaneously provided with the wiring patterns (reference numerals 23 'and 2 in FIG. 7B).
3 '') is formed. Thereafter, an insulating film 25 is formed on the entire structure by a CVD method using thermal decomposition.
The insulating film 25 is reflowed at a high temperature of about 950 ° C. Then, if a contact hole is formed and a final wiring process is performed, the solid-state imaging device is completed (FIGS. 6G and 7).
(C)).

[0012]

In such a conventional solid-state imaging device, in order to reduce smear and reduce the resistance of the wiring pattern, the light shielding film 23 and the wiring material have good light shielding properties and specific resistance. (W) film is used. In order to improve the adhesion between the W film 23 and the silicon oxide film 19, a TiN (titanium nitride) film 22 is formed.
Is used as a base of the light-shielding film 23. In the step of forming the insulating film 25, the light shielding film 23 is formed.
Of the silicon oxide film 1
9, an insulating film 25 having high temperature and reflow property is formed thereon by a CVD method by thermal decomposition, and thermal reflow is performed at a high temperature of 950 ° C.

However, in general, when a heat treatment is performed at a high temperature after forming an alloy containing Ti and Ti, such as the TiN film 22, on the silicon oxide film 19, the Ti is deposited in the silicon oxide film 19. It is known that they diffuse to form a conductive film (TiO ₂ ).

When such a conductive film is formed, the insulating property is impaired. Therefore, Ti and an alloy containing Ti (Ti
After forming the film N), it is not preferable to perform a heat treatment at a high temperature.

For example, in the wiring region 5, the unreacted Ti in the TiN diffuses into the silicon oxide film 19 due to the heat treatment at 950 ° C. of the Ti-based alloy. There is a problem that insulation failure occurs. Further, also in the region of the light shielding film 23, there is a problem that unreacted Ti diffuses into the silicon oxide film 19, resulting in insulation failure between the silicon substrate 11 and the light shielding film.

In general, the voltage of the light-shielding film 23 and the substrate 11 is fixed to GND by DC. However, since the substrate is affected by induction by application of a pulse voltage or a shutter voltage to the vertical transfer gate electrode 17, it is transiently applied. The occurrence of a potential difference between the light-shielding film 23 and the silicon substrate 11 causes the above-described insulation failure. Therefore, when TiN is formed before the formation of the wiring and the light-shielding film as in the related art, unreacted Ti in the TiN alloy diffuses into the insulating film 19 due to the subsequent high-temperature heat treatment. At the same time, the leakage current locally increases, causing a problem of poor withstand voltage.

Accordingly, the present invention has been made in view of the above circumstances, and has a structure in which a leak electrode between a light-shielding film and a substrate is reduced, a breakdown voltage defect is reduced, and smear is reduced. To provide a solid-state imaging device having:

[0018]

According to the present invention, there is provided a light receiving portion for performing photoelectric conversion formed near the surface of a semiconductor substrate, and a signal receiving portion formed near the surface of the semiconductor substrate different from the light receiving portion. A charge transfer portion for reading and transferring charges, a transfer gate electrode portion formed on the charge transfer portion via a gate insulating film, a light shielding portion formed above the transfer gate electrode portion, and a transfer gate. An insulating film formed by using a plasma CVD method between the electrode portion and the light-shielding portion, directly above the light-shielding portion, or directly above and directly below the light-shielding portion, wherein the light-shielding portion is a metal film mainly composed of Ti. An object of the present invention is to provide a solid-state imaging device having a structure in which refractory metal films are stacked in this order.

A method for manufacturing a solid-state imaging device in which a charge transfer portion, a gate insulating film, a transfer gate electrode, and a light-shielding portion are formed in this order on a semiconductor substrate. A first insulating film is formed on the gate electrode, and a light-shielding portion formed by stacking a metal film containing titanium as a main component and a light-shielding film made of a light-shielding material in this order on the first insulating film. And patterning the light-shielding portion so that the light-shielding portion covers at least an upper portion of the charge transfer portion. A second insulating film is formed on the light-shielding film by using a plasma CVD method. It is another object of the present invention to provide a method for manufacturing a solid-state imaging device, comprising a step of forming a third insulating film containing a predetermined impurity thereon and then reflowing the third insulating film.

This makes it possible to reduce the withstand voltage failure between the semiconductor substrate and the light-shielding film of the solid-state imaging device, and to reduce the occurrence of smear.

[0021]

In the present invention, a material having a light-shielding property is used for the refractory metal film. For example, tungsten, molybdenum, or a silicide compound thereof can be used. As the metal film mainly composed of Ti, for example, TiN can be used. Further, a predetermined wiring pattern is further provided on the semiconductor substrate, and the material of this wiring pattern may be the same as that of the light shielding portion.

Further, according to the present invention, plasma CVD
The second insulating film formed by the method is formed immediately above the high melting point metal film after patterning the light shielding portion.

In the present invention, an insulating film may be formed directly above and below the light shielding portion by using a plasma CVD method. That is, according to the present invention, a charge transfer portion, a gate insulating film, a transfer gate electrode, and a light shielding portion composed of a metal film containing titanium as a main component and a light shielding film made of a material having a light shielding property are formed in this order on a semiconductor substrate. A method for manufacturing a solid-state imaging device, comprising: forming a transfer gate electrode, forming a first insulating film on the transfer gate electrode, and forming a second insulating film of P-CVD on the first insulating film. After forming the film, a metal film containing titanium as a main component is formed, a refractory metal film made of a material having a light-shielding property is formed immediately above the film, and a plasma CVD method is further applied on the light-shielding film. Forming a third insulating film, patterning the light-shielding portion so that the light-shielding portion covers at least an upper portion of the charge transfer portion, and forming a fourth insulating film containing a predetermined impurity on the entire structure. Later, this fourth insulating film is To provide a method of manufacturing a solid-state imaging device which comprises a row to process.

Here, the insulating film formed by using the plasma CVD method is composed of a SiO ₂ , SiO or SiN film.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. It should be noted that the present invention is not limited by this. 1 and 2 are cross-sectional views of a manufacturing process in the vicinity of a light receiving section 1 and a vertical transfer section 2 showing an embodiment of the present invention. FIG. 3 is a sectional view of the wiring region 5. In FIG. 1A, first, on an N-type silicon substrate 51,
The P ⁻ layer 52 is formed to a depth of about 5 μm using photolithography, ion implantation, and heat treatment.

Next, by photolithography, after resist coating with a mask having a predetermined pattern, below the region that becomes the vertical transfer unit 54 P ^- layers by implanting boron ions (B ^+), of about 1μm A P layer 53 having a thickness is formed. Thereafter, a vertical transfer section 54 of about 0.5 μm is formed on the P layer 53 by ion implantation of phosphorus or arsenic using the same mask. Thereafter, the resist of the mask is removed.

Next, a predetermined patterning of the resist is performed, and a channel stop portion 55 (pixel separation P ⁺ layer) 55 for element isolation is formed on a part of the P ⁻ layer adjacent to the vertical transfer portion 54 with boron ions. It is formed by ion implantation.

Next, a gate insulating film 56 is formed on these structures by thermal oxidation or CVD so as to have a thickness of, for example, about 35 nm. Further, a first polysilicon layer (1st PolySi) to be the vertical transfer gate electrode 57 is further deposited thereon by 350 nm by LP-CVD.
It is formed with a thickness of about m. Then, after patterning the resist by lithography, the first-layer vertical transfer gate 57 is formed by etching.
(A)). The first layer of polysilicon has a prescribed resistivity (for example, 30 Ω / □), and therefore, a material containing phosphine or phosphorus chloride is used, or an impurity (such as P + (phosphorus)) is added by ion implantation. Is preferably performed.

Thereafter, an interlayer oxide film 59 is formed on the first layer vertical transfer gate (polysilicon) 57 by thermal oxidation or CVD to a thickness of about 150 nm. Next, on the entire structure, a second polysilicon (2nd polysilicon) to be the second-layer vertical transfer gate electrode 58 is formed.
lySi) is deposited by LP-CVD with a thickness of about 350 nm.

Thereafter, the first-layer gate electrode 57 is formed.
In the same manner as the formation of the gate electrode, the second-layer vertical transfer gate electrode 58 is patterned by lithography and etched to form a gate electrode having a predetermined shape. A silicon oxide film 59 is formed on the second-layer vertical transfer gate electrode by thermal oxidation or CVD (FIG. 1B).

Next, as shown in FIG. 1C, a photoelectric conversion region 60 to be the light receiving section 1 is formed by lithography technology.
In order to open only the openings, a predetermined patterning is performed after applying a resist. Then, phosphorus ions are implanted into the P ⁻ layer in the opening to form a photoelectric conversion region 60 having a thickness of about 1 μm.
To form

Thereafter, in order to form a high-concentration P ⁺ layer 61 as an inversion layer on the surface of the photoelectric conversion region 60, P-type ions such as boron ions are implanted (FIG. 1C). This high concentration P ⁺ layer is formed with a thickness of about 0.3 μm.

Thereafter, an insulating film (for example, an oxide film such as SiO ₂ ) 70 is formed on the first and second vertical transfer gate electrodes and the light receiving portion 1 by a CVD method so as to have a thickness of about 100 nm. In order to form a TiN film on the insulating film 70, a Ti film 62 is sputtered above the above structure in a N ₂ atmosphere under a condition of 8 W by a reactive sputtering method. At this time, the TiN film 62 is
A film having a thickness of about nm is formed on the entire structure (see FIG. 1).
(D)). Note that the TiN film 62 can be formed by the MO-CVD method, which is characterized by excellent base step coverage.

Thereafter, a W film 6 which is a wiring material and a light shielding film is formed.
3 is formed on the entire structure by a CVD method. Under conditions of 80 Torr and 475 ° C., WF6 and H
By reacting the two gases, 100 to 200 nm
A W film is formed with a thickness of about (FIG. 2E). At this time, in the wiring region 5, as shown in FIG. 3A, on the silicon substrate 51, on the oxide film 56 for element isolation, on the TiN film 62,
It has a structure in which W films 63 are stacked in this order.

Next, a pixel opening 69 is formed so that light is incident only on the photoelectric conversion region 60 serving as the light receiving section 1. Here, after applying the resist, the resist is patterned by a lithography technique using a predetermined mask so that the pattern of the light receiving section 1 as shown in FIG. TiN
The film 62 and the W film 63 are removed (FIG. 2F). At this time, the wiring pattern (FIG. 3) is also formed in the wiring region 5 by performing predetermined patterning and etching.
(B) 63 ', 63'') are also formed.

Next, a plasma oxide film 64 which is a feature of the present invention is formed on the above structure by a plasma CVD method. The plasma oxide film 64 is for preventing a reaction between the insulating film 65 having a reflow property formed later and the light shielding film 63.

The plasma oxide film 64 is made of TEOS / O2:
A material composed of 500/350 SCCM is converted to a power of 460
By introducing into a plasma atmosphere under the conditions of W, 60 sec and 400 ° C., 100
A film having a thickness of about 400 nm is formed (FIGS. 2G and 3C). In this embodiment, a so-called TEOS-based oxide film is used as the plasma insulating film 64, but any other insulating film (for example, SiN) may be used as long as it is an insulating film containing hydrogen ions formed in a plasma atmosphere. It does not matter.

As described above, when the insulating film 64 is formed by the plasma CVD, hydrogen atoms contained in the insulating film penetrate the W film 63 and reach the TiN film 62 immediately below the W film, and the TiN It is known to react with unreacted Ti atoms in the film. That is, since unreacted Ti atoms are trapped by being combined with hydrogen atoms, unreacted Ti can enter the silicon oxide film 59 of the vertical transfer portion 2 and the wiring region 5 even if a high-temperature heat treatment is performed later. Can be prevented. Therefore, occurrence of insulation failure can be reduced as compared with the conventional case.

Next, on the entire structure having the plasma oxide film 64 formed thereon, an insulating film 65 containing impurities such as boron and phosphorus having a reflow property is formed by CVD method for 600 to 9 times.
It is formed to a thickness of about 00 nm. Thereafter, a heat treatment is performed at a high temperature of, for example, 950 ° C. for about 30 minutes to reflow the insulating film 65 (FIGS. 2H and 3D).

Then, a contact hole for wiring is formed in a predetermined region, a wiring material (for example, Al—Cu) is formed for electric wiring of each part, and a predetermined shape is formed by photolithography and etching. If the final wiring step for processing is performed, the solid-state imaging device of the present invention is completed.

In this embodiment, the case where the insulating film 64 is formed by plasma CVD after the formation of the light shielding film 63 has been described, but the plasma is formed above and below the light shielding part so that the TiN film 62 and the light shielding film 63 are sandwiched. Insulating film 64
May be formed.

In the case of such a structure, similarly, unreacted Ti atoms are trapped by hydrogen atoms, so that unreacted Ti atoms are trapped.
The atoms do not invade the silicon oxide film 59, and the occurrence of insulation failure can be reduced. Furthermore, although the tungsten W of the high melting point metal is used as the light shielding film 63, the present invention is not limited to this, and a silicide compound of tungsten W or a silicide compound of Mo or Mo may be used.

[0043]

According to the solid-state imaging device of the present invention,
An insulating film formed using a plasma CVD method is provided between the gate electrode portion and the light-shielding portion made of a high-melting point metal film and a metal film mainly composed of Ti, directly above the light-shielding portion, or directly above and below the light-shielding portion. Therefore, it is possible to prevent unreacted Ti atoms in the metal film mainly composed of Ti from invading the insulating film formed under the light-shielding portion, and to reduce the breakdown voltage between the light-shielding film and the substrate and between the wiring patterns. Thus, the generation of smear can be prevented.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a method of manufacturing a charge transfer section and a light receiving section of a solid-state imaging device according to the present invention.

FIG. 2 is an explanatory diagram of a method of manufacturing a charge transfer section and a light receiving section of the solid-state imaging device of the present invention.

FIG. 3 is an explanatory diagram of a method for manufacturing a wiring region of the solid-state imaging device according to the present invention.

FIG. 4 is a general schematic block diagram of a solid-state imaging device.

FIG. 5 is an explanatory diagram of a method for manufacturing a charge transfer section and a light receiving section of a conventional solid-state imaging device.

FIG. 6 is an explanatory diagram of a method for manufacturing a charge transfer section and a light receiving section of a conventional solid-state imaging device.

FIG. 7 is an explanatory diagram of a method for manufacturing a wiring region of a conventional solid-state imaging device.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 light receiving section 2 vertical transfer section 3 horizontal transfer section 4 output circuit section 5 wiring area 51 silicon substrate 52 P ⁻ layer 53 P layer 54 vertical transfer section 55 channel stop section (pixel separation P ⁺ layer) 56 gate insulating film 57 first Vertical transfer gate electrode 58 second vertical transfer gate electrode 59 silicon oxide film 60 photoelectric conversion region 61 high-concentration P ⁺ region 62 TiN film 63 light-shielding film 64 plasma oxide film 65 insulating film 70 insulating film

Claims (8)

[Claims] 1. A light receiving unit for performing photoelectric conversion formed near a surface of a semiconductor substrate, and a charge transfer formed near a surface of a semiconductor substrate different from the light receiving unit and for reading and transferring signal charges from the light receiving unit. A transfer gate electrode portion formed on the charge transfer portion via a gate insulating film; a light shielding portion formed above the transfer gate electrode portion; and a portion between the transfer gate electrode portion and the light shielding portion. An insulating film formed by a plasma CVD method immediately above the light-shielding portion, or directly above and directly below the light-shielding portion, and the light-shielding portion is formed by laminating a metal film mainly composed of Ti and a high melting point metal film in this order. A solid-state imaging device characterized by having a modified structure. 2. The solid-state imaging device according to claim 1, wherein said high melting point metal film is made of tungsten, molybdenum, or a silicide compound thereof. 3. The solid-state imaging device according to claim 1, further comprising a predetermined wiring pattern on the semiconductor substrate, wherein a material of the wiring pattern is the same as a material of the light shielding portion. 4. The method according to claim 1, wherein the metal film containing titanium as a main component is
The solid-state imaging device according to claim 1, wherein the solid-state imaging device is an iN film. 5. A method for manufacturing a solid-state imaging device in which a charge transfer section, a gate insulating film, a transfer gate electrode, and a light-shielding section are formed in this order on a semiconductor substrate, wherein the transfer is performed after forming the transfer gate electrode. A first insulating film is formed on a gate electrode, and a light-shielding film is formed by stacking a metal film containing titanium as a main component and a refractory metal film made of a light-shielding material in this order on the first insulating film. A light-shielding portion is patterned so that the light-shielding portion covers at least an upper portion of the charge transfer portion.
A second insulating film is formed using a method, and over the entire structure,
A method for manufacturing a solid-state imaging device, comprising: after forming a third insulating film containing a predetermined impurity, reflowing the third insulating film. 6. A semiconductor device formed using the plasma CVD method.
Insulating film is made of SiO _Two, SiO or SiN film
6. The method for manufacturing a solid-state imaging device according to claim 5, wherein
Law. 7. The refractory metal film made of a material having a light-shielding property is made of tungsten, molybdenum, or a silicide compound thereof.
The manufacturing method of any of the solid-state imaging devices. 8. The method according to claim 1, wherein the metal film containing titanium as a main component is
8. The method for manufacturing a solid-state imaging device according to claim 5, wherein the device is an iN film.