WO2020111790A1 - Method for manufacturing diamond substrate - Google Patents

Abstract

The present invention relates to a method for manufacturing a diamond substrate, and the method for manufacturing a diamond substrate, of the present invention, is a method using a photoresist pattern and a heat treatment and the like for an air gap formation film material so as to form, on a substrate such as sapphire (Al2O3), an air gap structure having a crystalline correlation with a lower substrate, and then grow a diamond. The method simplifies a process during the heterogeneous growth of large-area/large-diameter single crystal diamond and lowers costs, and mitigates the stress caused by a difference in lattice constants and thermal expansion coefficients between a heterogeneous substrate and diamond and reduces defects or cracks even during drops in temperature, thereby manufacturing a single crystal diamond substrate with high quality and facilitating self-separation of the diamond substrate from the heterogeneous substrate.

Description

Diamond substrate manufacturing method

The present invention relates to a method for manufacturing a single crystal diamond substrate, and more particularly, to a method for manufacturing a single crystal diamond substrate in which high-quality single crystal diamond substrates are heterogeneously grown and separated by themselves.

The single crystal diamond semiconductor is a very wide band gap (5.5 eV) material, and is a semiconductor material having very good physical properties such as high thermal conductivity, electron/hole mobility, and dielectric breakdown strength (10MV/cm). It is expected to be used in a variety of high-frequency, high-power electronic devices with extreme performance. The growth of single crystal diamonds for semiconductor devices is currently the only high temperature/high pressure method. However, by the high temperature/high pressure method, only a very small die (≤ 10×10 mm ² ) can be obtained, and there is no cost competitiveness to apply as a semiconductor device due to the high cost required.

In order to overcome this, heterogeneous growth technology using chemical vapor deposition has been studied in earnest since the 1990s, and the diamond single crystal heterogeneous growth technology presented so far is mainly incomplete with a large diameter on a single crystal Si substrate or a single crystal oxide substrate such as Al ₂ O ₃ or MgO. It has reached the point where single crystal diamond can be grown. That is, the conventional single crystal diamond heterogeneous growth method has an advantage of obtaining a large-diameter thin film or a substrate, but a large stress is introduced due to a difference in lattice constant and thermal expansion coefficient with a dissimilar substrate, resulting in many defects and cracks when the temperature decreases after growth. ), there is a problem that the yield falls.

Therefore, the present invention has been devised to solve the above-mentioned problems, and an object of the present invention is to form an air gap structure using a photoresist pattern on a substrate such as sapphire (Al ₂ O ₃ ). By applying a simple process and a low-cost growth method for heterogeneous growth of large-area/large-diameter single crystal diamonds, it relieves stress caused by differences in lattice constants and thermal expansion coefficients with dissimilar substrates, and reduces defects or cracks even when the temperature decreases, resulting in high quality. It is to provide a single crystal diamond substrate manufacturing method, and to provide a single crystal diamond manufacturing method in which self-separation of a diamond substrate from a dissimilar substrate can be easily performed.

First, to summarize the features of the present invention, a diamond substrate manufacturing method according to an aspect of the present invention for achieving the above object, forming a repeating photoresist pattern on the lower substrate; Depositing an air gap forming film; Removing the photoresist by heat treatment and forming an air gap between the lower substrate and the air gap forming film; Forming a buffer layer; Forming a diamond thick film; And cooling the diamond thick film to self-separate from the lower substrate.

The shape of the photoresist pattern is embossed or engraved and includes a stripe, circle, or polygonal shape.

In the step of forming the air gap, the air gap forming film is crystallized in the same orientation as the lower substrate by the heat treatment, and the photoresist is evaporated to form the air gap at the position where the photoresist was. .

By forming the air gap, the stress due to the difference in the lattice constant and the coefficient of thermal expansion between the lower substrate and the heterogeneous diamond thick film is relieved, and when the cooling occurs, defects or cracks in the diamond thick film are reduced to obtain a diamond substrate. .

The lower substrate may be an Al ₂ O ₃ substrate, an MgO substrate, an Iridium substrate, a Quartz substrate, a Platinum substrate, a SiC substrate, an YSZ substrate, a SrTiO3 substrate, a silicon substrate, an SOI substrate, or a group III-V compound semiconductor substrate.

The air gap forming film may be formed of Al ₂ O ₃ , MgO, Iridium, Quartz, Platinum, SiC, YSZ, SrTiO3, Si or a group 3-5 compound material.

In the step of forming the air gap, the heat treatment temperature may be in the range of 500 ~ 2000 ℃.

When the air gap forming film is made of SiC, Si, or a group 3-5 compound semiconductor, the step of forming the buffer layer includes α-Al ₂ O ₃ or γ-Al ₂ O ₃ , MgO, SrTiO ₃ , or YSZ It may include the step of sequentially laminating an oxide layer made of a metal oxide, and a metal layer made of a material containing Ni or a platinum group metal containing Ir, Pt, or Rh.

When the air gap forming film is made of SiC, Si, or a group 3-5 compound semiconductor, forming the buffer layer may include forming a layer containing SiC.

When the air gap forming film is made of Al ₂ O ₃ , MgO, YSZ, Iridium, Quartz, Platinum, or SrTiO 3, the forming of the buffer layer may include a platinum group metal or Ni-containing material including Ir, Pt, or Rh It may include the step of forming a metal layer consisting of.

In the forming of the buffer layer, ALD (atomic layer deposition), CVD (chemical vapor deposition), or PVD (physical vapor deposition) is used.

The step of forming the diamond thick film uses hot filament-CVD (HF-CVD), microwave plasma-CVD (MP-CVD), or RF plasma-CVD (RF-CVD) equipment as CVD (chemical vapor deposition) equipment. .

The forming of the diamond thick film may include forming a diamond crystal nucleus layer having a nuclear density of 10 ⁵ cm ^-2 or more; And growing a single crystal diamond thick film on the diamond crystal nucleus layer.

According to the method of manufacturing a single crystal diamond substrate according to the present invention, a simple process of heterogeneous growth of a large area/large diameter single crystal diamond as a method of forming an air gap structure using a photoresist pattern on a substrate such as sapphire (Al ₂ O ₃ ) and By applying a low-cost growth method, the stress due to the difference in the lattice constant and the coefficient of thermal expansion with the dissimilar substrate is relieved, and defects and cracks are reduced even when the temperature decreases to produce a high-quality single crystal diamond substrate. Self-separation can be easily achieved.

For example, the present invention forms patterns in various forms using a semiconductor photolithography process on a sapphire (Al ₂ O ₃ ) substrate, deposits Al ₂ O ₃ thereon, and heat-treats to remove the photoresist inside the patterns. As the Al ₂ O ₃ film outside the pattern is crystallized in the same orientation as the sapphire substrate below, an air gap is formed between the sapphire substrate and the Al ₂ O ₃ thin film, and a single crystal diamond is grown thereon. As described above, when diamonds are grown on the air gap structure, defects in diamonds are reduced through lateral growth of diamond materials grown on patterns spaced apart from each other, and when cooled due to a stress reduction effect between the heterogeneous substrate and the diamond growth layer. It is possible to manufacture a large-diameter single crystal diamond substrate that is self-separating by reducing the occurrence of defects or cracks.

The accompanying drawings included as part of the detailed description to aid understanding of the present invention provide embodiments of the present invention and describe the technical spirit of the present invention together with the detailed description.

1 is a process flow chart for explaining a method of manufacturing a single crystal diamond substrate according to an embodiment of the present invention.

FIG. 2 is a diagram for comparing the difference in defects between the existing diamond substrate and the diamond substrate based on the process of FIG. 1.

FIG. 3 is an example of a scanning electron microscope photograph of a form in which an air gap is formed based on the process of FIG. 1.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. At this time, the same components in each drawing are denoted by the same reference numerals as possible. In addition, detailed descriptions of already known functions and/or configurations are omitted. The contents disclosed below focus on parts necessary for understanding the operation according to various embodiments, and descriptions of elements that may obscure the subject matter of the description will be omitted. Also, some components of the drawings may be exaggerated, omitted, or schematically illustrated. The size of each component does not entirely reflect the actual size, and thus the contents described herein are not limited by the relative size or spacing of the components drawn in each drawing.

In describing the embodiments of the present invention, when it is determined that a detailed description of known technology related to the present invention may unnecessarily obscure the subject matter of the present invention, the detailed description will be omitted. In addition, terms to be described later are terms defined in consideration of functions in the present invention, which may vary according to a user's or operator's intention or practice. Therefore, the definition should be made based on the contents throughout this specification. The terminology used in the detailed description is only for describing embodiments of the present invention and should not be limiting. Unless expressly used otherwise, a singular form includes a plural form. In this description, expressions such as “including” or “equipment” are intended to indicate certain characteristics, numbers, steps, actions, elements, parts or combinations thereof, and one or more other than described. It should not be interpreted to exclude the presence or possibility of other characteristics, numbers, steps, actions, elements, or parts or combinations thereof.

Further, terms such as first and second may be used to describe various components, but the components are not limited by the terms, and the terms are used to distinguish one component from other components. Used only.

1 is a process flow diagram for explaining a method of manufacturing a single crystal diamond substrate according to an embodiment of the present invention.

Referring to FIG. 1, a method of manufacturing a single crystal diamond substrate according to an embodiment of the present invention includes forming a repeating photoresist pattern 20 on the lower substrate 10 (S111) and an air gap forming film ( 30) depositing (S112), removing the photoresist by heat treatment and forming an air gap 25 between the lower substrate 10 and the air gap forming layer 30 (S121), buffer layer 40 ) Forming (S122), diamond nucleation layer 50, forming diamond thick film 60 (S131, S132) and cooling the diamond thick films 50 and 60 to be separated from the lower substrate 10 by itself (S141), obtaining a high-quality diamond substrate separated from the lower substrate 10 (S142). The diamond thick films 50 and 60 may be, for example, 1000 nm to 100 mm thick, and separated from the lower substrate 10 to be used as a bulk substrate for forming various electronic devices such as transistors, diodes, and LEDs (light emitting diodes). Can be.

Hereinafter, a method of manufacturing a single crystal diamond substrate according to an embodiment of the present invention will be described in more detail.

First, the lower substrate 10 is prepared. The lower substrate 10 is sapphire (Al ₂ O ₃ ) Although it is preferable to be a substrate, in addition to MgO substrate, Iridium substrate, Quartz substrate, Platinum substrate SiC substrate, YSZ (Yttria Stabilized Zirconia) substrate, SrTiO3 substrate, silicon substrate, SOI (Silicon on Insulator) substrate or group 3-5 compound semiconductor ( For example, a GaN, etc.) substrate may be used. Hereinafter, as the lower substrate 10, sapphire (Al ₂ O ₃ ) Although an example using a substrate is mainly described, it is not limited thereto, and it can be well understood to those skilled in the art that various substrates as described above can be similarly applied even when used as the lower substrate 10. The size of the lower substrate 10 may be about 1x1 mm ² engraving specimens for experimental purposes, but substrates of various sizes suitable for purposes up to 12-inch large-diameter wafers or larger for obtaining large-area/large-diameter single crystal diamond substrates This is possible.

When the lower substrate 10 is prepared as described above, a repeating photoresist pattern 20 is formed on the lower substrate 10 (S111). For example, the photoresist pattern 20 may be formed by applying the photoresist 20 on the lower substrate 10 and exposing and developing with an electron beam, X-rays, or ultraviolet rays using a photolithography equipment such as a stepper. The shape of the photoresist pattern 20 formed in this way includes a stripe, a circle, or a polygon (eg, triangle, square, etc.). The photoresist pattern 20 may be embossed or engraved to have such a shape. The size of each photoresist pattern 20 may range from 1 nm to 100 μm in diameter and may range from 1 nm to 100 μm in thickness.

When the repeating photoresist pattern 20 is formed on the lower substrate 10, the air gap forming film 30 is then deposited (S112). Air gap forming film 30, Al ₂ O ₃ , MgO, Iridium Quartz, Platinum, SiC, YSZ, SrTiO3, Si, or a group 3-5 compound semiconductor material may be formed in a thickness of 10nm ~ 10㎛ range . For example, when the lower substrate 10 is a sapphire (Al ₂ O ₃ ) substrate, the air gap forming film 30 is also preferably formed of Al ₂ O ₃ , but is not limited thereto, as described below. It is possible to form the air gap forming film 30 from various materials as above, which can be combined with the lower substrate 10.

Thereafter, the photoresist forming the photoresist pattern 20 is removed by heat treatment using a furnace or the like, and an air gap 25 is formed between the lower substrate 10 and the air gap forming layer 30 (S121). In order to form the air gap 25, a heat treatment temperature may be performed in a range of 500 to 2000°C. By this heat treatment, the air gap forming film 30 is crystallized in the same orientation as the lower substrate 10 (eg, covalent bonding, ionic bonding, etc.), and the photoresist is small in the air gap forming film 30. The air gap 25 is formed as an empty space at the position where the photoresist was evaporated through the gap.

By forming the air gap 25, the elasticity of the air gap forming film 30 is increased to reduce stress due to a difference in lattice constant and thermal expansion coefficient when forming the single crystal diamond thick films 50 and 60 in a subsequent process. It is possible to obtain a diamond substrate by alleviating and reducing defects or cracks in the diamond thick films 50 and 60 upon cooling.

After the air gap 25 is formed in this way, the buffer layer 40 is formed next (S122). The buffer layer 40 is formed as a buffer layer in consideration of comparison of lattice constants, stress generation, and the like before forming the single crystal diamond thick films 50 and 60. The buffer layer 40 may be formed as a single layer or a double layer with a total thickness of 10 nm to 100 μm in consideration of bonding properties of the upper and lower layers. The buffer layer 40 may be formed using ALD (atomic layer deposition), CVD (chemical vapor deposition), or PVD (physical vapor deposition).

For example, when the air gap forming film 30 is made of an oxide type such as Al ₂ O ₃ , MgO, YSZ, Iridium, Quartz, Platinum or SrTiO 3, the buffer layer 40 includes Ir, Pt, or Rh It may be formed of a metal layer made of a platinum group metal or a material containing Ni.

Further, for example, when the air gap forming film 30 is made of a semiconductor type such as SiC, Si, or a group 3-5 compound semiconductor, the buffer layer 40 may be formed of a layer containing SiC.

In addition, when the air gap forming film 30 is made of a semiconductor type such as SiC, Si, or a group 3-5 compound semiconductor, as a double layer, α-Al ₂ O ₃ or γ-Al ₂ O ₃ , MgO, SrTiO ₃ Alternatively, an oxide layer made of a metal oxide containing YSZ and a metal layer made of a material containing Ni or a platinum group metal containing Ir, Pt, or Rh may be formed as a double layer.

Thereafter, single crystal diamond thick films 50 and 60 are formed on the buffer layer 40 (S131 and S132). The single crystal diamond thick films 50 and 60 are CVD (chemical vapor deposition) equipment such as hot filament-CVD (HF-CVD), microwave plasma-CVD (MP-CVD), or RF plasma-CVD (RF-CVD) equipment. Can be used.

The single crystal diamond thick films 50 and 60 first form a diamond crystal nucleus 50 having a nuclear density (eg, BEN (Bias Enhanced Nucleation) diamond density) of 10 ⁵ cm ^-2 or more (S131), and then the diamond crystal nuclei are formed. The single crystal diamond thick film layer 60 is formed by growing (S132) in the range of 1000 nm to 100 mm in thickness, for example, by fully depositing the diamond single crystal on the entire surface by using it as a seed. For example, when the single crystal diamond thick film layer 60 is grown by using the MP-CVD method, at a growth temperature of 100 to 1500° C. in a chamber, a plasma power of 0.5 to 100 KW, a growth pressure of 0 to 1000 torr, H ₂ About The ratio of CH ₄ , O ₂ , Ar, and N ₂ (supply gas ratio) is appropriately adjusted in a range of 0.1 to 50%, and a thickness growth rate of 10 nm to 1000 μm/hr can be obtained. In this way, as the diamond crystals are grown on the patterns spaced apart from each other by the photoresist pattern 20, the groove portion with the step difference between the patterns is also filled through side growth, and the single crystal diamond thick film in a form in which defects in the diamond are reduced. Layer 60 may be formed.

Thereafter, the diamond thick films 50 and 60 are cooled to self-separate from the lower substrate 10 (S141), thereby obtaining a high-quality diamond substrate separated from the lower substrate 10 (S142).

The substrates having the separated thick films (eg, thickness of 1000 nm to 100 mm) in the form of single crystal diamond thick films 50 and 60 may be single crystal diamond substrates that can be used as bulk substrates for the formation of various electronic devices.

2 is a view for comparing the defect difference between the existing diamond substrate (a) and the diamond substrate (b) based on the process of FIG. 1.

As shown in (b) of FIG. 2, by forming the air gap 25, the stress due to the difference in the lattice constant and the coefficient of thermal expansion between the lower substrate 10 and the different diamond thick films 50 and 60 is relieved and the diamond is cooled. The defects or cracks were reduced in the thick films 50 and 60 to obtain a diamond substrate.

3 is an example of a scanning electron microscope (SEM) photograph of a form in which the air gap 25 is formed based on the process of FIG. 1.

Figure 3 using sapphire (Al ₂ O ₃₎ substrate to the lower substrate 10 and the case of forming by using sapphire (Al ₂ O ₃₎ as the air gap forming film 30, shown in the first figure of the upper left It shows each selected area electron diffraction (SAED) pattern for the corresponding crystal plane orientation of the five points. Through this electron diffraction pattern, the air gap forming film 30 is crystallized in the same sapphire (Al ₂ O ₃ ) crystal plane orientation as the lower substrate 10, and shows a bonded (eg covalent bond, ionic bond, etc.) state. , It can be seen that the structure of the air gaps 25 formed corresponding to the repeated photoresist pattern 20 is well formed.

As described above, according to the method for manufacturing a single crystal diamond substrate according to the present invention, a large area is formed by a method of forming an air gap 25 structure using a photoresist pattern 20 on a substrate such as sapphire (Al ₂ O ₃ ) High quality single crystal diamond by reducing the stress caused by the difference in the lattice constant and the coefficient of thermal expansion with a heterogeneous substrate and reducing the occurrence of defects or cracks even when the temperature decreases by applying a simple process of low-growth growth of large-diameter single crystal diamonds and a low-cost growth method. The substrate can be fabricated and self-separation of the diamond substrate from the dissimilar substrate can be easily achieved. For example, the present invention forms patterns in various forms using a semiconductor photolithography process on a sapphire (Al ₂ O ₃ ) substrate, deposits Al ₂ O ₃ thereon, and heat-treats to remove the photoresist inside the patterns. As the Al ₂ O ₃ film outside the pattern is crystallized in the same orientation as the sapphire substrate below, an air gap is formed between the sapphire substrate and the Al ₂ O ₃ thin film, and a single crystal diamond is grown thereon. As described above, when diamonds are grown on the air gap structure, defects in diamonds are reduced through lateral growth of diamond materials grown on patterns spaced apart from each other, and when cooled due to a stress reduction effect between the heterogeneous substrate and the diamond growth layer. It is possible to manufacture a large-diameter single crystal diamond substrate that is self-separating by reducing the occurrence of defects or cracks.

As described above, in the present invention, specific matters such as specific components and the like have been described by limited embodiments and drawings, but these are provided only to help a more comprehensive understanding of the present invention, and the present invention is not limited to the above embodiments , Those of ordinary skill in the art to which the present invention pertains will be able to make various modifications and variations without departing from the essential characteristics of the present invention. Therefore, the spirit of the present invention is not limited to the described embodiments, and should not be determined, and all technical spirits equivalent to or equivalent to the claims as well as the claims described below are included in the scope of the present invention. It should be interpreted as.

Claims (14)

Forming a repeating photoresist pattern on the lower substrate; Depositing an air gap forming film; Removing the photoresist by heat treatment and forming an air gap between the lower substrate and the air gap forming film; Forming a buffer layer; Forming a diamond thick film; And Cooling the diamond thick film to self-separate from the lower substrate Diamond substrate manufacturing method comprising a. According to claim 1, The shape of the photoresist pattern is embossed or engraved as a diamond substrate manufacturing method, characterized in that it comprises a stripe, circular, or polygonal shape. According to claim 1, In the step of forming the air gap, the air gap forming film is crystallized in the same orientation as the lower substrate by the heat treatment, and the photoresist is evaporated to form the air gap at the position where the photoresist was. Diamond substrate manufacturing method. According to claim 1, By forming the air gap, the stress due to the difference in the lattice constant and the coefficient of thermal expansion between the lower substrate and the different types of diamond thick film is relieved, and when the cooling occurs, defects or cracks in the diamond thick film are reduced to obtain a diamond substrate. Method for manufacturing a diamond substrate, characterized in that for. According to claim 1, The lower substrate, Al ₂ O ₃ substrate, MgO substrate, Iridium substrate, Quartz substrate, Platinum substrate, SiC substrate, YSZ substrate, SrTiO3 substrate, silicon substrate, SOI substrate, or a method of manufacturing a diamond substrate, characterized in that a group 3-5 semiconductor semiconductor substrate. According to claim 1, The air gap forming film, Al ₂ O ₃ , MgO, Iridium, Quartz, Platinum, SiC, YSZ, SrTiO3, Si or diamond substrate manufacturing method characterized in that it is formed of a group 3-5 compound material. According to claim 1, In the step of forming the air gap, the heat treatment temperature is 500 ~ 2000 ℃ diamond diamond manufacturing method characterized in that the range. According to claim 1, When the air gap forming film is made of SiC, Si, or a group 3-5 compound semiconductor, The forming of the buffer layer may include an oxide layer made of a metal oxide containing α-Al ₂ O ₃ or γ-Al ₂ O ₃ , MgO, SrTiO ₃ , or YSZ, and a platinum group including Ir, Pt, or Rh. And sequentially depositing a metal layer made of a metal or a material containing Ni. According to claim 1, When the air gap forming film is made of SiC, Si, or a group 3-5 compound semiconductor, The step of forming the buffer layer includes forming a layer containing SiC. According to claim 1, When the air gap forming film is made of Al ₂ O ₃ , MgO, YSZ, Iridium, Quartz, Platinum or SrTiO3, The forming of the buffer layer may include forming a metal layer made of a platinum group metal containing Ir, Pt, or Rh or a material containing Ni. According to claim 1, The step of forming the buffer layer, A method of manufacturing a diamond substrate, characterized by using ALD (Atomic Layer Deposition), CVD (Chemical Vapor Deposition), or PVD (Physical Vapor Deposition). According to claim 1, The step of forming the diamond thick film, A method of manufacturing a diamond substrate, characterized by using hot filament-CVD (HF-CVD), microwave plasma-CVD (MP-CVD), or RF plasma-CVD (RF-CVD) equipment as CVD (chemical vapor deposition) equipment. According to claim 1, The step of forming the diamond thick film, Forming a diamond crystal nucleus layer having a nuclear density of 10 ⁵ cm ^-2 or more; And Growing a single crystal diamond thick film on the diamond crystal nucleus layer Diamond substrate manufacturing method comprising a. A diamond substrate manufactured by the method for manufacturing the diamond substrate of claim 1.

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