Detector circuit with a semiconductor diode operating as a detec

Active solid-state devices (e.g. – transistors – solid-state diode – Responsive to non-electrical signal – Electromagnetic or particle radiation

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Details

257458, 257463, 257465, 330250, 330269, 330277, 330307, H01L 31075, H01L 31105, H01L 31117

Patent

active

055192475

DESCRIPTION:

BRIEF SUMMARY
TECHNICAL FIELD

The present invention relates to a detector circuit with a semiconductor diode operating as a detector and with an amplifier circuit integrated with the diode.


BACKGROUND ART

By "a semiconductor diode operating as a detector" is meant in this application a semiconductor diode which is intended for and used as a radiation detector. The most common use is as a photodiode, that is, as a detector for optical radiation inside or outside the visible wavelength range. A diode of the intended kind operates under reverse bias. At the pn junction of the diode a depletion layer is then generated. Incident radiation generates electron-hole pairs in the depletion layer and thereby gives rise to a current through the diode, and the magnitude of this current is a measure of the intensity of the radiation.
Photodiodes are usually designed as vertical pin diodes, that is, with a relatively highly doped p-conducting layer at one surface of a semiconductor body, a relatively highly doped n-conducting layer at the opposite surface, and between these layers a weakly doped layer, in which the depletion layer is formed. The p-layer is provided with an anode contact and the n-layer with a cathode contact. Diodes of this kind will have a homogeneous depletion layer and thus good detection properties--the sensitivity is the same independently of where on the surface of the diode the radiation is caused to become incident. However, they must be designed with a relatively large area to attain the necessary sensitivity, and this results in a high self-capacitance and hence a low speed of operation.
Further, lateral photodiodes are known. In such, however, it has not been possible to attain the homogeneous depletion layer which the vertical diodes exhibit, and these diodes have therefore exhibited inferior detection properties.
To obtain good properties these diodes have been made of high-resistance and very high-quality (defect free) silicon, typically with a resistivity of 500-1000 ohmcm.
It is further known to design detector diodes with integrated amplifiers. The diode and the amplifier are then produced in an epitaxial silicon layer arranged on a highly doped substrate. One of the contact regions of the diode is then produced at the same surface as the amplifier, and the other contact region of the diode consists of the substrate layer. Thus, the diode is made as a vertical diode, and its depletion layer is formed in the epitaxial layer. Such a layer is well suited for amplifier circuits, for example, of CMOS type, but because of the lower silicon quality it provides an inferior function of the detector diode.


SUMMARY OF THE INVENTION

The invention aims to provide a detector circuit of the kind described in the introductory part of the description, in which a high speed of action and optimal detection properties are obtained and which can be produced by a simple and hence economical manufacturing process with a good yield.


BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described in greater detail in the following with reference to the accompanying FIGS. 1-4.
FIG. 1 shows an embodiment of a circuit according to the invention, wherein FIG. 1a shows a section through the circuit and FIG. 1b a view of that surface of the semiconductor body where the diode and the amplifier circuit are produced.
FIG. 2 shows in more detail a section through the diode shown in FIG. 1.
FIG. 3 shows an example of how the amplifier circuit may be designed.
FIG. 4 shows an alternative embodiment of the invention.


DETAILED DESCRIPTION OF THE INVENTION

FIG. 1a and FIG. 1b show an embodiment of a detector circuit according to the invention. FIG. 1a shows a section through that semiconductor wafer in which the detector circuit is produced, and FIG. 1b is a view of the upper surface of the semiconductor wafer according to FIG. 1a. The circuit is produced in a semiconductor wafer 1 of high-quality silicon material. For that purpose it is suitable to use silicon produced by the so-called floating zone method, by means of which

REFERENCES:
patent: 5101253 (1992-03-01), Mizutani et al.
patent: 5162887 (1992-11-01), Dierschke
patent: 5239193 (1993-08-01), Benton et al.
patent: 5382824 (1995-01-01), Popovic

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