JP2011244009A - Method of manufacturing ain semiconductor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing an AIN semiconductor capable of easily manufacturing AIN semiconductor, and obtaining an AIN semiconductor for an electronic device which is excellent in crystallinity by controlling growth speed of AIN across a wider range and excluding possibility of entrainment of impurities as much as possible.SOLUTION: In a method of manufacturing an AIN semiconductor for an electronic device, NHgas and aluminum chloride gas, which is a result from sublimation or evaporation with absolute aluminum chloride, of which the total of impurity components other than group III elements is 0.001 wt.% or less, that has been heated are caused to react each other by a hydride vapor-phase deposition, to allow crystal growth of AIN on a substrate.

Description

  The present invention relates to an AlN semiconductor manufacturing method for crystal growth of AlN on a substrate using a hydride vapor phase growth method, and an AlN semiconductor manufacturing apparatus for manufacturing an AlN semiconductor.

  Aluminum nitride (AlN) has the widest bandgap (up to 6.2 eV) among semiconductors that can be put to practical use, so it is expected to be used as a semiconductor light-emitting element and various semiconductor devices in the short ultraviolet region with a short wavelength. ing. Up to now, excimer lasers and YAG lasers have been used as lasers in the deep ultraviolet region, but if a deep ultraviolet laser diode using AlN is realized, higher efficiency can be achieved compared to these lasers. It can be expected to be used in a wide range of applications such as lithography, small-sized, low-cost general-purpose precision processing, and medical applications, high-density white light storage, and high-power white using the high thermal conductivity of AlN. Various applications are also possible in the field of electronic devices such as LEDs and substrate materials for manufacturing high-power / high-frequency electronic devices.

As a technology for crystal growth of an AlN semiconductor, an aluminum nitride raw material is placed in a growth vessel, and this growth vessel is heated by high-frequency induction heating or the like to keep the raw material portion at a high temperature of about 1900 to 2250 ° C. A sublimation method in which an AlN single crystal is grown by recombination and recrystallization at a lower temperature than the raw material portion, a solution growth method (flux method) in which an AlN crystal is precipitated while cooling a saturated solution in which the Al raw material is dissolved, and Using a hot wall type quartz reaction tube, high purity Al (solid) and HCl (gas) are reacted in the raw material part of the quartz reaction tube to produce Al halide (gas). There is a hydride vapor phase epitaxy (HVPE) method in which Al halide is transported to the reaction part of a quartz reaction tube and reacted with NH ₃ gas to vapor phase grow AlN. (See, for example, Patent Document 1, Non-Patent Document 1, and Non-Patent Document 2 for the HVPE method). However, it is difficult to obtain crystals with a large diameter by the sublimation method and the flux method, and it is not suitable for applying AlN semiconductors to industrial products and devices.

On the other hand, although the hydride vapor phase growth method can obtain a relatively large-diameter crystal and has a high growth rate and is suitable for obtaining thick AlN, AlCl gas generated when Al is reacted with HCl. Since the AlCl ₂ gas corrodes the quartz reaction tube (SiO ₂ ) vigorously, there is a possibility that Si may be mixed into the AlN crystal as an impurity. In some cases, the quartz reaction tube may be damaged. Hold it.

Under such circumstances, as described in Patent Document 1 and Non-Patent Document 1, the present inventors conducted AlN crystal growth by hydride vapor phase epitaxy in the raw material portion in the quartz reaction tube. Thermodynamic analysis of the reaction between HCl and HCl has led to the solution of previous problems. That is, as shown in FIG. 4, the reaction temperature is controlled to 700 ° C. or lower in the raw material part (raw material reaction part) to preferentially generate AlCl ₃ that does not corrode the quartz reaction tube [formula (1) ], Such an aluminum chloride gas was transported to the reaction part (growth reaction part) and reacted with NH ₃ gas, and AlN was vapor-phase grown [the following formula (2)].
Raw material part: Al (s) + 3HCl (g) = AlCl ₃ (g) + 3 / 2H ₂ (g) (1)
Reaction section: AlCl ₃ (g) + NH ₃ (g) = AlN (s) + 3HCl (g) (2)

Regarding the manufacturing method of the AlN semiconductor using this hydride vapor phase growth method, the further examination subject can be mentioned. To extensively control the growth rate of AlN is the partial pressure P ⁰ _AlCl3 of AlCl ₃ gas is necessary to control a wide range in the reaction section. In the hydride vapor phase growth method, AlCl ₃ gas generated by the reaction of the above formula (1) is used. For this, AlCl ₃ partial pressure P ⁰ _AlCl3 gas in the reaction section, as shown in the following equation (3), the supply amount FLOW partial pressure P ⁰ _HCl and HCl gas HCl gas supplied to the feed unit It is determined by _HCl and the total flow rate FLOW _Total in the reaction section.
P ⁰ _AlCl3 = 1/3 · P ⁰ _HCl · FLOW _HCl / FLOW _Total (3)

However, P ⁰ _HCl is uniquely determined by the HCl concentration in the HCl gas cylinder used. For this, the control of AlCl ₃ partial pressure P of the gas ⁰ _AlCl3 in the reaction unit must be carried out at a feed rate FLOW _HCl in HCl gas. A flow rate controller called a mass flow controller is usually used to control this flow rate, but the controllable range is determined by the control range of the mass flow controller to be used, and usually it cannot be controlled below several percent of full scale. . Therefore, the supply of the Al source for growing the crystal of AlN can be performed only within a limited range, which restricts the control of the AlN semiconductor. Furthermore, the reaction in formula (1) requires the use of a low temperature of 700 ° C. or lower for the selective production of AlCl ₃ . Therefore, if a high concentration of HCl is supplied, the reaction represented by the formula (1) becomes insufficient and unreacted HCl gas is supplied to the main reaction section of the formula (2). When this unreacted HCl gas is supplied to the reaction section, the growth rate is slowed as expected by equation (2).

  In addition, the above hydride vapor phase growth method requires that a raw material part (raw material reaction part) and a reaction part (growth reaction part) be provided in the reaction tube, so that the reaction apparatus itself becomes large-scale. There is room for. Furthermore, it is necessary to periodically replenish the metal Al provided in the raw material part. In this case, the reaction apparatus is opened, which causes the entire reaction apparatus to be contaminated with moisture, oxygen, or the like.

By the way, in the vapor phase growth of an AlN semiconductor using the hydride vapor phase growth method, it is conceivable to use AlCl ₃ directly as a raw material. However, in the purity of AlCl ₃ that has been available so far, impurities contained therein There were problems that the contamination in the quartz reaction tube was caused by the metal and the reaction did not proceed sufficiently, and that this impurity metal was mixed into the resulting AlN. For this reason, there has been no report that an AlN semiconductor is manufactured using AlCl ₃ directly as a raw material.

JP2003-303,774

Yoshinao Kumagai and Maki Haku, “High-speed growth of Al-based nitrides by hydride vapor phase growth”, IEICE Technical Report, ED2004-121, CPM2004-95, LQE2004-59 (2004-10) , P27-32. Yu-Huai LIU, Tomoaki TANABE, Hideo MIYAKE, Kazumasa HIRAMATSU, Tomohiko SHIBATA, Mutsuhiro TANAKA and Yoshihiko MASA, Japanese Journal of Applied Physics, vol.44, No.17, 2005, pp.L505-L507.

Accordingly, the present inventors can manufacture an AlN semiconductor having a large diameter of 2 inches or more and a method for manufacturing an AlN semiconductor using a hydride vapor phase growth method suitable for obtaining a thick AlN semiconductor. As a result of diligent studies to solve various problems of the conventional methods, NH ₃ gas and aluminum chloride gas obtained by heating and sublimating or vaporizing solid anhydrous aluminum chloride (AlCl ₃ ) It has been found that all the above-mentioned problems can be solved by direct reaction, and the present invention has been completed.

Accordingly, an object of the present invention is to manufacture an AlN semiconductor more easily than a conventional method in an AlN semiconductor manufacturing method using a hydride vapor phase growth method, which is relatively advantageous for practical application of AlN semiconductor manufacturing. In addition, it is possible to control the growth rate of AlN in a wider range, and to obtain an AlN semiconductor with excellent crystallinity by eliminating the possibility of contamination with impurities as much as possible. An object of the present invention is to provide a method for manufacturing an AlN semiconductor.
Another object of the present invention is to make it possible to easily manufacture an AlN semiconductor, to easily control the growth rate of AlN, and to eliminate contamination of impurities as much as possible. The object is to provide a semiconductor manufacturing apparatus.

That is, the present invention provides a hydride vapor phase growth method using an aluminum chloride gas and NH ₃ gas obtained by heating and sublimating or vaporizing anhydrous aluminum chloride in which the total of impurity components other than the group III element is 0.001% by weight or less. This is a method for producing an AlN semiconductor for electronic devices, characterized in that AlN is crystal-grown on a substrate.

  The present invention also relates to an AlN semiconductor manufacturing apparatus for growing AlN on a substrate by using a hydride vapor phase growth method, in which anhydrous aluminum chloride is heated to sublimate or vaporize to vaporize aluminum chloride gas. This is an AlN semiconductor manufacturing apparatus comprising a vessel and a reaction tube apparatus.

In the present invention, an aluminum chloride gas obtained by heating and sublimating or vaporizing anhydrous aluminum chloride (AlCl ₃ ) is used as the Al source, and NH ₃ gas is used as the N source, which is expressed by the following formula (4). AlN is crystal-grown on the substrate by a reaction by such a hydride vapor phase growth method.
AlCl ₃ (g) + NH ₃ (g) = AlN (s) + 3HCl (g) (4)

Among these, for the partial pressure P ⁰ _{AlCl 3} of aluminum chloride gas in the reaction section where AlN crystal grows on the substrate, the vapor pressure P ⁰⁰ _{AlCl 3} (T) of aluminum chloride maintained at the temperature T and the aluminum chloride transported The carrier gas supply amount FLOW _AlCl3 carrier to be used and the total flow rate FLOW _Total in the reaction section can be used to express the following equation (5).
_{^{P 0 AlCl3 = P 00 AlCl3 (}} T) · FLOW AlCl 3 carriers / FLOW _Total ··· ··· (5)

Here, the vapor pressure curve of aluminum chloride is shown in FIG. The solid line represents the vapor pressure curve of the dimer [(AlCl ₃ ) ₂ ], and the broken line represents the vapor pressure curve of the monomer [AlCl ₃ ]. Usually, since aluminum chloride is considered to be a dimer in a gas of 440 ° C. or lower, the term “aluminum chloride gas” in the present invention includes both states of a monomer and a dimer. . Then, in the present invention, it is possible to alter the vapor pressure P ⁰⁰ _AlCl3 (T) of aluminum chloride by adjusting the heating temperature of the anhydrous aluminum chloride, the partial pressure P ⁰ _AlCl3 Aluminum chloride gas, FLOW _AlCl 3 carrier In addition, it is possible to control in a wide range by controlling P ⁰⁰ _{AlCl 3} (T). That is, the growth rate of AlN can be controlled over a wide range by adjusting the heating temperature of anhydrous aluminum chloride.

Specifically, the heating temperature of anhydrous aluminum chloride is adjusted to 50 to 180 ° C, preferably 70 to 150 ° C, more preferably 85 to 135 ° C. When the heating temperature of anhydrous aluminum chloride is lower than 50 ° C., the partial pressure P ⁰ _{AlCl 3} of the aluminum chloride gas becomes too low to secure a sufficient AlN growth rate, and conversely, when the heating temperature is higher than 180 ° C., FIG. As is clear, the vapor pressure P ⁰⁰ _{AlCl 3} (T) of aluminum chloride reaches 1 atm, and the partial pressure P ⁰ _{AlCl 3} of the aluminum chloride gas cannot be controlled. By adjusting the heating temperature when heating anhydrous aluminum chloride in this way, the partial pressure P ⁰ _{AlCl 3} of the aluminum chloride gas depends on the carrier gas supply amount FLOW _AlCl 3 carrier of the aluminum chloride gas, but 1 It becomes possible to set a wide range in the range of × 10 ⁻⁶ to 1 × 10 ⁻¹ atm, and the crystal growth rate of AlN can be controlled in the range of 0.1 to 1000 μm / h.

The anhydrous aluminum chloride (AlCl ₃ ) used in the present invention is preferably anhydrous aluminum chloride in which impurity components other than the same group III elements as Al are reduced as much as possible, preferably other than the group III elements. The total of the impurity components is preferably 0.001% by weight or less. Examples of group III elements include gallium (Ga), boron (B), and indium (In). These elements are contained in anhydrous aluminum chloride, and are mixed during the crystal growth of AlN. However, since it is considered that a mixed crystal is formed with the AlN semiconductor, no positive exclusion is required. On the other hand, as impurity components other than Group III elements, for example, sodium (Na), magnesium (Mg), silicon (Si), potassium (K), titanium derived from an aluminum raw material used for industrial anhydrous aluminum chloride production Impurity metals such as (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), nickel (Ni), copper (Cu), zinc (Zn), calcium (Ca), water Examples thereof include impurities such as (H ₂ O) and oxygen (O). When impurity metals derived from aluminum materials as described above are mixed into AlN, it is considered that the crystallinity (crystal quality) of AlN is adversely affected. When the obtained AlN semiconductor is used in an electronic device, the band gap and transmission This may affect optical characteristics such as the rate and electrical characteristics such as conductivity, carrier density, and mobility. Similarly, water (H ₂ O) and oxygen (O) must be excluded. Therefore, it is preferable to use anhydrous aluminum chloride in which the total of impurity components other than Group III elements is 0.001% by weight or less. More preferably, the purity of anhydrous aluminum chloride is 99.999% by weight or more. Here, “purity of anhydrous aluminum chloride” refers to the purity of anhydrous aluminum chloride obtained by subtracting the total of impurity components including group III elements, other than the impurity concentration that can be detected by a commonly used analytical method. Means that everything is considered pure.

  In the present invention, it is preferable to use a vaporizer when heating the anhydrous aluminum chloride to sublimate or vaporize the aluminum chloride gas. As the vaporizer, those generally used in metal organic vapor phase epitaxy (MOVPE) can be used, and specifically, a temperature-controllable heating means for sublimating or vaporizing at least contained anhydrous aluminum chloride. And a carrier gas supply pipe for supplying a carrier gas for transporting the aluminum chloride gas, and a discharge pipe for discharging the aluminum chloride gas together with the carrier gas to the outside of the vaporizer. Anhydrous aluminum chloride is a solid powder at room temperature and easily absorbs moisture in the air to cause hydrolysis, so when filling the vaporizer, keep the anhydrous aluminum chloride away from the atmosphere. Need to work within. In addition, when filling an anhydrous aluminum chloride into a vaporizer, it is good to perform the dehydration process which heats for about 0.5 to 1 hour at about 120 degreeC previously.

For the aluminum chloride gas sublimated or vaporized by the vaporizer, an inert gas such as N ₂ , He, Ar, etc., and an AlCl ₃ carrier gas made of one or a combination selected from the group consisting of H ₂ are used. Then, it is discharged to the outside of the vaporizer and reacted with NH ₃ gas supplied separately by hydride vapor phase growth to grow AlN on the substrate. Hydride vapor phase growth is faster than other vapor phase growth methods such as metal organic vapor phase epitaxy (MOVPE), and the target material does not contain carbon. There is a feature that can be obtained. Regarding the temperature at which the aluminum chloride gas and NH ₃ gas are reacted by the hydride vapor phase growth method, the temperature on the substrate on which AlN crystal grows is preferably 1000 to 1200 ° C.

When reacting the aluminum chloride gas and the NH ₃ gas, it is preferable to use a reaction tube, preferably a quartz reaction tube. There is no particular limitation on the means for heating to a temperature for reacting the aluminum chloride gas and NH ₃ gas, and the reaction tube itself may be heated to a predetermined temperature by a hot wall method. Alternatively, only the substrate may be heated by a cold wall method. Then, for example, for the above reaction tube, for supplying the aluminum chloride gas and aluminum gas supply pipe chloride, and NH ₃ gas supply port for supplying the NH ₃ gas, for holding a substrate to crystal growth of AlN The reaction tube is provided with a temperature-controllable heating means provided with a substrate holding means and a discharge port for discharging the gas in the reaction tube, and in particular when a hot wall system is adopted so as to cover the side surface of the reaction tube. The device should be configured.

In addition, as the NH ₃ gas in the present invention, it is preferable to use a semiconductor grade gas generally used in the semiconductor manufacturing field. When this NH ₃ gas is supplied into the reaction tube, an inert gas such as N ₂ , He, Ar or the like, and an NH ₃ carrier gas made of one or a combination selected from the group consisting of H ₂ are used. You may make it introduce.

In the present invention, for a substrate (initial substrate) on which an AlN semiconductor is crystal-grown, sapphire (Al ₂ O ₃ ), silicon carbide (SiC), and gallium nitride (GaN) that are generally used in vapor phase growth are used. A substrate or the like can be used. For example, in sapphire, (0001) can be used as a crystal growth surface for growing an AlN crystal. When the aluminum chloride gas and NH ₃ gas are reacted in the reaction tube, it is preferable to arrange the tip of the aluminum chloride gas supply tube closer to the substrate than the NH ₃ gas supply port. The distance L between the tip of the supply tube and the crystal growth surface of the substrate is preferably 10 to 100 mm. Further, from the viewpoint of making the growth thickness of the AlN film obtained uniform, the crystal growth surface of the substrate is preferably perpendicular to the flow of aluminum chloride gas and NH ₃ gas.

  According to the present invention, an AlN semiconductor can be manufactured by crystal growth of AlN on a substrate. This AlN semiconductor can be mixed crystal by mixing elements such as Ga, B, In and the like at an arbitrary ratio as necessary. May be formed.

According to the present invention, since the AlN semiconductor can be crystal-grown on the substrate by directly reacting the aluminum chloride gas and the NH ₃ gas, the AlN semiconductor manufacturing method by the conventional hydride vapor phase growth method, High purity metal Al is reacted with HCl in the raw material part of the quartz reaction tube to produce Al halide (gas), and this Al halide is transported to the reaction part of the quartz reaction tube and reacted with NH ₃ gas. Thus, it is possible to fundamentally solve the problem that AlCl gas or AlCl ₂ gas corrodes the quartz reaction tube, which has been a problem in the method of vapor phase growth of AlN. In addition, since it is not necessary to strictly control the temperature in the raw material part of the quartz reaction tube, which has been performed in order to preferentially generate AlCl ₃ by the conventional method, it is not necessary to provide this raw material part. Such a device itself can be further simplified and miniaturized, and the degree of freedom of design is increased. Furthermore, the vapor pressure P ⁰⁰ _{AlCl 3} (T) of the aluminum chloride gas can be changed by adjusting the heating temperature of anhydrous aluminum chloride (AlCl ₃ ), and the partial pressure P ⁰ _{AlCl 3} of the aluminum chloride gas can be varied over a wide range. Therefore, the control of the growth rate of AlN can be selected more easily and in a wide range.

In addition, the AlN semiconductor obtained by the production method of the present invention was obtained by sublimation or vaporization of high-purity anhydrous aluminum chloride (AlCl ₃ ), in addition to preventing Si contamination due to corrosion of the quartz reaction tube. By using aluminum chloride gas, contamination of impurities such as Mg, Na, K, Ca, Cr, Fe, Zn, C, O, and H ₂ O, which are considered to have a particularly bad influence on device characteristics, is made possible. It is an AlN semiconductor that can be reduced, has high purity, and excellent crystallinity.

  Hereinafter, based on an Example and a comparative example, this invention is demonstrated more concretely.

FIG. 2 shows an AlN semiconductor manufacturing apparatus X used in the AlN semiconductor manufacturing method of the present invention. This AlN semiconductor manufacturing apparatus X is a reaction tube comprising a horizontal quartz reaction tube 1 having an inner diameter of 60 mm and a length of 1000 mm and a temperature-controllable reaction tube heating means 7 provided so as to surround the outer peripheral side surface of the quartz reaction tube 1. A vaporizer 9 having a volume of 1500 cm ³ is connected to the device 8 via a sorting device 14. This quartz reaction tube 1 has an NH ₃ gas supply port 2 for supplying NH ₃ gas to one end thereof, an aluminum chloride gas supply tube 3 for supplying aluminum chloride gas to the inside thereof, and a reaction on the other end side. A discharge port 4 for discharging the gas inside the tube and a substrate holding means 6 for holding a substrate (initial substrate) 5 for crystal growth of AlN inside the reaction tube are provided. The vaporizer 9 can heat solid anhydrous aluminum chloride (AlCl ₃ ) 11 filled therein from a supply port (not shown) by means of a temperature-controllable vaporizer heating means 10 provided so as to surround the outer periphery of the vaporizer 9. In addition, a carrier gas supply pipe 12 for supplying a carrier gas therein and a discharge pipe 13 for discharging the sublimated aluminum chloride gas to the outside of the vaporizer 9 are provided. A valve x ₁ and a valve x ₂ capable of ON / OFF control of the gas are provided at one end of the carrier gas supply pipe 12 and the discharge pipe 13 exposed to the outside.

The distribution device 14 that connects the reaction tube device 8 and the vaporizer 9 is composed of a piping system having openings A ₁ , A ₂ , B ₁ , B ₂ , and B ₃ . Among these, the opening A ₂ is connected to the tip of the carrier gas supply pipe 12 of the vaporizer 9 via the joint portion 15 a so that the carrier gas flowing from the opening A ₁ is supplied to the vaporizer 9. A carrier gas pipe 16 is provided. The opening B ₁ is connected to the tip of the discharge pipe 13 of the vaporizer 9 via a joint 15b, and the aluminum chloride gas sublimated in the vaporizer 9 is transported together with the carrier gas via the aluminum chloride gas transport pipe 17. Then, the opening B ₂ is connected to one end of the aluminum chloride gas supply pipe 3 of the reaction tube device 8 so that the aluminum chloride gas is supplied into the quartz reaction tube 1. Further, the carrier gas pipe 16 branches in the middle of the opening A ₁ and is bypassed to the aluminum chloride gas transport pipe 17, and a waste pipe 18 having an opening B ₃ is provided at the end thereof. ing.

In addition, the valve x ₃ is in front of the opening A ₂ of the carrier gas pipe 16, and the valve x ₄ is in the middle of the aluminum chloride gas transport pipe 17 in front of the opening B ₁ of the aluminum chloride gas transport pipe 17. The valve x ₅ is located at the quartz reaction tube 1 side of the connection with the waste pipe 18 and is in the middle of the waste pipe 18 and bypasses the carrier gas pipe 16 and the aluminum chloride gas transport pipe 17. the valve x6 is, the front of the opening B ₃ is the end of and discard pipe 18 valve x ₇ is provided respectively, the valves are capable of oN-OFF control of both gases.

  Further, the aluminum chloride gas transport pipe 17 of the sorting device 14 and the exposed portion of the discharge pipe 13 of the vaporizer 9 are provided with pipe heating means 19 capable of temperature control. The temperature inside these pipes is set to be about 20 ° C. higher than the temperature of the aluminum chloride gas sublimated by the vaporizer 8.

An example of how to use the thus configured AlN semiconductor manufacturing apparatus X is as follows. First, in the standby state where the reaction between the aluminum chloride gas and the NH ₃ gas is not performed, the valves x ₃ , x ₁ , x ₂ , And x ₄ are sequentially closed, and then the valve x ₆ is opened and the carrier gas is allowed to flow from the opening A1, while the valve x ₅ is opened and the valve x ₇ is closed and the carrier gas flows into the quartz reaction tube 1. Keep it as In actual crystal growth of AlN, the valves x ₄ , x ₂ , x ₃ , and x ₁ are sequentially opened from the standby state, and then the valve x ₆ is closed and the carrier gas is supplied to the vaporizer 9 side. To do. When terminating the crystal growth of AlN, the valve x ₆ is opened, the valves x ₃ , x ₁ , x ₂ , and x ₄ are sequentially closed so that the carrier gas flows directly into the quartz reaction tube 1, Return to the standby state again. Here, if the remaining amount of anhydrous aluminum chloride charged in the vaporizer 9 is less than a predetermined value, the vaporizer 9 is removed at the joint portions 15a and 15b, filled with anhydrous aluminum chloride, and newly prepared separately. Replace with the vaporizer 9. After a new vaporizer 9 is attached, open the valve x _7, after closing the valves x _5, while exhausting the carrier gas from the opening B ₃ by opening the valve x ₃ and the valve x _4, vaporizing All of the air that may have entered the sorting device 14 during replacement of the container 9 is removed. Then, opening the valve x ₅ by closing the valve x ₃ and x _4, leave again returned to the standby state by closing the valve x _7, when resuming the crystal growth of AlN is repeating the same procedure as above Good.

Using such an AlN semiconductor manufacturing apparatus X, AlN was crystal-grown. A sapphire substrate (0001) 5 having a diameter of 2 inches and a thickness of 400 μm is attached to the tip of the substrate holding means 6 so that the distance L from the tip of the aluminum chloride gas supply pipe 3 is 80 mm. The sapphire substrate 5 is provided such that (0001) is perpendicular to the flow of NH ₃ gas and AlCl ₃ gas, and AlN is crystal-grown using this (0001) as a crystal growth surface. The temperature on the sapphire substrate 5 is set to 1200 ° C. by the reaction tube heating means 7. The sapphire substrate 5 is etched for 5 minutes using an aqueous ammonia solution before being placed in the quartz reaction tube 1.

On the other hand, the vaporizer 9 is filled with 400 g of flaky anhydrous aluminum chloride having the impurity components shown in Table 1 using a probe box (not shown) so as not to be exposed to the atmosphere, and is vaporized by the vaporizer heating means 10. The anhydrous aluminum chloride 11 in the vessel 9 is heated to 120 ° C. The anhydrous aluminum chloride was obtained by performing a dehydration treatment by heating at 120 ° C. for 1 hour in advance before filling the vaporizer 9. Further, N ₂ is supplied as a carrier gas from the opening A1 of the distribution device 14, and the AlN crystal growth is performed from the standby state described above for each of the valves x ₁ to ₇ of the distribution device 14 and the vaporizer 9. An N ₂ carrier gas containing aluminum chloride gas sublimated in the vaporizer 9 is transported into the quartz reaction tube 1 at a carrier gas supply rate of FLOW _AlCl 3 carrier = 3800 ml / min. The partial pressure P ⁰ _AlCl ^{3 of the} aluminum chloride gas in the reaction part for crystal growth was _adjusted to 5 × 10 ⁻³ atm.

Further, NH ₃ gas (manufactured by Taiyo Nippon Sanso Corporation: Superammonia) is supplied from the NH ₃ gas supply port 2 of the quartz reaction tube 1 using N ₂ as a carrier gas, and the carrier containing this NH ₃ gas is supplied. The gas supply amount FLOW _NH 3 carrier was set to 1500 ml / min, and the partial pressure P ⁰ _NH3 of NH ₃ gas in the reaction part for crystal growth of AlN on the sapphire substrate 5 was set to 1 × 10 ⁻¹ atm. Under such circumstances, the total pressure in the horizontal quartz reaction tube 1 was set to 1.0 atm, and the reaction was carried out for 1 hour to grow AlN on the crystal growth surface (0001) of the sapphire substrate 5 to produce an AlN semiconductor. P ⁰ _{NH 3} / P ⁰ _{AlCl 3} in this reaction was 20, the film thickness of AlN grown on the crystal growth surface of the sapphire substrate 5 was 82 μm, and the growth rate of AlN was 82 μm / h.

[Examples 2 to 8]
Using the AlN semiconductor manufacturing apparatus X used in Example 1, the heating temperatures of anhydrous aluminum chloride in the vaporizer 8 were 50 ° C., 70 ° C., 80 ° C., 90 ° C., 100 ° C., 110 ° C., 120 ° C., respectively. And AlN were grown on the sapphire substrate 5 in the same manner as in Example 1 except that the temperature was set to 130 ° C. (Examples 2 to 8). That is, in Examples 2 to 8, the partial pressure P ⁰ _NH3 of NH ₃ gas in the reaction part is 1 × 10 ⁻¹ atm, and the partial pressure P ⁰ _{AlCl 3} in the reaction part of aluminum chloride gas is the heating temperature of anhydrous aluminum chloride. By adjusting, the vapor pressure P ⁰⁰ _{AlCl 3} (T) of aluminum chloride was changed to the values shown in Table 2 below. As a result, the crystal growth of AlN in each of Examples 2 to 8 is as shown in Table 2 and FIG. 3, and by adjusting the heating temperature of anhydrous aluminum chloride, including the result in Example 1 above. It was confirmed that the growth rate of AlN can be controlled.

[Comparative Example 1]
FIG. 4 shows a reaction tube apparatus 20 for producing an AlN semiconductor by a conventional hydride vapor phase growth method. The reaction tube device 20 according to the conventional method includes a horizontal quartz reaction tube 21 having an inner diameter of 60 mm and a length of 1500 mm, and the surrounding quartz so as to surround an outer peripheral surface of approximately half of the length of the horizontal quartz reaction tube 21 in the length direction. The first heating means 25a for forming the raw material portion in the quartz reaction tube 21 by controlling the temperature of the region in the reaction tube 21 to the following predetermined temperature, and the outer peripheral surface of the remaining half of the quartz reaction tube 21 are surrounded. The region within the quartz reaction tube 21 surrounded in this way is heated from the end of the horizontal quartz reaction tube 21 and the second heating means 25b for controlling the heating so that the following predetermined temperature is reached. It is supplied but the NH ₃ gas supply pipe 22 for supplying the NH ₃ gas at a position to reach the reaction part of the quartz reaction tube 21, the HCl gas also provided from one end of the quartz reaction tube 21 to the feed section of the quartz reaction tube 21 An HCl gas supply port 23, a discharge port 24 for discharging the gas in the quartz reaction tube 21 provided at the other end of the horizontal quartz reaction tube 21, and a substrate on which AlN is crystal-grown in the reaction part of the quartz reaction tube 21 The substrate holding means 26 for holding the (initial substrate) 27, and the same sapphire (0001) substrate 27 as that of the first embodiment is formed at the tip of the substrate holding means 26 as in the first embodiment, and NH ₃ It is attached so that the distance from the gas supply pipe 22 is L = 60 mm. The raw material part of the quartz reaction tube 21 is provided with an Al boat 28 made of alumina containing metal Al. The Al boat 28 contains 98 g of metal Al (6NAl) having a purity of 99.9999% by weight. ing.

Then, HCl gas (purity 99.999 wt%) is supplied from the HCl supply pipe 13 at a flow rate of 150 ml / min with the total pressure in the horizontal quartz reaction tube 21 being 1.0 atm and the temperature of the raw material section being 550 ° C. did. The HCl gas was introduced with N ₂ as a carrier gas. In the raw material part, HCl gas reacts with metal Al to generate AlCl ₃ gas, and this AlCl ₃ gas is transported to the reaction part side. On the other hand, in the reaction part of the quartz reaction tube 21, the temperature of the crystal growth surface of the sapphire substrate 27 is set to 1180 ° C., and the AlCl ₃ gas generated in the raw material part and the NH ₃ supply pipe 22 are supplied at a flow rate of 1000 ml / min. Reaction with the supplied NH ₃ gas (manufactured by Taiyo Nippon Sanso Co., Ltd .: Superammonia) caused AlN having a film thickness of 60 μm to grow on the sapphire substrate 27. The reaction time from the supply of HCl gas in the raw material portion to the stop of AlN crystal growth on the sapphire substrate 27 was 1.5 hours, and the growth rate of AlN was 40 μm / h.

[Comparative Example 2]
An AlN semiconductor was manufactured by crystal growth of 3.7 μm thick AlN in the same manner as in Comparative Example 1 except that the flow rate of HCl gas was 10 ml / min.

[X-ray diffraction of AlN]
FIG. 5 shows the result of analyzing the crystal structure of the AlN film grown on the sapphire substrate in Example 1 by X-ray diffraction. For the measurement, X'pert MRD manufactured by Spectris was used, and the measurement conditions were 45 kV and 40 mA. As for the obtained diffraction peak, the FWHM (half-value width) of AlN (0002) has a narrow tilt angle of 15 arcmin, and there is no diffraction peak other than (000 n), so that an AlN epitaxial film can be grown by the manufacturing method of the present invention. Can be confirmed.

[AlN UV absorption spectrum]
The ultraviolet absorption spectrum of AlN obtained in Example 1 is shown in FIG. A V-7300 type UV-Vis near-infrared spectrophotometer manufactured by JASCO Corporation was used for the measurement. From this, it can be confirmed that steep absorption has started from around 6.1 eV and AlN has grown.

[Analysis of AlN by TOF-SIMS]
For the AlN obtained in Example 5 and the AlN film obtained in Comparative Example 1, analysis of impurities present in each AlN film using a time-of-flight secondary ion mass spectrometer (Time of flight SIMS: TOF-SIMS) Went. Since this TOF-SIMS can qualitatively analyze trace element elements present on the extreme surface (about 10 nm from the surface), AlN obtained by the AlN semiconductor manufacturing method of the present invention and the conventional method (Comparative Example 1) It is suitable for comparing the degree of impurity contamination with AlN obtained in (1). The equipment used was TRIFT III (manufactured by Physical Electronics), and the analysis conditions were as follows. Primary ions: Ga ⁺ , Cs ⁺ , acceleration voltage: 15 kV, current: 600 pA (as DC), sputtering area: 300 μm × 300 μm, sputtering time: 1 min, analysis area: 200 μm × 200 μm, integration time: 3 min, and detection ions: The analysis was performed after sputtering for 1 minute with Cs ions from the outermost surface of AlN.

  7 to 11 are positive ion detection enlarged spectra in the vicinity of the mass of each element of Si, Mg, Na, Ca, and K. FIG. 7 to 11, the upper (A) shows the results for AlN obtained in Comparative Example 1, and the lower (B) shows the results for AlN obtained in Example 5. Table 3 summarizes the results including analysis results other than these elements. Table 3 shows the peak intensities obtained by sputtering and analyzing with Ga ions and normalized by the peak intensity of each element and the intensity of Al in the matrix. In the table, “M / Z” represents a mass number.

  As apparent from FIGS. 7 to 11 and Table 3, Si, Mg, Na, Ca, and K were detected from the AlN film obtained in Comparative Example 1, but from the AlN film obtained in Example 5. These elements were hardly detected. Table 4 shows the analysis results of Al and Ga when sputtering and analyzing with Cs ions. From Table 4, it can be seen that the detected amount of Ga is 1/4 in the AlN obtained in Example 5 as compared with the AlN in Comparative Example 1.

[Analysis of AlN by D-SIMS]
The AlN obtained in Example 3 and the AlN obtained in Comparative Example 2 were analyzed for impurities present in the respective AlN films by D-SIMS (Dynamic-SIMS). The apparatus used was ATOMICA SIMS4100 manufactured by ATOMICA, and the measurement conditions were as follows. Primary ion species: Cs (superscript: +), primary acceleration voltage: 7 kV, beam current: 83 nA, scan width: 150 μm, detected ions: (superscript: 12) C (superscript: +), (superscript: 18) O (superscript : +), (Superscript: 28) Si (superscript: +), (superscript: 55) AlN (subscript: 2) (superscript: +), (superscript: 81) Al (subscript: 3) (superscript: +), Each of the conditions. FIG. 12 shows a profile obtained from AlN of Example 3, and FIG. 13 shows a profile obtained from AlN of Comparative Example 2. 12 and 13, the vertical axis represents the secondary ion signal intensity, the horizontal axis represents the depth from the surface of the AlN film, and the outermost surface of the AlN film was 0 μm. For the horizontal axis, the depth of the sputter trace is measured with a surface roughness meter, and converted into depth based on the time of sputtering with Cs ions from the surface of the AlN film to the sapphire substrate in the depth direction. . Further, for comparison of the amount of the analytical element, normalization is performed with the (superscript: 18) O intensity in the sapphire substrate. When both were compared, it was found that the strengths of O, C, and Si were less in AlN obtained in Example 3, and it was confirmed that the production method in the present invention was superior to the conventional method.

According to the present invention, an AlN semiconductor can be produced by directly reacting an aluminum chloride gas obtained by sublimating anhydrous aluminum chloride (AlCl ₃ ) with NH ₃ gas. Since the apparatus itself can be reduced in size and simplified, and the crystal growth of AlN can be controlled freely and easily, a large-diameter AlN semiconductor can be obtained by taking advantage of the hydride vapor phase growth method. Therefore, the present invention is an extremely effective invention for industrial application as an AlN semiconductor manufacturing method.

  In addition, since the AlN semiconductor obtained by the present invention eliminates contamination of impurities as much as possible, and can particularly prevent the entry of elements that are adversely affected by device characteristics, it can be used in general precision processing and medical fields. High-efficiency deep ultraviolet laser diodes that can be expected to be used in a wide range of applications, optical storage with high recording density, high-power white LEDs utilizing the high thermal conductivity of AlN, and substrates for manufacturing high-power and high-frequency electronic devices Various applications such as materials can be expected.

FIG. 1 shows the vapor pressure curve of aluminum chloride. FIG. 2 is a cross-sectional explanatory view of the AlN semiconductor manufacturing apparatus of the present invention. FIG. 3 shows the relationship between the heating temperature of anhydrous aluminum chloride and the growth rate of AlN. FIG. 4 is a cross-sectional explanatory view of a conventional reaction tube apparatus for producing an AlN semiconductor by hydride vapor phase epitaxy. FIG. 5 is an X-ray diffraction pattern of AlN grown on the sapphire substrate in Example 1. FIG. 6 shows the ultraviolet absorption spectrum of AlN obtained in Example 1. FIG. 7 is an enlarged spectrum of positive ion detection around the mass of Si obtained by analysis by TOF-SIMS. The upper part (A) is the result of analysis of AlN obtained in Comparative Example 1, and the lower part (B) is the result of analysis of AlN obtained in Example 5. FIG. 8 is an enlarged spectrum of positive ion detection around the mass of Mg obtained by analysis by TOF-SIMS. The upper part (A) is the result of analysis of AlN obtained in Comparative Example 1, and the lower part (B) is the result of analysis of AlN obtained in Example 5. FIG. 9 is an enlarged spectrum of positive ion detection near the mass of Na obtained by analysis by TOF-SIMS. The upper part (A) is the result of analysis of AlN obtained in Comparative Example 1, and the lower part (B) is the result of analysis of AlN obtained in Example 5. FIG. 10 is an enlarged spectrum of positive ion detection around the mass of Ca obtained by analysis by TOF-SIMS. The upper part (A) is the result of analysis of AlN obtained in Comparative Example 1, and the lower part (B) is the result of analysis of AlN obtained in Example 5. FIG. 11 is a positive ion detection enlarged spectrum around the mass of K obtained by analysis by TOF-SIMS. The upper part (A) is the result of analysis of AlN obtained in Comparative Example 1, and the lower part (B) is the result of analysis of AlN obtained in Example 5. FIG. 12 is a D-SIMS profile of AlN obtained in Example 3. FIG. 13 is a D-SIMS profile of AlN obtained in Comparative Example 2.

X: AlN semiconductor manufacturing apparatus, 1: horizontal quartz reaction tube, 2: NH ₃ gas supply port, 3: aluminum chloride gas supply tube, 4: discharge port, 5: sapphire substrate, 6: substrate holding means, 7: reaction tube Heating means, 8: reaction tube apparatus, 9: vaporizer, 10: vaporizer heating means, 11: anhydrous aluminum chloride (AlCl ₃ ), 12: carrier gas supply pipe, 13: discharge pipe, 14: sorting apparatus, 15a, 15b: joint, 16: carrier gas pipe, 17: aluminum gas transport pipe chloride, 18: discarded piping, 19: piping heating means, 20: reaction tube device, 21: horizontal quartz reaction tube, 22: NH ₃ gas supply tube 23: HCl gas supply port, 24: discharge port, 25a: first heating unit, 25b: second heating unit, 26: substrate holding unit, 27: sapphire substrate, 28: Al boat, A ₁ , A ₂ , B _1, B _2, B _3: opening, x _{1, 2, x 3, x 4,} x 5, x 6, x 7: Valve.

Claims (4)

Anhydrous aluminum chloride whose total amount of impurity components other than Group III elements is 0.001% by weight or less is heated and sublimated or vaporized to react with NH ₃ gas by a hydride vapor phase growth method, on the substrate. A method for producing an AlN semiconductor for electronic devices, characterized in that AlN is crystal-grown.   The method for producing an AlN semiconductor according to claim 1, wherein the purity of anhydrous aluminum chloride is 99.999% by weight or more.   The method for producing an AlN semiconductor according to claim 1 or 2, wherein the growth rate of AlN is controlled by adjusting the heating temperature of anhydrous aluminum chloride in a range of 50 to 180 ° C.   The method for producing an AlN semiconductor according to any one of claims 1 to 3, wherein anhydrous aluminum chloride preliminarily heated and dehydrated is filled in a vaporizer and sublimated or vaporized.

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