Silicon (110) substrate and method for processing silicon (110) substrate

Abstract

The present invention provides a silicon (110) substrate which is characterized in that the silicon (110) substrate has an off angle, and the off angle is more than 2° and less than 36°. This configuration makes it possible to provide: a silicon (110) substrate in which the occurrence of protruding defects on the surface is suppressed; and a method for processing a silicon (110) substrate, with which the occurrence of protruding defects on the surface is suppressed.

Description

Silicon (110) substrate and method for processing silicon (110) substrate

[0001] The present invention relates to a silicon (110) substrate and a method for processing a silicon (110) substrate.

[0002] Instead of the FinFET (Fin Field Effect Transistor) structure currently adopted in logic ICs, in the post-next generation, GAA (Gate All Around) and further CFET (Complementary Field Effect Transistor) in which NMOS (N-type Metal-Oxide-Semiconductor) and PMOS (P-type Metal-Oxide-Semiconductor) are stacked have been proposed and actively researched and developed. At this time, as a method for improving hole mobility, it is considered to use silicon (110) (hereinafter also referred to as Si(110)) (Non-Patent Document 1).

[0003] However, it has been pointed out that the Si(110) substrate has problems of large surface roughness and haze (Non-Patent Document 1). Here, haze is also referred to as the degree of cloudiness of the surface, and represents the surface roughness in terms of the degree of light scattering. The larger the haze, the rougher the surface. Also, the most stable structure of the outermost surface of Si(110) was confirmed relatively recently (Non-Patent Documents 2 and 3).

[0004] Further, according to the descriptions of Non-Patent Documents 2 and 3, the 16×2 domain, which is the most stable structure, undergoes a phase conversion depending on the temperature, and the structure changes in the range of 600 to 800°C. This temperature range, for example, is such that the temperature during hydrogen bake for growing a silicon epitaxial layer (hereinafter simply referred to as an epi layer or an epitaxial layer) and the subsequent silicon epitaxial growth exceeds 1,000°C. Once it becomes a 1×1 structure, a phase change occurs during cooling, and the surface structure also changes depending on the time passed during cooling. Also, for example, things like SiGe stacked in GAA or CFET often use this temperature range, making it more difficult to understand the surface structure.

[0005] The unique surface structure of this Si(110) plane also affects the surface structure after heat treatment. Because the most stable structure is a special 16×2 structure, there are unstable regions (described as disorder regions in Non-Patent Literature 2) adjacent to the most stable 16×2 structure.

[0006] Furthermore, Patent Document 1 and Non-Patent Document 4 disclose that silicon (551) has better surface roughness than silicon (110) and that hole mobility can be improved, and propose its application.

[0007] Furthermore, Non-Patent Document 5 summarizes step motion (i.e., motion of silicon surface atoms), exemplified by step bunching (reconstruction of surface atoms). According to this document, there is an extra energy barrier for diffusion across steps, and this difference in thermal stability (asymmetry) due to the steps leads to step bunching. The presence of a diffusion barrier at the step edge results in differences in crystallization and diffusion rates between adsorbed atoms on the upper terrace and those on the lower terrace (Erlik-Schwebel effect).

[0008] When the energy barrier for diffusion across the step edge is large, crystallization preferentially occurs from the lower side of the step, and the terrace on the upper side of the step behaves like a two-dimensional crystal within the diffusion field of adsorbed atoms. This causes the linear step to meander. This phenomenon is called Bales-Zangwill destabilization.

[0009] Japan Society of Applied Physics, Industry-Academia Collaboration Committee on Crystal Growth, Processing and Evaluation of Semiconductors, 1st Workshop Meeting "Crystal Technology Supporting the Resurgence of Semiconductors," Yamada et al., "Fabrication of Si(110)-16×2 Single Domain Surface," Surface Science, 29(7), 401 (2008) Miyaji et al., "Observation of Si(110) Reconstructed Surfaces by Ultra-High Vacuum Non-Contact Atomic Microscope," Journal of the Japan Institute of Metals, 72(4), 290 (2008) Teramoto, "Atomic-Order Flat Silicon Surface and Properties of MOS Devices Formed Thereon," HORIBA Tech. Reprot, 51, 44 (2018) Ueba, "Fundamentals of Epitaxial Growth - Strain, Diffusion, and Step Motion -," Journal of the Japan Society for Crystal Growth, 43(4), 213 (2016)

[0010] Japanese Patent Publication No. 2004-265918

[0011] Thus, although the surface of Si(110) substrates has a very complex shape and problems such as high surface roughness and haze have been pointed out, they are not systematically understood, and the mechanism by which surface protrusion defects occur is not clear. As a result, there is a problem in that no method for suppressing the occurrence of surface protrusion defects is known.

[0012] The present invention has been made to solve the above problems, and aims to provide a silicon (110) substrate in which the occurrence of protruding surface defects is suppressed, and a method for processing a silicon (110) substrate in which the occurrence of protruding surface defects is suppressed.

[0013] To solve the above problems, the present invention provides a silicon (110) substrate characterized in that the silicon (110) substrate has an off-angle, and the off-angle is greater than 2° and less than 36°.

[0014] With such a silicon (110) substrate, the off-angle is greater than 2° and less than 36°, resulting in a low surface energy and a stable surface, which suppresses the occurrence of surface protrusion defects.

[0015] Furthermore, it is preferable that the silicon (110) substrate is an annealed substrate that has been heat-treated at 1000°C or higher, and that no protruding defects are detected.

[0016] Such an annealed substrate is preferable because no surface protrusion defects are detected even after heat treatment.

[0017] Furthermore, it is preferable that the annealed substrate is cooled at a rate of 1000°C / min or more in the temperature range of 540 to 640°C after the heat treatment at 1000°C or higher.

[0018] If the annealed substrate is cooled at such a rate, the phase transition temperature will be passed quickly during cooling, further suppressing the generation of surface protrusion defects.

[0019] To solve the above problems, the present invention provides a method for processing a silicon (110) substrate, characterized by preparing a silicon (110) substrate having an off-angle greater than 2° and less than 36°, and then subjecting the silicon (110) substrate having the off-angle to a heat treatment of 1000°C or higher to produce an annealed substrate.

[0020] With this silicon (110) substrate processing method, by preparing a silicon (110) substrate with an off-angle greater than 2° and less than 36°, the surface energy can be reduced, resulting in a stable surface and suppressing the occurrence of surface protrusion defects. Furthermore, by using an annealed substrate that has been heat-treated at 1000°C or higher, it is possible to further prevent the detection of protrusion defects.

[0021] Furthermore, it is preferable that the heat treatment is an etching process that removes the native oxide film of the silicon (110) substrate using an etching gas, and that the pressure of the gas be 5 Torr or higher.

[0022] With this etching gas pressure, the evaporation of atoms during etching is suppressed due to the relatively high pressure, thus further suppressing the generation of minute surface protrusion defects caused by atomic evaporation.

[0023] Furthermore, the heat treatment is preferably an etching process that removes the native oxide film of the silicon (110) substrate using an etching gas, and during the cooling process, it is preferable to cool the temperature range of 540 to 640°C at a rate of 1000°C / min or more.

[0024] If the etched substrate is cooled at such a rate, the phase transition temperature can be passed quickly during cooling, further suppressing the occurrence of surface protrusion defects.

[0025] Furthermore, it is preferable that the heat treatment is an etching process that removes the native oxide film of the silicon (110) substrate using an etching gas, and that the storage temperature after cooling in the etching process be 540°C or lower with a temperature variation of ±30°C or less.

[0026] By using such storage temperatures, the occurrence of minute surface protrusion defects during storage can be further suppressed.

[0027] Furthermore, the heat treatment is an etching process that removes the native oxide film of the silicon (110) substrate using an etching gas, and during cooling in the etching process, it is preferable to keep the temperature difference within the surface of the silicon (110) substrate within ±10°C when the average surface temperature of the silicon (110) substrate is in the range of 630°C to 750°C.

[0028] Such an in-plane temperature difference can further suppress the generation of minute protrusion-like defects within the plane.

[0029] Furthermore, it is preferable that the heat treatment is an epitaxial treatment in which epitaxial growth is carried out on the silicon (110) substrate using gas, and that the pressure of the gas be 5 Torr or less.

[0030] With such a gas pressure, the adhesion of atoms to the substrate surface can be suppressed to some extent due to the relatively low pressure, preventing growth from becoming too rapid. This further suppresses the generation of minute surface protrusion defects caused by excessive growth.

[0031] Furthermore, the heat treatment is preferably an epitaxial treatment in which epitaxial growth is carried out on the silicon (110) substrate using gas, and during cooling in the epitaxial treatment, it is preferable to cool in the temperature range of 540 to 640°C at a rate of 1000°C / min or more.

[0032] If the substrate after epitaxial treatment is cooled at such a rate, the phase transition temperature can be passed quickly during cooling, further suppressing the generation of protruding surface defects.

[0033] Furthermore, it is preferable that the heat treatment is an epitaxial treatment in which epitaxial growth is carried out on the silicon (110) substrate using gas, and that the storage temperature after cooling in the epitaxial treatment be 540°C or lower and with a temperature variation of ±30°C or less.

[0034] By using such storage temperatures, the occurrence of minute surface protrusion defects during storage can be further suppressed.

[0035] Furthermore, the heat treatment is an epitaxial treatment in which epitaxial growth is performed on the silicon (110) substrate using gas, and during cooling in the epitaxial treatment, it is preferable to keep the temperature difference within the surface of the silicon (110) substrate within ±10°C when the average temperature within the surface of the silicon (110) substrate is in the range of 630°C to 750°C.

[0036] Such an in-plane temperature difference can further suppress the generation of minute protrusion-like defects within the plane.

[0037] Furthermore, it is preferable that the gas (excluding the inert gas) does not contain any atoms other than hydrogen and chlorine, other than those used for the epitaxial treatment.

[0038] By using such a gas species, it is possible to grow the material with as few extra atoms as possible, thereby further suppressing the generation of minute surface protrusion defects caused by these extra atoms.

[0039] Furthermore, it is preferable to set the flow rate of the aforementioned gas (excluding inert gas) to 1000 sccm or less.

[0040] With such a gas flow rate, the number of reactive species can be reduced due to the relatively low flow rate, and the generation of minute surface protrusion defects caused by an excessive number of reactive species can be further suppressed.

[0041] With the silicon (110) substrate of the present invention, the off-angle is greater than 2° and less than 36°, resulting in a low surface energy and a stable surface, which suppresses the occurrence of surface protrusion defects.

[0042] Furthermore, by using the silicon (110) substrate processing method of the present invention, by preparing a silicon (110) substrate with an off-angle greater than 2° and less than 36°, the surface energy can be reduced, resulting in a stable surface and suppressing the occurrence of surface protrusion defects. Moreover, by using an annealed substrate that has been heat-treated at 1000°C or higher, it is possible to further prevent the detection of protrusion defects.

[0043] Further, in the present invention, after heat-treating a silicon (110) substrate at 1000°C or higher, by cooling a temperature range of 540 to 640°C at a rate of 1000°C / min or higher, the phase transition temperature can be rapidly passed through, and the generation of protrusion defects on the surface can be further suppressed.

[0044] Further, if the relationship between the surface energy, the process temperature, and the off-angle is determined in advance, it is also possible to determine an off-angle suitable for the process temperature for suppressing the generation of protrusion defects on the surface, or to determine the process temperature conditions based on the off-angle.

[0045] It is a diagram showing the heat treatment temperature for treating silicon (110), the defects generated on the surface of silicon (11), and the change in the surface structure due to step bunching. It is a graph showing the relationship between the off-angle and the surface energy (the product of the step terrace width obtained from the off-angle and the heat treatment temperature). It is an AFM image of the surface after heat-treating wafers with different off-angles at 1080°C. It is a schematic diagram of a silicon (110) substrate in an embodiment of the present invention.

[0046] Hereinafter, the present invention will be described in detail, but the present invention is not limited thereto.

[0047] As described above, there has been a demand for providing a silicon (110) substrate in which the generation of protrusion defects on the surface is suppressed, and a method for treating a silicon (110) substrate for suppressing the generation of protrusion defects on the surface.

[0048] Therefore, in order to clarify the mechanism by which protrusion defects on the surface occur, the present inventors have conducted various studies focusing particularly on the off-angle of the silicon (110) substrate and the heat treatment temperature of the silicon (110) substrate.

[0049] First, changing the Euler angle θ, or off-angle, of the silicon (110) surface by 30° results in silicon (111). Furthermore, by finely varying this off-angle, for example, numerous high-index surfaces exist between silicon (110) and (111). Among these high-index surfaces, silicon (551), which is a relatively low-index surface, has better surface roughness than silicon (110). In other words, it is clear that surface roughness changes with the off-angle, and considering that surface roughness is influenced by the presence and amount of surface protrusion defects, we hypothesized that it may be possible to suppress surface protrusion defects by changing the off-angle.

[0050] Furthermore, our investigation revealed that hydrogen baking of a silicon (110) substrate before epitaxial growth causes minute protrusion-like defects to occur in the adjacent areas of the most stable structure 16×2 (referred to as disorder regions in Non-Patent Literature 2).

[0051] Furthermore, it has been found that defect formation on the silicon (110) surface is related to step bunching. It has also been discovered that the temperature at which step bunching, or the reconstruction of surface atoms, occurs is crucial.

[0052] Further explanation regarding this matter will be provided with reference to the figure. Figure 1 shows the heat treatment temperature for processing silicon (110) and the changes in surface structure due to defects and step bunching that occur on the surface of silicon (110).

[0053] First, the results in the upper panel show the TEM observation results of silicon (110) heat-treated at various heat treatment temperatures. It can be seen that defects increase from 600°C to around 800°C, and then decrease and gradually disappear above 800°C.

[0054] The lower section shows the results of surface step observation using AFM, where the angle (direction of the lines) of the steps changes in the temperature range between 540°C and 800°C. At 540°C, the steps are vertical, at 600°C and 760°C they are diagonal, showing the same trend, and at 800°C they look like a "く" shape. Regarding the surface structure, at 540°C it is a 16×2 structure, at 600°C and 760°C it is a (17,15,1)2×1 structure, and at 800°C it is a 1×1 structure. Therefore, the difference in the angle (direction of the lines) of the steps is thought to be due to the difference in surface structure.

[0055] Furthermore, comparing the upper and lower sections, it can be said that 800°C has the most defects and, structurally, is close to the boundary between a (17,15,1) 2x1 structure and a 1x1 structure.

[0056] Therefore, we hypothesized that performing heat treatment at a temperature close to the boundary where the structure changes would easily lead to step bunching (reconstruction of surface atoms), which in turn could cause defects to form.

[0057] Therefore, we attempted to systematically summarize the relationship between off-angle, heat treatment temperature, and defect formation, and to establish a guideline method that allows for the selection of a substrate with an appropriate off-angle and processing at an appropriate heat treatment temperature, depending on the device process such as film deposition and etching, and the substrate fabrication process.

[0058] According to Non-Patent Document 5, the step terrace width (hereinafter also referred to as step width or terrace width) is considered to play an important role in surface stability.

[0059] On the other hand, external energy is required to induce step motion, such as that seen in step bunching. In other words, the step motion on the surface (i.e., the motion that leads to defect formation in silicon (110)) is related to both the step width and thermal energy.

[0060] Therefore, we considered estimating the surface energy of silicon (110) by the product of the step width and thermal energy. Although thermal energy is normally determined by the product of temperature and time, if we assume that the temperature is constant and the processing is performed for the same amount of time, the parameter can be simplified to temperature only. As a result, the surface energy can be estimated as the product of the step width and thermal energy (temperature) (see Equation 1 below).

[0061]

[0062] Furthermore, according to Non-Patent Document 4, the step width (hereinafter also referred to as the step length) of silicon (110) can be expressed by the following Equation 2 using the off-angle.

[0063]

[0064] Based on the above, plotting the off-angle and surface energy (calculated by substituting the step width obtained from the off-angle in Equation 2 into Equation 1 and calculating the product with the heat treatment temperature) results in the graph shown in Figure 2. The horizontal axis represents the off-angle, and the vertical axis represents the surface energy (product of step terrace width and heat treatment temperature). For clarity, the step terrace width is calculated in nm and the temperature in Kelvin (K).

[0065] The results in Figure 2 show that as the off-angle increases, the surface energy (product of step terrace width and heat treatment temperature) decreases. In other words, as the off-angle increases, the surface energy decreases, making step motion less likely and resulting in a more stable surface. As a result, it is expected that the occurrence of surface protrusion defects will be suppressed.

[0066] In fact, when we look at the changes due to the off-angle with silicon (110) as a reference, when the off-angle is small (for example, 1.0°), the surface energy is the largest in Figure 2 (approximately 100 nm·K), and after heat treatment at, for example, 1080°C, numerous protruding defects are observed on the surface of 110 in Figure 3.

[0067] On the other hand, when the off-angle of silicon (110) in Figure 2 is increased to about 8°, the surface energy decreases (approximately 0.001 nm·K, equivalent to silicon (551)), and when the off-angle is further increased to about 35°, the surface energy decreases even more (approximately 0.00003 nm·K, equivalent to silicon (111)). After heat treatment at 1080°C, the surfaces of 551 and 111 in Figure 3 show very few surface defects.

[0068] For reference, regarding step bunching, in silicon (111), it occurs at around 860°C (Non-Patent Literature 4), while in silicon (110), our research has shown that it occurs from around 600°C (see Figure 1). Therefore, silicon (110) has a higher surface energy and is more prone to undergoing changes.

[0069] Based on the above, in order to suppress defects on the silicon (110) surface, the surface energy should be reduced. To reduce the surface energy to 10 nm·K or less, which is an order of magnitude lower than the highest surface energy of 100 nm·K shown in Figure 2, the off-angle should be greater than 2°. Furthermore, since the minimum surface energy of approximately 0.00003 nm·K was confirmed at an off-angle of 35°, it is safer to set the upper limit of the off-angle to less than 36°.

[0070] Therefore, by selecting a silicon (110) substrate with an off-angle greater than 2° and less than 36°, the occurrence of surface protrusion defects can be suppressed.

[0071] To summarize, the surface energy is expressed as the product of the step terrace width (Equation 2), calculated from the off-angle of silicon (110), and the heat treatment temperature (Equation 1). When the relationship with the off-angle is plotted, the relationship shown in Figure 2 is obtained. In other words, it was found that as the off-angle of silicon (110) increases (especially when it is greater than 2° and less than 36°), the surface energy decreases and stabilizes.

[0072] Therefore, as shown in Figure 3, when the same heat treatment conditions of 1080°C were applied, it was confirmed that the number of defects decreased and the surface stabilized as the off-angle increased to 8° (551 in Figure 3) and 35° (111 in Figure 3).

[0073] In this way, by clarifying the relationship between the off-angle and the surface energy that drives defect formation on the silicon (110) surface, it becomes possible to determine the heat treatment conditions (especially the process temperature) according to the off-angle, or conversely, to select an off-angle suitable for the heat treatment conditions.

[0074] As described above, in order to clarify the mechanism by which surface protrusion defects occur, the inventors have conducted various studies, focusing particularly on the off-angle of the silicon (110) substrate and the heat treatment temperature of the silicon (110) substrate, and have found a silicon (110) substrate in which the occurrence of surface protrusion defects is suppressed, and a method for processing the silicon (110) substrate to suppress the occurrence of surface protrusion defects, thereby completing the present invention.

[0075] In other words, the silicon (110) substrate of the present invention is characterized in that it has an off-angle, and the off-angle is greater than 2° and less than 36°.

[0076] Furthermore, the present invention relates to a method for processing a silicon (110) substrate, characterized by preparing a silicon (110) substrate having an off-angle greater than 2° and less than 36°, and then subjecting the silicon (110) substrate having the off-angle to a heat treatment of 1000°C or higher to produce an annealed substrate.

[0077] Embodiments of the present invention will be described below with reference to the drawings.

[0078] First, the silicon (110) substrate of the present invention has an off-angle, which is greater than 2° and less than 36°.

[0079] With such a silicon (110) substrate, the off-angle is greater than 2° and less than 36°, resulting in a low surface energy and a stable surface, which suppresses the occurrence of surface protrusion defects.

[0080] Here, although not particularly limited, a native oxide film is often formed on the surface of silicon (110) substrates.

[0081] Figure 4 is a schematic diagram of a silicon (110) substrate 1 in one embodiment of the present invention.

[0082] The silicon (110) substrate 1 comprises a base material 2 having an off-angle greater than 2° and less than 36° in silicon (110), and a native oxide film 3 is formed on the surface of this base material 2.

[0083] While not specifically limited, generally, before epitaxial growth, annealing (hydrogen baking) is performed under a high-temperature hydrogen atmosphere to remove the native oxide film 3 present on the silicon substrate surface. The temperature at this time is not specifically limited, but is often in the range of approximately 1000°C or higher. This is because even a thin native oxide film of less than 1 nm can prevent the epitaxial growth of silicon due to the presence of an amorphous oxide layer.

[0084] Therefore, although the silicon (110) substrate 1 is not particularly limited, it is preferable that it is an annealed substrate that has been heat-treated at 1000°C or higher and that no protruding defects are detected. For example, Figure 3 shows an example in which heat treatment has been performed at 1080°C.

[0085] Annealed substrates that have undergone heat treatment at temperatures above 1000°C are preferable because no surface protrusion defects are detected even after heat treatment.

[0086] The upper limit of the heat treatment temperature is not particularly limited, but it is preferably below the melting point of silicon, 1420°C, and more preferably 1300°C or lower. Furthermore, depending on the capacity of the heat treatment apparatus, the temperature can be set to, for example, 1200°C or lower in order to reduce power consumption during heat treatment, although this is not particularly limited.

[0087] Furthermore, although not particularly limited, it is preferable that the annealed substrate is heat-treated at 1000°C or higher, and then cooled at a rate of 1000°C / min or higher in the temperature range of 540 to 640°C.

[0088] If the annealed substrate is cooled at such a rate, the phase transition temperature will be passed quickly during cooling, further suppressing the generation of surface protrusion defects.

[0089] There is no particular upper limit to the cooling rate, but it can be, for example, 2000°C / min or less.

[0090] Next, a method for processing a silicon (110) substrate in one embodiment of the present invention will be described.

[0091] To solve the above problems, the present invention provides a silicon (110) substrate processing method which involves preparing a silicon (110) substrate with an off-angle greater than 2° and less than 36°, and then subjecting the silicon (110) substrate having an off-angle to a heat treatment of 1000°C or higher to produce an annealed substrate.

[0092] With this silicon (110) substrate processing method, by preparing a silicon (110) substrate with an off-angle greater than 2° and less than 36°, the surface energy can be reduced, resulting in a stable surface and suppressing the occurrence of surface protrusion defects. Furthermore, by using an annealed substrate that has been heat-treated at 1000°C or higher, it is possible to further prevent the detection of protrusion defects.

[0093] The upper limit of the heat treatment temperature is not particularly limited, but it is preferably below the melting point of silicon, 1420°C, and more preferably 1300°C or lower. Furthermore, depending on the capacity of the heat treatment apparatus, the temperature can be set to, for example, 1200°C or lower in order to reduce power consumption during heat treatment, although this is not particularly limited.

[0094] Furthermore, the heat treatment is preferably an etching process that removes the native oxide film of the silicon (110) substrate using an etching gas, although this is not particularly limited, and the gas pressure is preferably 5 Torr or higher, although this is not particularly limited. Hydrogen gas or the like can be used as the etching gas.

[0095] With this etching gas pressure, the evaporation of atoms during etching is suppressed due to the relatively high pressure, thus further suppressing the generation of minute surface protrusion defects caused by atomic evaporation.

[0096] There is no particular upper limit to the etching pressure, but it can be, for example, 100 Torr or less. Here, 1 Torr is approximately 133.32 Pa in the International System of Units (SI).

[0097] Furthermore, the heat treatment is an etching process that removes the native oxide film of the silicon (110) substrate using an etching gas, although this is not particularly limited. During cooling in the etching process, although this is not particularly limited, it is preferable to cool at a rate of 1000°C / min or more in the temperature range of 540 to 640°C.

[0098] If the etched substrate is cooled at such a rate, the phase transition temperature can be passed quickly during cooling, further suppressing the occurrence of surface protrusion defects.

[0099] There is no particular upper limit to the cooling rate, but it can be, for example, 2000°C / min or less.

[0100] Furthermore, the heat treatment is preferably an etching process that removes the native oxide film of the silicon (110) substrate using an etching gas, although this is not particularly limited. The storage temperature after cooling in the etching process is preferably 540°C or lower with a temperature variation of ±30°C or less, although this is not particularly limited.

[0101] By using such storage temperatures, the occurrence of minute surface protrusion defects during storage can be further suppressed.

[0102] The lower limit of the storage temperature is not particularly limited, but it can be, for example, 30°C or higher.

[0103] Furthermore, the heat treatment is an etching process that removes the native oxide film of the silicon (110) substrate using an etching gas, although this is not particularly limited. During cooling in the etching process, although this is not particularly limited, it is preferable to keep the temperature difference within the plane of the silicon (110) substrate within ±10°C when the average temperature within the plane of the silicon (110) substrate is in the range of 630°C to 750°C.

[0104] For example, when the average temperature within a plane is the boundary temperature of 630°C or 750°C, a large temperature difference within the plane may result in a mixture of temperature ranges where defects are likely to form and temperature ranges where defects are not. However, by keeping the temperature difference within the plane within ±10°C, the possibility of such a mixture of temperature ranges can be reduced, and as a result, the occurrence of minute protrusion-like defects within the plane can be further suppressed.

[0105] Furthermore, the heat treatment is preferably an epitaxial treatment in which epitaxial growth is carried out on a silicon (110) substrate using a gas, although this is not particularly limited, and the gas pressure is preferably 5 Torr or less, although this is not particularly limited.

[0106] With such a gas pressure, the adhesion of atoms to the substrate surface can be suppressed to some extent due to the relatively low pressure, preventing growth from becoming too rapid. This further suppresses the generation of minute surface protrusion defects caused by excessive growth.

[0107] The lower limit of the pressure for epigenetic growth is not particularly limited, but it can be, for example, 1 Torr or more.

[0108] Furthermore, the heat treatment is an epitaxial treatment in which epitaxial growth is carried out on a silicon (110) substrate using gas, although this is not particularly limited. During cooling in the epitaxial treatment, although this is not particularly limited, it is preferable to cool at a rate of 1000°C / min or more in the temperature range of 540 to 640°C.

[0109] If the substrate after epitaxial treatment is cooled at such a rate, the phase transition temperature can be passed quickly during cooling, further suppressing the generation of protruding surface defects.

[0110] There is no particular upper limit to the cooling rate, but it can be set to 2000°C / min or less, for example, similar to the etching conditions.

[0111] Furthermore, the heat treatment is preferably an epitaxial treatment in which epitaxial growth is carried out on a silicon (110) substrate using gas, although this is not particularly limited, and the storage temperature after cooling in the epitaxial treatment is preferably 540°C or lower and with a temperature variation of ±30°C or less, although this is not particularly limited.

[0112] By using such storage temperatures, the occurrence of minute surface protrusion defects during storage can be further suppressed.

[0113] The lower limit of the storage temperature is not particularly limited, but it can be set to 30°C or higher, for example, similar to the conditions after etching.

[0114] Furthermore, the heat treatment is an epitaxial treatment in which epitaxial growth is carried out on a silicon (110) substrate using gas, although this is not particularly limited. During cooling in the epitaxial treatment, although this is not particularly limited, it is preferable to keep the temperature difference within the plane to within ±10°C when the average temperature within the plane of the silicon (110) substrate is in the range of 630°C to 750°C.

[0115] For example, when the average temperature within a plane is the boundary temperature of 630°C or 750°C, a large temperature difference within the plane may result in a mixture of temperature ranges where defects are likely to form and temperature ranges where defects are not. However, by keeping the temperature difference within the plane within ±10°C, the possibility of such a mixture of temperature ranges can be reduced, and as a result, the occurrence of minute protrusion-like defects within the plane can be further suppressed.

[0116] Furthermore, while the gas is not particularly limited, it is preferable that it does not contain any atoms other than hydrogen and chlorine, except for those used for epitaxial processing.

[0117] By using such a gas species, it is possible to grow the material with as few extra atoms as possible, thereby further suppressing the generation of minute surface protrusion defects caused by these extra atoms.

[0118] For example, as a gas for epitaxial processing (excluding inert gases), SiH ４ and GeH ４ While these are examples, it is preferable that the material does not contain any atoms other than hydrogen and chlorine, other than the atoms used for epitaxial treatment (Si and Ge).

[0119] Furthermore, while there are no specific limitations on the flow rate of the gas (excluding inert gas), it is preferable to keep it at 1000 sccm or less.

[0120] With such a gas flow rate, the number of reactive species can be reduced due to the relatively low flow rate, and the generation of minute surface protrusion defects caused by an excessive number of reactive species can be further suppressed.

[0121] The lower limit of the gas flow rate is not particularly limited, but it can be, for example, 100 sccm or more.

[0122] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0123] From Equation 2, the step terrace width for each off-angle was calculated and multiplied by the heat treatment temperature. The off-angle was set to match the high-index surface. The temperature was set between 873 K (600°C) and 1273 K (1000°C). These values ​​were calculated according to Equation 1, and the off-angle and surface energy (product of step terrace width and heat treatment temperature) were plotted and graphed (Figure 2).

[0124] From this plot, it was found that silicon (110), which has a similar surface energy to silicon (551), has a lower and more stable surface energy at an off-angle of 8° compared to silicon (110) with a smaller off-angle (e.g., 1.0°), and it was predicted that the generation of surface protrusion defects is suppressed at an off-angle of 8°.

[0125] Therefore, to confirm this, the following experiment was conducted.

[0126] First, a 300 mm diameter (110) boron-doped ingot with a resistance of 10 Ω·cm was sliced ​​so that the off-angle was exactly 8° in the direction of the (001) plane (i.e., (551) in Figure 2), and then processed into a single-crystal silicon substrate for preparation.

[0127] Next, the substrate was annealed in a hydrogen atmosphere at a temperature of 1080°C for 600 seconds. The pressure during this process was 5 Torr, and cooling was achieved by limiting the output of the heating lamp.

[0128] AFM measurements were then performed, and the result was obtained as shown in Figure 3, 551. The 551 with an off-angle of 8° had fewer defects compared to the 110 with an off-angle of 1.0°, confirming from the experiment that the 551 with an off-angle of 8° is advantageous. This result was as predicted from Figure 2 above.

[0129] The present invention encompasses the following embodiments: [1] A silicon (110) substrate, characterized in that the silicon (110) substrate has an off-angle, and the off-angle is greater than 2° and less than 36°. [2] The silicon (110) substrate according to [1], characterized in that the silicon (110) substrate is an annealed substrate that has been heat-treated to 1000°C or higher, and no protruding defects are detected. [3] The silicon (110) substrate according to [2], characterized in that the annealed substrate has been cooled in the temperature range of 540 to 640°C at a rate of 1000°C / min or higher after the heat treatment to 1000°C or higher. [4] A method for processing a silicon (110) substrate, characterized in that a silicon (110) substrate having an off-angle greater than 2° and less than 36° is prepared, and an annealed substrate is produced by heat-treating the silicon (110) substrate having the off-angle to 1000°C or higher. [5]: The method for processing a silicon (110) substrate according to [4] above, characterized in that the heat treatment is an etching treatment to remove the native oxide film of the silicon (110) substrate using an etching gas, and the pressure of the gas is 5 Torr or more. [6]: The method for processing a silicon (110) substrate according to [4] or [5] above, characterized in that the heat treatment is an etching treatment to remove the native oxide film of the silicon (110) substrate using an etching gas, and during cooling in the etching treatment, the temperature range of 540 to 640°C is cooled at a rate of 1000°C / min or more. [7]: The method for processing a silicon (110) substrate according to any one of [4] to [6] above, characterized in that the heat treatment is an etching treatment to remove the native oxide film of the silicon (110) substrate using an etching gas, and the storage temperature after cooling in the etching treatment is 540°C or less and the temperature variation is within ±30°C.[8]: The method for processing a silicon (110) substrate according to any one of [4] to [7] above, wherein the heat treatment is an etching treatment in which an etching gas is used to remove the native oxide film of the silicon (110) substrate, and during cooling in the etching treatment, the temperature difference in the plane of the silicon (110) substrate is kept within ±10°C when the average temperature in the plane of the silicon (110) substrate is in the range of 630°C to 750°C. [9]: The method for processing a silicon (110) substrate according to [4] above, wherein the heat treatment is an epitaxial treatment in which epitaxial growth is performed on the silicon (110) substrate using a gas, and the pressure of the gas is 5 Torr or less.

[10] : The method for processing a silicon (110) substrate according to [4] or [9] above, characterized in that the heat treatment is an epitaxial treatment in which epitaxial growth is performed on the silicon (110) substrate using a gas, and during cooling in the epitaxial treatment, the temperature range of 540 to 640°C is cooled at a rate of 1000°C / min or more.

[11] : The method for processing a silicon (110) substrate according to any one of [4], [9] or

[10] above, characterized in that the heat treatment is an epitaxial treatment in which epitaxial growth is performed on the silicon (110) substrate using a gas, and the storage temperature after cooling in the epitaxial treatment is 540°C or less and the temperature variation is within ±30°C.

[12] : The method for processing a silicon (110) substrate according to any one of [4] or [9] to

[11] above, characterized in that the heat treatment is an epitaxial treatment in which epitaxial growth is performed on the silicon (110) substrate using a gas, and during cooling in the epitaxial treatment, the temperature difference in the plane of the silicon (110) substrate is kept within ±10°C when the average temperature in the plane of the silicon (110) substrate is in the range of 630°C to 750°C.

[13] : The method for processing a silicon (110) substrate according to any one of [9] to

[12] above, characterized in that the gas (excluding inert gas) does not contain anything other than hydrogen and chlorine other than atoms for the epitaxial treatment.

[14] : The method for processing a silicon (110) substrate according to any one of [9] to

[13] above, characterized in that the flow rate of the gas (excluding inert gas) is 1000 sccm or less.

[0130] It should be noted that the present invention is not limited to the embodiments described above. The embodiments described above are illustrative, and any configuration that has substantially the same technical idea as described in the claims of the present invention and achieves similar effects is included within the technical scope of the present invention.

Claims

1. A silicon (110) substrate, characterized in that the silicon (110) substrate has an off-angle, and the off-angle is greater than 2° and less than 36°.

2. The silicon (110) substrate according to claim 1, characterized in that the silicon (110) substrate is an annealed substrate that has been heat-treated at 1000°C or higher, and no protruding defects are detected.

3. The silicon (110) substrate according to claim 2, characterized in that the annealed substrate is cooled at a rate of 1000°C / min or more in the temperature range of 540 to 640°C after the heat treatment of 1000°C or more.

4. A method for processing a silicon (110) substrate, characterized by preparing a silicon (110) substrate having an off-angle greater than 2° and less than 36°, and performing a heat treatment of 1000°C or higher on the silicon (110) substrate having the off-angle to produce an annealed substrate.

5. The method for processing a silicon (110) substrate according to claim 4, characterized in that the heat treatment is an etching treatment that removes the native oxide film of the silicon (110) substrate using an etching gas, and the pressure of the gas is 5 Torr or more.

6. The method for processing a silicon (110) substrate according to claim 4, characterized in that the heat treatment is an etching treatment that removes the native oxide film of the silicon (110) substrate using an etching gas, and during cooling in the etching treatment, the temperature range of 540 to 640°C is cooled at a rate of 1000°C / min or more.

7. The method for processing a silicon (110) substrate according to claim 4, characterized in that the heat treatment is an etching treatment that removes the native oxide film of the silicon (110) substrate using an etching gas, and the storage temperature after cooling in the etching treatment is 540°C or less and the temperature variation is within ±30°C.

8. The method for processing a silicon (110) substrate according to claim 4, wherein the heat treatment is an etching treatment that removes the native oxide film of the silicon (110) substrate using an etching gas, and during cooling in the etching treatment, the temperature difference within the surface of the silicon (110) substrate is kept within ±10°C when the average temperature within the surface of the silicon (110) substrate is in the range of 630°C to 750°C.

9. The method for processing a silicon (110) substrate according to claim 4, characterized in that the heat treatment is an epitaxial treatment in which epitaxial growth is carried out on the silicon (110) substrate using a gas, and the pressure of the gas is 5 Torr or less.

10. The method for processing a silicon (110) substrate according to claim 4, characterized in that the heat treatment is an epitaxial treatment in which epitaxial growth is performed on the silicon (110) substrate using a gas, and during cooling in the epitaxial treatment, the temperature range of 540 to 640°C is cooled at a rate of 1000°C / min or more.

11. The method for processing a silicon (110) substrate according to claim 4, characterized in that the heat treatment is an epitaxial treatment in which epitaxial growth is performed on the silicon (110) substrate using gas, and the storage temperature after cooling in the epitaxial treatment is 540°C or less and the temperature variation is within ±30°C.

12. The method for processing a silicon (110) substrate according to claim 4, wherein the heat treatment is an epitaxial treatment in which epitaxial growth is performed on the silicon (110) substrate using a gas, and during cooling in the epitaxial treatment, the temperature difference within the surface of the silicon (110) substrate is kept within ±10°C when the average temperature within the surface of the silicon (110) substrate is in the range of 630°C to 750°C.

13. The method for processing a silicon (110) substrate according to any one of claims 9 to 12, characterized in that the gas (excluding inert gas) does not contain anything other than hydrogen and chlorine, other than the atoms for epitaxial processing.

14. A method for processing a silicon (110) substrate according to any one of claims 9 to 12, characterized in that the flow rate of the gas (excluding inert gas) is 1000 sccm or less.

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