JP5052174B2 - Zinc oxide based semiconductor manufacturing method and zinc oxide based semiconductor manufacturing apparatus - Google Patents

Description

  The present invention relates to a method for manufacturing a zinc oxide based semiconductor by an HVPE (Halide Vapor Phase Epitaxy) method and an apparatus for manufacturing a zinc oxide based semiconductor.

  A zinc oxide-based semiconductor is a direct transition type semiconductor with a band gap of 3.3 eV, and the binding energy of excitons in which holes and electrons are combined in a solid is as large as 60 meV, which is stable even at room temperature. It is expected as a light emitting device from the blue region to the ultraviolet region that is inexpensive and has a low environmental impact. In addition to light emitting devices, zinc oxide based semiconductors are also expected for applications such as light receiving elements, piezoelectric elements, and transparent electrodes. For this reason, the request of the manufacturing method and manufacturing apparatus of the high quality zinc oxide type semiconductor excellent in mass productivity is increasing.

  The following methods are known as methods for producing high-quality zinc oxide-based semiconductors. For example, in the molecular beam epitaxy method (hereinafter referred to as MBE method), zinc and radicalized (plasmaized) oxygen are supplied as molecular beams and reacted on a growth substrate to grow a high-quality zinc oxide-based semiconductor. ing. In the pulsed laser deposition method (hereinafter referred to as PLD method), high-quality zinc oxide is deposited on a growth substrate by depositing a zinc oxide-based semiconductor evaporated by irradiating a sintered body or crystal of the zinc oxide-based semiconductor with a laser. Growing semiconductors.

  However, when growing a zinc oxide based semiconductor by the MBE method and the PLD method described above, it is necessary to perform growth in a high vacuum in order to grow a beam-like material on a growth substrate. There is a problem that it is difficult to mass-produce.

  Therefore, as a method for producing a zinc oxide semiconductor that does not require high vacuum, a zinc oxide semiconductor is grown by metal organic vapor deposition (hereinafter referred to as MOCVD), which is widely used for crystal growth of III-V semiconductors. The method of making it known is known. In the MOCVD method, an organic metal material containing zinc is decomposed on a growth substrate into zinc and a hydrocarbon group, and then a zinc oxide based semiconductor is grown.

  However, in the MOCVD method described above, since the vapor pressure of zinc, which is a group II element, is very high compared to group III elements, even if zinc reaches the growth substrate at a high temperature capable of high quality growth, the growth substrate Easy to leave. For this reason, since the ratio of zinc that can contribute to the growth of the zinc oxide based semiconductor on the growth substrate is small, there is a problem that the efficiency of the material containing zinc is low. Further, since carbon is mixed into the zinc oxide-based semiconductor due to hydrocarbon groups generated when the organometallic material containing zinc is decomposed, there is a problem that it is difficult to grow a zinc oxide-based semiconductor not containing carbon.

  Therefore, as an industrial manufacturing method of a zinc oxide semiconductor that does not require a carbon-containing material, a halide (or hydride) vapor phase growth method (hereinafter referred to as HVPE method) using a halogenated group II metal as a group II material is used. A method for growing a zinc oxide-based semiconductor has been proposed. The HVPE method is known as a III-V group semiconductor manufacturing method for industrially manufacturing a gallium nitride substrate or the like by using a halide (chloride) as a group III material and a hydride as a group V material. It has been. In this HVPE method, a hot wall system is generally used in which a quartz tube is applied to a growth zone in which a zinc oxide based semiconductor is grown by a chemical reaction, and not only the growth substrate and its periphery but also the quartz tube is heated to a high temperature.

  Here, when a zinc oxide based semiconductor is grown by the HVPE method, it can be grown under conditions closer to the equilibrium state than the MBE method or MOCVD method, so the ratio of zinc contributing to the growth of the zinc oxide based semiconductor is improved. Can be made.

In the case of growing a zinc oxide based semiconductor by a vapor phase epitaxy (VPE) method, it is known as one method to use a zinc metal simple substance and an oxygen material containing oxygen (for example, oxygen) as materials. However, the equilibrium constant of this chemical reaction is larger than the equilibrium constant of the III-V group semiconductor, and it is necessary to set the supply partial pressure of zinc having a high vapor pressure high for high-temperature growth as described above. Therefore, there is a problem that it is difficult to control the reaction. Therefore, Patent Document 1 discloses a method using zinc chloride and an oxygen material as another method for growing a zinc oxide based semiconductor by the VPE method. In this method of manufacturing a zinc oxide based semiconductor in Patent Document 1, zinc chloride powder is placed in a reaction tube and heated to transport zinc chloride vaporized by a carrier gas and react with oxygen to produce a zinc oxide based semiconductor. Growing semiconductors.
N. Takahashi, et al. “Atomospheric pressure vapor-phase growth of ZnO using chloride source”, Journal of Crystal Growth. 209 (2000) pp. 822-827.

  However, in the above-described method for producing a zinc oxide semiconductor of Patent Document 1, zinc chloride is used as a zinc material. Zinc chloride has deliquescence and the purity of easily available zinc chloride is about 99.9. Since zinc chloride having a low purity of about% and high purity is expensive, there is a problem that a high-quality zinc oxide-based semiconductor cannot be easily manufactured.

  The present invention was created to solve the above-described problems, and an object of the present invention is to provide a method for manufacturing a zinc oxide-based semiconductor and an apparatus for manufacturing the same that can easily manufacture a high-quality zinc oxide-based semiconductor. .

  To achieve the above object, the invention according to claim 1 is a first step of generating a group II metal halide by reacting a group II metal material containing a metal element of zinc and a halogen gas in a raw material zone. A second step of supplying an oxygen material containing oxygen to the growth zone; a third step of transporting the Group II metal halide from the source zone to the growth zone; the Group II metal halide and the And a fourth step of growing a zinc oxide based semiconductor on a growth substrate by reacting an oxygen material in the growth zone.

  The invention according to claim 2 is the method for producing a zinc oxide based semiconductor according to claim 1, wherein the supply partial pressure of hydrogen is set to be equal to or lower than the supply partial pressure of the group II metal halide. .

  The invention according to claim 3 is characterized in that the supply partial pressure of hydrogen is set to 1/10 or less of the supply partial pressure of the group II metal halide. It is a manufacturing method.

  The invention according to claim 4 is the production of a zinc oxide based semiconductor according to any one of claims 1 to 3, wherein the fourth step is performed at a temperature of 500 ° C or higher. Is the method.

  The invention according to claim 5 is the zinc oxide according to any one of claims 1 to 4, wherein the first step is performed at a temperature lower than that of the fourth step. This is a method for manufacturing a semiconductor.

  The invention according to claim 6 is the method for producing a zinc oxide-based semiconductor according to any one of claims 1 to 5, wherein the group II metal material contains a single metal of magnesium. is there.

  The invention according to claim 7 is the method for producing a zinc oxide based semiconductor according to any one of claims 1 to 6, wherein the oxygen material is water.

  The invention according to claim 8 is the method for producing a zinc oxide based semiconductor according to any one of claims 1 to 7, wherein the halogen gas is chlorine gas or bromine gas. .

  The invention according to claim 9 is a first raw material zone in which a first group II metal material containing a single metal of zinc is held, and a halogen gas supply means for supplying a halogen gas to the first raw material zone. An oxygen material supply means for supplying an oxygen-containing oxygen material; and a growth zone for reacting the halogen gas and a group II metal generated from the group II metal material with the oxygen material. Is a manufacturing apparatus for a zinc oxide based semiconductor.

  The invention according to claim 10 further comprises a second raw material zone in which a second group II metal material containing a group II metal simple substance other than zinc is held. This is a zinc-based semiconductor manufacturing apparatus.

  According to the present invention, since a zinc simple substance that can be easily obtained with high purity is used as the Group II metal material instead of zinc chloride, which is difficult to obtain high purity, A quality zinc oxide based semiconductor can be easily manufactured.

(First embodiment)
Hereinafter, a first embodiment in which the present invention is applied to a method of manufacturing a zinc oxide semiconductor and an apparatus for manufacturing the same will be described with reference to the drawings. FIG. 1 is an overall view of a zinc oxide semiconductor manufacturing apparatus according to the present invention.

  First, with reference to FIG. 1, the manufacturing apparatus of the zinc oxide semiconductor by HVPE method is demonstrated.

  As shown in FIG. 1, the zinc oxide semiconductor manufacturing apparatus 1 according to the first embodiment includes a chlorine gas supply means 2, a carrier gas supply means 3, a raw material zone 4, a heating means 5, and a water supply means 6. The carrier gas supply means 7, the growth zone 8, the heating means 9, the substrate holding means 10, and the hydrogen supply means 11 are provided.

  The raw material zone 4 is for holding a group II metal material 15 made of zinc metal alone. The raw material zone 4 is a zone in which the chlorine gas supplied from the chlorine gas supply means 2 and zinc are reacted to generate zinc chloride gas.

  In the growth zone 8, the zinc chloride gas supplied from the raw material zone 4 connected by the supply pipe reacts with the water (water vapor) supplied from the water supply means 6 as an oxygen material, and held in the substrate holding means 10. In this zone, a zinc oxide semiconductor is grown on the grown substrate 16. Note that hydrogen for adjusting the driving force described later is supplied from the hydrogen supply means 11 to the growth zone 8. Here, the hydrogen supplied from the hydrogen supply means 11 easily reacts with the chlorine gas, so that it is supplied to the growth zone 8 through a supply path different from the chlorine gas.

  The raw material zone 4, the growth zone 8, and each supply pipe connecting each gas supply means and the growth zone 8 are made of quartz.

  The heating means 5 is for heating the raw material zone 4 and the water supply path. The heating means 9 is for heating the growth zone 8. By these heating means 5 and 9, the manufacturing apparatus 1 realizes a hot wall system.

  The nitrogen gas supplied from the carrier gas supply means 3 and 7 is for transporting the zinc chloride gas generated in the raw material zone 4 and the water supplied from the water supply means 6 to the growth zone 8.

  Next, the manufacturing method of the zinc oxide semiconductor by the manufacturing apparatus mentioned above is demonstrated.

First, chlorine gas and nitrogen gas are transported to the raw material zone 4 from the chlorine gas supply means 2 and the carrier gas supply means 3, respectively. In the raw material zone 4, the reaction according to the following reaction formula (1) occurs by the group II metal material 15 made of the zinc simple metal and the supplied chlorine gas, and zinc chloride gas is generated. .
Zn (s, l) + Cl ₂ (g) ⇔ ZnCl ₂ (g) (1)
Here, the zinc simple substance held in the raw material zone 4 is preferably highly pure, for example, 99.99999% or more. In the reaction formula, (s), (l), and (g) represent solid, liquid, and gas, respectively.

  The raw material zone 4 allows the reaction in the reaction formula (1) to proceed almost to the right side, and the surface area of the group II metal material 15 made of zinc metal alone so that the flow rate of the zinc chloride gas can be controlled by the supply amount of the chlorine gas. The structure is increased and the temperature is appropriate. In addition, about 300 degreeC-about 450 degreeC is desirable as such suitable temperature. In addition, the temperature of the raw material zone 4 is set to about 500 ° C. or less in order to suppress the transport of zinc gas having a very high vapor pressure among the metals to the growth zone 8. Then, the zinc chloride gas generated by the above reaction formula (1) is transported to the growth zone 8 by the nitrogen gas supplied from the carrier gas supply means 3.

  Further, the water (water vapor) supplied from the water supply means 6 is transported to the growth zone 8 as an oxygen material by the nitrogen gas supplied from the carrier gas supply means 7 via another path.

In the growth zone 8, the reaction of the following reaction formula (2) proceeds to the right side by the transported zinc chloride gas and water, so that a zinc oxide semiconductor thin film grows on the growth substrate 16. The reaction of the following reaction formula (3) occurs by the hydrogen supplied from the hydrogen supply means 11. The supply partial pressure of hydrogen is set to be equal to or lower than the supply partial pressure of zinc chloride gas, or to 1/10 or less of the supply partial pressure of zinc chloride gas.
ZnCl ₂ (g) + H ₂ O (g) ⇔ZnO (s) + 2HCl (g) (2)
ZnCl ₂ (g) + H ₂ (g) Ｚｎ Zn (g) + 2HCl (g) (3)
Here, the temperature of the growth zone 8 is set to be higher than the temperature of the raw material zone 4 so that the zinc chloride gas does not precipitate on the way to the growth zone 8. Specifically, the temperature of the growth zone 8 is set to about 500 ° C. to about 1100 ° C.

  Although the details will be described later, the inventor of the present application can advance the reaction of the reaction formula (2) to the right side by controlling the supply partial pressure of hydrogen even at a high temperature (for example, about 1000 ° C. or higher). This is confirmed by thermodynamic analysis.

(Relationship between hydrogen supply partial pressure and driving force)
Next, the driving force of the reaction formula (2) is obtained from the equilibrium constants of the reaction formulas (2) and (3) and the storage conditions of each element, and a thermodynamic viewpoint regarding the relationship between the driving force and the supply partial pressure of hydrogen. From the theoretical explanation.

In the following formulas, P _* indicates the equilibrium partial pressure of each gas *. The equilibrium partial pressure is a partial pressure in an equilibrium state in the vicinity of the zinc oxide based semiconductor formed on the growth substrate. P ⁰ _* indicates a supply partial pressure when each gas * is supplied.

First, the equilibrium constant K ₁ of the reaction formula (2) is defined by the following “Equation 1”.

ここで、これらの平衡定数は、ギブスの自由エネルギーなどから求められる値である。 In addition, the equilibrium constant K ₂ in the reaction formula (3) is defined by the following “Equation 2”.

Here, these equilibrium constants are values obtained from Gibbs free energy and the like.

Further, the storage condition of chlorine is as shown in the following “Equation 3”.

Further, the storage condition of hydrogen is as shown in the following “Equation 4”.

Further, the constraint condition of the system relating to the precipitation of the zinc oxide semiconductor is as shown in the following “Equation 5”.

In addition, the pressure constraint condition of the system in the present embodiment is as shown in the following “Equation 6”. The left side shows the total pressure. In the case of atmospheric pressure, this total pressure is 760 torr.

These “Equation 1” to “Equation 6” are made simultaneous, and the relationship between the equilibrium partial pressure and the temperature of the six gas types is obtained from these equations. Then, the driving force D at each growth temperature is obtained by substituting the equilibrium partial pressure P _H2O of water into “Equation 7” shown below.

The result is shown in FIG. In FIG. 2, the vertical axis represents the normalized growth driving force, and the horizontal axis represents the growth temperature [° C.]. The standardized growth driving force referred to here is standardized by setting the driving force when the temperature of the growth zone is 500 ° C. to “1”. The four curves represent the driving force D when the hydrogen supply partial pressure P ⁰ _H2 is set to 100 torr, 10 torr, 1 torr, and 0.1 torr, as indicated by the subscript. The supply partial pressure P ⁰ _{ZnCl 2} of zinc chloride gas was set to 1 torr, and the supply partial pressure P ⁰ _{H 2 O} of water was set to 10 torr.

As shown in FIG. 2, when the hydrogen supply partial pressure P ⁰ _H2 is set to 0.1 torr, which is 1/10 of the zinc chloride gas supply partial pressure P ⁰ _{ZnCl 2} , the growth temperature is set to 1000 ° C. or higher. It can be seen that the driving force D is 0.5 or more, and the zinc oxide semiconductor can be grown even with a small amount of raw material. As is clear from FIG. 2, even when the hydrogen supply partial pressure P ⁰ _{H2 is set} to 1/10 or less of the zinc chloride gas supply partial pressure P ⁰ _{ZnCl 2} , the driving force D is at a growth temperature of 1000 ° C. or more. It becomes a positive number and it can be estimated that a zinc oxide semiconductor can be grown.

Further, when the hydrogen supply partial pressure P ⁰ _H2 is set to 1 torr which is the same as the zinc chloride gas supply partial pressure P ⁰ _{ZnCl 2} , the driving force D becomes positive even if the growth temperature is set to 800 ° C. or higher, and the zinc oxide semiconductor It can be seen that it can grow. When the hydrogen supply partial pressure P ⁰ _H2 is 0.1 torr, the hydrogen supply partial pressure P ⁰ _H2 is 1 torr (zinc chloride gas supply partial pressure P ⁰ _{ZnCl 2} ) or less. It can be estimated that a zinc oxide semiconductor can be grown at a growth temperature of 800 ° C. or higher. Furthermore, when the growth temperature is around 900 ° C., the driving force D can be controlled by controlling the hydrogen supply partial pressure P ⁰ _{H 2,} and the growth rate of a high-quality zinc oxide semiconductor can be controlled at a high temperature. It can be seen that this can be done easily.

  As described above, in the first embodiment, zinc simple metal that can be easily obtained with high purity is used as the group II metal material 15 instead of zinc chloride, which is difficult to obtain with high purity. Therefore, a high quality zinc oxide semiconductor can be easily manufactured.

In the first embodiment, a zinc oxide semiconductor is grown even at a growth temperature of 1000 ° C. or higher by setting the hydrogen supply partial pressure P ⁰ _H2 to 1/10 or less of the zinc chloride gas supply partial pressure P ⁰ _{ZnCl 2} . Therefore, a higher quality zinc oxide semiconductor can be grown.

In the first embodiment, a zinc oxide semiconductor is grown even at about 800 ° C. or higher by setting the hydrogen supply partial pressure P ⁰ _H2 to the same supply partial pressure as the zinc chloride gas supply partial pressure P ⁰ _{ZnCl 2} or less. Can be made. Further, the hydrogen supply partial pressure P ⁰ _H2 is set to the same supply partial pressure as the zinc chloride gas supply partial pressure P ⁰ _{ZnCl 2} , and the growth temperature is increased to about 900 ° C., so that the driving force D is reduced and the growth is continued. Since the speed can be reduced, the film thickness of the zinc oxide semiconductor can be easily controlled.

  Further, by making the set temperature of the raw material zone 4 lower than the growth temperature of the growth zone 8, it is possible to prevent the zinc chloride gas generated in the raw material zone 4 from being deposited before being transported to the growth zone 8. .

  Further, by adopting water instead of simple oxygen as the oxygen material, hydrochloric acid gas is generated in the growth zone 8 instead of chlorine gas. Therefore, the reaction formula (2) is advanced to the right side in a more thermodynamically stable state. be able to.

(Second Embodiment)
Next, a second embodiment in which the present invention is applied to an MgZnO semiconductor (zinc oxide-based semiconductor) manufacturing method and manufacturing apparatus will be described. FIG. 3 is a view showing an apparatus for manufacturing an MgZnO semiconductor according to the second embodiment. In addition, the same code | symbol is attached | subjected to the same structure as 1st Embodiment, and description is abbreviate | omitted.

  As shown in FIG. 3, the MgZnO semiconductor (zinc oxide semiconductor) manufacturing apparatus 1 </ b> A holds chlorine gas supply means 12, carrier gas supply means 13, and a group II metal material 25 containing magnesium metal alone. And a raw material zone 14.

  In the MgZnO semiconductor manufacturing method using the MgZnO semiconductor manufacturing apparatus 1 </ b> A, chlorine gas is transported to the raw material zone 14 together with the carrier gas, and magnesium chloride gas is generated in the raw material zone 14. Then, the magnesium chloride gas is transported to the growth zone 8 by the nitrogen gas supplied from the carrier gas supply means 13, and the zinc chloride gas, the magnesium chloride gas and water are reacted in the growth zone 8, whereby the MgZnO semiconductor is grown. 16 can be grown.

  As mentioned above, although this invention was demonstrated in detail using embodiment, this invention is not limited to embodiment described in this specification. The scope of the present invention is determined by the description of the claims and the scope equivalent to the description of the claims. Hereinafter, modified embodiments in which the above-described embodiment is partially modified will be described.

  For example, in the above-described embodiment, the magnesium metal element is employed as the group II metal material other than zinc, but cadmium may be employed as the group II metal material in addition to magnesium.

  In the above-described embodiment, water is used as the oxygen material, but oxygen gas may be used as the oxygen material instead of water.

  Moreover, in the above-mentioned embodiment, although chlorine gas was employ | adopted as halogen gas, you may employ | adopt bromine gas instead of chlorine gas.

  In the second embodiment described above, two types of Group II metal materials are used. However, the type of Group II metal materials is not limited to two types, and three or more Group II metal materials may be used. Good.

1 is an overall view of a zinc oxide semiconductor manufacturing apparatus according to a first embodiment of the present invention. It is a figure which shows the relationship between the growth temperature and driving force in the supply partial pressure of different hydrogen. It is a figure which shows the manufacturing apparatus of the MgZnO semiconductor (zinc oxide type semiconductor) by 2nd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Zinc chloride semiconductor manufacturing apparatus 1A Zinc chloride type semiconductor manufacturing apparatus 2 Chlorine gas supply means 3 Carrier gas supply means 4 Raw material zone 5 Heating means 6 Water supply means 7 Carrier gas supply means 8 Growth zone 9 Heating means 10 Substrate holding means 11 Hydrogen supply means 12 Chlorine gas supply means 13 Carrier gas supply means 14 Raw material zone 15 Group II metal material 16 Growth substrate 25 Group II metal material

Claims (10)

A first step of generating a group II metal halide by reacting a group II metal material including a metal element of zinc with a halogen gas in the raw material zone;
A second step of supplying an oxygen material containing oxygen to the growth zone;
A third step of transporting the Group II metal halide from the source zone to the growth zone;
A method for producing a zinc oxide-based semiconductor comprising: a fourth step of growing a zinc oxide-based semiconductor on a growth substrate by reacting the group II metal halide and the oxygen material in the growth zone. .   2. The method for producing a zinc oxide based semiconductor according to claim 1, wherein the supply partial pressure of hydrogen is set to be equal to or lower than the supply partial pressure of the group II metal halide.   The method for producing a zinc oxide based semiconductor according to claim 1, wherein the supply partial pressure of hydrogen is set to 1/10 or less of the supply partial pressure of the group II metal halide.   The method for producing a zinc oxide based semiconductor according to any one of claims 1 to 3, wherein the fourth step is performed at a temperature of 500 ° C or higher.   The method for producing a zinc oxide based semiconductor according to any one of claims 1 to 4, wherein the first step is performed at a temperature lower than that of the fourth step.   The said group II metal material contains the metal simple substance of magnesium, The manufacturing method of the zinc oxide type semiconductor of any one of Claims 1-5 characterized by the above-mentioned.   The said oxygen material is water, The manufacturing method of the zinc oxide type semiconductor of any one of Claims 1-6 characterized by the above-mentioned.   The said halogen gas is chlorine gas or bromine gas, The manufacturing method of the zinc oxide type semiconductor of any one of Claims 1-7 characterized by the above-mentioned. A first raw material zone in which a first Group II metal material containing a metal element of zinc is held;
Halogen gas supply means for supplying halogen gas to the first raw material zone;
Oxygen material supply means for supplying oxygen material containing oxygen;
An apparatus for producing a zinc oxide based semiconductor, comprising: a growth zone for reacting a halogenated group II metal generated from the halogen gas and the group II metal material with the oxygen material.   The apparatus for producing a zinc oxide based semiconductor according to claim 9, further comprising a second raw material zone in which a second group II metal material containing a group II metal simple substance other than zinc is held.

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