JPH0950946A - Manufacturing for semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method adequate for a large-size semiconductor substrate, in which two semiconductor substrates are put in a pressure contact with each other and bonded by heat treatment. SOLUTION: Two semiconductor substrates 10 and 16 are put in a pressure contact and bonded by heat treatment. In this case part of bonding face of at least one of substrates 10 and 16 is removed to form a plurality of projected parts 10a, and put in a pressure contact.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a semiconductor device manufactured by using a technique of bonding different kinds of substrates.

[0002]

2. Description of the Related Art In recent years, optoelectronic integrated circuits (Optoelectronic
Interest in integrated circuits (OEIC) is increasing. Optical devices made of GaAs and InP and Si and Ga
The main reason for this is that by integrating electronic devices using As as a material, dramatic improvements in operating characteristics and realization of new functions are expected. Traditionally,
In order to realize OEIC, research on techniques for directly crystal-growing materials such as Si, GaAs, and InP having different lattice constants has been actively conducted. There is a remarkable progress in this crystal growth technology for lattice mismatched systems, such as GaAs on Si, InP on Si and Ga.
Room temperature oscillations of semiconductor lasers made of InP on As have been achieved. However, this type of crystal growth film has a problem that dislocations are introduced due to lattice mismatch and difference in thermal expansion coefficient. Many attempts have been made to reduce the dislocation density, such as introducing various buffer layers, but the dislocation density is still 10 ⁵ to 10 ⁷ cm ^-2.
And several orders of magnitude higher than the lattice-matched growth layer. This makes it difficult to improve the characteristics and reliability of the laser. As another method of integrating such materials having different lattice constants, there is a method of directly bonding different types of substrates. Direct bonding technology has been actively researched in the field of Si, and attempts to put it into practical use are progressing. For materials other than Si, Ga
InP-based lasers on As substrates and InP-based lasers on Si substrates have been reported, and the characteristics and reliability that are the same as those of lattice-matched systems have been obtained.

An InP-based laser element having a wavelength of 1.3 μm manufactured on a GaAs substrate by using the direct bonding technique for different kinds of substrates will be described below as an example. FIG. 4 is a diagram showing a manufacturing process of the laser element, and is a cross-sectional view of one element in the substrate. The steps are as follows. That is, 1) First, p-InGaAs is formed on the p-InP substrate 1 by MOCVD.
Etching stop layer 2, p-InP clad layer 3, wavelength 1.3 μ
A GRIN-SCH-MQW active layer 4 oscillating at m and an n-InP clad layer 5 are epitaxially sequentially laminated (FIG. 4A). 2) Next, the laminated substrate is washed with a mixed solution of H ₂ SO ₄ : H ₂ O ₂ : H ₂ O = 3: 1: 1 and hydrofluoric acid. Further, the n-GaAs substrate 6 is washed with a mixed liquid of H ₂ SO ₄ : H ₂ O ₂ : H ₂ O = 1: 1: 10 and hydrofluoric acid. Then, the laminated substrate and the n-GaAs substrate 6
After drying, the n-InP cladded layer 5 surface of the laminated substrate and n-Ga
The mirror surface side of the As substrate 6 is bonded at room temperature in the atmosphere. At this time, the cleavage planes of the laminated substrate and the n-GaAs substrate 6 are aligned (FIG. 4B). 3) After that, a weight of molybdenum (Mo) of about 30 g / cm ² is placed on the laminated substrates, and heat treatment is performed at 600 ° C. for 30 minutes in a hydrogen atmosphere. As a result, the n-InP cladding layer 5 and the n-GaAs substrate 6 are well bonded. 4) Next, the p-InP substrate 1 is removed by etching with hydrochloric acid (HCl). At this time, since the p-InGaAs etching stop layer 2 is not etched with hydrochloric acid, the etching is automatically stopped on this surface (FIG. 4 (c)). 5) Next, using the SiNX film with a width of about 5 μm as a mask, p-InGaAs is etched with a sulfuric acid-based etching solution and a hydrochloric acid-based etching solution.
The etching stop layer 2 and the p-InP clad layer 3 are partially removed by etching to form a stripe-shaped inverted mesa having a mesa bottom width of about 2 μm. 6) Next, after forming the SiNX film 7 on the entire surface of the laminated substrate, only the upper part of the mesa is opened to form a current path. afterwards,
The GaAs substrate 6 is polished to about 100 μm, and the p-side electrode 8, n
The side electrode 9 is formed (FIG. 4D).

There are still many unclear points about the mechanism of this direct adhesion, but in the case of Si with each other, it is explained as follows. By treating the substrate with a sulfuric acid-based etching solution, the surface becomes hydrophilic. When the hydrophilic surfaces are bonded together, the OH groups adsorbed on the surfaces form hydrogen bonds. After that, it is explained that by performing heat treatment, a dehydration condensation reaction occurs and the adhesive strength is increased. Also, at the GaAs / InP adhesive interface, the
Dislocations are present at 15 nm intervals. This is GaAs and InP
Since the lattice constants of are different by about 3.7%, it is explained that dislocations are formed approximately every 27 atoms. However, this dislocation is observed only in the vicinity of the interface, and is not observed at a distance of several atomic layers from the interface. In this way, the technique of directly adhering the epitaxial layer laminated on the substrate to another substrate is
This makes it possible to fabricate InP lasers with different lattice constants on a GaAs substrate by a simple method and without impairing the characteristics and reliability, which is the most promising method for realizing OEIC.

[0005]

When different types of substrates are bonded together, the adhesion between the surfaces to be bonded together, that is, the surface flatness between them is important. However, the current technology has a limitation on the surface flatness of the substrate and the epitaxial layer stacked on the substrate. Therefore, for example, even if the substrates are enlarged and the large-area substrates are bonded to each other for the purpose of reducing the manufacturing cost, it has not been possible. Therefore, an object of the present invention is to enable bonding of large-area substrates of different types to each other and realize a reduction in device manufacturing cost.

[0006]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and the invention of claim 1 is a semiconductor having a step of pressing two semiconductor substrates together and adhering them to each other by heat treatment. In the method of manufacturing the device, at least one of the surfaces of the bonding surface of the substrate is removed to form a plurality of convex portions, and then pressure contact is performed. According to a second aspect of the invention, in the first aspect of the invention, a part of the surface of the adhesive surface of one substrate is removed to form a plurality of convex portions, and the convex surface is formed on the adhesive surface of the other substrate. It is characterized in that a concave portion for positioning the portion is provided and then pressure-welded. Here, the semiconductor substrate includes a laminated substrate in which semiconductor layers are laminated on the surface thereof, and an optical device or electronic device formed in or on the substrate.

[0007]

As described above, after removing a part of the surface of the adhesive surface of at least one substrate to form a plurality of convex portions, 2
When a plurality of semiconductor substrates are pressed and bonded together, even if the size of the substrate is increased, the pressure applied at the time of pressing will distort the surface of the substrate on which a plurality of convex portions are formed, so that all convex portions of one substrate will Make sure contact with one of the opposing substrates. Therefore,
By heat-treating and bonding in this state, substrates having a larger area than in the past can be bonded to each other. Further, after forming a convex portion on the adhesive surface of one substrate, and providing a concave portion for positioning the convex portion on the adhesive surface of the other substrate, when pressure contact,
The two substrates can be easily aligned and bonded.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the embodiments shown in the drawings. FIG. 1 is a process explanatory view of an example of a method for manufacturing a semiconductor device according to the present invention, and is a cross-sectional view of one element in a substrate. The steps are as follows. That is, 1) First, p-InGa is formed on the p-InP substrate 11 by the MOCVD method.
As etching stop layer 12, p-InP clad layer 13, wavelength
A GRIN-SCH-MQW active layer 14 oscillating at 1.3 μm and an n-InP clad layer 15 are sequentially laminated (FIG. 1A). 2) Next, using the SiO ₂ film as a mask, the p-InGaAs 12 is etched with a sulfuric acid-based and hydrochloric acid-based etching solution to form a convex portion 10a having a mesa stripe with a width of about 2 μm at the upper portion of the mesa and having a mesa-like shape. To form. On the substrate 11 having a diameter of 2 inches, about 100 mesa stripes are formed in parallel at regular pitch intervals. 3) Next, the SiO ₂ film 17 is formed only on the side surface of the convex portion 10a (FIG. 1B). 4) Next, the laminated substrate 10 is treated with H ₂ SO ₄ : H ₂ O ₂ : H ₂ O = 3: 1: 1.
Treatment with the mixed solution of 1 and hydrofluoric acid. Further, the n-GaAs substrate 16 is treated with a mixed solution of H ₂ SO ₄ : H ₂ O ₂ : H ₂ O = 1: 1: 10 and hydrofluoric acid. Then, after drying the laminated substrate 10 and the substrate 16, the n-InP cladding layer 15 of the laminated substrate 10 and the mirror surface side of the n-GaAs substrate 16 are bonded to each other in the room temperature atmosphere. This time,
Align the cleavage planes of the laminated substrate 10 and the substrate 16 (see FIG. 1).
(C)). After that, about 30g /
A weight made of molybdenum (Mo) of about cm2 is placed, and heat treatment is performed at a temperature of 600 ° C for 30 minutes in a hydrogen atmosphere. At this time, the laminated substrate 10 has n- which forms the upper ends of the plurality of mesa stripe-shaped convex portions 10a formed in parallel over the entire surface.
The InP cladded layer 15 is pressed against the substrate 16 with a weight. In this case, even if the upper end portions of the plurality of convex portions 10a are not on the same plane and the flatness is not good, the substrate 11 is pressed by pressing.
Can be distorted, so that all of the plurality of n-InP cladded layer 15 portions formed on the substrate 11 can be reliably pressed and bonded to the n-GaAs substrate 16. 5) Next, the p-InP substrate 11 is removed by etching with hydrochloric acid (HCl). At this time, since the p-InGaAs etching stop layer 12 is not etched with hydrochloric acid, etching is automatically stopped on this surface. Also, on the side surface of the convex portion 10a,
Since the SiO2 film 17 is formed, the p-InP clad layer 1
3. The active layer 14 and the n-InP clad layer 15 are not etched (FIG. 1 (d)). 6) Next, the polyimide 18 is formed only on the side surface of the mesa, and then the GaAs substrate 16 is polished to about 100 μm, and the n-side electrode 20 and the p-InGaAs etching stop layer 1 are formed on the n-GaAs substrate 16.
A p-side electrode 19 is formed on 2 (FIG. 1 (e)).

In this embodiment, the laminated substrate 10 is securely pressure-bonded and adhered to the n-GaAs substrate 16 at the n-InP clad layer 15 portion forming the upper ends of the plurality of mesa stripe-shaped convex portions 10a. The size of the substrate 10 and the n-GaAs substrate 16 can be increased.

Further, as shown in FIG. 2, when the mesa stripes 21 formed on the laminated substrate 10 are divided at regular intervals along the middle to form a smaller convex portion, the convex shape is more surely formed. The laminated substrate 10 can be adhered by the section. Further, as shown in FIG. 3, if a groove 22 is formed in advance on the GaAs substrate 16 so as to be aligned with the mesa stripe 21 of the laminated substrate 10, the position where the GaAs substrate 16 and the laminated substrate 10 are bonded to each other. Matching becomes easy.

In the above embodiments, the polyimide embedded ridge waveguide type structure has been described, but another structure may be used after the bonding. Also, the oscillation wavelength, the active layer structure,
The semiconductor material composition is not limited to that in the above embodiment.
Also, when removing the InP substrate with hydrochloric acid,
Although protected by the SiO ₂ film, the material to be protected is not limited to this and may be protected by a resist or the like after the bonding. Furthermore, the higher the heat treatment temperature for adhesion, the higher the adhesive strength. But,
If the temperature is too high, the characteristics of the device formed on the substrate may be deteriorated. Therefore, it goes without saying that this temperature is appropriately selected.

The present invention can be applied to manufacture an OEIC composed of a light emitting / receiving element and an electronic device formed on a different type substrate. For example, GaAs electronic devices on a GaAs substrate and InP-based light emitting and receiving elements, or electronic devices on a Si substrate and In
The present invention can be applied to various combinations such as P 2 -based light emitting and receiving elements.

[0013]

As described above, according to the first aspect of the present invention, in the method of manufacturing a semiconductor device, which comprises the step of pressing two semiconductor substrates and adhering them to each other by heat treatment, the bonding surface of at least one of the substrates. Since a part of the surface of is removed to form a plurality of convex portions and then pressure contact is performed, there is an excellent effect that substrates having a larger area can be adhered to each other as compared with the conventional case. Further, according to claim 2, a part of the surface of the adhesive surface of one substrate is removed to form a plurality of convex portions, and a concave portion for positioning the convex portions is formed on the adhesive surface of the other substrate. Since the two substrates are pressed together after being provided, there is an excellent effect that the two substrates can be easily aligned and bonded.

[Brief description of drawings]

1A to 1E are process explanatory views of an example of a method for manufacturing a semiconductor device according to the present invention.

FIG. 2 is a plan view of an embodiment of a substrate used in the present invention.

FIG. 3 is an explanatory diagram of another embodiment of the present invention.

4A to 4D are process explanatory views of a conventional method for manufacturing a semiconductor device.

[Explanation of symbols]

 10 laminated substrate 10a convex part 11 p-InP substrate 12 etching stop layer 13 p-InP clad layer 14 active layer 15 n-InP clad layer 16 GaAs substrate 17 SiO2 film 18 polyimide 19 p side electrode 20 n side electrode 21 mesa stripe 22 groove

Claims (3)

[Claims] 1. A method for manufacturing a semiconductor device, comprising a step of pressing two semiconductor substrates together and adhering them to each other by heat treatment, wherein a part of the bonding surface of at least one of the substrates is removed to form a plurality of convex shapes. A method for manufacturing a semiconductor device, which comprises press-contacting after forming the portion. 2. A part of the adhesive surface of one substrate is removed to form a plurality of convex portions, and a concave portion for positioning the convex portions is provided on the adhesive surface of the other substrate, The method for manufacturing a semiconductor device according to claim 1, wherein the step of pressing is performed. 3. The method for manufacturing a semiconductor device according to claim 1, wherein an optical device or an electronic device is formed in or on at least one of the semiconductor substrates.