Semiconductor device manufacturing: process – Making field effect device having pair of active regions... – On insulating substrate or layer
Reexamination Certificate
1998-01-09
2001-08-28
Smith, Matthew (Department: 2825)
Semiconductor device manufacturing: process
Making field effect device having pair of active regions...
On insulating substrate or layer
Reexamination Certificate
active
06281057
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of manufacturing a semiconductor device, and in particular to a method of manufacturing a semiconductor device having a semiconductor layer.
2. Description of the Background Art
Conventionally, liquid crystal displays (LCDs) include a display pixel portion arranged in a matrix and a drive circuit portion which drives the display pixel portion. Generally, for LCDs, a transistor which configures the drive circuit portion is required to have higher mobility (rapidity) than a transistor which configures the display pixel portion. In recent years, high mobility has been achieved to some extent by employing polycrystalline silicon film as an active layer of a thin film transistor (TFT) which configures the drive circuit. Thus, the TFT formed of polycrystalline silicon film has been employed as not only a transistor configuring the display pixel portion but also a transistor configuring the drive circuit portion. As polycrystalline silicon film has been used as the active layers of a TFT configuring the display pixel portion and the TFT configuring the drive circuit portion, a so-called LCD integral with a drive circuit has been developed in which the display pixel portion and the drive circuit portion are formed on the same substrate.
For LCDs including such a TFT that employs polycrystalline silicon film as an active layer, a further rapid TFT configuring the drive circuit portion is required with higher definition and higher density of the pixels of the LCDS. Accordingly, researches have been conventionally conducted to improve the mobility of the TFT active layer formed of polycrystalline silicon film. Various methods have been proposed to achieve high mobility, for example, by changing a material gas used in forming a silicon layer serving as a polycrystalline silicon film from silane (SiH
4
) gas to disilane (Si
2
H
6
) gas to relatively increase the grain size of the polycrystalline silicon film after its solid phase crystallization (SPC).
However, it is difficult to obtain a TFT active layer of sufficient high mobility even with such a technique proposed as above. Thus, it is particularly difficult to achieve a faster drive circuit when such a TFT is used in an LCD and hence to improve the display characteristics of the LCD.
SUMMARY OF THE INVENTION
One object of the present invention is to readily manufacture a semiconductor device with a semiconductor layer of high mobility in a method of manufacturing the semiconductor device.
Another object of the present invention is to reduce crystal defect of a semiconductor layer and the roughness of a surface of the semiconductor layer in a method of manufacturing a semiconductor device.
A method of manufacturing a semiconductor device in one aspect of the present invention includes the steps of: initially forming a semiconductor layer on a substrate; irradiating the semiconductor layer with high energy beam; and then performing a heat treatment under a temperature condition capable of reducing the roughness of a surface of the semiconductor layer. According to the present invention, since a semiconductor layer is irradiated with high energy beam, crystal defect of the semiconductor layer can be reduced and the crystallinity of the semiconductor layer can thus be improved. Furthermore, the heat treatment under a temperature condition capable of reducing the surface roughness of the semiconductor layer after the radiation of high energy beam can effectively reduce the roughness of the surface of the semiconductor layer increased due to the radiation of high energy beam. Thus, the manufacturing method in one aspect of the present invention can reduce crystal defect of a semiconductor layer and the roughness of a surface of the semiconductor layer. Thereby, the field-effect mobility of the semiconductor layer can be improved and the drain current of the semiconductor layer can thus be increased. With such a semiconductor layer used in a liquid crystal display, the drive circuit portion can rapidly operate and the high definition and high density of the pixel portion can be achieved. It is preferable that the heat treatment be performed at a temperature of 900° C. to 1100° C., preferably in rapid thermal annealing. The use of rapid thermal annealing allows a high temperature treatment to be finished in an extremely short period of time, and thus disadvantages, such as deformation of the substrate, can be avoided while crystal defect of the semiconductor layer or the like is reduced by the high-temperature heat treatment.
In the method of manufacturing a semiconductor device in the above one aspect of the present invention, solid phase crystallization may be employed to render an amorphous semiconductor layer polycrystalline so that a polycrystalline silicon layer is formed, and the polycrystalline semiconductor layer may be irradiated with high energy beam. The radiation of high energy beam is preferably provided while the polycrystalline semiconductor layer is heated, preferably in 100° C. to 600° C. Since the polycrystalline semiconductor layer is heated at the same time as the radiation of high energy beam, the roughness of a surface of the polycrystalline semiconductor layer can be reduced and the mobility of a transistor can thus be improved. Furthermore, the cost for maintenance of the laser device can be reduced since laser energy density can be reduced as compared with the case where heating is not provided during laser radiation. Prior to the radiation of high energy beam, a surface of the polycrystalline semiconductor layer may be oxidized to form oxide film which is then removed to expose a surface of the polycrystalline semiconductor layer and the exposed polycrystalline semiconductor layer may be irradiated with high energy beam to further improve the crystallinity of the polycrystalline semiconductor layer.
In the method of manufacturing a semiconductor device in the above one aspect of the present invention, a substrate may be provided thereon with an amorphous semiconductor layer which is then irradiated with high energy beam to render the amorphous semiconductor layer polycrystalline so that a polycrystalline semiconductor layer is formed. The heat treatment may be performed immediately after the radiation of high energy beam, or after an insulating film and a polycrystalline silicon film are successively formed on the polycrystalline semiconductor layer after the radiation of high energy beam. The heat treatment is preferably performed through rapid thermal annealing. The use of rapid thermal annealing allows a high-temperature treatment to be finished in an extremely short period of time, and thus disadvantages, such as deformation of the substrate, are avoided while crystal defect of the semiconductor layer or the like is reduced by a high-temperature heat treatment.
In the method of manufacturing a semiconductor device in the above one aspect of the present invention, high energy beam preferably includes either laser or xenon arc lamp. When laser or xenon arc lamp is used, the crystals of the semiconductor layer can effectively absorb the radiated energy and thereby the crystallinity of the semiconductor layer as an active layer can readily be improved. Furthermore, the semiconductor layer may include a silicon layer. Preferably, the semiconductor layer includes an active layer of a thin film transistor. Furthermore, a gate electrode may be formed on the semiconductor layer after the formation of the semiconductor layer with a gate insulating layer interposed therebetween, or the semiconductor layer may be formed on a gate electrode formed on the substrate with a gate insulating layer interposed therebetween.
A method of manufacturing a semiconductor device in another aspect of the present invention includes the steps of: initially forming an amorphous semiconductor layer on an insulating substrate; rendering the amorphous semiconductor layer polycrystalline by solid phase crystallization to form a polycrystalline semicon
Abe Hisashi
Aya Yoichiro
Hamada Hiroki
Nakahara Yasuo
Nouda Tomoyuki
Armstrong Westerman Hattori McLeland & Naughton LLP
Lee Calvin
Sanyo Electric Co,. Ltd.
Smith Matthew
LandOfFree
Method of manufacturing a semiconductor device does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method of manufacturing a semiconductor device, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method of manufacturing a semiconductor device will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2501988