JPS5936218B2 - Method for improving linearity of dual surface lateral photodetector for position determination - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for improving linearity in a photodetector that uses an electric signal to detect the position of a point of incidence of a light beam on a detection surface of the detector, wherein the photodetector , a semiconductor board, two resistance layers each covering one side of this semiconductor board, a p-n junction separating these two resistance layers, and a pair of electrodes provided on each resistance layer. the electrodes are positioned such that each pair defines two opposite sides of a square;
The squares define two portions of the resistive layer located opposite and parallel to each other.

Lateral photodetectors of the type outlined above are used for non-contact analysis of the position of stationary or moving objects in two and three dimensions, by locating a light source on the object to be located; Two or more photodetectors are used to simultaneously detect a light source and determine the position and motion of an object in space and time.

The term lateral is used here because the impulse generated on the detector by the light beam is divided into two components, each of which is transmitted laterally along the detector surface to the electrode. However, conventional lateral photodetectors have the disadvantage that the relationship between the output signal and the positional coordinates is non-linear, especially near the edges of the detection surface defined by the electrodes. For this reason, when linearity is strictly required, there is an inconvenience that the sensor must be used only in a small portion of the detection surface arranged symmetrically with respect to the center of the detection surface where the edge effect is small. For example, by giving the electrodes a special geometry, and more particularly by extending the ends of the electrodes beyond and across the opposite electrodes, to some extent the so-called periphery Although this effect can be eliminated, for this method to have any practical effect, it is necessary to make the electrodes long, which tends to make the detector unduly large compared to the effective surface of the detector. Additionally, the area of the p-n junction and the circumference of the semiconductor board increase, resulting in an undesirable increase in leakage current through the p-n junction and the periphery, resulting in increased noise and the need for more material. Of course, this is necessary. It is therefore an object of the present invention to provide a method that eliminates the above-mentioned drawbacks of conventional lateral photodetectors and improves the linearity of the detector.

To achieve this objective, the method for improving the linearity of a dual-surface lateral photodetector according to the present invention uses electrical signals from two pairs of electrodes to determine the position of the human irradiation point on the detection surface of the photodetector. and forming a semiconductor substrate substrate layer, adding two doped resistive layers covering opposite sides of each of the substrate layers, and disposing a p-n junction between the two doped resistive layers; further providing two pairs of electrodes, each pair of the two pairs of electrodes being set on each of the doped resistive layers, said pairs of electrodes being shaped and arranged to define boundaries of a parallelepiped; The parallelepiped surrounds a respective portion of each of the doped resistive layers, and such that one pair of electrodes are on opposite sides of the parallelepiped square on the resistive layer surface and the other pair of electrodes are on opposite sides of the parallelepiped square on the resistive layer surface. The electrodes are on opposite sides of the parallelepiped square on the surface of the other resistive layer, and thus the two pairs of electrodes are arranged at right angles to each other in the surface of the photodetector. A method for manufacturing a double-sided semiconductor-type lateral photodetector having a conductive structure, wherein the doped resistive layer surrounds the electrode and surrounds a parallelepiped square on a surface of the resistive layer. The pn junction is electrically insulated from the doped resistive layer disposed within the square of the parallelepiped by removing the entire portion and the pn junction.

A preferred and simple embodiment of the invention is characterized in that the division is effected by etching, each etched area extending substantially in a square pattern adjacent to an electrode and the plane defined by said electrode. It is something to do. ``Next, the method for improving the linearity of a double-sided lateral photodetector according to the present invention will be described in detail below with reference to the accompanying drawings.

” will be added. As shown in FIGS. 1 and 2, the detector according to the invention has a semiconductor plate 1 made of impurity-mixed silicon, a so-called wafer.

Due to the special manufacturing method and the difficult working nature of the fragile wafer, semiconductor boards of this type are almost exclusively made in the form of a disk. On each side of the semiconductor board 1, there are resistive layers 2 and 3, respectively.
are arranged. Although the resistance value depends on the method of use, the usual value is 10 to 200 Ω-m. The resistive layers are produced by doping, and for one layer 2 there is a p-n junction 1? at the "transition point" between this layer and the semiconductor body. Each resistive layer 2, 3 has a . ← Pairs of elongated and parallel electrodes 4, 5 and 6, ? The opposing sides of the electrodes extend along two opposing sides of one square, and the opposing sides of another pair of electrodes extend along the other two opposing sides of the square. , such that this square surrounds the ideal effective detection surface 8. Electrodes 4, 5 and 6,? are each connected to one subtractor (not shown). 10, the energy of the beam causes a photocurrent to flow through the p-n junction.Since the p-n junctions are biased in opposite directions via electrodes 4, 5 and 6, 1, respectively, the resistance layer 2 , 3, each of the electrode pairs 4, 5 and 6, 7, and an external electronic device (not shown)
Only the circuit consisting of is closed. Depending on the position on the detection surface 8 where the light beam 9 is incident, different currents flow through different electrodes.
This provides a relatively linear indication of the entrance position 10 on the X and Y coordinate axes of the detector. In order to eliminate the aforementioned non-linear edge effects that normally occur in detectors of this type, the areas 11, 12 of each resistive layer 2 and 3 located within the surface defined by the squares described above are According to the invention, an area 13 of the resistive layer located outside the square
, 14, and to perform this partitioning each resistive layer 2,
Etching areas 15 and 16 are provided on 3.

p-n junction 1? The portions of the resistive layer 2 adjacent to the resistive layer 2 are etched deep enough that the etched area extends beyond the p-n junction. Areas 13, 1 of the resistive layer 2, 3 located outside the ideal detection surface 8 defined by the squares described above
By preventing current from flowing through 4, improved linearity is obtained. Preferably, each etching area 15, 16, carried out in a so-called mesa type, is in the form of a closed ring, surrounding between the ends of a pair of opposing electrodes and the outside of the electrodes, but not in complete contact with the electrodes. It is preferable not to do so.
The detection surface 8 surrounded by the electrodes 4, 5 and 6, 1 is insulated from the remaining parts 13, 14 of the resistive layer by etching, so that the electric field image of the detection surface 8 differs from that of conventional techniques of this type. Significantly improved linearity is obtained compared to the detector, and the relationship between the output signal of the detector and the incident position 10 of the incident light 9 on the detection surface shows extremely good linearity. Additionally, the area of leakage current flowing through the p-n junction is reduced, resulting in a reduction in the total leakage current flowing through the detector. Edge effects at the periphery of the detector are reduced in this way as well, without the need for other additional devices. By using the method for improving the linearity of a dual-plane lateral photodetector according to the present invention, the accuracy of non-contact analysis of the position of stationary or moving objects can be significantly increased.

The invention is not limited to the embodiments described and illustrated above, but various modifications are possible within the scope of the claims.

For example, the resistance layers 2 and 3 located outside the detection surface and the p-
Etching the entire area of the n-junction 17 is also effective. It is also possible to carry out the partitioning by mechanical means, for example by blasting. Of course, the invention is also applicable to similar types of detectors made of other materials. For detectors that are etched at the periphery,
To reduce leakage currents, this peripheral etching may be replaced by an etched area according to the invention.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of a photodetector that implements the method for improving linearity of a lateral photodetector according to the present invention, and the thickness of the detector is enlarged for convenience of explanation. The figure is a sectional view taken along the line - in FIG. 1... Semiconductor board, 2, 3... Resistance layer, 4, 5, 6, 7... Electrode, 8... Sensing surface, 9... ...ray, 10... point of incidence,
11, 12, 13, 14... area, 15, 16
...Etching area, 1?・・・・・・p-
n-junction.

Claims (1)

[Claims] 1. The position of the incident point on the detection surface of a photodetector is detected using electrical signals from two pairs of electrodes, and a semiconductor substrate base layer is formed and each of the base layers is Two doped resistive layers covering opposite sides are added, a p-n junction is placed between the two doped resistive layers, and two pairs of electrodes are provided, each pair of the two electrodes being doped. disposed on each of the resistive layers, the electrode pair being shaped and arranged to define the boundaries of a parallelepiped, the parallelepiped surrounding a respective portion of each of the doped resistive layers; and whereby one pair of electrodes are on opposite sides of the parallelepiped square on the surface of the resistive layer and another pair of electrodes are on opposite sides of the parallelepiped square on the surface of the other resistive layer. In a method of manufacturing a semiconductor-type double-sided lateral photodetector with improved linearity, the two pairs of electrodes are arranged at right angles to each other in the plane of the surface of the photodetector. , by removing the entire portion of the doped resistive layer and the p-n junction surrounding the electrode and surrounding the parallelepiped square on the surface of the resistive layer. A method for improving the linearity of a double-sided lateral photodetector for position determination, characterized in that a portion between a doped resistive layer arranged in a square and a p-n junction is electrically insulated. 2. The position-defining double-sided lateral light according to claim 1, wherein the portion to be removed substantially extends in a square contour adjacent to the electrode and the surface defined by the electrode. Detector linearity improvement method. 3. A method for improving the linearity of a dual surface lateral photodetector for position determination according to claim 1 or 2, characterized in that the removal is achieved by etching. 4. A method for improving the linearity of a dual surface lateral photodetector for position determination according to claim 1 or 2, characterized in that the removal is achieved by a plasto method.