METHOD FOR DEPOSITING SINGLE CRYSTAL SiC EPITAXIAL GROWTH FILM, METHOD FOR MANUFACTURING SEMICONDUCTOR DEVICE, COMPOSITE SUBSTRATE AND SEMICONDUCTOR DEVICE

Abstract

To provide: a method for depositing a single crystal SiC epitaxial growth film including a high quality epitaxial film having an epitaxial growth surface less in defects; a method for manufacturing a semiconductor device; a composite substrate; and a semiconductor device.SOLUTION: A method for depositing a single crystal SiC epitaxial growth film comprises: an introduction step of introducing reducing gas to put a bonded substrate including a polycrystal SiC substrate and a single crystal SiC film into a reducing gas atmosphere; and a film deposition step of depositing a single crystal SiC epitaxial growth film at a film deposition temperature held in the reducing gas atmosphere on the surface to be deposited of the single crystal SiC film of the bonded substrate. The film deposition temperature is less than 1500°C, and an etching amount obtained by etching the surface to be deposited of the single crystal SiC film with the reducing gas is 0.1 μm.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for forming a single crystal SiC epitaxially grown film, a method for manufacturing a semiconductor device, a composite substrate, and a semiconductor device. [Background technology]

[0002] As a method for obtaining a SiC bonded substrate having a single crystal SiC thin film on a support substrate such as polycrystalline SiC (silicon carbide), there is a technique in which hydrogen ions are implanted into the surface of the single crystal SiC substrate to form a hydrogen ion implanted layer, a support substrate made of a material different from the single crystal SiC is bonded to the surface of the single crystal SiC substrate on which the hydrogen ion implanted layer has been formed, and then the single crystal SiC substrate is peeled off at the hydrogen ion implanted layer. It is known that the surface of the single crystal SiC thin film of the SiC bonded substrate obtained by such a technique is polished or hydrogen etched, and then SiC is epitaxially grown on the surface of this single crystal SiC thin film (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2012-146695 A Summary of the Invention [Problem to be solved by the invention]

[0004] The temperature conditions for epitaxially growing SiC on the single crystal SiC thin film of the SiC bonded substrate are set to about 1500°C to 1600°C, similar to the epitaxial growth of SiC on a single crystal SiC substrate that is not a SiC bonded substrate, thereby making it possible to increase the growth rate of the epitaxial growth layer. Before epitaxially growing SiC on the single crystal SiC thin film of the SiC bonded substrate or on a single crystal SiC substrate that is not a SiC bonded substrate, the surface to be epitaxially grown is smoothed by CMP polishing (Chemical Mechanical Polishing) or hydrogen etching, etc. to reduce the surface roughness.

[0005] However, even if the surface is smoothed by chemical polishing or etching so that there are no defects on the surface, invisible latent scratches remain on the surface, and there is a problem that the surface defects of the formed epitaxial growth layer increase, especially when epitaxial growth of SiC is performed at a high growth rate. In addition, especially when attempting to grow SiC epitaxially on a single-crystal SiC thin film of a SiC bonded substrate, if CMP polishing or hydrogen etching is performed too strongly before starting epitaxial growth, the single-crystal SiC thin film bonded to the support substrate will disappear, and the required epitaxial growth layer cannot be obtained.

[0006] The embodiments described below have been made to solve these problems, and have the object of providing a method for forming a single crystal SiC epitaxially grown film having a high-quality epitaxial film with an epitaxial growth surface with few defects, a method for manufacturing a semiconductor device, a composite substrate, and a semiconductor device. [Means for solving the problem]

[0007] In order to solve the above problems, the method for forming a single crystal SiC epitaxial growth film of the present invention includes a film formation step of forming a single crystal SiC epitaxial growth film on a film formation target surface of a single crystal SiC film of a bonded substrate comprising a polycrystalline SiC substrate and a single crystal SiC film, at a film formation temperature maintained in a reducing gas atmosphere, and a reducing gas introduction step of introducing a reducing gas to place the bonded substrate under the reducing gas atmosphere prior to the film formation step, wherein the film formation temperature is less than 1500°C, and the amount of etching of the film formation target surface of the single crystal SiC film by the reducing gas is 0.1 μm or less.

[0008] In order to solve the above problems, the method for manufacturing a semiconductor device of the present invention includes a step of forming components of a semiconductor element in the single crystal SiC epitaxial growth film of a composite substrate obtained by the method for forming a single crystal SiC epitaxial growth film of the present invention, the composite substrate being formed of a polycrystalline SiC substrate, a single crystal SiC film, and a single crystal SiC epitaxial growth film, in that order.

[0009] In order to achieve the above object, the present invention provides a composite substrate comprising a polycrystalline SiC substrate, a single crystal SiC film, and a single crystal SiC epitaxially grown film laminated in this order, the single crystal SiC film being a film from which a damaged region has been removed, the single crystal SiC film having a thickness of 1 μm or less in the lamination direction of the composite substrate, and the single crystal SiC epitaxially grown film having a defect density of 1 defect / cm. 2 The following is the result.

[0010] In order to achieve the above object, a semiconductor device of the present invention is a semiconductor device using the above-mentioned composite substrate of the present invention. Effect of the Invention

[0011] According to each embodiment, it is possible to provide a method for forming a single crystal SiC epitaxially grown film having a high-quality epitaxial film with an epitaxial growth surface with few defects, a method for manufacturing a semiconductor device, a composite substrate, and a semiconductor device. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a perspective view showing a typical laminated substrate 100. [Diagram 2] FIG. 2 is a perspective view showing a schematic diagram of a composite substrate 500. [Diagram 3] FIG. 1 is a diagram showing an example of a temperature sequence in a method for forming a single crystal SiC epitaxial growth film 400. [Figure 4] 4 is a diagram showing an example of a temperature sequence in a method for forming a single-crystal SiC epitaxial growth film 400, which is different from that shown in FIG. [Diagram 5] 5 is a diagram showing an example of a temperature sequence in a method for forming a single-crystal SiC epitaxial growth film 400, which is different from those in FIGS. [Figure 6] FIG. 1 is a cross-sectional side view of a single-crystal SiC film photographed using a transmission electron microscope (TEM). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, an example of an embodiment will be described with reference to the drawings.

[0014] [Method of forming single crystal SiC epitaxial film] One method for forming single crystal SiC epitaxially grown films is the chemical vapor deposition (CVD) method. One type of equipment that can be used for the CVD method is a single-wafer horizontal CVD device. The CVD method has a simple device configuration, and the growth of the epitaxially grown film can be controlled by turning the gas on and off, making it a growth method with excellent controllability and reproducibility of the epitaxial film.

[0015] [Laminated boards] 1 includes a polycrystalline SiC substrate 200 and a single-crystal SiC film 300 bonded to the surface of the polycrystalline SiC substrate 200. The bonded substrate 100 uses a high-quality single-crystal SiC film 300 for the portion forming the components of a semiconductor device, and bonds this to the polycrystalline SiC substrate 200, which serves as a support substrate, thereby providing a substrate that combines a low-cost support substrate portion with high-quality single-crystal SiC.

[0016] The bonded substrate 100 can be manufactured, for example, by a technique of injecting hydrogen ions into the surface of a single crystal SiC substrate to form a hydrogen ion implanted layer, bonding a polycrystalline SiC substrate 200 to the surface of the single crystal SiC substrate with the hydrogen ion implanted layer formed thereon, and then peeling off the single crystal SiC substrate at the hydrogen ion implanted layer to form a single crystal SiC film 300.

[0017] (Polycrystalline SiC substrate) The polycrystalline SiC substrate 200 may be a substrate made of polycrystalline SiC formed by, for example, a CVD method. One example of the shape of the polycrystalline SiC substrate 200 is a disk shape with a thickness of 200 μm to 500 μm and a diameter of 4 inches to 8 inches. For example, it is formed into a 6-inch disk shape with a thickness of about 350 μm. The polycrystalline SiC of the polycrystalline SiC substrate 200 is composed of any one of 4H-SiC crystal, 6H-SiC crystal, and 3C-SiC crystal, or a mixture thereof.

[0018] (single crystal SiC film) The single crystal SiC film 300 is made of single crystal SiC and has a diameter of 4 to 8 inches, which is the same as that of the polycrystalline SiC substrate 200. There are no particular limitations on the thickness before the film-forming surface 310 is formed, but the thickness may be, for example, about 0.3 μm to 2.0 μm.

[0019] As the single crystal SiC film 300, a disk-shaped 4H-SiC single crystal for epitaxial film formation obtained by processing a bulk single crystal of silicon carbide prepared by sublimation method or the like can be used, or a 4H-SiC epitaxial layer formed on a single crystal by sublimation method or the like can be used.18 cm -3 ~8×10 18 cm -3 The dopants that can be used include boron, gallium, phosphorus, vanadium, nitrogen, and the like.

[0020] The method for forming a single crystal SiC epitaxially grown film includes the following film forming step and reducing gas introducing step.

[0021] [Film forming process] The film formation step is a step of forming a single crystal SiC epitaxially grown film 400 on the film formation target surface 310 of the single crystal SiC film 300 of the bonded substrate 100 at a film formation temperature maintained in a reducing gas atmosphere. This step results in a composite substrate 500 on which the single crystal SiC epitaxially grown film 400 is formed (FIG. 2).

[0022] FIG. 3 shows an example of a temperature sequence in a method for forming a single crystal SiC epitaxial growth film 400. In FIG. 3, the vertical axis indicates an increase in the ambient temperature (T), and the horizontal axis indicates the passage of time (t). The thick arrows indicate the timing of introducing the raw material gas and the continued introduction of the raw material gas after that timing. In FIG. 3, the raw material gas is introduced at time t4, and the introduction of the raw material gas is continued after t4. The thin arrows indicate the timing of introducing the reducing gas and the continued introduction after that timing. In FIG. 4, the reducing gas is introduced at time t3, and the introduction of the reducing gas is continued after t3. That is, in FIG. 3, the reducing gas introduction process is started at time t3, and the film formation process is started at time t4. In addition, time t3 is the time when the ambient temperature in the film formation chamber becomes the film formation temperature T1.

[0023] As an example of the outline of the procedure for forming the single crystal SiC epitaxial growth film 400, first, the laminated substrate 100 is placed in the film formation chamber of the CVD apparatus, the ambient temperature in the film formation chamber is raised from room temperature to the film formation temperature T1, and the source gas and the reducing gas are introduced into the film formation chamber at an appropriate timing. The film formation temperature T1 is maintained in the reducing gas atmosphere, and when the film formation temperature T1 is stably maintained, the source gas is introduced into the film formation chamber. The introduction of the source gas starts the film formation process. Note that, in FIG. 3, an example is shown in which the ambient temperature is maintained at temperature T2 from time t1 to time t2 when the ambient temperature is raised from room temperature to the film formation temperature T1, but various other sequences may be applied, including the raising of the ambient temperature from room temperature to the film formation temperature T1 in a monotonically increasing manner.

[0024] <Film-forming temperature> In the film formation process, the film formation temperature T1 is set to less than 1500° C. By setting the film formation temperature T1 to less than 1500° C., the growth rate of epitaxial growth is reduced and single crystal SiC is epitaxially grown on the film formation target surface 310 of the single crystal SiC film 300. This makes it possible to obtain a high-quality single crystal SiC epitaxial growth film 400 that has a defect-free flat growth surface 410 and has high uniformity and reproducibility in film thickness and n-type dopant concentration.

[0025] In particular, if step bunching occurs on the growth surface 410 of the single crystal SiC epitaxial growth film 400, the smoothness of the growth surface 410 is impaired, and the surface roughness Sa becomes 0.3 nm or more. However, by setting the film formation temperature T1 to a low temperature of less than 1500° C., the occurrence of step bunching can be suppressed, and the smoothness of the growth surface 410 can be satisfied.

[0026] However, lowering the film formation temperature T1 may slow down the epitaxial growth rate and reduce manufacturing efficiency. In consideration of this, it is preferable that the lower limit of the film formation temperature T1 is equal to or higher than the temperature at which the film formation rate of the single crystal SiC epitaxial growth film 400 is 10 μm / h.

[0027] <Film formation conditions other than film formation temperature> (mixed gas) The silicon source gas and the carbon source gas, which are the raw materials for silicon carbide, are the raw material gases, and the raw material gases are mixed with a carrier gas such as a rare gas such as argon gas or helium gas, which serves to transport these raw material gases, and a reducing gas to form a mixed gas. The mixed gas may further contain a dopant gas such as nitrogen gas and argon gas as appropriate. The mixed gas obtained by mixing these gases is introduced to the film formation target surface 310 in the film formation chamber, and a single crystal SiC epitaxial growth film 400 is formed.

[0028] (raw gas) The silicon source gas is not particularly limited as long as it can form a single crystal SiC epitaxial growth film 400 on the film formation target surface 310 without any problems. For example, one or more selected from the group consisting of monomers SiH4, SiH3Cl, SiH2Cl2, SiHCl3, and SiCl4 can be used as the silicon source gas.

[0029] The carbon source gas is not particularly limited as long as it can form the single crystal SiC epitaxial growth film 400 on the film formation target surface 310 without any problems. Since it is in a gaseous state near room temperature and is convenient to handle, it is preferable to use a carbon source gas consisting of a saturated hydrocarbon having a carbon number of 5 or less, or an unsaturated hydrocarbon having a carbon number of 5 or less, and a mixture of one or more of these can be suitably used. In particular, one or more of the hydrocarbon gases selected from the hydrocarbons having a carbon number of 5 or less, such as methane, ethane, propane, butane, and similar hydrocarbon gases, can be appropriately used as the carbon source gas.

[0030] Furthermore, when forming the single crystal SiC epitaxial growth film 400, the ratio (C / Si) of the number of carbon atoms in the carbon source gas to the number of silicon atoms in the silicon source gas is important. By controlling C / Si to 0.7 to 1.3, it becomes easy to epitaxially grow the single crystal SiC epitaxial growth film 400 on the film formation target surface 310, and the growth rate can be increased, leading to improved productivity. If C / Si is out of the range of 0.7 to 1.3, the balance of the abundance ratio of silicon atoms and carbon atoms becomes poor, which may make film formation difficult, slow the film formation rate, or increase the amount of raw material gas not involved in film formation, resulting in waste of raw material gas. For example, if C / Si is less than 0.7, unreacted Si may adhere to the film in a metallic state (droplets), causing defects. Also, if C / Si exceeds 1.3, surface steps called bunching may occur, which may have an adverse effect on device fabrication. More preferably, C / Si is set to 0.8 to 1.2.

[0031] The flow rates of the raw material gases are not particularly limited, but while optimizing C / Si appropriately, the raw material gases are diluted with a reducing gas, a carrier gas, or the like, and the flow rate of the silicon source gas diluted to, for example, 5 to 15 volume %, more preferably 8 to 12 volume %, is set to 300 to 600 cc per minute, more preferably 400 to 500 cc per minute, and the flow rate of the carbon source gas diluted to, for example, 5 to 15 volume %, more preferably 8 to 12 volume %, is set to 50 to 150 cc per minute, more preferably 80 to 120 cc per minute.

[0032] (reducing gas) The reducing gas may be H2 gas, which can promote the formation of a SiC film. The flow rate of the reducing gas is not particularly limited, but since the reducing gas also has a role of diluting the raw material gas, the flow rate can be set to, for example, 50 to 200 L per minute.

[0033] (growth rate) In forming the single crystal SiC epitaxial growth film 400 having a high quality epitaxial film with an epitaxial growth surface with few defects, the growth rate of the silicon carbide single crystal thin film is preferably 10 to 70 μm / h, more preferably 10 to 30 μm / h. In order to achieve such a growth rate, the concentration and flow rate of the source gas in the mixed gas may be appropriately adjusted as described above.

[0034] (pressure) The growth pressure of the single crystal SiC epitaxial growth film 400 may be set to conditions generally used in CVD growth of the single crystal SiC epitaxial growth film 400. For example, the growth pressure is set to a range of 9 to 11 kPa, more preferably 9.5 to 10.5 kPa.

[0035] As for other conditions, general conditions for growing the single crystal SiC epitaxial growth film 400 by CVD can be adopted.

[0036] [Reducing gas introduction process] The reducing gas introduction step is a step of introducing a reducing gas to place the bonded substrate 100 in a reducing gas atmosphere. For example, by introducing a reducing gas into a film formation chamber, the bonded substrate 100 can be placed in a reducing gas atmosphere. Since it is important to stabilize the conditions such as temperature, pressure, and atmospheric gas during film formation before starting the film formation step using a source gas, the reducing gas introduction step is performed before the film formation step.

[0037] In addition, the reducing gas has a property of etching SiC, and in this embodiment, the deposition target surface 310 of the single crystal SiC film 300 is etched by the reducing gas. As the etching progresses, there is a risk that the single crystal SiC film 300 will be partially disappeared and the polycrystalline SiC substrate 200 will be exposed on the deposition target surface 310. Since the single crystal SiC epitaxial growth film 400 will not grow on the exposed portion of the polycrystalline SiC substrate 200, it is necessary to prevent the polycrystalline SiC substrate 200 from being exposed.

[0038] In order to prevent exposure of polycrystalline SiC substrate 200, the etching amount of deposition target surface 310 of single crystal SiC film 300 by the reducing gas must be less than the film thickness of single crystal SiC film 300, specifically, 0.1 μm or less, more preferably 0.08 μm or less. Although the lower limit of the etching amount is ideally 0 μm, when H2 gas is used as the reducing gas, deposition target surface 310 is etched even slightly, so that the etching amount is preferably 0.01 to 0.1 μm.

[0039] The etching amount can be controlled by the flow rate of the reducing gas, the atmospheric temperature and pressure in the film formation chamber, and the like.

[0040] Temperature sequence in the reducing gas introduction step FIG. 4 is a diagram showing an example of a temperature sequence in a method for forming a single-crystal SiC epitaxial growth film 400, which is different from that shown in FIG. 3. In FIG. 4, the reducing gas introduction step is started at time t1, and the film formation step is started at time t4. Time t3 is the time when the atmospheric temperature in the film formation chamber reaches the film formation temperature T1. FIG. 5 is a diagram showing an example of a temperature sequence in a method for forming a single-crystal SiC epitaxial growth film 400, which is different from that shown in FIG. 3 and FIG. 4. In FIG. 3, the reducing gas introduction step is started at time t1, and the film formation step is started at time t4. Time t3 is the time when the atmospheric temperature in the film formation chamber reaches the film formation temperature T1. Hereinafter, an example of the atmospheric temperature in the film formation chamber in the reducing gas introduction step will be described with reference to FIGS. 3 to 5.

[0041] In the reducing gas introduction step, it is preferable to raise the atmospheric temperature in the film formation chamber to the film formation temperature T1, and to maintain the film formation temperature T1 after raising the temperature to the film formation temperature T1. In Figs. 3 to 5, once the temperature is raised to the film formation temperature T1 at time t3, the film formation temperature T1 is maintained until the film formation is started at time t4. Since it is important to stabilize the conditions such as temperature, pressure, and atmospheric gas during film formation before starting the film formation step using the source gas, it is preferable to control the film formation apparatus so that once the atmospheric temperature is raised to the film formation temperature T1 in the reducing gas introduction step, this temperature can be stably maintained, and once the state of maintaining the film formation temperature T1 is stabilized, the source gas is introduced into the film formation chamber to start the film formation step.

[0042] Regarding the timing for introducing the reducing gas into the film formation chamber, for example, as shown in FIG. 3, the introduction of the reducing gas may be started when the atmospheric temperature in the film formation chamber is at the film formation temperature T1.

[0043] 4, the introduction of the reducing gas may be started at time t1 when the ambient temperature T2 is lower than the film formation temperature T1. Then, this ambient temperature T2 may be maintained from time t1 to time t2. The period during which the ambient temperature T2 is maintained from time t1 to time t2 may be, for example, 90 seconds or less, more preferably 60 seconds or less, and further preferably 30 seconds or less.

[0044] Here, the ambient temperature T2 may be any temperature lower than the film formation temperature T1, but for example, the etching temperature at which SiC on the film formation target surface 310 is etched by H2 gas may be set as T2. An example of the lower limit of the etching temperature is the temperature at which the etching reaction of SiC by H2 gas starts, and an example of the upper limit of the etching temperature is the temperature at which the formation of the single crystal SiC epitaxial growth film 400 starts. More specifically, when the etching temperature is T2, it is 1000°C≦T2≦1480°C, and more preferably 1200°C≦T2≦1480°C.

[0045] Also, the ambient temperature T2 does not have to be maintained, and the introduction start temperature T3 at which the introduction of the reducing gas is started may be lower than the film formation temperature T1, and the ambient temperature may be raised so as to increase monotonically from the introduction start temperature T3 to the film formation temperature T1, as shown in Fig. 5. Note that T3 may be the same temperature as T2, or may be a temperature higher than T2, or may be a temperature lower than T2.

[0046] The deposition target surface 310 of the single crystal SiC film 300 to be etched by the reducing gas may be a surface that has been polished by CMP. By polishing by CMP, the deposition target surface 310 is smoothed and the surface roughness is reduced, resulting in a flat surface. By depositing a film on such a surface, a high-quality epitaxial film having an epitaxial growth surface with few defects can be formed.

[0047] (CMP polishing process) To obtain a bonded substrate 100 in which the film-forming surface 310 is a CMP-polished surface, such a bonded substrate 100 may be obtained by purchase or the like, or such a bonded substrate 100 may be obtained by performing a CMP polishing step in which the surface of the single-crystal SiC film 300 is CMP-polished to obtain the film-forming surface 310 before the reducing gas introduction step.

[0048] Since the thickness of the single crystal SiC film 300 is reduced by CMP polishing, it is preferable to polish the single crystal SiC film 300 to a thickness of 0.3 μm or less, more preferably 0.1 μm or less, so as to prevent the polycrystalline SiC substrate 200 from being exposed.

[0049] For polishing the film formation target surface 310 by CMP, a polishing method and polishing device known as a method for CMP of single crystal SiC can be used. For example, as the polishing device, a rotary type polishing device can be used in which a polishing pad is attached to a circular platen, and a slurry is dropped onto the polishing pad while the polishing pad is in contact with a carrier holding the bonded substrate 100 and rotated together. In addition, a known slurry can be used as appropriate for the polishing.

[0050] [Method of manufacturing semiconductor devices] The above-mentioned method for forming a single crystal SiC epitaxial growth film provides a composite substrate 500 in which a polycrystalline SiC substrate 200, a single crystal SiC film 300, and a single crystal SiC epitaxial growth film 400 are laminated in this order. A method for manufacturing a semiconductor device includes a step of forming components of a semiconductor element on the single crystal SiC epitaxial growth film 400 of the composite substrate 500. Examples of the components of the semiconductor element include a circuit pattern.

[0051] The method for manufacturing a semiconductor device may also include a step of forming a surface protective layer for protecting the formed circuit pattern with a resin or the like, and a back-grinding step of grinding the back surface side opposite to the surface on which the circuit pattern is formed after the surface protective layer is formed to thin the polycrystalline SiC substrate 200. Furthermore, a step of forming a drain electrode as a back surface electrode after the back-grinding step, and dicing may also be performed to remove the surface protective layer of the semiconductor device and cut the semiconductor device using a diamond blade or the like to form dies.

[0052] [Composite board] The composite substrate 500 is a substrate in which a polycrystalline SiC substrate 200, a single crystal SiC film 300, and a single crystal SiC epitaxially grown film 400 are laminated in this order (FIG. 2). The composite substrate 500 can be manufactured by the method for forming a single crystal SiC epitaxially grown film of the above embodiment.

[0053] As described above, the bonded substrate 100 is manufactured by, for example, peeling off a single crystal SiC substrate at a hydrogen ion implantation layer and forming a single crystal SiC film 300 on a polycrystalline SiC substrate 200. Damage from the hydrogen ion implantation and damage from peeling cause a damage region having crystal defects on the surface of the single crystal SiC film 300. This damage region can be confirmed using a transmission electron microscope (TEM). For example, in the side cross-sectional view of the single crystal SiC film 300 photographed using a TEM shown in FIG. 6, a layer-like damage region 320 having a thickness of about 100 nm exists on the surface of the single crystal SiC film 300 in FIG. 6(A).

[0054] If a single crystal SiC epitaxial growth film is formed with this damaged region 320 present, the epitaxial growth film will have many surface defects. Therefore, the damaged region 320 is removed by CMP polishing or etching with H2 gas to form the film-forming surface 310 (Figure 6(B)).

[0055] Even if the surface of the film-forming target surface 310 is smoothed by such polishing or etching so that there are no defects on the surface of the film-forming target surface 310, there is a risk that invisible latent scratches remain on the film-forming target surface 310, resulting in many surface defects in the formed single-crystal SiC epitaxial growth film 400. Therefore, it is preferable that the single-crystal SiC film 300 is a film from which the damaged region 320 has been completely removed. Furthermore, it is more preferable that the single-crystal SiC film 300 is a film from which latent scratches have been removed by removing not only the damaged region 320 but also the single-crystal SiC film 300 below the damaged region 320 by a thickness of about 50 to 150 nm while preventing the exposure of the polycrystalline SiC substrate 200.

[0056] In the composite substrate 500 of this embodiment, the thickness of the single crystal SiC film 300 in the stacking direction of the composite substrate 500 is 1 μm or less, and more preferably 0.27 μm or more. The thickness varies depending on the depth at which the hydrogen ion implanted layer is formed, and this depth depends on the hydrogen ion implantation energy. If the composite substrate 500 is manufactured using the bonded substrate 100 manufactured by adjusting the hydrogen ion implantation energy to 45 to 150 keV, the thickness of the single crystal SiC film 300 can be controlled to 0.27 to 1 μm.

[0057] Indices for evaluating the quality of the single crystal SiC epitaxial growth film 400 include surface roughness, defect density, and n-type dopant density. Regarding defect density, epitaxial defects on the Si surface currently in practical use include defects exposed on the surface such as stacking fault complexes (called Carrots), polytype inclusions (called Triangles and Comets), and particle inclusions (called Large Pits), as well as basal plane dislocations (BPDs) and stacking faults (SFs). Here, defects exposed on the surface are caused by the surface condition of the single crystal, particles, dislocations of the single crystal, dust from the epitaxial film formation device, and epitaxial growth conditions (epitaxial film formation conditions). In addition, BPDs are caused by BPD-TED conversion in the early stage of epitaxial growth, and SFs are caused by the SFs of the single crystal and the epitaxial growth conditions. In the case of the composite substrate 500, from the viewpoint of using the composite substrate 500 in a semiconductor device, the defect density of the main surface (growth surface 410) of the single crystal SiC epitaxial growth film 400 is 1 / cm 2 It is preferable that:

[0058] The n-type dopant density in the single crystal SiC epitaxial growth film 400 may be the density used in a typical semiconductor device. For example, for a breakdown voltage of 1200 V, it may be 9×10 15 cm -3 ~1.1×10 16 cm -3 It is desirable that the degree of

[0059] It is important that the surface roughness of the growth surface 410 of the single crystal SiC epitaxial growth film 400 is smooth to prevent pattern defects when semiconductor devices are miniaturized, and it is preferable that the surface roughness Sa is 0.3 nm or less, and more preferably 0.2 nm or less, within a 1.5 mm × 1.5 mm area of ​​the growth surface 410. The Sa of the growth surface 410 is generally equal to or greater than the Sa of the film-forming surface 310, which is the surface of the single crystal SiC film 300 before the growth of the single crystal SiC epitaxial growth film 400, and taking this into consideration, it is important to keep the Sa of the film-forming surface 310 before the growth of the single crystal SiC epitaxial growth film 400 to 0.2 nm or less.

[0060] Furthermore, in consideration of the withstand voltage of the semiconductor device, the thickness of the single crystal SiC epitaxial growth film 400 is desirably 5 to 15 μm, and more desirably 9 to 11 μm, in order to provide a reverse withstand voltage of 1200 V.

[0061] [Semiconductor devices] The semiconductor device may be a semiconductor device using the above-mentioned composite substrate 500, and may be a semiconductor device having a circuit pattern as a component of a semiconductor element or a drain electrode as a back electrode, or may be a semiconductor device diced into a chip shape. EXAMPLES

[0062] The present invention will be explained in more detail below by showing examples, but the present invention is not limited to the following examples in any way.

[0063] [Example 1] (Fabrication of polycrystalline SiC substrate 200) A seed substrate formed in a disk shape made of carbon was used as a base substrate, and a SiC polycrystalline film having a thickness of 2 mm was formed on the surface of the base substrate by chemical vapor deposition (CVD). Methylchlorosilane was used as the raw material gas, and hydrogen and nitrogen gases were used as the carrier gas. The growth temperature in this chemical vapor deposition method was 1400°C. Then, the base substrate was heated and removed in an air atmosphere at 1000°C by a combustion method, and a disk-shaped SiC polycrystalline film was produced. This SiC polycrystalline film was heat-treated using an atmosphere-controlled heating furnace. The heating temperature was 1700°C, the heating temperature was held for 24 hours, and the atmosphere in the furnace was an argon gas atmosphere. Then, the surface of the SiC polycrystalline film was ground and polished to be flattened, and a polycrystalline SiC substrate 200 having a diameter of 6 inches (about 150 mm) and a thickness of 350 μm was obtained.

[0064] <Manufacture of the bonded substrate 100> The manufactured polycrystalline SiC substrate 200 was used to manufacture the bonded substrate 100 by a delamination technique (Smart Cut (registered trademark)) using hydrogen atom ablation. As a single crystal SiC substrate to be bonded to the polycrystalline SiC substrate 200, a 350 μm thick, 6 inch (about 150 mm) diameter single crystal SiC substrate with a main surface orientation of <0001> The disk-shaped substrate was a 4H polytype.

[0065] Hydrogen ions were implanted into the bonding surface of the single crystal SiC substrate to be bonded to the polycrystalline SiC substrate 200, forming a hydrogen ion implanted layer in a region 0.6 μm deep from the bonding surface. Furthermore, high concentration phosphorus ions were implanted into the outermost surface of the single crystal SiC substrate to reduce interface resistance. The single crystal SiC substrate and the polycrystalline SiC substrate 200 were attracted by an electrostatic chuck and set in a chamber. Next, the electrostatic chuck was moved to align the relative positions of the single crystal SiC substrate and the polycrystalline SiC substrate 200 so that the two substrates can contact each other in the correct positional relationship during the room temperature bonding process. Next, the chamber was filled with 2×10 -6The chamber was placed in a vacuum state of 10 Pa. Next, a neutral atomic beam of argon was uniformly irradiated to the entire surface of the bonding target surface of the single crystal SiC substrate and the entire surface of the bonding target surface of the polycrystalline SiC substrate 200 using a FAB gun, removing the oxide film and adsorption layer on both bonding target surfaces to expose the bonds and activate them. Next, while maintaining the vacuum state at room temperature, the electrostatic chuck was moved within the chamber, so that the bonding target surfaces of the single crystal SiC substrate and the bonding target surfaces of the polycrystalline SiC substrate 200 were brought into contact with each other in a vacuum state within the chamber and directly bonded by covalent bonds to obtain a bonded substrate.

[0066] Next, using a furnace, the bonded substrates were heated to 1000°C in an inert atmosphere filled with argon gas to form a microbubble layer in the hydrogen ion implanted layer, the single crystal SiC substrate was separated at the microbubble layer, and a thin plate-shaped single crystal SiC film 300 with a thickness of 0.6 μm was transferred to the polycrystalline SiC substrate 200.

[0067] Finally, the surface of the transferred single crystal SiC film 300 was processed by CMP to make it smooth, and the damaged area 320 and invisible latent scratches were completely removed to form the film formation target surface 310, thereby producing the bonded substrate 100. The thickness of the single crystal SiC film 300 of the bonded substrate 100 was measured by the ellipsometric method and was about 0.4 to 0.5 μm.

[0068] <Manufacture of composite substrate 500> The single crystal SiC epitaxial growth film 400 was formed using a single-wafer horizontal CVD apparatus, and a reducing gas introduction step and a film formation step were performed based on the temperature sequence shown in FIG.

[0069] (Reducing gas introduction process) The laminated substrate 100 was set in the film formation chamber of the CVD apparatus, and the temperature in the film formation chamber was raised from room temperature to temperature T3 in a vacuum state, and then a reducing gas introduction process was performed. At temperature T3 during the temperature rise from room temperature to film formation temperature T1, the vacuum state was stopped and the introduction of H2 gas as a reducing gas into the film formation chamber was started. The flow rate of H2 gas was set to 100 L per minute. While introducing H2 gas, the atmospheric temperature in the film formation chamber was raised from temperature T3 to film formation temperature T1 over 12 minutes. Then, the film formation temperature T1 was held for 1 minute so that the atmospheric temperature was stabilized at the film formation temperature T1. That is, in FIG. 5, the period from time t1 to t3 was set to 12 minutes, and the period from time t3 to t4 was set to 1 minute.

[0070] (Film forming process) The deposition temperature T1 was set to 1480°C, and the pressure was set to 10.5 kPa. At time t4 when the atmospheric temperature in the deposition chamber stabilized at the deposition temperature T1, the introduction of the source gas was started to form a single crystal SiC epitaxial growth film on the deposition target surface 310 of the bonded substrate 100. As epitaxial growth conditions, the source gas used was SiH4 diluted with H2 gas to 10 volume % at a flow rate of 450 cc per minute, and C3H8 diluted with H2 gas to 10 volume % at a flow rate of 102.3 cc per minute, and the introduction of H2 gas at a flow rate of 100 L per minute was continued even in the deposition process. In addition, nitrogen gas was introduced as an n-type dopant at a flow rate of 80 cc per minute.

[0071] (Surface roughness Sa) The surface roughness Sa of the growth surface 410 after the film formation process was determined by measuring the surface roughness at nine points within a 1.5 mm x 1.5 mm area of ​​the growth surface 410 using a white light differential interferometer (ZYGO) as a measuring device and calculating the average value. The surface roughness Sa of the growth surface 410 was 0.11 nm. The surface roughness Sa of the film formation target surface 310 before the film formation process was determined by the same method and was 0.15 nm. From these results, it was found that the surface roughness Sa before and after the epitaxial growth in Example 1 was equivalent and good.

[0072] (Surface defects, BPD, SF) Surface defects (CarrotTriangle, Large Pit), BPD, and SF were calculated using a map measured by SICA88X. There were 30 surface defects (density 0.19 cm -2 ), BPD32 pieces (density 0.20cm -2 ), SF96 pieces (density 0.60cm -2 The total number of defects was 158 (density 0.98 cm -2 ), and the defect density required for semiconductor device applications is 1 / cm 2 The results met the following conditions:

[0073] (n-type dopant concentration) The in-plane distribution of n-type dopant density in the single crystal SiC epitaxial growth film 400 was calculated by CV measurement. The average n-type dopant density was 1.08×10 16 cm ―3 It was.

[0074] (Film thickness) The in-plane distribution of the film thickness of the single crystal SiC epitaxially grown film 400 was determined by FTIR measurement. The average film thickness was 10.38 μm.

[0075] (Amount of etching on the surface to be coated) The etching amount of the film-forming target surface 310 of the single-crystal SiC film 300 by the H2 gas was calculated from the difference in film thickness before and after the reducing gas introduction step by performing the reducing gas introduction step again using the bonded substrate 100, removing the bonded substrate 100 without performing the film-forming step, and measuring the film thickness of the single-crystal SiC film 300 by the ellipsometric method. As a result, the etching amount in Example 1 was 0.1 μm or less.

[0076] These results show that composite substrate 500 of Example 1 has a flat growth surface 410 with a small defect density, and a high-quality epitaxial film with high uniformity in film thickness and n-type dopant concentration.

[0077] The thickness of the single crystal SiC film 300 of the bonded substrate 100 can be selected in the range of 0.3 μm or more and 2.0 μm or less. The single crystal SiC film 300 is achieved by adjusting the implantation depth of hydrogen ions. Specifically, for example, by setting the acceleration energy of hydrogen ions to 45 keV, 150 keV, and 300 keV, hydrogen ions can be implanted at a high concentration into regions of the SiC single crystal substrate at depths of about 0.3 μm, 1.2 μm, and 2.0 μm, respectively, from the surface. By changing only the implantation conditions of hydrogen ions and following the method described in detail in Example 1 for other conditions, a composite substrate 500 in which the thickness of the single crystal SiC film 300 is 0.27 μm or more and 1.0 μm or less can be finally produced.

[0078] [Comparative Example 1] Except for changing the film formation temperature T1 from 1480° C. to 1575° C., the polycrystalline SiC substrate 200, the bonded substrate 100, and the composite substrate 500 were produced under the same conditions as in Example 1. In addition, the surface roughness Sa, surface defects, BPD, SF, n-type dopant concentration, film thickness, and etching amount of the film formation target surface were also measured and calculated in the same manner as in Example 1.

[0079] (Surface roughness Sa) The surface roughness Sa of the growth surface 410 was 0.21 nm, and the surface roughness Sa of the film-forming surface 310 before the film-forming step was determined to be 0.10 nm. In Comparative Example 1, the surface roughness Sa increased before and after the epitaxial growth.

[0080] (Surface defects, BPD, SF) There were 140 surface defects (density 0.87 cm -2 ), BPD195 pieces (density 1.21cm -2 ), SF461 pieces (density 0.60cm -2 The total number of defects was 796 (density 4.94 cm -2 ), and the defect density required for semiconductor device applications is 1 / cm 2 The following conditions were not met:

[0081] (n-type dopant concentration) The average n-type dopant density in the single crystal SiC epitaxial growth film 400 is 0.93×10 16 cm ―3 It was.

[0082] (Film thickness) The average film thickness was 9.91 μm.

[0083] (Amount of etching on the surface to be coated) The amount of etching in Comparative Example 1 was 0.03 μm.

[0084] From these results, it was found that when the epitaxial growth temperature T1 was set to 1575° C., which was higher than that in Example 1, composite substrate 500 could not provide a high-quality epitaxial film having a flat growth surface 410 with low defect density.

[0085] From the results of Example 1 and Comparative Example 1, by lowering the deposition temperature T1, the growth rate of the single crystal SiC epitaxial growth film 400 was lowered and the surface roughness of the growth surface 410 was improved. The growth rate of the single crystal SiC epitaxial growth film 400 can be reduced not only by the growth temperature but also by the flow rates and ratios of the source gases SiH4 and C3H8. Therefore, when the single crystal SiC epitaxial growth film 400 is grown using the CVD method, if the deposition temperature T1 is 1500°C or lower, the composite substrate 500 has a defect-free flat growth surface 410, and a high-quality epitaxial film with high uniformity in film thickness and n-type dopant concentration can be obtained.

[0086] [Comparative Example 2] 4, a reducing gas introduction step and a film formation step were performed to form a single crystal SiC epitaxial growth film 400. The rest of the steps were the same as those in Example 1, and the polycrystalline SiC substrate 200, the bonded substrate 100, and the composite substrate 500 were produced.

[0087] (Reducing gas introduction process) The laminated substrate 100 was set in the film formation chamber of the CVD apparatus, and the temperature in the film formation chamber was raised from room temperature to temperature T2 in a vacuum state, and then a reducing gas introduction process was performed. At temperature T2 during the temperature rise from room temperature to film formation temperature T1, the vacuum state was stopped and the introduction of H2 gas as a reducing gas into the film formation chamber was started. The flow rate of H2 gas was set to 100 L per minute. While introducing H2 gas, the atmospheric temperature in the film formation chamber was held at temperature T2 for 3 minutes, and then the temperature was raised from temperature T2 to film formation temperature T1 over 12 minutes. Then, the film formation temperature T1 was held for 1 minute so that the atmospheric temperature was stabilized at film formation temperature T1. That is, in FIG. 4, the period from time t1 to t2 was set to 3 minutes, the period from time t2 to t3 was set to 12 minutes, and the period from time t3 to t4 was set to 1 minute.

[0088] (Film forming process) The film formation temperature T1 was set to 1575° C. and the pressure was set to 10.5 kPa. At time t4 when the atmospheric temperature in the film formation chamber stabilized at the film formation temperature T1, the introduction of the raw material gas was started to form a single crystal SiC epitaxial film on the film formation target surface 310 of the bonded substrate 100.

[0089] When the composite substrate after the single crystal SiC epitaxial growth film was formed was checked, a normal epitaxial film growth surface 410 was formed on the outer periphery of the composite substrate, but the inside was cloudy, resulting in an abnormal film formation. When this abnormal part was observed, it was found that the single crystal SiC film 300 of the bonded substrate 100 had disappeared and polycrystalline SiC had grown epitaxially. Therefore, in Comparative Example 2, the surface roughness Sa, surface defects, BPD, SF, n-type dopant concentration, and film thickness were not measured or calculated.

[0090] Considering the result that polycrystalline SiC was epitaxially grown, the reducing gas introduction step was carried out again using the bonded substrate 100, the bonded substrate 100 was removed without carrying out the film formation step, the thickness of the single crystal SiC film 300 was measured by an ellipsometric method, and the etching amount of the single crystal SiC film 300 was calculated from the difference in film thickness before and after the reducing gas introduction step. As a result, the etching amount in Comparative Example 2 was 0.3 to 0.5 μm.

[0091] Table 1 shows the etching temperature, film formation temperature, etching time, heating time to the film formation temperature, the time during which the film formation temperature was maintained in the reducing gas introduction process (stable time), the thickness of the etching amount of the film formation target surface 310 etched by the H2 gas, and whether or not the single crystal SiC film 300 was lost due to etching by the H2 gas to expose the polycrystalline SiC substrate 200 (exposure of the polycrystalline substrate).

[0092] [Table 1]

[0093] Table 2 shows the film formation temperature in the film formation process, the growth rate of the single crystal SiC epitaxial growth film 400, the surface roughness Sa of the film formation target surface 310 before the film formation process and the growth surface 410 after the film formation process, the surface defects in the single crystal SiC epitaxial growth film 400, BPD, SF, the total number of defects, the density of the n-type dopant, and the thickness of the single crystal SiC epitaxial growth film 400. When the difference in the growth rate of the single crystal SiC epitaxial growth film 400 due to the difference in film formation temperature was evaluated, it was 12 μm per hour when the film formation temperature was 1480° C., and 17 μm per hour when the film formation temperature was 1575° C.

[0094] [Table 2] [Industrial Applicability]

[0095] According to this invention, it is possible to produce a composite substrate having a high-quality epitaxial film with a defect-free flat growth surface in epitaxial growth on a SiC bonded substrate. Therefore, if electronic devices are formed on such a substrate, it is expected that the characteristics and yield of the devices will be improved. [Explanation of symbols]

[0096] 100: bonded substrate, 200: polycrystalline SiC substrate, 300: single crystal SiC film, 310: film formation target surface, 320: damaged area, 400: single crystal SiC epitaxial growth film, 410: growth surface, 500: composite substrate

Claims

1. a film formation step of forming a single crystal SiC epitaxial growth film on a film formation target surface of a bonded substrate including a polycrystalline SiC substrate and a single crystal SiC film at a film formation temperature maintained under a reducing gas atmosphere; a reducing gas introduction step of introducing a reducing gas to place the bonded substrates under the reducing gas atmosphere before the film formation step; Including, The deposition temperature is less than 1500° C. a thickness of the single crystal SiC film that is etched by the reducing gas on the deposition target surface of the single crystal SiC film is 0.1 μm or less.

2. 2. The method for forming a single crystal SiC epitaxially grown film according to claim 1, wherein in the reducing gas introducing step, introduction of the reducing gas is started when the atmospheric temperature is at the film-forming temperature.

3. 2. The method for forming a single crystal SiC epitaxially grown film according to claim 1, wherein the reducing gas introducing step maintains an atmospheric temperature lower than the film formation temperature for 90 seconds or less.

4. 2. The method for forming a single crystal SiC epitaxially grown film according to claim 1, wherein, in the reducing gas introduction step, an introduction start temperature at which introduction of the reducing gas is started is lower than the film formation temperature, and the atmosphere temperature is raised from the introduction start temperature to the film formation temperature so that it monotonically increases.

5. 2. The method for forming a single crystal SiC epitaxially grown film according to claim 1, wherein in the reducing gas introducing step, the atmospheric temperature is raised to the film formation temperature, and after the temperature is raised to the film formation temperature, the film formation temperature is maintained.

6. 2. The method for forming a single crystal SiC epitaxial growth film according to claim 1, wherein the deposition target surface of the single crystal SiC film that is etched by the reducing gas is a surface that has been polished by CMP.

7. 2. The method for forming a single crystal SiC epitaxial growth film according to claim 1, further comprising a CMP polishing step of CMP-polishing a surface of the single crystal SiC film to obtain the film formation surface before the reducing gas introduction step, wherein the CMP polishing is performed to a thickness of 0.3 μm or less.

8. 2. The method for forming a single crystal SiC epitaxially grown film according to claim 1, wherein the film formation temperature is equal to or higher than a temperature at which a film formation rate of the single crystal SiC epitaxially grown film is 10 μm / h.

9. 2. A method for manufacturing a semiconductor device, comprising a step of forming components of a semiconductor element on a single crystal SiC epitaxially grown film of a composite substrate in which a polycrystalline SiC substrate, a single crystal SiC film, and a single crystal SiC epitaxially grown film are laminated in this order, the composite substrate being obtained by the method for forming a single crystal SiC epitaxially grown film as defined in claim 1.

10. A composite substrate having a polycrystalline SiC substrate, a single crystal SiC film, and a single crystal SiC epitaxially grown film laminated in this order, the single crystal SiC film is a film from which a damaged region has been removed, The thickness of the single crystal SiC film in the lamination direction of the composite substrate is 1 μm or less, The defect density of the main surface of the single crystal SiC epitaxial growth film is 1 / cm ２ The composite substrate is as follows:

11. The composite substrate according to claim 10 , wherein the thickness of the single crystal SiC film in the stacking direction of the composite substrate is 0.27 μm or more.

12. A semiconductor device using the composite substrate according to claim 10.

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