JPH05259012A - Semiconductor substrate and manufacture thereof - Google Patents

Abstract

PURPOSE:To laminate two substrates without generation of voids even when rough-surfaced single crystal silicon substrates are used by a method wherein an insulting film is constructed into a laminated structure consisting of a silicon oxide film and a silicon nitride film in the manufacture of a semiconductor substrate having a single crytal layer which is formed on a supporting substrate through an insulating film. CONSTITUTION:A single crystal silicon substrate 1, having a silicon oxide film 2 of 1mum in thickness, is prepared. Oxygen ions 3 of the dosage of 1X10<16>/cm<2> are implanted into the silicon oxide film 2 using the accelerated energy of 30 KeV before lamination of the above-mentioned material. Then, a commercially available second single crystal silicon substrate 4 of 1nm in surface roughness, is laminated with the substrate 1 as the supporting substrate. The lamination of the two substrates is conducted as follows: the oxygen ion implanted silicon oxide film 2 and the mirror surface of the second single crystal silicon substrate 4 are laminated, and a heat treatment is conducted at 950 deg.C for two hours. A SOI substrate is obtained by polishing the first single crystal silicon substrate 1 after lamination.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor substrate and a method for manufacturing the same, and in particular, a single crystal silicon substrate covered with an insulating film is bonded to another single crystal silicon substrate and then polished from one side to obtain single crystal silicon. The present invention relates to a semiconductor substrate in which a single crystal silicon layer is formed on an insulating film by thinning the substrate and a manufacturing method thereof.

[0002]

2. Description of the Related Art With the miniaturization of transistors, the distance between individual elements is becoming narrower, and complete element isolation is receiving attention. SOI (Silicon On Insu)
A substrate) is a substrate in which a single crystal silicon layer is present on an insulating film on a silicon substrate serving as a support substrate. By forming an element on the single crystal silicon layer, the silicon substrate below the element region is electrically connected. It is expected to be used as a countermeasure against latch-up and radiation soft error because it can be completely separated. One of the methods for manufacturing an SOI substrate is a bonding method for a single crystal silicon substrate. The conventional bonding technique will be described below with reference to FIG.

First, as shown in FIG. 3A, a first single crystal silicon substrate 2 having a silicon oxide film 2 on its surface is prepared. Next, as shown in FIG. 3B, the silicon oxide film 2 of the first single crystal silicon substrate 1 is overlaid on the second single crystal silicon substrate 4 as a supporting substrate, and heat treatment is performed for about 2 hours. Laminate.

The heat treatment requires a temperature of 1100 ° C. or higher, and when the heat treatment temperature is low, peeling occurs due to a slight tensile stress, and voids called voids are formed on the bonding surface 5. When laminating at 1100 ° C, the tensile stress is 60
It can withstand up to 0 kg / cm ₂ or more, but the bonding strength at 900 ° C. becomes 200 kg / cm ₂ or less. In addition, when laminating at 800 ° C or lower, voids may occur
Of Force International Symposium
On Silicon On Insulator Technology
And Devices (Proceedings of
4th international Symposi
um on “Silicon-on-Insult
or Technology and Device
s ") P61-71 (1990).

After the bonding, either side may be used, but polishing is performed from one side to form a single crystal silicon layer 1A on the silicon oxide film 3 as shown in FIG. Finalize.

[0006]

The above-described conventional method for laminating a single crystal silicon substrate has a problem that voids are generated at the laminating interface. It has been described above that a void is generated when the heat treatment temperature is 800 ° C. or lower, but the void is generated depending on the surface state of the substrate to be bonded at 1100 ° C. in the conventional method. The occurrence of voids is greatly related to the surface condition of the substrates to be bonded other than the bonding temperature, and one of them is the surface roughness. The condition of the surface roughness for preventing the generation of voids in the conventional example must be 0.5 nm or less. Considering that the surface roughness of a normal silicon substrate having a mirror surface is about 1 nm, this value is quite a severe requirement. Therefore, the SOI substrate using the conventional method has a problem that the cost becomes high because it cannot be manufactured with the conventional ordinary silicon substrate.

Further, since the SOI substrate has a structure in which a silicon oxide film is sandwiched between single crystal silicon substrates, there is potential internal stress. Therefore, when heat treatment is performed at 1100 ° C. under the conditions for a normal single crystal silicon substrate, crystal defects such as slips are introduced into the SOI substrate, causing crystal deterioration in the element region. However, the conventional method has a problem that when the heat treatment temperature is lowered below 1100 ° C., voids are generated and the bonding strength is lowered.

[0008]

A semiconductor substrate according to a first aspect of the present invention is a semiconductor substrate having a single crystal silicon layer provided on a supporting substrate via an insulating film, wherein the insulating film is a silicon oxide film and a silicon nitride film. It has a laminated structure composed of films.

In the method of manufacturing a semiconductor substrate according to the second invention, the second single crystal silicon substrate is bonded onto the surface of the first single crystal silicon substrate whose surface is covered with an insulating film, and then polished from one side. In the method for manufacturing a semiconductor substrate in which the first or second single crystal silicon substrate is thinned, oxygen ions or hydroxyl ions are implanted into the insulating film before bonding the second single crystal silicon substrate. It is a thing.

By implanting oxygen ions or hydroxyl ions into the insulating film before heat treatment, the silicon atoms in the single crystal silicon substrate and the implanted oxygen ions are bonded at the bonding interface to form silicon oxide. As a result, firm bonding is achieved in a thermal oxidation temperature region that is lower than in the past, and at the same time, the generation of voids is suppressed due to the progress of silicon oxide film formation. Furthermore, by using a silicon nitride film for the insulating film, oxygen can be prevented from diffusing into the silicon substrate below the insulating film during heat treatment, so that oxygen can be concentrated on the bonding surface to promote bonding. You can

[0011]

The present invention will be described below with reference to the drawings. 1A to 1C are sectional views for explaining a first embodiment of the present invention.

First, as shown in FIG. 1A, a device having a silicon oxide film 2 with a thickness of 1 μm on a first single crystal silicon substrate 1 is prepared as an element formation substrate, and oxygen ions 3 are attached before bonding. 1 × 10 ₁₆ / cm ₂ dose amount, 30 keV
Was implanted into the silicon oxide film 2 under the conditions of acceleration energy. The implantation depth with this implantation energy is about 60 nm
And oxygen ions exist near the bonding surface 5.

Next, as shown in FIG. 1B, a commercially available second single crystal silicon substrate 4 having a surface roughness of 1 nm was used as a supporting substrate. The two substrates were bonded together by superposing the oxygen ion-implanted silicon oxide film 2 and the mirror surface of the second single-crystal silicon substrate 4 on each other and performing heat treatment at 950 ° C. for 2 hours.

Next, as shown in FIG. 1 (c), the first single crystal silicon substrate 1 is polished after the bonding to form a single crystal silicon layer 1A having a thickness of 2 μm, and an SOI substrate is obtained. ..

The bonding of the substrates in the first embodiment is
By lowering the heat treatment temperature to 950 ° C., crystal defects such as slip were not observed. Further, the bonding surface 5 has a tensile strength and can withstand a stress of 600 kg / cm ₂ or more as in the conventional case. Further, in the conventional example, when bonding is performed using a commercially available single crystal silicon substrate having a surface roughness of about 1 nm, it is necessary to process the surface roughness to 0.5 nm or less to suppress the generation of voids. However, in the first embodiment, even if the surface roughness remains 1 nm,
No void was found on the bonding surface 5.

In the first embodiment, oxygen ions are implanted before the heat treatment to oxidize the silicon atoms of the second single crystal silicon substrate 4 to carry out the bonding, so that the second single crystal silicon as the supporting substrate is used. Void-free bonding was realized without processing the surface roughness of the substrate 4. Therefore, according to the first embodiment, the SOI substrate can be obtained by using the commercially available single crystal silicon substrate and performing the heat treatment at a lower temperature than the conventional one.

FIGS. 2A to 2C are sectional views for explaining the second embodiment of the present invention.

First, as shown in FIG. 2A, a first single crystal silicon substrate having a three-layer insulating film of a silicon oxide film 2A, a silicon nitride film 6, and a silicon oxide film 2B on the surface as an element formation substrate. 11, the hydroxyl ion 7 was injected into the insulating film at a dose of 1 × 10 ₁₆ / cm ₂ before bonding. The thickness of the silicon oxide film 2B is 1 μm, and the acceleration energy is set to 30 in the same manner as in the first embodiment so that oxygen ions do not escape to the layer below the silicon oxide film 2B.
It was set to keV.

Next, as shown in FIG. 2B, a commercially available second single crystal silicon substrate 14 having a surface roughness of about 1 nm was used as a supporting substrate. The bonding of the two substrates was performed by superimposing the silicon oxide film 2B and the mirror surface of the second single crystal silicon substrate 14 on each other and performing heat treatment at 950 ° C. for 1 hour.

Next, as shown in FIG. 2 (c), after bonding, polishing is performed from the first single crystal silicon substrate 11 side to form a single crystal silicon layer 11A having a thickness of 2 μm to obtain an SOI substrate. It was

The bonding surface 5A of the SOI substrate formed in the second embodiment is subjected to the heat treatment at 950 ° C. as in the first embodiment to prevent the generation of voids and has a tensile strength of 6%.
It was confirmed that it could withstand a stress of 00 kg / cm ₂ or more. Further, no crystal defects such as slips were observed due to the low temperature. In the second embodiment, the silicon nitride film 6 is sandwiched between the insulating films to prevent the hydroxyl ions from diffusing into the silicon oxide film 2A during the heat treatment. Thereby,
Since the hydroxyl group ions diffused only into the second single crystal silicon substrate 14 and promoted the oxidation of silicon atoms in the vicinity of the bonding surface 5A, bonding was possible in a shorter time than in the first embodiment. .. As described above, the void-free substrates can be bonded even in the second embodiment and the commercially available single crystal silicon substrate.

[0022]

As described above, according to the present invention, even if a single crystal silicon substrate having a surface roughness of about 1 nm is used, it is possible to bond the substrates without generating voids. As a result, it became possible to manufacture an SOI substrate by laminating a commercially available single crystal silicon substrate.
Further, since the heat treatment temperature can be lowered, the deterioration of the crystal in the element region was suppressed.

[Brief description of drawings]

FIG. 1 is a sectional view for explaining a first embodiment of the present invention.

FIG. 2 is a sectional view for explaining a second embodiment of the present invention.

FIG. 3 is a sectional view for explaining a conventional method for manufacturing a semiconductor substrate.

[Explanation of reference numerals] 1,11 First single crystal silicon substrate 1A, 11A Single crystal silicon layer 2,2A, 2B Silicon oxide film 3 Oxygen ion 4,14 Second single crystal silicon substrate 5 Bonding surface 6 Silicon nitride Membrane 7 Hydroxyl ion

Claims (4)

[Claims] 1. A semiconductor substrate having a single crystal silicon layer provided on a supporting substrate via an insulating film, wherein the insulating film has a laminated structure of a silicon oxide film and a silicon nitride film. substrate. 2. A first single crystal silicon substrate having a surface covered with an insulating film, a second single crystal silicon substrate bonded to the surface of the first single crystal silicon substrate, and then polished from one surface to obtain the first or second single crystal silicon substrate. A method of manufacturing a semiconductor substrate having a thin crystalline silicon substrate, wherein oxygen ions or hydroxyl ions are implanted into the insulating film before the second single crystal silicon substrate is bonded. .. 3. The insulating film is a silicon oxide film.
A method for manufacturing the semiconductor substrate described. 4. The method of manufacturing a semiconductor substrate according to claim 2, wherein the insulating film is a laminated film of a silicon oxide film and a silicon nitride film.