JP2556335B2 - InSb single crystal wafer of composite substrate for electromagnetic transducer-Method of measuring thickness - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for processing a composite substrate in which an InSb single crystal wafer is bonded onto a substrate used for an electromagnetic conversion element such as a Hall element or a magnetoresistive element, In particular, the thickness of the InSb single crystal wafer that was once bonded to the substrate was measured with high accuracy by applying the DC four-terminal method that has been conventionally used to measure the resistance and resistivity of semiconductors during the manufacturing process. Adhesive resin layer for bonding, which can be processed with high accuracy regardless of thickness and thickness variation, and can obtain a composite substrate in which InSb single crystal wafers with a uniform required thickness are bonded and arranged. The present invention relates to a method of processing a composite substrate for a device.

Conventional technology InSb, which is known as a semiconductor with the highest electron mobility, is an electromagnetic conversion element that uses the Hall effect and magnetoresistive effect.
There is often used a structure in which the above are arranged in various patterns on a required substrate.

As a method of disposing InSb on a substrate, a method of bonding an InSb single crystal wafer on the substrate and a method of depositing an InSb film on the substrate to a required thickness by vapor deposition are known.

In either arrangement method, In arranged on the substrate
The thickness of Sb greatly affects the electromagnetic conversion characteristics.

In addition, after bonding the InSb single crystal wafer to the substrate, the thickness is set to a required thickness by processing, and further, in the etching process when the InSb single crystal wafer is divided into a plurality of elements having a required pattern, the InSb single crystal wafer is also processed. The thickness variation is a factor that causes device failure due to overetching.

In any case, in order to obtain the device having high characteristics, it is necessary to accurately measure and control the thickness of the InSb single crystal wafer in the manufacturing process.

On the other hand, when InSb is vapor-deposited on a substrate and deposited to a required thickness, by measuring the vapor deposition rate in advance, it is possible to control to a predetermined InSb thickness by adjusting the film formation time. A crystal oscillation type film thickness meter etc. is attached to the
It can be measured in units of μm.

Therefore, after the deposition of the InSb film, there is an advantage that there are few occurrences of element defects due to over-etching during the manufacturing process and variations in the electromagnetic conversion characteristics of the elements.

However, the electron mobility of the InSb film formed by the vapor deposition method is as low as half the electron mobility of the InSb single crystal wafer (bulk material), which satisfies the recent demand for higher performance in terms of device characteristics. It was difficult to do.

On the other hand, with the structure in which the InSb single crystal wafer is bonded onto the substrate (bulk method), the high electron mobility originally possessed by InSb can be effectively realized as described above.

However, it is unavoidable to use an adhesive resin for bonding the InSb single crystal wafer to the substrate, and the presence of the adhesive layer, which has a large variation in thickness, makes it possible to accurately measure the thickness of the InSb single crystal wafer in the manufacturing process by the conventional measurement method. It was difficult to measure, and it was not possible to stably obtain the preset electromagnetic conversion characteristics.

Problems to be Solved by the Invention Conventionally, it is difficult to directly measure the thickness of an InSb single crystal wafer once bonded to a substrate during a manufacturing process, and an adhesive resin is used between the substrate and the InSb single crystal wafer. With the intervening state, the thickness of the InSb single crystal wafer was only estimated by using a known step measuring device with the upper surface of the substrate as a reference surface.

That is, conventionally, the In
The thickness measurement accuracy of the Sb single crystal wafer itself is affected.For example, in the case where the adhesive resin layer is tapered in one direction, the upper surface of the substrate is used as the reference surface, so after polishing the surface,
The thickness of the InSb single crystal wafer is partially different, in other words, the thickness gradually decreases corresponding to the taper of the adhesive resin.

In addition, if the adhesive resin is thicker than necessary, the InSb single crystal wafer will be processed thinner than the setting in the same manner. There is a problem that the value is not shown and the output characteristic is deteriorated.

In view of such a present situation, the present invention is a structure that can effectively realize the high electron mobility originally possessed by InSb, that is, a composite substrate for an electromagnetic conversion element comprising a structure in which an InSb single crystal wafer is bonded onto the substrate. InSb that constitutes the substrate
A method of processing a composite substrate for an electromagnetic conversion element that enables the provision of an electromagnetic conversion element having stable electromagnetic conversion characteristics by measuring and managing the thickness of a single crystal wafer with high accuracy at any time during the manufacturing process. And

Means for Solving the Problems The present invention has variously studied the thickness measurement method of an InSb single crystal wafer in a state of being bonded to a substrate, and as a result, a DC voltage which has been conventionally used for measuring the resistance and resistivity of semiconductors Using the terminal method, the specific resistance (ρ) of the InSb single crystal wafer whose surface has been subjected to strain-free processing in advance is obtained, and after applying both ends to the strain-free processing to reduce the thickness, the InSb single crystal wafer in the DC 4-terminal method is used. By finding the applied current and the detected voltage to the sensor, we have found that it is possible to measure with high accuracy at any time during processing, and by using this measurement method, processing can be performed with high accuracy regardless of the adhesive resin layer thickness and thickness variation. The present invention has been completed by discovering that a composite substrate can be obtained which can be processed and in which InSb single crystal wafers having a uniform required thickness are bonded and arranged.

That is, the present invention is a method of processing a composite substrate for an electromagnetic conversion element, in which an InSb single crystal wafer is bonded onto a substrate via an adhesive resin, in which the specific resistance (ρ) of the InSb single crystal wafer is previously measured before bonding to the substrate. Insb single crystal wafer with strain-free processing on the end surface of the bonding surface of the substrate was bonded to the substrate via an insulating adhesive resin to form a composite substrate. The other end surface of the crystal wafer was subjected to strain-free processing to reduce the thickness, and the applied current (I) to the InSb single crystal wafer in the DC four-terminal method and the detection voltage (V) of the measuring probe were obtained, The thickness (t) of the InSb single crystal wafer itself was measured based on the above formula regardless of the thickness of the adhesive resin layer, and further, the other end face of the InSb single crystal wafer was subjected to strain-free processing again based on the measured thickness value. By reducing the thickness of the InSb single crystal wafer to a uniform predetermined thickness.

Operation The processing method of the present invention and its operation will be described in detail with reference to the drawings. FIG. 2 is a perspective explanatory view of a composite substrate for an electromagnetic conversion element showing application of the DC four-terminal method to an InSb single crystal wafer.

In FIG. 2, an InSb single crystal wafer (2) having a thickness (t) is bonded onto a substrate (1) via an adhesive resin (3) made of an insulating epoxy resin.

Further, on the InSb single crystal wafer (2), four measuring probes (4) are in contact with each other at regular intervals.

If the relationship (S) between the intervals (S) of the four measuring probes (4) arranged at equal intervals and the thickness (t) of the InSb single crystal wafer is S >> t, the InSb single crystal wafer (2) The specific resistance (ρ) is obtained by the following formula by the DC four-terminal method.

However, I: Current applied to the InSb single crystal wafer V: Detection voltage of the measuring probe The thickness (t) of the InSb single crystal wafer is Can be obtained at

Where, the resistivity of the InSb single crystal wafer (ρ)
Is a sliced InSb ingot manufactured by the pulling method in advance, after removing the processing strain by etching,
That is, a known measurement method, for example, a DC four-terminal method or any other method can be adopted in a state where there is no processing distortion, and the measured value is substituted as an initial value.

Therefore, in the present invention, when a work-affected layer is present on the surface of an InSb single crystal wafer, its resistivity (ρ) is different from the previously measured resistivity (ρ) inherently possessed by the InSb material, and the accuracy is It becomes difficult to measure good thickness.

Therefore, it is necessary to finish both sides of the InSb single crystal wafer by strain-free processing. As the strain-free processing, a known mechanochemical polish is preferable, and after performing another known polishing process, a mechanochemical polish may be used to form a non-strained surface.

Further, (I) and (V) in the equation can be measured by the measurement system of the DC four-terminal method shown in FIG. 2, but in order to obtain these values accurately, the InSb single crystal wafer and the substrate are It is necessary to ensure insulation, and it is necessary to interpose a so-called insulative adhesive resin such as insulative epoxy resin between the wafer and the substrate for bonding.

Furthermore, it is desirable to appropriately select the material of the probe used for adopting the DC four-terminal method, the current applied to the probe spacing, etc. according to the thickness of the InSb single crystal wafer.

By substituting (ρ), (V), and (I) obtained by setting various conditions in advance according to such conditions,
The thickness of an InSb single crystal wafer can be measured with an accuracy of 0.1 μm.

Regarding this measurement, since the formula is a relational formula that can be applied to a wafer having an infinite spread, when measuring a wafer having a finite outer diameter dimension, the effect and correction of the end portion occur especially at the wafer outer peripheral portion. It is effective to apply within 10mm from the outer circumference.

As explained above, InSb single crystal wafers that have been bonded to the substrate while ensuring insulation and finished on both sides by strain-free processing are highly accurate by the DC four-terminal method while being bonded to the substrate. Since it is possible to measure the thickness at any time, the thickness can be measured at any time during the manufacturing process, and the predetermined surface of the wafer can be subjected to strain-free processing again based on the measured value. (EN) It is possible to provide a composite substrate for an electromagnetic conversion element, which is formed by bonding InSb single crystal wafers having a uniform predetermined thickness.

Example Hereinafter, a process of measuring and controlling the thickness of an InSb single crystal wafer using the processing method of the present invention to manufacture a composite substrate for an electromagnetic conversion element will be described.

1A to 1E are explanatory views showing a manufacturing process of a composite substrate for an electromagnetic conversion element to which a processing method according to the present invention is applied.

A tungsten carbide material was used as the probe material used in the DC four-terminal method shown in FIG. 2, and the probe interval was set to 1 mm.

First, as shown in FIGS. 1A and 1B, the outer diameter 60 is reduced by applying strain-free processing to the end surface (bottom surface in the drawing) on the substrate bonding surface side.
mm, 0.5 mm thick InSb single crystal wafer (2) with an outer diameter of 76 m
A glass substrate (1) having a thickness of 1 mm and a thickness of 1 mm was bonded via an insulating epoxy resin (3) to form a composite substrate.

The resistivity (ρ) of the InSb single crystal wafer was 4.6 × 10 ^-3 when measured without bonding strain before bonding.
It was Ω · cm.

At the time of the joining, the insulating epoxy resin (3) layer is
As shown in FIG. B, the taper shape which is inclined on one side was formed.

Next, as shown in FIG. C, the InSb single crystal wafer (2) bonded to the glass substrate (1) is subjected to strain-free processing by mechanochemical polishing, and the InSb single crystal wafer is processed from the upper surface of the glass substrate (1). The thickness up to the upper surface of (2) is 10 μm
It was processed so that

Here, as shown in FIG. C, the thickness of the InSb single crystal wafer was measured by the DC four-terminal method. As a result, the thickness of the A portion (15 mm inside the left end portion from the outer periphery) in the figure was 9 μm, and the B portion (the central portion).
Had a thickness of 7.5 μm, and the thickness of the C portion (15 mm inner right end from the outer periphery) was 6 μm.

 The applied current (I) at this time was 10 mA.

In order to cope with such variation in thickness, in the mechanochemical polishing apparatus, the composite substrate, the polisher, or the facing angle of the both are adjusted, and the upper surface of the InSb single crystal wafer (2) is again subjected to strain-free processing to reduce the thickness, and then again. When the thickness was measured by the DC four-terminal method similar to the above, as shown in Fig. D, it was 3 μm at any position of A, B and C.
It was possible to obtain an InSb single crystal wafer (2) having a thickness of.

InSb single crystal wafer with uniform and required thickness (2)
Then, a photo-etching process was performed on the substrate to form it into a plurality of elements (5) (see FIG. 1E).

Further, a short circuit electrode (not shown) of Cu was provided between a plurality of InSb single crystal elements (5), and the elements and electrodes were connected in series to form a magnetoresistive element, and various characteristics were measured. It was possible to obtain good characteristics close to the preset logical value.

Similarly, when a large number of composite substrates were prepared, FIG.
Without adjusting the thickness of the epoxy resin (3) layer as shown in the figure, the thickness of the InSb single crystal element is uniform and has a predetermined thickness despite the fact that the thickness of the resin (3) layer is uneven or fluctuates. In the electromagnetic conversion element using the composite substrate,
There is no element defect or element variation, and the output characteristics are higher than those of the vapor deposition type element, and the bulk type element, which has been conventionally poor in yield, can now be actually produced with good yield and low cost.

EFFECTS OF THE INVENTION As described above, the processing method of the present invention is such that the InSb single crystal wafer arranged on the substrate is subjected to strain-free double-sided processing, and an insulating adhesive resin is interposed between the substrate and the electromagnetic field. As long as it is a composite substrate for a conversion element, the substrate material may be a non-magnetic substrate such as glass, sapphire or Al ₂ O ₃ , a soft magnetic substrate such as ferrite / pure iron, a hard magnetic substrate such as a cast magnet or a sintered magnet. Similarly, in the composite substrate using the known substrate material described in (1), the absolute thickness of the InSb single crystal wafer can be directly measured during the process of being bonded to the substrate with an accuracy of 0.1 μm.

Usually used for Hall elements, magnetoresistive elements, etc.
The InSb element has a thickness of about several μm to 10 μm, but in the processing method of the present invention, if the thickness is 500 μm or less, while measuring with almost the same measurement accuracy,
Can be processed.

For example, when the processing method of the present invention is applied by using the mechanochemical polishing method, once the both surfaces of the wafer are subjected to the strain-free processing, the accurate thickness can be measured at any time, and the processing / correction can be performed again based on the measured value. By doing so, it can be processed according to the set value, so only the InSb element that exhibits stable electromagnetic conversion characteristics has an absolute thickness of 10 μm and a parallelism of 1
It is possible to achieve extremely high-precision polishing processing of μm or less.

Therefore, it is possible to greatly reduce the thickness defect of the InSb element and provide an electromagnetic conversion element having stable electromagnetic conversion characteristics.

Further, by adopting the processing method of the present invention, an expensive InSb single crystal can be produced with a high yield, so that the price of the electromagnetic conversion element can be reduced.

[Brief description of drawings]

1A to 1E are explanatory views showing a manufacturing process of a composite substrate for an electromagnetic conversion element to which a processing method according to the present invention is applied. FIG. 2 is a perspective explanatory view of a composite substrate for an electromagnetic conversion element showing application of the DC four-terminal method to an InSb single crystal wafer. 1 ... Substrate, 2 ... InSb single crystal wafer, 3 ... Epoxy resin, 4 ... Measuring probe.

Claims (1)

(57) [Claims] 1. A method of processing a composite substrate for an electromagnetic conversion element, comprising an InSb single crystal wafer bonded on a substrate via an adhesive resin, wherein the resistivity (ρ) of the InSb single crystal wafer is previously measured before bonding to the substrate. Obtained in the absence of processing distortion, and then the InSb single crystal wafer with the end surface of the substrate bonding side subjected to strain-free processing was bonded onto the substrate via an insulating adhesive resin to form a composite substrate, and then the InSb single crystal was formed. The other end surface of the wafer is subjected to strain-free processing to reduce the thickness, and the applied current (I) to the InSb single crystal wafer and the detection voltage (V) of the measuring probe in the DC four-terminal method are obtained, and the adhesion is performed based on the following formula. The thickness (t) of the InSb single crystal wafer itself is measured regardless of the resin layer thickness, and the other end face of the InSb single crystal wafer is again subjected to strain-free processing to reduce the thickness based on the measured thickness value. Make InSb single crystal wafer uniform thickness A method of processing a composite substrate for an electromagnetic conversion element, comprising: