Manufacturing method for semiconductor devices

Abstract

To provide a technology that can form a SiC layer with a uniform dopant concentration. [Solution] The method for manufacturing a semiconductor device comprises: a first step of forming an n-type SiC layer (28a) on a semiconductor substrate (28b) placed in a chamber (90) by epitaxial growth by supplying a first raw material gas containing C, a second raw material gas containing Si, and a dopant gas into a chamber (90); and a second step of increasing the thickness of the SiC layer by epitaxial growth by supplying the first raw material gas, the second raw material gas, and the dopant gas into the chamber. In the second step, the total flow rate of the first and second raw material gases is higher than in the first step, and the carbon supply ratio, which is the value obtained by dividing the flow rate of the first raw material gas by the flow rate of the second raw material gas, is lower in the second step than in the first step.

Description

Technical Field

[0001] The technology disclosed in this specification relates to a technology for epitaxially growing a SiC layer.

Background Art

[0002] Patent Document 1 discloses a technology for epitaxially growing a SiC layer. In this technology, first, a SiC layer is epitaxially grown on a SiC substrate at a first growth rate. Next, the thickness of the SiC layer is increased at a second growth rate higher than the first growth rate by epitaxial growth. In the initial stage of growth where the process conditions are not stable, the generation of defects is suppressed by growing the SiC layer at the low first growth rate. Also, after the process conditions become stable, the SiC layer is grown at the high second growth rate to efficiently grow the SiC layer.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Source gases containing Si decompose more easily than source gases containing C. Therefore, during epitaxial growth, the decomposition of Si-containing source gases proceeds faster than that of C-containing source gases. Consequently, the C / Si ratio (more specifically, the number of decomposed C atoms divided by the number of decomposed Si atoms) in the chamber is low in the early stages of epitaxial growth and increases during the growth process. A low C / Si ratio makes it easier for dopants to be incorporated into the growing SiC layer, while a high C / Si ratio makes it difficult for dopants to be incorporated. Therefore, in the technique described in Patent Document 1, a SiC layer with a high dopant concentration grows in the early stages of epitaxial growth, followed by the growth of a SiC layer with a low dopant concentration. Thus, in the technique described in Patent Document 1, it was difficult to homogenize the dopant concentration within the SiC layer. This specification provides a technique for forming a SiC layer with a uniform dopant concentration. [Means for solving the problem]

[0005] A first manufacturing method disclosed herein comprises a first step and a second step. In the first step, an n-type SiC layer (28a) is formed on a semiconductor substrate (28b) placed in a chamber (90) by epitaxial growth by supplying a first raw material gas containing C, a second raw material gas containing Si, and a dopant gas into the chamber (90). In the second step, the thickness of the SiC layer is increased by epitaxial growth by supplying the first raw material gas, the second raw material gas, and the dopant gas into the chamber. In the second step, the total flow rate of the first and second raw material gases is higher than in the first step, and the carbon supply ratio, which is the value obtained by dividing the flow rate of the first raw material gas by the flow rate of the second raw material gas, is lower than in the first step.

[0006] According to the above configuration, the carbon supply ratio in the second step is lower than in the first step. That is, the carbon supply ratio is high in the first step, which is the initial stage of epitaxial growth (i.e., the first step where the first raw material gas is difficult to decompose). Conversely, the carbon supply ratio is low in the subsequent second step (i.e., the second step where the first raw material gas is easily decomposed). Therefore, the increase in the C / Si ratio during the growth of the SiC layer can be suppressed. Consequently, a SiC layer with a uniform dopant concentration can be formed.

[0007] A second manufacturing method disclosed herein comprises a first step and a second step. In the first step, an n-type SiC layer (28a) is formed on a semiconductor substrate (28b) placed in a chamber (90) by epitaxial growth by supplying a first raw material gas containing C, a second raw material gas containing Si, a dopant gas, and a Cl-based gas containing Cl into the chamber (90). In the second step, the thickness of the SiC layer is increased by epitaxial growth by supplying the first raw material gas, the second raw material gas, the dopant gas, and the Cl-based gas into the chamber. In the second step, the total flow rate of the first and second raw material gases is higher than in the first step. In the second step, the chlorine supply ratio, which is the value obtained by dividing the flow rate of the Cl-based gas by the flow rate of the second raw material gas, is higher than in the first step.

[0008] When a chlorine (Cl)-based gas is supplied to the chamber, silicon droplets are less likely to form within the chamber. Therefore, as the flow rate of the Cl-based gas supplied to the chamber increases, the amount of decomposed Si atoms (i.e., reactive silicon material) present in the chamber increases. According to the above configuration, the chlorine supply ratio is higher in the second step than in the first step. That is, the chlorine supply ratio is low in the first step, which is the initial stage of epitaxial growth. Furthermore, the chlorine supply ratio is high in the subsequent second step. Therefore, in the first step with a low chlorine supply ratio (i.e., the first raw material gas is less likely to decompose in the first step), silicon droplets are more likely to form within the chamber, and the amount of reactive silicon material in the chamber decreases. In the subsequent second step with a high chlorine supply ratio (i.e., the first raw material gas is more likely to decompose in the second step), silicon droplets are less likely to form within the chamber, and the amount of reactive silicon material in the chamber increases. As a result, the increase in the C / Si ratio during the growth of the SiC layer can be suppressed. Therefore, a SiC layer with a uniform dopant concentration can be formed. [Brief explanation of the drawing]

[0009] [Figure 1] This is a schematic diagram of a cross-sectional view of the semiconductor device of Example 1. [Figure 2] This is a diagram illustrating the manufacturing process of the semiconductor device of Example 1. [Figure 3] This is a schematic diagram of an apparatus for epitaxial growth. [Figure 4] This is a diagram illustrating the manufacturing process of the semiconductor device of Example 1. [Figure 5] This graph shows the supply timing and supply amount of each gas in the comparative example's manufacturing method. [Figure 6] This graph shows the distribution of nitrogen concentration in the first drift region formed by the manufacturing method of the comparative example. [Figure 7] This graph shows the supply timing and supply amount of each gas in the manufacturing method of Example 1. [Figure 8] This graph shows the distribution of nitrogen concentration in the first drift region formed by the manufacturing method of Example 1. [Figure 9] This graph shows the supply timing and supply amount of each gas in the manufacturing method of Example 2. [Figure 10] This graph shows the supply timing and supply amount of each gas in the manufacturing method of Example 3. [Figure 11] This is a schematic diagram of a cross-sectional perspective view of the semiconductor device of Example 4. [Modes for carrying out the invention]

[0010] (Example 1) The semiconductor device 10 in this embodiment shown in Figure 1 is a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor). In other words, the semiconductor device 10 is a switching element. The semiconductor device 10 has a semiconductor substrate 12. The semiconductor substrate 12 is made of silicon carbide (SiC). A source electrode 80 is placed on the upper surface 12a of the semiconductor substrate 12. A drain electrode 84 is placed on the lower surface 12b of the semiconductor substrate 12.

[0011] Multiple trenches 34 are formed on the upper surface 12a of the semiconductor substrate 12. As shown in Figure 1, the multiple trenches 34 are spaced apart in the left-right direction of the paper. A gate insulating film 38 and a gate electrode 40 are formed in each trench 34. The gate insulating film 38 is made of, for example, silicon oxide and covers the inner surface of the trench 34. The gate electrode 40 is insulated from the semiconductor substrate 12 by the gate insulating film 38. The upper surface of the gate electrode 40 is covered by an interlayer insulating layer 36. The gate electrode 40 is insulated from the source electrode 80 by the interlayer insulating layer 36.

[0012] The semiconductor substrate 12 has a source region 22, a contact region 24, a body region 26, a drift region 28, and a drain region 30. Each region 22, 24, 26, 28, and 30 is made of SiC.

[0013] A plurality of source regions 22 are formed in the semiconductor substrate 12. Each source region 22 is an n-type region. Each source region 22 is exposed on the upper surface 12a of the semiconductor substrate 12. Each source region 22 makes an ohmic contact with the source electrode 80. Each source region 22 is in contact with the gate insulating film 38 at the upper end of the trench 34.

[0014] A plurality of contact regions 24 are formed in the semiconductor substrate 12. Each contact region 24 is a p-type region. Each contact region 24 is exposed on the upper surface 12a of the semiconductor substrate 12 at a position adjacent to the source region 22. Each contact region 24 makes an ohmic contact with the source electrode 80.

[0015] The body region 26 is a p-type region. The body region 26 has a lower p-type dopant concentration than each contact region 24. The body region 26 contacts the source region 22 and the contact region 24 from below. The body region 26 is in contact with the gate insulating film 38 below the source region 22.

[0016] The drift region 28 is an n-type region. The drift region 28 contacts the body region 26 from below. The drift region 28 is separated from the source region 22 by the body region 26. The drift region 28 is in contact with the gate insulating film 38 below the body region 26. The drift region 28 has a first drift region 28a and a second drift region 28b. The n-type dopant concentration of the first drift region 28a is higher than the n-type dopant concentration of the second drift region 28b.

[0017] The first drift region 28a contacts the body region 26 from below. The second drift region 28b contacts the first drift region 28a from below.

[0018] The drain region 30 is an n-type region. The n-type dopant concentration in the drain region 30 is higher than the n-type dopant concentration in the first drift region 28a. The drain region 30 is in contact with the second drift region 28b from below. The drain region 30 is exposed on the lower surface 12b of the semiconductor substrate 12. The drain region 30 makes an ohmic contact with the drain electrode 84.

[0019] Next, the operation of the semiconductor device 10 will be described. A potential higher than that of the source electrode 80 is applied to the drain electrode 84. When a potential equal to or higher than the gate threshold is applied to the gate electrode 40, a channel is formed in the body region 26 near the gate insulating film 38. Then, electrons flow from the source electrode 80, through the source region 22, the channel in the body region 26, the drift region 28, and the drain region 30, toward the drain electrode 84. That is, the semiconductor device 10 is turned on. Also, when the potential of the gate electrode 40 is lowered to a potential lower than the gate threshold, the channel disappears, the flow of electrons stops, and the semiconductor device 10 is turned off.

[0020] Subsequently, a method for manufacturing the semiconductor device 10 will be described with reference to FIGS. 2 to 4. Note that FIGS. 2 and 4 show cross-sections corresponding to FIG. 1. The semiconductor device 10 is manufactured from a semiconductor substrate 12 (that is, the semiconductor substrate 12 before processing) configured by the drain region 30. First, the second drift region 28b is epitaxially grown on the drain region 30.

[0021] Specifically, as shown in Figure 3, a semiconductor substrate 12, which is composed of a drain region 30, is placed inside the chamber 90. The semiconductor substrate 12 is heated inside the chamber 90. Then, silane gas (SiH4), propane gas (C3H8), doping gas (N2), and chlorine gas (HCl) are supplied into the chamber 90. As shown in Figure 3, the silane gas and chlorine gas are supplied into the chamber 90 along with the carrier gas (H2) through the flow path 92a. The propane gas is supplied into the chamber 90 along with the carrier gas through the flow path 92b. The doping gas is supplied into the chamber 90 along with the carrier gas through the flow path 92c. The flow rate of silane gas inside the chamber 90 is controlled by a flow control valve 94a installed between the silane gas supply source and the flow path 92a. The flow rate of chlorine gas inside the chamber 90 is controlled by a flow control valve 92d installed between the chlorine gas supply source and the flow path 92a. The flow rate of propane gas in chamber 90 is controlled by a flow control valve 94b located between the propane gas supply source and the flow path 92b. The flow rate of doping gas in chamber 90 is controlled by a flow control valve 94c located between the doping gas supply source and the flow path 92c.

[0022] Here, silane gas, propane gas, doping gas, and chlorine gas are supplied into the chamber 90 to epitaxially grow a second drift region 28b above the drain region 30, as shown in Figure 2. Chlorine gas is supplied into the chamber to accelerate the epitaxial growth of the second drift region 28b.

[0023] After the second drift region 28b is formed, the first drift region 28a is epitaxially grown on top of the second drift region 28b. The timing and amount of each gas supplied during the process of epitaxially growing the first drift region 28a on top of the second drift region 28b will be described later.

[0024] Subsequently, a body region 26, a source region 22, and a contact region 24 are formed within the semiconductor substrate 12. The body region 26, source region 22, and contact region 24 can be formed, for example, by epitaxial growth or ion implantation.

[0025] Next, as shown in Figure 4, a plurality of trenches 34 are formed by selectively etching the upper surface 12a of the semiconductor substrate 12. Here, each trench 34 is formed so that it penetrates the source region 22 and the body region 26 and reaches the drift region 28 (particularly the first drift region 28a).

[0026] Next, using techniques such as CVD (Chemical Vapor Deposition) or sputtering, the interlayer insulating layer 36, gate insulating film 38, gate electrode 40, source electrode 80, and drain electrode 84 are formed to complete the semiconductor device 10 shown in Figure 1.

[0027] Next, referring to Figures 5 to 8, the supply timing and supply amount of each gas in the process of epitaxially growing the first drift region 28a on the second drift region 28b will be explained.

[0028] First, the manufacturing method of the comparative example will be described. The graph in Figure 5 shows the supply timing and amount of each gas in the manufacturing method of the comparative example. The graph in Figure 6 shows the distribution of nitrogen concentration (i.e., n-type dopant concentration) in the first drift region 28a formed by the manufacturing method of the comparative example. The graph in Figure 6 shows the distribution of nitrogen concentration in the thickness direction of the first drift region 28a. In Figure 6, position A is the position at the start of growth, and position B is the position at the end of growth.

[0029] As shown in Figure 5, in the comparative example's manufacturing method, first, at time t1, propane gas, silane gas, doping gas, and chlorine gas are supplied into the chamber 90. Between time t1 and time t2, each gas is supplied into the chamber 90 while continuously increasing its flow rate. That is, when epitaxially growing the drift region 28a, epitaxial growth is initially carried out at a low speed, and the growth rate is gradually increased. In the early stages of growth when the growth conditions are not stable, epitaxial growth at a low speed allows for the formation of a first drift region 28a (i.e., SiC) with fewer defects. Here, propane gas, silane gas, doping gas, and chlorine gas are increased in the same ratio. That is, here, the flow rates of these gases are increased without changing the ratio of propane gas, silane gas, doping gas, and chlorine gas. From time t2 onward, the flow rate of each gas is controlled to a constant high value. Therefore, the carbon supply ratio (i.e., the value obtained by dividing the propane gas flow rate by the silane gas flow rate) does not change from time t1 to time t2 onward. From time t2 onward, since the flow rates of each gas are high, the drift region 28a can be epitaxially grown at a high growth rate. After a certain period of time has elapsed since the start of epitaxial growth, the growth conditions stabilize, so even if the drift region 28a is epitaxially grown at a high growth rate, a drift region 28a with few crystal defects can be formed. In this way, by performing epitaxial growth at a low speed in the initial stages of growth and then at a high speed after a certain period of time has elapsed, a drift region 28a with few crystal defects can be efficiently formed.

[0030] The propane gas and silane gas supplied into chamber 90 are decomposed within the chamber 90. The decomposition of propane gas generates reactive carbon material (i.e., decomposed C atoms) within chamber 90. The decomposition of silane gas generates reactive silicon material (i.e., decomposed Si atoms) within chamber 90. Hereafter, the ratio of reactive carbon material to reactive silicon material present in the chamber will be referred to as the C / Si ratio. That is, the C / Si ratio is the value obtained by dividing the number of moles of reactive carbon material by the number of moles of reactive silicon material. The binding energy of silane gas is lower than that of propane gas. In other words, silane gas decomposes more easily than propane gas. Therefore, when propane gas and silane gas are supplied into chamber 90 at a constant supply ratio, the C / Si ratio is low in the initial stages of epitaxial growth, and then increases over time.

[0031] Furthermore, the dopant concentration in the SiC layer formed by epitaxial growth (e.g., the first drift region 28a) depends on the C / Si ratio in the chamber. Specifically, the nitrogen (N) of the n-type dopant is incorporated into the SiC by coordinating with C. Therefore, the lower the C / Si ratio in the chamber (i.e., the less reactive carbon material in the gas), the easier it is for the n-type dopant to be incorporated into the SiC. In other words, the lower the C / Si ratio, the higher the n-type dopant concentration in the SiC formed by epitaxial growth.

[0032] Therefore, as shown in the graph in Figure 6, the n-type dopant concentration is high in the portion of the first drift region 28a that is formed during the early stages of epitaxial growth (i.e., the period when the C / Si ratio is low). In the portion of the first drift region 28a that is formed during the later stages of epitaxial growth (i.e., the period when the C / Si ratio is stable at a high value), the n-type dopant concentration stabilizes at a low value.

[0033] Thus, in the comparative example, a region with a high n-type dopant concentration is formed in the first drift region 28a during the initial stages of epitaxial growth. Specifically, a region with a high n-type dopant concentration is formed in the vicinity of the upper surface of the second drift region 28b within the first drift region 28a. The presence of such a region with a high n-type dopant concentration in the first drift region 28a can lead to a decrease in the breakdown voltage of the semiconductor device 10 and an increase in the leakage current of the semiconductor device 10.

[0034] Next, the manufacturing method of Example 1 will be described. As shown in the graph in Figure 7, in Example 1 as well, the flow rates of propane gas, silane gas, doping gas, and chlorine gas are continuously increased from time t1 to time t2, and from time t2 onward, the flow rates of each gas are controlled to a constant high value. Therefore, from time t2 onward, the total flow rates of propane gas and silane gas are higher than from time t1 to time t2. Consequently, the drift region 28a grows slowly from time t1 to time t2, and grows rapidly from time t2 onward (i.e., the thickness of the drift region 28a increases). Therefore, a drift region 28a with few crystal defects can be efficiently formed. In addition, in the manufacturing method of Example 1, the rate of increase of the flow rate of propane gas is lower than the rate of increase of the flow rates of silane gas, doping gas, and chlorine gas between time t1 and time t2. Therefore, the carbon supply ratio is highest at time t1, and decreases from time t1 to time t2. From time t2 onward, the carbon supply ratio is maintained at a low value. In Example 1, the ratio of the flow rates of silane gas, doping gas, and chlorine gas is constant.

[0035] As described above, in the manufacturing method of Example 1, the carbon supply ratio is high between time t1 and time t2, and low after time t2. Therefore, the decrease in the C / Si ratio can be suppressed in the early growth stage when silane gas is easily decomposed. As a result, fluctuations in the C / Si ratio can be suppressed during epitaxial growth. For example, the C / Si ratio can be kept approximately constant. As a result, as shown in the graph of Figure 8, the n-type dopant concentration in the first drift region 28a can be made uniform. As a result, a semiconductor device 10 with high breakdown voltage and low leakage current can be manufactured.

[0036] In this embodiment, propane gas and silane gas are examples of the "first raw material gas" and "second raw material gas," respectively.

[0037] The epitaxial growth between time t1 and time t2 is an example of the first step. The epitaxial growth after time t2 is an example of the second step. In the embodiments described above, the flow rates of each gas gradually increased between time t1 and time t2, but the flow rates of each gas may remain constant between time t1 and time t2. In the second step, the total flow rates of the first and second raw material gases are higher than in the first step, and the carbon supply ratio is lower in the second step than in the first step. As long as these conditions are met, the flow rates of each gas in the first and second steps may be any values.

[0038] (Example 2) Next, with reference to Figure 9, Example 2 will be described. As shown in Figure 9, in Example 2, from time t1 to time t2, the flow rates of propane gas, silane gas, doping gas, and chlorine gas are increased in stages, and from time t2 onward, the flow rates of each gas are controlled to a constant high value. Therefore, from time t2 onward, the total flow rates of propane gas and silane gas are higher than from time t1 to time t2. Consequently, the drift region 28a grows slowly from time t1 to time t2, and grows rapidly from time t2 onward (i.e., the thickness of the drift region 28a increases). Therefore, a drift region 28a with few crystal defects can be efficiently formed. Furthermore, in the manufacturing method of Example 2, the rate of increase of the flow rate of propane gas between time t1 and time t2 is lower than the rate of increase of the flow rates of silane gas, doping gas, and chlorine gas. Therefore, the carbon supply ratio is highest at time t1, and decreases from time t1 to time t2. After time t2, the carbon supply ratio is maintained at a low value. In Example 2, the ratio of the flow rates of silane gas, doping gas, and chlorine gas is constant. In the configuration of Example 2, as in Example 1, the n-type dopant concentration in the first drift region 28a can be made uniform. As a result, a semiconductor device 10 with high breakdown voltage and low leakage current can be manufactured. (Example 3) Next, with reference to Figure 10, Example 3 will be described. As shown in Figure 10, in Example 3 as well, the flow rates of propane gas, silane gas, doping gas, and chlorine gas are continuously increased from time t1 to time t2, and from time t2 onward, the flow rates of each gas are controlled to a constant high value. Therefore, the drift region 28a grows slowly from time t1 to time t2, and grows rapidly from time t2 onward (i.e., the thickness of the drift region 28a increases). Thus, a drift region 28a with few crystal defects can be efficiently formed. Furthermore, in the manufacturing method of Example 3, the rate of increase of the chlorine gas flow rate is higher than the rate of increase of the silane gas, propane gas, and doping gas flow rates between time t1 and time t2. Therefore, the chlorine supply ratio (i.e., the value obtained by dividing the chlorine gas flow rate by the silane gas flow rate) is lowest at time t1, and the chlorine supply ratio increases from time t1 to time t2. From time t2 onward, the chlorine supply ratio is maintained at a high value. In Example 3, the ratio of the flow rates of silane gas, propane gas, and doping gas remains constant.

[0039] When chlorine gas is supplied into the chamber 90, silicon droplets are less likely to form within the chamber 90. Therefore, as the flow rate of chlorine gas supplied into the chamber 90 increases, the amount of decomposed Si atoms (i.e., reactive silicon material) present in the chamber 90 increases. Consequently, a high chlorine supply ratio tends to result in a low C / Si ratio, while a low chlorine supply ratio tends to result in a high C / Si ratio. As described above, in the manufacturing method of Example 3, the chlorine supply ratio is low between time t1 and time t2, and high after time t2. Therefore, the decrease in the C / Si ratio can be suppressed in the early growth stage when silane gas is easily decomposed. Consequently, fluctuations in the C / Si ratio can be suppressed during epitaxial growth. For example, the C / Si ratio can be kept approximately constant. As a result, the n-type dopant concentration in the first drift region 28a can be made uniform. As a result, a semiconductor device 10 with high breakdown voltage and low leakage current can be manufactured.

[0040] Chlorine gas is an example of a "Cl-based gas."

[0041] The epitaxial growth between time t1 and time t2 is an example of the first step. The epitaxial growth after time t2 is an example of the second step. In the embodiments described above, the flow rates of each gas gradually increased between time t1 and time t2, but the flow rates of each gas may remain constant between time t1 and time t2. In the second step, the total flow rates of the first and second raw material gases are higher than in the first step, and the chlorine supply ratio is higher in the second step than in the first step. As long as these conditions are met, the flow rates of each gas in the first and second steps may be any values.

[0042] (Example 4) Next, with reference to Figure 11, Embodiment 4 will be described. In the semiconductor device 100 of Embodiment 4, the first drift region 28a and the second drift region 28b are equipped with a superjunction structure. The other configurations of the semiconductor device 100 of Embodiment 4 are the same as those of the semiconductor device 10 of Embodiment 1. Within the first drift region 28a, a plurality of n-type columns 150 and a plurality of p-type columns 152 are alternately arranged in the lateral direction. Within the second drift region 28b, a plurality of n-type columns 160 and a plurality of p-type columns 162 are alternately arranged in the lateral direction. The direction in which the p-type columns 152 extend and the direction in which the p-type columns 162 extend intersect. The p-type columns 162 are connected to the body region 126 via the p-type columns 152.

[0043] In the manufacturing method of the semiconductor device 100 of Example 4, first, an n-type second drift region 28b is formed by epitaxial growth in the same manner as in Example 1. Next, a p-type column 162 is formed by selectively injecting a p-type dopant into the second drift region 28b. The area of ​​the second drift region 28b in which the p-type column 162 was not formed becomes the n-type column 160. Next, a first drift region 28a is grown on the second drift region 28b in the same manner as in Example 1 (or Example 2 or Example 3). Thus, a first drift region 28a with a uniform n-type dopant concentration is formed. Next, a p-type column 152 is formed by selectively injecting a p-type dopant into the first drift region 28a. The area of ​​the first drift region 28a in which the p-type column 152 was not formed becomes the n-type column 150.

[0044] The first drift region 28a is formed so that the amount of p-type dopant in the p-type column 152 and the amount of n-type dopant in the n-type column 150 are balanced. If, during epitaxial growth of the first drift region 28a, a region with a high concentration of n-type dopant is formed as shown in Figure 6, it becomes difficult to balance the dopant between the n-type column 150 and the p-type column 152. In this case, the breakdown voltage of the semiconductor device 100 will be low. On the other hand, in the manufacturing method of Example 4, the concentration of n-type dopant in the first drift region 28a can be made uniform. Therefore, it is possible to balance the dopant between the n-type column 150 and the p-type column 152, and a semiconductor device 100 with high breakdown voltage can be manufactured.

[0045] The configurations of the manufacturing methods disclosed herein are listed below. (Composition 1) A method for manufacturing a semiconductor device, A first step involves supplying a first raw material gas containing C, a second raw material gas containing Si, and a dopant gas into a chamber (90) to form an n-type SiC layer (28a) on a semiconductor substrate (28b) placed in the chamber by epitaxial growth. A second step involves supplying the first raw material gas, the second raw material gas, and the dopant gas into the chamber to increase the thickness of the SiC layer by epitaxial growth. Equipped with, In the second step, the total flow rates of the first and second raw material gases are higher than in the first step. A manufacturing method wherein the carbon supply ratio, which is the value obtained by dividing the flow rate of the first raw material gas by the flow rate of the second raw material gas, is lower in the second step than in the first step. (Configuration 2) A method for manufacturing a semiconductor device, A first step involves supplying a first raw material gas containing C, a second raw material gas containing Si, a dopant gas, and a Cl-based gas containing Cl into a chamber (90) to form an n-type SiC layer (28a) on a semiconductor substrate (28b) placed in the chamber by epitaxial growth. A second step involves supplying the first raw material gas, the second raw material gas, the dopant gas, and the Cl-based gas into the chamber to increase the thickness of the SiC layer by epitaxial growth. Equipped with, In the second step, the total flow rates of the first and second raw material gases are higher than in the first step. A manufacturing method wherein the chlorine supply ratio, which is the value obtained by dividing the flow rate of the Cl-based gas by the flow rate of the second raw material gas, is higher in the second step than in the first step.

[0046] The specific examples of the technology disclosed in this specification have been described in detail above, but these are merely illustrative and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes to the specific examples described above. The technical elements described in this specification or drawings exhibit technical usefulness individually or in various combinations, and are not limited to the combinations described in the claims at the time of filing. Furthermore, the technology illustrated in this specification or drawings can achieve multiple objectives simultaneously, and achieving even one of these objectives itself constitutes technical usefulness. [Explanation of Symbols]

[0047] 10: Semiconductor device, 12: Semiconductor substrate, 22: Source region, 24: Contact region, 26: Body region, 28: Drift region, 28a: First drift region, 28b: Second drift region, 30: Drain region, 34: Trench, 36: Interlayer insulating layer, 38: Gate insulating film, 40: Gate electrode, 80: Source electrode, 84: Drain electrode

Claims

1. A method for manufacturing a semiconductor device, A first step involves supplying a first raw material gas containing C, a second raw material gas containing Si, and a dopant gas into a chamber (90) to form an n-type SiC layer (28a) on a semiconductor substrate (28b) placed in the chamber by epitaxial growth. A second step involves supplying the first raw material gas, the second raw material gas, and the dopant gas into the chamber to increase the thickness of the SiC layer by epitaxial growth. Equipped with, In the second step, the total flow rates of the first and second raw material gases are higher than in the first step. A manufacturing method wherein the carbon supply ratio, which is the value obtained by dividing the flow rate of the first raw material gas by the flow rate of the second raw material gas, is lower in the second step than in the first step.

2. A method for manufacturing a semiconductor device, A first step involves supplying a first raw material gas containing C, a second raw material gas containing Si, a dopant gas, and a Cl-based gas containing Cl into a chamber (90) to form an n-type SiC layer (28a) on a semiconductor substrate (28b) placed in the chamber by epitaxial growth. A second step involves supplying the first raw material gas, the second raw material gas, the dopant gas, and the Cl-based gas into the chamber to increase the thickness of the SiC layer by epitaxial growth. Equipped with, In the second step, the total flow rates of the first and second raw material gases are higher than in the first step. A manufacturing method wherein the chlorine supply ratio, which is the value obtained by dividing the flow rate of the Cl-based gas by the flow rate of the second raw material gas, is higher in the second step than in the first step.

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