JPH028702A - Semi-insulating thickness measuring device - 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 Field of the Invention The present invention relates to an apparatus for non-contact measurement of the thickness of semi-insulators, such as GaAs wafers.

Conventional technology contact type AI1 constant instruments, such as micrometers, are
It is not suitable for measuring brittle materials such as aAs. Therefore, a laser method, which is a non-contact measurement device,
In other words, a laser beam is projected onto the wafer, the reflected light image is formed on an image sensor, and measurement is performed using trigonometry.
Alternatively, there is a capacitive method, in which the reference bed 10 and the sensor 1 are opposed to each other at a distance as shown in FIG. A device that calculates the change in capacitance due to change is used.

Problems to be Solved by the Invention However, the above-mentioned laser method has a problem in that it may change the physical properties of the object to be measured upon which it is irradiated, and the objects to which it can be applied are limited. In addition, the overall configuration is complicated,
In contrast, the capacitive method does not have the above problems.However, in this case, when the object to be measured is a semi-insulator, the object to be measured is the reference floor 10.
Since the output of the sensor 1 changes depending on the position in the space between the sensor 1 and the sensor 1, the occurrence of errors due to misalignment of the insertion position is unavoidable.

Method for Solving the Problems The present invention makes the measured thickness independent of the insertion position of the object to be measured. In other words, this invention was made by focusing on the fact that the relationship between the insertion position and the sensor output changes monotonically and can be considered as a substantially straight line. It consists of two capacitance sensors, and a processing section that calculates the average value of the outputs of both capacitance sensors.

■ In the above, as shown in Fig. 1, the distance between the first and second capacitance sensors 1.2 is d, and the object to be measured 3 with a thickness of t inserted between them and the second capacitance sensor 1. If the distance between the capacitance sensors 2 is y, the outputs A and B of the first and second capacitance sensors 1.2, which are selectively taken out via the spinner 4.4, have a thickness of t. In addition, as shown in Figure 2, they increase and decrease monotonically as y increases, and y becomes (d-t).
/2 state, that is, when the object to be measured 3 is located at the center of the sensor 1.2, both outputs A and B match and intersect.

Therefore, if the object to be measured 3 is inserted between both sensors 1.2 and the outputs of the first and second sensors 1 are taken out alternately and selectively in this state, each output will be as shown in FIG. Output Aa, Ba at the insertion position at that time, e.g. point a
This is sent to the processing section, and an output corresponding to the average value of both outputs is formed.

Therefore, if one of these outputs Aa and Ba becomes large, the capacity becomes small, and the average value thereof becomes approximately constant regardless of the insertion position y. The thickness E of the object is found.

In FIG. 3 of the embodiment, iW'! The four-capacitance type first and second sensors 1.2 are arranged facing each other at a predetermined interval, and the object to be measured 3 is inserted between them. 10 is a processing unit connected to the first and second sensors 1.2, and each sensor 1.2 is connected to a corresponding position detection module 11.12. This position detection monoyl 11.12 is
As shown in Figure 4, an alternating current signal C1 is applied to the sensor, and the capacitance C between both sensors 1 and 2 (and the capacitance C5 of the reference capacitor are compared to correspond to the dielectric constant change between the sensors 1 and 2). It is an element that forms an output C6, that is, an output corresponding to the thickness of the object to be measured 3 inserted therein, and further extracts it as a DC voltage through a current filter (not shown), and the DC voltage is As shown in FIG. 3, after being digitally encoded via each corresponding A/D converter 13, 14, it is sent to a calculation r315.

The arithmetic unit 15 selectively sends operation/non-operation commands to the position detection module 11.12, and also inputs commands from the position detection monolayer 11 or 12 during operation via the A/D converter 13 or 14. The outputs are sequentially and alternately read and the average value is calculated. Finally, based on the relationship between the average value and thickness, which has been calibrated in advance using a reference body made of the same material as the book being measured, the average value is linearized and output externally for display, recording, etc. .

In the above, when the object to be measured 3 is inserted into the space formed by the first and second sensors 1.2, the position detection monoyls 11.12 are alternately put into an operating state, and in each operating state, the As shown in Figure 2, the output A is related to the thickness of the book 3 to be measured and is also related to the insertion position.
The amount corresponding to B is detected and read into the calculation section 15.

Then, the itching section 15 calculates the average value of both read values, and then the average value is subjected to a predetermined linear alignment X process and output.

In addition, although the above embodiment illustrated the case where the position detection module is selectively operated, as shown in FIG.
The sensors 1.2, ie the electrode parts, may be selectively switched alternately and a common position detection module may be used.

The effects of the invention are as described above, and since the present invention alternately and selectively operates two capacitance sensors placed facing each other and obtains the average value of both outputs, The change in output due to the change in the insertion position of the semi-insulator is canceled out, and a measured value corresponding to the thickness independent of the insertion position can be obtained.

2: capacitive sensor : Suinna

Claims (1)

[Claims] 1. A semi-insulated device consisting of two capacitance sensors that are placed facing each other with a gap between them and are operated alternately and selectively, and a processing unit that calculates the average value of the outputs of both capacitance sensors. Body thickness measuring device.