Semiconductor device manufacturing: process – Making device or circuit responsive to nonelectrical signal – Responsive to electromagnetic radiation
Reexamination Certificate
2001-10-11
2002-11-12
Niebling, John F. (Department: 2812)
Semiconductor device manufacturing: process
Making device or circuit responsive to nonelectrical signal
Responsive to electromagnetic radiation
C438S064000, C438S069000, C438S070000, C438S636000
Reexamination Certificate
active
06479317
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The proposed invention relates to a method for integrating an anti-reflection layer and a salicide block, and more particularly to a method for simplifying fabricating process of a photodetector device.
2. Description of the Prior Art
Because of advancement of semiconductor technology and the gradually increased requirement of high-integrated devices, the importance of a device that includes several different functional elements is increased, such as the photodetector device that includes a photodiode and a transistor. However, because any specific functional element corresponds to a specific structure and a specific fabricating process, inconsistent difficulties is unavoidable during integration of different elements, especially when the structure of any element is complex, such as complementary metal-oxide semiconductor. A popular solution of the difficulty is to divide the whole device into several independent parts and then to form each part separately. For instance, a chip is divided into several parts and when any specific part is formed photoresist is used to cover other parts. Obviously, unavoidable disadvantages of this method comprise prolonged cycle time and increased wastage of interactants.
In terms of a photodetector device that is usually used by a digital camera and scanner, as the basic structural illustration shown in
FIG. 1A
, the photodetector device is formed on substrate
10
and comprises sensor area
11
and transistor area
12
. Herein, several isolations
102
are located on substrate
10
, some doped regions
101
are located in the sensor area and are separated from each other by some isolations
102
, and there are transistors made of gates
121
, sources
122
, drains
123
and spacers
124
located in the transistor area. And silicide
125
locates on gates
121
, sources
122
and drains
123
. Besides, dielectric layer
13
locates on substrate
10
and covers all forementioned structures, interconnects
14
locates on dielectric layer
13
and further connects with transistors, covering layer
15
locates on dielectric layer
13
and totally covers interconnects
14
, and color filter
16
locates on covering layer
15
and over doped regions
101
. Further, because color filter
16
is used to let only some specific light propagate to specific doped regions
101
, not only is at least one color filter located over any doped region
101
, but also there is no light restrictive structure, such as interconnect
14
located between a doped region
101
and corresponding color filter
16
.
However, in sensor area
11
, because the light that propagates through color filters
16
to doped regions
101
will be partly reflected and also owing to the fact that light does not always vertically propagate to doped regions
101
, reflected light will be distributed in all directions. Significantly, as reflected light is reflected by light restrictive interconnects
14
, it is possible that any doped region
101
is interfered with by other doped regions
101
and then crosstalk phenomena occurs. This means that any doped region
101
cannot distinguish between received light as being the light propagated from corresponding color filter
16
or the light propagated from neighboring interconnects
14
which only is noise. Therefore, as
FIG. 1B
shows, to make sure any doped region
101
is not interfered with by light that is reflected by other doped regions
101
, it is necessary to form anti-reflection layer
17
on all doped regions
101
before dielectric layer
13
is formed. As usual, available materials of anti-reflection layer
17
are TiN, Ti or TiW.
On the other hand, in transistor area
12
, importance of silicide
125
is increased as critical scale is decreased, but it is not desired to cover total transistor area
12
by silicide
125
. That is to say, it is necessary to form salicide block
18
on substrate
10
and cover the forbidden region of transistor area
12
before silicide
125
is formed, as
FIG. 1B
shows, where the forbidden region is the region in which silicide
125
is not required. In general, material of the salicide block
18
will not react with metal for forming silicide
25
, and available materials comprise tetraethyl-orthosilicate (TEOS).
According to the previous discussion, it is natural that because the material of anti-reflection layer
17
is different from the material of salicide block
18
, through doped regions
101
and isolations
102
of both areas can be formed together to simplify the fabricating process of the photodetector device, but the following processes of different areas cannot be formed at the same time until silicide
125
is formed. However, and referring to
FIG. 1B
, due to the structural difference of the two areas, some processes for constructing these different structures are always incompatible, such as the process for forming gate
121
, the process for forming silicide
125
and the process for forming color filter
16
. But due to the location of the anti-reflection layer as being similar to the location of salicide block
18
, it is possible to integrate the process for forming anti-reflection layer
17
and the process for forming silicide block
18
. Thus, overcoming current difficulties to properly integrate these processes is an important field of fabrication processes of the photodetector device.
SUMMARY OF THE INVENTION
A principal object of the present invention is to provide a method for integrating the fabricating processes of anti-reflection layer and the fabricating processes of the salicide block.
Another object of the present invention is to provide a method for forming both the anti-reflection layer and the salicide block at the same time.
A further object of the present invention is to provide a method in which the anti-reflection layer and the salicide block are made of identical materials.
Still an object of the invention is to provide a manufacturable and practical method for forming both the anti-reflection layer and the salicide block.
Objects of the invention further includes a method for forming a photodetector device, where anti-reflection layer for preventing crosstalk phenomena and a salicide block for making sure the location of silicide are formed together to simplify the fabricating process and to improve efficiency.
In short, a preferred embodiment of the present invention is a method which comprises: Providing a substrate that is divided into at least a sensor area and a transistor area, wherein the sensor area comprises a doped region and the transistor area comprises a transistor that includes a gate, a source and a drain; forming a composite layer on the substrate, wherein the composite layer at least also covers both the sensor area and the transistor area, and the composite layer increases the refractive index of light that propagates from the doped region into the composite layer; performing an etching process and a photolithography process to remove part of the composite layer and to let top of the gate, the source and the drain not being covered by the composite layer; and performing a salicide process to let top of the gate, the source and the drain being covered by a silicate.
Further, when the embodiment is applied to form a photodetector device, the following steps are included: Removing some leftover interacts of the salicide process; forming a first dielectric layer on both the composite layer and the silicide layer; forming some interconnects on the first dielectric layer, wherein interconnects locate over both transistors and isolations; forming a second dielectric layer on the first dielectric layer, wherein the second dielectric layer also covers the interconnects; and forming some color filters on the second dielectric layer, wherein the color filters locate over these doped regions.
Obviously, one main characteristic of the invention is that the composite layer is used as an anti-reflection layer of the sensor area and a salicide block of the transistor region at the same time.
Chen Chong-Yao
Lin Chen-Bin
Liu Feng-Ming
Niebling John F.
Powell Goldstein Frazer & Murphy LLP
Simkovic Viktor
United Microelectronics Corp.
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