Semiconductor device manufacturing: process – Making device or circuit responsive to nonelectrical signal – Responsive to electromagnetic radiation
Reexamination Certificate
2000-06-08
2001-10-16
Tsai, Jey (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
06303406
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The proposed invention relates to a method for integrating anti-reflection layer and salicide block, and more particularly to a method for simplifying fabricating process of a photodetector device.
2. Description of the Prior Art
Because advancement of semiconductor technology and gradually increased requirement of high-integrated device, importance of device that includes several different functional elements is increased, such as the photodetector device that includes photodiode and 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 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 forms 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 the method comprise prolonged cycle time and increased wastage of interactants.
In terms of photodetector device that usually used by digital camera and scanner, as the basic structural illustration shown in
FIG. 1A
, photodetector device is formed on substrate
10
and comprises sensor area
11
and transistor area
12
. Herein, several isolations
102
locate on substrate
10
, some doped regions
101
locate in sensor area and are separated to each other by some isolations
102
, and there are transistors made of gates
121
, sources
122
, drains
123
and spacers
124
locate in transistor area. And silicide
125
locates on gates
121
, sources
122
and drains
123
. Beside, dielectric layer
13
locates on substrate
10
and covers all forementioned structures, interconnects
14
locates on dielectric layer
13
and further connecting 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 that color filter
16
is used to let only some specific light propagate to specific doped regions
101
, not only at least one color filter locates over anyone of doped regions
101
, but also no lighttight structure, such as interconnects
14
locates between a doped region
101
and corresponding color filter
16
.
However, in sensor area
11
, because that light propagates through color filters
16
to doped regions
101
will be partly reflected and also owing to the truth 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 lighttight interconnects
14
, it is possible that any doped region
101
is interfered by other doped regions
101
and then crosstalk phenomena is happened. It means that any doped region
101
can not distinguish received light is 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 by light that is reflect 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 forbidden region of transistor area
12
before silicide
125
is formed, as
FIG. 1B
shows, where forbidden region is the region that silicide
125
is needless. In general, material of salicide block
18
will not react with metal for forming silicide
25
, and available materials comprise tetraethyl-orthosilicate (TEOS).
According to previous discussion, it is natural that because material of anti-reflection layer
17
is different to material of salicide block
18
, though doped regions
101
and isolations
102
of both areas can be formed together to simplify the fabricating process of photodetector device, but following processes of different areas can not be formed at the same time until silicide
125
is formed. However, 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 process for forming gate
121
, process for forming silicide
125
and process for forming color filter
16
. But due to location of anti-reflection layer is similar to location of salicide block
18
, it is possible to integrate process for forming anti-reflection layer
17
and process for forming salicide block
18
. Thus, how to overcome current difficulties to properly integrate these processes is an important field of fabrication processes of photodetector device.
SUMMARY OF THE INVENTION
A principal object of the present invention is to provide a method for integrating fabricating processes of anti-reflection layer and fabricating processes of salicide block.
Another object of the present invention is to provide a method for forming both anti-reflection layer and salicide block at the same time.
A further object of the present invention is to provide a method that anti-reflection layer and salicide block are made of identical materials.
Still an object of the invention is to provide a manufacturable and practical method for forming both anti-reflection layer and salicide block.
Objects of the invention further includes a method for forming photodetector device, where anti-reflection layer for preventing crosstalk phenomena and salicide block for making sure location of silicde are formed together to simplify fabricating process and improve efficiency.
In short, a preferred embodiment is a method comprises: provide 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; forms a composite layer on the substrate, herein the composite layer at least also covers both sensor area and transistor area, and the composite layer increases refractive index of light that propagate from the doped region into the composite layer; performs 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 are not covered by the composite layer; and performs a salicide process to let top of the gate, the source and the drain are covered by a silicate.
Further, when the embodiment is applied to form a photodetector device, following steps are included: removes some leftover interacts of the salicide process; forms a first dielectric layer on both composite layer and silicide layer; forms some interconnects on first dielectric layer, wherein interconnects locate over both transistors and isolations; forms a second dielectric layer on the first dielectric layer, herein second dielectric layer also covers interconnects; and forms some color filters on the second dielectric layer, herein color filters locates 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. Thus, after doped regions and transistors are all formed, it is possible to integrate fabricating processes of anti-reflection layer and fabricating processes of salicide block. Further, the composite layer is made of several alternate overlapped basic layers and refractive index of any basic layer is different to refractive indexe
Chen Chong-Yao
Lin Chen-Bin
Liu Feng-Ming
Simkovic Viktor
Tsai Jey
United Microelectronics Corp.
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