JP2007311672A - Method of manufacturing soi substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing an SOI substrate with excellent electric characteristics wherein a defect density caused in an SOI layer is low, even after a device manufacturing process. <P>SOLUTION: In the manufacturing method of the SOI substrate before heat treatment is applied to a bond wafer at least at first, heat treatment is applied for marking internal defect to a single crystal silicon substrate manufactured from a single crystal silicon ingot to select a single crystal silicon ingot whose internal defect density is 1&times;10<SP>8</SP>/cm<SP>3</SP>or below by inspecting the internal defect density of the single crystal silicon ingots, and the SOI substrate is manufactured by using the single crystal silicon substrate manufactured from the selected single crystal silicon ingot for the bond wafer. <P>COPYRIGHT: (C)2008,JPO&amp;INPIT

Description

  The present invention relates to a method for manufacturing an SOI (Silicon On Insulator) substrate by a bonding method, and more particularly, to a method for manufacturing an SOI substrate having a low density of internal defects generated in an SOI layer.

  As one of semiconductor device substrates, there is an SOI (Silicon On Insulator) substrate in which a silicon layer (hereinafter also referred to as an SOI layer) is formed on a silicon oxide film that is an insulating film. This SOI substrate has a small parasitic capacitance and high radiation resistance because the SOI layer on the surface layer of the substrate, which is a device manufacturing region, is electrically separated from the inside of the substrate by a buried oxide film layer (BOX layer). Has characteristics. Therefore, effects such as high-speed and low-power consumption operation and prevention of soft errors are expected, and it is promising as a substrate for high-performance semiconductor elements.

  As a method for manufacturing this SOI substrate, for example, a bonding method as shown below is known. That is, two mirror-polished single crystal silicon substrates (a single crystal silicon substrate (bond wafer) serving as an SOI layer and a single crystal silicon substrate (base wafer) serving as a support substrate) are prepared, and at least one single crystal silicon is prepared. An oxide film is formed on the surface of the substrate. Then, after bonding these single crystal silicon substrates through an oxide film, heat treatment is performed to increase the bond strength. Thereafter, the bond wafer is thinned to obtain an SOI substrate on which an SOI layer is formed. As a method of thinning the film, there are a method of grinding and polishing the bond wafer to a desired thickness, a method of peeling the bond wafer with an ion implantation layer by a method called an ion implantation separation method, and the like.

Usually, a single crystal silicon substrate manufactured from a single crystal silicon ingot grown by the Czochralski (CZ) method is used for a bond wafer and a base wafer which are raw materials for an SOI substrate. In the silicon single crystal grown by the CZ method, interstitial oxygen is contained as an impurity at a concentration of about 10 ¹⁸ atoms / cm ³ . Due to the presence of interstitial oxygen, it is supersaturated in the heat history from the solidification during the crystal growth process until it is cooled to room temperature (hereinafter abbreviated as crystal heat history) and the heat treatment process in the semiconductor element manufacturing process. In order to be in a state, it precipitates to form silicon oxide precipitates (hereinafter sometimes referred to as oxygen precipitates or simply precipitates).

  The process of oxygen precipitation includes a process of forming a precipitation nucleus and a process of growing the precipitation nucleus. Usually, the formation of precipitation nuclei progresses in the crystal thermal history, and it grows greatly by a heat treatment such as a subsequent device process, and is detected as an oxygen precipitate. Therefore, what is formed by the crystal thermal history is referred to as a grown-in precipitation nucleus (crystal growth introduction precipitation nucleus). Of course, precipitation nuclei may be formed in the subsequent heat treatment.

  The presence of oxygen precipitates in the device fabrication region near the wafer surface degrades the electrical characteristics of the device. Therefore, it is desirable that the defect density of the device manufacturing region is as low as possible.

  When an SOI substrate having an SOI layer thickness of about 1 μm or more (hereinafter sometimes referred to as a thick film SOI substrate) is manufactured by a bonding method, a silicon oxide film is formed on at least one surface of a bond wafer and a base wafer. After producing and bonding a bond wafer and a base wafer through the silicon oxide film, it heat-processes and raises bond strength. Thereafter, the bond wafer is ground and polished to a desired thickness to obtain a thick film SOI substrate. In such an SOI substrate manufacturing method, for example, when a silicon oxide film is formed on the surface of a bond wafer, the bond wafer is subjected to at least two heat treatments for forming the oxide film and heat treatment for increasing the bond strength. This heat treatment is performed.

  In such a case, the bond wafer is subjected to a heat treatment before it is thinned, so that oxygen precipitation proceeds during the heat treatment, and oxygen precipitates, dislocations and stacking faults, and the like may be generated. . In such a case, there is a problem that oxygen precipitates are exposed on the surface of the SOI layer by reducing the film thickness thereafter, and the electrical characteristics of the SOI layer are deteriorated. Further, even when a defect does not become apparent in the manufacturing process of the SOI substrate, it may become apparent in the subsequent device manufacturing process, and the electrical characteristics of the SOI layer may be deteriorated.

  In order to solve such a problem, Patent Document 1 discloses that a silicon oxide film is formed on the surface of a bond wafer having an interstitial oxygen concentration of 16 ppma or less by thermal oxidation, and is bonded to the base wafer through the oxide film. A method is disclosed. With such an SOI substrate manufacturing method, the interstitial oxygen concentration is 16 ppma or less, so that oxygen precipitation is suppressed, and generation of OSF (Oxidation Induced Stacking Fault), which is a stacking fault due to the oxygen precipitation, is suppressed. ing. In addition, since the thermal oxide film of the bond wafer is formed immediately after the cleaning of the silicon wafer, it has an effect of protecting the bond wafer from external contamination, which also suppresses the generation of crystal defects. In addition, it has been speculated that the generation of crystal defects is suppressed by reducing the interstitial oxygen concentration on the SOI layer surface by thermal oxidation before bonding.

  However, even when a single crystal silicon substrate having an interstitial oxygen concentration of 16 ppma or less is used for the bond wafer, oxygen precipitation may proceed in the SOI layer even if OSF is not generated. Has occurred, thereby deteriorating the electrical characteristics of the SOI layer.

Japanese Patent Laid-Open No. 7-263651

  Therefore, the present invention has been made in view of such problems, and provides a method for manufacturing an SOI substrate having a low density of defects generated in an SOI layer even after a device manufacturing process and having excellent electrical characteristics. Objective.

The present invention has been made to solve the above-described problems, and at least a step of producing a single crystal silicon substrate from a single crystal silicon ingot to form a bond wafer and a base wafer, and at least the bond wafer and the base wafer. An SOI substrate comprising: a step of forming a silicon oxide film on one surface; a step of bonding the bond wafer and the base wafer through the silicon oxide film; and a step of thinning the bonded bond wafer In the manufacturing method, at least before the heat treatment is first applied to the bond wafer, a single crystal silicon substrate manufactured from the single crystal silicon ingot is subjected to an internal defect revealing heat treatment to inspect the internal defect density of the single crystal silicon substrate. By doing so, the internal defect density is 1 × 10 ⁸ pieces / cm ^3. A method for manufacturing an SOI substrate, comprising: selecting a single crystal silicon ingot, and manufacturing an SOI substrate using the single crystal silicon substrate manufactured from the selected single crystal silicon ingot as the bond wafer. (Claim 1).

In this way, the internal defect density is inspected in advance, and an SOI substrate is manufactured using a single crystal silicon substrate manufactured from a single crystal silicon ingot having an internal defect density of 1 × 10 ⁸ pieces / cm ³ or less as a bond wafer. For example, an SOI substrate having a low density of oxygen precipitates generated in the SOI layer in the SOI manufacturing process or device manufacturing process can be manufactured. In addition, before manufacturing the SOI substrate, a single crystal silicon substrate which is not suitable for use as a bond wafer can be excluded.

  In this case, the internal defect revealing heat treatment is performed at a temperature of a heat treatment that the bond wafer first receives in the manufacturing process of the SOI substrate, or less than a temperature of a heat treatment that the bond wafer first receives in the manufacturing process of the SOI substrate and Heat treatment is preferably performed at 800 ° C. or higher (claim 2).

  As described above, in the internal defect revealing heat treatment, the bond wafer is first subjected to the heat treatment temperature in the SOI substrate manufacturing process, or the bond wafer is first subjected to the heat treatment temperature received in the SOI substrate manufacturing process and 800 ° C. or higher. If the oxygen precipitates are revealed by heat treatment, at least the density of oxygen precipitates generated in the manufacturing process of the SOI substrate can be estimated more accurately.

  The inspection of the internal defect density is preferably performed at a depth of 3 μm or more from the surface of the single crystal silicon substrate to be inspected.

  As described above, the inspection of the internal defect density can be performed more accurately by measuring the density of oxygen precipitates generated in the manufacturing process of the SOI substrate by measuring at a depth of 3 μm or more from the surface of the single crystal silicon substrate for inspecting the internal defect density. Can be estimated.

  Further, the thickness of the SOI layer of the manufactured SOI substrate can be 3 μm or more.

  Even when an SOI substrate having a thickness of 3 μm or more is manufactured, an SOI substrate having a low density of oxygen precipitates generated in the SOI layer in the SOI manufacturing process or device manufacturing process is manufactured. Can do.

  With the method for manufacturing an SOI substrate according to the present invention, an SOI substrate having a low density of defects generated in the SOI layer in the SOI manufacturing process or device manufacturing process can be manufactured. Such an SOI substrate can be an SOI substrate having excellent electrical characteristics.

Hereinafter, the present invention will be described more specifically.
As described above, a single crystal silicon substrate having a low interstitial oxygen concentration such that the interstitial oxygen concentration is 16 ppma (JEIDA standard, JEIDA is the current JEITA (Japan Electronics and Information Technology Industries Association)) or less is applied to the bond wafer. Even if it is used, oxygen precipitation may progress in the SOI substrate manufacturing process and device manufacturing process, and various defects are generated accordingly, which may deteriorate the electrical characteristics of the SOI layer. was there.

  As a result of intensive studies based on experiments and the like regarding the reason why oxygen precipitation proceeds even when the interstitial oxygen concentration of the bond wafer is sufficiently low, the present inventors have determined that oxygen in the SOI manufacturing process and the device manufacturing process. It has been found that the easiness of the precipitation is not determined only by the interstitial oxygen concentration of the bond wafer, but also depends on the crystal thermal history described above. That is, it has been found that it is not sufficient to specify the interstitial oxygen concentration in order to reduce oxygen precipitation.

Based on this knowledge, the present inventors further optimized various conditions through experiments, and the initial heat treatment simply reduced the internal defect density (Bulk Micro Defect; BMD) to 1 × 10 ⁸ pieces / cm ³ or less. It has been found that if a crystalline silicon substrate is used for a bond wafer, oxygen precipitation in the SOI layer can be sufficiently reduced, and the present invention has been completed.

Hereinafter, the present invention will be described more specifically with reference to the drawings, but the present invention is not limited thereto.
FIG. 1 is a flowchart showing an example of a method for manufacturing an SOI substrate by the bonding method of the present invention. The outline of the manufacturing method of the SOI substrate by the bonding method to which the present invention is applied is as follows.

  First, in the step (a), a single crystal silicon ingot 10 is prepared. As described above, a single crystal silicon substrate used for manufacturing an SOI substrate is usually manufactured from a single crystal silicon ingot grown by a CZ method, but the present invention is limited to this. Instead, a single crystal silicon ingot manufactured by any manufacturing method such as the FZ method may be prepared.

Next, in the step (b), an inspection wafer 11 for measuring the internal defect density is produced from a single crystal silicon ingot to be used as a bond wafer. The inspection wafer 11 does not need to be mirror-polished like a normal bond wafer, and may be in a state of being chemically etched after being ground after cutting, for example.
In addition, you may perform the process of normally producing several bond wafers of the process (d) before this inspection wafer preparation process. That is, the inspection wafer 11 and the bond wafer 12 do not need to be clearly distinguished, and the next step (c) may be performed using the single crystal silicon substrate manufactured as the bond wafer as the inspection wafer.

  Next, at least before the bond wafer 12 undergoes a heat treatment for the first time in the manufacturing process of the SOI substrate, an internal defect revealing heat treatment is applied to the inspection wafer 11 to measure the internal defect density (step (c)). . The temperature of this internal defect clarification heat treatment is equal to or lower than the temperature of the heat treatment first received by the bond wafer in the manufacturing process of the SOI substrate, or 800 ° C. or higher. Is preferred.

  Note that the “heat treatment” here refers to a case where the temperature is raised to a temperature at which defects are generated in the single crystal silicon substrate, and specifically, the temperature is 400 ° C. or more, for example. Refers to a case. That is, “the temperature of the heat treatment that the bond wafer first receives in the manufacturing process of the SOI substrate” means, for example, that a silicon oxide film to be a BOX layer is formed on the bond wafer surface in a silicon oxide film forming step (e) described later. In this case, the oxidation temperature is about 900 ° C., for example. Further, when the silicon oxide film to be the BOX layer is formed only on the surface of the base wafer, the heat treatment that the bond wafer receives at the beginning of the SOI manufacturing process is the bonding heat treatment in the step (g) described later, and the temperature is, for example, 1100 ° Degree. In addition, if there is a step of diffusing impurities, there are various cases such as the temperature of the diffusion heat treatment. In the case of a CZ wafer, a donor killer heat treatment (about 650 ° C.) for eliminating the influence of oxygen donors is performed when a bond wafer is produced from the single crystal silicon ingot 10. Is not included.

  Further, if the temperature of the internal defect revealing heat treatment is too low, it takes time to grow the grown-in precipitation nuclei in the inspection wafer. Therefore, in order to perform the heat treatment more efficiently, the internal defect revealing heat treatment is performed. The temperature is preferably 800 ° C. or higher.

The oxygen precipitation of the bond wafer is that the grown-in precipitation nuclei that remain stable at the heat treatment temperature received at the beginning of the SOI manufacturing process remain in the grown-in precipitation nuclei included in the bond wafer and grow in the subsequent heat treatment process. To proceed. Therefore, by performing heat treatment below the temperature of the heat treatment received at the beginning of the SOI manufacturing process, if grown-in precipitation nuclei are grown and manifested and measured as oxygen precipitates having a detectable size, at least the manufacture of an SOI substrate is possible. It can be estimated as the density of oxygen precipitates generated in the process.
Oxygen precipitation in the device manufacturing process proceeds mainly due to growth of oxygen precipitates generated in the SOI substrate manufacturing process. Therefore, if the density of oxygen precipitates generated in the SOI substrate manufacturing process is low, device manufacturing is performed. Since the density of oxygen precipitates grown in the process is also reduced, it is only necessary to consider the influence of the heat treatment in the SOI substrate manufacturing process.

  Further, when the “temperature of the heat treatment that the bond wafer first receives in the manufacturing process of the SOI substrate”, which is adopted as the internal defect revealing heat treatment, is lower than 1000 ° C., the internal defect revealing heat treatment is performed only at that temperature. Since it takes time to grow to a detectable size, “the temperature of the heat treatment that the bond wafer first receives in the manufacturing process of the SOI substrate” or “the temperature of the heat treatment that the bond wafer first receives in the manufacturing process of the SOI substrate” It is preferable that after the heat treatment is performed at 800 ° C. or higher for several hours, the heat treatment is performed at a temperature of 1000 ° C. or higher for several hours to efficiently grow to a detectable size.

  The method of measuring the internal defect density of the heat-treated inspection wafer 11 is not limited. For example, after selectively etching a cleaved section or an angle-polished surface, it is observed with an optical microscope, and an etch pit caused by a defect. By counting the number, the internal defect density can be measured. Alternatively, it can be measured by an infrared scattering method. At that time, the position where the defect density is measured is preferably a position deeper than the surface by 3 μm or more. This is because if the measurement is performed at such a deep position, the internal defect density can be estimated more accurately with almost no influence by the drastic change in the defect density due to the out-diffusion of interstitial oxygen.

If the measured internal defect density is 1 × 10 ⁸ pieces / cm ³ or less, the single crystal silicon ingot 10 on which the inspection wafer 11 is manufactured is accepted as a bond wafer and manufactured from the single crystal silicon ingot. The single crystal silicon substrate 12 is used as a bond wafer.
On the other hand, when it is higher than 1 × 10 ⁸ pieces / cm ³ , it is rejected, and a single crystal silicon substrate manufactured from the same single crystal silicon ingot as the inspection wafer is not used as a bond wafer. Such a single crystal silicon substrate cannot be used as a bond wafer used for manufacturing an SOI substrate according to the present invention, but it can be used for other purposes as a matter of course and is not wasted. For example, it can be used as a base wafer.
The reason why the acceptance criterion for use as a bond wafer is set to an internal defect density of 1 × 10 ⁸ pieces / cm ³ will be described later.

  In the subsequent steps (d) to (h), an SOI substrate is manufactured by a normal method using a single crystal silicon substrate manufactured from the single crystal silicon ingot passed in the above step (c) as a bond wafer. . An example is described below.

First, in the step (d), the bond wafer 12 is manufactured from the single crystal silicon ingot passed in the step (c), and the base wafer 13 is prepared. The base wafer 13 prepared here may be manufactured from a single crystal silicon ingot for manufacturing the bond wafer 12, but 1 × 10 ⁸ from the viewpoint of gettering ability, mechanical strength, and the like. It may be manufactured from another single crystal silicon ingot having an internal defect density higher than / cm ³ .

  As described above, this step (d) may be performed before step (b). That is, the inspection wafer 11 is manufactured, the internal defect density thereof is inspected, and a single crystal silicon substrate as a bond wafer may be manufactured from the single crystal silicon ingot. Alternatively, a single crystal silicon substrate may be used. May be prepared, and at least one of them may be used as the inspection wafer 11 to inspect the internal defect density in the step (c) described above. If it passes the inspection, it is used as a bond wafer, and even if it fails, it may be used for other purposes as described above.

Next, in step (e), a silicon oxide film 14 to be a BOX layer is formed on the surface of at least one of the bond wafer 12 and the base wafer 13. FIG. 1 shows an example in which a silicon oxide film 14 is formed on the surface of the base wafer 13.
The formation of the silicon oxide film 14 in this step is preferable because a thermal oxidation method can easily form a dense and high-quality silicon oxide film, but is not limited to this method.

  In this process, when the silicon oxide film 14 is formed on the bond wafer 12 and this process is the first heat treatment that the bond wafer 12 receives, as described above, “the bond wafer is in the SOI substrate manufacturing process. The “first heat treatment temperature” is the heat treatment temperature when the silicon oxide film 14 is formed.

  Next, in the step (f), the base wafer 13 on which the bond wafer 12 and the silicon oxide film 14 are formed is adhered and bonded through the silicon oxide film 13. In this way, a bonded wafer 15 is obtained.

Next, in the step (g), bonding heat treatment for increasing the bonding strength is performed. In this bonding heat treatment, for example, two wafers are firmly bonded by performing a heat treatment in an oxidizing or inert gas atmosphere. The temperature of this bonding heat treatment may be 1000 ° C. or higher and lower than the melting point of silicon, and the heat treatment time may be, for example, 1 hour or more and 4 hours or less, but is not limited thereto.
As described above, the temperature of this bonding heat treatment may be “the temperature of the heat treatment that the bond wafer first receives in the manufacturing process of the SOI substrate”.

  Next, in step (h), the SOI layer is thinned to a desired thickness to obtain an SOI substrate 18 having the SOI layer 16 and the buried oxide film (BOX layer) 17. For thinning at this time, for example, a method by surface grinding and mirror polishing can be used.

For thinning the bond wafer, it is preferable to use, for example, a method by surface grinding and mirror polishing or a method by etching suitable for forming a relatively thick SOI layer.
In particular, as described below, the present invention is particularly suitable when the thickness of the SOI layer of the finally manufactured SOI substrate is set to 3 μm or more. The bond wafer is thinned by grinding and polishing.

  As described above, the present invention is particularly suitable when the thickness of the SOI layer of the finally manufactured SOI substrate is 3 μm or more. This is due to the following reasons. Also in the heat treatment in the SOI manufacturing process, on the surface side of the bond wafer, oxygen diffuses outward during the heat treatment, so that the grown-in nuclei are difficult to grow and may disappear. The same applies to the surface (bonded surface side) of the bond wafer during the bonding heat treatment after bonding. Therefore, when the SOI layer of the finally manufactured SOI substrate is thinner than 3 μm, the possibility of oxygen precipitation in the SOI layer is reduced.

On the other hand, even when manufacturing an SOI substrate having an SOI layer thickness of 3 μm or more, a single crystal silicon ingot having an internal defect density of 1 × 10 ⁸ pieces / cm ³ or less is selected as in the present invention. If the SOI substrate is manufactured, an SOI substrate having a low defect density generated in the SOI layer in the SOI manufacturing process or device manufacturing process can be manufactured.

Of course, the present invention may be applied when the thickness of the SOI layer of the finally manufactured SOI substrate is thinner than 3 μm.
When such a relatively thin SOI layer is used, the thinning step of step (h) includes a bond wafer suitable for forming a relatively thin SOI layer in addition to the above-described grinding and polishing methods. Before the step (f) for bonding the base wafer, a peeling ion layer is formed by implanting hydrogen ions or helium ions in advance from the bonding surface side of the bond wafer, and after the bonding, the peeling ion implantation is performed. A method called an ion implantation separation method in which a thin film is formed by peeling a bond wafer with a layer can also be used. In addition, when thinning by ion implantation peeling method, after bonding at room temperature, after performing peeling by performing low temperature heat treatment at about 500 ° C. if necessary, bonding heat treatment step for increasing the bonding strength (G) is performed in the order of steps.

  Through the steps as described above, an SOI substrate having a low density of oxygen precipitates generated in the SOI layer in the SOI manufacturing process or device manufacturing process can be manufactured.

In addition to the above steps, various processes that can be performed in manufacturing the SOI substrate may be added. For example, before the bonding step (f), ion implantation can be performed on the bonding surface in order to form a high-concentration ion diffusion layer for the purpose of adding gettering capability and the convenience of device fabrication.
If the additional treatment is a heat treatment and the heat treatment is the first heat treatment applied to the bond wafer 12, as described above, “the bond wafer is first subjected to the manufacturing process of the SOI substrate. The heat treatment temperature of the added treatment is adopted as the “heat treatment temperature”.

Next, the reason why the internal defect density is set to 1 × 10 ⁸ pieces / cm ³ as the acceptance criterion for use as a bond wafer in the step (c) will be described below.
The present inventors consider that the electrical characteristics of the finally manufactured SOI substrate will be affected by oxygen precipitates that are potentially present inside the bond wafer that will be the SOI layer. Experiments were conducted.
(Experimental example)
An experimental example will be described with reference to FIG.

  First, six single crystal silicon ingots having different oxygen concentrations and crystal positions were prepared using a single crystal silicon ingot having a diameter of 200 mm and a plane orientation {100} grown by the CZ method (a). An inspection wafer 11 was prepared from each ingot (b). In addition, a single crystal silicon substrate 12 serving as an SOI layer was also prepared from the same ingot (d). Moreover, the single crystal silicon substrate 13 used as a support substrate was prepared from another single crystal silicon ingot (d).

  The inspection wafer 11 was subjected to heat treatment for 16 hours at 1000 ° C., which is 800 ° C. or higher, which is not higher than the heat treatment temperature that the bond wafer first receives in the manufacturing process of the SOI substrate in this experimental example. Thereafter, the internal defect density of the heat-treated inspection wafer was measured by an infrared scattering tomography method (hereinafter sometimes referred to as LST) which is one of infrared scattering methods (c). The density measurement position was set to a depth in the range of 40 μm to 200 μm.

On the other hand, a silicon oxide film 14 having a thickness of about 1 μm to be a BOX layer was formed on the surface of the single crystal silicon substrate 13 to be a support substrate by thermal oxidation (e).
Thereafter, the single crystal silicon substrate 12 serving as the SOI layer and the single crystal silicon substrate 13 serving as the support substrate were adhered to each other with the silicon oxide film 14 interposed therebetween (f).
Next, bonding heat treatment for increasing the bonding strength was performed (g). The temperature of the bonding heat treatment was 1150 ° C. Thereafter, the active layer side of the bonded wafer 15 was thinned to a thickness of about 14 μm by surface grinding or mirror polishing to obtain an SOI substrate 18 (h).

With respect to the SOI substrate manufactured as described above, the oxide film breakdown voltage characteristic (TDDB (Time Dependent Dielectric Breakdown) non-defective rate) was measured. This TDDB is for observing leakage and dielectric breakdown that occur in a certain length of time even when a relatively low voltage that does not cause instantaneous dielectric breakdown is applied.
In measuring the TDDB non-defective rate, a thermal oxide film having a film thickness of about 25 nm was formed on the surface of the SOI substrate 18 on the SOI layer 16 side, and a phosphorus-added polysilicon electrode (electrode area: 4 mm ² ) was formed thereon. Then, the non-defective product rate was calculated by measuring 100 points in the wafer surface with a dielectric breakdown charge amount of 10 C / cm ² or more as a good product.

The relationship between the internal defect density of the inspection wafer and the TDDB non-defective rate of the SOI substrate is shown in FIG. From this result, it can be seen that if the internal defect density of the inspection wafer is 1 × 10 ⁸ pieces / cm ³ or less, the TDDB characteristics are good.
That is, if a single crystal silicon substrate manufactured from a single crystal silicon ingot having an internal defect density of an inspection wafer of 1 × 10 ⁸ pieces / cm ³ or less is used as a bond wafer, generation of defects in the SOI layer is suppressed. An SOI substrate can be manufactured.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples of the present invention, but the present invention is not limited thereto.

(Example 1, Comparative Example 1)
Based on the process shown in FIG. 1, an SOI substrate was manufactured as follows.
First, four ingots having a diameter of 200 mm and a plane orientation {100} having different oxygen concentrations and crystal positions were prepared (a), and inspection wafers were prepared from each ingot (b).
The inspection wafer was subjected to a heat treatment for 16 hours at 1000 ° C., which is 800 ° C. or higher and lower than the heat treatment temperature that the bond wafer first receives in the manufacturing process of the SOI substrate. Thereafter, the internal defect density of the heat-treated inspection wafer was measured by LST (c). The density measurement position was set to a depth in the range of 40 μm to 200 μm.
Based on the measurement result of the internal defect density, the ingot whose internal defect density was 8 × 10 ⁶ pieces / cm ³ (Example 1) and the ingot which was 7 × 10 ⁸ pieces / cm ³ (Comparative Example 1). From this, a single crystal silicon substrate was prepared and prepared as a bond wafer (d). Next, after manufacturing a base wafer from another single crystal silicon ingot (d), an SOI substrate was prepared in the same manner as in the experimental example (eh), and TDDB characteristics were measured.

As a result, the TDDB non-defective rate of the SOI substrate in which the internal defect density of the inspection wafer was 8 × 10 ⁶ pieces / cm ³ (Example 1) was as good as 95%. On the other hand, the TDDB non-defective rate of the SOI substrate in which the internal defect density of the inspection wafer was 7 × 10 ⁸ pieces / cm ³ (Comparative Example 1) was 83%, and the electrical characteristics were deteriorated.
As described above, according to the present invention, it has been shown that an SOI substrate having excellent electrical characteristics can be manufactured.

  The present invention is not limited to the above embodiment. The above embodiment is merely an example, and the present invention has the same configuration as that of the technical idea described in the claims of the present invention, and any device that exhibits the same function and effect is the present invention. It is included in the technical scope of the invention.

It is the flowchart which showed the outline of the manufacturing method of the SOI substrate by the bonding method of this invention. It is the graph which plotted the relationship between an internal defect density and a TDDB non-defective rate.

Explanation of symbols

10 ... single crystal silicon ingot, 11 ... wafer for inspection,
12 ... single crystal silicon substrate (bond wafer),
13 ... single crystal silicon substrate (base wafer), 14 ... silicon oxide film,
15 ... bonded wafer, 16 ... SOI layer, 17 ... buried oxide film,
18 ... SOI substrate.

Claims (4)

Producing a single crystal silicon substrate from at least a single crystal silicon ingot to form a bond wafer and a base wafer; forming a silicon oxide film on at least one surface of the bond wafer and the base wafer; and In a method for manufacturing an SOI substrate comprising a step of bonding the bond wafer and the base wafer through a film, and a step of thinning the bonded bond wafer,
Before applying heat treatment to the bond wafer at least first, by applying an internal defect manifestation heat treatment to a single crystal silicon substrate made from the single crystal silicon ingot, and inspecting the internal defect density of the single crystal silicon substrate, A single crystal silicon ingot having an internal defect density of 1 × 10 ⁸ pieces / cm ³ or less is selected, and an SOI substrate is manufactured using the single crystal silicon substrate manufactured from the selected single crystal silicon ingot as the bond wafer. A method for manufacturing an SOI substrate, comprising:   The internal defect revealing heat treatment is performed at a temperature of a heat treatment that the bond wafer first receives in the manufacturing process of the SOI substrate, or a temperature lower than a heat treatment that the bond wafer first receives in the manufacturing process of the SOI substrate and 800 ° C. or more. The method for manufacturing an SOI substrate according to claim 1, wherein the heat treatment is performed at a temperature.   3. The method for manufacturing an SOI substrate according to claim 1, wherein the inspection of the internal defect density is performed at a depth of 3 μm or more from a surface of the single crystal silicon substrate in which the internal defect density is inspected. .   4. The method for manufacturing an SOI substrate according to claim 1, wherein a thickness of the SOI layer of the SOI substrate to be manufactured is 3 μm or more. 5.

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