Active solid-state devices (e.g. – transistors – solid-state diode – Responsive to non-electrical signal – Electromagnetic or particle radiation
Reexamination Certificate
2001-09-07
2002-07-09
Wilson, Allan R. (Department: 2815)
Active solid-state devices (e.g., transistors, solid-state diode
Responsive to non-electrical signal
Electromagnetic or particle radiation
C257S440000
Reexamination Certificate
active
06417553
ABSTRACT:
BACKGROUND OF INVENTION
1. Field of the Invention
The invention relates to a semiconductor wafer that can detect radiation, and more particularly, to a semiconductor wafer that uses a conducting state of a channel of a field oxide to measure radiance.
2. Description of the Prior Art
Due to the extensive use of semiconductor devices, semiconductor wafers are more often subjected to environments that have a large amount of radiation. This radiation can cause a semiconductor device to malfunction. Please refer to FIG.
1
.
FIG. 1
is a structural diagram of a prior art semiconductor wafer
10
. The semiconductor wafer
10
has two N-type metal-oxide-semiconductor (NMOS) transistors
12
A and
12
B on a P-type substrate. Each NMOS transistor has a gate
16
A or
16
B, a source
18
A or
18
B, a drain
20
A or
20
B, and a gate oxide
22
A or
22
B. In the highly compact modern circuit layouts, distances between transistors are extremely small, and are isolated by field oxides, like field oxide
28
in the semiconductor wafer
10
, to prevent mutual electrical interference. Conductive layer
26
on the field oxide
28
provides a link to each transistor. The conductive layer
26
is typically a metallic link in the semiconductor wafer
10
. In addition, a channel stop
15
is below the field oxide
28
.
When a semiconductor wafer
10
is subject to radiation, the energy of the radiation will create electron-hole pairs in the oxide layer in semiconductor wafer
10
.Holes are more likely to be retained in the oxide layer because hole mobility is slower in an oxide layer. In a field oxide layer, the above phenomenon is more evident. Compared to other oxide layers (such as a gate oxide) in a semiconductor wafer, electron-hole pairs are more likely to occur in the field oxide layer, and holes are more likely to accumulate in a field oxide because the volume of a field oxide is larger.
When the conductive layer
26
passes over the field oxide
28
, field oxide
28
, conductive layer
26
and two electrodes
18
A and
20
B become, in effect, a field oxide transistor. Field oxide
28
is equivalent to a gate oxide capacitor. Charge carried by holes accumulated in the field oxide
28
reduces the threshold voltage of the equivalent field oxide transistor. It is well known that changing the amplitude of the threshold voltage of a metal-oxide-semiconductor is proportional to charge of the gate oxide capacitance, and inversely proportional to the capacitance of a gate oxide capacitor. In a metal-oxide-semiconductor transistor, when the gate oxide capacitance is very small, even very little net charge on the gate oxide capacitor will cause dramatic change of the threshold voltage. This change of threshold voltage in the above equivalent field oxide transistor is particularly evident. Because holes easily accumulate in the field oxide, and the field oxide is very thick, the equivalent gate capacitance of the field oxide is relatively small, and the threshold voltage caused by charge is thus affected more. If too much charge accumulates on the field oxide
28
because of radiation, the threshold voltage of the field oxide transistor is, in effect, reduced. If there is electric activity in the conductive layer
26
, a channel will form below the field oxide
28
and activate the equivalent field oxide transistor. An improper electric connection between the electrode
18
A and the electrode
20
B on two sides of the field oxide
28
is formed. Then, the functionality of the field oxide
28
to isolate transistor
12
A and transistor
12
B is damaged and causes the semiconductor wafer
10
to malfunction.
In the prior art, the semiconductor wafer
10
has no advance warning that the semiconductor wafer
10
is being influenced by radiation. When negative affects induced by radiation accumulate to cause a prior art semiconductor wafer
10
to malfunction, normal operations of a microprocessor system based on the semiconductor wafer
10
is severely and adversely influenced.
SUMMARY OF INVENTION
It is therefore a primary objective of the present invention to provide a semiconductor wafer that can detect radiation and provide a warning signal when the semiconductor wafer is subjected to radiation-induced damage in the early stages of exposure.
Briefly, in a preferred embodiment, the present invention provides a semiconductor wafer having at least one sensor comprising. The sensor includes a field oxide transistor, and a detecting circuit electrically connected to the field oxide transistor for detecting if the field oxide transistor is switched on or off and generating corresponding detecting signals.
It is an advantage of the present invention that the semiconductor wafer according to the present invention can detect radiation and provide a corresponding warning. Malfunctions of a semiconductor wafer can thus be prevented.
These and other objects and the advantages of the present invention will no doubt become obvious to those of ordinary skill in the art after having read the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings.
REFERENCES:
patent: 5412243 (1995-05-01), Morishita
patent: 5945722 (1999-08-01), Tsuei et al.
patent: 6114740 (2000-09-01), Takimoto et al.
patent: 06216385 (1994-08-01), None
patent: 2000150662 (2000-05-01), None
Chiang Chien-Shan
Chou Kuo-Yu
Ho Lo-Chun
Hsu Chih-Hsueh
AMIC Technology (Taiwan) Inc.
Hsu Winston
Wilson Allan R.
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