Semiconductor substrate manufacturing method

Abstract

To provide a manufacturing method for a semiconductor device, in which the deterioration in a forward direction of 4H-SiC can be suppressed in a separating technique by H+ injection.SOLUTION: A manufacturing method for a semiconductor substrate includes: an ion injecting step of forming an ion injection layer 2 by injection ions including H+ to a surface of a 4H-SiC substrate; a bonding step of bonding another supporting substrate 3 onto the surface of the 4H-SiC substrate after the ion injection step, thereby obtaining a bonded substrate 10; and a separating step of separating the 4H-SiC substrate at the ion injection layer 2 by performing a heating process on the bonded substrate 10 in a hydrogen-containing atmosphere, so as to divide into a bonded substrate 12 in which a surface layer of the 4H-SiC substrate has been transferred onto the supporting substrate 3 as a 4H-SiC layer and a separation substrate 11 corresponding to a substrate after the surface layer is separated from the 4H-SiC substrate.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing a semiconductor substrate, a semiconductor substrate, and a semiconductor device. [Background technology]

[0002] SiC has a wide band gap of 2.2 to 3.3 eV, which gives it high dielectric breakdown strength, and it also has high thermal conductivity, making it a promising semiconductor material for various semiconductor devices such as power devices and high-frequency devices.

[0003] However, when fabricating actual devices such as diodes using SiC as a semiconductor, a large number of carriers are injected into the substrate when a current is passed through in the forward direction, causing dislocations to expand and fluctuating the forward characteristics (Vf fluctuations), resulting in unstable operation and reduced reliability. This phenomenon is known as forward degradation, and is a major problem (Non-Patent Document 1).

[0004] As a method to stop the dislocation extension, a Cu ion implantation method (Non-Patent Document 2) was proposed in 2010, and recently, H + It has been reported that similar effects are also observed (Non-Patent Documents 3 and 4). + to 1.0×10 15 atoms / cm 2 A method of injecting a certain amount of

[0005] This H +Several other prior arts have been reported regarding the implantation of hydrogen ions into SiC. Patent Document 1 describes a method of preparing two SiC single crystal wafers, forming an oxide film on each, implanting hydrogen ions into one of the substrates, and then bonding them together at room temperature via the oxide layer, followed by heat treatment at 500°C or higher to divide the SiC single crystal wafer in two at the hydrogen ion implanted location, thereby producing a substrate for a semiconductor electronic device. In this method, an oxide film exists at the bonded portion, and when a vertical device is fabricated, this oxide film functions as an insulating layer, significantly limiting the functionality as a power device substrate. Patent Document 2 also describes a method of fabricating a substrate for a semiconductor electronic device using hydrogen ions. + Patent Document 2 discloses a method of bonding an implanted single crystal and a polycrystalline SiC substrate together, and then separating the single crystal and the polycrystalline SiC substrate. However, Patent Document 2 does not mention the increased cost of performing the separation twice, the difficulty of performing the separation in the respective prescribed steps, or the forward degradation. Furthermore, Patent Document 3 focuses on the impurity concentration and defect density, and describes a method of forming a high resistance substrate with a low defect density by using H + This method reduces defects that exist in the original substrate, but does not mention the subsequent forward degradation that affects reliability. + It is about the technology that causes substrate peeling due to H, and mentions the diffusion barrier (oxygen diffusion barrier) function, but there is no mention of forward degradation. + Although there is a description of separation by H, there is no solution to the forward degradation. + As described above, the prior art describes a method for producing the H + Suppression of forward degradation by implantation and H + The fabrication of substrates using implantation-assisted delamination techniques has been described in each paper, but H + There is no mention of suppressing forward degradation in the implantation stripping technique. [Prior art documents] [Patent documents]

[0006] [License 1] Special Announcement No. 11-003842 [License 2] Special Announcement No. 2016-018890 [License 3] Special Announcement No. 2014-022711 [License 4] Special Announcement No. 2007-329470 [Patent Document 5] Special Announcement No. 2007-227415 [License 6] Special Announcement No. 2022-510822 [Non-licensed literature]

[0007] [Non-licensed Document 1] M. Skowronski and S. Ha, “Degradation of hexagonal silicon-carbide-based bipolar devices”, J. Appl., Phys., 99, 01101(2006). [Non-licensed Document 2] B. Chen, H. Matsuhara, T. Sekiguchi, T. Ohyanagi, A. Kinoshita and H. Okumura, “Pinning of recombination-enhanced dislocation migration in 4H-SiC : Role of Cu and EH1 complex”, Appl. Phys. Lett., 96, 212110(2010). [Non-licensed Document 3] M. Kato, O. Watanabe, T. Mii, H. Sakane, S. Harada, “Suppression of stacking fault expansion in SiC PiN diodes by H+ implantation”, Abstract of 19th International Conference on Silicon Carbide and Related Materials, 453(2022). [Non-patent document 4] S. Harada, T. Mii, H. Sakane, M. Kato, “Suppression of recombination enhanced dislocation glide motion in 4HSiC by hydrogen ion implantation”, Abstract of 19th International Conference on Silicon Carbide and Related Materials, 459(2022). Summary of the Invention [Problem to be solved by the invention]

[0008] The present invention has been made to solve the above-mentioned problem of forward degradation of SiC elements at the substrate level, and furthermore, to efficiently use valuable bulk SiC substrates that are thinned and lost in the device process. More specifically, 4H-SiC, which is expected to be a high-voltage device substrate, suppresses forward degradation (current degradation) in which dislocations expand due to carrier injection when current is passed through, changing the electrical characteristics, and also suppresses the H + The objective is to achieve compatibility with ion-based substrate peeling technology. In other words, the ultimate object of the present invention is to simultaneously suppress the deterioration of forward characteristics due to the expansion of dislocations, which is a reliability problem, and to provide a cheaper SiC substrate. To this end, the present invention provides +The present invention provides a semiconductor device manufacturing method, a semiconductor substrate, and a semiconductor device that can suppress forward degradation of 4H-SiC in implantation-based delamination technology. [Means for solving the problem]

[0009] The present invention has been made to achieve the above object, and is directed to forming H on the surface of a 4H—SiC substrate. + a bonding step of bonding another support substrate to the surface of the 4H—SiC substrate that has been subjected to the ion implantation step to obtain a bonded substrate; and a delamination step of subjecting the bonded substrate to a heat treatment in an atmosphere containing hydrogen to delaminate the 4H—SiC substrate at the ion implantation layer, thereby separating the bonded substrate into a bonded substrate in which the surface layer of the 4H—SiC substrate has been transferred onto the support substrate as a 4H—SiC layer, and a delamination substrate, which is the substrate obtained after the surface layer has been delaminated from the 4H—SiC substrate.

[0010] In this method, hydrogen ions are implanted into the surface of a 4H-SiC substrate, which is then bonded to another support substrate. A delamination process is then performed in a hydrogen-containing atmosphere to create a bonded substrate. Epitaxial growth can then be performed on the bonded substrate thus created. This allows hydrogen to exist at the epitaxial growth interface, and delamination can be performed simultaneously. More specifically, this method involves applying H + When bonding a support substrate to a 4H-SiC substrate implanted with H and then peeling it off to transfer the surface layer of the 4H-SiC substrate to the support substrate, the surface layer is transferred by heat treatment in a hydrogen-containing atmosphere. + This suppresses the out-diffusion of 4H-SiC during the heat treatment that occurs during delamination. Furthermore, the delamination substrate, which is the 4H-SiC substrate after 4H-SiC has been transferred to the support substrate in the delamination process, can be reused as a substrate for transferring 4H-SiC to the support substrate by repeating the ion implantation, bonding, and delamination processes. Therefore, even if the 4H-SiC substrate is high-cost bulk 4H-SiC, no waste is produced during manufacturing, which is advantageous in terms of manufacturing cost and makes this an inexpensive manufacturing method. Therefore, in the method for manufacturing a semiconductor device of the present invention, the surface layer of the 4H—SiC substrate transferred to the support substrate can contain more hydrogen than when the heat treatment is not performed in a hydrogen atmosphere, and the hydrogen contained in the transferred surface layer prevents the dislocations in the 4H—SiC substrate from expanding, thereby reducing the amount of hydrogen. + The implantation-based delamination technique can also suppress the forward degradation of 4H-SiC and reduce manufacturing costs.

[0011] The delamination step is performed by heating the bonded substrate for a predetermined time at a temperature lower than the temperature at which the 4H—SiC substrate is delaminated from the ion-implanted layer, thereby delaminating the H + After the inward diffusion of ions, the temperature may be raised to a delamination temperature or higher to delaminate the 4H—SiC substrate at the ion-implanted layer. In this case, the H implanted in the ion implantation process + In order to inwardly diffuse the ions before peeling off the 4H-SiC substrate, H is formed outside the ion-implanted layer in the 4H-SiC substrate. + This allows the diffusion of dislocations in the 4H-SiC substrate, preventing dislocations from expanding over a wider area.

[0012] The 4H—SiC substrate may be bulk 4H—SiC, in which case the ion implantation step involves implanting H into the surface of the bulk 4H—SiC. + This is a step of implanting ions containing In this configuration, H is deposited on the surface of the bulk 4H-SiC. + Since ions containing 4H-SiC are implanted, there is no need to prepare a substrate on which 4H-SiC has been epitaxially grown in advance. Furthermore, the delamination process allows the 4H-SiC substrate, which is the 4H-SiC substrate after 4H-SiC has been transferred to the support substrate, to be reused as a substrate for transferring 4H-SiC to the support substrate by repeating the ion implantation, bonding, and delamination processes. Therefore, even if the 4H-SiC substrate is high-cost bulk 4H-SiC, no waste is produced during manufacturing, resulting in low manufacturing costs.

[0013] When the 4H—SiC substrate is bulk 4H—SiC, the method may include, after the separation step, an epitaxial step of forming an epitaxial layer by epitaxially growing 4H—SiC on the 4H—SiC layer of the bonded substrate. In this configuration, if the 4H-SiC substrate is bulk 4H-SiC, the H + Since 4H-SiC is epitaxially grown on a 4H-SiC layer containing H, the dislocations in the epitaxial layer are prevented from expanding when current is applied. + This can prevent the formation of a thin film, and a high-quality epitaxial layer can be used as the device layer.

[0014] The 4H—SiC substrate may be an epitaxial substrate formed by epitaxially growing 4H—SiC on the surface of bulk 4H—SiC to form an epitaxial layer. In this case, the ion implantation step may be performed by implanting H ions into the surface of the epitaxial layer. + This is a step of implanting ions containing In this configuration, H is deposited on the surface of the epitaxial layer of the epitaxial substrate. + This has the advantage that it is not necessary to grow a 4H—SiC epitaxial layer on the 4H—SiC layer of the bonded substrate after delamination.

[0015] The ion implantation step is + The injection volume is 5×10 16 atoms / cm 2 The process may be a step of implanting ions so as to achieve the above. In this configuration, H + The injection volume is 5×10 16 atoms / cm 2 Therefore, the amount of H is sufficient to separate the 4H-SiC substrate during the separation process. + can be implanted into the 4H—SiC substrate in the implantation process.

[0016] According to the present invention, there is provided a support substrate and a H + and a 4H—SiC layer containing ions including In this configuration, the H contained in the 4H—SiC layer bonded to the surface of the support substrate + However, this prevents the expansion of dislocations in the 4H-SiC layer when current is applied. Therefore, H + Degradation in the forward direction can also be suppressed in the implantation separation technique.

[0017] Furthermore, the present invention provides a semiconductor device comprising the above-described 4H—SiC substrate. In this configuration, the H contained in the 4H—SiC layer of the semiconductor device + However, it prevents dislocations from expanding when current is applied. Therefore, forward degradation of 4H—SiC can be suppressed, resulting in a highly reliable semiconductor device. [Effects of the Invention]

[0018] As described above, the configuration of the present invention effectively suppresses the forward degradation that is a problem with 4H—SiC, and also makes it possible to effectively utilize a peeled substrate even when using bulk SiC. More specifically, according to the method for manufacturing a semiconductor device of the present invention, H + The forward degradation of 4H—SiC can also be suppressed by the delamination technique using H implantation. + This technology also suppresses forward degradation of 4H-SiC in the delamination technique by implantation. Moreover, the delamination of the 4H-SiC substrate can be reused, which is extremely cost-effective. [Brief explanation of the drawings]

[0019] [Figure 1] 1 shows a 4H—SiC substrate and a semiconductor device according to an embodiment of the present invention. [Figure 2] 1A to 1C are diagrams showing a process flow of a method for manufacturing a semiconductor device according to an embodiment of the present invention, illustrating the case where the substrate to be peeled is bulk 4H—SiC. [Figure 3]1A to 1C are diagrams showing a process flow of a method for manufacturing a semiconductor device according to an embodiment of the present invention, in which the substrate to be peeled is an epitaxial substrate. [Figure 4] The procedure of the test method for the forward degradation test of the example and the comparative example is shown below. [Figure 5] ΔVf for Example 1, Example 2, and Comparative Example, which were determined from the results of the forward deterioration test, are shown. DETAILED DESCRIPTION OF THE INVENTION

[0020] The present invention will be described in detail below, but the present invention is not limited thereto.

[0021] As mentioned above, H + There has been a demand for a semiconductor device manufacturing method, a semiconductor substrate, and a semiconductor device that can suppress forward degradation of 4H—SiC even in the implantation-based delamination technology.

[0022] As a result of extensive research into the above-mentioned problems, the present inventors have found that H + a bonding step of bonding another support substrate to the surface of the 4H—SiC substrate that has been subjected to the ion implantation step to obtain a bonded substrate; and a delamination step of subjecting the bonded substrate to a heat treatment in an atmosphere containing hydrogen to delaminate the 4H—SiC substrate at the ion implantation layer, thereby separating the bonded substrate into a bonded substrate in which the surface layer of the 4H—SiC substrate has been transferred onto the support substrate as a 4H—SiC layer, and a delamination substrate, which is a substrate obtained after the surface layer has been delaminated from the 4H—SiC substrate. + The inventors have found that a method for manufacturing a semiconductor device can be provided that can suppress forward degradation of 4H—SiC even when using the exfoliation technique by implantation, and have completed the present invention. Furthermore, as a result of intensive research into the above-mentioned problems, the present inventors have found that a support substrate and a H + and a 4H—SiC layer containing ions including +The inventors have found that the forward degradation of 4H-SiC can also be suppressed using the exfoliation technique by implantation, and have completed the present invention. Furthermore, as a result of intensive research into the above-mentioned problems, the present inventors have discovered that a semiconductor device comprising the above-described 4H—SiC substrate can + The present inventors have found that the forward degradation of 4H-SiC can be suppressed in bonded substrates using the implantation delamination technique, resulting in high reliability, and have completed the present invention.

[0023] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. First, the configurations of a semiconductor substrate 5 and a semiconductor device 6 according to an embodiment of the present invention will be described with reference to FIG.

[0024] First, the configuration of the semiconductor substrate 5 will be described with reference to FIG. As shown in FIG. 1, the semiconductor substrate 5 according to the embodiment of the present invention includes a support substrate 3 and a H + and a 4H—SiC layer 1a containing ions including The support substrate 3 is a substrate that supports the 4H—SiC layer 1 a, and its material and dimensions can be selected appropriately as long as it has sufficient strength to support the 4H—SiC layer 1 a and does not react unintentionally with the 4H—SiC layer 1 a. Specifically, it can be bulk 4H—SiC, which is the same material as the 4H—SiC layer 1 a, but considering cost, a SiC polywafer, which is a SiC substrate that is less expensive than bulk 4H—SiC, can also be used.

[0025] The 4H-SiC layer 1a is + The layer is a single crystal layer of 4H—SiC containing ions including , and is bonded to the surface of a support substrate 3. The 4H-SiC layer 1a is + By containing ions containing H, even if there are dislocations in the 4H-SiC substrate serving as a support substrate or in the 4H-SiC layer 1a, the dislocations are prevented from expanding when current is applied. + prevents. Therefore, forward deterioration of the 4H—SiC layer 1a can be suppressed. The 4H—SiC layer 1 a may be bulk 4H—SiC as long as it is a single crystal layer, or may be an epitaxial layer in which 4H—SiC is grown on the support substrate 3 . The minimum thickness of the 4H—SiC layer 1a should be such that it can maintain its shape as a layer, can form a device, and is not lost during etching, polishing, etc. On the other hand, the maximum thickness is, for example, a thickness that does not result in any unused portion being produced when forming the device. The thickness can be, for example, 0.01 μm to 400 μm.

[0026] In this way, the semiconductor substrate 5 of the present invention is a semiconductor substrate having a 4H-SiC layer 1a bonded to the surface of the support substrate 3. + However, it prevents dislocations from expanding when current is applied. Therefore, the semiconductor substrate 5 is H + Even when manufactured using the implantation delamination technique, forward degradation can be suppressed.

[0027] Next, the configuration of the semiconductor device 6 will be described with reference to FIG. The semiconductor device 6 shown in FIG. A specific example of the semiconductor device 6 is one in which some kind of semiconductor device is formed on a semiconductor substrate 5, particularly a 4H—SiC layer 1a. For example, as shown in FIG. 1, a device is fabricated on the 4H—SiC layer 1a, which is the front surface of the semiconductor substrate 5, and then an Al / Pt electrode 7 is vapor-deposited and an Au electrode 8 is vapor-deposited on the back surface of the semiconductor substrate 5, thereby forming a Schottky barrier diode (SBD). Therefore, an example of the semiconductor device 6 including the semiconductor substrate 5 is a semiconductor substrate 5 on which a Schottky barrier diode is formed. Of course, the semiconductor device 6 can also be divided into chips by dicing.

[0028] Next, a method for manufacturing a semiconductor substrate according to an embodiment of the present invention will be described with reference to FIGS. + A manufacturing method for manufacturing the semiconductor substrate 5 shown in FIG. 1 using the injection-based delamination technique will be described as an example.

[0029] First, the case where the 4H—SiC substrate to be peeled is bulk 4H—SiC, specifically the case where the 4H—SiC layer 1a of the semiconductor substrate 5 to be manufactured is bulk 4H—SiC, will be described with reference to FIG.

[0030] This embodiment is shown in Figure 2. First, as shown in Figure 2(a), bulk 4H-SiC1 is prepared as a 4H-SiC substrate, and as shown in Figure 2(b), an ion implanter is used to implant, for example, H + The injection volume is 1.0 × 10 17 atoms / cm 2 The ion implantation layer 2 is formed by implanting ions under the conditions of (ion implantation step). 17 atoms / cm 2 By setting the ion implantation dose to 5.0×10, the bulk 4H-SiC1 can be reliably delaminated in the subsequent delamination process. 16 atoms / cm 2 On the other hand, the upper limit of the implantation amount is not particularly limited, but is, for example, the amount that can be implanted within the upper limit of the working time that can be used for the ion implantation process. The ions to be implanted are H + Ions containing H may be cluster ions, etc. + Only the HCl solution may be injected.

[0031] Next, as shown in FIG. 2(c), a substrate other than the bulk 4H-SiC1 is prepared as the support substrate 3, and as shown in FIG. 2(d), this is bonded to the ion-implanted surface of the bulk 4H-SiC1 after the implantation step to obtain a bonded substrate 10 (bonding step). As a bonding method, for example, room temperature bonding as in the prior art is performed. It is important not to raise the temperature during this bonding, and for this reason, it is preferable to adopt room temperature bonding. It is particularly important not to raise the temperature above 300°C. By not raising the temperature during bonding, H +This prevents delamination from occurring at the implanted site during the bonding process. The following explanation will be given using an example in which bonding is performed at room temperature. The support substrate 3 in this case can be single-crystal bulk 4H—SiC, which is the same material as the bulk 4H—SiC that was ion-implanted, or a SiC polywafer can be used for cost reasons. However, since the 4H—SiC layer 1a of the semiconductor substrate 5 to be manufactured is bulk 4H—SiC, the support substrate 3 is bulk 4H—SiC. Note that the surface of the bulk 4H—SiC 1 may be activated using N2 plasma or the like before bonding.

[0032] Next, as shown in FIG. 2(e), the bonded substrate 10 bonded at room temperature is heat-treated in a hydrogen-containing atmosphere at, for example, 400°C or higher, preferably 500°C, to delaminate the bulk 4H—SiC 1 at the ion-implanted layer 2. This separates the bonded substrate 10 into a bonded substrate 12 (here, semiconductor substrate 5) in which the surface layer of the bulk 4H—SiC 1 is transferred onto the support substrate 3 as a 4H—SiC layer 1a, and a delamination substrate 11, which is the substrate after the surface layer has been delaminated from the bulk 4H—SiC 1 (delamination step). Here, the H in the ion-implanted layer 2 + The thickness distribution of H + Even if the transfer is performed at a high concentration, the transferred bulk 4H-SiC1 still contains H + Therefore, by performing heat treatment in an atmosphere containing hydrogen, the outward diffusion of hydrogen can be suppressed and the implanted H + Among them, the skirt H + The upper limit of the temperature is, for example, the upper limit of the temperature that the heat treatment device can withstand and that does not alter the materials constituting the bonded substrate 12 and the separated substrate 11. Through the above steps, the semiconductor substrate 5 as the bonded substrate 12 is obtained.

[0033] In this way, in the method for manufacturing a semiconductor device of the present invention, H +When the support substrate 3 is bonded to the bulk 4H-SiC 1 into which H is implanted and then peeled off, and the surface layer of the bulk 4H-SiC 1 is transferred to the support substrate 3 to obtain the semiconductor substrate 5, the implanted H is removed by heat treatment in an atmosphere containing hydrogen. + This prevents the outward diffusion of the metal during the heat treatment for peeling. Therefore, in this method, the surface layer of the bulk 4H—SiC 1 transferred to the support substrate 3 can contain more hydrogen than when the heat treatment is not performed in a hydrogen atmosphere, and the hydrogen contained in the transferred surface layer prevents the dislocations in the semiconductor substrate 5 from expanding, thereby reducing the amount of hydrogen. + The forward degradation of the semiconductor substrate 5 can also be suppressed by the implantation-based separation technique. Furthermore, the exfoliated substrate 11, which is bulk 4H—SiC 1 after 4H—SiC has been transferred to the support substrate 3 in the delamination process, can be reused as a substrate for transferring 4H—SiC to the support substrate 3 by repeating the ion implantation process, bonding process, and delamination process again until it becomes thick enough that it cannot be further delaminated. Therefore, even if the 4H—SiC substrate is bulk 4H—SiC 1, which is expensive, no part is wasted during manufacturing, which is advantageous in terms of manufacturing costs.

[0034] In the delamination step, the bonded substrate 10 is heated for a predetermined time at a temperature lower than the temperature at which the bulk 4H—SiC 1 is delaminate in the ion-implanted layer 2, and the H implanted in the ion implantation step is delaminated. + After the inward diffusion, the bulk 4H—SiC 1 may be separated from the ion-implanted layer 2 by increasing the temperature to a temperature equal to or higher than the separation temperature. In the following description, the heat treatment in the delamination step at a temperature lower than the temperature at which the bulk 4H—SiC 1 is delaminated will be referred to as low-temperature heat treatment. By performing low-temperature heat treatment, the H + However, before the bulk 4H—SiC 1 is peeled off, it diffuses inward within the bonded substrate 10. Therefore, in the bulk 4H—SiC 1, H + can be diffused, and dislocations can be prevented from expanding over a wider range in the semiconductor substrate 5 serving as the bonded substrate 12 when a current is passed through it. The temperature of the low-temperature heat treatment is H +From the viewpoint of ensuring the inward diffusion of H, the temperature of the low-temperature heat treatment is preferably 100°C or higher. From the viewpoint of ensuring the prevention of the semiconductor substrate 5 from peeling off during the low-temperature heat treatment, the temperature of the low-temperature heat treatment is preferably less than 300°C. + To ensure the inward diffusion of H, it is preferable that the time is 10 minutes or more. + The diffusion of H is very fast and diffuses in the substrate in a short time. + However, the time is sufficient for the inward diffusion to a degree that can sufficiently prevent the expansion of dislocations when current is applied, so it is preferable to set the time to 60 minutes or less.

[0035] After the peeling process is completed, epitaxial growth of 4H—SiC is performed as needed on the 4H—SiC layer 1a of the bonded substrate 12 (here, the semiconductor substrate 5) among the substrates separated in the peeling process, to form an epitaxial layer 4 (epitaxial process) as shown in FIG. 2(f). In this way, the H transferred to the bonded substrate 12 (here, the semiconductor substrate 5) + By epitaxially growing 4H-SiC on the 4H-SiC layer 1a containing H, the dislocations in the epitaxial layer 4 are prevented from expanding when a current is applied. + can be prevented. The above is a description of the method for manufacturing a semiconductor substrate when the substrate to be peeled is bulk 4H-SiC1.

[0036] Next, a method for manufacturing a semiconductor substrate when the 4H—SiC substrate to be peeled is an epitaxial substrate, specifically when the 4H—SiC layer 1a of the semiconductor substrate 5 to be manufactured is an epitaxial layer, will be described with reference to FIG.

[0037] First, as shown in FIG. 3(a), an epitaxial substrate 5a is prepared as a 4H—SiC substrate. The epitaxial substrate 5a includes a 4H—SiC single crystal substrate 1b and a 4H—SiC epitaxial layer 1c formed on the 4H—SiC single crystal substrate 1b. Next, as shown in FIG. 3(b), ions are implanted into the surface of the epitaxial layer 1c to form an ion-implanted layer 2 (ion implantation step). The ion implantation amount may be the same as that implanted into bulk 4H—SiC 1.

[0038] Next, as shown in Fig. 3(c), a substrate other than the epitaxial substrate 5a is prepared as the support substrate 3, and as shown in Fig. 3(d), it is bonded to the surface of the epitaxial layer of the epitaxial substrate 5a after the implantation step, whereby a bonded substrate 10 is obtained (bonding step). The type of support substrate 3 and the temperature during bonding may be the same as when the substrate to be peeled is bulk 4H-SiC1.

[0039] Next, the bonded bonded substrate 10 is heat-treated in a hydrogen-containing atmosphere as shown in FIG. 3(e), thereby separating the epitaxial substrate 5a at the ion-implanted layer 2. This separates the bonded substrate 10 into a bonded substrate 12 (here, the semiconductor substrate 5) in which the surface layer of the epitaxial layer 1c has been transferred onto the support substrate 3, and a separated substrate 11, which is the substrate obtained after the surface layer has been separated from the epitaxial layer 1c of the epitaxial substrate 5a (separation step). The heat treatment temperature may be the same as when the substrate to be separated is bulk 4H—SiC1. Furthermore, low-temperature heat treatment may be performed as needed. Through the above steps, a semiconductor substrate 5 is obtained in which an epitaxial layer 1c has been transferred onto the support substrate 3. Because the epitaxial layer 1c has already been transferred onto this semiconductor substrate 5, unlike when the substrate to be peeled off is bulk 4H—SiC 1, a step of growing an epitaxial layer 4 on the semiconductor substrate 5 as shown in FIG. 2(f) is not necessarily required. Furthermore, the peeled substrate 11, which is the epitaxial substrate 5a obtained after the epitaxial layer 1c has been transferred onto the support substrate 3 in the peeling step, can be reused as a substrate for transferring the 4H—SiC epitaxial layer 1c onto the support substrate 3 by repeating the ion implantation step, bonding step, and peeling step again until the thickness of the epitaxial layer 1c reaches a point where it is no longer possible to peel off any more.

[0040] The choice of whether to use bulk 4H—SiC 1 or epitaxial substrate 5a as the 4H—SiC substrate to be peeled off may be made in consideration of the advantages of each. For example, the method of using bulk 4H-SiC as the substrate to be delaminated eliminates the need to prepare a substrate on which 4H-SiC has been epitaxially grown in advance, which is advantageous when the epitaxial growth is to be performed after the delaminated process.

[0041] On the other hand, when the substrate to be peeled is an epitaxial substrate 5a, the semiconductor substrate 5 obtained in the peeling step already has the epitaxial layer 1c transferred thereon, which is advantageous in that there is no need to grow a 4H—SiC epitaxial layer 4 on the substrate again after the peeling step. [Example]

[0042] The present invention will be specifically explained below with reference to examples, but the present invention is not limited to these examples.

[0043] A bonded substrate 10 having a 4H—SiC epitaxial layer formed on a support substrate 3 manufactured by the semiconductor substrate manufacturing method of the present invention, and H + The forward characteristics were compared between a substrate with a 4H-SiC epitaxial layer formed without implantation and a substrate with a 4H-SiC epitaxial layer formed without implantation. The specific procedure is as follows.

[0044] Example 1 As the bulk 4H-SiC1, a single crystal substrate of 4H-SiC with a diameter of 150 mm, a thickness of 355 μm, n-type, resistivity of 0.01 Ω·cm, and an off-axis angle of 4° relative to the (0001) plane was prepared. + at 50 keV with a dose of 1.0 × 10 17 atoms / cm 2The 4H-SiC substrates were then implanted at room temperature. Next, a support substrate 3 identical to the bulk 4H-SiC 1 was prepared, and its surface was activated with N2 plasma. Then, the substrates were bonded at room temperature. This was followed by a delamination process in which the 4H-SiC single crystal substrates were delaminated by heat treatment at 500°C for 30 minutes in an N2 atmosphere containing 3% hydrogen by volume, yielding bonded substrate 12 and delaminated substrate 11. Next, in the epitaxial growth process, 4H-SiC epitaxial growth was performed on the 4H-SiC layer 1a of bonded substrate 12 using a hot-wall CVD apparatus with H2 as the carrier gas and SiH4 and C3H8 as the source gases, forming epitaxial layer 4. The temperature was 1600°C, and the furnace pressure was 7 kPa. An Al / Pt electrode 7 with a diameter of 1 mm was evaporated on the epitaxial layer 4, which was the front surface of this substrate, to form a Schottky barrier diode (SBD). (An Au electrode 8 was evaporated on the back surface of the support substrate 3.) Then, a forward stress of 20 A / cm was applied according to the stress sequence shown in FIG. 2 The voltage was increased stepwise every 100 minutes from the initial value. The difference between the Vf measured initially ("Vf measurement Init.") and "Vf measurement 4" was defined as ΔVf (the current value at this time was 0.0002A), and this value was used as the value indicating the Vf fluctuation.

[0045] Example 2 A 4H-SiC single crystal substrate 1b was prepared, which was 150 mm in diameter, 355 μm thick, n-type, had a resistivity of 0.01 Ω·cm, and was 4° off-axis relative to the (0001) plane. 4H-SiC was epitaxially grown on this substrate using a hot-wall CVD apparatus with H2 as the carrier gas and SiH4 and C3H8 as the source gases, to form an epitaxial layer 1c. The temperature was 1600°C and the furnace pressure was 7 kPa. H + at 50 keV with a dose of 1.0 × 10 17 atoms / cm 2The implantation was performed at room temperature. Next, a 4H-SiC substrate was prepared as the support substrate 3, and after activating its surface with N2 plasma, bonding was performed at room temperature as the bonding process. Next, as the delamination process, heat treatment was performed at 500°C for 30 minutes in an N2 atmosphere containing 3% hydrogen by volume, to delaminate the 4H-SiC single crystal substrate 1b, obtaining a bonded substrate 12 and a delamination substrate 11. An Al / Pt electrode 7 with a diameter of 1 mm was vapor-deposited on the epitaxial layer 1c, which is the surface of the bonded substrate 12, to form a Schottky barrier diode (SBD) (an Au electrode 8 was vapor-deposited on the support substrate 3, which is the backside). Thereafter, a forward stress of 20 A / cm was applied according to the stress sequence shown in Figure 4. 2 The voltage was increased stepwise every 100 minutes from the initial value. The difference between the Vf measured initially ("Vf measurement Init.") and "Vf measurement 4" was defined as ΔVf (the current value at this time was 0.0002A), and this value was used as the value indicating the Vf fluctuation.

[0046] (Comparative Example 1) A 150 mm diameter, 355 μm thick, n-type, 0.01 Ω·cm resistivity 4H-SiC single crystal substrate with a 4° offset from the (0001) plane was prepared. A 4H-SiC epitaxial layer was formed on the substrate using a hot-wall CVD reactor with H2 as the carrier gas and SiH4 and C3H8 as the source gases. The temperature was 1600°C and the furnace pressure was 7 kPa. A 1 mm diameter Al / Pt electrode 7 was evaporated on the surface of the epitaxial layer to form a Schottky barrier diode (SBD). (An Au electrode 8 was evaporated on the backside of the 4H-SiC single crystal substrate.) A forward stress of 20 A / cm was then applied according to the stress sequence shown in Figure 4. 2 The voltage was increased stepwise every 100 minutes from the initial value. The difference between the Vf measured initially ("Vf measurement Init.") and "Vf measurement 4" was defined as ΔVf (the current value at this time was 0.0002A), and this value was used as the value indicating the Vf fluctuation.

[0047] The values ​​of ΔVf calculated in Example 1, Example 2, and Comparative Example are shown in FIG. As is clear from Fig. 5, H +In Examples 1 and 2 in which implantation was performed, ΔVf was nearly 3 V lower than in the comparative example, and Vf fluctuations as large as in the comparative example were not observed, demonstrating that forward degradation was suppressed. On the other hand, H + In the comparative example in which no implantation was performed, ΔVf was higher than in Examples 1 and 2, Vf fluctuation was observed, and forward degradation occurred.

[0048] (Comparative Examples 2 and 3) Bonded substrate 12 was obtained under the same conditions as in Example 1, except that separation was performed in an atmosphere not containing hydrogen (Comparative Example 2). Also, bonded substrate 12 was obtained under the same conditions as in Example 2, except that separation was performed in an atmosphere not containing hydrogen (Comparative Example 3). Next, forward stress was applied to bonded substrates 12 of Comparative Examples 2 and 3 under the same conditions as in Examples 1 and 2, and ΔVf was determined. As a result, ΔVf of Comparative Examples 2 and 3, in which peeling was performed in an atmosphere containing no hydrogen, was approximately 0.5 V, which was more than twice the value of Examples 1 and 2, in which peeling was performed in an atmosphere containing hydrogen, and Vf fluctuation was observed, indicating forward degradation.

[0049] As described above, according to the examples of the present invention, it was found that the forward degradation can be suppressed by manufacturing the semiconductor substrate 5 using the manufacturing method of the present invention.

[0050] The present specification includes the following aspects. [1]:H on the surface of the 4H-SiC substrate + an ion implantation step of implanting ions containing a bonding step of bonding another support substrate to the surface of the 4H—SiC substrate that has been subjected to the ion implantation step to obtain a bonded substrate; a delamination step of performing a heat treatment on the bonded substrate in an atmosphere containing hydrogen to delaminate the 4H—SiC substrate at the ion-implanted layer, thereby separating the bonded substrate into a bonded substrate in which a surface layer of the 4H—SiC substrate is transferred onto the support substrate as a 4H—SiC layer, and a delamination substrate, which is a substrate obtained after the surface layer has been delaminated from the 4H—SiC substrate; A method for manufacturing a semiconductor substrate, comprising: [2]: The peeling step is The bonded substrate is heated for a predetermined time at a temperature lower than the temperature at which the 4H—SiC substrate is peeled off from the ion-implanted layer, and the H implanted in the ion implantation step is removed. + and then increasing the temperature to a temperature equal to or higher than a delamination temperature to delaminate the 4H—SiC substrate at the ion-implanted layer. [3]: the 4H—SiC substrate is bulk 4H—SiC; The ion implantation step involves implanting H into the surface of the bulk 4H—SiC. + The method for manufacturing a semiconductor substrate according to [1] or [2] above, characterized in that it is a step of implanting ions containing [4]: After the peeling step, The method for manufacturing a semiconductor substrate according to [3] above, further comprising an epitaxial step of forming an epitaxial layer by epitaxially growing 4H—SiC on the 4H—SiC layer of the bonded substrate. [5]: The 4H—SiC substrate is an epitaxial substrate formed by epitaxially growing 4H—SiC on the surface of bulk 4H—SiC, The ion implantation step is performed by implanting H + The method for manufacturing a semiconductor substrate according to [1] or [2] above, characterized in that it is a step of implanting ions containing [6]: The ion implantation step is H + The injection volume is 5×10 16 atoms / cm 2 The method for producing a semiconductor substrate according to any one of [1] to [5] above, characterized in that the step of implanting ions is carried out so as to achieve the above. [7]: A support substrate and a H bonded to the surface of the support substrate. + and a 4H—SiC layer containing ions including [8]: A semiconductor device comprising the semiconductor substrate according to [7] above.

[0051] The present invention is not limited to the above-described embodiments, which are merely examples, and anything that has substantially the same configuration as the technical idea described in the claims of the present invention and that provides similar effects is included within the technical scope of the present invention. [Explanation of symbols]

[0052] 1...bulk 4H-SiC, 1a...4H-SiC layer, 1b...4H-SiC single crystal substrate, 1c...epitaxial layer, 2...ion-implanted layer, 3...support substrate, 4...epitaxial layer, 5...semiconductor substrate, 6...semiconductor device, 7...Al / Pt electrode, 8...Au electrode, 10...bonded substrate, 11...exfoliated substrate, 12...bonded substrate.

Claims

1. H on the surface of the 4H-SiC substrate ＋ an ion implantation step of implanting ions containing a bonding step of bonding another support substrate to the surface of the 4H—SiC substrate that has been subjected to the ion implantation step to obtain a bonded substrate; a delamination step of performing a heat treatment on the bonded substrate in an atmosphere containing hydrogen to delaminate the 4H—SiC substrate at the ion-implanted layer, thereby separating the bonded substrate into a bonded substrate in which a surface layer of the 4H—SiC substrate is transferred onto the support substrate as a 4H—SiC layer, and a delamination substrate, which is a substrate obtained after the surface layer has been delaminated from the 4H—SiC substrate; A method for manufacturing a semiconductor substrate, comprising:

2. The peeling step includes: The bonded substrate is heated for a predetermined time at a temperature lower than the temperature at which the 4H—SiC substrate is peeled off from the ion-implanted layer, and the H implanted in the ion implantation step is removed. ＋ 2. The method for manufacturing a semiconductor substrate according to claim 1, further comprising the step of: after inward diffusing ions, raising the temperature to a temperature equal to or higher than a delamination temperature to delaminate the 4H—SiC substrate at the ion-implanted layer.

3. the 4H—SiC substrate is bulk 4H—SiC; The ion implantation step is performed by implanting H into the surface of the bulk 4H—SiC. ＋ 2. The method for manufacturing a semiconductor substrate according to claim 1, wherein the step of implanting ions containing

4. After the peeling step, 4. The method for manufacturing a semiconductor substrate according to claim 3, further comprising an epitaxial step of forming an epitaxial layer by epitaxially growing 4H-SiC on the 4H-SiC layer of the bonded substrate.

5. the 4H—SiC substrate is an epitaxial substrate formed by epitaxially growing 4H—SiC on a surface of bulk 4H—SiC, The ion implantation step is performed by implanting H ＋ 2. The method for manufacturing a semiconductor substrate according to claim 1, wherein the step of implanting ions containing

6. The ion implantation step is ＋ The injection amount is 5 × 10 １６ atoms / cm ２ 6. The method for manufacturing a semiconductor substrate according to claim 1, further comprising the step of implanting ions so as to achieve the above.

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