Active solid-state devices (e.g. – transistors – solid-state diode – Field effect device – Having insulated electrode
Reexamination Certificate
1998-08-28
2001-05-08
Crane, Sara (Department: 2811)
Active solid-state devices (e.g., transistors, solid-state diode
Field effect device
Having insulated electrode
C257S292000, C257S293000, C257S294000, C257S290000
Reexamination Certificate
active
06229165
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a semiconductor device for converting light and sound to electric signals.
Diodes, lateral bipolar transistors, and MOS transistors are known as a photoreceptor device incorporated in a semiconductor integrated circuit.
FIG. 1
is a sectional view showing a photoreceptor device having a conventional MOS transistor structure.
In
FIG. 1
, reference numeral
1
denotes a p-type silicon substrate;
2
, an n
+
-type source region;
3
, an n
+
-type drain region;
4
, an n
+
-type polysilicon gate electrode;
5
, a gate oxide film;
6
, an SiO
2
film;
7
, an interconnection;
8
, an Al light-reflecting film; and
9
, light.
The source region
2
, the drain region
3
, the gate electrode
4
, and the gate oxide film
5
constitute a MOS transistor. In the MOS-FET having this structure, a photoelectrically converted signal is detected by changing the current flowing between the drain and source regions.
Since the light
9
is incident on the photoreceptor portion from above the chip, no multilevel interconnection that interrupts the light
9
can be formed. For this reason, the design for a large-scale Integration (LSI) incorporating many photoreceptor devices such as image sensors is greatly limited, and the chip size cannot be decreased.
In recent LSIs, the number of interconnections is increasing to four or five. When a microprocessor, a memory, a logic, and an image sensor are mounted on one chip, the whole chip design is greatly limited because no multilevel interconnection can be formed at the image sensor portion.
Since the light
9
is incident on the upper surface of the silicon substrate from the electrode interconnection side, the light
9
is absorbed and reflected by the electrode interconnection and the gate, resulting in a low photoelectric conversion efficiency.
FIG. 2
is a view showing the layout of a conventional LSI.
In
FIG. 2
, reference numeral
11
denotes a microprocessor;
12
, a logic and a memory; and
13
, an image sensor. With an increase in integration degree, a multilevel interconnection made up of three or more layers is desirably formed on the image sensor
13
. However, no multilevel interconnection can be formed on the image sensor
13
because light is incident on the silicon substrate from the multilevel interconnection side in the conventional photoreceptor device structure.
When an LSI incorporating a photosensor and an image sensor with a multilayered structure is to be mounted on a logic LSI, a memory LSI, or the like, the upper LSI faces down and is connected to the lower one. Therefore, the conventional LSI incorporating a photosensor and an image sensor cannot be mounted with such a multilayered structure.
FIG. 3
is a view showing a typical CCD as a conventional image sensing device for photographing images.
FIG. 3
shows the state upon applying a clock
3
. A potential well
22
is formed in that portion of a silicon substrate
21
facing a gate G of a clock
3
, and charges
23
are generated in accordance with the intensity of incident light. An optical signal is converted into an electric signal as a charge amount, and the electric signal is stored in the potential well
22
.
After the signal is stored, clocks are cyclicly applied from
3
→
1
→
2
to transfer the electric signal rightward in FIG.
3
and output it from the final output stage.
In the image sensing device, since the signal enters the chip from above it, the signal is reflected and absorbed by the gate electrode material, resulting in a low photoelectric conversion efficiency.
BRIEF SUMMARY OF THE INVENTION
The present invention has been made in consideration of the above situation, and has as its object to provide a semiconductor device in which a multilevel interconnection can be formed without considering the light and sound input paths by inputting light and sound to a photoreceptor device from the side opposite to the multilevel interconnection side.
It is another object of the present invention to provide a semiconductor device in which the photoelectric conversion efficiency of the photoreceptor device can be increased by etching away part or all of silicon on the side opposite to an electrode interconnection and entering light into the photoreceptor device.
To achieve the above objects, according to the first aspect of the present invention, there is provided a semiconductor device comprising:
a silicon layer;
an insulating layer formed on the silicon layer;
a first semiconductor device formed on the insulating film to convert light into an electric signal; and
a second semiconductor device formed on the insulating film,
wherein a silicon region is formed in the silicon layer to shield the second semiconductor device from light, and a through hole extending through the silicon layer except for the silicon region to input light to the first semiconductor device is formed in a portion of the silicon layer corresponding to lower portions of the first and second semiconductor devices.
According to the second aspect of the present invention, there is provided a semiconductor device of the first aspect, wherein a surface of the silicon region is silicided.
According to the third aspect of the present invention, there is provided a semiconductor device of the first aspect, wherein a metal is formed on a surface of the silicon region.
According to the fourth aspect of the present invention, there is provided a semiconductor device of the second aspect, wherein a transparent electrode is formed on the silicided surface of the silicon region and a surface of the insulating film.
According to the fifth aspect of the present invention, there is provided a semiconductor device of the third aspect, wherein a transparent electrode is formed on surfaces of the metal and the insulating film.
According to the sixth aspect of the present invention, there is provided a semiconductor device of the first aspect, further comprising a transparent film covering the through hole.
According to the seventh aspect of the present invention, there is provided a semiconductor device of the first aspect, wherein the first semiconductor device is a Schottky diode.
According to the eighth aspect of the present invention, there is provided a semiconductor device of the seventh aspect, wherein the Schottky diode comprises:
an n-type region;
an n
+
-type region adjacent to the n-type region; and
a Schottky electrode for forming a Schottky junction with the n-type region.
According to the ninth aspect of the present invention, there is provided a semiconductor device of the eighth aspect, wherein an impurity is doped in the n-type region.
According to the 10th aspect of the present invention, there is provided a semiconductor device of the eighth aspect, wherein the n-type region is formed around the n
+
-type region.
According to the 11th aspect of the present invention, there is provided a semiconductor device of the first aspect, wherein the first semiconductor device is a p-n junction diode.
According to the 12th aspect of the present invention, there is provided a semiconductor device of the first aspect, wherein the first semiconductor device is a MOS transistor.
According to the 13th aspect of the present invention, there is provided a semiconductor device comprising:
a silicon layer;
an insulating layer formed on the silicon layer;
a plurality of first semiconductor devices formed on the insulating film to convert light into an electric signal; and
a plurality of second semiconductor devices formed on the insulating film,
wherein silicon regions are formed in the silicon layer to shield the plurality of second semiconductor devices from light, and a through hole extending through the silicon layer except for the silicon regions to input light to the first semiconductor devices is formed in a portion of the silicon layer corresponding to lower portions of the pluralities of first and second semiconductor devices.
According to the 14th aspect of the present invention, there is provided a semiconduc
Akazawa Yukio
Ieda Nobuaki
Ino Masayuki
Inokawa Hiroshi
Mano Tsuneo
Crane Sara
NTT Electronics Corporation
Pillsbury & Winthrop LLP
Tran Thien F.
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