Manufacturing method for semiconductor devices

Abstract

To provide a method for manufacturing a semiconductor device in which a semiconductor substrate is less likely to rupture even when heat processing is performed using β-gallium oxide as the semiconductor substrate.SOLUTION: A method for manufacturing a semiconductor device performs the processing for: preparing a semiconductor substrate 30 composed of β-gallium oxide; arranging the semiconductor substrate 30 on a susceptor 20 arranged in a chamber 10; sealing the chamber 10; performing heat processing for lowering the temperature of the semiconductor substrate 30 after increasing the temperature of the semiconductor substrate 30 by heat transfer by adjusting the temperature of the susceptor 20; and putting the semiconductor device into a state in which the substrate 30 can be extracted from the chamber 10 by releasing the sealing of the chamber 10. The step of preparing the semiconductor substrate 30 prepares a semiconductor substrate where one surface 30a or the other surface 30b is within 45 to 90° with respect to a (100) surface or a (001) surface. The heat processing increases the semiconductor substrate 30 to 300°C or higher by increasing the temperature of the susceptor 20 on the condition that a temperature increase rate of the susceptor 20 becomes 100°C / min or lower.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a semiconductor device including heat-treating a β-gallium oxide (i.e., Ga2O3) substrate.

Background Art

[0002] Conventionally, in a method for manufacturing a semiconductor device, heat treatment has been proposed for activating impurities implanted by ion implantation and for recovering defects in a semiconductor substrate. However, when performing heat treatment, if the temperature difference between one surface and the other surface of the semiconductor substrate is large, the semiconductor substrate may warp and break. For this reason, for example, when using a silicon substrate as the semiconductor substrate and heat-treating this semiconductor substrate, a method has been proposed in which the semiconductor substrate is rapidly heated to about 500°C and then slowly heated to about 1000°C.

[0003] By the way, in recent years, β-gallium oxide having a larger bandgap energy than silicon carbide or the like has been attracting attention, and it has been studied to form a semiconductor device including a semiconductor element such as a MOSFET using a semiconductor substrate made of β-gallium oxide. Note that MOSFET is an abbreviation for metal oxide semiconductor field effect transistor.

[0004] Here, although research on β-gallium oxide is underway, it has been reported that its crystal structure is monoclinic and its thermal conductivity is about 1 / 6 lower than that of silicon. Further, for example, Non-Patent Document 1 suggests that β-gallium oxide has a steep decrease in the linear expansion coefficient in the

[0100] direction around 300°C.

Prior Art Documents

Non-Patent Documents

[0005]

Non-Patent Document 1

[0006] The inventors of the present invention are considering constructing a semiconductor device using β-gallium oxide as a semiconductor substrate. However, as described above, β-gallium oxide has low thermal conductivity, so a temperature difference is likely to occur between one side and the other side of the semiconductor substrate during heat treatment. In addition, the coefficient of linear expansion of β-gallium oxide in the

[0100] direction decreases sharply at around 300°C. When β-gallium oxide is used as a semiconductor substrate, if one or the other side of the semiconductor substrate is within the range of 45 to 90° with respect to the (100) plane, or within the range of 45 to 90° with respect to the (001) plane, then the

[0100] direction becomes the plane direction of the semiconductor substrate.

[0007] Therefore, when β-gallium oxide is used as a semiconductor substrate, and one or the other surface of the semiconductor substrate is within the range of 45 to 90° with respect to the (100) surface or the (001) surface, if the semiconductor substrate is subjected to heat treatment at 300°C or higher in the same manner as when the semiconductor substrate is a silicon substrate, the following phenomena are likely to occur. That is, due to the low thermal conductivity, the temperature difference between one surface and the other surface of the semiconductor substrate tends to become large, and because the

[0100] direction is the plane direction of the semiconductor substrate, there is a high possibility that the semiconductor substrate will warp and break.

[0008] In view of the above, the present invention aims to provide a method for manufacturing a semiconductor device that uses β-gallium oxide as a semiconductor substrate and is less prone to fracture even when subjected to heat treatment. [Means for solving the problem]

[0009] Claim 1, for achieving the above objective, is a method for manufacturing a semiconductor device, comprising: preparing a semiconductor substrate (30) made of β-gallium oxide; placing the semiconductor substrate on a susceptor (20) placed in a chamber (10); sealing the chamber; performing a heat treatment to raise the temperature of the semiconductor substrate by heat transfer and then lower the temperature of the semiconductor substrate by adjusting the temperature of the susceptor; and releasing the seal on the chamber so that the semiconductor substrate can be removed from the chamber, wherein in preparing the semiconductor substrate, one side (30a) or the other side (30b) is within the range of 45 to 90° with respect to the (100) plane, or within the range of 45 to 90° with respect to the (001) plane; in placing the semiconductor substrate, the other side is placed facing the susceptor; and in the heat treatment, the susceptor is heated under conditions where the heating rate of the susceptor is 100°C / min or less, thereby raising the temperature of the semiconductor substrate to 300°C or higher. By cooling the susceptor under conditions where the cooling rate of the susceptor is 100°C / min or less, the semiconductor substrate is cooled to 300°C or less, thereby preparing a semiconductor substrate in which the thickness between one surface and the other is 400 μm or less. .

[0010] According to this method, when heating a semiconductor substrate, it becomes less likely for a temperature difference to occur between one side of the substrate and the other side, thereby suppressing the fracture of the semiconductor substrate.

[0011] The reference numerals in parentheses attached to each component indicate an example of the correspondence between that component and the specific components described in the embodiments described later. [Brief explanation of the drawing]

[0012] [Figure 1] This is a cross-sectional view showing the configuration of a heating device for performing heat treatment in the first embodiment. [Figure 2] This figure shows the relationship between elapsed time and the susceptor's set temperature. [Modes for carrying out the invention]

[0013] The embodiments of the present invention will be described below with reference to the drawings. In the following embodiments, parts that are the same or equivalent to each other will be denoted by the same reference numerals.

[0014] (First Embodiment) The first embodiment will be described with reference to the drawings. Below, a method for manufacturing a semiconductor device, including a heat treatment of the semiconductor substrate, will be described using β-gallium oxide as the semiconductor substrate.

[0015] First, the configuration of the heating device 1 that performs the heat treatment will be explained with reference to Figure 1. As shown in Figure 1, the heating device 1 includes a chamber 10 and a susceptor 20.

[0016] Chamber 10 is connected to an exhaust pump (not shown) and the like, so that the inside is maintained at a predetermined pressure. Chamber 10 is also equipped with a supply port 11 for supplying atmospheric gas and an exhaust port 12 for exhausting the atmospheric gas.

[0017] The susceptor 20 is used to raise (i.e., heat) and lower (i.e., cool) the semiconductor substrate 30, which has one surface 30a and the other surface 30b. Specifically, the susceptor 20 is configured to raise and lower the temperature of the semiconductor substrate 30 by heat transfer, and is made of a material with high thermal conductivity, such as graphite or silicon carbide. The temperature of the susceptor 20 is controlled by methods such as lamp heating or induction heating.

[0018] The above describes the configuration of the heating device 1 in this embodiment. Next, a method for manufacturing a semiconductor device, including a heat treatment using the heating device 1, will be described.

[0019] First, prepare a semiconductor substrate 30 made of gallium beta - oxide, in which the

[0100] direction is included in the plane direction of one surface 30a or the other surface 30b. More specifically, as the semiconductor substrate 30, prepare one made of gallium beta - oxide, where one surface 30a or the other surface 30b is within the range of 45 to 90° with respect to the (100) plane, or one surface 30a or the other surface 30b is within the range of 45 to 90° with respect to the (001) plane.

[0020] Note that the semiconductor substrate 30 may be one in which impurities constituting an impurity layer for forming a semiconductor element are ion - implanted. Examples of the impurities to be ion - implanted include nitrogen, zinc, magnesium, etc. when forming a p - type impurity layer. Also, the semiconductor substrate 30 may be one in which a trench for forming a trench gate structure is formed from the side of one surface 30a.

[0021] Then, arrange the semiconductor substrate 30 such that the other surface 30b faces the susceptor 20. After that, seal the chamber 10 and set the pressure inside the chamber 10 to a predetermined pressure by an exhaust pump (not shown).

[0022] Next, adjust the temperature of the susceptor 20 and perform a heat treatment in which the semiconductor substrate 30 is heated to 300°C or higher by heat transfer from the susceptor 20 and then cooled by heat transfer to the susceptor 20. In this case, specifically as will be described later, when heating the semiconductor substrate 30, by specifying the heating rate of the susceptor 20, it is made difficult for a temperature difference to occur between one surface 30a and the other surface 30b of the semiconductor substrate 30. Similarly, specifically as will be described later, when cooling the semiconductor substrate 30, by specifying the cooling rate of the susceptor 20, it is made difficult for a temperature difference to occur between one surface 30a and the other surface 30b of the semiconductor substrate 30.

[0023] When performing the heat treatment, a predetermined atmosphere gas is supplied into the chamber 10 from the supply port 11, and the atmosphere gas is exhausted from the exhaust port 12 while the heat treatment is being carried out. For example, in the case of a heat treatment for oxidizing the semiconductor substrate 30, the heat treatment is performed while supplying oxygen as the atmosphere gas. Also, for example, in the case of a heat treatment for diffusing impurities implanted by ion implantation without oxidizing the semiconductor substrate 30, the heat treatment is performed while supplying nitrogen or argon as the atmosphere gas.

[0024] After the susceptor 20 is cooled to a predetermined temperature, the sealed state of the chamber 10 is released so that the semiconductor substrate 30 can be taken out.

[0025] After that, a predetermined manufacturing process is carried out, and a desired semiconductor device is manufactured by forming predetermined electrodes and the like.

[0026] The above is the manufacturing method of the semiconductor device including the heat treatment in the present embodiment. Next, the results actually obtained by the present inventors will be described.

[0027] First, as the semiconductor substrate 30, one with a size of 2 inches and a thickness of 400 μm is prepared. The semiconductor substrate 30 is made of β-gallium oxide as described above and includes the

[0100] direction in the surface direction of one surface 30a or the other surface 30b.

[0028] Then, the present inventors performed the heat treatment as shown in FIG. 2. In FIG. 2, the flow rate of nitrogen gas as the atmosphere gas is set to 2 slm.

[0029] Specifically, when raising the temperature of the semiconductor substrate 30, the heating rate of the susceptor 20 was set to 100°C / min to ensure sufficient heat transfer time within the semiconductor substrate 30 and to prevent a large temperature difference from occurring between one side 30a and the other side 30b of the semiconductor substrate 30. The temperature of the susceptor 20 was then maintained at 1000°C for approximately 10 minutes. Subsequently, when lowering the temperature of the semiconductor substrate 30, the cooling rate of the susceptor 20 was set to 100°C / min to prevent a large temperature difference from occurring between one side 30a and the other side 30b of the semiconductor substrate 30. After lowering the temperature of the susceptor 20 to below 100°C, the chamber 10 was released from its sealed state and the semiconductor substrate 30 was removed.

[0030] Furthermore, in this embodiment, the heating process is performed while supplying an atmospheric gas to the chamber 10, but the atmospheric gas is used to prevent one side 30a of the semiconductor substrate 30 from being cooled. In this embodiment, the semiconductor substrate 30 is exposed to the atmospheric gas heated by the heat of the susceptor 20. Specifically, according to the inventors' studies, it has been confirmed that by controlling the flow rate of the supplied atmospheric gas so that the gas exchange in the chamber 10 per unit minute is 100% or less of the volume in the chamber 10, the atmospheric gas makes it difficult for one side 30a of the semiconductor substrate 30 to be cooled. In this embodiment, the volume of the chamber 10 is 10 L and the flow rate of nitrogen gas is 2 s lm, so the flow rate of nitrogen gas is 100% or less of the volume in the chamber 10.

[0031] The inventors have confirmed that when the semiconductor substrate 30 was subjected to heat treatment under the above conditions, the semiconductor substrate 30 did not fracture.

[0032] On the other hand, in the comparative example, the temperature of the susceptor 20 was maintained at 1000°C for 10 minutes with a heating rate of 6000°C / min. Also in the comparative example, the temperature of the susceptor 20 was lowered to 300°C with a cooling rate of 6000°C / min, and the semiconductor substrate 30 was removed when it was ready to be removed.

[0033] The inventors confirmed that when they performed a heat treatment on a semiconductor substrate 30 under the conditions of the above comparative example, the semiconductor substrate 30 fractured. Upon further investigation of this fracture, the inventors confirmed that the fracture occurred along the

[0010] direction. This

[0010] direction is tilted by 90 degrees from the

[0100] direction, which is prone to strain due to temperature differences between one surface 30a and the other surface 30b. Therefore, it is considered that the coefficient of linear expansion in the

[0100] direction has an influence when heat treating β-gallium oxide.

[0034] As described above, in this embodiment, the semiconductor substrate 30 is heated under conditions where the heating rate of the susceptor 20 is 100°C / min or less. Therefore, when heating the semiconductor substrate 30, it is less likely that a temperature difference will occur between one side 30a and the other side 30b of the semiconductor substrate 30, and fracture of the semiconductor substrate 30 can be suppressed.

[0035] (1) In this embodiment, the semiconductor substrate 30 is cooled under conditions that the cooling rate of the susceptor 20 is 100°C / min or less. Therefore, when the semiconductor substrate 30 is cooled, it is less likely that a temperature difference will occur between one side 30a and the other side 30b of the semiconductor substrate 30, and fracture of the semiconductor substrate 30 can be suppressed.

[0036] (2) In this embodiment, when the semiconductor substrate 30 is prepared to be removed, the susceptor 20 is kept below 100°C. Therefore, when removing the semiconductor substrate 30, it is possible to suppress the fracture of the semiconductor substrate 30 due to the temperature difference with the outside air.

[0037] (3) In this embodiment, the semiconductor substrate 30 is exposed to a heated atmospheric gas. Therefore, it is possible to suppress the cooling of one side 30a of the semiconductor substrate 30 by the atmospheric gas, and to suppress a large temperature difference between the one side 30a and the other side 30b.

[0038] (4) In this embodiment, the flow rate of the atmospheric gas is controlled so that the gas exchange in the chamber 10 per unit minute is 100% or less of the volume in the chamber 10. Therefore, it is possible to suppress the cooling of one side 30a of the semiconductor substrate 30 by the atmospheric gas, and to suppress a large temperature difference between the one side 30a and the other side 30b.

[0039] (5) In this embodiment, the semiconductor substrate 30 is 2 inches in diameter and has a thickness of 400 μm, thereby suppressing fracture during heat treatment. Note that the thinner the semiconductor substrate 30, the less likely it is that a temperature difference will occur between one surface 30a and the other surface 30b. In other words, the above results will be the same if the semiconductor substrate 30 has a thickness of 400 μm or less.

[0040] (Other embodiments) This disclosure is described in accordance with embodiments, but it is understood that this disclosure is not limited to such embodiments or structures. This disclosure also includes various modifications and variations within the scope of equivalents. In addition, various combinations and forms, as well as other combinations and forms that include only one, more, or fewer of those elements, fall within the scope and idea of ​​this disclosure.

[0041] For example, in the first embodiment described above, the atmospheric gas may be heated outside the chamber 10 and supplied into the chamber 10. Furthermore, the flow rate and other parameters of the atmospheric gas can be appropriately changed if it is necessary to prevent one side 30a of the semiconductor substrate 30 from being cooled by the atmospheric gas.

[0042] Furthermore, in the first embodiment described above, the size and thickness of the semiconductor substrate 30 can be changed as appropriate.

[0043] [Disclosure of the Invention] [First point of view] A method for manufacturing a semiconductor device, Prepare a semiconductor substrate (30) composed of β-gallium oxide, The semiconductor substrate is placed on a susceptor (20) located inside the chamber (10), To seal the chamber, By adjusting the temperature of the susceptor, a heating process is performed in which the semiconductor substrate is heated by heat transfer and then cooled down. The sealing of the chamber is released so that the semiconductor substrate can be removed from the chamber. The semiconductor substrate is prepared such that one side (30a) or the other side (30b) is within a range of 45 to 90° with respect to the (100) plane, or within a range of 45 to 90° with respect to the (001) plane. In arranging the semiconductor substrate, the other side is positioned to face the susceptor. A method for manufacturing a semiconductor device, wherein in the heat treatment, the susceptor is heated under conditions that the heating rate of the susceptor is 100°C / min or less, thereby raising the temperature of the semiconductor substrate to 300°C or higher.

[0044] [Second perspective] The method for manufacturing a semiconductor device according to the first aspect, wherein in the heat treatment, the susceptor is cooled under conditions that the cooling rate of the susceptor is 100°C / min, thereby lowering the temperature of the semiconductor substrate to 300°C or below.

[0045] [Third perspective] A method for manufacturing a semiconductor device according to the first or 22nd aspect, wherein the susceptor is heated to 100°C or below in order to make the semiconductor substrate removable.

[0046] [Fourth perspective] A method for manufacturing a semiconductor device according to any one of the first to third aspects, wherein the heat treatment is performed while supplying an atmospheric gas into the chamber and exhausting the atmospheric gas, and the semiconductor substrate is exposed to the heated atmospheric gas.

[0047] [Fifth perspective] The method for manufacturing a semiconductor device according to a fourth aspect, wherein the heat treatment adjusts the flow rate of the atmospheric gas so that the gas exchange in the chamber with respect to the atmospheric gas per unit minute is 100% or less of the volume in the chamber.

[0048] [Sixth perspective] A method for manufacturing a semiconductor device according to any one of the first to fifth aspects, wherein the semiconductor substrate is 2 inches in size.

[0049] [Perspective 7] A method for manufacturing a semiconductor device according to any one of the first to sixth aspects, wherein the semiconductor substrate is prepared such that the thickness between one surface and the other surface is 400 μm or less. [Explanation of Symbols]

[0050] 10 Chambers 20 Susceptors 30 Semiconductor substrates

Claims

1. A method for manufacturing a semiconductor device, A semiconductor substrate (30) composed of β-gallium oxide is prepared, The semiconductor substrate is placed on a susceptor (20) located inside the chamber (10), To seal the chamber, By adjusting the temperature of the susceptor, a heating process is performed in which the semiconductor substrate is heated by heat transfer and then cooled down. The sealing of the chamber is released so that the semiconductor substrate can be removed from the chamber. The semiconductor substrate is prepared such that one side (30a) or the other side (30b) is within the range of 45 to 90° with respect to the (100) plane, or within the range of 45 to 90° with respect to the (001) plane. In arranging the semiconductor substrate, the other side is positioned to face the susceptor. In the aforementioned heat treatment, the semiconductor substrate is heated to 300°C or higher by raising the susceptor's heating rate to 100°C / min or less, and the semiconductor substrate is cooled to 300°C or lower by lowering the susceptor's heating rate to 100°C / min or less. A method for manufacturing a semiconductor device, wherein the semiconductor substrate is prepared such that the thickness between one surface and the other surface is 400 μm or less.

2. The method for manufacturing a semiconductor device according to claim 1, wherein the susceptor is heated to 100°C or below in order to make the semiconductor substrate removable.

3. The method for manufacturing a semiconductor device according to claim 1, wherein the heat treatment is performed while supplying an atmospheric gas into the chamber and exhausting the atmospheric gas, and the semiconductor substrate is exposed to the heated atmospheric gas.

4. The method for manufacturing a semiconductor device according to claim 3, wherein the heat treatment involves adjusting the flow rate of the atmospheric gas so that the gas exchange in the chamber with respect to the atmospheric gas per unit minute is 100% or less of the volume in the chamber.

5. The method for manufacturing a semiconductor device according to claim 1, wherein the semiconductor substrate is 2 inches in size.

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