Method for forming CMOS sensor without blooming effect

Details Method for forming CMOS sensor without blooming effect Method for forming CMOS sensor without blooming effect

2000-05-17

2001-06-12

Dang, Trung (Department: 2823)

Semiconductor device manufacturing: process

Making device or circuit responsive to nonelectrical signal

Responsive to electromagnetic radiation

C438S527000, C438S529000

Reexamination Certificate

active

06245592

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to the formation of a CMOS sensor, and more particularly to the formation of a CMOS sensor structure without blooming effect.
2. Description of the Prior Art
According to
FIG. 1
, a bird's beak
150
on field oxide area
140
inside the conventional complementary metal-oxide semiconductor (CMOS) sensor structure is a p-type field. Normally this p-type field owns higher concentration leading to leakage current.
For reducing leakage, the concentration of p-type field could be reduced. However, the isolation effect could be reduced as well after the concentration of p-type field is reduced. Thus, the blooming effect and the dark current will happen thus seriously destroying the general function of isolation inside the (CMOS) sensor structure.
SUMMARY OF THE INVENTION
In accordance with the present invention, a method is provided for forming a CMOS sensor that substantially reduces blooming effect.
Junction isolation including well doping, p-field implant and p+ implant can be used for the preferred embodiment. Also it can be combined with the formation process of the conventional CMOS structure.
In the preferred embodiment, the current leakage and the blooming effect can be efficiently eliminated.
In the preferred embodiment, firstly, a semiconductor substrate is provided. A first oxide layer is formed on the surface of the semiconductor substrate. A nitride layer is formed on the surface of the first oxide layer. A first photoresist layer is formed on the nitride layer as an implanting mask. Thus, first p-type ions are first implanted into the semiconductor substrate to form a p-type well region. The first photoresist layer is removed. The p-type well region is annealed. The nitride layer is removed. The first oxide layer is removed. The second oxide layer is deposited on the surface of the semiconductor substrate.
The second photoresist layer is formed on the second oxide layer as an implanting mask. The second p-type ions are second implanted into the p-type well region to form a p-type field located within the p-type well region, wherein concentration of the p-type field is higher than that of the p-type well regions. The second photoresist layer is removed. The p-type field is annealed. A third photoresist is formed on the second oxide layer as an implanting mask to cover the p-type field and p-type well region. The n-type ions are thirdly implanted into the semiconductor substrate as n-type regions around the p-type well region and are abutted the oxide layer below. The third photoresist is removed. The fourth photoresist is formed on the surface of the second oxide layer as an implanting mask to cover the p-type field and the p-type well region and portions of the n-type regions. The n+-type ions are fourth implanted into the n-type region as n+-type regions located within the n-type region. The fourth photoresist are removed. The fifth photoresist is formed on the surface of the second oxide layer as an implanting mask to cover the n-type region and the n+-type region and the p-type well region and portions of p-type field region. The p+-type ions are fifthly implanted into the p-type field as a p+-type region located within the p-type field. The n+-type region and the p+-type region are annealed to complete a semiconductor sensor device.


REFERENCES:
patent: 5118631 (1992-06-01), Dyck et al.
patent: 5371033 (1994-12-01), Lee et al.
patent: 6046069 (2000-04-01), Ishikawa et al.
patent: 6117738 (2000-09-01), Tung

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