Semiconductor device manufacturing: process – Making field effect device having pair of active regions... – Having insulated gate
Reexamination Certificate
2001-03-22
2002-12-03
Niebling, John F. (Department: 2812)
Semiconductor device manufacturing: process
Making field effect device having pair of active regions...
Having insulated gate
C438S291000, C438S299000, C438S302000, C438S305000
Reexamination Certificate
active
06489206
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for forming a raised source/drain semiconductor device, and more particularly to a method for forming a local-halo semiconductor device with raised source/drain.
2. Description of the Prior Art
As semiconductor devices are scaled to smaller dimensions, generally in the sub-0.1 &mgr;m region, it is highly desirable and generally necessary to fabricate such devices with source/drain shallow junction and a controllable halo implant region adjacent to the source/drain shallow junction to reduce short channel effects, such as subsurface punchthrough and hot carrier effect. The halo implant region is a doped implanted region, which is oppositely doped to the shallow junction region. However, when a silicide is formed on the source/drain region, the silicide easily contacts with the shallow junction to make junction leakage. Therefore, an approach to resolve the leakage problem is to use raised source/drain. Since the raised source/drain is formed upward above the substrate, the silicide could not easily contact with the shallow junction, and then the junction leakage can be reduced.
FIGS. 1A
to
1
C shows various steps for forming a conventional N-channel metal-oxide-semiconductor (MOS) device with raised source/drain. The conventional method comprises the following steps. Firstly, referring to
FIG. 1A
, a P type semiconductor substrate
100
is provided. A plurality of shallow trench isolation
101
is formed in the substrate
100
. Then, a gate oxide
102
and a gate electrode
103
are sequentially formed between each pair of the shallow trench isolation
101
on the substrate
100
. Subsequently, placing an implant mask on the substrate
100
and by way of ion implantation, to form an N type lightly doped drain region
104
between the gate electrode
103
and each of the pair of shallow trench isolation
101
in the substrate
100
. And then, performing halo implantation to form a halo implant region
105
with P type conductivity surrounding each of the lightly doped drain region
104
.
Secondly, referring to
FIG. 1B
, forming a conformal silicon dioxide layer
106
on the gate electrode
103
and then forming a silicon nitride layer
107
on the conformal silicon dioxide layer
106
. The conformal silicon dioxide layer
106
is anisotropically etched by way of reactive ion etch method to form a pair of first sidewall spacers
106
on opposite sides of the gate electrode
103
and a pair of second sidewall spacers
107
on the opposite sides of the first sidewall spacer
106
.
Finally, referring to
FIG. 1C
, forming a raised source/drain
108
upward on each of the pair of the lightly doped drain region
104
. However, there are some disadvantages existing in this conventional method. One is the halo implant region
105
surrounding the lightly doped drain region
104
increases the junction capacitance, resulting in a slower operation speed for the MOS device. The other is the misalignment of the ion implant mask can cause changeable LDD/halo implant regions.
Accordingly, it is desirable to provide a method for forming a local halo MOS device with raised source/drain to reduce the junction capacitance and also overcome the drawbacks of the conventional method.
SUMMARY OF THE INVENTION
It is an objective of the present invention to provide a method for forming a self-aligned local-halo metal-oxide-semiconductor (MOS) device with raised source/drain, in which a gate electrode and the raised source/drain act as the self-aligned masks, a LDD/halo implantation is performed to form a local LDD/halo diffusion region therebetween in the substrate. The local LDD/halo diffusion region reduces the junction capacitance. Thereby, the operation speed of the MOS device is facilitated.
Another objective of the present invention is to provide a method for forming a self-aligned local-halo metal-oxide-semiconductor (MOS) device with raised source/drain, in which a gate electrode and the raised source/drain act as self-aligned masks to form a local LDD/halo diffusion region therebetween. Therefore, an extra mask is not necessary and then the manufacturing process is simplified.
In order to achieve the above objectives, the present invention provides a method for forming a self-aligned local-halo metal-oxide-semiconductor device. At first, a semiconductor substrate with a first conductive type having a plurality of shallow trench isolation formed therein is provided. Then, sequentially forming a gate oxide and a gate electrode between each pair of the shallow trench isolations over the substrate. Next, forming a first sidewall spacer along each side of the gate electrode. And then, a second sidewall spacer is formed along one side of each first sidewall spacer. Thereafter, forming a raised source/drain upward on the substrate between each shallow trench isolation and each second sidewall spacer. Then, each second sidewall spacer is removed. Following, forming a lightly doped diffusion region with a second conductive type being opposite with the first conductive type between each raised source/drain and the gate electrode in the substrate. Finally, forming a halo diffusion region with the first conductive type surrounding the lightly doped diffusion region. By way of the present method, a local LDD/halo diffusion region with a low junction capacitance is obtained. And then, the operation speed of the MOS device is facilitated.
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Chen Tai-Ju
Tseng Hua-Chou
Lindsay Jr. Walter L.
Niebling John F.
Powell Goldstein Frazer & Murphy LLP
United Microelectronics Corp.
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