Method for forming an SOI substrate by use of a plasma ion...

Semiconductor device manufacturing: process – Formation of electrically isolated lateral semiconductive... – Implanting to form insulator

Reexamination Certificate

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C438S404000, C438S474000, C438S480000

Reexamination Certificate

active

06506662

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to a method and apparatus for forming a silicon on insulator substrate suitable for high performance semiconductor integrated circuits.
Separation by implanted oxygen method is one of the conventional methods for fabricating the silicon on insulator substrate disclosed in Journal of Material Research, Vol. 8, No. 3 pp. 523-534, 1993. According to this separation by implanted oxygen method, various kinds of ions are generated in an ion source and then subjected to mass separation by a mass separator to separate oxygen ions O+ from the various kinds of ions. The separated oxygen ions O+ are then implanted at a high dose into a silicon substrate. Subsequently, the oxygen ion implanted substrate is subjected to a heat treatment to form a continuous silicon dioxide film within the silicon substrate.
FIG. 1
is a schematic view illustrative of an ion-implantation apparatus used in the conventional method for forming the silicon on insulator substrate. The ion-implantation apparatus comprises a plasma generator
110
for generating various kinds of ions, a mass separator
120
coupled to the plasma generator
110
for separating oxygen ions O+ from the various kinds of ions generated d an ion-implantation chamber coupled to the mass separator
120
for accommodating and scanning a silicon substrate
140
to implant accelerated oxygen ions O+ into the silicon substrate
140
. The acceleration of the separated oxygen ions O+ prior to the implantation into the silicon substrate is made at an acceleration voltage in the range of 60 kV to 200 kV. The accelerated oxygen ions O+ are implanted into the silicon substrate
140
at a dose in the range of 2×10
17
atoms/cm
2
to 2×10
18
atoms/cm
2
.
The use of the above separation by implanted oxygen method makes it relatively easy to form a thin film silicon insulator substrate, wherein a silicon active layer overlying the silicon dioxide layer has a thickness of not more than 0.5 micrometers. However, the above separation by implanted oxygen method requires the oxygen ion-implantation of one hundred times the number of oxygen ions as compared to that of the normal ion-implantation process. This means that the above separation by implanted oxygen method requires a longer time for the oxygen ion implantation process. In order to shorten such longer time for the oxygen ion implantation process, a high performance ion implantation apparatus has been developed which is expensive. This increases manufacturing cost of the silicon on insulator substrate thereby increasing the price of the silicon on insulator substrate.
In the Japanese laid-open patent publication No. 4-249323, there is disclosed a method for forming a buried insulation layer in the silicon substrate, wherein a silicon dioxide layer as the buried insulation layer has a planerized interface with the silicon layer overlying this buried insulation layer. This is made as follows. First oxygen ions are implanted into a main face of the silicon substrate at a first high energy so that the distribution in density of oxygen implanted has a maximum value at a position deeper than the surface of the silicon substrate. The oxygen implanted substrate is then subjected to a heat treatment to form a silicon dioxide layer at a lower level than the surface level in this silicon substrate. Further, second oxygen ions are implanted into the main face of the silicon substrate at a second high energy which is lower than the first high energy so that the distribution in density of oxygen implanted has a maximum value at a position in the vicinity of the interface between the silicon dioxide layer formed by the above first ion-implantation process and the silicon layer overlying the silicon dioxide layer. The oxygen implanted substrate is then subjected to a heat treatment.
In the Japanese laid-open patent publication No. 4-356960, there is disclosed a method for forming a silicon on insulator substrate having a thin silicon monocrystal layer of a uniform thickness, which is almost free of crystal defects. This method is carried out as follows. Oxygen ions are implanted into a silicon wafer having a uniform and thin thickness before another silicon wafer is combined with this oxygen-implanted surface of the above silicon wafer with a heat treatment to thereby form a silicon dioxide film in the combined silicon wafer.
In the Japanese laid-open patent publication No. 5-275048, there is disclosed an oxygen ion implantation method which enables free control of a surface silicon layer and allows an additional formation of a high quality silicon layer as well which is capable of formation of a multiple layered silicon on insulator structure. A monocrystal silicon wafer is introduced into a vacuumed ion implantation chamber and then heated by a silicon wafer heater. Silicon atoms are evaporated from a silicon source whereby a monocrystal silicon layer is grown in vapor phase growth on the heated silicon wafer, wherein a shutter is used to control arrival of the evaporated silicon atoms onto the silicon wafer surface. A thickness tester is used to detect a rate of evaporation of silicon. A liquid nitrogen shroud is also used to absorb unnecessary gas molecules for emission thereof.
In the Japanese laid-open patent publication No. 5-335530, there is disclosed a method for forming a silicon on insulator substrate, which may suppress crystal defects such as slip lines as well as enable repair of crystal defects which may be caused by an oxygen ion implantation at a high dose, in addition which is capable of formation of the multi-layered silicon on insulator substrate comprising a semiconductor substrate, an insulation film overlying the semiconductor substrate and a crystal silicon layer overlying the insulation film. The insulation film is formed by oxygen ion implantation and subsequent annealing by excimer laser beam irradiation. The crystal silicon layer is then formed on the insulation film, and as required, a silicon layer is epitaxially grown on the crystal silicon layer. The above processes are repeated as required.
In the Japanese laid-open patent publication No. 5-299349, there is disclosed a method for forming a silicon on insulator substrate being thin and having an high crystal quality and less impurities. A polysilicon layer is deposited on a silicon substrate before an oxygen ion implantation into the polysilicon layer to thereby form a silicon dioxide film. A silicon layer overlying the silicon dioxide film is then subjected to a heat treatment to form a silicon on insulator substrate.
In the Japanese laid-open patent publication No. 6-37288, there is disclosed a method for forming a silicon on insulator substrate wherein an insulation film is thin and formed at a deep level from the surface of the substrate. The insulation film is formed by a high energy oxygen ion implantation and subsequent heat treatment to the substrate. A first oxygen ion implantation is carried out at an oxygen flow rate in the range of 1×10
15
ions/cm
2
to 1×10
16
ions/cm
2
. Subsequently a heat treatment is carried out at a temperature in the range of 600° C. to 900° C. A second oxygen ion implantation is carried out at an oxygen flow rate in the range of 2×10
17
ions/cm
2
to 8×10
17
ions/cm
2
. A final heat treatment is carried out at a temperature in the range of 1150° C. to 1400° C.
The above separation by implanted oxygen method has an advantage in relatively easy formation of the silicon on insulator substrate, but has a substantial disadvantage in an increased ion implantation time. In order to shorten the ion implantation time, it is, however, required to develop an exclusive and high performance ion implantation apparatus which is expensive. This leads to an increase in manufacturing cost of the silicon on insulator substrate thereby resulting in an increase in the price of the silicon on insulator substrate.
The foregoing conventional methods for forming the silicon on insulator substra

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