JPS61198789A - Continuous manufacture of optical semiconductor element - Google Patents

Abstract

PURPOSE:To improve productivity, by combining a liquid-phase growing method and a vapor-phase growing method into a series system, applying the liquid- phase method in forming a thick epitaxial layer, and applying the vapor-phase method in forming a thin epitaxial layer requesting accuracy. CONSTITUTION:On a GaAs substrate 2, a P1 layer 3 having a thickness of about 100mum is formed. In this case, a vapor-pressure controlled, temperature- difference, continuous liquid-phase growing method 11, whose growing speed is quick, is applied. In order to remove the remaining melt 7 after the liquid- phase growth, the surface of the P1 layer is treated by surface-vapor phase cleaning (including etching) 12. A P2 layer (thickness of about 1mum) 4 is epitaxially grown 8 by a vapor-phase growing method 13 on the surface of the P1 layer. The wafer is transferred to a liquid-phase growing chamber, and an N layer 5 having a thickness of about 50mum is epitaxially grown 9 by the liquid phase method. Thus the productivity is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [5] The present invention relates to a continuous manufacturing method for optical semiconductor devices.

Ori J (10 digits Conventionally, when manufacturing optical semiconductor devices, a double hetero layer is formed by forming P, 22, and N layers of different thickness on a GaAs substrate by epitaxial growth as shown in Figure 2. (DH) structure wafer 1 was prepared, and GaAs was etched from the acid wafer 1 by etching as shown in FIG.
After removing the substrate (which serves as an absorption layer for the generated light), Au electrodes are formed on both surfaces to manufacture the chip 2 with the DH structure. However, when creating multiple layers with different thicknesses, the time required for each layer to grow is significantly different, so it is not possible to simply set the time the slider spends in each melt tank constant and move the slider continuously. Epitaxial growth cannot be performed. That is, epitaxial growth cannot be performed continuously in time series.

Therefore, as a method for continuously manufacturing optical semiconductor devices, the confinement layer (22 layers) of the DH wafer 1 must be formed using a method with low productivity as shown in FIG. That is, in this method, a slider 3 consisting of a continuous repeating combination of a connecting slider, a slider supporting a dummy board, and a slider supporting a DH plate is attached to each melt layer 4.
5.6.7 is moved intermittently, but since the melt tank 6 is in a supersaturated state for 90 minutes, the G
When the aAs substrate comes under the melt bath 6, the rate of epitaxial growth is too fast, making it difficult to control the thickness of the 22 layers to lμ. Therefore, in order to avoid this phenomenon, a 90mm
When the growth rate slows down after 5 minutes of epitaxial growth, it is necessary to position it under the DH plate melt tank 6, and therefore the connecting slider and the dummy substrate bone are both ineffective.

Further, in the production of semiconductor devices, either the vapor phase method or the liquid phase method is normally used, particularly when performing epitaxial growth on a crystal substrate. When epitaxial growth is performed using the vapor phase growth method, in order to obtain a more complete and high quality crystal, the growth rate must be reduced to 1 atomic layer (2 to 2 ~
In some cases, it is extremely slow (4 people/5ec). In addition, in the ordinary MOCVD (organometallic CVD) method, it is on the order of 5 to 30 people/5ec). Therefore, the vapor phase growth method has a one- to two-fold growth rate that is slower than that of the liquid crystal growth method, and this fact becomes an extremely important problem when manufacturing semiconductor devices. That is, the vapor phase growth method can be said to be a method that has both the advantage of forming a high-quality epitaxial film and the disadvantage of requiring a long epitaxial growth time.

On the other hand, the liquid phase growth method is characterized in that its crystallinity is relatively good even when the growth rate is increased. but,
In the case of liquid phase growth, it is nearly impossible to regularly control epitaxial growth of one atomic layer or one molecular layer. Therefore, it can be said that it is inferior to the gas phase method in this respect.

The present invention addresses the steam problem and provides an optical semiconductor device that enables continuous epitaxial growth in chronological order even if the thickness of multiple epitaxial layers differs, thereby improving productivity. The purpose is to provide a continuous manufacturing method.

The continuous manufacturing method of optical semiconductor devices according to the present invention combines a vapor pressure controlled temperature difference method continuous liquid phase growth method (hereinafter referred to as liquid phase method) and a vapor phase growth method in a series of systems to continuously manufacture a GaAs substrate. When transferred, the liquid phase method is applied to form a thick epitaxial layer, and the vapor phase method is applied to form a thin epitaxial layer that requires precision, and the GaAs substrate remains in each growth chamber. This is to keep the time constant.

Hereinafter, the present invention will be described in detail based on an embodiment shown in FIG. 1. FIG. 1 shows a method for making a wafer as shown in FIG. This is a P1 layer epitaxial growth process in which 21 layers are epitaxially grown to about 10'Oμ on a GaAs substrate by a liquid phase method in a phase growth chamber, and this thickness is such that the defects in the GaAs substrate crystal are covered with 29 layers and the thickness is as shown in FIG. When the GaAs substrate serving as the light absorption layer is removed to obtain the chip structure shown, the thickness is the minimum that allows handling of the wafer and chip. In order to form these 21 layers with a thickness of about 100 μm, a liquid phase method is adopted because it is advisable to use a method with a high growth rate. Step 12 is to transfer the wafer on which the 21st layer has been formed to a chamber that is isolated with a gate pulp or the like and capable of continuous transfer, and removes a small amount of melt residue after liquid phase growth that is present on the surface of the P7 layer in an inert gas or high vacuum. This is a surface vapor phase cleaning step for removing the P1 layer, and it is also possible to etch the surface of the P1 layer in a vapor phase. 13 is a 22-layer epitaxial growth step in which the wafer, which has undergone the above-mentioned processing, is transferred to a vapor phase growth chamber and a 22-layer is epitaxially grown on the surface of the 21-layer; the thickness and crystallinity of this layer are determined when the device is formed. The required thickness is approximately 1 μm. For the formation of these 92 layers, MOCVD method, M,
Vapor phase growth methods such as BE (molecular beam epitaxial) method and photoexcited molecular layer epitaxial method are used. In step 14, after forming 22 layers, the wafer is transferred to a liquid phase growth chamber, a light extraction part and a surface electrode are formed, and an N layer with a thickness of approximately 50 μm is epitaxially grown using a liquid phase method, taking into account the strain during bonding. This is an N-layer epitaxial process. Each of the above steps is performed continuously.

Note that this example is structured as a system of liquid phase growth method, vapor phase growth method, and liquid phase growth method, but liquid phase growth method - vapor phase growth method -
A system of vapor phase growth and liquid phase growth is also included in the present invention.

As mentioned above, according to the continuous manufacturing method of optical semiconductor devices according to the present invention, when a GaAs substrate is continuously transferred, a liquid phase method is applied to form a thick epitaxial layer, and a thin and highly accurate layer is formed. Since a vapor phase method is applied to form the required epitaxial layer, the time that the GaAs substrate stays in each growth chamber can be made constant. Therefore, continuous epitaxial growth can be performed in a time-series manner, and there are no ineffective parts, so that productivity is improved. Furthermore, although the crystals that serve as substrates for the ■-v group are still not perfect, defects can be reduced by growing them thickly by liquid phase epitaxial growth on such imperfect substrates. Furthermore, it is possible to ensure a sufficient thickness for handling even after the substrate is removed. Furthermore, since the confinement layer (22 layers, . . . well), which is the key to the double heterostructure, is formed by a well-controlled and highly accurate vapor phase epitaxial growth method, the electrical-optical conversion efficiency is increased. Further, since the confinement layer can be grown at a thermally low temperature, there is no thermal diffusion and the composition can be made steep. Furthermore, the method of the present invention is advantageous for alleviating lattice strain in crystals.

[Brief explanation of the drawing]

Fig. 1 is a system diagram showing an embodiment of the method for continuously manufacturing optical semiconductor devices according to the present invention, Fig. 2 is a cross-sectional view of a wafer with a double heterostructure, and Fig. 3 is a cross-sectional view of a chip with a double heterostructure. , FIG. 4 is a schematic diagram showing a conventional manufacturing method. ■...Wafer, 2...Chip, 11...P
1-layer epitaxial process, 12... surface vapor phase cleaning process, 13... P-2 layer epitaxy process,
14..., N layer epitaxial process.

Claims (1)

[Claims] The vapor pressure controlled temperature difference method continuous liquid phase growth method and vapor phase growth method are combined in a series of systems, and the liquid phase growth method is applied to form a thick epitaxial layer, and the epitaxial layer is thin and requires precision. A method for continuously manufacturing an optical semiconductor device, wherein the vapor phase growth method described above is applied to the formation of the semiconductor device.