Silicon single crystal substrate and method for manufacturing silicon single crystal substrate

Abstract

To provide a silicon single crystal substrate capable of suppressing the haze of a silicon (110) substrate and having a stable surface structure, and a method for manufacturing the silicon single crystal substrate.SOLUTION: A silicon single crystal substrate has a plane direction of (110), and the surface of the silicon single crystal substrate has a surface stable structure 1×1 in the room temperature environment. A method for manufacturing the silicon single crystal substrate comprises preparing the silicon single crystal substrate having a plane direction of (110) and forming the surface stable structure 1×1 in the room temperature environment by rapidly annealing the silicon single crystal substrate.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a silicon single crystal substrate and a method for manufacturing a silicon single crystal substrate. [Background technology]

[0002] Instead of the Fin structure currently used in logic ICs, GAA (Gate All Around) and CFET (Complementary Field Effect Transistor) stacking NMOS and CMOS have been proposed for the next generation and beyond, and are being actively researched and developed. In this case, the use of silicon (hereinafter also referred to as Si) substrates with a (110) surface orientation is considered to be a method for improving hole mobility (Non-Patent Document 1).

[0003] However, problems with silicon (110) substrates have been pointed out, such as high surface roughness and haze (Non-Patent Document 1). Here, haze is also referred to as the degree of cloudiness of the surface, and is a measure of surface roughness expressed by the degree of light scattering, with larger haze indicating a rougher surface. Also, it was only relatively recently that the most stable structure of the silicon (110) outermost surface was identified (Non-Patent Documents 2, 3).

[0004] According to the description in Non-Patent Documents 2 and 3, the 16×2 domain, which is the most stable surface stable structure, undergoes a phase transition depending on the temperature, and the structure changes in the range of 900K (627°C) to 1043K (770°C) as shown in FIG. 2. (Hereinafter referred to as the range of 600 to 800°C.) This temperature range, for example, hydrogen baking for growing a silicon epitaxial layer (hereinafter simply referred to as epi or epitaxial) and the subsequent silicon epi exceed 1000°C, so the surface stable structure becomes 1×1 at a high temperature at first, but during the subsequent cooling, a phase change occurs while passing through the range of 600 to 800°C, and the surface structure changes depending on the time of passing. For example, SiGe laminated in GAA or CFET often uses exactly this temperature range, making it even more difficult to understand the surface structure.

[0005] This unique surface structure of the silicon (110) surface also affects the surface structure after etching. The step edges of the 16 x 2 surface structure are not single-atom structures like silicon (100), but have a step of two atoms. As a result, when the energy of the reaction system is low (equilibrium reaction), the reaction proceeds with the atoms on the outermost surface, and the surface shape after etching has a linear structure surrounded by silicon (111) that is first closest to the surface. On the other hand, when the energy of the reaction system is high, the outermost surface and even the atoms below it are involved in the reaction, and a square shape appears surrounded by silicon (111) that is second closest to the surface.

[0006] For silicon with such a surface state (110), Patent Document 1 discloses a method for reducing surface roughness by tilting the orientation during epitaxial growth. Patent Document 2 discloses the regulation of the cooling rate and surface protection. Furthermore, Patent Document 3 discloses a method for similarly reducing surface roughness by regulating the surface orientation during crystal growth rather than epitaxial growth. Patent Document 4 discloses polishing the epitaxial surface. Patent Document 5 discloses a combination of Patent Documents 1 and 3. [Prior art documents] [Non-patent literature]

[0007] [Non-Patent Document 1] Japan Society of Applied Physics, Industry-Academia Collaboration Committee on Semiconductor Crystal Growth, Processing and Evaluation, 1st Workshop "Crystal Technology Supporting the Revival of Semiconductors" [Non-Patent Document 2] Yamada et al., "Fabrication of Si(110)-16×2 single domain surface," Surface Science, 29(7), 401 (2008) [Non-Patent Document 3] Miyaji et al., "Observation of the Si(110) reconstructed surface by ultra-high vacuum non-contact atomic force microscope," Journal of the Japan Institute of Metals, 72(4), 290(2008) [Patent documents]

[0008] [Patent Document 1] JP 2008-091887 A [Patent Document 2] JP 2006-100596 A [Patent Document 3] JP 2008-088045 A [Patent Document 4] JP 2014-239184 A [Patent Document 5] JP 2008-091891 A Summary of the Invention [Problem to be solved by the invention]

[0009] As described above, the surface of a silicon (110) substrate has a very complicated shape, and various methods have been disclosed for reducing the surface roughness. However, unlike a silicon (100) substrate, the most stable surface structure of a silicon (110) substrate is a special structure of 16x2 (a structure having a step of two atoms). In addition, the structural transition temperature is 600-800°C, and there is a problem that the surface structure changes and haze is unavoidable in processes that pass through this temperature range, particularly during epitaxial growth.

[0010] The present invention has been made in consideration of the above-mentioned problems in the conventional technology, and has an object to provide a silicon single crystal substrate that suppresses haze on a silicon (110) substrate and has a stable surface structure, and a method for manufacturing the silicon single crystal substrate. [Means for solving the problem]

[0011] In order to solve the above problems, the silicon single crystal substrate of the present invention has a plane orientation of (110), and the surface of the silicon single crystal substrate has a stable 1×1 surface structure in a room temperature environment.

[0012] In the case of a silicon (110) substrate with a surface stable structure of 1 x 1 in a room temperature environment, firstly, because the surface stable structure is 1 x 1, haze is suppressed, unlike a structure with a step of two atoms such as a surface stable structure of 16 x 2. Secondly, because it is a room temperature environment, it is far from the structural transition temperature (600 to 800°C) of the silicon (110) substrate, so the structure is less likely to change and has a stable surface structure.

[0013] In addition, the method for manufacturing a silicon single crystal substrate of the present invention is a method for forming a surface stable structure 1×1 in a room temperature environment by preparing a silicon single crystal substrate having a (110) surface orientation and rapidly annealing the silicon single crystal substrate.

[0014] In the case of such a method of forming a surface stable structure 1×1 in a room temperature environment by rapid annealing, first, rapid annealing is a method of rapidly annealing only the outermost surface of the substrate, and since the temperature of only the outermost surface of the substrate is rapidly increased and the temperature of the substrate other than the outermost surface is not increased, the surface stable structure 1×1 can be formed by making only the outermost surface of the substrate reach the desired temperature in an extremely short time. Since the surface stable structure is 1×1, unlike a structure having a step of two atoms such as the surface stable structure 16×2, haze can be suppressed. Next, since the rapid annealing is performed in a room temperature environment, the substrate other than the outermost surface is maintained at room temperature, and the outermost surface of the substrate can be returned to room temperature in an extremely short time after the rapid annealing is completed. Therefore, during both heating and cooling after the rapid annealing, the temperature of the outermost surface of the substrate can instantly pass through the structural transition temperature (600 to 800° C.), so that the structure is unlikely to change and the substrate can have a stable surface structure. Effect of the Invention

[0015] The silicon single crystal substrate of the present invention is a silicon (110) substrate with a surface stable structure of 1×1 in a room temperature environment, and unlike a structure with a step of two atoms such as a surface stable structure of 16×2, haze is suppressed. Secondly, since it is a room temperature environment, it is far from the structural transition temperature (600 to 800°C) of the silicon (110) substrate, and the structure is less likely to change, resulting in a stable surface structure.

[0016] Furthermore, the method for producing a silicon single crystal substrate of the present invention is a method for forming a surface stable structure 1×1 in a room temperature environment by rapid annealing, and unlike a structure having a step of two atoms such as a surface stable structure 16×2, haze can be suppressed. Furthermore, during both heating and cooling after the end of rapid annealing, the temperature of the outermost surface of the substrate can instantaneously pass through the structural transition temperature (600 to 800° C.), so that the structure is unlikely to change and a stable surface structure can be obtained. [Brief description of the drawings]

[0017] [Figure 1] 1 is a schematic diagram of a silicon single crystal substrate in a first embodiment of the present invention. [Diagram 2] FIG. 2 is a schematic diagram showing the relationship between the surface temperature and the surface stable structure of a silicon (110) substrate. [Diagram 3] 1 is a flow diagram of a method for producing a silicon single crystal substrate in a first embodiment of the present invention. [Figure 4] FIG. 1 is a schematic diagram of a conventional silicon single crystal substrate. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] The present invention will be described in detail below, but the present invention is not limited thereto.

[0019] As described above, there has been a need to provide a silicon single crystal substrate that suppresses haze on a silicon (110) substrate and has a stable surface structure, and a method for manufacturing the silicon single crystal substrate.

[0020] As a result of extensive research into the above-mentioned problems, the inventors discovered that the stable surface structure does not undergo phase change by instantly passing through the temperature range of 600 to 800°C, which is the structural transition temperature of a silicon (110) substrate, and thus completed the present invention.

[0021] That is, the silicon single crystal substrate of the present invention has a plane orientation of (110), and the surface of the silicon single crystal substrate has a stable 1×1 surface structure in a room temperature environment.

[0022] In addition, the method for manufacturing a silicon single crystal substrate of the present invention is a method for forming a surface stable structure 1×1 in a room temperature environment by preparing a silicon single crystal substrate having a (110) surface orientation and rapidly annealing the silicon single crystal substrate.

[0023] Specifically, as a means of obtaining a stable surface with little haze, a surface stable structure 1×1 is formed at high temperature, and rapid annealing (flash lamp annealing) is performed to instantly pass the structural transition temperature (600 to 800°C).

[0024] Here, annealing is usually performed to activate dopants introduced by ion implantation and to recover defects, but conventional annealing using a general halogen lamp takes several seconds to heat up, and the steep profile formed by ion implantation is likely to collapse due to dopant diffusion during this period. Diffusion can be suppressed by lowering the annealing heating temperature, but this has the disadvantage of insufficient activation and recovery of defects, which are the original objectives.

[0025] On the other hand, if a flash lamp annealing method using a xenon flash lamp is used for rapid annealing, this dilemma can be resolved by applying heat only to the substrate surface in a very short time (on the order of milliseconds). This method is used in the present invention.

[0026] By using such flash lamp annealing, it takes only a few milliseconds to heat the surface temperature of the substrate from room temperature (e.g., 25°C) to about 1,200°C, and it takes only a short time to return from about 1,200°C to room temperature after heating is completed. The temperature of the outermost surface of the substrate can instantly pass through the structural transition temperature (600-800°C), so there is no time for the structure to change and an extremely stable surface structure can be maintained. In this case, the surface stable structure 1×1 is formed at about 1,200°C, and the surface stable structure 1×1 can be maintained even when cooled to room temperature. Furthermore, the surface stable structure 1×1 can suppress haze, unlike a structure with a step of two atoms such as the surface stable structure 16×2.

[0027] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0028] 1 is a schematic diagram of a silicon single crystal substrate in a first embodiment of the present invention. The silicon single crystal substrate 1 has a surface orientation of (110) and has two surface stable structures 1×1 on its surface in a room temperature environment. More specifically, the substrate can be fabricated by heating only the substrate surface to approximately 1,200° C. by rapid annealing (flash lamp annealing) for an extremely short time of several milliseconds to form the surface stable structures 1×1, and then returning only the substrate surface to room temperature in an extremely short time.

[0029] On the other hand, Figure 4 is a schematic diagram of a conventional silicon single crystal substrate. Using a conventional annealing method, the entire substrate is heated to 1,200°C in an epitaxial furnace over a long period of time, over several seconds, and then the entire substrate is returned to room temperature over a similarly long period of time. In this case, only the surface stable structure 1×1 similar to that in Figure 1 was formed in the 1,200°C environment in the epitaxial furnace, but since it takes a long time to return to the room temperature environment, the surface structure undergoes a phase change when passing through the structural transition temperature (600-800°C), and not only the surface stable structure 1×1 in 2, but also the surface stable structure 16×2 in 3 and the surface stable structure (17,15,1)2×1 in 4 are formed. The mixture of various structures on the surface in this way results in a large haze.

[0030] FIG. 2 is a schematic diagram showing the relationship between the surface temperature of a silicon (110) substrate and the stable surface structure. This is a summary of what has become clear during further investigations, in addition to the information in Non-Patent Documents 2 and 3. Silicon (110) is prone to form a stable surface structure 16×2 at low temperatures below 900 K (627°C), a stable surface structure 1×1 at high temperatures above 1043 K (770°C), and a stable surface structure (17,15,1)2×1 in the range of 900 K (627°C) to 1043 K (770°C). For example, a stable surface structure (17,15,1)2×1 is formed at 1003 K (730°C).

[0031] Among these, the surface-stabilized structure 16×2 has a step of two atoms, the surface-stabilized structure (17,15,1)2×1 is said to have a stepped structure, and the surface-stabilized structure 1×1, which has fewer steps, is more preferable. The surface-stabilized structure 1×1 can most effectively suppress haze.

[0032] According to Figure 2, the surface stable structure 1×1 is formed at a temperature of 1043 K (770°C) or higher, so although the explanation above using Figures 1 and 4 gave an example of about 1,200°C, this is not limited to this and the temperature can be selected arbitrarily in the range of 770°C or higher.

[0033] FIG. 3 is a flow diagram of a method for producing a silicon single crystal substrate in the first embodiment of the present invention.

[0034] First, in step S1, a silicon single crystal substrate having a (110) surface orientation is prepared.

[0035] Next, in step S2, the silicon single crystal substrate is subjected to rapid annealing to form a surface stable structure 1×1 in a room temperature environment. This is a method in which only the outermost surface of silicon (110) is instantly heated by rapid annealing to form the surface stable structure 1×1 at high temperature, and then the structural transition is suppressed by rapid cooling.

[0036] Here, as a method for this rapid annealing, flash lamp annealing using a flash lamp filled with a rare gas such as xenon can be used. This flash lamp has a radiation rate of, for example, several tens of J / cm. 2 The method may involve irradiating the above-mentioned high energy in the form of pulsed light of 0.1 to 100 milliseconds.

[0037] The room temperature is expected to be between 0 and 40°C depending on the season, and can be kept at, for example, 25°C using air conditioning equipment.

[0038] Furthermore, based on non-patent documents 2 and 3 and knowledge gained during further investigation, the surface temperature of silicon (110) when forming the surface stable structure 1x1 should be 850°C or higher, but can be, for example, 1,200°C or lower, specifically 1,200°C.

[0039] As described above, within these conditions, the heating and cooling times are only a few milliseconds, and the structural transition temperature (600 to 800°C) can be instantly passed. As a result, a silicon single crystal substrate with a stable 1x1 surface structure can be produced in a room temperature environment. EXAMPLES

[0040] The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited thereto.

[0041] [Example 1] Silicon single crystal substrates with a diameter of 300 mm, a surface orientation of (110), doped with boron, and a resistance of 10 Ω·cm were prepared, and 25 of them were subjected to flash lamp annealing in a room temperature environment. Flash lamp energy: 30J / cm 2 Flash lamp pulse width: 5 ms (1 pulse) · Surface temperature of single crystal silicon substrate: Average 1,200℃ ·Room temperature: 25℃ Time to pass structural transition temperature (600-800℃): Average 5 milliseconds

[0042] After that, the haze was measured using an optical defect inspection device (KLA-Tencor's SurfScan-SP3, hereafter referred to as KLA / SP-3), and the haze values ​​from the first to the 25th sheets were stable at low values ​​between 0.7 and 0.8 ppm. When examined with an atomic force microscope (AFM), the surface was found to have a stable structure of 1 × 1.

[0043] [Comparative Example 1] Silicon single crystal substrates with a diameter of 300 mm, a surface orientation of (110), boron doping, and a resistivity of 10 Ω·cm were prepared, and 25 substrates were successively annealed in an epitaxial furnace at 1,140°C using hydrogen. Where: - Surface temperature (and overall temperature) of single crystal silicon substrate: 1,140℃ ·Room temperature: 25℃ Time to pass structural transition temperature (600-800℃): 10 seconds on average

[0044] Thereafter, the haze was measured using KLA / SP-3, and the haze values ​​from the first sheet to the 25th sheet were 1 to 2.5 ppm, which was larger than that in Example 1 and tended to vary more. When examined with an AFM, the surface stable structure was 16×2.

[0045] As described above, it was found that Example 1 had a lower and more stable haze value than Comparative Example 1.

[0046] The present invention is not limited to the above-described embodiment. The above-described embodiment is merely an example, and any configuration that is substantially the same as the technical idea described in the claims of the present invention and that provides similar effects is included in the technical scope of the present invention. [Explanation of symbols]

[0047] 1...Silicon single crystal substrate, 2...Surface stabilized structure 1×1, 3...Surface stabilized structure 16×2, 4…Surface stable structure (17,15,1)2×1. S1, S2...steps.

Claims

1. A silicon single crystal substrate, characterized in that the surface orientation is (110), and the surface of the silicon single crystal substrate has a 1x1 surface stable structure in a room temperature environment.

2. A silicon single crystal substrate having a (110) surface orientation is prepared. A method for producing a silicon single crystal substrate, comprising the steps of: rapidly annealing the silicon single crystal substrate to form a 1x1 surface stable structure in a room temperature environment.

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