JPH09283811A - Manufacture of pyroelectric sensor and pyroelectric-sensor manufacturing apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a TGS crystal having a uniform characteristic in a growing direction by measuring the growing speed of the crystal in a specific axial direction, when growing the TGS single crystal in a solvent, and controlling super saturation of the solvent based on the measured value so as to maintain the growing speed of the crystal in the specific axial direction within a predetermined range. SOLUTION: Growing speed measuring means has a laser light source 3a for emitting a parallel laser beam to a crystal C, which grows in a constant-temperature chamber 1, a CCD sensor 3b and the like. A part of the parallel laser beam, emitted from the laser light source 3a, is blocked by the growing crystal C. The CCD sensor 3b detects the size of the blocked part of the laser beam so as to obtain the change of the length of the growing crystal C per unit period. The measured value is inputted into slow-cooling control means 4 which feed-back controls the speed of degradation of the temperature of a solvent L in the constant-temperature chamber 1 such that the growing speed of the crystal C stays within a predetermined range. This maintains the growing speed of the crystal in the constant-temperature reservoir 1 at a constant speed, therefore a TGB single crystal having a uniform character in a growing direction can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pyroelectric sensor manufacturing method and a pyroelectric sensor manufacturing apparatus.

[0002]

2. Description of the Related Art As a sensor for detecting optical power of infrared rays or the like, there is a highly sensitive pyroelectric sensor using a TGS (Tri-Glycine Sulfate) type single crystal. This TGS-based single crystal is doped with an amino acid, a metal ion, or another type of acid in order to improve or improve the crystal characteristics.

For example, when an amino acid is doped, the device has an internal electric field, the spontaneous polarization becomes stable and the relative dielectric becomes small, and the relative dielectric becomes small even by doping with metal ions. The Curie temperature can be controlled by doping beryllium fluoride or phosphoric acid.

Such an impurity-doped TGS type single crystal is generally produced by growing from a solution containing a component (raw material) to be a crystal and an impurity. Further, in this type of crystal growth, control is conventionally performed such that the temperature drop rate or the raw material supply rate is kept constant during crystal growth to keep the supersaturation degree of the solution constant.

[0005]

By the way, in the growth of a TGS-based single crystal, it is common to grow the single crystal in a desired crystal orientation (generally, the b-axis direction in a pyroelectric sensor). The uniformity of the crystal characteristics is important for manufacturing the pyroelectric sensor.

However, in the conventional growth method, the crystal characteristics (internal electric field, etc.) in the growth direction are often non-uniform, which reduces the usable area in the crystal when manufacturing a pyroelectric sensor. As a result, there is a problem that the yield is deteriorated.

The present invention has been made in view of the above circumstances, and a method capable of obtaining a TGS-based single crystal having uniform characteristics in the growth direction, thereby improving the yield of a pyroelectric sensor, The aim is to provide a device suitable for carrying out such a method.

[0008]

First, in the conventional growth method, the crystal characteristic in the growth direction becomes non-uniform because the supersaturation degree of the solution is controlled to be constant during crystal growth. It is considered that this is because the growth rate in the crystal axis direction (b-axis direction) is not constant and therefore the doping amount of impurities is not uniform.

Therefore, in the present invention, when a TGS-based single crystal is grown in a solution, the growth rate of the crystal in a specific axis direction is measured, and the supersaturation degree of the solution is controlled based on the measured value. By adopting a method of keeping the growth rate of the crystal in the specific axis direction within a predetermined range, the desired amount of impurities can be made uniform in the specific axis direction (b-axis direction) of the TGS series single crystal. Achieve the purpose.

An apparatus suitable for carrying out such a method is, for example, as shown in FIG. 1, a thermostatic bath 1 containing a solution L for growing a TGS type single crystal C, and a thermostatic bath 1 in the thermostatic bath 1. Means for measuring the growth rate of the crystal C in the specific axis direction during the crystal growth (laser light source 3a, CCD sensor 3b, etc.)
And means for feedback-controlling the degree of supersaturation of the solution L in the thermostat so that the growth rate of the crystal in the specific axis direction falls within a predetermined range based on the measured value (slow cooling control means 4).
May be provided.

Here, in the present invention, the growth rate of the specific axis (b axis) during crystal growth is that the crystal is uniformly doped with impurities, and if the growth rate is too slow, a good quality crystal cannot be obtained. Considering the point, 0.6mm / day ~ 1.5mm / da
y is appropriate, preferably 1.0 mm / day to 1.2 mm / day.

Further, as a method for controlling the supersaturation degree of the solution, there is a solution gradual cooling method for adjusting the temperature decrease rate of the solution or a raw material supply method for adding a solution having a higher concentration than the solution for crystal growth. Can be mentioned.

When the solution gradual cooling method is adopted, the temperature decrease rate is decreased when the crystal growth rate is higher than the specified value, and conversely, the temperature decrease rate is increased when the growth rate is smaller than the specified value. Such control may be performed.

On the other hand, when the raw material supply method is adopted, the raw material supply rate is increased or the raw material supply amount is increased when the growth rate is higher than the specified value, and the raw material supply rate is decreased when the growth rate is lower than the specified value. Alternatively, control may be performed such that the raw material supply amount is reduced.

The present invention is not limited to the case of growing a crystal in the b-axis direction, but can be applied to the case of growing a crystal in the a-axis direction or the c-axis direction.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. First, this embodiment is shown in FIG.
As shown in, a solution L containing a component to be a crystal and impurities such as amino acids is put in a constant temperature bath 1, and a crystal growth apparatus for growing a TGS-based single crystal C in the solution L is used. The example in the case of manufacturing an electric sensor is shown.

In the apparatus shown in FIG. 1, crystal growth is carried out in the desired crystal orientation (b) as shown in FIGS. 2 (A) and 2 (B).
The seed crystal C'of (axis) is attached to the lower end of the support member 2 and immersed in the solution L in the bath. Based on the seed crystal C ', the TGS single crystal C is b-axis direction It is performed by the operation of growing in the direction. A pyroelectric sensor can be obtained by subjecting the TGS-based single crystal produced by such crystal growth to predetermined processing, for example, processing such as cutting out a sensor element from the crystal and forming electrodes.

In this embodiment, the growth rate measuring means 3 and the slow cooling control means 4 are provided as shown in FIG. 1, and the growth rate of the single crystal C in the b-axis direction is controlled by the solution slow cooling method. It is characterized in that is kept within a predetermined range.

The growth rate measuring means 3 is a laser light source 3a for irradiating a crystal C growing in the constant temperature bath 1 with parallel laser light.
The laser light source 3 is provided with a CCD sensor 3b and the like arranged at a position facing the laser light source 3a with the constant temperature bath 1 interposed therebetween.
Of the parallel laser light output from a, the size of the portion blocked by the growth crystal C, that is, the length of the growth crystal C in the b-axis direction is detected by the CCD sensor 3b, and the length of the growth crystal C It is configured to calculate the change per unit time (day). In this measuring system, it goes without saying that a part or all of the wall of the constant temperature bath 1 is made of a transparent material so that the parallel laser light from the laser light source 3a to the CCD sensor 3b is not hindered.

Then, the slow cooling control means 4 takes in the measured value of the growth rate measuring means 3, and based on the measured value, the crystal growth rate is within a specified range (0.6 mm / day to 1.5 mm / day). The temperature decrease rate of the solution L in the constant temperature bath 1 is feedback-controlled so that it falls within the range.

The control is performed by decreasing the temperature drop rate when the growth rate is larger than the upper limit value of the specified range and conversely increasing the temperature drop rate when the growth rate is smaller than the lower limit value of the specified range. By such control, the rate of crystal growth in the constant temperature bath 1 can be kept constant, and as a result, it is possible to obtain a TGS-based single crystal having uniform growth direction characteristics.

A specific example will be described. Using the crystal growth apparatus shown in FIG. 1, a TGS-based single crystal doped with the amino acid L-alanine was grown at a growth rate of 0.8 mm in the b-axis direction.
When grown at a value of / day to 1.2 mm / day, a single crystal with a uniform internal electric field of 2.5 kV / cm to 5 kV / cm was obtained.

In the above embodiment, an example of the case of crystal growth by the solution slow cooling method has been shown, but when adopting the raw material supply method as the growth method, the mode as shown in FIG. 3 or 4 is adopted. The present invention can be implemented by.

First, in the embodiment shown in FIG. 3, a raw material supply tank 11 containing a solution L'having a higher concentration than the solution L in the constant temperature tank 1, a pump 12 for supplying the same, and a drive control means 1 are provided.
3 is provided, and the discharge amount of the pump 12 is feedback-controlled based on the measurement value from the growth rate measuring means 3,
The inflow amount of the solution L ′ into the constant temperature bath 1, that is, the raw material supply rate is adjusted. In the case of this example, when the growth rate is higher than the upper limit value of the specified range, the discharge amount of the pump 12 is increased to increase the raw material supply rate, and conversely, when the growth rate is smaller than the upper limit value of the specified range, the pump 12 is increased.
The control is performed such that the discharge amount of is reduced to reduce the raw material supply rate.

On the other hand, in the embodiment shown in FIG. 4, the discharge amount of the pump 12 is constant, and the supply amount of the raw material is controlled by adjusting the concentration of the solution L'supplied to the constant temperature bath 1. .

That is, in the embodiment shown in FIG. 4, the temperature control means 1 for feedback-controlling the temperature of the solution L'in the raw material supply tank 11 based on the value measured by the growth rate measurement means 3.
4 is provided, and when the growth rate is higher than the upper limit of the specified range, the temperature of the solution L'in the raw material supply tank 11 is increased and the concentrated solution L'is supplied to the constant temperature bath 1. When the growth rate is larger than the upper limit of the specified range, the temperature of the solution L'in the raw material supply tank 11 is lowered to reduce the supply amount of the raw material.

As the growth rate measuring means used in the present invention, in addition to the method of capturing parallel laser light with a CCD sensor as shown in FIG. 1, for example, a method of capturing crystal growth with a reading telescope, a CCD camera, or the like. Alternatively, a method may be used in which the crystal growth is photographed and the growth rate is obtained by image processing. Further, instead of such an optical method, for example, a measuring method using ultrasonic waves may be adopted.

[0028]

As described above, according to the present invention,
When growing a TGS-based single crystal used for a pyroelectric sensor, the growth rate of the crystal is kept within a predetermined range so that the doping amount of impurities in the crystal in the specific axis direction becomes uniform. A single crystal having various characteristics can be obtained. As a result, the usable area in the crystal is increased, and as a result, the yield of the pyroelectric sensor is improved as compared with the conventional one.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an embodiment of the present invention.

FIG. 2 is a diagram showing a growth state of a TGS-based single crystal.

FIG. 3 is a configuration diagram of another embodiment of the present invention.

FIG. 4 is a configuration diagram of still another embodiment of the present invention.

[Explanation of symbols]

 1 Constant Temperature Tank 2 Support Member 3 Growth Rate Measuring Means 3a Laser Light Source 3b CCD Sensor 4 Slow Cooling Control Means 11 Raw Material Supply Tank 12 Supply Pump 13 Drive Control Means 14 Temperature Control Means

Claims (3)

[Claims] 1. A method for producing a TGS-based single crystal by growing a crystal in a solution and obtaining a pyroelectric sensor from the single-crystal, wherein when the TGS-based single crystal is grown in the solution, a specific axis direction of the crystal is obtained. A method for manufacturing a pyroelectric sensor, characterized in that the growth rate in the specific axis direction of the crystal is maintained within a predetermined range by controlling the growth rate of the crystal on the basis of the measured value. 2. In the growth of the TGS-based single crystal, the growth rate in a target crystal orientation is 0.6 mm / day to 1.5 mm / da.
The method for manufacturing a pyroelectric sensor according to claim 1, wherein the pyroelectric sensor is maintained in the range of y. 3. A thermostatic bath containing a solution used for growing a TGS-based single crystal, a means for measuring the growth rate of a crystal in a specific axis direction during crystal growth in the thermostatic bath, and the measured value based on the measured value. A device for manufacturing a pyroelectric sensor, comprising means for feedback-controlling the degree of supersaturation of a solution in a thermostat so that the growth rate of crystals in a specific axis direction falls within a predetermined range.