Electricity: measuring and testing – Fault detecting in electric circuits and of electric components – Of individual circuit component or element
Reexamination Certificate
2001-11-05
2003-02-11
Jones, Deborah (Department: 1775)
Electricity: measuring and testing
Fault detecting in electric circuits and of electric components
Of individual circuit component or element
C324S719000, C117S002000, C438S014000, C438S017000
Reexamination Certificate
active
06518785
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a wafer for a heavy metal monitor and a method for monitoring an amount of heavy metal contamination in a wafer, which is capable of measuring the degree of heavy metal contamination with good accuracy, even in a manufacturing process in which a large-diameter wafer of 8 inches or 12 inches and over is being processed.
2. Description of the Related Art
In the past, in a process for manufacturing a semiconductor, heavy metal contamination, which causes a deterioration of the characteristics of a semiconductor, such as with regard to leakage, was measured and monitored by a minority carrier lifetime measurement apparatus which made use of the &mgr;-PCD method (microwave photoconductive decay).
In particular, because it was advantageous to have the wafer that is used for this monitoring be the same size as the wafer being processed, as the size of silicon wafers grew, in order to achieve rigidity with respect to stress, the thickness of the wafer grew large, the result being that the apparent lifetime became long, this hindering measurement with good accuracy.
FIG. 3
shows the method for monitoring heavy metal in the past. This wafer is subjected to thermal oxidation at a temperature in the range from 900° C. to 1000° C. in an atmosphere of O
2
or in an atmosphere of N
2
and O
2
, thereby achieving thermal treating for the purpose of preventing surface recombination.
However, a metal such as titanium, which has a low diffusion coefficient, is introduced into the oxide film during thermal treating, in which case there is a further deterioration of the measurement accuracy.
Accordingly, it is an object of the present invention to improve on the drawbacks of the prior as noted above, by providing a novel wafer which enables measurement of the amount of heavy metal contamination with good accuracy, even in a process of manufacturing a large-diameter wafer, and a further object to provide a method for monitoring an amount of heavy metal contamination in a wafer.
Another object of the present invention is to provide a novel wafer for monitoring heavy metal contamination that is capable of measuring of the amount of metal contamination with good accuracy, while suppressing the measurement error that is introduced by the introduction of a metal such as titanium, which has a low diffusion coefficient, into the oxide film.
SUMMARY OF THE INVENTION
In order to achieve the above-noted objects, the present invention adopts the following basic technical constitution.
The aspect of the present invention is a method for monitoring the amount of the heavy metal contamination on a wafer, this method comprising the steps of;
setting a wafer for monitoring an amount of heavy metal contamination in a prescribed monitoring place,
performing thermal treatment to the wafer at a temperature in the range from 1150° C. to 1350° C. in an atmosphere of O
2
+He or an atmosphere of H
2
+He,
performing thermal treatment to the wafer at a temperature in the range from 900° C. to 1000° C. in an atmosphere of N
2
+O
2
or an atmosphere of O
2
, and measuring an amount of heavy metal contamination in the wafer.
In a method for monitoring the amount of heavy metal contamination on a wafer, by measuring minority carriers lifetime, this method having a step of thermal treatment at a temperature in the range from 1150° C. to 1350° C. in an inert light element gas atmosphere of O
2
+He or an atmosphere of H
2
, +He, and a step of thermal treatment at a temperature in the range from 900° C. to 1000° C. in an atmosphere of N
2
+O
2
or an atmosphere of O
2
, and by means of these steps, it is possible to eliminate the measurement error that occurs because of the inclusion of a metal such as titanium, which has a low diffusion coefficient, into the oxide film during thermal treating, thereby resulting in the achievement of good measurement accuracy.
REFERENCES:
patent: 4668330 (1987-05-01), Golden
patent: 4706493 (1987-11-01), Chang et al.
patent: 5418172 (1995-05-01), Falster et al.
patent: 5698771 (1997-12-01), Shields et al.
patent: 5788763 (1998-08-01), Hayashi et al.
patent: 06342839 (1994-12-01), None
patent: 08-037216 (1996-02-01), None
patent: 10070165 (1998-03-01), None
Japanese Patent Office Action dated Feb. 20, 2001.
Jones Deborah
Katten Muchin Zavis & Rosenman
NEC Corporation
Stein Stephen
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