Semiconductor device manufacturing: process – Making field effect device having pair of active regions... – On insulating substrate or layer
Reexamination Certificate
2003-01-03
2004-09-07
Le, Dung A. (Department: 2818)
Semiconductor device manufacturing: process
Making field effect device having pair of active regions...
On insulating substrate or layer
C438S149000, C257S151000, C257S413000
Reexamination Certificate
active
06787407
ABSTRACT:
FIELD OF THE TECHNIQUE
The present invention is a technique relating to a method of manufacturing a semiconductor device utilizing a crystalline semiconductor thin film containing silicon as a main component. More particularly, the invention relates a method of manufacturing a thin film transistor (hereinafter, referred to as TFT) utilizing a substrate having a crystalline semiconductor thin film containing silicon as the main component on an insulating substrate.
Throughout the present specification, the semiconductor device generally designates a device which functions utilizing a semiconductor. Thus, the electronic device or the like mounted thereto such as an arithmetic processing device, a storage processing device, or an electro-optical device as well as a single element such as the TFT are all contained in the category of the semiconductor device.
BACKGROUND ART
An active matrix liquid crystal display device is a monolithic display device in which a pixel matrix circuit and a driver circuit are provided on the same substrate. In the monolithic display device, it is the main stream, to employ the thin film transistors (TFTs). In the thin film transistor, an amorphous silicon film is formed on an insulating substrate such as a glass substrate or a quartz substrate to obtain an active layer. The development of a system-on-panel incorporating therein logic circuits such as a memory circuit and a clock generating circuit utilizing the TFTs has been advancing.
The high speed operation is required for such a driver circuit and the logic circuit, and therefore it is not suitable therefor that the amorphous silicon film is formed as the active layer on the quartz substrate or the glass substrate to obtain an element. For this reason, at present TFT in which a polycrystalline silicon film is used as the active layer is manufactured.
There are present some technologies in which after having deposited the amorphous silicon film on the quartz substrate or the glass substrate, the polycrystalline silicon film is obtained through crystallization. Of those, there is known a technique in which the catalytic metal element, with which the excellent electrical characteristics of the element are obtained when forming the element, and which promotes the crystallization of the amorphous silicon film, is added to the film to conduct the crystallization by a heat treatment. This technique will hereinbelow be described in more detail.
A semiconductor thin film having the amorphous structure containing as a main component a silicon is formed on an insulating substrate such as a quartz substrate or a glass substrate into a thickness on the order of 50 nm to 100 nm by LPCVD or the PECVD. Metal is added to the surface of the semiconductor thin film or into the semiconductor thin film having the above-mentioned amorphous structure to carry out the heat treatment therefor, thereby crystallizing the semiconductor thin film having the above-mentioned amorphous structure in the solid phase. The semiconductor thin film having the above-mentioned amorphous structure is crystallized in the solid phase so that a crystalline semiconductor thin film containing silicon as the main component is formed. Then, it is confirmed by the inventors of the present invention that the addition of the metal promotes the solid-phase crystallization, and it is therefore said that the metal acts as the catalyst during the solid-phase crystallization. In the present specification, the metal is referred to as the catalytic metal.
As for the phenomenon that the semiconductor thin film having the above-mentioned amorphous structure is crystallized by the heat treatment with the metal as a catalyst, a large number of reports have been made as the Metal Induced Lateral Crystallization (MILC). As the typical ones, there are the transition metal elements such as nickel (Ni), cobalt (Co), palladium (Pd), platinum (Pt), and copper (Cu). The presence of the catalytic metal becomes advantageous in the temperature and the time required for the semiconductor thin film having the above-mentioned amorphous structure to be crystallized in the solid phase as compared with the case where no catalytic metal is added. As a result, it has become clear that the Ni element shows excellent property as the catalytic metal. Hereinbelow, descriptions will be made on the assumption that the Ni element is employed as the catalytic metal.
The heat treatment required for the solid phase crystallization of the semiconductor thin film having the above-mentioned amorphous structure is performed at from 400° C. to 700° C. for several hours or more by the electric furnace, etc.
In the present specification, the semiconductor thin film having the amorphous structure containing silicon as the main component includes a SiGe thin film having the amorphous structure, in which the component ratio of Ge is less than 50%.
DISCLOSURE OF THE INVENTION
For the catalytic metal for promoting the crystallization of the semiconductor thin film having the above-mentioned amorphous structure, the transition metal element such as nickel (Ni), cobalt (Co), palladium (Pd), platinum (Pt), or copper (Cu) is employed. As generally well known, the metal such as Ni, if it is present in crystalline silicon, forms the deep levels to have a bad influence on the electrical characteristics and the reliability of the element. Therefore, the metal such as a Ni element needs to be removed from the region (element active region) in which the element is formed, and is used as the element. The above-mentioned crystalline semiconductor thin film is also concerned about the bad influence exerted on the element characteristics due to the catalytic metal.
Therefore, the metal such as the Ni element needs to be removed from the element active region to the degree at which it does not have a bad influence on the electrical characteristics. Removing the metal such as the Ni element from the element active region in the crystalline silicon is generally called gettering. The method of gettering which has been confirmed by the inventors of the present invention will hereinbelow be described.
An insulating film is formed on the above-mentioned crystalline semiconductor thin film. The insulating film is formed using a silicon oxide film, a silicon nitride film, or the like by the CVD apparatus or a sputtering apparatus. Then, the insulating film is formed into island-like shape. The island-like structure of the insulating film can be formed by utilizing photolithography and etching, which are general in the semiconductor technology.
A nonmetal element or ion of the nonmetal element is added to the crystalline semiconductor thin film with the insulating film as a mask, and a region, to which the nonmetal element or the ion of the nonmetal element has been added, is formed on the crystalline semiconductor thin film. That is, the nonmetal element or the ion of the nonmetal element is not added to the region in which the island-like structure of the insulating film is present on the crystalline semiconductor thin film, but are added to the region in which the island-like structure of the insulating film is absent. The nonmetal element or the ion of the nonmetal element is added thereto by thermal diffusion from a gas phase or by utilizing an ion implantation apparatus.
The nonmetal element or the ion of the nonmetal element is one kind of or plural kinds selected from the group consisting of boron (B), silicon (Si), phosphorus (P), arsenic (As), helium (He), neon (Ne), argon (Ar), krypton (Kr), and xenon (Xe).
The mechanism and the phenomenon of gettering of the transition metal elements in monocrystalline silicon are actively studied, and as a result, a considerable part thereof has become clear. While some of gettering in the polycrystalline silicon does not become clear in detail, the case of the monocrystalline silicon may be referred therefor. In polycrystalline silicon as well, the damage which is caused by the ion implantation method becomes an effective gettering. The mark which is generated by knocking o
Katsumura Manabu
Nakamura Osamu
Yamazaki Shunpei
Costellia Jeffrey L.
Le Dung A.
Nixon & Peabody LLP
Semiconductor Energy Laboratory Co,. Ltd.
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