JP2002071601A - Sample heater for thermoelectric measuring instrument - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a sample from being irradiated with radiant heat from a heat source and to prevent thermoelectric measurement from being affected by a current flowing through a heater by disposing a conductive heater container on the back side of the sample in a thermoelectric measuring instrument. SOLUTION: The conductive heater container 50 comprises a cylinder part 51 and a flange 52. An upper end of a conductive bellows 70 is fixed on the flange 52. Flat panel heater elements 54 and 56 are housed within the cylinder part 51. The container 50 is fixed to an under surface of a substrate 12 of a sample assembly 10 via an electrically insulating heat transfer sheet 68. Since the container 50 is positioned on the back side of the substrate 12 as viewed from the sample 14, radiant heat from the container 50 does not directly irradiate the surfaces of the sample 14. The container 50, the bellows 70, a lower plate 82, and a tube 84 are electrically connected to each other, thus forming an electrostatic shield. Since the heater elements are outside the shield, electromagnetic noises emitted from the heater elements and from their wiring are cut off by the shield.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sample heating device of a thermoelectric measuring device for measuring the electrical characteristics of a sample by changing the temperature of the sample. As a typical method for measuring the electrical characteristics of a sample by changing the temperature of the sample, there is a TSC (Thermally Stimulated Current) measurement method. In addition, DEA (Dielectric
Analysis: Thermal relaxation measurement), DLTS (Deep Level Trans
Spectroscopy), ICTS (Isothermal Capacita)
nce Transient Spectroscopy), TSIC (Thermally
Stimulated Ionic Current), IV (Current-Voltage)
characteristic: Current-voltage characteristic measuring method), CV (Capac
There is a measuring method such as itance-Voltage characteristic. The present invention relates to a sample heating device for a thermoelectric measurement device that performs these measurement techniques.

[0002]

2. Description of the Related Art The TSC method is a kind of traditional thermal measurement method, and measures a current generated in a sample by changing a sample temperature. Various analyzes can be performed from the measurement results. It is known to analyze a crystal defect of a sample using the TSC method. For example, Japanese Journal o
f Applied Physics, Vol.27, No.2, 1988, pp.260-268
Analyzes deep level traps by measuring TSC spectra of semi-insulating GaAs (gallium arsenide) in a low temperature range from liquid helium temperature to room temperature. To measure such a crystal defect, the following is performed. When the sample is cooled to a low temperature of, for example, about minus 180 ° C., and the sample is irradiated with excitation light having a specific wavelength, and then the temperature of the sample is increased, carriers are released from the crystal defects. A weak current (for example, about 10 −13 amps to about −15 amps) is generated. By measuring the weak current, crystal defects in the sample can be analyzed.

In the TSC measuring device, a sample cooling device and a sample heating device are required to change a sample temperature. Various methods are known as means for heating the sample, but the most common method is to arrange the sample inside a heating furnace. When the heater of the heating furnace is heated, the sample temperature rises due to radiant heat from the heater and heat conduction transmitted through the gas and the sample support.

[0004]

When a sample is heated by using radiant heat from a heat source such as a heater, there are the following problems. Considering the measurement of the thermal stimulation current of a semiconductor sample in a TSC measuring device, when a sample receives radiant heat from a heater, if a band gap sensitive to the radiant energy exists in the sample, it is caused by the radiant energy. A trap is generated, and a weak current due to recombination is generated in the sample, which becomes an extra current for the measurement result.
Therefore, it is important that radiant heat from a heat source such as a heater does not directly hit the sample. Therefore, for example, it is conceivable to arrange a heater on the back surface of the sample support and heat the sample only by heat conduction from the heater. However, when the heater is brought close to the sample, the current flowing through the heater affects the measurement of the weak current in the sample, and may cause noise on the measurement result.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a thermoelectric measurement apparatus in which radiant heat from a heat source does not hit a sample and current flowing through a heater is not heat. An object of the present invention is to provide a sample heating device that does not affect electric measurement.

[0006]

The sample heating device of the thermoelectric measuring device according to the present invention has the following arrangement. (A) A conductive heater container that can be fixed to a sample assembly of a thermoelectric measurement device. (B) A heater element disposed inside the heater container. (C) an electrical insulator for electrically insulating the heater element from the heater container. (D) a conductive bellows having one end electrically connected to the heater container; (E) a conductive tube electrically connected to the other end of the bellows, the tube surrounding a space accommodating the sample assembly;

[0007] The heater container, the bellows and the tube are electrically connected to each other, and these constitute an electrostatic shield surrounding a space for accommodating the sample assembly. It should be noted that this electrostatic shield can be an excellent electromagnetic shield (attenuate lines of magnetic force and electromagnetic waves) by appropriately selecting the material and thickness of the components that make up the electrostatic shield. Hereinafter, in this specification,
The term “electrostatic shield” will be used as a function of the electromagnetic shield (regardless of its capability). The heater element disposed inside the heater container is located outside the electrostatic shield when viewed from the space. Therefore, the electromagnetic wave generated due to the current flowing through the heater element is not shielded by the electrostatic shield and does not reach the sample, and does not affect the measurement of the weak current flowing through the sample. In addition, the heater container is fixed to the sample assembly, and the sample is heated by heat conduction, so that the radiant heat from the heat source does not directly hit the sample surface, generating a weak current due to the radiant energy from the heat source. do not do.

[0008] The sample assembly according to the present invention refers to a combination of a sample and a support for supporting the sample. For example, in a thermoelectric measurement device, a sample is generally fixed to a substrate by means such as adhesion, and in this case, a sample assembly includes the sample and the substrate. When fixing the heater container to this sample assembly, the heater container is fixed to the back surface of the substrate (the side on which the sample is not fixed).

The sample heating apparatus of the present invention is typically
TSC (Thermally Stimulated Current)
It can be applied to measuring devices,
(Dielectric Analysis: thermal relaxation measurement), DLTS (Deep
Level Transient Spectroscopy), ICTS (Isother
mal Capacitance Transient Spectroscopy), TSIC
(Thermally Stimulated Ionic Current), IV (Curr
The present invention can also be applied to a thermoelectric measurement device that performs a measurement method such as ent-Voltage characteristic (method for measuring current-voltage characteristics) and CV (capacitance-voltage characteristic: measuring method for capacitance-voltage characteristics). The object to be measured is one that needs to be irradiated with a laser beam of a specific wavelength, for example, a semiconductor (compound semiconductor such as GaAs or Si) or another electronic material (organic, indefinite, or a mixture thereof). )
It is suitable for the measurement of a weak current reflecting the impurity level of.

[0010]

FIG. 1 is a front sectional view showing a main part and a sample assembly of one embodiment of a sample heating apparatus according to the present invention. The sample heating device and sample assembly shown here are for a TSC measurement device. First, the structure of the sample assembly 10 will be described. This sample assembly 10 is obtained by bonding a GaAs sample 14 to a substrate 12 made of aluminum nitride. Aluminum nitride is an electrical insulating material having good thermal conductivity. In the TSC measuring device, since it is important to control the temperature of the sample 14 accurately and uniformly, the substrate 1
4 must have good thermal conductivity. The thermal conductivity of aluminum nitride is 170 [W / (m · K)] at 20 ° C., which is extremely good. In addition, as a material of the substrate 12, boron nitride, beryllium oxide, and aluminum oxide can be used, and their thermal conductivity (unit is [W /
(m · K)]) is that boron nitride is 75 at 20 ° C. (however,
Beryllium oxide is 24 ° C at 20 ° C.
0, aluminum oxide is 38 at 20 ° C.

In the center of the elongated substrate 12 in the longitudinal direction, T
An intermediate layer 16 having a three-layer structure of i / Mo / Au (Ti is on the substrate side) is formed. The GaAs sample 14 is bonded thereon via an adhesive layer 18 made of In (indium). Since indium constituting the adhesive has a very good thermal conductivity, the sample has good heat uniformity. A pair of relay electrode layers 24 and 26 are formed at both ends in the longitudinal direction of the substrate 12 at a distance from the center intermediate layer 16. These relay electrode layers 24 and 26 are also located at the center intermediate layer 1.
As in the case of No. 6, it has a three-layer structure of Ti / Mo / Au.

A film having a two-layer structure is formed on the lower surface of the sample 14 in the order of Ti (titanium) and Au (gold) from the side of the sample 14. On the upper surface of the sample 14, a pair of electrode layers 2
0 and 22 are formed at intervals. These electrode layers 20 and 22 have a three-layer structure of AuGe / Ni / Au. That is, in order from the sample 14 side, Au 88%
・ Ge12% AuGe (gold germanium) alloy, Ni
Films are formed in the order of (nickel) and Au (gold). The electrode layer 20 on the sample 14 is electrically connected to the left relay electrode layer 24 by two Au wires 28. Similarly, the right electrode layer 22 on the sample 14 is electrically connected to the right relay electrode layer 26 by another two Au wires 30.

Next, a structure when the sample assembly 10 is mounted on a TSC measuring device will be described. Sample assembly 10
By two stainless steel support rods 32, 34
It is supported in the SC measuring device. These support rods 3
Reference numerals 2 and 34 also function as conductors for forming an electric circuit. These support rods 32, 34 are connected to the substrate 12 of the sample assembly 10 by screws 40, 42. Au washers 36 and 38 are inserted between the lower end surfaces of the support rods 32 and 34 and the upper surfaces of the relay electrode layers 24 and 26, respectively. 1
An ammeter and a voltage source will be selectively connected between the pair of support rods 32,34.

FIG. 2 is a plan view of the sample assembly 10. An intermediate layer 16 and a relay electrode layer 24 formed on the substrate 12;
26 is indicated by hatching. The electrode layers 20 and 22 formed on the sample 14 are also shown by hatching. Since the sample assembly 10 has the pair of electrode layers 20 and 22 formed on the upper surface of the sample 14, the heat stimulation current along the surface of the sample 14 is measured.

Next, the sample heating device will be described. Returning to FIG. 1, the sample heating device is a conductive (metal) heater container 5.
0 is provided. The heater container 50 includes a cylindrical portion 51 and a flange 52. The cylindrical portion 51 has a cup shape (bottomed cylindrical shape) opened downward. A flange 52 is formed integrally with the lower end of the cylindrical portion 51. The upper end of a conductive (metal) bellows 70 is fixed to the flange 52.
Inside the cylindrical portion 51 of the heater container 50, flat panel heater elements 54 and 56 are accommodated. In this embodiment, the flat panel heater elements 54 and 56
They are arranged in columns. A sheet-shaped electric insulator 58 is disposed between the upper heater element 54 and the heater container 50 to electrically insulate the heater element 54 from the heater container 50. An electric insulator 60 on the sheet is also arranged between the upper and lower heater elements 54 and 56. The heater elements 54 and 56 are resistance heating type heater elements and are formed in a sheet shape. These heater elements 54 and 56
Has a spiral pattern as shown in FIG. Returning to FIG. 1, power is supplied to the heater elements 54 and 56 from the wiring 62. Upper plate 64 of heater container 50
The tip of a thermocouple 66 is adhered to the inner surface (lower surface) of the thermocouple 66. The upper surface of the upper plate 64 of the heater container 50 is fixed to the lower surface of the substrate 12 of the sample assembly 10 via a heat transfer sheet 68 made of a soft material having good heat conduction. As the heat transfer sheet 68, a sheet made of silver, gold, or graphite can be used. The heat transfer sheet 68 plays a role of improving the adhesion between the substrate 12 and the heater container 50 and efficiently transmitting the heat of the heater element to the sample.

In FIG. 2, the cylindrical portion 51 of the heater container is shown by a broken line. The substrate 12 of the sample assembly 10 has a pair of through holes 72, 7 used for mounting a heater container.
4 are formed. Screw holes are formed in the upper plate 64 (FIG. 1) of the heater container at positions corresponding to these through holes 72 and 74. FIG. 3 is a sectional view taken along line 3-3 of FIG. 2 and shows a state where the heater container 50 is attached to the sample assembly 10. The upper surface of the upper plate of the heater container 50 is fixed to the lower surface of the substrate 12 of the sample assembly 10 via the heat transfer sheet 68. The two screws 76, 78 are inserted into the through holes 72, 74.
2 is screwed into the screw hole of the upper plate of the heater container 50, whereby the heater container 50 can be fixed to the back side of the substrate 12. The heat transfer sheet 68 is also provided with through holes for the screws 76 and 78 to pass through.

As shown in FIG. 3, since the heater container 50 is located on the back side of the substrate 12 when viewed from the sample 14, radiant heat from the heater container 50 does not directly hit the surface of the sample 14.

FIG. 4 is a front sectional view showing the structure around the sample assembly. The lower end of the bellows 70 of the sample heating device is fixed to the flange 80. The flange 80 is formed integrally with the inner peripheral portion of the lower plate 82 having a substantially hollow disk shape.
The outer peripheral edge of the lower plate 82 is fixed to the lower end of the cylinder 84. The tube 84 surrounds a space 86 that accommodates the sample assembly 10. The lower plate 82 and the cylinder 84 are both formed of a conductive material (metal), and are mechanically fixed to each other, and of course, electrically connected to each other. The upper end of the cylinder 84 is mechanically and electrically connected to the frame of the TSC measuring device, and is at the ground potential. Therefore, the space 86 accommodating the sample assembly 10 is surrounded by the conductor (electrostatic shield) at the ground potential. The conductive heater container 50 also forms a part of the electrostatic shield. The heater element inside the heater container 50 is located outside the electrostatic shield when viewed from the space 86 containing the sample assembly 10.

Since the heater element is located outside the electrostatic shield, the following effects can be obtained. When power is supplied to the heater element to heat the sample assembly, the current flowing through the heater element has no electrical effect on the sample assembly. Since the heater element is outside the electrostatic shield,
Electromagnetic noise radiated from the heater element and its wiring is cut off by the electrostatic shield and does not affect the internal space of the electrostatic shield.

The heater container 50, the bellows 70 and the lower plate 82
And the cylinder 84 may be made of a conductive material (typically a metal) from the viewpoint of the electrostatic shielding material, but if the function of the electromagnetic shield is emphasized, stainless steel (ferromagnetic material), iron, nickel It is preferable to use such as. Also, the heater container 50
Is preferably a material having good heat conductivity in addition to being electrically conductive. For example, copper-plated copper can be used.

The bellows 70 includes the heater container 50 and the lower plate 8.
It has a function of absorbing a change in the distance from the second. Sample assembly 1
Since the height position of 0 and the height position of the lower plate 82 are at predetermined positions, the distance between them is basically constant. However, when the temperature of the sample is changed over a wide temperature range, the distance may change due to expansion and contraction of each part. Therefore, the height position of the heater container 50 may change with respect to the lower plate 82. Also, in the operation of attaching the heater container 50 to the sample assembly 10, the heater container 5
It is conceivable to move 0 up and down. In consideration of such a point, a function that can change the distance between the heater container 50 and the lower plate 82 in an electrically connected state is required. Therefore, a conductive bellows 70 is provided between the heater container 50 and the lower plate 82 so that a change in distance can be absorbed. Further, the bellows 70 also has the meaning of increasing the heat conduction distance from the heater container 50 to the lower plate 82. When the heater container 50 is electrically connected to the lower plate 82, heat is conducted through the connection portion, which leads to loss of heating energy. Since the bellows 70 can increase the distance of heat conduction, loss of heating energy can be reduced.

[0022]

According to the sample heating apparatus of the present invention, since the heater container is fixed to the sample assembly, radiant heat from the heater container does not directly hit the sample. Further, since the space accommodating the sample assembly is surrounded by the electrostatic shield having the heater container as a part, the current flowing through the heater element does not affect the thermoelectric measurement.

[Brief description of the drawings]

FIG. 1 is a front sectional view showing a main part and a sample assembly of one embodiment of a sample heating apparatus according to the present invention.

FIG. 2 is a plan view of a sample assembly.

FIG. 3 is a sectional view taken along line 3-3 in FIG. 2;

FIG. 4 is a front sectional view showing a structure around a sample assembly.

FIG. 5 is a plan view showing a pattern of a heater element.

[Explanation of symbols]

 Reference Signs List 10 Sample assembly 12 Substrate 14 Sample 50 Heater container 54, 56 Flat panel heater element 58, 60 Electrical insulator 68 Heat transfer sheet 70 Bellows 84 Tube 86 Space

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Masanobu Inami 3-9-1, Matsubara-cho, Akishima-shi, Tokyo Rigaku Electric Co., Ltd. F-term (reference) 2G040 AB08 AB18 AB20 BA18 BA25 BA27 CA02 CA13 CA22 DA02 EA02 EA06 EB06 EB02 EC03 EC08 FA01

Claims (4)

[Claims] 1. A sample heating device for a thermoelectric measurement device having the following configuration. (A) A conductive heater container that can be fixed to a sample assembly of a thermoelectric measurement device. (B) A heater element disposed inside the heater container. (C) an electrical insulator for electrically insulating the heater element from the heater container. (D) a conductive bellows having one end electrically connected to the heater container; (E) a conductive tube electrically connected to the other end of the bellows, the tube surrounding a space accommodating the sample assembly; 2. The sample heating apparatus according to claim 1, wherein the heater container is fixed to the sample assembly via a heat transfer sheet made of a soft material having good heat conduction. apparatus. 3. The sample heating apparatus according to claim 1, wherein said heater element is a flat panel heater element of a resistance heating type. 4. The sample heating device according to claim 1, wherein the thermoelectric measurement device is capable of irradiating the sample with light to measure the thermoelectric characteristics of the sample. Sample heating device.