JPH012376A - 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 B0 Overview of the invention C0 Prior art [Figs. 4 to 6] D8 Problems to be solved by the invention [Fig. 7] E0 Means for solving the problems F0 Effects G, Embodiment [Figs. 1 to 3] H0 Effects of the invention (A, industrial application field) The present invention provides a photo sensor, particularly a p fi +4 on an insulating substrate.
The present invention relates to a photosensor in which a PIN photodiode is formed by laterally arranging a semiconductor layer, an intrinsic semiconductor layer, and an N'J4 semiconductor layer.

(B. Summary of the Invention) The present invention provides the photo sensor described above, in which a multilayer capacitor connected in parallel to the PIN photodiode is submerged in an insulating substrate in order to widen the dynamic range.

(C, Prior Art) [Figs. 4 to 6] As shown in Fig. 4, as a foot sensor, when a P-type semiconductor thin film is formed on a transparent insulating substrate a made of quartz or the like, an N-type semiconductor thin film 115! c and the conductor thin rI5! ,b-
A lateral type PIN photodiode PD is provided by forming an intrinsic (1) amorphous semiconductor thin layer 11!2d on the gap between the two sides, and this is used as a light receiving element. Figure 5 shows PI
FIG. 3 is an equivalent circuit diagram of an N photodiode PD. This PI
As shown in FIG. 6, the N photodiode PD is connected in series with a MOS transistor Q to form a photodetector circuit. In the drawing, φ is a switching pulse for switching the MOS transistor Q, and C1l is the equivalent reverse bias capacitance of the PIN photodiode PD.

The manufacturing process of the lateral type PIN photodiode PD is simpler than that of the sandwich-structured PIN photodiode, which is a stack of a P-type semiconductor thin film, an intrinsic (I) amorphous semiconductor thin film, and an N-type semiconductor thin film. The photomask pattern used 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 7] By the way, as mentioned above, the manufacturing process for a photosensor using a lateral type PIN photodiode PD as a light-receiving element is simple, IP, and a photo sensor. It has the advantage that a relatively large portion of the mask pattern can be used, but on the other hand, the P
Reverse bias capacity i c of IN photodiode PD,,
The problem is that the dynamic range is small and the signal retention characteristics are also poor.

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. 7 is a characteristic diagram showing the output voltage of the light detection circuit shown in FIG. 6 during the dark period, and shows the characteristics of the light detection 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. On the other hand, a sandwich-structured PIN with the same size as the PIN photodiode
In the case of a foot diode, the output voltage vX decreases very slowly as shown by the broken line. This difference is due to the difference in the reverse bias capacitance of the PIN photodiode, and the reverse bias capacitance of the lateral I'IN photodiode is smaller than that of the sandwich structure PIN photodiode. It is a manifestation.

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 was not a desirable characteristic of the photosensor.

The present invention was made to solve these problems, and its purpose is 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. do.

(E. Means for Solving the Problems) In order to solve the above problems, the photosensor of the present invention has a sandwich structure capacitor provided together with a PIN photodiode on an insulating substrate, and this capacitor is connected in parallel with a P/N photodiode. According to the foot sensor 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 As a result, the dynamic range becomes wider, and the optical detection signal retention characteristics become better.

(G. Embodiment) [FIGS. 1 to 3] The photosensor of the present invention will now be described in detail according to the illustrated embodiment.

1 to 3 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-
FIG. 3, which is a sectional view taken along line 2, is a photodetection circuit diagram.

In the drawing, 1 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 the N channel region forming the train and source, 3 is the gate insulating film of MO5I-Lancistor Q, 4 is the silicon case 1/electrode, 5 is the insulating film, 6 is the window for taking out the source electrode, 7 is the near side of the drain. An extraction window, 8 is a wiring film made of aluminum connected to the train 2n of the MOS transistor Q through the window 7, and 9 is the wiring 11! ≧8
This is the window opening for the pounding pad.

Reference numeral 10 denotes an N+ type semiconductor thin film constituting the PIN photodiode PD, which is formed in a comb shape.

11 is a P+ type semiconductor thin film, also formed in a comb shape, and the N4 type semiconductor thin film 10 and the 21 type semiconductor thin film 11 are inserted into a portion between one of them, and the other is formed in a comb shape.
They are provided in such a positional relationship that there is a substantially constant spacing between them. The reason why the N'' type semiconductor thin film 10 and the P+ type semiconductor thin film 11 are formed in a comb shape and made to face each other is to increase the ratio of the facing area to the same occupied area and obtain a large photocurrent, thereby increasing the sensitivity. be.

12 is an amorphous intrinsic (1) semiconductor thin film formed on a portion between the N+ type semiconductor thin film 10 and the 20 type semiconductor thin film 11; A diode PD is configured.

13 is a window opening through which the surface of the N0 type semiconductor thin film 10 is exposed;
Reference numeral 14 denotes a wiring film made of aluminum, whose negative end is connected to the source surface of the MOS transistor Q through the window opening 6, and whose other end is connected to the N1 type semiconductor thin film of the PIN photodiode PD through the window opening 13. 10
The wiring film 14 serves to connect the MOS transistor Q and the PIN photodiode PD in series.

Reference numeral 15 denotes a P+ type semiconductor thin film formed simultaneously with the P'' type semiconductor thin film 11, and is formed in a rectangular shape.

16 is a wiring film made of aluminum, one end of which is connected to the surface of the wiring film 14 through a window opening 17;
Amorphous intrinsic (1) Insulating film 5 on semiconductor thin film 12
It passes through the surface and further extends to a position facing the P+ type semiconductor thin film 15 with the insulating film 5 interposed therebetween. Thus, the capacitor CP is constituted by the P+ type semiconductor thin film 15 and the wiring +1#216 facing the P+ type semiconductor thin film 15 with the insulating film 5 interposed therebetween.

The capacitor CP will be connected in parallel to the PIN photodiode PD, so that a photodetection circuit as shown in FIG. 3 will be constructed.

That is, the PIN photodiode PD itself has an inherent reverse bias capacity ICu, and a capacitor CP consisting of the wiring film 16 and the P11 type semiconductor thin film 15 is connected in parallel to it, and this capacitor CP can compensate for the lack of capacity M of the reverse bias capacitance C2 inherent in the PIN photodiode PD. Therefore, the lack of dynamic range caused by the lack of 8 capacitors Cp can be resolved, and the signal retention characteristics can be improved. Specifically, the capacitor CP makes it easy to make the effective reverse bias capacity of the PIN photodiode PD similar to the natural reverse bias capacity of a sandwich-structured PIN photodiode (see the broken line in Figure 'A7). Ta.

In the above embodiment, since the wiring film 16 made of aluminum passes above the amorphous intrinsic (1) semiconductor layer 12, there is also the advantage that the light conversion efficiency of the PIN photodiode PD can be increased. It will be done.

This is because the aluminum forming the wiring film 16 has a reflective function and is located above the semiconductor thin film 12 that performs photoelectric conversion, so some of the light that enters the semiconductor thin film 12 is reflected by the semiconductor thin film 12. Even if the light passes through the thin film 12, it is reflected by the wiring film 16 and returns to the semiconductor thin film 12, where it is optically converted. Therefore, most of the light that enters the semiconductor thin film can be photoelectrically converted, and the photoelectric conversion efficiency can be increased.

(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, an electrode connected to one of the P-type semiconductor layer and the N-type semiconductor layer, and an electrode connected to one of the P-type semiconductor layer and the N-type semiconductor layer, and an electrode connected to the PIN photodiode on the insulating substrate, and an electrode connected to the PIN photodiode on the insulating substrate. The present invention is characterized in that a capacitor is formed which includes an electrode formed through an i-film and connected to the other of the P-type semiconductor layer and the N-type semiconductor layer.

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, and the dynamic range is widened. Characteristics get better.

[Brief explanation of drawings]

1 to 3 are for explaining one embodiment of the photosensor of the present invention, FIG. 1 is a plan view showing the pattern of winter clothes excluding the insulating film of the photosensor, and FIG. 1 is a cross-sectional view taken along the line 2-2 of FIG. 1 showing the cross-sectional structure of the sensor, FIG. 3 is a circuit diagram showing a light detection circuit, and FIGS. The figure is a cross-sectional view of the photosensor, Figure 5 is an equivalent circuit diagram, Figure 6 is a photodetection circuit diagram, and Figure 7 is a characteristic showing the output voltage in the dark to explain the problem to be solved by the invention. It is a diagram. Explanation of symbols 1... Insulating substrate, 5... Insulating film, 10... N-type semiconductor layer, 11... P-type semiconductor layer, 12... Intrinsic semiconductor layer, 14.15... Electrode , PD...PIN photodiode, CP...capacitor. ＼ To＼ｑ Shini (Mi Doto＄

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, a photo sensor is connected to one of the P-type semiconductor layer and the N-type semiconductor layer in the vicinity of the PIN photodiode on the insulating substrate. electrode,
A photosensor comprising a capacitor formed on the electrode through an insulating film and connected to the other of the P-type semiconductor layer and the N-type semiconductor layer.