JP3092271B2 - Method for manufacturing solid-state imaging device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a solid-state imaging device, and more particularly, to a technique for preventing the influence of impurities on a charge transfer region and a sensor region.

[0002]

2. Description of the Related Art A conventional method of manufacturing a solid-state imaging device of this type will be described with reference to an example shown in FIG. First, a gate electrode 3 made of polysilicon is patterned on a portion of the silicon substrate 1 to be a charge transfer region via a gate insulating film 2, and then an insulating film 4 is formed on the entire surface. Next, the insulating film 4
After patterning the polysilicon layer 5 serving as a shift electrode thereon, an oxide film 6 is formed on the surface of the polysilicon layer 5. Then, a non-doped normal pressure SiO ₂ film 7 is deposited on the entire surface of the processed semiconductor substrate by using a normal pressure CVD method of 760 Torr, and thereafter, PSG (phosphosilicate glass) or the like is formed on the normal pressure SiO ₂ film 7. Is deposited by an AP-CVD method, and a light shielding Al electrode 9 is patterned at a predetermined position (above the charge transfer region) on the reflow film 8.

[0003] Such a method is based on a technical idea of minimizing the influence of impurities on the base by covering the entire surface with a non-doped normal pressure SiO ₂ film 7.

[0004]

However, in such a conventional method for manufacturing a solid-state imaging device, there is a problem that step coverage is deteriorated with miniaturization. In addition, it is difficult to form a SiO ₂ film having a thickness of 1000 ° or less by a normal pressure CVD method, and the controllability of such a film thickness or film quality becomes extremely poor with miniaturization. Have the above problem.

[0005] As Therefore, as shown in FIG. 9, SiO ₂
The thickness of the film 7 cannot be reduced, the distance between the edge of the light-shielding Al film 9 formed above the charge transfer region and the silicon substrate 1 is large, and light to be incident only on the sensor region There is a problem that the smear characteristic deteriorates by invading the charge transfer region.

Further, even if the non-doped SiO ₂ film 7 is formed by the normal pressure CVD method, diffusion of impurities such as Na ⁺ from the upper reflow film 8 cannot be prevented. Diffuse impurities cause image defects.

SUMMARY OF THE INVENTION The present invention has been made in view of such conventional problems, and prevents deterioration of characteristics due to miniaturization, facilitates process management, and reduces image defects. An object of the present invention is to provide a method for manufacturing a solid-state imaging device, which is reduced.

[0008]

Accordingly, the present invention provides a process for forming an insulating film on the surface of a semiconductor substrate, a process for patterning a gate electrode on the insulating film, and a process for forming an insulating film on the surface of the gate electrode. a step of, forming a SiO ₂ film by using a whole surface pressure CVD, the SiO ₂ film, a reflow film, the charge transfer region of said semiconductor substrate
And forming a light shielding electrode located above .

[0009]

By forming an SiO ₂ film above the charge transfer region and above the sensor region by using a low pressure CVD method, impurities (for example, Na ⁺ ) from the reflow film as the upper layer are removed from the above two regions and the gate electrode. Has the effect of preventing diffusion to the like. In addition, since the reduced-pressure SiO ₂ film can be controlled to have a small thickness, the distance between the edge of the light-shielding electrode and the semiconductor substrate can be reduced, and light incident on the charge transfer region, which causes smear, can be reduced. Has the effect of preventing.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of a method for manufacturing a solid-state imaging device according to the present invention will be described below with reference to the embodiments shown in the drawings.

First, as shown in FIG.
1, an insulating film 12 serving as a gate insulating film is formed, a polysilicon film is deposited on the gate insulating film 12 and patterned, and a polysilicon gate (gate) is formed at a position to be a charge transfer region in circuit design. An electrode 13 is formed.

Next, as shown in FIG. 2, after an inter-electrode insulating film 14 is formed on the surface of the polysilicon gate 13, predetermined impurities are implanted into the silicon substrate 11 to form a charge transfer region 11A and a sensor region 11B. To form

Next, as shown in FIG. 3, a shift electrode 15 is formed by depositing and patterning a polysilicon film. Then, an insulating film 16 is formed on the surface of the shift electrode 15.

Then, as shown in FIG. 5, L is formed on the entire surface of the silicon substrate thus processed by the low pressure CVD method.
A P-SiO ₂ film 17 is deposited thinly (1000 ° or less).

The conditions for forming the LP-SiO ₂ film 17 are, for example, as follows.

(LP-SiO ₂ film formation conditions 1) Gas and flow rate thereof SiH ₄ ··· 1000 _SCCM N ₂ O ··· 1000 to 2000 _SCCM · Pressure ··· 0.2 to 0.8 Torr · Temperature ··· 800 ° C. (LP -SiO ₂ film deposition condition 2) ○ gas and its flow rate _{SiH 2 Cl 2 ... 1000 SCCM N} 2 O ... 1000~2000 SCCM ○ pressure ... 0.2~0.8Torr ○ temperature ... 800 ° C. Next, FIG. 6 as shown in, P on the LP-SiO ₂ film 17
A reflow film 18 made of SG is deposited by a CVD method,
A heat treatment is applied to reflow to smooth the steps.
Thereafter, an aluminum film is deposited on the reflow film 18,
By patterning, the light shielding Al electrode 19 is formed only above the charge transfer region 11A.

FIG. 7 is a plan view of the solid-state imaging device, and FIG. 6 is a sectional view taken along line AA of FIG. FIG. 8 is a sectional view taken along the line BB of FIG.

The solid-state imaging device manufactured according to the above-described embodiment has a structure in which the gate electrode and the like protrude from the silicon substrate 11, but since the LP-SiO ₂ film 17 can be set to a small thickness, the reflow film 18 The distance between the peripheral portion of the light-shielding Al electrode 19 formed through the silicon substrate 11 and the silicon substrate 11 can be reduced by about the length of the thinned LP-SiO ₂ film 17. Therefore, in the present embodiment, the charge transfer region 11A is compared with a film formed by the normal pressure CVD method as in the conventional method.
Thus, the amount of light incident on the substrate can be significantly reduced, and the smear characteristics can be improved.

The film quality of LP-SiO ₂ is normal pressure CV.
It is superior to the SiO ₂ film formed by the method D and has an effect of preventing contamination such as Na ⁺ from the reflow film side from diffusing to the lower layer side.

Although the embodiment has been described above, the present invention is not limited to this, and can be applied to solid-state imaging devices having various structures. Needless to say, the film formation conditions of LP-SiO ₂ can be appropriately changed to conditions other than those described above. For example, it is possible to form a film at a temperature of about 700 ° C. using etraethoxysilane, and silane (SiH ₄ ) And oxygen (O ₂ ) as a film forming gas,
It is also possible to carry out at a temperature of 0 ° C.

Further, the present invention is applicable even if the structure of the sensor region and the charge transfer region formed on the silicon substrate and the transfer system are changed.

[0022]

As is clear from the above description, according to the present invention, there is an effect of preventing deterioration of characteristics due to miniaturization of a solid-state imaging device.

Further, since it is easy to form a thin SiO ₂ film by the low pressure CVD method in the process, the production management is simplified and the controllability is improved.

In particular, according to the present invention, it is possible to prevent light from being incident on the charge transfer region, and there is an effect of reducing image defects such as smear.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a process of an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing the steps of the embodiment of the present invention.

FIG. 3 is a cross-sectional view showing the steps of the embodiment of the present invention.

FIG. 4 is a cross-sectional view showing the steps of the embodiment of the present invention.

FIG. 5 is a cross-sectional view showing the steps of the embodiment of the present invention.

FIG. 6 is a sectional view (A in FIG. 7) showing a process of the embodiment of the present invention.
-A sectional view).

FIG. 7 is a plan view of a solid-state imaging device formed according to an embodiment of the present invention.

FIG. 8 is a sectional view taken along line BB of FIG. 7;

FIG. 9 is a sectional view of a conventional example.

[Explanation of symbols]

11 silicon substrate, 12 gate insulating film, 13 polysilicon gate, 14 inter-electrode insulating film, 17 LP-S
iO ₂ film, 18: reflow film, 19: light shielding Al electrode.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01L 27/148 H01L 27/14

Claims (1)

(57) [Claims] A step of forming an insulating film on the surface of the semiconductor substrate; a step of patterning a gate electrode on the insulating film; a step of forming an insulating film on the surface of the gate electrode; Forming a SiO ₂ film by using a reflow film on the SiO ₂ film;
A light shielding electrode located above the charge transfer region is formed
And a method of manufacturing a solid-state imaging device.