JPH03220717A - Crystal growth apparatus - Google Patents

Abstract

PURPOSE:To obtain a superlattice structure having a predetermined distortion amount with high reproducibility by integrating an X-ray diffraction unit with a crystal growing unit, and feeding back diffraction information of grown crystal from the distortion amount to a mixed crystal composition and from the mixed composition to a reaction gas flow rate. CONSTITUTION:An X-ray diffraction device having an X-ray source 2, an X-ray transmission window 3, a diffraction wave transmission window 4, a counter 5, and a gyro mechanism 6 is associated with an organic metal thermal decomposition reactor 1, predetermined reaction gas is fed to form a semiconductor crystalline layer 7, and the diffraction angle of the layer is measured. The diffraction angle information is converted from the distortion amount to the mixed crystal composition, further from the mixed composition to the reaction gas flow rate by a CPU controller 8, and then fed back to a gas controller 9. Thus, a superlattice structure having desired distortion can be formed accurately with high reproducibility.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a crystal growth apparatus for high-performance compound semiconductor optical devices and electric devices, and particularly relates to crystal growth devices for strained superlattice III-V groups, II
The present invention relates to a crystal growth apparatus for -VI group compound semiconductors and their mixed crystal semiconductors, and more specifically to a crystal growth apparatus that uses organometallic compounds or hydrogen compounds containing the respective delivered constituent elements as crystal growth raw materials.

[Conventional technology]

(2) Conventional amount of strain As an application example of a compound semiconductor, a semiconductor laser with an InGaAs strained superlattice active layer was prototyped using MBE (molecular beam epitaxy), as described in the International Conference on Integrated Optics and Optical Communications], pp. 8B2-68 (1989) (Inter
National Conference onInt.
egrated 0ptics and 0ptica
l Communj, cations18B2-6 P
-8 (1,989).

[Problem to be solved by the invention]

The delivery growth method of a strained superlattice according to the above-mentioned prior art does not have a feedback mechanism for the amount of strain, and therefore cannot be accurately controlled.

An object of the present invention is to obtain a target strained superlattice structure in the growth of a strained compound semiconductor by accurate measurement of the strain and rapid feedback of the amount of deviation from the set pattern. Furthermore, it is an object of the present invention to provide a new and highly productive crystal growth apparatus for compound semiconductors and the like by making the in-plane distribution of strain on a growing wafer uniform.

(3) (Means for solving ill 1 problem) In order to achieve the above object, in the crystal growth apparatus of the present invention, for example, as shown in the No. Source 2, X-ray transmission window 3, diffracted wave transmission window 4
, a counter 5, and a gyro mechanism 6, and a means for measuring the angle of diffraction of the semiconductor delivery layer 7 formed by flowing a predetermined reaction gas is provided. Further, this diffraction angle information is converted by the CPU control system 8 from the strain amount to the mixed crystal composition and from the mixed crystal composition to the reaction gas flow rate, and then fed back to the gas control system 9. Further, the distribution of the amount of strain in the semiconductor crystal layer 7 within the wafer plane is made uniform by a gas flow control plate 10 provided in the reactor 1. In addition, a part of the gas flow control plate 1.0 is
By using feed with sufficiently high X-ray transmittance, the diffraction angle can be easily measured. For example, if beryllium is used, an X-ray transmittance of 90% or more can be ensured. by the way,
Beryllium X-ray transparent window 11 placed above the board delivery
Because it is exposed to reactive gases during delivery growth.

(4) Reaction products gradually accumulate, resulting in a gradual decrease in X-ray transmittance. This phenomenon can be solved by replacing the beryllium (integrated with the beryllium holder) with a new beryllium holder together with the substrate wafer every time the same crystal grows using the transport mechanism.

[Effect]

By integrating the X-ray diffraction system and the crystal growth device, the diffraction information of the growing crystal can be fed back from the strain amount to the mixed crystal composition and from the mixed crystal composition to the reaction gas flow rate in a short time.
A superlattice structure with a predetermined amount of strain can be realized with good reproducibility1. In addition, since beryllium, which also serves as the gas flow control plate and has good X-ray transmittance, is used, the intensity attenuation of the incident X-ray wave and the refraction wave is small, and accurate information on the refraction angle can be easily obtained, as well as distortion. Since the distribution of the amount within the wafer surface is also uniform, crystal growth with excellent reproducibility and mass productivity can be achieved.

〔Example〕

An embodiment of the present invention will be described below in more detail with reference to the drawings.

(Example Work) (5) InP/I was deposited on a 50 mmφ InP substrate as a phase material.
The case of creating a strained superlattice structure of nGaAs will be explained using FIGS. 1 and 2 as an example.

FIG. 1 shows the structure of a crystal growth apparatus according to an embodiment of the present invention. The second figure shows the detailed structure of the crystal growth apparatus according to one embodiment of the present invention, especially around the substrate holder.

After pre-etching the n-type InP (100) substrate 7, it is fixed to a predetermined device in the reactor 1 by means of a transport system 2, as shown in FIG. At this time, the jig for setting the substrate wafer 7 doubles as a gas control board, and two silk beryllium X-ray transmitting windows 1 are arranged so that the second jig and the wafer holder are shown on three sides. It is a structure in which King 3 is integrated. The substrate heating holder 14 is heated by a high frequency induction heating method, a resistance heating method, etc., and the wafer holder 13 is arranged above the substrate holder 4. Further, the substrate holder 14 can also be made to be able to rotate in the same direction by an external driving force.

(6) Next, the reaction system was sufficiently replaced with hydrogen gas under a reduced pressure of 76 Torr. After that, the substrate holder 14 is heated to 600°C using a resistance heating method.
was held at After about 5 minutes, trimethylindium, which is a raw material for In (indium), and phosphine, which is a raw material for P (phosphorous), were transported for 20 minutes to grow a 0.5 μm InP (indium phosphide) buffer layer. Next, trimethylindium, which is a raw material for In (indium), phosphine, which is a raw material for P (phosphorus), and triethyl gallium, a raw material for Ga (gallium), are mixed so that the amount of crystal lattice mismatch with the substrate InP is +2.0%. Each gas flow rate was adjusted and transported for about 25 seconds, and 0.01 am In
A GaAs strained layer (quantum well layer) was grown. In this state, the X-axis, Y-axis, tilt, etc. (using the gyro mechanism 6) are finely adjusted using the X-ray diffractometer, and In Ga A
As a result of measuring the diffraction angle of the s-strained layer and calculating the amount of strain using the CPU control system 8, the amount of strain in the grown layer was +1.8%.

This amount of distortion is -0.2% compared to the design value of +2.0%.
% difference (7) This information was immediately converted into the mixed crystal composition of the crystal by the CPU control system 8, and further converted into the reaction gas flow rate from the mixed crystal composition, and the data was temporarily saved. During this time, the next InP layer (barrier layer) was grown to a thickness of about 0.01 μm in the reactor 1. Next I
An nGaAs quantum well layer was grown, and at this point, the flow rate of the reaction gas was already adjusted so that the amount of strain was +2.0%.

After repeating this operation 10 times, the InP layer was finally deposited at about 0.
It grew by 5 μm. Through the process described above, the distortion amount of the crystal has an error of less than ±0.1%, which is lower than the conventional error of ±0.2 to 0.
It was possible to obtain a much more accurate distortion amount compared to 4%. When this crystal was suspended from reactor l and subjected to a semiconductor process, carriers were injected into the crystal. Compared to a normal superlattice or bulk, the carrier energy distribution changed significantly (band filling effect), and the refractive index changed significantly. The refractive index change was 4% in the element of the present invention, compared to 2% in the bulk. This is a major feature of strained superlattices.

(Embodiment 2) (8) The third example is an explanatory diagram when the present invention is applied to a semiconductor laser diode.

By the same operation as in Example 1, n was formed on the nGaAs substrate 31.
-A I G a As Clarad layer 32, film thickness 50
A strained superlattice layer consisting of a 5-periodic structure of 1 n, a, Gao, 5A s well 133 and a 100A thick GaA 5n-aPna7 barrier layer 34, p-A I Ga
As cladding layer 35, n-Ga As layer 36
are sequentially grown using the crystal growth apparatus of the present invention, a current passing region 38 is formed by the Zn diffusion region 37, and a p-electrode 39.
An n-electrode 40 was formed.

When the characteristics of this laser were measured, reflecting the effect of the strained superlattice structure, the threshold current was approximately 1 mA, and the resonance frequency was 30 GHz with an optical output of 5 mW, several times higher than conventional values.

(Embodiment 3) FIG. 4 is an explanatory diagram when the present invention is applied to a semiconductor optical phase modulator.

By the same operation as in Example 1, n was deposited on the n-InP substrate 51.
-InP rosette layer 52, In film thickness 70A (9). , *G ao+7. As well layer 53 and film thickness 7
a strained superlattice layer consisting of seven periods of 0A InP barrier layer 54;
p-InP cladding layer 55, p-InP cladding layer 55, p-InP cladding layer 55, p-InP cladding layer 55
The sP charap layer 56 is sequentially grown using the crystal growth apparatus of the present invention. At this time, the amount of strain in the well layer was 1.9%.

Next, using a photoresist mask, the cap layer 56 and the cladding layer 55 are selectively etched using a mixed solution of hydrochloric acid and nitric acid until the strained superlattice layer is reached, thereby forming a ridge structure as shown in FIG. . After this, SiO, crotch 5
7 is formed by the CVD method, and after forming a contact hole, a Zn diffusion region 58 is formed. Next, the n-type electrode 5
9 and the p-type electrode 60 were formed, the length in the optical axis direction was set to 1 mm by the crystal arm opening method, and both crystal opening surfaces were coated with anti-reflection coating. Wavelength 1.55 from one end face of this optical modulator
The propagation loss when a μm laser beam is incident is 20 d
A phase control of 2π was obtained with B/cm and an injection current of 30 mA.

In this example, I n P and Ga A are used as substrates.
s, strain (10) InGaAsI as a combination of well layer and barrier layer of superlattice
Although nP and InGaAs-GaAsP layers have been described as representative, these substrates are not limited to the combination of strained superlattice well layers and barrier layers, Sj and II-VI group substrates may be used, quantum wells, etc. and I n Ga As as a barrier layer.
P, I n A s P, A], Ga
As.

GaInAsSb, InGaAIA,s,
It goes without saying that any introduction to InGaAIP is acceptable.

Further, other molecular beam epitaxy equipment or the like may be used as a means for delivery growth.

〔Effect of the invention〕

As explained in detail above, according to the present invention, a superlattice structure with a desired strain can be formed with high precision and high reproducibility, so it can be used for various new optical devices and devices that could not be produced using conventional crystal growth equipment. Electrical elements can be designed.

[Brief explanation of drawings]

Fig. 2 is a schematic diagram showing the overall configuration of the crystal growth apparatus of the present invention, and Fig. 2 is a schematic diagram showing the suitable structure of the beryllium X-ray transparent (11) which also serves as a wafer holder in the crystal growth apparatus of the present invention. , FIG. 3, and FIG. 4 are cross-sectional views of an example of a strained superlattice structure applied element formed by the crystal growth apparatus of the present invention. Engineering: reactor, 2: X-ray source, 3: X-ray transmission window, 4: diffracted wave transmission window, 5: counter, 6.
... Gyro mechanism, 7... Semiconductor crystal layer, 8...C
PU control system, 9...Gas control system, lO...Gas flow control panel, Engineering 1...Beryllium X-ray transmission window, ↓3...Wafer holder 14...Substrate holder, 31... n
-G a As substrate, 32- n -A ] G
a As Clarado layer, 33...I n G a
A, s-well layer, 34-GaAsP barrier layer,
35- A I G a As Clarado Layer, 36-
n-GaAs layer, 51- n-I n P substrate, 5
2- n -I n P rosette layer, 53...I n
G a A, s well layer, 54...InP disorder layer,
55...p-InP cladding layer, (12)th? Figure diagram

Claims (1)

[Scope of Claims] 1. A semiconductor crystal growth apparatus for growing a semiconductor epitaxial layer on a semiconductor substrate, characterized by having a function of measuring the strain amount of the epitaxial debris during the formation of the epitaxial layer. Device. 2. In the crystal growth apparatus according to claim 1, the growth apparatus is provided with at least two X-ray transmission windows and a diffraction wave transmission window, and has means for measuring the amount of strain by an X-ray diffraction method. A crystal growth device that is characterized by: 3. The crystal growth apparatus according to claim 2, wherein the material of the X-ray transmission window and the diffraction wave transmission window is Be (beryllium). 4. In the crystal growth apparatus according to claim 1, 2, or 3, Be (beryllium) for X-ray transmission is arranged in at least two locations of the wafer holder on which the semiconductor substrate is mounted. A crystal growth device that is characterized by: 5. The crystal growth apparatus according to claim 4, characterized in that the wafer holder integrated with the Be (beryllium) X-ray transmission window can be taken out of the growth apparatus by a transport mechanism. 6. A crystal growth apparatus according to claim 4 or 5, characterized in that the existing holder also serves as a gas flow control plate.