JPH0230694A - Vapor-phase epitaxial growth process - Google Patents

Abstract

PURPOSE:To perform a stable vapor-phase epitaxial growth of a good crystal by reacting HCl gas to iron obtained by the thermal decomposition of an Fe- containing organic compound and supplying the obtained iron chloride to effect the iron doping. CONSTITUTION:H2 gas containing ferrocene gas is passed through a ferrocene gas supplying tube 4. In the above process, the inside of the dopant-feeding tube 8 near the inlet of a heater 1 is heated to about >=450 deg.C with the heater 1 and the supplied ferrocene gas is thermally decomposed to deposit iron in the tube 8. The supply of ferrocene gas is stopped and HCl gas is introduced from the HCl-feeding tube 3 into the dopant-feeding tube 8. The supplied HCl gas reacts with the iron deposited in the tube 8 to form iron chloride, which is transferred to the surface of a wafer 7. InP is grown on the wafer in vapor- phase by the reaction of PCl3 supplied from an introduction tube 5 with In in a source boat 6 and the InP is doped with iron by the supplied iron chloride gas. An iron-doped epitaxial layer of InP having high resistance can be grown by this process.

Description

[Detailed Description of the Invention] [Industrial Application Field] The invention of this application relates to a vapor phase epitaxial growth method for doping a compound semiconductor with iron.

[Prior Art] For example, a vapor phase epitaxial growth method for compound semiconductors such as ■-V group semiconductors is used in the manufacturing process of light emitting devices such as semiconductor lasers and light receiving devices. In these applications, it is necessary to make the epitaxial growth layer high in resistance (10 6 Ω·cm or more) in order to improve the characteristics of the device.

However, the resistivity of a non-doped epitaxial phase to which nothing is added is as low as about several tens of Ω·cm, and cannot satisfy the required conditions.

Therefore, in the epitaxial growth of ■-V group compound semiconductors represented by InP and GaAs, resistance is increased by doping them with iron.

Conventionally common iron doping methods include, for example, J. Appl. Phys., 61 (1,987).
There are methods, such as those disclosed in US Pat. No. 4,698, by reacting iron wire or iron powder with H2-based HCl gas to produce iron chloride, which is then delivered onto the substrate to dope it with iron.

However, such a method has the disadvantage that impurities in the iron wire or iron powder, mainly sulfur, are simultaneously doped into the epitaxial layer, and as a result, high resistance cannot be obtained.

As a method to solve such problems, Japanese Patent Application Laid-Open No. 62-2
In Publication No. 35300, an organic compound gas containing an iron element such as ferrocene is transported and supplied simultaneously with a halide gas such as HCQ, and iron is converted into a compound semiconductor by iron chloride generated by the reaction of these gases during transportation. Methods of doping have been developed. Compared to iron wire and iron powder,
Since impurities that impair the purity of the epitaxial layer are hardly present in such an organic compound, a high-resistance epitaxial phase can be obtained by such a method.

[Problems to be Solved by the Invention] However, according to such a method, since two types of gases, organic compound gas and HCi gas, are flowed simultaneously, the amount of unreacted HC gas fluctuates significantly. Cheap. Unreacted Hi gas etches the epitaxial layer of, for example, InP, thereby adversely affecting crystal growth. Therefore, there is a problem in that the conventional method cannot stably avoid crystal growth. An object of the invention of this application is to provide a vapor phase epitaxial growth method that can improve the conventional drawbacks and grow stable and good crystals.

[Means for Solving the Problems] In the invention of claim 1, an organic compound containing iron element is thermally decomposed to precipitate and deposit iron, and then HC magazine gas is reacted with the iron to form iron chloride. This iron chloride is then supplied onto the substrate to dope the compound semiconductor with iron.

In the invention of claim 2, an organic compound containing iron element is thermally decomposed to precipitate and deposit iron, and then H (4 gas) is reacted with the iron in an inert gas as a carrier gas to form iron chloride. This iron chloride is mixed with H2 gas just before the substrate, and the compound semiconductor is doped with iron.

Examples of organic compounds containing iron used in these inventions include ferrocene (Fe(CsHs)
2) and iron pentacarbonyl (Fe(Co)s).

[Function] According to the invention of claim 1, first, a gas of an organic compound containing an iron element is supplied, and before the gas reaches the substrate, this gas is thermally decomposed to precipitate and deposit iron. In the case of ferrocene, it thermally decomposes at temperatures above 450°C and becomes iron and hydrocarbons. Next, HCi gas is supplied and reacts with the already deposited iron to generate FeCl2 gas. This FeC
The epitaxial layer of the compound semiconductor grown on the substrate is doped with iron by supplying l2 gas.

Iron obtained by thermally decomposing an organic compound containing the elemental iron contains significantly fewer impurities that impair the purity of the epitaxial layer than conventional iron powder or iron wire. For example, when ferrocene is used as the organic compound, the impurity concentration of the InP epitaxial layer is less than or equal to 5.times.10"cm.sup.-". Therefore, the epitaxial layer can have higher resistance than when iron powder or the like is used.

Moreover, unlike the method disclosed in JP-A No. 62-235300 mentioned above, since the two gases of organic compound gas and H (4) are not flowed simultaneously, the amount of unreacted HCQ gas fluctuates. Therefore, crystals can be grown stably.

The invention of claim 2 is a further improvement of the invention of claim 1, in which an inert gas is used as a carrier gas, and iron chloride obtained by reacting in the inert gas is heated with H2 gas immediately before the substrate. It is characterized by being mixed with. The reaction between iron and HCl gas progresses according to the thermodynamic equilibrium shown in the following equation.

Fe(s)+211Cl(g)# PeCf1
2 (g) 102 (g) According to this reaction, F
121 moles of FeCff and 21 moles of N are generated from 1 mole of e and 2 moles of HCi. When a large amount of N2 gas is present in the system, a decomposition reaction proceeds in the opposite direction, and the produced iron chloride is reduced to iron. Therefore, in order to increase the amount of iron chloride produced, it is necessary to remove N2 gas in advance. In this invention, as a carrier gas,
By using an inert gas other than N2, supplying HCIL gas, and causing iron and HCL gas to react in this inert gas, more iron chloride is produced. As a result, it becomes possible to sufficiently supply iron chloride necessary for doping.

Figure 3 shows FeC when the carrier gas is N2 gas and when the carrier gas is N2 gas, which is an inert gas.
It is a figure showing the calculation result of the thermodynamic equilibrium of l2 production.

In FIG. 3, the solid line shows the case where H'2 gas is used as the carrier gas, and the dotted line shows the case where N2 gas is used as the carrier gas. As is clear from FIG. 3, if N2 gas is used as the carrier gas, 10 times more iron chloride can be produced than when N2 gas is used. In addition, since the amount of remaining HCi gas decreases, crystal growth is suppressed due to the presence of HCi gas,
Alternatively, etching of the substrate by HCQ gas is reduced, and iron-doped epitaxial growth becomes possible with good reproducibility.

Figure 4 is a diagram showing the relationship between the N2 gas concentration and the equilibrium partial pressure of FeC (12). It shows the amount of N2. added (CC) when
The lower scale shows the percent N2 gas. Further, the vertical axis indicates the partial pressure of FeclL2. Fourth
The figure shows the relationship between 650°C and 800°C. As is clear from FIG. 4, when even a small amount of N2 gas is mixed, the partial pressure of iron chloride decreases rapidly, and the equilibrium shifts in the direction of reduction of iron chloride. Therefore, as in the present invention, by avoiding mixing with N2 gas until immediately before the substrate and mixing immediately before the substrate, it is possible to dope iron into the Ebitashal layer with good reproducibility.

In FIGS. 3 and 4, N2 gas is used as the inert gas, and the concentrations of all four H gases are 5 mol%.

When the H(4 gas concentration is higher than this), a larger amount of FecQ2 is generated, and a more significant effect is observed.

[Embodiment] FIG. 1 is a schematic sectional view showing an apparatus for carrying out an embodiment of the invention according to claim 1. In this method, N2 gas is used as a carrier gas. In FIG. 1, a source port 6 containing In and a wafer 7 are provided in a reaction tube 2. An introduction tube 5 for introducing N2, PCQ, and s gases is installed in the reaction tube 2, and the tip of the introduction tube 5 is located above the source port 6. Further, a dopant supply pipe 8 is attached to the reaction tube 2, and the tip of the dopant supply pipe 8 is
It is located at the center of the reaction tube 2. A ferrocene gas supply pipe 4 for supplying ferrocene gas and an MCI supply pipe 3 for supplying N2 and HCII gas are connected to the other end of the dopant supply pipe 8.

A heater 1 for heating the inside of the reaction tube 2 is provided around the reaction tube 2 .

The inner diameter of the reaction tube 2 is 100 mm. N2 in the introduction pipe 5
The gas flow rate was 1000c/min, and the PCQ at 1℃
, a is introduced by bubbling P(4).In the HCl supply pipe 3, N2-based gas containing 10% HCI)-gas is supplied at 1 to 3 cc/min, and the 200-400cc/N2 gas is supplied. The ferrocene gas supply pipe 4 has 25 to 5
By passing over solid ferrocene at 0°C, N2 gas containing ferrocene gas is heated to 100 to 300 c c
/min is swept away. Note that the inner diameters of the HCQ supply pipe 3, ferrocene gas supply pipe 4, and introduction pipe 5 are all 5 mm.
It is. In addition, an In source is placed in the source port 6, and its surface is covered with an InP crust (thick film).
covered with.

First, before starting crystal growth, the ferrocene gas supply pipe 4
Then, N2 gas containing ferrocene gas was added as described above.
Flow at 00-300cc/min.

At this time, the heater 1 heats the inside of the dopant supply pipe 8 near the heater 1 population to 450° C. or higher, thermally decomposes the sent ferrocene gas, and deposits iron in the dopant supply pipe 8. Thereafter, the supply of ferrocene gas is stopped, and HCI gas is passed from the HC supply pipe 3 into the dopant supply pipe 8 under the above-mentioned conditions. The sent HCl gas reacts with the iron deposited in the dopant supply pipe 8 to generate iron chloride, and this iron chloride is carried onto the wafer 7 .

During this crystal growth, the temperature of the In source in the source port 6 is set at 720-800°C, and the wafer 7 is
The temperature is set at 0 to 680°C. P supplied from the introduction pipe 5
Due to the reaction between CI and In in the source port 6, InP is grown in a vapor phase on the wafer 7. At this time, iron chloride gas is supplied and the InP is doped with iron.

Under the above conditions, an iron-doped InP epitaxial layer having a high resistance of 10 6 Ω·cm or more can be grown.

FIG. 2 is a schematic cross-sectional view of an apparatus used to carry out an embodiment of claim 2. In this example, N2 gas is used as the carrier gas. In FIG. 2, in the reaction tube 12, a source port 16 containing In metal 17 is set at 750 to 850°C.
The substrate 18 is maintained at 600-650°C. Further, a dopant introducing tube 19 is installed in the reaction tube 12, and its tip is provided at a position 10 mm before and 10 mm above the tip of the substrate 18. A ferrocene gas introduction pipe 14 and an MCI gas introduction pipe 13 are connected to the introduction side of the dopant supply pipe 19 . Heaters 11a, 11b, and 11c are provided around the reaction tube 12. The heater 11c is a heater for thermally decomposing ferrocene to precipitate iron, and is always maintained at 600°C.

The inner diameter of the reaction tube 12 is 100 mm. N2 gas made by bubbling liquid PCl3 maintained at 1° C. is introduced into the introduction pipe 15 at a flow rate of 100 cc/min.

The Hll gas introduction pipe 13 has a
HCl gas of mol % is supplied at 20 to 30 cc/min. From the ferrocene gas introduction pipe 14, 25 to 5
By passing through solid ferrocene maintained at 0°C, N2 gas containing ferrocene gas is
It is supplied at a flow rate of cc/min. In addition, from the H2 introduction pipe 21, N2 gas is supplied as a dilution gas at 200~
It is supplied into the reaction tube 12 at a flow rate of 400 cc/min. All introduction tubes have an internal diameter of 5 mm.

In addition, the surface of the In metal 7 has an InP crust (coating).
covered with.

First, before starting crystal growth, N2 gas containing ferrocene gas is supplied at 100 to 300 cc/mi as described above.
The transported ferrocene gas is thermally decomposed by the heat of the thermal decomposition heater 11c, and iron is precipitated and deposited on the inner wall of the dopant introduction pipe 19. Next, the ferrocene gas is stopped and only N2 gas is used, and HCI gas based on N2 gas is flowed into the dopant introduction pipe 19 from the HCl gas introduction pipe 131 at a flow rate of 20 to 30 cc/min. The introduced HCi gas reacts with the deposited iron,
Iron chloride is produced, and this iron chloride is conveyed through the dopant introduction pipe 19 to just in front of the substrate 18.

By thermal decomposition of PCQs supplied by the inlet pipe 5,
It becomes HCl and P4, reacts with In metal 7, and grows InP on substrate 8. At this time, dopant introducing pipe 1
The iron chloride supplied by 9 is mixed with the N2 gas supplied into the reaction tube 2 by the H2 introduction pipe 21, and the InP is doped with iron.

As described above, high-resistance InP epitaxial growth can be realized with good reproducibility, and the resistivity can be made higher by about one order of magnitude or more than in the case of the embodiment described in FIG. Furthermore, the growth rate can be made more stable.

In addition, in this invention, the inert gas contains 4 N2 gas.
They may be mixed as long as the amount is 0% or less.

This is because, as is clear from FIG. 4, the effects of the present invention can be exhibited if the N2 gas concentration is 40% or less.

In addition, even in doping using iron powder or iron wire, if an inert gas is used as the carrier gas, N
The amount of iron chloride produced can be higher than when using a carrier gas based on two gases.

In each of the embodiments of claims 1 and 2, the chloride vapor phase epitaxial growth method of InP has been described as an example, but these inventions can also be applied to the hydride method.

Also, using a halide gas, for example, GaAs.

It can also be applied to the formation of high-resistance epitaxial layers of ■-v group compound semiconductors such as InGaAsP, InGaAs, InGaP, and GaP.

Further, in the embodiment of claim 2, N2 gas is used as the inert gas, but instead of this gas, for example, argon,
Inert gases such as helium can also be used.

[Effects of the Invention] As explained above, in the inventions of claims 1 and 2, an organic compound containing an iron element is thermally decomposed, iron is precipitated and deposited, and then this iron and HC are separated. Since it is doped with iron chloride produced by reacting HCi, fluctuations in unreacted HCi gas, which were a problem in conventional methods, can be reduced.

Therefore, better crystals can be grown more stably than conventional methods. In addition, since iron produced by thermal decomposition of an organic compound is used, there are few impurities that adversely affect the increase in resistance of the epitaxial layer, and a high-resistance epitaxial layer can be obtained even with a small amount of iron doping.

Furthermore, in the invention of claim 2, since an inert gas is used as the carrier gas, the amount of unreacted HC gas can be reduced, thereby preventing damage caused by etching of the substrate due to H (4 gas). It can be prevented.

In addition, since an inert gas is used as a carrier gas and N2 gas and iron chloride are mixed just before the substrate, the amount of iron chloride produced can be increased and iron can be doped stably with good reproducibility. A compound semiconductor can be obtained.

As described above, the epitaxial layer obtained by the invention of claims 1 and 2 has excellent characteristics, so
It can be used for many purposes, such as a current confinement layer of an InP-based semiconductor laser used in optical communications, an In, P-based light-receiving element, and an inter-element isolation insulating layer of an optoelectronic integrated circuit.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view showing an apparatus used to carry out an embodiment of the invention as claimed in claim 1. FIG. 2 is a schematic cross-sectional view showing an apparatus used for carrying out an embodiment of the invention according to claim 2. FIG. 3 is a diagram showing the thermodynamic equilibrium of FeCfL2 production when N2 gas is used as the carrier gas and when N2 gas is used as the carrier gas. FIG. 4 is a diagram showing the relationship between the N2 gas concentration and the equilibrium partial pressure of FeCrL2. In the figure, 1 is a heater, 2 is a reaction tube, 3 is an HCl supply tube, 4 is a ferrocene gas supply tube, 5 is an introduction tube, 6 is a source boat, 7 is a wafer, 8 is a dopant supply tube, lla
, llb is a heater, llc is a pyrolysis heater, 12 is a reaction tube, 13 is an HCfl gas introduction tube, 14 is a ferrocene gas introduction tube, 15 is an introduction tube, 16 is a source port, 7 is an In metal, 18 is a substrate , 19 is a dopant introduction pipe, 21
indicates the H2 introduction tube. Figure 3 Figure 4 Necaro H, (CC) Miwaka H, ('',)

Claims (2)

[Claims] (1) React HCl gas with iron to generate iron chloride,
In a vapor phase epitaxial growth method in which a compound semiconductor is doped with iron by supplying the iron chloride, an organic compound containing the iron element is thermally decomposed to precipitate and deposit iron, and then HCl gas is reacted with the iron. A vapor phase epitaxial growth method comprising: converting the iron chloride into the iron chloride, and doping the iron chloride with iron. (2) A vapor phase epitaxial growth method in which a compound semiconductor on a substrate is doped with iron by reacting iron with HCl gas in a carrier gas to generate iron chloride, and supplying the iron chloride mixed with H_2 gas. After thermally decomposing an organic compound containing the iron element to precipitate and deposit iron, HCl gas is reacted with the iron in the inert gas as the carrier gas to form the iron chloride. A vapor phase epitaxial growth method in which a compound semiconductor is doped with iron by mixing it with H_2 gas just before the substrate.