JPH0964403A - Semiconductor device and manufacturing method thereof - Google Patents

Abstract

(57) Abstract: It is an object of the present invention to make a light receiving part and a driving part close to each other and to arrange a plurality of these in an array. An insulating film 206 made of silicon oxide having a film thickness of 1 μm is formed on the entire surface, and then the thin film transistor 21 is formed.
2, the gate wiring 207, the gate insulating film 208 made of silicon nitride, and the i-amorphous silicon layer 20.
9. A silicon nitride channel protection layer 210 is formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device used for an optical monitor of a large-scale optical path switching system in optical communication, imaging and image sensing of light from near infrared to far infrared, and a manufacturing method thereof. Regarding

[0002]

2. Description of the Related Art A visible light receiving portion is one-dimensional or two-dimensional.
Examples of light receiving devices arranged in a three-dimensional array include a CCD using crystalline silicon and a linear image sensor using amorphous silicon. These are TV cameras,
It is widely used in imaging parts such as copying and facsimile.

On the other hand, for receiving near-infrared rays having a wavelength of 1 μm or more used for optical communication, InG is epitaxially grown on an InP substrate which is usually a III-V group compound semiconductor.
A photodiode having an aAs layer is used. This is 1 μm for silicon, whether crystalline or amorphous.
This is because the absorption coefficient at the above wavelengths is extremely small, and it does not operate as a light receiving element. In addition, the longer wavelength 2-10
A compound semiconductor such as HgCdTe is used for receiving infrared light of nm. The following are examples of devices in which the light-receiving units for infrared light having a wavelength of 1 μm or more are arranged in a one-dimensional or two-dimensional array.

First, as shown in FIG. 6, photodiodes 62 are formed in an array on a compound semiconductor substrate 61 by mesa etching or impurity diffusion, and one electrode of each photodiode 62 is formed using the compound semiconductor substrate 61. The other electrode 63 is common, and the wiring 64 is individually taken out from each photodiode 62 and connected. Further, as shown in FIG. 7, there is a hybrid type imaging device. This is a flat sensor 71 made of a compound semiconductor substrate and an In bump 72.
It is electrically and mechanically joined to the input of the solid-state electronic scanning unit 73 via. In this flat plate type sensor 71, a pn junction 71a is formed as a light receiving portion. Also,
The solid-state electronic scanning unit 73 has a CCD 73b as a readout circuit formed on a silicon substrate 73a.

[0005]

Since the conventional configuration is as described above, there are the following problems.
First, in the light-receiving device shown in FIG. 6, since the wirings are individually taken out from the photodiodes arranged in an array, there is a problem that it becomes very difficult to take out the wirings when the scale of the array becomes large. . In order to solve this problem, switching elements may be installed in individual photodiode elements and the wiring may be arranged in a matrix.

However, it is extremely difficult to simultaneously form a photodiode made of a compound semiconductor for receiving infrared light and a switching element on the compound semiconductor substrate, as shown below. First, since the film thickness and the structure of the photodiode and the switching element are different, the compound semiconductor thin film in the photodiode part is epitaxially grown and etched, and then the compound semiconductor thin film in the switching element part is epitaxially grown and etched. By this process, this light receiving device is manufactured.

Alternatively, a very complicated multilayer structure in which both a photodiode and a switching element are laminated is epitaxially grown, and these are processed by etching,
Each element part will be formed. in this way,
Since the manufacturing process becomes very complicated and difficult, not only the cost becomes high, but also the yield when arranging a large number of light receiving elements in an array becomes very bad.

On the other hand, in the hybrid type image pickup device shown in FIG. 7, first, as the number of pixels increases, it becomes difficult to completely bond all the In bumps in each pixel. Further, there is a problem that the difference in thermal expansion between the compound semiconductor and the silicon crystal is a problem, and the mechanical and thermal reliability is low.

The present invention has been made to solve the above problems, and an object of the present invention is to make a light receiving portion and a driving portion close to each other and to arrange a plurality of these in an array. .

[0010]

A semiconductor device of the present invention is a photo device having a first-conductivity-type compound semiconductor layer and a second-conductivity-type compound semiconductor region formed on a substrate made of a compound semiconductor. It is characterized in that it has a diode and a thin film transistor for driving a photodiode formed of amorphous or polycrystalline silicon formed on the substrate via an insulating film. For this reason,
The photodiode and the thin film transistor that drives the photodiode are formed monolithically. Further, a method of manufacturing a semiconductor device according to the present invention includes a step of forming a compound semiconductor layer of a first conductivity type on a substrate made of a compound semiconductor, and a compound of a second conductivity type on a compound semiconductor layer of the first conductivity type. Forming a semiconductor region to form a photodiode; forming a second-conductivity-type compound semiconductor region and then forming an insulating film over the entire substrate; and forming an amorphous or polycrystalline film on the insulating film. And forming a thin film transistor made of silicon for driving the photodiode. Therefore, a thin film transistor that drives the photodiode is formed close to the photodiode without high temperature treatment.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram showing a configuration of a semiconductor device and an equivalent circuit according to the present invention described below. In the figure, 1 is a photodiode composed of a compound semiconductor, 2 is a thin film transistor as a switching element composed of amorphous silicon, and G ₁
˜G _n are gate wirings, D ₁ ˜D _n are data output wirings, and C is a common bias wiring.

When a voltage is applied to the common bias line C so that each photodiode 1 is reversely biased and a voltage is applied to the gate lines G _{1 to} G _n to turn on the thin film transistor 2, the photo of the pixel exposed to the light is photoactivated. An output corresponding to the amount of received light is output from the diode to the data wiring and can be read using an external detection circuit (not shown). Then, by sequentially applying a voltage to each of the gate wirings G _{1 to} G _n and sequentially turning on the transistors 2 in each column, the output from each photodiode 1 is output in accordance with the timing. It can be taken out from D _{1 to} D _n .

Embodiment 1 FIG. 2 is a sectional view showing a sectional structure of a single pixel as one embodiment of the present invention. It shows a state in which the photodiode and the thin film transistor in FIG. 1 are monolithically formed.
The manufacturing method will be described below with reference to FIG.

First, a film thickness of 2 μm is formed on the n-InP substrate 201.
m n ⁺ -InP layer 202, 2 μm thick i-In _x Ga
_1-x As layer 203 (x = 0.53), p ⁺ -with a film thickness of 1 μm
The In _x Ga _1-x As layer 204 (x = 0.53) is sequentially formed by M
Epitaxial growth is performed by the OCVD method. And p ⁺ -I
The n _x Ga _1-x As layer 204 and the i-In _x Ga _1-x As layer 20
3 is selectively etched, and n ⁺ -InP layer 202 and i-
In _x Ga _1-x As layer 203 and p ⁺ -In _x Ga _1-x As layer 2
A pin type photodiode portion 205 made of No. 04 was formed. Here, the n ⁺ -InP layer 202 layer becomes the common bias wiring in FIG.

Next, an insulating film 206 made of silicon oxide having a film thickness of 1 μm is formed on the entire surface, and a molybdenum film having a film thickness of 70 nm is deposited by a sputtering method. Then, the molybdenum film is patterned to form the gate wiring 207. Subsequently, a gate insulating film 208 made of silicon nitride and having a film thickness of 200 nm, an i-amorphous silicon layer 209 having a film thickness of 100 nm, and a film thickness of 200 made of silicon nitride.
a channel protective layer 210 having a thickness of nm. These are formed by patterning by photolithography or the like after film formation by the plasma CVD method.

After that, amorphous silicon to which n ⁺ -type impurities are added at a high concentration is formed by the plasma CVD method, and this film is patterned to obtain a film thickness of 70 nm.
Then, an n ⁺ -amorphous silicon layer 211 is formed. With the gate wirings 207 to n ⁺ -amorphous silicon layer 211 formed as described above, the thin film transistor 212
Is formed.

Next, an insulating film 213 made of silicon oxide having a film thickness of 200 nm is formed on the entire surface, and the n ⁺ -InP layer 20 is formed.
2, a contact hole is formed so that a part of the p ⁺ -In _x Ga _{1 -x} As layer 204 and the n ⁺ -amorphous silicon layer 211 are exposed. Then, an Al film having a film thickness of 1 μm is deposited thereon by a sputtering method and then patterned to form an n ⁺ -amorphous silicon layer 211,
Data output wiring 214 connected to the n ⁺ -InP layer 202
a, common bias wiring lead-out electrode 214c, and n
⁺ -Amorphous silicon layer 211 and p ⁺ -In _x Ga _1-x A
A connection wiring 214b for connecting the s layer 204 is formed.

As described above, according to the first embodiment, the photodiode portion and the thin film transistor portion can be formed monolithically close to each other. Amorphous silicon (a-Si) switching element (thin film transistor:
Since the TFT) has a low formation temperature as widely used as a switching element of an active matrix type liquid crystal display, it can be easily formed on various substrates.
Therefore, generally, the compound semiconductor can be formed on the compound semiconductor which is easily deteriorated by the high temperature process without deteriorating the compound semiconductor.

Further, the switching characteristics of the thin film transistor made of amorphous silicon, that is, the ratio of the ON and OFF currents is 6 digits, and matrix driving is possible even if they are arranged in a large two-dimensional array of several hundreds × several hundreds. Is possible. As a result, it is possible to easily arrange a plurality of cells each including the photodiode portion 205 and the thin film transistor portion 212 shown in FIG. 2, and to form an infrared image sensor in which a large number of light receiving portions are arranged in a one-dimensional or two-dimensional array. it can.

Embodiment 2 FIG. 3 is a sectional view showing a sectional structure of a single pixel in the second embodiment of the present invention. Hereinafter, the manufacturing method will be described with reference to FIG. First, n ⁺ -having a film thickness of 2 μm is formed on the n-InP substrate 201.
InP layer 202, 2 μm-thick i-In _x Ga _1-x As layer 203 (x = 0.53), 1 μm-thick n-InP layer 3
01 (x = 0.53) is sequentially grown epitaxially by MOCVD.

Then, Zn is selectively introduced and diffused by using a pattern of silicon nitride (not shown) as a mask, and p
^{A +} region 302 is formed. As described above, the pin type photodiode section 205 is formed by the p ⁺ region 302 formed by impurity diffusion. Then, after removing the pattern of silicon nitride, an insulating film 206 of silicon oxide having a film thickness of 1 μm is formed on the entire surface. After that, the thin film transistor section 212 and the Al wiring were formed as in the first embodiment.

In the second embodiment, unlike the above embodiment, the photodiode portion is formed by selective impurity diffusion. The single pixel portion shown in FIG. 3 can be formed in a plurality of arrays, for example, and as shown in this embodiment, one-dimensional or two-dimensional photodiode can be formed by impurity diffusion. It is easy to manufacture in a dimensional array.

Embodiment 3 FIG. FIG. 4 is a sectional view showing a sectional structure of a single pixel in the third embodiment of the present invention. The manufacturing method will be described below with reference to FIG. In this embodiment, the thin film transistor is formed using polycrystalline silicon.

First, an n-InP substrate 201 having a film thickness of 2 μm
An n ⁺ -InP layer 202 having a film thickness of 2 μm, an i-In _x Ga _1-x As layer 203 (x = 0.53) having a film thickness of 2 μm, and a p ⁺ -In _x Ga _{1-x having} a film thickness of 1 μm are formed on the top. As layer 204 (x = 0.5
3) is sequentially formed by epitaxial growth by MOCVD. Next, the p ⁺ -In _x Ga _1-x As layer 204 and the i-In _x Ga _1-x As layer 203 are selectively etched to form the photodiode portion 205. here,
The n ⁺ -InP layer 202 becomes the common bias wiring in FIG.

Next, an insulating film 206 of silicon oxide having a film thickness of 1 μm is formed on the entire surface, and then a film thickness of 100 nm is formed.
Then, silicon is deposited by a sputtering method so as to be formed so as to be patterned so as to remain in a desired region. Then, using an excimer laser, this silicon was polycrystallized to form a channel layer 601 made of polysilicon. next,
100 nm thick gate insulating film 6 made of silicon oxide
02 is deposited by a sputtering method, and then Mo is deposited to a film thickness of 70.
Then, the gate wiring 207 was formed by depositing it by sputtering so as to have a thickness of 0.9 nm, and patterning this.

Then, P by ion shower doping method
To form a source / drain region 603 and hydrogenate the channel layer 601 by hydrogen plasma treatment to form a thin film transistor portion 604. After that, the insulating film 21 made of silicon oxide and having a thickness of 200 nm is formed.
3 is formed on the entire surface, a contact hole is formed at a predetermined position, and then Al is deposited by a sputtering method of about 1 μm.
Then, this Al is patterned to form a data output wiring 214a, a connection wiring 214b, and a common bias wiring extraction electrode 214c.

As described above, similarly to the above-described embodiment, also in the third embodiment, the photodiode section and the thin film transistor section can be formed monolithically close to each other. That is, polycrystalline silicon (poly-Si)
The thin film transistor can be easily formed on various substrates without exposing the substrate to high temperature by using the laser annealing method in the polycrystallization process, and thus can be formed on the compound semiconductor. Like the thin film transistor made of amorphous silicon, the thin film transistor made of polysilicon has a 6-digit ratio of on and off currents, and matrix driving is possible even when arranged in a large two-dimensional array of several hundreds × several hundreds. It is possible to

Embodiment 4. By the way, although the photodiode portion is formed by selective etching in the third embodiment, the invention is not limited to this. As in the second embodiment described above, as shown in FIG. 5, the pin type photodiode section 205 may be formed by the p ⁺ region 302 formed by impurity diffusion. In this case, unlike the second embodiment, the thin film transistor portion 604 is formed using polycrystalline silicon instead of amorphous silicon. Also in the fourth embodiment, the photodiode portion and the thin film transistor portion can be formed monolithically close to each other, as in the above-described embodiments.

[0029]

As described above, according to the present invention, amorphous or polycrystalline silicon is formed via an insulating film on a compound semiconductor substrate on which a photodiode made of a compound semiconductor is formed. The thin film transistor for driving the photodiode is formed. Therefore, it is possible to bring the photodiodes, which are the light receiving portions, and the thin film transistors, which are the driving portions, close to each other, and to arrange a plurality of these in an array.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a configuration of a semiconductor device and an equivalent circuit according to the present invention.

FIG. 2 is a sectional view showing a sectional structure of a single pixel as one embodiment of the present invention.

FIG. 3 is a sectional view showing a sectional structure of a single pixel in a second embodiment of the present invention.

FIG. 4 is a sectional view showing a sectional structure of a single pixel according to a third embodiment of the present invention.

FIG. 5 is a sectional view showing a sectional structure of a single pixel according to a fourth embodiment of the present invention.

FIG. 6 is a plan view showing a configuration of a conventional light receiving element used for optical communication.

FIG. 7 is a perspective view (a) and a sectional view (b) showing a configuration of a conventional hybrid type imaging device.

[Explanation of symbols]

201 ... n-InP substrate, 202 ... n ⁺ -InP layer, 20
_{3 ... i-In x Ga 1} -x As layer, 204 ... p ⁺ -In _x Ga
_1-x As layer, 205 ... Photodiode section, 206, 2
13 ... Insulating film, 207 ... Gate wiring, 208 ... Gate insulating film, 209 ... i-Amorphous silicon layer, 210 ...
Channel protection layer, 211 ... N ⁺ -amorphous silicon layer, 212 ... Thin film transistor, 214a ... Data output wiring, 214b ... Connection wiring, 214c ... Common bias wiring extraction electrode.

Claims (3)

[Claims] 1. A photodiode including a compound semiconductor layer of a first conductivity type and a compound semiconductor region of a second conductivity type formed on a substrate made of a compound semiconductor, and an insulating film on the substrate via an insulating film. And a thin film transistor for driving the photodiode, which is made of amorphous or polycrystalline silicon formed by the above process. 2. The semiconductor device according to claim 1, wherein the thin film transistor and the photodiode are the first
A semiconductor device having a plurality of conductive compound semiconductor layers in common. 3. A step of forming a compound semiconductor layer of a first conductivity type on a substrate made of a compound semiconductor, and a compound semiconductor region of a second conductivity type being formed on the compound semiconductor layer of the first conductivity type, A step of forming a photodiode, a step of forming an insulating film over the entire substrate after forming the second conductivity type compound semiconductor region, and a step of forming amorphous or polycrystalline silicon on the insulating film, And a step of forming a thin film transistor for driving the photodiode.