JPH08222715A - Manufacture of laminated soi substrate - Google Patents

Abstract

PURPOSE: To increase the bonding strength of the laminated surface of a laminated SOI substrate by a method wherein the SOI substrate is subjected to oxidation treatment in a high-temperature oxygen atmosphere to grow a buried oxide film and the interface between a surface active silicon layer and the buried oxide film is moved from the laminated surface of the SOI substrate and formed. CONSTITUTION: A surface oxidation single crystal silicon substrate 2 is laminated to a single-crystal silicon substrate 1 and a buried oxide film 5 is provided by bonding together the substrates 2 and 1. Then, the surface, which faces the side of the substrate 1, of the substrate 2 is polished to form a SOI substrate 6 which uses this polished surface as a surface active silicon layer 4. The SOI substrate 6 is subjected to oxidation treatment in a high-temperature oxygen atmosphere to grow the film 5 and the interface between the layer 4 and the film 5 is moved from the laminated surface of the substrate 6 and is formed. Thereby, the bonding strength of the laminated surface of the SOI substrate can be increased to a strength equal with that of a bulk material.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an SOI substrate, and more particularly to a method for manufacturing an SOI substrate in which an insulating layer is formed in a bonded single crystal silicon substrate.

[0002]

2. Description of the Related Art It is advantageous to form various elements in a thin semiconductor layer provided on an insulating material in terms of element characteristics and element isolation, rather than forming an integrated circuit on a bulk semiconductor substrate. . From this point of view, an SOI substrate in which a silicon single crystal layer for forming an element is provided on a single crystal silicon substrate via an insulating film of SiO ₂ is used.

As a method of manufacturing the SOI substrate, one of at least two silicon substrates is oxidized to form a surface oxide film, and the other silicon substrate is stacked with the surface oxide film sandwiched therebetween. There is a method of forming an insulating layer in a single crystal silicon substrate by bonding. In this method, two mirror-polished single crystal silicon substrates are made hydrophilic, and they are brought into contact with each other in a clean room temperature atmosphere, and then heat-treated at 800 to 1100 ° C. to bond them together. Upon bonding, an oxide film is generally formed in advance on one of the substrates, so that an insulating film of SiO ₂ is formed as a buried oxide film in the single crystal silicon substrate.

In the case of manufacturing a bonded SOI substrate, the silicon substrate side having a surface oxide film formed is polished to form a surface active silicon layer, or the single crystal silicon substrate side having no oxide film formed is polished. Either of these is used to form the surface active silicon layer. Figure 6
As shown in FIGS. 6A and 6B, after the surface oxide film 3 is formed on the first single crystal silicon substrate 1 and is bonded to the second single crystal silicon substrate 2 having no surface oxide film, FIG. (C
_As shown in ₁ ), the surface of the first single crystal silicon substrate 1 is polished and thinned to form a surface active silicon layer 4. As a result, the bonded SOI substrate 6 having the buried oxide film 5 is completed. In this case, the base side substrate is the second single crystal silicon substrate 2, and the surface active silicon layer side substrate is the first single crystal silicon substrate 1. Another method is to use the first surface-oxidized single-crystal silicon substrate 1 and the second surface-oxidized single-crystal silicon substrate 1.
After bonding the single crystal silicon substrate 2 of FIG.
_As shown in ₂ ), the surface of the second single crystal silicon substrate 2 is polished and thinned to obtain a surface active silicon layer 4
Are formed, the bonded SOI substrate 6 having the buried oxide film 5 is completed.

[0005]

[Problems to be Solved by the Invention]
When forming a buried oxide film in an OI substrate, the following problems occur. (1) The bonding strength of the bonding surface is SIM in which oxygen ions are implanted and implanted to form a buried oxide film inside silicon.
Low compared to OX substrate. In particular, if an unbonded portion due to air bubbles or the like remains on the bonded surface, the adhesive strength will decrease. (2) In the method of forming the surface active silicon layer by polishing the side of the silicon substrate on which the surface oxide film is formed (see FIGS. 6 (c ₁ ) and 6 (d ₁ )), it is formed in advance on the front and back surfaces of the silicon substrate. Since one side of the surface oxide film 3 is removed by polishing, a difference in thermal expansion coefficient between the oxide film layer and the silicon layer causes a difference in FIG.
_As shown in ₁ ), the bonded SOI substrate 6 warps. In particular, when the oxide film at the bonding interface, that is, the surface oxide film thickness of the single crystal silicon substrate 1 on the surface active silicon layer side is as thick as 500 nm or more, the warp of the substrate increases to about 40 μm. On the other hand, the film thickness is 100 nm
The following conventional substrates that are bonded through a thin oxide film can have a relatively small warp, but the adhesion strength decreases if particles of 0.1 μm or more adhere to the surfaces of the substrates during bonding. To do. Further, particles larger than the oxide film thickness at the bonding interface become a source of generation of voids. (3) Method of polishing by forming the single crystal silicon substrate side on which the oxide film is not formed (see FIGS. 6C ₂ and 6D ₂ ).
Then, since the bonded SOI substrate is formed with the surface oxide film left on the front and back surfaces of the first single crystal silicon substrate 1, even if the surface oxide film is thickened, the warpage of the substrate is reduced, At the bonding interface 9, the interface state density increases to 1 × 10 ¹² / cm ² eV due to the inclusion of impurities when bonding the oxide film and the active silicon layer. This interface state density cannot be reduced even if the film thickness of the surface oxide film of the first single crystal silicon substrate 1 is changed and bonded. Therefore, the electrical characteristics of the element (for example, MOS type FET) formed in the surface active silicon layer 4 deteriorates. M
In the OS type FET, for example, the controllability of the threshold voltage with respect to the set voltage between the source and the drain deteriorates.

The present invention has been made in view of the above-mentioned conventional problems, and a first object thereof is to provide an SOI substrate having a high bonding strength on a bonding surface. Secondly, in the case of a thin oxide film at the time of bonding, even when particles larger than the oxide film thickness of the substrate surface adhere, the adhesive strength at the bonding surface is not reduced, and An object of the present invention is to provide a method for manufacturing a bonded SOI substrate that can reduce voids at the bonding interface. Thirdly, the value of the interface state density generated at the interface between the thermal oxide film formed by thermally oxidizing the single crystal silicon substrate and the interface state density of the bonding interface with less warpage is shown. It is an object of the present invention to provide a method for manufacturing a bonded SOI substrate that can be reduced to a maximum.

[0007]

The present invention is intended for an SOI substrate in which an oxide film embedded in a silicon substrate is formed in advance, and a phenomenon in which the buried oxide film thickness is increased by subjecting this substrate to high temperature oxidation treatment is described. It was realized by finding. SO having a surface single-crystal silicon layer thickness of 320 nm and a buried oxide film thickness of 89 nm
For the I substrate, the substrate was placed in an oxygen atmosphere of 70% O ₂ in an inert gas at a flow rate ratio (the same applies hereinafter) at 1350 ° C., and the surface of the single crystal silicon layer was oxidized by about 180 nm. However, there was a phenomenon in which the buried oxide film was thickened to 118 nm (hereinafter referred to as a film increasing action or a film increasing effect).

Therefore, the increase amount of the buried oxide film with respect to each oxidation temperature was determined by changing the oxidation temperature condition under the condition that the thickness of the thermal oxide film formed on the surface of the SOI substrate was constant. As shown, it was confirmed that the film thickness of the buried oxide film increased as the oxidation temperature increased. The film increasing effect was confirmed at 1150 ° C. or higher. Similarly,
FIG. 4 shows the case where the oxidation time is fixed to 4 hours and the O ₂ concentration is fixed to 70%. In these figures, the oxidation temperature on the horizontal axis is represented by a value that is 10 ⁴ times the reciprocal of the absolute temperature. The temperature in degrees Celsius is also shown at the top of each figure. As is clear from FIG. 4, the increase in the buried oxide film thickness also increases as the oxidation temperature increases. Oxidation temperature is 11
If the temperature is 00 ° C. or less, the increase in the thickness of the buried oxide film is small, or if the oxidation time is a practical length, for example, 4 hours, the increase is below the detection level and there is no effect of thickening the film. When the oxidation temperature is raised to 1350 ° C., the increase amount of the buried oxide film thickness becomes about 30 nm.

Whereas the buried oxide film thickness of the single crystal silicon substrate according to the prior art is 80 to 90 nm, when the present invention is applied to perform oxidation treatment at 1350 ° C. and the surface oxide film thickness is about 400 nm, Buried oxide film thickness is 100 ~
It can be confirmed that the thickness increases to 120 nm. Therefore, in order to obtain the film thickening effect, a temperature condition of at least 1150 ° C. or higher is required, which is comparable to the annealing temperature. Further, since the melting point of silicon is 1412 ° C., the upper limit temperature needs to be set to a temperature condition lower than this.

Further, since the influence of the oxygen concentration in the oxygen atmosphere is considered to basically contribute to the film thickening action, different oxygen partial pressures due to the oxidation treatment for 4 hours at a temperature condition of 1350 ° C. after the annealing treatment are performed. When the amount of increase in the buried oxide film thickness due to is determined experimentally, a characteristic diagram as shown in FIG. 5 was obtained. According to this, it can be understood that the film-increasing effect can be obtained when the concentration is 1% O ₂ or more.
At% O ₂ concentration, the amount of film increase is very small, and since it is impossible to distinguish the difference from the irregularities at the interface, it is considered that the film increase effect can be obtained at a concentration of 1% O ₂ or more. This is because oxygen in the atmosphere is diffused inward from at least the surface single crystal silicon layer or the substrate single crystal silicon layer, and SiO ₂ is accumulated and accumulated basically at the interface of the buried oxide film. Since the conditions can be adjusted with the main factor, it is considered that the above-mentioned concentration of 1% O ₂ or more is required as the minimum concentration required for diffusion into the silicon layer. Of course, it can be understood from FIG. 5 that the film-increasing action can be performed with the oxygen concentration as a factor at a predetermined high temperature.

Therefore, according to the present invention, if the effect of increasing the thickness of the buried oxide film by subjecting the bonded SOI substrate to high temperature oxidation treatment is utilized, the unbonded portion remaining due to bubbles or the like on the bonding surface between the buried oxide film and silicon is used. Solving the problem of the decrease in the adhesive strength, the problem of the decrease in the adhesive strength due to the particles adhering to the surface of the bonded SOI substrate when the film thickness of the buried oxide film is 100 nm or less, or It was made based on the knowledge that the generation of voids due to the adhesion of particles larger than the oxide film thickness at the bonding interface can be reduced. Also,
In manufacturing a bonded SOI substrate, a surface active silicon layer is polished as a single crystal silicon substrate on the side where an oxide film is not formed to form an SOI substrate with less warp, and such an SOI substrate is subjected to high temperature oxidation. If the thickening effect of the buried oxide film by the treatment is utilized, the interface between the buried oxide film formed by bonding and the active silicon layer is buried inside the oxide film by the thickening function of the oxide film, and the electrical characteristics are improved. It is possible to form the actual interface position that affects the film thickness between the thickened oxide film and the surface active silicon layer. Therefore, it has been found that it is possible to reduce an increase in the interface state density generated at the interface between the surface active silicon layer and the buried oxide film, while reducing the warpage that occurs during bonding.

That is, by oxidizing the bonded SOI substrate at a high temperature, the buried oxide film becomes thicker, and the defective adhesion portion and the void portion are filled by the film increasing action, and oxygen bonds with the interfacial silicon to increase the interfacial adhesive strength. It can be done. Furthermore, after bonding the silicon substrates together, the surface-oxidized silicon layer of the SOI substrate is formed by polishing the side of the single crystal silicon substrate that has not been surface-oxidized, and then this substrate is subjected to high temperature oxidation treatment. By doing so, the thickness of the oxide film embedded in the silicon substrate is increased, and the interface position between the newly formed buried oxide film and the surface-active silicon layer is displaced from the bonding surface position by this film increasing action. It is something that changes. As a result, a portion where the interface state density is increased due to particles or the like attached during bonding can be taken into the embedded oxide film, and a new interface is formed between the oxide film surface grown inside the silicon substrate. To be done. This can reduce the interface state density of the SOI substrate.

From the above, the SO according to the present invention
The method for manufacturing the I substrate is as follows. First, one of the at least two silicon substrates is provided with an oxide film, and the silicon substrate is stacked with the oxide film sandwiched between the bonded SOI substrates.
After the substrate is manufactured, the bonded substrate is subjected to an oxidation treatment in a high temperature oxygen atmosphere. As a result, the buried oxide film is thickened by oxidizing the substrate in a high-temperature atmosphere, and the defective portion of the buried insulating layer due to particle adhesion or the like is repaired.
It is possible to increase the interfacial adhesion strength and the dielectric strength strength. In this case, the high temperature oxidation treatment temperature may be maintained within the range of 1150 ° C. or higher and lower than the melting point of the single crystal silicon substrate as described above, and the high temperature oxidation treatment may be performed at a concentration higher than the oxygen concentration during annealing. It may be performed in the oxygen gas atmosphere. In particular, in the above method for manufacturing a bonded SOI substrate, the film thickness of 10
When a base-side single crystal silicon substrate having a surface oxide film of 0 nm or less and a surface-active silicon layer-side single crystal silicon substrate having no surface oxide film were bonded together, the surface of the substrate had a thickness of 0. Even if particles with a size of 1 μm or more are attached, the embedded oxide film is thickened by oxidizing the substrate in a high temperature atmosphere, so that particles are attached to repair the defective portion of the embedded insulating layer. A decrease in adhesive strength can be prevented.

An SOI substrate having a buried oxide film formed by bonding and bonding a surface-oxidized single crystal silicon substrate and a single crystal silicon substrate, and polishing the single crystal silicon substrate side to use this as a surface active silicon layer Was formed, and the buried oxide film was thickened by oxidizing the SOI substrate in a high temperature oxygen atmosphere, and the interface between the surface active silicon layer and the buried oxide film was formed to move from the bonding surface. It is a thing. As the SOI substrate to be subjected to the high temperature oxidation treatment, a single crystal silicon substrate having a surface oxide film formed thereon and an unoxidized single crystal silicon substrate are bonded together, and then the unoxidized single crystal silicon substrate side is polished. By using the surface active silicon layer, an SOI substrate having no warp is obtained in advance. Then, the SOI substrate is subjected to an oxidation treatment in a high temperature atmosphere to thicken the bonded oxide film embedded inside the substrate, and the thickened oxide film causes the bonded surface to have a buried oxide film. The density of the interface states of the buried oxide film, which is taken in the inside of the device, can be reduced. Even in this case, the high temperature oxidation treatment temperature is 1150 ° C. as described above.
As described above, the temperature may be kept within a range lower than the melting point of the single crystal silicon substrate, and the high temperature oxidation treatment may be performed in an oxygen gas atmosphere having a concentration higher than the oxygen concentration during annealing.

[0015]

According to the above structure, when manufacturing a bonded SOI substrate, a base side single crystal silicon substrate having a surface oxide film obtained by applying an oxide film to one of the silicon substrates, and no surface oxide film are used. 1 on the SOI substrate in which the single crystal silicon substrate on the surface active silicon layer side is bonded
Since the high temperature oxidation process of 150 ° C. or higher is performed, the buried oxide film is further formed on the conventional surface oxide film, and the oxide film thickness becomes thicker than that before the high temperature oxidation process. Even in an SOI substrate in which a pinhole or a particle larger than the oxide film thickness on the substrate surface is adhered at the time of bonding to generate a void, the void is reduced due to the increase in the embedded oxide film thickness, and oxygen is silicon at the interface portion. Combined with
It is possible to increase the adhesive strength at the bonding interface to the level of bulk. Further, in the SOI substrate formed by polishing the single crystal silicon substrate to form the surface active silicon layer, a surface oxide film was formed on the surface of the substrate opposite to the surface active silicon layer side. With the structure, a difference in stress does not occur between the front and back surfaces of the silicon layer which is the base of the SOI substrate and is sandwiched between the buried oxide film and the surface oxide film, and as a result, the warp of the SOI substrate is reduced. Since such an SOI substrate is subjected to a high temperature oxidation treatment of 1150 ° C. or higher, a new surface oxide film is formed on the surface of the SOI substrate, that is, the upper surface of the surface active silicon layer side single crystal silicon substrate, and An oxide film is laminated on the oxide film on the lower surface of the side single crystal silicon substrate. At the same time, the buried oxide film grows and becomes thicker due to the effect of increasing the thickness of the buried oxide film. The warp of the manufactured SOI substrate is as small as that of a bulk, and since the buried oxide film is further formed on the buried oxide film by the high-temperature oxidation treatment, the bonding surface is embedded inside the bonding surface and the bonding surface is bonded. The adhered particles and the like are taken inside. As a result, the interface state density between the buried oxide film and the active silicon layer can be reduced to a value equivalent to that of the bulk.

[0016]

EXAMPLES Example 1 of the method for manufacturing a bonded SOI substrate according to the present invention will be described below with reference to the drawings. FIG. 1 is a schematic cross-sectional view of a substrate showing the manufacturing method of the SOI substrate in the order of manufacturing steps. First, FIG. 1 (a)
, The single crystal silicon substrate 2 on the surface active silicon layer side and the single crystal silicon substrate 1 on the base side
Each is mirror-polished and the base side single crystal silicon substrate 1
Then, for example, an oxidation treatment is performed at 1000 ° C. for 2 hours to form a surface oxide film 3 having a thickness of about 100 nm on the surface. Next, as shown in FIG. 1B, the surface active silicon layer side single crystal silicon substrate 2 is placed on the base side single crystal silicon substrate 1 and bonded at room temperature. Then, for example, 11
Annealing is performed at 00 ° C. for 2 hours to complete the bonding between the surface active silicon layer side single crystal silicon substrate 2 and the base side single crystal silicon substrate 1. Next, as shown in FIG. 1C, the surface of the bonded surface active silicon layer-side single crystal silicon substrate 2 is polished and thinned to a thickness of about 1.0 μm to form the active layer 4. It The oxide film remaining on the bonding interface becomes the buried oxide film 5.
Through these steps, the bonded SOI substrate 6 is completed. Up to this point, the manufacturing process is the same as the conventional one. Since the surface oxide film on the back surface of the bonded SOI substrate 6 is as thin as about 100 nm, in FIG.
An example of removing the OI substrate by cleaning is shown.

FIG. 1D shows a high temperature oxidation step in which the bonded SOI substrate 6 is oxidized in an atmosphere having an O ₂ gas concentration of more than 1% and 100% or less. Oxidation temperature is 1150
And a temperature lower than the melting point of the bonded SOI substrate,
Heat for several hours. By the high temperature oxidation treatment, an increase 7 of the buried oxide film thickness is formed at the interface of the buried oxide film 5.
Reference numeral 8 is a surface oxide film formed by the high temperature oxidation treatment.

Next, an experimental example to which the present invention is applied will be described. (1) Substrate oxidation: A mirror-polished base-side single crystal silicon substrate was subjected to an oxidation treatment at 1000 ° C. for 2 hours to form an oxide film having a thickness of 100 nm to obtain a substrate with an oxide film. (2) Bonding: The base-side single crystal silicon substrate with the oxide film and the mirror-polished surface-active silicon layer-side single crystal silicon substrate were bonded together. (3) Annealing: The two bonded single crystal silicon substrates were annealed at 1100 ° C. for 2 hours to complete the bonding. (4) Single-sided thin film processing: The surface of the single crystal silicon substrate on the surface active silicon layer side was polished and processed into a thin film so that the surface active silicon layer had a thickness of 1.0 μm. (5) High temperature oxidation treatment: Oxidation treatment was performed at a temperature of 1350 ° C. for 3 hours in an O ₂ gas atmosphere having a concentration of 70%. The oxide film thickness on the surface of the SOI substrate was 410 nm, and the buried oxide film thickness was increased by 28 nm.

With respect to the SOI substrate subjected to the high temperature oxidation treatment, the adhesive strength was measured and the void generation rate was investigated, and the following results were obtained. (1) Bonding strength: The bonding strength was 500 kg / cm ² in the conventional SOI substrate not subjected to the high temperature oxidation treatment, but the bonding strength was 800 kg when the high temperature oxidation treatment according to the present invention was added to the SOI substrate. / Cm ² and the strength became equivalent to that of bulk. (2) Void occurrence rate: In the SOI substrate according to the conventional technique, about 50% of the number of voids was generated on the substrate, but the void occurrence rate is about 1% by subjecting these substrates to high temperature oxidation treatment. Fell to. When the oxidation temperature is set to 1100 ° C. or lower in the high temperature oxidation treatment of the SOI substrate,
The increase in the buried oxide film thickness was slight, and the effect of thickening the film and reducing voids was not observed.

Next, a second embodiment of the method for manufacturing a bonded SOI substrate according to the present invention will be described with reference to the drawings. FIG. 2 is a schematic cross-sectional view of the substrate showing the method of manufacturing the SOI substrate in the order of manufacturing steps. First, FIG. 2 (a)
, The single crystal silicon substrate 2 on the surface active silicon layer side and the single crystal silicon substrate 1 on the base side
Are mirror-polished, and the base-side single crystal silicon substrate 1 is subjected to wet oxidation treatment at, for example, 1100 ° C. for 2 hours to form a surface oxide film 3 having a thickness of about 1000 nm. Next, as shown in FIG. 2B, the surface active silicon layer side single crystal silicon substrate 1 is placed on the base side single crystal silicon substrate 2 provided with the surface oxide film 3 and bonded at room temperature. Thereafter, for example, annealing is performed at 1100 ° C. for 2 hours, and the surface active silicon layer side single crystal silicon substrate 2
And the base-side single crystal silicon substrate 1 are bonded together. Next, as shown in FIG. 2C, the surface of the bonded surface-active silicon layer-side single crystal silicon substrate 2 is polished, and the surface-active silicon layer 4 is thinned to a thickness of about 1.0 μm. It is formed. The oxide film remaining on the bonding interface becomes the buried oxide film 5. Through these steps, the basic bonded SOI substrate 6 is completed. Up to this point, the manufacturing process is the same as the conventional one.

FIG. 2D shows a high temperature oxidation step in which the bonded SOI substrate 6 is oxidized in an atmosphere in which the O ₂ gas concentration exceeds 1% and 100% or less. Oxidation temperature is 1150
And a temperature lower than the melting point of the bonded SOI substrate,
Heat for several hours. By the high temperature oxidation treatment, an increase 7 of the buried oxide film thickness is formed on the upper surface of the buried oxide film 5.
A surface oxide film 8 is formed on the upper and lower surfaces of the bonded SOI substrate 6.

Next, an experimental example to which the second embodiment is applied will be described. (1) Substrate oxidation: Mirror-polished base-side single crystal silicon substrate 1 was subjected to wet oxidation treatment at 1100 ° C. for 2 hours, and 1.
A surface oxide film having a thickness of 0 μm was formed to obtain a substrate with an oxide film. (2) Bonding: The base-side single crystal silicon substrate 1 having the oxide film and the mirror-polished surface-active silicon layer-side single crystal silicon substrate 2 were bonded together. (3) Annealing: The two bonded single crystal silicon substrates were annealed at 1100 ° C. for 2 hours to complete the bonding. (4) Single-sided thin film processing: The surface of the substrate 2 on the active layer side was polished and processed so that the surface active silicon layer had a thickness of 1.0 μm. (5) High temperature oxidation treatment: Oxidation treatment was performed at a temperature of 1150 ° C. for 6 hours in an O ₂ gas atmosphere having a concentration of 70%. The oxide film thickness on the surface of the SOI substrate was 350 nm, and the buried oxide film thickness was increased by 5 nm.

When the warp and the interface state density of the SOI substrate subjected to the high temperature oxidation treatment were measured,
The following results were obtained. (1) Warp: When the high temperature oxidation treatment according to the present invention was added, the warp became 5 μm (like bulk). (2) Interface state density: In order to reduce the warpage, the interface state density of the conventional SOI substrate in which the base-side substrate was subjected to an oxidation treatment and bonded was 1 × 10 ¹² / cm ² eV. When the manufacturing method according to the present invention was used, the interface state density decreased to 1 × 10 ¹⁰ / cm ² eV. In this way, both the warpage and the interface state density could be reduced to values equivalent to those of the bulk. When the oxidation temperature is set to 1100 ° C. or lower in the high temperature oxidation treatment of the SOI substrate,
Almost no increase in the buried oxide film thickness was observed, and no effect of reducing the interface state density was observed.

[0024]

As described above, according to the present invention, one of the silicon substrates is provided with an oxide film, and the silicon substrates are stacked and bonded with the oxide film sandwiched therebetween, and then the high temperature oxidation treatment is performed. Since it was decided to apply
A buried oxide film is further formed on the buried oxide film of the OI substrate, and the buried oxide film thickness becomes thicker than that before the high temperature oxidation treatment. As a result, even in the SOI substrate in which particles larger than the oxide film thickness on the substrate surface are adhered at the time of bonding to generate voids, the voids are reduced due to the increase in the embedded oxide film thickness, and the bonding strength at the bonding interface is reduced. Can be increased to a strength comparable to bulk. Therefore, in the case of a bonded SOI substrate in which a thin buried oxide film is desirable, it is possible to solve the problems that have been conventionally encountered, such as the decrease in adhesive strength at the bonding interface and the occurrence of voids.

In manufacturing a bonded SOI substrate, the single crystal silicon layer on the side where the surface oxide film is not applied is polished on the bonded substrate to form a surface active silicon layer, and this is used as a basic SOI. Since the SOI substrate is used as a substrate and subjected to a high temperature oxidation treatment at 1150 ° C. or higher and lower than the melting point, an oxide film is increased on the bonding interface of the oxide films embedded inside the SOI substrate.
It is possible to reduce the bonding interface state density to a value equivalent to that of bulk. At the same time, it is possible to suppress the warp of the substrate to the same level as the bulk. Therefore, in the case of a bonded SOI substrate in which a thick buried oxide film is desirable, warpage of the substrate and high interface state density, which have been problems in the past, can be significantly reduced, and a high quality S
It becomes possible to manufacture an OI substrate.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of a substrate showing a method of manufacturing an SOI substrate according to a first embodiment in the order of manufacturing steps. (A) is mirror polishing and oxidation, (b) is bonding, (c) is polishing,
(D) shows each process of high temperature oxidation.

2A and 2B are schematic cross-sectional views of a substrate showing a second embodiment of the method for manufacturing an SOI substrate in the order of manufacturing steps. FIG. 2A is a mirror polishing and oxidation step, FIG. 2B is a bonding step, and FIG.
(D) shows each process of high temperature oxidation.

FIG. 3 is a diagram showing a correlation between an oxidation temperature and a buried oxide film thickness increase amount when a surface silicon single crystal layer is oxidized by about 180 nm in a high temperature oxidation step.

FIG. 4 is a diagram showing the correlation between the oxidation temperature and the increase amount of the buried oxide film thickness when the oxidation time is fixed at 4 hours and the O ₂ concentration is 70% in the high temperature oxidation step.

FIG. 5 is a diagram showing a correlation between an oxygen partial pressure in a high temperature oxidation step and an increase amount of a buried oxide film thickness.

FIG. 6 is a cross-sectional view illustrating a state of warpage occurring in an SOI substrate when a surface-active silicon layer-side single crystal silicon substrate having a thick surface oxide film and a base-side single crystal silicon substrate having no oxide film are bonded together. Schematic diagram ((a), (b), (c
1) and (d ₁ )), or when the base-side single-crystal silicon substrate having a surface oxide film and the surface-active silicon layer-side single-crystal silicon substrate having no oxide film are bonded together, the bonding interface is surface-active silicon. FIG. 3 is a schematic cross-sectional view ((a), (b), (c ₂ ), and (d ₂ )) explaining that it is located on the layer side, where (a) is mirror polishing and oxidation, and (b) is bonding. , (C ₁ ) and (c ₂ ) show the state after polishing, and (d ₁ ) and (d ₂ ) show the state after polishing.

[Explanation of symbols]

 1 Surface Oxidized Single Crystal Silicon Substrate 2 Single Crystal Silicon Substrate 3,8 Surface Oxide Film 4 Surface Active Silicon Layer 5 Embedded Oxide Film 6 Bonded SOI Substrate 7 Embedded Oxide Film Thickness Increase 9 Surface Active Silicon Layer and Embedded Oxide Film interface

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tatsuhiko Katayama 2612 Shinomiya, Hiratsuka-shi, Kanagawa Komatsu Electronic Metals Ltd.

Claims (3)

[Claims] 1. An SOI substrate in which a surface-oxidized single-crystal silicon substrate and a single-crystal silicon substrate are bonded and bonded to each other to provide a buried oxide film, and the single-crystal silicon substrate side is polished to form a surface-active silicon layer. And a buried oxide film is grown by subjecting this SOI substrate to an oxidation treatment in a high temperature oxygen atmosphere, and the interface between the surface active silicon layer and the buried oxide film is moved from the bonding surface. A method for manufacturing a bonded SOI substrate. 2. The method for manufacturing a bonded SOI substrate according to claim 1, wherein the high temperature oxidation treatment temperature is maintained in the range of 1150 ° C. or higher and lower than the melting point temperature of the single crystal silicon substrate. 3. The bonding S according to claim 1 or 2.
A method of manufacturing a bonded SOI substrate, characterized in that, in the method of manufacturing an OI substrate, an oxide film formed on the surface of one silicon substrate is made 100 nm or less in advance to obtain an SOI substrate in which the other silicon substrate is bonded.