JPH06196403A - Substrate structure, controlling method therefor and controlling method for substrate temperature - Google Patents

Abstract

PURPOSE:To control fluctuation in the substrate temperature during the crystalline growing step on the substrate in vacuum state. CONSTITUTION:A substrate 1 is bonded onto a semiconductor crystal 2 using a low melting point metal 3 while the semiconductor crystal 2 is further bonded onto a substrate holder 4 using another low melting point metal 5. The substrate holder 4 is heated with a heater 6 while the temperature on the rear side of the holder 4 is measured using a thermocouple 7. The semiconductor crystal 2 in the size almost covering the whole surface of the substrate holder is doped with the impurities while the emissivity of the substrate 1 and the whole semiconductor crystal is to be controlled. At this time, a specific substrate temperature is maintained during the crystalline growing step by specifying the display temperature of the thermocouple 7 by equalizing the emissivity with that of the growing crystal. Through these procedures, the fluctuation in the substrate temperature during the crystalline growing step can be controlled. Furthermore, the crystalline growing step can be assured of the extremely high quality if only the display temperature of the thermocouple 7 or the heater power is specified thereby entirely eliminating the whole complicated temperature control during the crystalline growing step.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a substrate structure, a substrate structure manufacturing method, and a substrate temperature control method.

[0002]

2. Description of the Related Art Pretreatment methods for GaAs substrates in molecular beam epitaxy (MBE) growth are degreasing, etching,
The protective oxide film is formed by a wet process, washed with water, dried, and then attached to the substrate holder. As a method of attaching the substrate to the substrate holder, there are a case of sticking with In and a case of fixing the substrate as it is to a heat radiation heating type substrate holder (J. Vacuum Sc
i. Technol. B5 (1987) p. 734)).
This fixing is usually done in air. After that, the holder with the substrate attached is introduced into the growth chamber.

The pretreatment method for a CdTe or CdZnTe substrate is as follows. First, the substrate is degreased and dried, and the substrate is attached to the substrate holder by Ga in air. Next, it is immersed in bromine methanol together with the substrate holder, and the surface oxide film on the substrate is removed by etching (Journal of Crystal Growth (J.Cr.
ystal Growth 54 (1981) 577
page)). After washing in methanol, it is dried in nitrogen without exposure to air and introduced into a growth chamber.

Further, when the substrate bonded to the substrate holder by the low melting point metal is heated during crystal growth in vacuum, it is heated by a heat supply source such as a heater arranged on the back side of the substrate. At this time, when heating by heat conduction through a substrate holder or the like, a low melting point metal such as In or Ga is used to improve heat transfer between the substrate and the substrate holder (Journal of Crystal Growth). (J.C.
physical Growth 54 (1981) 57
(P. 7)). In the case of heating by heat radiation, sapphire or the like may be arranged between the substrate and the heater in order to increase the temperature uniformity (Journal of Vacuum Science and Technology (J. Va.
cum Sci. Technol. B5 (1987)
734)).

In the above heating method, the temperature of the substrate is controlled by using any one of a thermocouple, a heater power, a radiation thermometer or a combination thereof. The thermocouple is arranged in contact or non-contact with the back side of the substrate or the substrate holder. The radiation thermometer measures the temperature by the amount of infrared radiation from the surface of the substrate.

[0006]

The conventional pretreatment method has a problem of surface oxidation and surface contamination due to impurities, since the work of attaching the substrate in air is involved. Ideally, such work is performed in a clean environment such as a high-purity nitrogen atmosphere in which oxygen, moisture, and other impurities are extremely small. However, in an atmosphere of an inert gas such as nitrogen, the low melting point metal does not adapt to the substrate and the substrate holder, and there is a problem that the substrate does not stick well to the substrate holder.

Particularly, in the case of a CdTe or CdZnTe substrate, it is necessary to completely remove the oxide film at the pretreatment stage, and therefore, after the substrate is attached to the substrate holder, the substrate is put into an etching solution together with the holder. At this time, the etching liquid that has entered the details of the substrate holder cannot be completely removed by cleaning, and may be taken as an impurity in the growth film or contaminate the growth chamber.

Yet another major problem of the conventional pretreatment method is that when the size of the substrate changes, the rate of temperature change of the substrate during growth changes. During growth, the growth film adheres to both the substrate holder and the substrate, but the emissivity change at that time is different between the two. for that reason,
When the size of the substrate changes, the amount of change in the substrate temperature during the growth changes, making it impossible to perform reproducible growth. GaA
Unlike Si, it is difficult to obtain a large-area substrate for s, CdTe, CdZnTe, or the like, so that depending on the plane orientation, it may be indefinite or only a small-sized substrate may be obtained. In such a case, the above-mentioned problem of reproducibility of growth conditions becomes a problem that cannot be avoided by the conventional method. Further, handling of irregular-shaped or small-sized substrates is extremely troublesome, and it is necessary to prepare a dedicated jig for each substrate or the yield at the time of processing is deteriorated.

Particularly with respect to the substrate temperature of the conventional method, the temperature can be controlled to be constant in a steady state, but it is generally impossible to accurately control the substrate temperature during growth. The crystal to be grown adheres to the substrate and the substrate holder during the growth, so that the emissivity of the substrate and the substrate holder changes. Therefore, the amount of heat loss from the substrate and the substrate holder changes, and the substrate temperature changes accordingly. Usually, the emissivity change during growth often increases, and in that case, the substrate temperature during growth drops even if the measured temperature of the thermocouple or the heater power is kept constant. When the substrate temperature changes from the originally set value, the crystal characteristics are deteriorated, which is a big problem when the crystal is used as a device or the like.

An example in which the thermocouple is brought into contact with the substrate holder or the heater power is increased during growth in order to prevent the substrate temperature from changing as much as possible (Journal of Crystal Growth).
Growth 111 (1991) p. 698)), but the problem is that the substrate surface temperature changes even if the temperature of the back surface of the substrate holder is constant, and it is extremely difficult to optimize the amount of change in heater power during growth. There is. Further, even when using a radiation thermometer, there is a problem that an accurate temperature cannot be measured due to interference between the grown crystal and the substrate and a change in surface morphology during growth. Therefore, it is impossible to perform highly reproducible growth in which the substrate temperature is precisely controlled.

The object of the present invention has been made in view of the above conventional circumstances.
To provide a substrate structure capable of performing MBE growth with high reproducibility and a method for manufacturing the same, and a substrate temperature control method in crystal growth in vacuum capable of freely controlling the amount of change in substrate temperature during growth. is there.

[0012]

To achieve the above object, a substrate structure according to the present invention is a substrate structure having a semiconductor crystal and a substrate, wherein the semiconductor crystal is made of a low melting point metal on the upper surface of a substrate holder. The substrate is bonded to the surface of the semiconductor crystal by MBE growth, and is bonded to the surface of the semiconductor crystal by a low melting point metal.

The method of manufacturing a substrate structure according to the present invention is a method of manufacturing a substrate structure in which an etching process, a bonding process, a pressure bonding process and a heating process are performed to laminate and bond a substrate and a semiconductor crystal on a substrate holder. The etching process is to etch the substrate, the bonding process is to bond the semiconductor crystal to the upper surface of the substrate holder with a low melting point metal, and the bonding process is to lower the temperature in an inert gas atmosphere. The melting point metal is heated to a temperature equal to or higher than the melting point to be melted, the etched substrate is pressed down, and the substrate is bonded to the upper surface of the semiconductor crystal by the melted low melting point metal,
The heat treatment is to preheat the substrate and the semiconductor crystal, which are laminated and bonded to the upper surface of the substrate holder, in a high vacuum.

The method of manufacturing a substrate structure according to the present invention is a method of manufacturing a substrate structure in which a bonding process, an etching process, a pressure bonding process, and a heating process are performed to laminate and bond a substrate and a semiconductor crystal on a substrate holder. Then, the bonding process is to bond the substrate to the upper surface of the semiconductor crystal with a low melting point metal, the etching process is to etch the substrate together with the semiconductor crystal, and the pressure bonding process is under an inert gas atmosphere. The low melting point metal is heated to a temperature equal to or higher than the melting point to be melted, the laminated substrate and the semiconductor crystal are pressed down, and the back surface of the semiconductor crystal is bonded to the upper surface of the substrate holder by the melted low melting point metal, The heat treatment preheats the substrate and the semiconductor crystal, which are laminated and bonded to the upper surface of the substrate holder, in vacuum.

Further, the substrate temperature control method according to the present invention is
A substrate temperature control method for controlling the temperature of a substrate laminated and bonded with a low melting point metal on a semiconductor crystal, wherein the semiconductor crystal covers the entire surface of the substrate holder and is bonded to the substrate holder with the low melting point metal. The temperature of the substrate during growth is controlled by the doping amount of the impurities with which the semiconductor crystal is doped.

The substrate structure control method according to the present invention is a substrate temperature control method for controlling the temperature of a substrate laminated and bonded on a semiconductor crystal by a low melting point metal, and the semiconductor crystal is controlled by a substrate holder. It is joined by a melting point metal and is doped with a certain amount of impurities when controlling the substrate temperature. It changes the area of the semiconductor crystal and changes the total thermal emissivity of the substrate, the semiconductor crystal and the substrate holder. This controls the substrate temperature during growth.

[0017]

In the method of manufacturing a substrate structure according to the present invention, the cleaned substrate after etching is processed in a high-purity inert gas atmosphere and introduced into the growth chamber without exposing the substrate to the atmosphere. Adhesion of impurities to the surface and surface oxidation are extremely small.

By the way, in an originally inert gas atmosphere,
The reason why the low melting point metal, which is not compatible with the substrate and the substrate holder, is well adapted by the method of the present invention is due to the pressure bonding and the preheating in vacuum. When a substrate or a Si wafer is attached to a low-melting-point metal-coated surface in an inert gas atmosphere, the low-melting-point metal becomes droplets at that moment if it is laterally displaced to fit the adhesive surface. It separates from the coated surface.

Therefore, if the substrate is heated only in a crimped state without being made familiar with it and heated in a vacuum, the gap between the substrate or the Si wafer and the coating surface is evacuated and filled with the liquefied low melting point metal so that the substrate and the like are made compatible with it. become. If the temperature at the time of pressure bonding is not higher than the melting point of the low-melting-point metal, the gap due to the unevenness of the coating surface is too large, and it becomes difficult to adapt even if it is heated in vacuum. The reproducibility of the substrate temperature greatly depends on whether the low melting point metal is well suited.

Since the method of the present invention is a manufacturing method in an oxygen-free state, it is not necessary to form a protective oxide film in the pretreatment of the GaAs substrate. If there is no protective oxide film, the step of removing the oxide film before growth can be omitted, so that low-temperature treatment can be performed with the upper limit near the growth temperature. G with built-in device
When growing on an aAs substrate, the method of the invention allows MBE growth without destroying the device.

In the pretreatment of CdTe and CdZnTe of the present invention, the reason why Ga is used to stick to a Si wafer is that it is not dissolved in bromine methanol used as an etching solution. If another low melting point metal such as In is used, it dissolves in bromine methanol and contaminates the substrate surface, so that the object of the present invention cannot be achieved.

Further, when the substrate is heated during crystal growth in vacuum, the semiconductor crystal covers almost the entire surface of the substrate holder, so that heat loss from the substrate holder can be avoided.
The change in the amount of heat loss from the semiconductor crystal and the substrate during growth can be controlled by changing the doping amount of the semiconductor crystal. The emissivity of a semiconductor crystal increases as the doping amount increases. Therefore, if the doping amount is controlled so that the emissivity of the semiconductor crystal becomes the same as the emissivity of the grown crystal, the heat loss from the semiconductor crystal does not change during the growth. In fact, considering the effect of the emissivity of the substrate,
If the doping amount is controlled so that the overall emissivity does not change before and after the growth, the substrate temperature can be kept constant during the growth. Here, if the doping amount is smaller than the above-mentioned doping amount, the substrate temperature can be lowered during the growth, and if it is larger, the substrate temperature can be raised.

Further, the emissivity of the entire semiconductor crystal and the substrate holder can be controlled by the area of the semiconductor crystal to control the substrate temperature during growth. The substrate holder is usually made of a metal such as molybdenum, and when the grown crystal adheres to the substrate in a polycrystalline state, the emissivity increases remarkably, so that the heat loss increases and the substrate temperature decreases. for that reason,
By changing the exposed area of the substrate holder, the amount of change in emissivity before and after growth can be freely changed. If the emissivity of the semiconductor crystal is made larger than that of the growing crystal, the substrate temperature during growth rises when the exposed area of the substrate holder is 0 (the semiconductor crystal and the substrate holder have the same size), and the area of the semiconductor crystal increases. If is smaller, the substrate temperature becomes constant at a certain size, and if it is smaller, the substrate temperature during growth can be lowered.

[0024]

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a configuration diagram showing a basic configuration of a substrate structure according to the present invention.

In FIG. 1, the substrate structure according to the present invention is
The semiconductor crystal 2 and the substrate 1 are laminated and joined.

The semiconductor crystal 2 is bonded to the upper surface of the substrate holder 4 with the low melting point metal 5.

The substrate 1 is to be MBE-grown on the surface, and is bonded to the surface of the semiconductor crystal 2 with the low melting point metal 3.

The substrate holder 4 is heated by the heater 6 and the back surface temperature is measured by the thermocouple 7. Also,
In FIG. 1, a substrate 1 having a size of 15 × 15 mm is used, and a substrate holder 4 made of molybdenum having a diameter of 88 mm is used.

(Embodiment 1) Next, an embodiment of a method for manufacturing a substrate structure according to the present invention shown in FIG. 1 will be described with reference to the drawings. FIG. 2 shows a method of manufacturing a substrate structure used when CdTe MBE growth is performed on a GaAs substrate.

First, a GaAs substrate is used as the substrate 1,
On the other hand, a Si wafer 2 is used as the semiconductor crystal 2. Then, the GaAs substrate 1 is etched with a sulfuric acid-based etching solution, and the Si wafer 2 is pinned 8 in a high-purity nitrogen atmosphere.
Crimp using. The Si wafer 2 is bonded in advance to the substrate holder 4 with indium as the low melting point metal 5 in the air, and indium as the low melting point metal 3 is applied to the bonding surface with the GaAs substrate 1. After that, the sample was introduced into the sample preparation chamber of the growth apparatus without being exposed to the atmosphere, preheated at 200 ° C. for 10 minutes in a high vacuum of 10 ⁻⁹ torr, and the space between the GaAs substrate 1 and the Si wafer 2 was familiarized with indium. Then, the GaAs substrate 1 is laminated and bonded on the Si wafer 2.

The substrate 1 is introduced into the growth chamber while maintaining a vacuum, heated to 250 ° C., and CdTe is grown on its surface.

(Embodiment 2) Next, C on the substrate 1 shown in FIG.
A substrate temperature control method for growing dTe will be described with reference to FIGS.

In this embodiment, by changing the area of the semiconductor crystal 2, the total thermal emissivity of the substrate 1, the semiconductor crystal 2 and the substrate holder 4 is changed, thereby controlling the substrate temperature during growth. .

In this embodiment, the GaAs substrate is not subjected to the high temperature treatment for removing the oxide film, but single crystal C is used.
dTe was obtained and low temperature treatment became possible. Moreover, the substrate temperature did not change depending on the size of the substrate 1. Si wafer 2 contains approximately 10 ¹⁹ c with P as an impurity.
m ^-3 Dope pink, and the resistivity of Si wafer 2 is about 0.0
Adjust to 5Ω · cm. Diameter of Si wafer 2 is 76m
When m, the substrate temperature during growth is constant,
When the area of the wafer 2 was reduced, the substrate temperature during growth was lowered when the display temperature of the thermocouple 7 was kept constant. In the method of the present invention, the substrate temperature during growth can be controlled while the Si doping amount is kept constant. Therefore, by preparing a large number of Si wafers of the same type and different sizes, it is possible to rapidly prepare for various growth conditions. It also has the advantage of being able to respond.

(Embodiment 3) Another embodiment of the method of manufacturing the substrate structure according to the present invention shown in FIG. 1 will be described with reference to FIG.

The present embodiment is an example in which MBE growth of HgCdTe is performed on a CdZnTe substrate. First, C
The dZnTe substrate 7 is bonded to the Si wafer 2 by using gallium as the low melting point metal 3 in the atmosphere. This is etched with bromine methanol to remove the surface oxide film of the substrate, and then pressure-bonded to the substrate holder 4 to which gallium as the low melting point metal 5 has been applied in advance in a high-purity nitrogen atmosphere using pins 8. After that, the sample was introduced into the sample preparation chamber of the growth apparatus without being exposed to the atmosphere, preheated at 200 ° C. for 10 minutes in a high vacuum of 10 ⁻⁹ torr, and the space between the Si wafer 2 and the substrate holder 4 was familiarized with gallium. No Si
The back surface of the wafer 2 is bonded to the top surface of the substrate holder 4.

The substrate 1 was introduced into the growth chamber while maintaining a vacuum, heated to 180 ° C., and HgCdTe was formed on the surface thereof.
Growth takes place.

(Embodiment 4) Next, H on the substrate 1 shown in FIG.
A substrate temperature control method for growing gCdTe will be described with reference to FIGS.

In this embodiment, MBE growth of HgCdTe is performed. The Si wafer of the semiconductor crystal 2 has a size that substantially covers the entire surface of the substrate holder 4, and is doped with As as an impurity. Here, the emissivity of the substrate 1 and the semiconductor crystal 2 as a whole is made equal to the emissivity of the grown crystal, so that the display temperature of the thermocouple 7 is kept constant and the substrate temperature is kept constant. As a result of the experiment, when the Si wafer 2 doped with As as high as 10 ¹⁹ cm ⁻³ was used, the substrate temperature during growth became constant only by making the display temperature of the thermocouple 7 constant. The resistivity of the Si wafer 2 at this time is 0.02 Ω · cm or less. In the conventional method, bromine was mixed in the grown film at about 10 ¹⁵ to 10 ¹⁶ cm ⁻⁵ , but in the method of the present invention, bromine was not mixed. Further, the surface defects of the grown film were extremely small, and the dislocation density of the HgCdTe crystal at this time was 10 ⁵ cm ^-2 or less, and the crystal of the highest level as obtained by MBE was obtained. When the doping amount was reduced from this, the substrate temperature during growth was lowered when the display temperature of the thermocouple was kept constant. Resistivity of about 20 Ω when B is doped as an impurity
In the case of using the Si wafer 2 of cm, due to the substrate temperature drop during the growth, twin crystals were formed 90 minutes after the growth, and the single crystal could not be grown. Further, when the Si wafer was not used, the single crystal could grow up to about 2 minutes at the initial growth stage due to the rapid temperature drop. In addition, in the method of the present invention, since the entire surface of the substrate holder is covered with the Si wafer 2, it is not necessary to etch the substrate holder 4 again, so that the work can be simplified and degassing from the substrate holder 4 can be prevented. It also has the advantage of reduction.

[0040]

As described above, according to the present invention,
A clean substrate surface with very few impurities is obtained in the pretreatment of MBE growth. Further, regardless of the size of the substrate, the growth of the substrate temperature can be performed with high reproducibility, and a good quality crystal can be obtained. Further, since all the substrates are attached to the Si wafer having a uniform diameter, the subsequent handling of the substrates becomes extremely simple.

Furthermore, it is possible to control changes in the substrate temperature during growth. Further, extremely high-quality crystal growth can be performed by simply making the display temperature of the thermocouple or the heater power constant without performing any complicated temperature control during the growth.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a basic configuration of a substrate structure according to the present invention and a method of controlling a temperature of a substrate using the substrate structure.

FIG. 2 is a configuration diagram showing an embodiment of a method for manufacturing a substrate structure according to the present invention.

FIG. 3 is a configuration diagram showing another embodiment of the method for manufacturing a substrate structure according to the present invention.

[Explanation of symbols]

 1 substrate 2 semiconductor crystal 3,5 low melting point metal 4 substrate holder 6 heater 7 thermocouple 8 pin

Claims (5)

[Claims] 1. A substrate structure having a semiconductor crystal and a substrate, wherein the semiconductor crystal is bonded to the upper surface of a substrate holder by a low melting point metal, and the substrate is molecular beam epitaxy grown on the surface. A substrate structure characterized by being bonded to the surface of the semiconductor crystal with a low melting point metal. 2. A method for manufacturing a substrate structure, wherein an etching process, a bonding process, a pressure bonding process and a heating process are performed to laminate and bond a substrate and a semiconductor crystal on a substrate holder, wherein the etching process etches the substrate. The bonding process is to bond the semiconductor crystal to the upper surface of the substrate holder with a low melting point metal, and the bonding process is to heat the low melting point metal to a temperature above the melting point under an inert gas atmosphere. The substrate is melted and the etched substrate is pressed down, and the substrate is bonded to the upper surface of the semiconductor crystal by the melted low melting point metal. The heat treatment is performed on the substrate and the semiconductor crystal laminated and bonded to the upper surface of the substrate holder. A method of manufacturing a substrate structure, comprising preheating under a high vacuum. 3. A method of manufacturing a substrate structure, wherein a substrate, a semiconductor crystal are laminated and bonded on a substrate holder by performing a bonding process, an etching process, a pressure bonding process and a heating process, wherein the bonding process is an upper surface of the semiconductor crystal. The substrate is bonded with a low-melting point metal, the etching process is for etching the substrate together with the semiconductor crystal, and the pressure bonding process is for heating the low-melting point metal to a temperature equal to or higher than the melting point in an inert gas atmosphere. It is melted and pressed down to laminate the substrate and semiconductor crystal, and the back surface of the semiconductor crystal is bonded to the upper surface of the substrate holder by the melted low melting point metal. The heat treatment is laminated bonding to the upper surface of the substrate holder. A method of manufacturing a substrate structure, comprising preheating the formed substrate and semiconductor crystal under vacuum. 4. A substrate temperature control method for controlling the temperature of a substrate laminated and bonded to a semiconductor crystal by a low melting point metal, wherein the semiconductor crystal covers the entire surface of the substrate holder and is bonded to the substrate holder by the low melting point metal. A substrate temperature control method, wherein the substrate temperature during growth is controlled by the doping amount of an impurity with which the semiconductor crystal is doped. 5. A substrate temperature control method for controlling the temperature of a substrate laminated and bonded to a semiconductor crystal by a low melting point metal, wherein the semiconductor crystal is bonded to a substrate holder by the low melting point metal to control the substrate temperature. At that time, a certain amount of impurities are doped, and by changing the area of the semiconductor crystal and changing the thermal emissivity of the entire substrate, the semiconductor crystal, and the substrate holder,
A substrate temperature control method comprising controlling the substrate temperature during growth.