Semiconductor device manufacturing: process – Making device or circuit responsive to nonelectrical signal – Responsive to electromagnetic radiation
Reexamination Certificate
1998-12-11
2001-01-09
Bowers, Charles (Department: 2813)
Semiconductor device manufacturing: process
Making device or circuit responsive to nonelectrical signal
Responsive to electromagnetic radiation
Reexamination Certificate
active
06171882
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of manufacturing a semiconductor device. More particularly, the present invention relates to a method of manufacturing a photo diode.
2. Description of the Related Art
A photo diode based on the theorem of a P-N junction can convert light into an electrical signal. Before light energy in the form of photons strikes the photo diode, there is a depletion layer in the P-N junction and the depletion layer works as an electric field of the capacitor. The electrons in N region do not diffuse to the P region and the holes in the P region do not diffuse to the N region. When enough light strikes the photo diode, the light creates a number of electron-hole pairs. The electrons and the holes diffuse to the P-N junction. As the electrons and the holes reach the P-N junction, the electrons flow to the N region and the holes flow to the P region as a result of the effect of the inner electric field. Thus a current is induced between the P-N junction electrodes. Ideally, a photo diode in the dark is open-circuit. In other words there is no current induced by light energy while the photo diode is in the dark.
Photo diodes are utilized to produce imaging sensors which include charge-coupled device cameras (CCD cameras), PC digital cameras etc. Conventionally, the photo diode usually suffers from plasma damage. Plasma damage is caused by later process steps that include forming an inter-layer dielectric, opening a contact hole, forming a conductive layer, etc. Due to plasma damage, the dark current is uneven, the pixels of the imaging sensors leak irregularly and spots of light occur in the display image.
FIGS. 1A through 1D
are schematic, cross-sectional views of a portion of a semiconductor device showing a conventional photo diode.
First, as shown in
FIG. 1A
, a substrate
100
having a first conductive type is provided. A patterned mask layer
102
is formed on the substrate
100
. Thereafter, a LOCOS step is performed to form a field oxide
104
utilized as an isolation region on the substrate
100
exposed by the mask
102
.
Referring to
FIG. 1B
, the mask layer
102
is stripped to expose the surface of the substrate
100
and the isolation region
104
. Thereafter, an ion implantation step and an annealing step are utilized to form a doped region
110
having a second conductive type in the active area of the substrate
100
exposed by the isolation region
104
.
Next, as shown in
FIG. 1C
, an inter-layer dielectric layer
112
having a contact hole
116
is formed on the substrate
100
and the isolation region
104
, and the contact hole
116
exposes a portion of the active area of the substrate
100
. Thereafter, a conductive layer
114
is formed over the substrate
100
and fills the contact hole
116
to form a contact plug
114
.
Next, as shown in
FIG. 1D
, the conductive layer
114
is patterned to form a conductive layer
114
a.
Conventionally, plasma damage is caused in the processes of forming the inter-layer dielectric layer, opening the contact hole, forming the conductive layer, etc. Furthermore, the plasma damage leads to uneven dark current, irregular pixel leakage of the imaging sensor, and the spots of light which occur on the display image.
In light of the foregoing, there is a need to provide an improved structure of a photo diode and a method of manufacturing an improved photo diode.
SUMMARY OF THE INVENTION
Accordingly, the present invention is to provide a structure of a photo diode and a method of manufacturing a photo diode. A protective layer can prevent the plasma damage, therefore the weaknesses seen in the prior art such as uneven dark current and irregular pixel leakage of the imaging sensor induced by the plasma damage can be overcome.
To achieve these and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, the invention provides a method of manufacturing a photo diode. The method comprises the step of providing a substrate having an isolation region. A doped region is formed in the substrate by performing an ion implantation step and an annealing step. Next, a protective layer utilized to prevent the plasma damage is formed on the substrate and the isolation region and an inter-layer dielectric layer is formed on the protective layer. Thereafter, a contact hole is formed to expose a portion of the doped region by patterning the inter-layer dielectric layer and the protective layer, and a contact plug is formed by filling the contact hole with a conductive material.
It is to be understood that both the foregoing general description and the following detailed description are exemplary, and are intended to provide further explanation of the invention as claimed.
REFERENCES:
patent: 5215928 (1993-06-01), Hirai
patent: 03094478 (1991-04-01), None
Ghandhi, Sorab; The Theory and Practice of Microelectronics; John Wiley and Sons, pp. 180-184 (no month available), 1968.*
Chien Cheng-Hung
Hsu Jen-Yao
Pan Jui-Hsiang
Blakely & Sokoloff, Taylor & Zafman
Bowers Charles
Christianson Keith
United Microelectronics Corp.
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