Semiconductor substrate processing method

Details Semiconductor substrate processing method Semiconductor substrate processing method

1998-09-30

2001-03-13

Saadat, Mahshid (Department: 2815)

Semiconductor device manufacturing: process

Making field effect device having pair of active regions...

Having insulated gate

C438S770000, C438S556000, C438S560000, C438S787000

Reexamination Certificate

active

06200872

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to a semiconductor substrate processing method, more specifically to a semiconductor substrate processing method for reducing crystal defects causing device failure.
Semiconductor substrates intrinsically contain various impurities and micro crystal defects caused by the various impurities. As micro crystal defects causing device failure, grown-in defects and micro oxygen precipitates have been recently noted. The grown-in defects are called also LSTDs (Laser Scattering Tomography Defects), COPs (Crystal Originated Particles) and FPDs (Flow Pattern Defects), but these names call the same defects. The defects are void-originated defects surrounded by SiO
2
film.
As semiconductor devices are more integrated, recently device failure caused by micro crystal defects are a serious problem. For improved yields of devices, reduction of such crystal defects is considered very important.
Prior art for reducing such crystal defects are hydrogen annealing and growth of epitaxial layers without defects on surfaces.
In the hydrogen annealing, as shown in
FIG. 16
a silicon substrate
100
containing grown-in defects
102
and micro oxygen precipitates
104
is subjected to oxygen out-diffusion annealing in a hydrogen gas ambient. The silicon substrate
100
is subjected to the annealing, e.g., in the hydrogen gas at 1200° C. for about 1 hour. This annealing makes defects
102
,
104
near the surface of the silicon substrate
100
smaller, and defects in the substrate surface are reduced. A device is fabricated on the surface of the silicon substrate
100
having defects reduced.
In the growth of an epitaxial layer, as shown in
FIG. 17
, a defect-free epitaxial layer
106
is grown on the surface of a silicon substrate
100
containing grown-in defects
102
and micro oxygen precipitates
104
. A device is fabricated on the defect-free epitaxial layer
106
.
In the hydrogen annealing, however, hydrogen gas is used at a high temperature of 1100-1200° C., and it is very dangerous to use the usual furnace. Accordingly, a special apparatus must be used. The universality lack of the apparatus is a problem.
In the growth of an epitaxial layer the growth of an epitaxial layer needs high costs, which makes wafers expensive. This is a problem. For example, an 8-inch wafer with an epitaxial layer formed on has a price even twice that of a usual wafer.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a semiconductor substrate processing method which includes no dangerous treatment, such as hydrogen annealing, and can effectively reduce defects which will be involved in device failure.
The above-described object can be achieved by a semiconductor substrate processing method comprising the steps of: surface-treating a semiconductor substrate to reduce a thickness of an oxide film on the surface of the semiconductor substrate to not more than 2 nm; loading the semiconductor substrate into a furnace with an ambient of an inert gas, except nitrogen, with keeping a temperature of the semiconductor substrate not more than about 300° C.; and increasing the temperature to a prescribed out-diffusion annealing temperature to out-diffuse impurities in the semiconductor substrate.
In the above-described semiconductor substrate processing method, it is possible that the method further comprises the steps of annealing the semiconductor substrate at a prescribed oxygen precipitation annealing temperature to form oxygen precipitates inside the semiconductor substrate.
In the above-described semiconductor substrate processing method, it is possible that the step of forming the oxygen precipitates is performed before the step of out-diffusing the impurities.
In the above-described semiconductor substrate processing method, it is possible that the step of forming the oxygen precipitates is performed after the step of out-diffusing the impurities.
In the above-described semiconductor substrate processing method, it is possible that the step of forming the oxygen precipitates is performed with the semiconductor substrate covered with an insulation film.
In the above-described semiconductor substrate processing method, it is preferable that the step of forming the oxygen precipitates is performed at a temperature which is not less than about 400° C. and not more than about 1000° C.
In the above-described semiconductor substrate processing method, it is preferable that the step of forming the oxygen precipitates is performed in an inert gas or an oxygen gas ambient.
In the above-described semiconductor substrate processing method, it is preferable that the prescribed out-diffusion annealing temperature is not less than about 1000° C. and not more than about 1300° C.
In the above-described semiconductor substrate processing method, it is preferable that the temperature increase from the temperature at the step of loading the semiconductor substrate into the furnace to the prescribed out-diffusion annealing temperature is performed at a temperature increasing rate of not less than about 3° C./min.
In the above-described semiconductor substrate processing method, it is preferable that the step of out-diffusing the impurities is performed in an ambient of an inert gas having a below 0.1 ppm O
2
concentration.
In the above-described semiconductor substrate processing method, it is preferable that the step of out-diffusing the impurities is performed in an ambient of an inert gas having a below 2 ppm H
2
O concentration.
In the above-described semiconductor substrate processing method, it is preferable that the step of out-diffusing the impurities is performed in an argon gas ambient.
In the above-described semiconductor substrate processing method, it is preferable that the impurities to be out-diffused in the step of out-diffusing the impurities is oxygen.


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