Active solid-state devices (e.g. – transistors – solid-state diode – Field effect device – Having insulated electrode
Reexamination Certificate
1999-10-04
2002-05-07
Abraham, Fetsum (Department: 2826)
Active solid-state devices (e.g., transistors, solid-state diode
Field effect device
Having insulated electrode
C257S551000, C257S577000, C257S546000, C257S547000
Reexamination Certificate
active
06384453
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a high withstand voltage diode and a method for manufacturing such a high withstand voltage diode, and more particularly to a high withstand voltage diode suitable for use in protection of a high-voltage transistor, such as diode having a withstand voltage of 60 to 300 V which is used in the protection of a driver IC for a plasma display panel, or a protective diode having a withstand voltage of 200 to 1000 V in the protection of a power supply IC, and to a method for manufacturing such a diode.
2. Background of the Invention
Prior art related to the present invention will be described with regard to the example of a 150-V diode that is fabricated on a p-type semiconductor substrate, such as shown in FIG.
4
(
a
).
This high withstand voltage diode is fabricated by forming an n-type diffusion layer
32
having a surface concentration of 1×10
16
atoms/cm
3
and a depth of approximately 15 &mgr;m as a cathode on a 1×10
14
atoms/cm
3
substrate, and forming a p-type diffusion layer
34
onto that surface as an anode, and forming a n-type high-concentration diffusion layer
35
that serves as the cathode, which is approximately 15 &mgr;m distant from the anode. To alleviate the electrical field in the area surrounding the high-concentration p-type diffusion layer
34
of the anode, a low-concentration p-type diffusion layer
33
is formed.
The reference numeral
38
denotes a cathode electrode that is formed on the high-concentration n-type diffusion layer
35
,
39
is an anode electrode that is formed on the high-concentration p-type diffusion layer
34
, and
36
is a field insulation layer.
When the above-noted high withstand voltage diode is used for protecting a high-voltage transistor, however, because it is necessary to set the withstand voltage of the diode to a voltage that is lower than the withstand voltage of the transistor, it is necessary to adjust the concentration on the n-type diffusion layer
32
, which establishes the withstand voltage. For this reason, when the above-noted high withstand voltage diode is formed on the same chip for the purpose of protecting a high-voltage transistor on that chip, there is the problem that it is necessary to form separately an n-type diffusion layer
32
for a high withstand voltage diode and an n-type diffusion layer for a transistor, these diffusion layers having different concentrations, which results in an increase in the number of manufacturing steps, and an increase in cost.
FIG.
4
(
b
) shows the example of shorting a gate electrode
47
and a source electrode
49
of a high-voltage transistor and using the high-voltage transistor as a protective diode.
In this drawing, the reference numeral
42
denotes an n-type diffusion layer that is formed on a p-type substrate
41
,
43
is a low-concentration p-type diffusion layer that is formed so as to be adjacent to the n-type diffusion layer
42
,
44
is a high-concentration p-type diffusion layer that is formed on the surface of the low-concentration p-type diffusion layer
43
,
50
is a high-concentration n-type diffusion layer that is formed on the surface of the low-concentration p-type diffusion layer
43
,
45
is a high-concentration n-type diffusion layer that is formed on the surface of the n-type diffusion layer
42
,
47
is a gate electrode, which is formed via a gate oxide film so as to straddle the low-concentration p-type diffusion layer
43
and the n-type diffusion layer
42
, the gate electrode
47
is electrically connected to the high-concentration n-type diffusion layer
50
,
48
is a drain electrode that is formed on the high-concentration n-type diffusion layer
45
,
49
is a source electrode that is formed on the high-concentration p-type diffusion layer
44
and the high-concentration n-type diffusion layer
50
, and
46
is a field oxide film.
In the case of the structure shown in FIG.
4
(
b
), however, because the withstand voltages of the protected transistor and the diode are the same, rather than allowing surge currents and the like to escape via the diode, such surge currents and the like are caused to flow in parallel through the protected transistor and the protective diode, so that the surge current flowing through the transistor is reduced, thereby improving the immunity with respect to damage from surges.
For this reason, a larger protective diode is required, this resulting in an increase in the cost of the chip. With the diode shown in FIG.
4
(
b
), a parasitic NPN transistor is formed by the n-type diffusion layer
42
, the p-type diffusion layer
43
, and the n-type diffusion layer
50
that are formed between the anode and the cathode.
For this reason, when the parasitic NPN transistor is turned on, because of the current concentration and breakdown resulting, the current immunity of this diode after a breakdown was worse than that of a P-N junction alone.
Accordingly, it is an object of the present invention to improve on the above-noted drawbacks of the prior art, by providing a high withstand voltage diode, in which, without an increase in the number of manufacturing process steps, a high withstand voltage diode is formed that has a lower withstand voltage that the high-voltage transistor to be protected, thereby reliably protecting the high-voltage transistor. It is a further object of the present invention to provide a method for manufacturing the above-noted high withstand voltage diode.
SUMMARY OF THE INVENTION
To achieve the above-noted object, the present invention has the following basic technical constitution.
Specifically, the first aspect of a high withstand voltage diode according to the present invention is a high withstand voltage diode formed on a semiconductor substrate of a first conductivity type comprising, a first region of a second conductivity type formed on the semiconductor substrate, a high-concentration second region of the second conductivity type formed on a surface of the first region,a cathode electrode that is formed on the second region, a third region of the first conductivity type formed so as to be adjacent to the first region, a high-concentration fourth region of the first conductivity type that is formed on a surface of the third region, an anode electrode that is formed on the fourth region, and a gate electrode that is provided on a surface of the semiconductor substrate via an intervening gate oxide film so as to straddle the first region and the third region, the gate electrode is electrically connected to the fourth region.
The second aspect of a high withstand voltage diode according to the present invention is a high withstand voltage diode that protects a high withstand voltage transistor formed on a semiconductor substrate of a first conductivity type having a first region of a second conductivity type formed on the semiconductor substrate, a high-concentration second region of the second conductivity type formed on a surface of the first region, a drain electrode formed on the second region, a third region of the first conductivity type formed so as to be adjacent to the first region, a high-concentration fourth region of the first conductivity type formed on a surface of the third region, a high-concentration fifth region of the second conductivity type formed on a surface of the third region, a source electrode that is formed at least on the fifth region; and a gate electrode that is provided via an intervening gate oxide film so as to straddle the first region and the third region, the gate electrode being electrically connected to the fifth region, wherein the diode and the transistor are formed on a same semiconductor substrate, and the diode comprising, a first region of the second conductivity type of this diode that is formed simultaneously with the first region of the high-voltage transistor formed on the semiconductor substrate, a high-concentration second region of the second conductivity type that is formed within the first region of the diode, the high-concentration
LandOfFree
High withstand voltage diode and method for manufacturing same does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with High withstand voltage diode and method for manufacturing same, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and High withstand voltage diode and method for manufacturing same will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2842551