JPH1197379A - Semiconductor substrate and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor substrate with an increased reliability and to manufacture high-quality semiconductor substrates without decreasing the yield. SOLUTION: A method for manufacturing a semiconductor substrate includes a step for forming a protecting film 12 against contamination on a single crystal silicon substrate 11, a step for forming an ion implanted layer 13 on the single crystal silicon substrate 11, a step for eliminating a protecting film 12 against contamination, a step for forming an insulating film 15 on a base substrate 14, a step for making the surface of the single crystal silicon substrate 11 on the side of ion implantation and the surface of the insulating film 15 on the side of the base substrate 14 hydrophilic, a step for adhering the single crystal silicon substrate 11 and the base substrate 14 with their hydrophilic sides inside, a step for peeling the single crystal silicon substrate 11 from the ion implanted layer 13 by heat to form a single crystal silicon thin film 11b and so on to complete a SOI(silicon on insulator) substrate 16.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a base substrate,
The present invention relates to a semiconductor substrate provided with a semiconductor layer for element formation in a state of being electrically insulated from the base substrate, and a method for manufacturing the same.

[0002]

2. Description of the Related Art As a semiconductor substrate of this kind, for example,
SOI having a structure in which a silicon single crystal film is provided as a semiconductor layer
(Silicon On Insulator) substrate. This has a structure in which an insulating oxide film is formed on a silicon substrate and a silicon single crystal film is formed thereon. By using such a semiconductor substrate, an insulating separation process from the substrate can be performed. This eliminates the need for a separate operation, provides good isolation performance, and enables the formation of an integrated circuit by forming elements on a silicon single crystal film with a high degree of integration.

[0003] As a method of manufacturing a silicon single crystal film for such an SOI structure, various methods have conventionally been adopted. Among them, a method of manufacturing a silicon single crystal film through the following three steps is described. Semiconductor thin film manufacturing technology
It is disclosed in Japanese Patent Publication No. 211128. Hereinafter, the manufacturing method will be described with reference to FIG.

First, as a first step, a semiconductor substrate material 1 on which a contamination protection film 1a such as an oxide film is formed on the upper surface is introduced.
Hydrogen gas or rare gas is ion-implanted from the side of the contamination protective film 1a (see FIG. 8A) to form an ion-implanted region 2 in which implanted ions are distributed at a predetermined depth in the semiconductor substrate material 1. Next, as a second step, a base substrate 3 made of at least one rigid material is bonded to the surface of the semiconductor substrate material 1 on the ion implantation side by a bonding method or the like (see FIG. 8B). In this case, it is desirable that the insulating film 4 such as an oxide film is formed in the point that a semiconductor substrate can be used as the base substrate 3 and an SOI substrate is finally formed.

Further, as a third step, by subjecting the semiconductor substrate material 1 and one object of the base substrate 3 to heat treatment, the semiconductor substrate is bounded by the microvoids (microbubbles) formed in the ion implantation region 2. The material 1 and the thin film portion are separated so as to be separated from each other, and an SOI substrate 6 having a structure in which a silicon single crystal film 5 is bonded to the base substrate 3 via an insulating film 4 or the like is formed (see FIG. 8C). ).

Actually, since a surface step and a defect layer of about several nm exist on the peeled surface, a polishing process and an etching process are performed on the peeled surface to finish the silicon single crystal film 5 flat. A predetermined film thickness (for example, 0.1 μm
m) to complete the SOI substrate 6 (see FIG. 8D).

[0007]

When the SOI substrate 6 is manufactured through the above-described steps, the following problems may actually occur. That is,
As shown in FIG. 9, in the above-described third heat treatment step, the semiconductor substrate that should originally become the silicon single crystal film 5 on the base substrate 3 side despite the occurrence of the peeling phenomenon at the microvoid portion. Expected area of peeling on material 1 side is
A phenomenon that the semiconductor substrate material 1 is partially left on the side of the semiconductor substrate material 1 may occur (the remaining portion is denoted by the letter Q).
Is shown). As a result, a non-uniformly peeled silicon layer adheres to the base substrate 3. When such a phenomenon occurs, there is a problem that the quality of the SOI substrate 6 is significantly deteriorated and the yield is deteriorated. In FIG. 9, the phenomenon that the remaining portion Q occurs is schematically shown due to restrictions on drawing, but actually occurs at many locations dispersed throughout the semiconductor substrate material 1.

It is assumed that the above phenomenon occurs because the bonding between the semiconductor substrate material 1 and the base substrate 3 is not performed uniformly over the entire bonding region. At present, the cause of such a defect in the bonded state is that the flatness of the contamination protective film 1a on the semiconductor substrate material 1 is impaired due to the execution of the ion implantation process, and that the contaminants are removed by the contamination protective film. It is conceivable that it remains in the vicinity of the surface in a segregated state. Further, in a state where such a bonding defect exists, there is a possibility that the bonding strength between the insulating film 3 and the silicon single crystal film becomes insufficient even if the phenomenon shown in FIG. 9 does not occur. This causes the reliability of the SOI substrate 6 to decrease.

Accordingly, an object of the present invention is to firstly increase the bonding strength between a base substrate and a semiconductor layer provided on the base substrate in an electrically insulated state, thereby improving reliability. Secondly, it is an object of the present invention to provide a method of manufacturing a semiconductor substrate which can manufacture a high quality semiconductor substrate without lowering the yield.

[0010]

According to the present invention, a semiconductor layer (11b) for element formation is provided on a base substrate (14) in a state of being electrically insulated therefrom. In the semiconductor substrate, the semiconductor layer (11b) and the base substrate (14) are directly or naturally oxidized (11a,
In the case of joining via 14a), the joining strength between them is increased, and the reliability is improved.

According to a third aspect of the present invention, in the protective film forming step, the contamination protective film (12) is formed on the semiconductor substrate material (11) prepared separately from the base substrate (14). At the same time, in the ion implantation step, the semiconductor substrate material (11) is ion-implanted from the contamination protective film (12) side to form an ion-implanted layer (1).
3) is formed, and the ion-implanted layer (1) is formed.
3) is in a distribution state parallel to the surface of the semiconductor substrate material (11).

Next, in the protective film removing step, after the contamination protective film (12) on the semiconductor substrate material (11) is removed, in the hydrophilic treatment step, the semiconductor substrate material (1) is removed.
The surface on the ion implantation side of 1) and the base substrate (1
The surface of 4) is subjected to a hydrophilization treatment, and further, in the bonding step, the semiconductor substrate material (11) and the base substrate (14) are bonded on the hydrophilization-treated surface. Thereafter, a heat treatment is performed in a peeling step,
Along with this heat treatment, in the semiconductor substrate material (11), microbubbles are aggregated in the defect layer region formed by the ion-implanted layer (13) to generate macro bubbles, thereby forming the defect layer region. Separation occurs at the boundary. As a result, the thin film semiconductor layer (11b) becomes the base substrate (1).
4) It is possible to form a substrate structure (corresponding to an SOI structure) laminated on the substrate in an electrically insulated state.

According to such a manufacturing method, before the bonding step for bonding the semiconductor substrate material (11) and the base substrate (14) is performed, the contamination protection on the semiconductor substrate material (11) is performed. Since the film (12) is removed, the flatness of the contamination protective film (12) is impaired with the execution of the ion implantation step, or contaminants are present near the surface of the contamination protective film (12). Even in a situation where the semiconductor substrate remains in a segregated state, the bonding state between the semiconductor substrate material (11) and the base substrate (14) is made uniform over the entire bonding region. Will be able to

As a result, when the peeling step is performed, the peeling phenomenon of the semiconductor substrate material (11) progresses uniformly in the entire defect layer region portion. ) Does not occur that the expected peeling region on the side of the semiconductor substrate material (11) to be the upper semiconductor layer (11b) remains partially on the side of the semiconductor substrate material (11). Therefore, the quality of the semiconductor substrate to be manufactured can be improved, and the yield can be improved.

According to a fourth aspect of the present invention, the bonding strength between the semiconductor substrate material (11) and the base substrate (14) is reduced when the peeling phenomenon occurs due to the heat treatment in the peeling step. In the case where the stress is set to be larger than the stress due to internal gas expansion generated in the ion implantation layer (13), a good peeling phenomenon can be expected in the peeling step.

According to a fifth aspect of the present invention, an ion-implanted layer (13) is formed on an integrated body of the semiconductor substrate material (11) and the base substrate (14) bonded in the bonding step. When the heat treatment is performed at a low temperature at which the peeling phenomenon does not occur in the defective layer region portion to improve the bonding strength between the two, the peeling step is performed and then the semiconductor substrate material is used. (1
1) The bonding strength between the base substrate (14) and the base substrate (14) can be made larger than the stress due to internal gas expansion generated in the ion-implanted layer (13) when the separation phenomenon occurs due to the heat treatment in the separation step. Thus, a good peeling phenomenon can be expected in the peeling step.

According to a sixth aspect of the present invention, in the hydrophilic treatment step, a natural oxide film is formed on the surface of the semiconductor substrate material on the ion-implanted side and on the surface of the base substrate. (11a, 14a) will be formed. Therefore, in the case of a semiconductor substrate manufactured through a bonding process and a peeling process thereafter,
Since the semiconductor layer (11b) and the base substrate (14) are joined via the natural oxide films (11a, 14a), the semiconductor layer (11b) and the base substrate (1) are joined.
4) The bonding strength between them is increased, and the reliability is improved.

According to a seventh aspect of the present invention, in the hydrophilization step, hydroxyl groups adhere to the surface of the semiconductor substrate material (11) on the ion-implanted side and the surface of the base substrate (14). This hydroxyl group is converted to the semiconductor substrate material (11) and the base substrate (1).
4) acts to promote bonding between them. In the case of a semiconductor substrate manufactured through such a hydrophilic treatment step, a subsequent bonding step, and a peeling step, a state in which the semiconductor layer (11b) and the base substrate (14) are directly bonded. Therefore, the bonding strength between the semiconductor layer (11b) and the base substrate (14) is increased, and the reliability is improved.

According to the eighth aspect of the present invention, in the protective film forming step, the contamination protective film (12) is formed on the semiconductor substrate material (11) prepared separately from the base substrate (14). At the same time, in the ion implantation step, the semiconductor substrate material (11) is ion-implanted from the contamination protective film (12) side to form an ion-implanted layer (1).
3) is formed, and the ion-implanted layer (1) is formed.
3) is in a distribution state parallel to the surface of the semiconductor substrate material (11).

Next, in the protective film removing step, after the upper surface portion of the contamination protective film (12) on the semiconductor substrate material (11) is removed, in the hydrophilic treatment step, the contamination protective film of the semiconductor substrate material (11) is removed. The surface of (12) and the surface of the base substrate (14) are subjected to a hydrophilic treatment, and further, in the bonding step, the semiconductor substrate material (1) is treated.
1) and the base substrate (14) are bonded together on the hydrophilized surface. Thereafter, heat treatment is performed in a peeling step, and with this heat treatment, the semiconductor substrate material (1
In 1), microbubbles are aggregated in the defect layer region formed by the ion-implanted layer (13) to generate macro bubbles, thereby causing separation at the defect layer region. As a result, it is possible to form a substrate structure (corresponding to an SOI structure) in which the thin film semiconductor layer (11b) is laminated on the base substrate (14) in an electrically insulated state.

According to such a manufacturing method, before the bonding step for bonding the semiconductor substrate material (11) and the base substrate (14) is performed, the contamination protection on the semiconductor substrate material (11) is performed. Since the upper surface portion of the film (12) is removed, the flatness of the contamination protective film (12) is impaired or the vicinity of the surface of the contamination protective film (12) is reduced with the execution of the ion implantation step. Even if the contaminants remain in a segregated state, the state of bonding between the semiconductor substrate material (11) and the base substrate (14) is uniform over the entire bonded region. Will be able to

As a result, at the time of performing the peeling step, the peeling phenomenon of the semiconductor substrate material (11) progresses uniformly in the entire defective layer region portion. ) Does not occur that the expected peeling region on the side of the semiconductor substrate material (11) to be the upper semiconductor layer (11b) remains partially on the side of the semiconductor substrate material (11). Therefore, the quality of the semiconductor substrate to be manufactured can be improved, and the yield can be improved.

As in the method for manufacturing a semiconductor substrate according to the ninth aspect, the bonding strength between the semiconductor substrate material (11) and the base substrate (14) may be reduced when the peeling phenomenon occurs due to the heat treatment in the peeling step. In the case where the stress is set to be larger than the stress due to internal gas expansion generated in the ion implantation layer (13), a good peeling phenomenon can be expected in the peeling step.

According to a tenth aspect of the present invention, in the protective film removing step for removing the upper surface portion of the contamination protective film (12), chemical etching or chemical etching and mechanical polishing are performed. In the case where the combination is made to remove the contaminated area in the contamination protective film (12) and to planarize the surface,
Since the flatness of the surface of the contamination protective film (12) is improved, the bonding strength between the semiconductor substrate material (11) and the base substrate (14) bonded via the contamination protective film (12) is sufficiently increased. Can be enhanced.

According to the manufacturing method of the eleventh aspect, an integrated body of the semiconductor substrate material (11) and the base substrate (14) bonded in the bonding step is formed by the ion implantation layer (13). When the heat treatment is performed at a low temperature at which the peeling phenomenon does not occur in the defective layer region portion to improve the bonding strength between the two, the peeling step is performed and then the semiconductor substrate material is used. (1
1) The bonding strength between the base substrate (14) and the base substrate (14) can be made larger than the stress due to internal gas expansion generated in the ion-implanted layer (13) when the separation phenomenon occurs due to the heat treatment in the separation step. Thus, a good peeling phenomenon can be expected in the peeling step.

In the method of manufacturing a semiconductor substrate according to the fifteenth aspect, in the heat treatment step, the heat treatment is performed at a temperature higher than the heat treatment temperature in the peeling step, whereby the material between the semiconductor substrate material (11) and the base substrate (14) is formed. Since the bonding strength of the bonding surface is increased, the semiconductor layer (11b) and the base substrate (1) in the semiconductor substrate to be manufactured are increased.
4) The bonding strength between them is increased, and the reliability can be further improved.

[0027] As in the method of manufacturing a semiconductor substrate according to claim 21 or 22, the heat treatment in the peeling step or the heat treatment in the heat treatment step may be performed by a lamp annealing apparatus or a laser irradiation annealing apparatus having a high temperature raising rate. When the apparatus is used, the throughput at the time of the heat treatment can be improved. The reason why such an annealing apparatus can be used is that a peeling phenomenon occurs instantaneously in the defect layer region.

[0028]

BEST MODE FOR CARRYING OUT THE INVENTION

(First Embodiment) Hereinafter, a first embodiment of the present invention will be described with reference to FIG. FIG. 1 is a schematic sectional view showing a manufacturing process of an SOI substrate. That is, in the protective film forming step shown in FIG. 1A, for example, a film is formed on a single-crystal silicon substrate 11 (corresponding to a semiconductor substrate material in the present invention) by thermal oxidation or a CVD method or a PVD method. The contamination protection film 12 made of a silicon oxide film having a uniform thickness is formed by the deposition method. The contamination protection film 12 is for preventing the single crystal silicon substrate 11 from being contaminated by heavy metals or the like in an ion implantation step described later, and the thickness thereof is preferably set to about 50 to 100 nm. You.

Thereafter, in the ion implantation step shown in FIG. 1B, hydrogen ions or rare gas ions are implanted into the single crystal silicon substrate 11 from the contamination protective film 12 side as indicated by arrows in the figure. Thereby, the ion-implanted layer 13 having a distribution parallel to the surface of the single-crystal silicon substrate 11 is formed. The dose in this ion implantation step is set to 1 × 10 ¹⁶ atoms / cm ² or more, preferably 5 × 10 ¹⁶ atoms / cm ² or more in the case of hydrogen ions. The ion implantation energy (acceleration voltage) is set according to the depth at which the ion implantation layer 13 is formed. It is conceivable to use various ions such as oxygen, chlorine, and fluorine in addition to the above-described hydrogen and the rare gas as the implanted ions.

In the protective film removing step shown in FIG. 1C, the contamination protective film 12 on the single crystal silicon substrate 11 is completely removed by, for example, chemical etching using a hydrofluoric acid aqueous solution. The removal of the contamination protective film 12 can be performed by mechanical polishing or dry etching.

On the other hand, in the insulating film forming step shown in FIG. 1D, the base substrate 14 made of, for example, a single crystal silicon substrate is used.
An insulating film 15 made of a silicon oxide film having a uniform thickness is formed thereon by a film formation by thermal oxidation or a deposition method such as a CVD method or a PVD method. Note that this insulating film 15
When the SOI structure is finally formed, it becomes a buried oxide film, and its film thickness is set to a value according to the design shape of the SOI substrate.

In the hydrophilization process shown in FIGS. 1E and 1F, the surface of the single-crystal silicon
In addition, the surface of the insulating film 15 on the base substrate 14 is subjected to a hydrophilic treatment. Specifically, in this hydrophilization treatment, for example, washing with a mixed solution of sulfuric acid and hydrogen peroxide solution (H2SO4: H2O2 = 4: 1) kept at about 90 to 120 DEG C. was performed for about 20 minutes. After that, washing with running water with pure water is performed 20 times.
For about a minute, the surface of the single crystal silicon substrate 11 on the ion implantation side and the insulating film 1 on the base substrate 14 side are formed.
This is achieved by forming the native oxide films 11a and 14a on the surface of No. 5, respectively.

Next, in the bonding step shown in FIG. 1 (g), the single-crystal silicon substrate 11 and the base substrate 14 are bonded to their hydrophilized surfaces (natural oxide films 11a and 11a).
Paste in a). This bonding is performed on each substrate 1
It is carried out by the adhesive action of hydrogen bonds between silanol groups and water molecules present on the hydrophilized surfaces 1 and 14.

Thereafter, in the peeling step shown in FIG.
By subjecting the single-crystal silicon substrate 11 and the base substrate 14 to an integrated heat treatment, the single-crystal silicon substrate 11 is separated from the defect layer region formed by the ion-implanted layer 13. Substrate 14
SOI in a form in which a single-crystal silicon thin film 11b (corresponding to a semiconductor layer in the present invention) is laminated thereon via an insulating film 15
A structure will be formed.

In this case, specifically, the ion implantation layer 13
Is formed by hydrogen ions,
Preferably, heat treatment is performed at about 400 to 600 ° C.
In response to such a heat treatment, microbubbles are aggregated to form macro bubbles in the defect layer region formed by the ion-implanted layer 13, and the bubble expands inside gas to make the defect layer region a boundary. Peeling will occur.

In order to achieve such a peeling phenomenon, it is necessary to set the bonding strength between the single crystal silicon substrate 11 and the base substrate 14 to a state that can withstand the stress caused by the internal gas expansion of the bubbles generated during the heat treatment. is there.

In general, in the bonding step of a silicon substrate, a bonding state is strengthened by performing a heat treatment after bonding at room temperature. Regarding the relationship between such bonding strength and heat treatment conditions, for example, Takao Abe et al., “Roles of hydrogen bonding in bonding silicon and quartz wafers”, SDM90-156 (1990 / IEICE), Takao Abe, et al .: “Silicon Wafer
Bonding Mechanism for Silicon-on-Insulator Structur
es ”: Japanese Journal of Appl. Phys. Vol. 29, No.
12, December, 1990, pp. L2311-L2314 and the like, it is known that a high-temperature and long-time heat treatment increases the bonding strength.

In FIG. 2, a large number of samples each made of an integrated body of the single crystal silicon substrate 11 and the base substrate 14 which have been bonded in accordance with the execution of the bonding step shown in FIG. After subjecting each of the plurality of samples to a heat treatment for 30 minutes in each state at different temperatures (for example, 150 ° C., 250 ° C., and 350 ° C.), the bonding strength between the substrates 11 and 14 is reduced. The results of actual measurements are shown. FIG. 2 shows that the bonding strength increases as the processing temperature increases.

In the single-crystal silicon substrate 11 and the base substrate 14 which have undergone the bonding step shown in FIG. 1G, the bonding between the substrates 11 and 14 can be strengthened by performing a heat treatment. In the peeling step (FIG. 1 (h)) performed after the step, a peeling phenomenon occurs in a temperature range of about 400 to 600 ° C. Such peeling phenomena are described, for example, in Xiang Lu, et. Al .: “Hydrogen i
nduced silicon surface layer cleavage ”: Appl. Ph
ys. Lett. 71 (13), 29 September (page 1804〜1806)
As shown in FIG. 2, it is considered that unbonded hydrogen segregated in the ion implantation layer 13 in the single crystal silicon substrate 11 is caused by the collected bubbles. That is, when the hydrogen gas in the bubbles expands by the heat treatment, a stress is generated in the ion implantation layer 13 in the single crystal silicon substrate 11, and the stress causes a separation phenomenon in the single crystal silicon substrate 11. .

In this case, the stress P (kgf / cm ² ) due to the hydrogen gas expansion as described above is given by the following relationship with the heat treatment temperature T (K) when applying a generally used ideal gas equation of state. It can be expressed by an expression.

P = R · nH · T / NA [kgf / cm ² ] (1) where R is a gas constant (84.7833 cm ³ · kgf / cm ² · mol ^−1).
K- ¹ ), nH: hydrogen concentration (atoms / cm ³ ), NA: Avogadro number (6.022045 × 10 ²³ mol ⁻¹ ).

On the other hand, the amount of implanted hydrogen ions necessary to cause the above-described separation phenomenon is experimentally found to be 3 to 4 × 10 ¹⁶ atoms / cm ² when the acceleration voltage is 80 KeV. Has been confirmed. Here, FIG. 3 shows the result of measuring the distribution of hydrogen implanted into silicon by SIMS (secondary ion mass spectrometry). The ion implantation amount (a) at which a stable peeling phenomenon occurs is 5 × 10 ¹⁶ at
There is a difference in hydrogen concentration at the peak position of the hydrogen distribution between the case of oms / cm ^{2 and} the case of the ion implantation amount (b) of about 3 × 10 ¹⁶ atoms / cm ² about the above threshold value. In other words, it can be seen from FIG. 3 that the separation phenomenon occurs when the hydrogen concentration at the peak position of the hydrogen distribution exceeds 2 to 3 × 10 ²¹ atoms / cm ³ .

In this case, the concentration difference at the peak position where the separation phenomenon is considered to occur is considered to be related to the formation of bubbles by the segregated hydrogen gas. That is, in the case of (b), the ion-implanted layer 1
No bubbles are formed in the defect layer formed by Step 3,
In the case of (a), it is considered that hydrogen which is excessively distributed as compared with (b) is involved in the formation of bubbles. In short, the hydrogen that causes the stress P represented by the above formula (1) is considered to be the concentration of hydrogen gas segregated in bubbles among hydrogen injected into silicon, and is 2 to 3 × 10 ²¹
A hydrogen concentration nH exceeding atoms / cm ³ will cause a peeling phenomenon.

FIG. 3 also shows the stress P calculated based on the equation (1). The ion implantation conditions at this time were as follows: an acceleration voltage of 80 KeV and a dose of 5 × 10
¹⁶ atoms / cm ² . Such a calculation result indicates that a stress of about 300 (kgf / cm ² ) or more is generated during the heat treatment at about 400 to 600 ° C. performed in the peeling step (see FIG. Is happening. Also, by changing the ion implantation conditions such as the acceleration voltage and the dose amount, the hydrogen concentration and the distribution state at the peak position of the hydrogen distribution also change, which is a threshold value of the hydrogen concentration necessary for causing the separation phenomenon. 2-3 × 10 ²¹ at
The difference with respect to oms / cm ³ also depends on the above-described implantation conditions, and the stress P generated accordingly changes.

Therefore, in order to establish a favorable peeling phenomenon in the peeling step, the bonding strength between the single crystal silicon substrate 11 and the base substrate 14 is reduced when the peeling phenomenon occurs due to the heat treatment in the peeling step. It is necessary to set the stress to be larger than the stress P due to internal gas expansion in the ion implantation layer 13. Therefore, in the present embodiment, the bonding strength between the single crystal silicon substrate 11 and the base substrate 14 is set to be larger than the stress generated by the internal gas expansion in the ion implantation layer 13 during the heat treatment in the separation step. ing.

Specifically, for example, prior to the heat treatment in the peeling step, the integrated body of the single crystal silicon substrate 11 and the base substrate 14 bonded in the bonding step
Under a low temperature at which the above-described peeling phenomenon does not occur (for example, FIG.
, A little over 300 ° C to 400 ° C, desirably 3
A heat treatment at a temperature of 50 to 400 ° C. is performed, for example, for about one hour to improve the bonding strength between the two, and thereafter, a high temperature (400 to 600 ° C.) heat treatment at which a peeling phenomenon occurs in the peeling step is performed. When such a heat treatment for improving the bonding strength is performed, the bonding strength between the single crystal silicon substrate 11 and the base substrate 14 illustrated in FIG.
In the temperature range of 00 to 600 ° C., the stress becomes larger than the stress P due to internal gas expansion in the ion implantation layer 13. Note that the heat treatment for improving the bonding strength and the heat treatment in the peeling step can be performed as a continuous heat treatment step using the same annealing apparatus. Further, in the heat treatment for improving the bonding strength, a method of gradually increasing the temperature to a target temperature set to less than 400 ° C. with the rate of temperature increase set to, for example, about 1 ° C./min. Can also be adopted.

However, the above heat treatment step for improving the bonding strength is not always necessary, and the bonding strength between the single crystal silicon substrate 11 and the base substrate 14 may be reduced depending on the conditions of the bonding surface. When the heat treatment is performed, the stress generated by the internal gas expansion in the ion-implanted layer 13 may be larger than that of the heat treatment. Therefore, in such a case, the heat treatment is unnecessary.

On the other hand, after the single-crystal silicon thin film 11b is separated from the single-crystal silicon substrate 11 by the above-described separation step, a heat treatment step is performed subsequently, although not specifically shown. In this heat treatment step, the insulating film 15 (embedded oxide film) on the base substrate 14 side and the single-crystal silicon thin film are subjected to heat treatment at a temperature higher than the heat treatment temperature in the peeling step (preferably about 1000 ° C. to 1200 ° C.) or higher. 11
The bonding strength of the bonding surface with b is strengthened.

The heat treatment in the above-mentioned stripping step and heat treatment step can be performed using a general electric furnace annealing apparatus. In this embodiment, a lamp annealing apparatus or a laser irradiation annealing apparatus is used. A short annealing time of several tens seconds to several minutes is performed by using an annealing apparatus having a high temperature rising rate. This is possible because the peeling phenomenon occurs instantaneously in the defect layer region.

The single-crystal silicon thin film 1 as described above
A defect layer formed by the ion implantation remains on the peeled surface 1b, and a minute step of about several nm to several tens nm is generated. For this reason, in this embodiment, the single-crystal silicon thin film 1 is mechanically polished on the peeled surface.
A flattening step (see FIG. 1 (i)) of removing a defect layer and a minute step on the substrate 1b is performed. According to the execution of such a flattening step, finally, FIG.
An insulating film 15 is formed on an SOI substrate 16 (corresponding to a semiconductor substrate in the present invention) as shown in FIG.
Through this, an SOI substrate 16 provided with a single-crystal silicon thin film 11b for element formation is completed.
However, the above-mentioned flattening step may be performed as needed.

On the other hand, the single-crystal silicon substrate 11 from which the single-crystal silicon thin film 11b has been stripped through the stripping step is used again for manufacturing another SOI substrate 16. Therefore, as shown in FIGS. 1 (j) and (k),
By performing a regeneration flattening step of mechanically polishing the separated surface of the single-crystal silicon substrate 11 to remove a defect layer and minute steps remaining on the separated surface, and using such a single-crystal silicon substrate 11 Then, steps after the above-described protective film forming step (see FIG. 1A) are performed.

According to the above-described embodiment, before the bonding step for bonding the single crystal silicon substrate 11 and the base substrate 14 is performed, in the protective film removing step, the surface of the single crystal silicon substrate 11 Since the contamination protection film 12 is removed, the flatness of the contamination protection film 12 is impaired or the contaminants are segregated near the surface of the contamination protection film 12 with the execution of the ion implantation process. Even in a situation where the single crystal silicon substrate 11 and the base substrate 14 remain, the bonding state between the single crystal silicon substrate 11 and the base substrate 14 can be made uniform over the entire bonding region.

As a result, the phenomenon that the single-crystal silicon thin film 11b is separated from the single-crystal silicon substrate 11 during execution of the separation step proceeds uniformly over the entire defect layer region formed by the ion-implanted layer 13. To become
As in the prior art, a phenomenon in which an expected peeling region on the single crystal silicon substrate 11 side, which should originally become the single crystal silicon thin film 11b on the base substrate 14, remains partially on the silicon substrate 11 side (FIG. 9) does not occur. Therefore, the quality of the SOI substrate 16 to be manufactured can be improved, and the yield can be improved.

In the present embodiment, in the hydrophilization treatment step performed before the bonding step, the surface of the single-crystal silicon substrate 11 on the ion implantation side and the insulating film 15 on the base substrate 14 side are formed. Natural oxide film 11a on the surface
And 14a will be formed respectively. Therefore, in the SOI substrate 16 manufactured through the bonding step, the peeling step, and the heat treatment step, the single-crystal silicon thin film 11b and the insulating film 15 have extremely small thicknesses (for example, at a molecular film level). Natural oxide films 11a and 14a
, The bonding strength between the single-crystal silicon thin film 11b and the insulating film 15 is increased, and the reliability of the SOI substrate 16 is improved.

Further, in the present embodiment, the bonding strength between the single crystal silicon substrate 11 and the base substrate 14 is larger than the stress generated by the internal gas expansion in the ion implantation layer 13 during the heat treatment in the peeling step. , A good peeling phenomenon can be expected in the peeling step.

According to the present embodiment, after the peeling step is performed, the heat treatment temperature (400 to 6) in the peeling step is used.
Higher than about 00 ° C) (preferably 1000 ° C to 120 ° C)
By performing a heat treatment of about 0 ° C.), the bonding strength of the bonding surface between the single crystal silicon thin film 11b and the insulating film 15 is increased, so that the finally obtained SO
The bonding strength between the single-crystal silicon thin film 11b and the insulating film 15 on the I-substrate 16 is increased, and the reliability thereof can be further improved.

Further, in each of the heat treatments in the peeling step and the heat treatment step, an annealing apparatus having a high temperature rising rate such as a lamp annealing apparatus or a laser irradiation annealing apparatus is used, so that the throughput in the heat treatment is improved. There is an advantage of gaining.

In this embodiment, when the SOI substrate 16 is manufactured, a product wafer whose impurity concentration is controlled to a constant value is used as the single crystal silicon substrate 11 in order to secure the quality of the single crystal silicon thin film 11b. On the other hand, it is sufficient that the base substrate 14 only has a function of holding the single-crystal silicon thin film 11b via the insulating film 15, so that a dummy wafer whose impurity concentration is not particularly controlled can be used. .

Therefore, an inexpensive base substrate 14 can be used, and the single-crystal silicon substrate 11 from which the single-crystal silicon thin film 11b has been peeled off through the peeling step is subjected to a flattening step for reproduction. By doing so, it can be reused when another SOI substrate 16 is manufactured, and effective use of resources can be achieved, so that the manufacturing cost can be reduced as a whole.

(Second Embodiment) FIG. 4 shows a second embodiment of the present invention. Only the portions different from the first embodiment will be described below. In addition, FIG.
FIG. 2 is a schematic cross-sectional view showing a manufacturing process of the SOI substrate, similarly to FIG. That is, in the present embodiment, the protective film forming step shown in FIG. 4A and the ion implantation step shown in FIG. 4B are performed by the protective film forming step (see FIG. 1A) in the first embodiment. This is performed in the same manner as in the ion implantation step (see FIG. 1B).

In the protective film removing step shown in FIG. 4C, only the upper surface of the contamination protective film 12 on the single crystal silicon substrate 11 is removed, so that the ion implantation step segregates near the surface of the contamination protective film 12. The contaminants remaining in the separated state are eliminated, and the contamination protection film 1 is formed on the single crystal silicon substrate 11.
2 'is left. In such a protective film removing step, chemical etching using a hydrofluoric acid aqueous solution or the like is generally used. In this embodiment, for example, a hydrofluoric acid aqueous solution (HF: H2O = 1: 50) is used. After performing chemical etching (1 minute treatment), the treated surface
By applying chemical mechanical polishing, the flatness is improved. Specifically, Ra (center line average surface roughness) is set to about 0.3 nm.

The insulating film forming step shown in FIG. 4D is replaced with the insulating film forming step in the first embodiment (see FIG. 1D).
4 (e) and 4 (f), in the hydrophilization treatment step shown in FIGS.
The surface of 2 'and the surface of the insulating film 15 on the side of the base substrate 14 are subjected to the same hydrophilic treatment as in the first embodiment to form natural oxide films 11a and 14a.

Thereafter, the bonding step shown in FIG. 4 (g) and the peeling step shown in FIG. 4 (h) correspond to the bonding step (see FIG. 1 (g)) and the peeling step (FIG. 1
(H), and the same heat treatment step as in the first embodiment. Prior to performing the above-described peeling step, heat treatment for increasing the bonding strength between the single crystal silicon substrate 11 and the base substrate 14 is also performed in the same manner as in the first embodiment. Further, the flattening step shown in FIG. 4I is replaced with the flattening step (FIG. 1I) in the first embodiment.
1), a single crystal silicon thin film 11 for element formation is formed on a base substrate 14 with an insulating film 15 interposed therebetween.
The SOI substrate 16 '(corresponding to the semiconductor substrate in the present invention) in the form provided with b is completed. Also, in the present embodiment, in order to reuse the single-crystal silicon substrate 11, a configuration is adopted in which a planarization step as shown in FIGS. 4J and 4K is performed in the same manner as in the first embodiment. .

According to the second embodiment, before the bonding step is performed, the upper surface portion of the contamination protective film 12 on the single crystal silicon substrate 11 is removed in the protective film removing step, so that the single crystal is removed. The flatness of the contamination protection film 12 'remaining on the silicon substrate 11 is ensured, and contaminants remaining in the vicinity of the surface in a segregated state are eliminated, so that the single crystal silicon substrate 11 and the base substrate 14 can be made uniform over the entire bonded region, and as a result, the SOI
The quality and yield of the substrate 16 are improved.
As in the first embodiment, the single-crystal silicon thin film 11b (actually, the contamination protection film 1)
2 ′) and the insulating strength between the insulating film 15 can be increased.

In the second embodiment, in the protective film removing step (see FIG. 4C), after performing chemical etching using a hydrofluoric acid aqueous solution, the treated surface is subjected to chemical mechanical polishing to be flattened. The reason why such a flattening process is performed is as follows.

That is, in the protective film removing step, the contamination protective film 12 on the single crystal silicon substrate 11 is only subjected to chemical etching (processing for 1 minute) using a hydrofluoric acid aqueous solution (HF: H 2 O = 1: 50). After that, in a hydrophilization treatment step, the temperature was kept at, for example, 90 ° C. (H 2 SO 4: H 2
O2 = 4: 1) Washing with a mixed solution (20 minutes) and washing with running pure water (20 minutes) are performed to remove the natural oxide film 1
When the lamination step of laminating the single crystal silicon substrate 11 and the base substrate 14 is performed as shown in FIG.
In some cases, a phenomenon that the size becomes relatively small may occur. Specifically, in the example of FIG. 5, the above-mentioned bonding strength is a stress due to internal gas expansion generated during a heat treatment at about 400 to 600 ° C. performed in the peeling step, that is, about 300 (kgf /
In this case, a bonding failure state which is significantly smaller than the stress of not less than cm ² ) is shown.

It is considered that such a phenomenon that the bonding failure occurs is because the flatness of the surface of the contamination protective film 12 is deteriorated before and after the chemical etching treatment with the hydrofluoric acid aqueous solution. Specifically, Ra (center line average surface roughness) before and after the above chemical etching treatment was measured by an AFM (atomic force microscope) in a region of 500 nm □.
= 0.3 nm was found to have deteriorated to about Ra = 0.6 nm. Further, it has been found that the flatness is not deteriorated by the hydrophilization treatment after the chemical etching. That is, since the vicinity of the surface of the contamination protective film 12 is damaged by the hydrogen ion implantation, a phenomenon occurs in which uneven etching progresses during the chemical etching treatment with the hydrofluoric acid aqueous solution. It is thought that it is getting worse. Therefore, in the present embodiment, in the protective film removing step, after performing chemical etching, the treated surface is subjected to chemical mechanical polishing to improve the flatness to Ra = about 0.3 nm. As a result of performing such a protective film removing step, in the subsequent bonding step, the bonding strength between the single crystal silicon substrate 11 and the base substrate 14 can be sufficiently increased, and thus, the stable bonding can be achieved in the subsequent peeling step. A peeling phenomenon will be obtained.

When the contamination centering on the heavy metal accompanying the execution of the ion implantation step is segregated in a narrow range on the outermost surface of the contamination protection film 12, the above protection film removal step is performed. Even if it does not exist, the subsequent hydrophilic treatment step (H
2 SO4 = 4: 1, 90-120 ° C, 20 minutes treatment: pure water washing for 20 minutes) to remove the contaminated portion, and in this case, the contaminated portion is removed. There is a situation that the flatness of the surface of the protective film 12 hardly deteriorates (Ra = 0.35 nm). When such flatness is obtained, the bonding strength between the single crystal silicon substrate 11 and the base substrate 14 can be sufficiently increased, and a stable separation phenomenon can be obtained in a subsequent separation step. Therefore, depending on the state of the surface of the contamination protective film 12, a configuration may be employed in which the protective film removing step is also performed by the chemical etching function of the hydrophilic treatment step.

(Third Embodiment) FIG. 6 shows a third embodiment of the present invention, and only the portions different from the first embodiment will be described below. That is, in the first embodiment, in the flattening step (see FIG. 1I) performed after the peeling step and the heat treatment step, the defect layer and the minute step on the single crystal silicon thin film 11b are removed by mechanical polishing. As described above, the present embodiment is characterized in that a flattening step for removing the defect layer and the minute step by etching is performed.

Specifically, in this embodiment, first, in the heat treatment step (see FIG. 6A) for increasing the bonding strength of the bonding surface between the single-crystal silicon thin film 11b and the insulating film 15, By performing thermal oxidation or nitriding on the surface of the crystalline silicon thin film 11b, a coating film 17 made of silicon oxide (semiconductor oxide) or silicon nitride (semiconductor nitride) is formed in advance. (See FIG. 6B). With the formation of such a coating film 17,
The defect layer and the surface step existing on the surface (peeled surface) of the single-crystal silicon thin film 11b are taken into the coating film 17.

Thereafter, a flattening step of removing the coating film 17 by chemical etching or dry etching is performed, whereby the single-crystal silicon thin film 11b is formed.
The surface defect layer and the surface step are removed, and the surface is planarized (see FIG. 6C). Further, thereafter, if necessary, the formation process and the etching process of the coating film 17 as described above are performed one or more times, so that the flatness of the surface of the single crystal silicon thin film 11b is greatly improved. be able to. Further, chemical mechanical polishing (CMP) may be performed after the etching process, and in this case, a required polishing thickness can be reduced. It should be noted that such a flattening step may be performed also in the second embodiment.

(Fourth Embodiment) FIG. 7 shows a fourth embodiment of the present invention. Only the portions different from the first embodiment will be described below. That is, in the first embodiment, in the flattening step (see FIGS. 1 (j) and 1 (k)) for recycling the single crystal silicon substrate 11, the defect layer and the minute step on the single crystal silicon substrate 11 are mechanically removed. Although removal is performed by polishing, the present embodiment is characterized in that a flattening step of removing the defect layer and the minute step by etching is performed.

More specifically, in this embodiment, the single-crystal silicon substrate 11 as shown in FIG. A coating film 18 made of a material (semiconductor oxide) or silicon nitride (semiconductor nitride) is formed in advance (see FIG. 7B). With the formation of such a coating film 18, the surface (peeled surface) of the single crystal silicon substrate 11.
The defect layer and the surface step present in the film 18 are taken into the coating film 18.

Thereafter, by performing a flattening step of removing the coating film 18 by chemical etching or dry etching, a defect layer and a surface step on the surface of the single crystal silicon substrate 11 are removed. Is flattened (see FIG. 7C). Furthermore, after this,
If necessary, the formation process and the etching process of the coating film 17 described above may be performed one or more times, or chemical mechanical polishing (CMP) may be performed.

(Other Embodiments) The present invention is not limited to the above-described embodiments, but can be modified or expanded as follows. As a semiconductor substrate material,
The semiconductor is not limited to a single-crystal silicon substrate, but may be any semiconductor mainly composed of a group 4 element, such as Ge (germanium) and SiC.
(Silicon carbide), SiGe (silicon germanium)
Alternatively, a substrate such as diamond can be used,
Further, a polycrystalline silicon substrate may be used.

The base substrate 14 is not limited to a single crystal silicon substrate, but may be another semiconductor substrate or a ceramic substrate or a glass substrate having an insulating property.
In this case, if the base substrate itself has an insulating property, it is not necessary to perform a step of separately forming the insulating film 15 on the base substrate.

In the hydrophilization treatment step, a natural oxide film is formed by sequentially performing washing with a mixed solution of sulfuric acid and hydrogen peroxide and running water with pure water.
For example, the surface to be hydrophilized (in the first embodiment, the surface of the single crystal silicon substrate 11 on the ion implantation side and the surface of the insulating film 15 on the base substrate 14 side; in the second embodiment, the contamination protection film 12 'And the insulating film 1 on the base substrate 14 side
After performing hydrofluoric acid treatment on the surface (surface No. 5), the surface of the surface to be hydrophilized may be subjected to a process of attaching a hydroxyl group by performing running water washing with pure water. Further, the heat treatment in the separation step and the heat treatment step may be performed as a series of annealing treatments.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view schematically showing an overall flow of a manufacturing process according to a first embodiment of the present invention.

FIG. 2 is a characteristic diagram showing a relationship between a heat treatment temperature, a bonding strength between substrates, and a stress caused by hydrogen gas expansion in the substrate.

FIG. 3 is a characteristic diagram showing a relationship between hydrogen ion implantation depth and hydrogen concentration.

FIG. 4 is a longitudinal sectional view schematically showing an entire flow of a manufacturing process according to a second embodiment of the present invention.

FIG. 5 is a characteristic diagram showing a relationship between a heat treatment temperature, a bonding strength between substrates, and a stress due to hydrogen gas expansion in the substrate.

FIG. 6 is a longitudinal sectional view schematically showing a main part of a manufacturing process according to a third embodiment of the present invention.

FIG. 7 is a longitudinal sectional view schematically showing a main part of a manufacturing process according to a fourth embodiment of the present invention.

FIG. 8 is a longitudinal sectional view schematically showing an example of a conventional manufacturing process.

FIG. 9 is a schematic longitudinal sectional view for explaining a phenomenon occurring in the manufacturing process.

[Explanation of symbols]

11 is a single crystal silicon substrate (semiconductor substrate material), 11a
Is a natural oxide film, 11b is a single crystal silicon thin film (semiconductor layer), 12 is a contamination protection film, 13 is an ion implantation layer, 14 is a base substrate, 14a is a natural oxide film, 15 is an insulating film,
6, 16 'indicate an SOI substrate (semiconductor substrate), and 17 indicates a coating film.

Claims (22)

[Claims] 1. A semiconductor substrate (16) comprising: a semiconductor layer (11b) for element formation provided on a base substrate (14) in a state of being electrically insulated from the base substrate (14); The surface on the ion implantation side of the semiconductor substrate material (11) in which the ion implantation layer (13) is formed at a predetermined depth on the base substrate (14) is bonded, and heat treatment is performed in this bonded state. In the semiconductor substrate (16) in which the semiconductor substrate material (11) is peeled at a defect layer region portion formed by the ion implantation layer (13) to form the semiconductor layer (11b), the semiconductor layer (11b) ) And the base substrate (14) are joined directly or via natural oxide films (11a, 14a). 2. The semiconductor substrate according to claim 1, wherein said base substrate is formed of a semiconductor material, and an insulating film is formed on an upper surface thereof. 3. A method of manufacturing a semiconductor substrate (16) comprising: forming a semiconductor layer (11b) for element formation on a base substrate (14) in a state of being electrically insulated from the base substrate (14). A protective film forming step of forming a contamination protective film (12) on a semiconductor substrate material (11) separately prepared from the base substrate (14); and the contamination protective film (1) for the semiconductor substrate material (11).
2) an ion implantation step of performing ion implantation from the side to form an ion implantation layer (13); and a protective film removing step of removing the contamination protective film (12) on the semiconductor substrate material (11) after the ion implantation. A hydrophilic treatment step of subjecting the surface of the semiconductor substrate material (11) on the ion-implanted side and the surface of the base substrate (14) to a hydrophilization treatment; and the semiconductor substrate material (11) and the base substrate (14). A bonding step of bonding on the hydrophilized surface, and a heat treatment, whereby the semiconductor substrate material (11)
Separating the semiconductor layer (11b) by stripping the semiconductor layer (11b) in a defect layer region formed by the ion-implanted layer (13). 4. The method for manufacturing a semiconductor substrate according to claim 3, wherein the bonding strength between the semiconductor substrate material (11) and the base substrate (14) is reduced when a peeling phenomenon occurs due to the heat treatment in the peeling step. A manufacturing method of the semiconductor substrate, wherein the stress is larger than a stress caused by internal gas expansion generated in the ion implantation layer (13). 5. The method of manufacturing a semiconductor substrate according to claim 3, wherein the semiconductor substrate material (11) and the base substrate (14) bonded in the bonding step prior to the heat treatment in the peeling step. The integrated with the above, heat treatment is performed at a low temperature at which the peeling phenomenon does not occur to improve the bonding strength between the two, and thereafter, a high temperature heat treatment at which the peeling phenomenon occurs in the peeling step is performed. Of manufacturing a semiconductor substrate. 6. The method for manufacturing a semiconductor substrate according to claim 3, wherein in the hydrophilizing step, the semiconductor substrate material is formed.
Surface of the ion-implanted side, and the base substrate (14)
A process for forming a natural oxide film (11a, 14a) on the surface of the semiconductor substrate. 7. The method for manufacturing a semiconductor substrate according to claim 3, wherein in the hydrophilizing step, the semiconductor substrate material is provided.
Surface of the ion-implanted side, and the base substrate (14)
A process for attaching a hydroxyl group to the surface of the semiconductor substrate. 8. A method of manufacturing a semiconductor substrate (16 ') comprising a semiconductor layer (11b) for element formation provided on a base substrate (14) in a state of being electrically insulated from the base substrate (14). A protective film forming step of forming a contamination protective film (12) on a semiconductor substrate material (11) prepared separately from the base substrate (14); 1
2) an ion implantation step of performing ion implantation from the side to form an ion implantation layer (13), and a protective film for removing an upper surface portion of the contamination protective film (12) on the semiconductor substrate material (11) after the ion implantation. A removing step; and the semiconductor substrate material (11) having undergone the protective film removing step.
A hydrophilic treatment step of subjecting the surface of the contamination protective film (12) and the surface of the base substrate (14) to a hydrophilic treatment, and applying the semiconductor substrate material (11) and the base substrate (14) to the hydrophilic treatment surface. The semiconductor substrate material (11)
Separating the semiconductor layer (11b) by stripping the semiconductor layer (11b) in a defect layer region formed by the ion-implanted layer (13). 9. The method for manufacturing a semiconductor substrate according to claim 8, wherein the bonding strength between the semiconductor substrate material (11) and the base substrate (14) is reduced when a peeling phenomenon occurs due to the heat treatment in the peeling step. A manufacturing method of the semiconductor substrate, wherein the stress is larger than a stress caused by internal gas expansion generated in the ion implantation layer (13). 10. The method for manufacturing a semiconductor substrate according to claim 8, wherein in the protective film removing step, chemical contamination or a combination of chemical etching and mechanical polishing is applied to the contamination protective film (12). A method for manufacturing a semiconductor substrate, comprising removing a contaminated region and flattening the surface. 11. The method for manufacturing a semiconductor substrate according to claim 8, wherein the semiconductor substrate material (11) and the base bonded in the bonding step prior to the heat treatment in the peeling step. The integrated body with the substrate (14) is subjected to a heat treatment at a low temperature at which the peeling phenomenon does not occur to improve the bonding strength between the two, and thereafter, a high-temperature heat treatment at which the peeling phenomenon occurs in the peeling step is performed. A method for manufacturing a semiconductor substrate, comprising: 12. The method for manufacturing a semiconductor substrate according to claim 8, wherein in the hydrophilization treatment step, the contamination protection film (12) of the semiconductor substrate material (11) having undergone the protection film removal step. ) And a process of forming a natural oxide film (11a, 14a) on the surface of the base substrate (14). 13. The method for manufacturing a semiconductor substrate according to claim 8, wherein in the hydrophilization treatment step, the contamination protection film (12) of the semiconductor substrate material (11) having undergone the protection film removal step. A) a process of attaching a hydroxyl group to the surface of the base substrate (14) and the surface of the base substrate (14). 14. The method of manufacturing a semiconductor substrate according to claim 3, wherein a semiconductor material is used as a material of the base substrate, and the base substrate is formed prior to the hydrophilization process. (1
4) A method of manufacturing a semiconductor substrate, comprising performing an insulating film forming step of forming an insulating film (15) thereon. 15. The method for manufacturing a semiconductor substrate according to claim 3, wherein a heat treatment at a temperature higher than a heat treatment temperature in the separation step is performed after the separation step is performed. A method of manufacturing a semiconductor substrate, comprising: performing a heat treatment step of increasing a bonding strength of a bonding surface between (11) and a base substrate (14). 16. The method for manufacturing a semiconductor substrate according to claim 3, wherein a flattening step for removing a surface step on a peeled surface of the semiconductor layer (11b) is performed after the peeling step is performed. A method for manufacturing a semiconductor substrate, comprising: 17. The method for manufacturing a semiconductor substrate according to claim 15, wherein a flattening step for removing a surface step on a peeled surface of the semiconductor layer is performed after the heat treatment step. Manufacturing method. 18. The method of manufacturing a semiconductor substrate according to claim 16, wherein in the flattening step, a peeled surface of the semiconductor layer (11b) is chemically and mechanically polished. Method. 19. The method for manufacturing a semiconductor substrate according to claim 16, wherein a coating film made of a semiconductor compound is formed in advance on a surface of said semiconductor layer, and in said flattening step, A method of manufacturing a semiconductor substrate, comprising: removing a surface step on a peeled surface of a semiconductor layer (11b) by etching the coating film (17). 20. The method for manufacturing a semiconductor substrate according to claim 17, wherein a semiconductor oxide or a semiconductor nitride is formed on the surface of the semiconductor layer (11b) during the heat treatment step. 17) forming the semiconductor substrate in advance, and in the flattening step, removing the surface step on the peeled surface of the semiconductor layer (11b) by etching the coating film (17). Method. 21. The method for manufacturing a semiconductor substrate according to claim 3, wherein an annealing apparatus having a high temperature raising rate such as a lamp annealing apparatus or a laser irradiation annealing apparatus is used for the heat treatment in the peeling step. A method of manufacturing a semiconductor substrate. 22. The method for manufacturing a semiconductor substrate according to claim 15, wherein the heat treatment in the heat treatment step has a high temperature rising rate such as a lamp annealing apparatus or a laser irradiation annealing apparatus. A method of manufacturing a semiconductor substrate, characterized by utilizing the following.