Semiconductor device manufacturing: process – Formation of semiconductive active region on any substrate – Polycrystalline semiconductor
Reexamination Certificate
1999-04-07
2001-07-17
Nelms, David (Department: 2818)
Semiconductor device manufacturing: process
Formation of semiconductive active region on any substrate
Polycrystalline semiconductor
C438S398000
Reexamination Certificate
active
06261930
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to the formation of a polysilicon layer, and more particularly to a method for the formation of polysilicon layer by irradiating with intermittently conducting Si
2
H
6
gas process on a silicon substrate layer of silicon wafer for a semiconductor.
2. Description of the Prior Art
Currently, the demand for high-density dynamic random access memory (DRAM) has rapily increased due to the widespread use of electronic equipment. In particular, the increasing popularity of some electronic equipment such as, for example, many kinds of computers are gradually increasing the demand for the large or very large semiconductor memories. Therefore, the advanced manufacture technology for improvement fabrication of DRAm is urgently needed.
No doubt one of the main technologies for improving DRAM performance is the Hemi-Spherical Grain (HSG) process. In fact, the recently Hemi-Spherical Grain (HSG) process is gradually applied to the production technology of High-Density DRAM. Futhermore, HSG process ideally will increase the surface area of the silicon layer in order to expand the capacity of the DRAM. This issue has been presented by previous laboratory experience already.
Basically, the HSG process firstly involves the deposit of an alpha-silicon thin film on the substrate of silicon wafer inside a PCVD furnace at 1 torr and 510°C to 550°C. Consequentially, the alpha-Silicon film surface is cleaned using SC-1 wet cleaning and then the native oxide layer is removed by HF dipping. Afterwards, HSG will grow in the UHV-CVD system chamber. When the wafer is irradiated for about 60 seconds, gas is conducted into the chamber. At this step, the temperature is arrived at about 200°C to 300°C as shown in
FIG. 1A
, then the flow of gas ceases after about 60 seconds. Thirdly, the temperature is held at 600°C. The whole treatment time is about 300 seconds at least. The pressure is about 10
−5
torr when the gas is being conducted into the chamber. Also, when the gas is not conducted into the chamber, the pressure will be about 10
−8
torr as shown FIG.
1
B. Also the flow of the gas fluid is about 10 sccm.
However, unfortunately the HSG process is still not totally desirable because it usually will take a long time for treating each wafer. On the other hand, it is still necessary to be refined again. Accordingly, the present invention presents a brand new preferred method.
SUMMARY OF THE INVENTION
In accordance with the present invention, a method is provided for forming a polysilicon layer that substantially exists on the substrate of a silicon wafer of a semiconductor.
In one embodiment, a polysilicon layer is first formed. Next an alpha-silicon layer is formed on the substrate. Then the temperature of the vacuum-chamber apparatus is increased as well. Sequentially the wafer is sent into the vacuum-chamber. After about 60 seconds, the gas is conducted intermittently into the vacuum-chamber when the temperature reaches about 200° C. to 300° C. Then the flow of gas is ceased. Sequentially, the temperature of wafer is held at about 600° C. and the gas is conducted and ceased a few times into the vacuum-chamber apparatus in order to irradiate this polysilicon layer. Not only is the process time for this polysilicon layer decreased but also the throughput in increased, and thereby the polysilicon layer is formed.
The intermittently conducting gas method for the present process forming polysilicon layer, which process is isolated as the following steps including both of the transmitting gas and ceasing gas process, is undertaken in a combination cycle and is repeated three times. Therefore, the whole conducting gas process invloves transmitting gas for few seconds and ceasing the flow of gas for few seconds, then transmitting gas for few seconds and ceasing the flow of gas gas for few seconds again and, finally transmitting gas for few seconds and ceasing the flow of gas for few seconds.
According to these processes, throughput thus increases and the process time for the polysilicon layer thus decreases in the formation of the polysilicon layer.
REFERENCES:
patent: 5326722 (1994-07-01), Huang
patent: 5930625 (1999-07-01), Lin et al.
patent: 6020247 (2000-02-01), Wilk et al.
patent: 6087240 (2000-07-01), Gilchrist
Chang Yi-Shin
Kao Ming-Kuan
Li Jui-Ping
Lin Ping-Wei
Dang Phuc T.
Mosel Vitelic Inc.
Nelms David
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