JPH012377A - photo sensor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] The present invention will be described in the following order.

A. Industrial field of application B9 Summary of the invention C1 Prior art [Figs. 5 to 7 1 D0 Problems to be solved by the invention [Fig. 8] E1 Means for solving the problems F1 Effects G, Embodiments [Figures 1 to 4] H9 Effects of the invention (A, Industrial application field) The present invention relates to a photosensor, in particular, a photo sensor, in which a P-type semiconductor layer, an intrinsic semiconductor layer, and an N-type semiconductor layer are laterally formed on an insulating substrate. The present invention relates to a photosensor in which a PIN photodiode is formed.

(B. Summary of the Invention) The present invention provides the above-mentioned photosensor, in order to widen the dynamic range without unnecessarily increasing the manufacturing process.
- an electrode made of a semiconductor layer integrally formed on one of the P-type semiconductor layer and the N-type semiconductor layer, and an insulating layer connected to the surface of the other semiconductor layer through a contact hole in the insulating layer; A capacitor constituted by an electrode made of a wiring film laminated through the PIN photodiode is provided to increase the reverse ha-r-as capacitance of the PIN photodiode.

(C, Prior Art) [Figures 5 to 7] As shown in Figure 5, as a photosensor, when a P-type semiconductor thin film is deposited on a transparent insulating substrate a made of quartz or the like, an N-type semiconductor thin film C is formed. An amorphous intrinsic (1) semiconductor thin film d is formed between the semiconductor thin films b and c to form a lateral type P.
There is one that constitutes an IN photodiode PD and uses this as a light receiving element. Figure 6 shows the PIN phototype auto P.
It is an equivalent circuit diagram of D. This PIN photodiode P
As shown in FIG. 7, D is connected in series with the M0S transistor Q to form a photodetector circuit. In addition, in the drawing,
φ is a switching pulse for switching the MO3h run transistor, and CH is an equivalent reverse bias capacitance of the PIN photodiode PD.

The lateral type PIN photodiode PD requires a more detailed manufacturing process than a PIN photodiode with a sandwich structure in which a P-type semiconductor thin film, an intrinsic (I) amorphous semiconductor thin film, and an N-type semiconductor thin film are laminated, and the required photodiode The mask pattern is also relatively simple. Therefore, it can be said that it is excellent in that it can reduce costs.

(D. Problem to be Solved by the Invention) [Figure 8] By the way, as mentioned above, the manufacturing process is simple and the photomask pattern of the photosensor using the lateral type PIN photodiode PD as the light receiving element is simple. It has the advantage of being relatively easy to use, but on the other hand, the PIN
There were problems in that the reverse bias capacitance aCH of the photodiode PD was small, resulting in a small dynamic range and poor signal retention characteristics.

This is because compared to a normal sandwich structure PIN photodiode, the lateral type PIN photodiode PD inevitably has a reverse bias capacitance C due to its structure difference.
H becomes extremely small, for example, one-third or less. This point will be explained in detail with reference to FIG.

FIG. 8 is a characteristic diagram showing the output voltage of the photodetector circuit shown in FIG. 7 in the dark, and shows the characteristics of the photodetector circuit when the switching pulse φ changes the transistor Q from on to off. It shows the change in output voltage (the horizontal axis is time t).

As is clear from this figure, in the conventional photosensor that uses a lateral PIN photodiode as a light receiving element, when the switching pulse φ falls, it is at a level approximately equal to the power supply voltage Vv, as shown by the solid line. The output voltage Vx rapidly drops from the power supply voltage Vv level to the ground level. A sandwich structure PIN with a size similar to that of the PIN photodiode.
In the case of a photodiode, the output voltage vx decreases more slowly as shown by the broken line. This difference is due to the difference in the size of the reverse bias capacitance of the PIN photodiode, and is an indication that the reverse bias capacitance of the lateral PIN photodiode is smaller than that of the sandwich structure PIN photodiode. It is.

If the reverse bias capacitance is small, the terminal voltage of the reverse bias capacitor CH reaches its maximum value with a small photocurrent. In other words, saturation occurs with a small amount of photocurrent, and the dynamic range becomes small. In addition, the retention characteristic for retaining the signal for a certain period of time also deteriorates. This is not a desirable characteristic of the photosensor.

The present invention has been made to solve these problems, and aims to widen the dynamic range of a photosensor that uses a lateral type PIN photodiode as a light receiving element, and to improve signal retention characteristics. shall be.

(E. Means for Solving the Problems) In order to solve the above problems, the photosensor of the present invention has an electrode made of a semiconductor layer integrally formed on one of the P-type semiconductor layer and the N-type semiconductor layer. and an electrode made of a wiring film that is connected to the surface of the other semiconductor layer through a contact hole in an insulating layer and laminated on the electrode with an insulating layer interposed therebetween.

(F. Effect) According to the photosensor of the present invention, since a capacitor is connected in parallel to the reverse bias capacitance of the I'IN photodiode, the reverse bias capacitance is substantially increased by the capacitor, and the dynamic range is widened. Optical detection signal retention characteristics are improved.

One electrode of the capacitor can be formed in the same process as one of the P-type semiconductor layer and the N-type semiconductor layer constituting the PIN photodiode, and the other electrode can electrically connect the other semiconductor layer. It can be formed in the same process as the wiring film to be taken out. Therefore, the capacitor can be formed without increasing the manufacturing process of the photosensor.
It is possible to improve characteristics such as expanding the dynamic range without increasing costs.

(G. Embodiment) [FIGS. 1 to 4] The photosensor of the present invention will be described in detail below according to the illustrated embodiment.

1 to 4 show one embodiment of the photosensor of the present invention, FIG. 1 is a plan view showing the patterns of each layer of the photosensor except for the insulating film, and FIG. -2
3 is a sectional view taken along line 3--3 in FIG. 1, and FIG. 4 is a photodetection circuit diagram.

In the drawing, ■ is a transparent insulating substrate made of, for example, glass, 2 is a semiconductor thin film forming the drain, channel, and source of an N-channel MOS transistor Q, 2n,
2n is an N-type semiconductor region forming the drain and source, 3 is M
Gate insulating film of OS transistor Q, 4 is a silicon gate electrode, 5 is an insulating film, 6 is a window for taking out the source electrode, 7
8 is a window for taking out the drain electrode, and 8 is a window for taking out the drain electrode.
This is a wiring film made of aluminum connected to the drain 2n of the oS transistor Q.

Reference numeral 9 denotes an N1 type semiconductor thin film constituting the PIN photodiode PD, which is formed in a comb shape.

Reference numeral 10 denotes a P-type semiconductor thin film, which is also formed in a comb shape, and includes an N+ type semiconductor thin film 9 and a P+ type semiconductor thin film 10.
The two are arranged in such a positional relationship that the other fits into the space between the two, creating a substantially constant distance between them. Forming the N+ type semiconductor thin film 9 and the P1 type half thin film 10 in a comb shape and making them face each other in this way increases the ratio of the opposing area to the same occupied area to obtain a large photocurrent, thereby increasing the sensitivity. This is to do so.

Reference numeral 11 denotes an amorphous intrinsic (1) semiconductor thin film formed on a portion between the N+ type semiconductor thin film 9 and the P" type semiconductor thin film 10, and the intrinsic (1) semiconductor thin film 11 and the semiconductor thin film 9
and 10 constitute a PIN photodiode PD. Reference numeral 12 denotes a P'' type semiconductor thin film formed integrally with the P+ type semiconductor thin film 10, and is formed in a rectangular shape. Reference numeral 13 denotes a wiring film made of aluminum and formed at the same time as the wiring film 8.
The insulating film 5 is connected to the source of the transistor Q and to the surface of the N3 type semiconductor thin film 9 through another contact hole 14, and bypasses the PIN photodiode PD to form an insulating film 5 on the P+ type semiconductor thin film 12. Laminated through. The wiring film 13 is thin in the detour portion, but is widened in the portion above the semiconductor thin film 12 so as to face the thin film 11i 12.

Thus, the capacitor CP is constituted by the P+ type semiconductor thin film 12 and the wiring film 13 facing the P+ type semiconductor thin film 12 with the insulating film 5 interposed therebetween. This capacitor CP will be connected in parallel to the PIN photodiode PD, thus:
A photodetection circuit as shown in FIG. 4 will be constructed.

In other words, the PIN photodiode PD itself has its own reverse bias capacitance C□, or the wiring IE213 and the capacitor CP whose electrodes are the P3 type half-thin i1A t2 are connected in parallel. , this capacitor CP can compensate for the insufficiency of the reverse bias capacitance C, , inherent in the PIN photodiode PD. Therefore, it is possible to solve the problem of insufficient dynamic range due to insufficient capacity of the capacitor CP, and to improve signal retention characteristics. Specifically, the capacitor cp makes it easy to make the effective reverse bias capacitance of the PIN photodiode PD similar to that of the sandwich-structured PIN photodiode (see the broken line in FIG. 8).

The P-type semiconductor thin film 12 forming one electrode of the capacitor CP is formed integrally with the P1-type half thin film 10.
The wiring film 13 forming the other electrode of the capacitor CP is formed at the same time as the wiring film 8, and no special process is required to form the capacitor CP. Therefore, it is possible to improve characteristics such as expanding the dynamic range without providing a special process.

(H, Effects of the Invention) As described above, the photosensor of the present invention has a PIN photodiode formed by laterally disposing a P-type semiconductor layer, an intrinsic semiconductor layer, and an N-type semiconductor layer on an insulating substrate. In the photosensor, a Ti pole constituted by a semiconductor layer integrally formed with one of the N-type semiconductor layer and the P-type semiconductor layer, and the other of the N-type semiconductor layer and the P-type semiconductor layer. A capacitor consisting of an electrode connected to the surface of the insulating film through a window opening and formed of a wiring film laminated on the above electrode via an insulating film is placed near the PIN photodiode on the insulating substrate. It is characterized by the fact that it has been provided.

Therefore, according to the photosensor of the present invention, since the capacitor is connected in parallel to the reverse bias capacitance of the PIN photodiode, the reverse bias capacitance is substantially increased by the capacitor, the dynamic range is widened, and the photodetection signal retention characteristic is gets better.

The capacitor can be formed in the same process as one of the P-type semiconductor layer and the Njq semiconductor layer that constitute the PIN photodiode, and the other electrode can electrically take out the other semiconductor layer. It can be formed in the same process as the wiring film. Therefore, the capacitor can be formed without increasing the manufacturing process of the photosensor, and characteristics such as an expansion of the dynamic range can be improved without increasing the cost.

[Brief explanation of the drawing]

1 to 4 are for explaining one embodiment of the photosensor of the present invention. FIG. 1 is a plan view showing a pattern of eight films excluding the insulating film of the photo sensor, and FIG. A cross-sectional view taken along line 2-2 in Figure 1 showing the cross-sectional structure of the photosensor, Figure 3 is a cross-sectional view taken along line 3-3, and Figure 4 is a cross-sectional view taken along line 3-3.
The figure is a circuit diagram showing a photodetection circuit, and Figures 5 to 7 show conventional technology. Figure 5 is a cross-sectional view of a photosensor, Figure 6 is an equivalent circuit diagram, and Figure 7 is a photodetector circuit. FIG. 8 is a characteristic diagram showing the output voltage in the dark for explaining the problem to be solved by the invention. Explanation of symbols 1... Insulating substrate, 5... Insulating film, 9... N-type semiconductor layer, 10... P-type semiconductor layer, 11... Intrinsic semiconductor layer, 12.13... Electrode , PD...PIN photodiode, Cp...capacitor. −. 9 products 2 items -" Light detection circuit diagram 4th picture

Claims (1)

[Claims] (1) P-type semiconductor layer, intrinsic semiconductor layer and N
In a photosensor in which a PIN photodiode is formed by laterally arranging type semiconductor layers, an electrode constituted by a semiconductor layer integrally formed with one of the N-type semiconductor layer and the P-type semiconductor layer; Above N
a capacitor comprising an electrode connected to the other surface of the P-type semiconductor layer and the P-type semiconductor layer through a window opening in an insulating film and formed of a wiring film laminated on the electrode with an insulating film interposed therebetween. , a photosensor provided near the PIN photodiode on the insulating substrate.