JPH08172053A - Crystal growth method - Google Patents

Abstract

PURPOSE: To grow a III-V compound semiconductor crystal such as AlGaAs selectively by alternately supplying the upper section of a III-V compound semiconductor substrate selectively masked with an insulating film with a group III material and a group V material and choicely growing the III-V compound semiconductor crystal. CONSTITUTION: A GaAs substrate 23, in which a surface is covered with an insulating film mask 32, is arranged into a reaction chamber for a normal- pressure MOCVD device. A changeover valve is changed over selectively, and the inside of the reaction chamber is supplied alternately with the group III raw material of TWA+TMG and the group V raw material of AsH3 at a certain period. The group III raw material of TMA+TMG and the group V raw material of AsH3 are supplied continuously and alternately at no interval at that tome. Accordingly, no polycrystal deposits on the insulating film mask 32, and an AlGaAs layer 33 having extremely excellent grown surface morphology is grown choicely only on a GaAs surface, on which no insulating film mask 32 is shaped.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a crystal growth method for III-V group compound semiconductors, and in particular to AlGaAs on a GaAs substrate by using atmospheric pressure MOCVD (metal organic chemical vapor deposition) method.
The present invention relates to a crystal growth method that enables selective growth of crystals.

[0002]

_2. Description of the Related Art Conventionally, for example, G is formed on a GaAs substrate on which an insulating film mask made of SiN _x or SiO ₂ is selectively applied.
When the aAs crystal is selectively grown, the GaAs crystal can be grown with good selectivity even by the atmospheric pressure MOCVD method. However, when an AlGaAs crystal is grown on a GaAs substrate in the same manner, polycrystal growth also occurs on the insulating film mask and the selectivity deteriorates. This tendency becomes stronger as the Al mixed crystal ratio increases.

This point will be described in more detail with reference to FIG. FIG.
Shows a normal AlGaAs atmospheric pressure MOCVD apparatus. In the figure, 1 is an atmospheric pressure MOCVD apparatus as a whole, 2 is its reaction chamber, and AlGaAs is provided in the reaction chamber 2.
A substrate, for example, a GaAs substrate 3 on which crystals are to be grown is arranged. 4 is an AsH ₃ cylinder containing arsine (AsH ₃ ) which is a raw material of As, 5 is a TMA bath containing trimethylaluminum (TMA) which is a raw material of Al, and 6 is trimethylgallium (TMG) which is a raw material of Ga Stored TM
It is a G bathtub. Both TMA and TMG are bubbled with H ₂ gas and supplied to the reaction chamber 2. Reference numeral 7 is a pipe, and 8 is an exhaust pipe.

In this atmospheric pressure MOCVD apparatus 1, normally, as shown in FIG. 9, TMA and TMG group III source gases and A
Group V source gas of sH ₃ is simultaneously passed through the pipe 7 to the reaction chamber 2
Is supplied to the GaAs substrate 3 and thermally decomposed to form AlG on the GaAs substrate 3.
The aAs crystal is grown.

Using this crystal growth method, SiN _x and Si
GaAs substrate 3 selectively covered with an insulating film mask such as O ₂
When selective growth of AlGaAs is performed on top, a polycrystal grows on an insulating film mask and the selectivity deteriorates. The higher the mixed crystal ratio of Al, the greater the proportion of polycrystalline precipitation on the insulating film mask, and the worse the selectivity. In the case of GaAs growth, almost no polycrystal is deposited on the insulating film mask, and the selectivity is extremely good.

For this reason, conventionally, this selective growth of AlGaAs has been performed under reduced pressure MOCVD and normal pressure MOCV with addition of HCl gas.
It was done by D etc.

[0007]

However, the reduced pressure MOCV
Since D requires a decompression system, the apparatus configuration is complicated, and there are problems such as HCl gas-contaminated HCl gas contamination and pipe corrosion.

In view of the above points, the present invention is directed to a normal pressure MOCV.
D provides a crystal growth method that enables selective growth of a III-V group compound semiconductor crystal such as AlGaAs.

[0009]

The crystal growth method according to the first aspect of the present invention comprises alternating group III and group V materials on a group III-V compound semiconductor substrate selectively masked with an insulating film. And a group III-V compound semiconductor crystal is selectively grown.

A crystal growth method according to a second aspect of the present invention is characterized in that, in the first aspect, the group III material and the group V material are continuously and alternately supplied without a gap.

According to a third aspect of the present invention, in the crystal growth method according to the first or second aspect of the invention, the amount of the group III material supplied at one time is set to 9 times.
It is characterized in that the thickness is equal to or less than the atomic layer.

The crystal growth method according to the fourth aspect of the present invention is the first,
In the second or third invention, the III-V group compound semiconductor substrate is a GaAs substrate, and the III-V group compound semiconductor crystal is an AlGaAs crystal.

[0013]

In the first aspect of the present invention, the III-V group compound semiconductor substrate 23 selectively masked by the insulating film 32 is provided,
By alternately supplying Group III material and Group V material,
The insulating film 32 is not formed by the atmospheric pressure MOCVD method III −
The III-V compound semiconductor crystal 33 can be selectively grown only on the V compound semiconductor surface.

In the second aspect of the present invention, in the alternate supply of the first aspect of the present invention, the group III material and the group V material are continuously and alternately supplied without a gap, so that the insulating film 32 is formed on the insulating film 32. A III-V group compound semiconductor crystal 33 having no growth of polycrystal and good growth surface morphology is selectively grown.

In the third aspect of the present invention, the group III material in the first or second aspect of the present invention is supplied at a rate of 9 atomic layers or less, so that the selectivity III and the film quality III are further improved. The -V semiconductor crystal 33 can be selectively grown.

In the fourth aspect of the present invention, the III-V compound semiconductor substrate 32 of the first, second or third aspect of the invention is G
The III-V compound semiconductor crystal 33 is used as an AAs substrate.
By using lGaAs crystal, G can be obtained by atmospheric pressure MOCVD.
The AlGaAs crystal 33 can be selectively grown on the aAs substrate.

[0017]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an AlGaAs atmospheric pressure MOCVD apparatus according to the present invention. In the figure, 21 is a normal pressure MO
A CVD apparatus is shown as a whole, and 22 is a reaction chamber in which an AlGaAs crystal is grown and a substrate, for example, a GaAs substrate 23 is arranged. 24 is an AsH ₃ cylinder containing arsine (AsH ₃ ) which is a raw material of As,
25 is trimethyl aluminum (TM) which is a raw material of Al
A) is a TMA bath containing 26, and 26 is a TMG bath containing trimethylgallium (TMG) which is a raw material of Ga.
Both TMA and TMG are bubbled with H ₂ gas and supplied to the reaction chamber 22. Each AsH ₃ cylinder 24, TMA bath 25, and TMG bath 26 are connected to a first pipe 27 that communicates with the reaction chamber 22 and a second pipe 28 that communicates with an exhaust pipe 29 via a switching valve 30, respectively.

Using this atmospheric pressure MOCVD apparatus 21, Ga
The selective growth of the AlGaAs layer on the As substrate 23 is performed as follows. Here, the substrate shown in FIG. 5A, that is, the GaAs substrate 23 whose surface is selectively covered with an insulating film mask 32 made of SiN _x or SiO ₂ is used.

After arranging the GaAs substrate 23 in the reaction chamber 22 of the atmospheric pressure MOCVD apparatus 21, the switching valve 34 is selectively switched to the inside of the reaction chamber 22 as shown in FIG.
TMA + TMG group III source (ie source gas) and AsH
₃ of V group raw material (i.e., raw material gas) and alternately supplied in a cycle in the. That is, at this time, the TMA + TMG group III raw material and the AsH ₃ group V raw material are continuously and alternately supplied without a time interval. Furthermore, once (corresponding to the period of Ta)
The supply amount of the Group III raw material is set to 9 atomic layers or less.

As described above, the group III raw material and the group V raw material are continuously and alternately supplied with no interval, and thus, FIG.
As shown in FIG. 3, no polycrystal is deposited on the insulating film mask 32, and the growth surface morphology is extremely good only on the GaAs surface on which the insulating film mask 32 is not formed.
The As layer 33 is selectively grown.

AlGaAs by the conventional atmospheric pressure MOCVD method
The poor growth selectivity is due to the fact that Ga migrates sufficiently, whereas the migration length of Al is extremely short.
For this reason, it is considered that they are deposited on the insulating film mask 32. Therefore, in order to improve the selectivity of AlGaAs growth, Al adsorbed on the insulating film mask 32 is removed. According to the above-described embodiment, by alternately supplying the group III material and the group V material, the Al adsorbed on the insulating film mask 32 can be migrated and desorbed due to the lack of As. As a result, selective growth of AlGaAs is realized.

Further, the supply amount of the group III source gas also affects the polycrystalline deposition on the insulating film mask 32 and the growth surface morphology. If the supply amount of the group III raw material at the time of alternate supply exceeds the equivalent of 9 atomic layers, polycrystalline precipitation occurs and the growth surface morphology deteriorates. However, when the supply amount of the group III raw material once is equal to or less than the amount equivalent to 9 atomic layers, there is no influence of polycrystalline precipitation or deterioration of growth surface morphology, and good selective growth can be performed.

On the other hand, depending on the alternating supply of the group III material and the group V material, there are cases in which polycrystals are deposited on the insulating film mask 7 or the morphology of the growth surface is deteriorated. For example, as shown in FIG. 3, TMA, T
When a time interval Ta is provided between the supply of the group III source material of MG and the supply of the group V source material of AsH ₃ , no polycrystal precipitation is observed on the insulating film mask 32, but the growth surface morphology is extremely high. Deteriorate. It is considered that this is because the supply of arsine (AsH ₃ ) was small and As was released from the growth surface.

On the contrary, as shown in FIG. 4, when the group III source gas and the group V source gas are alternately supplied so as to partially overlap with each other, when the superposition time Tb is long, the method is different from the normal growth method. However, the growth surface morphology is improved and the polycrystalline precipitation on the insulating film mask 32 becomes severe. Therefore, the alternate supply as shown in FIG. 2 is the best.

In the above example, the trimethyl group material was used as an example of the group III raw material, but a triethyl group material may be used.

FIG. 6 shows the crystal growth method of this embodiment, that is, AlG.
The case where the aAs selective growth method is applied to the production of a real index guide laser is shown.

For comparison, a conventional method of manufacturing a real index guide laser will be described with reference to FIG. Conventionally, as shown in FIG. 7A, an n-type AlGaAs clad layer 42, an active layer 43, a p-type AlGaAs clad layer 44, and a guide layer 4 are formed on an n-type GaAs substrate 41.
5, p-type AlGaAs cladding layer 46 and p-type Ga
The As cap layer 47 is sequentially crystal-grown by a normal MOCVD method.

Next, as shown in FIG. 7B, the insulating film 48 formed in stripes on the uppermost p-type GaAs cap layer 47 is used as a mask to etch both sides up to the middle of the p-type AlGaAs cladding layer 44 in a mesa shape. Give. Next, FIG.
As shown in C, the insulating film 48 is removed and an n-type AlGaAs current block layer 49 having a high Al mixed crystal ratio is formed in order to form an index step in the lateral direction on the entire upper surface. The stripe ridge 50 is embedded in the block layer 49. Next, as shown in FIG. 7D, the n-type AlGaAs layer 49 on the p-type GaAs cap layer 47 is etched away to form a current path region. After that, the electrodes are formed to manufacture the target real index guide laser.

On the other hand, in this example, as shown in FIG. 6A, n-type AlGaA is formed on the n-type GaAs substrate 41.
The s clad layer 42, the active layer 43, the p-type AlGaAs clad layer 44, the guide layer 45, the p-type AlGaAs clad layer 46, and the p-type GaAs cap layer 47 are sequentially M.
Crystal growth is performed by the OCVD method.

Next, as shown in FIG. 6B, the insulating film 48 formed in stripes on the uppermost p-type GaAs cap layer 47 is used as a mask to etch both sides up to the middle of the p-type AlGaAs clad layer 44 in a mesa shape. Give. The steps up to this point are the same as the above-described conventional steps of FIGS. 7A and 7B.

Next, as shown in FIG. 6C, an n-type AlGaAs current block layer 49 having a high Al mixed crystal ratio is selectively grown using the crystal growth method of the present invention. At this time, n-type Al
The GaAs current blocking layer 49 is selectively grown so as not to be polycrystalline grown on the insulating film 48 but to be etched so as to fill the portion. After that, the electrodes are formed to manufacture the target real index guide laser. In this way, AlGa
Since the selective growth of the As layer 49 can be easily realized, the manufacturing process can be simplified.

[0033]

According to the present invention, by alternately supplying a group III material and a group V material, it is possible to perform III-type atmospheric pressure MOCVD.
The group V compound semiconductor crystal can be selectively grown.

By continuously and alternately supplying the group III material and the group V material with no interval, a group III-V compound semiconductor crystal having excellent selectivity and good film quality can be selectively grown. .

Further, by setting the supply amount of the group III material to be equal to or less than the amount equivalent to 9 atomic layers, it is possible to grow a group III-V compound semiconductor crystal with good selectivity and good film quality.

In this way, the atmospheric pressure M, which has been difficult in the past, is obtained.
It is possible to selectively grow an AlGaAs crystal having good selectivity and good film quality on the GaAs substrate by the OCVD method.

[Brief description of drawings]

FIG. 1 is an atmospheric pressure MOCV used in a crystal growth method according to the present invention.
It is a block diagram of a D device.

FIG. 2 is an explanatory view showing an example of a method of supplying a group III raw material and a group V raw material in the crystal growth method according to the present invention.

FIG. 3 is an explanatory view showing another example of a method of supplying a group III raw material and a group V raw material of the crystal growth method according to the present invention.

FIG. 4 is an explanatory view showing another example of the method of supplying the group III raw material and the group V raw material of the crystal growth method according to the present invention.

FIG. 5 is a process drawing for selectively growing AlGaAs on an A GaAs substrate. It is a process drawing of selectively growing AlGaAs on a B GaAs substrate.

FIG. 6A is a process drawing showing the manufacturing method of a real index guide laser using the crystal growth method of the present invention. B is a process drawing showing a method for producing a real index guide laser using the crystal growth method of the present invention. FIG. C is a process drawing showing a method for producing a real index guide laser using the crystal growth method of the present invention. FIG.

FIG. 7A is a process drawing showing a method of manufacturing a conventional real index guide laser. B is a process diagram showing a method for manufacturing a conventional real index guide laser. C is a process diagram showing a method for manufacturing a conventional real index guide laser. D is a process diagram showing a method of manufacturing a conventional real index guide laser.

FIG. 8 is a block diagram showing a conventional atmospheric pressure MOCVD apparatus.

FIG. 9 is an explanatory diagram showing a method of supplying a group III raw material and a group V raw material in a conventional crystal growth method.

[Explanation of symbols]

1,21 Normal pressure MOCVD apparatus 2,22 Reaction chamber 3,23 Substrate 4,24 AsH ₃ cylinder 5,25 TMA bath 6,26 TMG bath 7,27,28 Piping 8,29 Exhaust pipe 30 Switching valve

Claims (4)

[Claims] 1. III-V selectively masked with an insulating film
A crystal growth method characterized in that a group III material and a group V material are alternately supplied onto a group compound semiconductor substrate to selectively grow a group III-V compound semiconductor crystal. 2. The crystal growth method according to claim 1, wherein the group III material and the group V material are continuously and alternately supplied without a gap. 3. The crystal growth method according to claim 1, wherein a single supply amount of the group III material is equal to or less than 9 atomic layers. 4. The III-V compound semiconductor substrate is Ga
The As substrate is used, and the III-V compound semiconductor crystal is Al.
The crystal growth method according to claim 1, wherein the crystal growth method is a GaAs crystal.