JPH0568868B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a photoelectric conversion element, and particularly to an integrated type conversion element capable of generating high voltage.

[Background technology]

When photodiodes are integrated into a semiconductor substrate as shown in FIG. 1, for example, a plurality of PN diodes as shown in FIG. A connection method as shown in Figure 3 can be considered, but in this case, it is a Darlington connection of bipolar transistors,
Only a small amount of output voltage and current could be obtained.

[Purpose of the invention]

Therefore, an object of the present invention is to eliminate the leakage current caused by the parasitic bipolar transistor and efficiently generate high voltage.

[Disclosure of the invention]

In order to achieve the above object, the present invention provides a semiconductor substrate of a first conductivity type, a plurality of first regions of opposite conductivity type formed at intervals on a surface portion of the substrate, and first regions of the opposite conductivity type. a third region of the opposite conductivity type formed on the surface of each second region; an insulating film formed on the surface of the semiconductor substrate; a conductive film that electrically connects one of the first regions and a second region formed on the surface thereof, and electrically connects this to a third region formed in another first region spaced apart from these; and x j1 is the junction depth of the first region with the semiconductor substrate, x _j2 is the junction depth of the second region with the first region, and x _j2 is the junction depth of the second region with the semiconductor substrate, and Let the junction depth of be x _j3 ,
When the number of first regions connected to each other is n and the absorption coefficient of incident light is α, these are as follows: 1>exp(−α・x _j1 +x _j2 /2) +nexp(−α・x _j2 +x _j3 /2) Each of the above welding depths is adjusted so as to satisfy the relational expression:
The gist of the present invention is an integrated photoelectric conversion element characterized in that x _j1 , x _j2 , and x _j3 are determined.

Hereinafter, the present invention will be explained in detail based on drawings showing embodiments thereof. FIG. 4 shows a cross section of an embodiment of the present invention, in which numerals 1 and 1a are N-type first regions, which are formed so as to be spaced apart from each other on the surface portion of a P-type substrate 4. FIG. 2 and 2a are P-type regions formed on the surfaces of the first regions 1 and 1a. 3 and 3a are P-type third regions formed on the surfaces of the second regions 2 and 2a. These three regions 1, 1a, 2, 2a, 3, 3a are formed in the P-type substrate 4 by N-P-N triple diffusion. 5 is an insulating film formed on the surface of the substrate 4, 7, 7 are P ⁺ diffusion regions of the channel stopper, and 8, 8a are for ohmic contact with the channel stopper.
N ⁺ diffusion region. Reference numeral 6 denotes a conductive thin film provided on the insulating film 5, which electrically connects the first region 1a and the second region 2a formed on the surface thereof on the one hand, and connects these regions 1a,
2a is electrically connected to a third region 3 in the first region 1 formed apart from these.

FIG. 5 shows a cross section of a second embodiment of the invention, in which a P-type substrate 4 having N ⁺ buried diffusion layers 9, 9a is shown.
An N-type epitaxial growth layer is formed thereon, and first regions 1, 1a are formed therein, separated from each other by P-type isolation diffusion layers 7, 7a. The P-type second regions 2, 2a and the N-type third regions 3, 3a are formed in the first regions 1, 1a by double diffusion. 8 and 8a are N ⁺ layers provided for channel stoppers and ohmic contacts. Reference numeral 6 denotes a conductive thin film formed on the insulating film 5, which electrically connects the separated third region 3 and second region 2a, and connects the first region and second region to regions 8, 2, and 8a and 2a are electrically connected.

FIG. 6 shows a cross section of the above embodiment, where x _j1 , x _j2 , and x _j3 are first regions 1 and 1, respectively.
a is the junction depth (diffusion depth) of the second regions 2, 2a and the third regions 3, 3a.

In the NPN junction formed from the first region, the second region 2, and the third region 3, since the first region 1 and the second region 2 are electrically connected, parasitic bipolar No transistor is formed. Similarly, in the PNP junction formed from the substrate 4, the first region 1, and the second region 2,
No parasitic bipolar transistors are formed.

Therefore, the equivalent circuit of the element structure of the present invention is not a circuit including transistors as shown in FIG. 3, but a circuit consisting only of diodes as shown in FIG. 7, which eliminates the problems in the conventional example. This eliminates the leakage current that is amplified through transistors, which was thought to be the case.

In the device structure of the present invention, it is necessary to reduce leakage current from the diode ( _IL in FIG. 4).

Now, when light with a wavelength λ is incident on the surface of the third region 3, 3a at a density Φ ₀ , and its absorption coefficient is α, the photocurrent I _P is I _P =Φ ₀ {1−exp(−αx _j1 + x _j2 /2)} ...(1) However, at the same time, the leakage current to the board 4 side
I _L also exists by I _L = Φ ₀ exp (−αx _j2 + x _j3 /2) ... (2).

FIG. 7 shows an equivalent circuit when n photodiodes having the structure shown in FIG. 6 are connected in series as shown in FIG. 4 or 5. In order to obtain a photocurrent between the terminals of this circuit, it is necessary that I _P > nI _L , and therefore, (1) above,
From equation (2), it is necessary that the following relational expression 1>exp(-αx _j1 +x _j2 /2) +nexp(-αx _j2 +x _j3 /2)...(3) be satisfied.

For example, x _j1 = 16 μm, x _j2 = 14 μm, x _j3 = 9 μm
If 10 photodiodes are connected in series (n = 10), α = 2 × 10 ³ cm ^-1 for red incident light λ = 700 nm, so this can be expressed as the above relational expression.
When calculated by substituting it into the right-hand side of (3), it is approximately 0.59, which is smaller than 1 on the left-hand side, so it satisfies relational expression (3). That is, a desired photocurrent can be obtained.

The present invention also includes those in which the conductivity types P and N of the embodiments are reversed.

[Effects of the Invention] Since the integrated photoelectric conversion element according to the present invention is configured as described above, it is possible to obtain a high open circuit voltage boosted by the number of diodes connected in series on a monolithic substrate. A photovoltaic force with voltage is obtained.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram showing diodes connected in series, Fig. 2 is a cross-sectional view showing an integrated photoelectric conversion element that realizes the diode series circuit of Fig. 1, and Fig. 3 is an explanatory diagram showing diodes connected in series.
The figure is an explanatory diagram showing the equivalent circuit of the element in Figure 2,
4 is a partial sectional view showing the first embodiment of this invention, FIG. 5 is a partial sectional view showing the second embodiment, FIG. 6 is a simplified sectional view of the main part of the embodiment, and FIG. 7 is a partial sectional view showing the second embodiment. It is an explanatory diagram showing an equivalent circuit of an example. 1, 1a...N-type first region, 2, 2a...P
Second region of type, 3, 3a...Third region of N type, 5
...Insulating film, 6...Conductive film.

Claims (1)

[Claims] 1. A semiconductor substrate of a first conductivity type, a plurality of first regions of opposite conductivity type formed at intervals on a surface portion of the substrate, and a plurality of first regions of opposite conductivity type formed in these first regions of opposite conductivity type. a second region of a first conductivity type formed on the surface of each second region; a third region of an opposite conductivity type formed on the surface of each second region; an insulating film formed on the surface of the semiconductor substrate; electrically connecting one of the regions and a second region formed on the surface thereof;
a conductive film electrically connected to a third region formed in another first region spaced apart from these, the junction depth of the first region with the semiconductor substrate is x _{j1 , and the depth of the junction of the second region with the semiconductor substrate is x j1} . The junction depth with the first region is x _j2 , the junction depth of the third region with the second region is x _j3 , the number of first regions connected to each other is n, and the absorption of incident light is When the coefficient is α,
The depths of each of the above joints are adjusted so that these satisfy the following relational expressions: 1>exp(-α・x _j1 +x _j2 /2) +nexp(−α・x _j2 +x _j3 /2)
An integrated photoelectric conversion element characterized in that x _j1 , x _j2 , and x _j3 are determined.