JP2004193631A5 - - Google Patents
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- JP2004193631A5 JP2004193631A5 JP2004081316A JP2004081316A JP2004193631A5 JP 2004193631 A5 JP2004193631 A5 JP 2004193631A5 JP 2004081316 A JP2004081316 A JP 2004081316A JP 2004081316 A JP2004081316 A JP 2004081316A JP 2004193631 A5 JP2004193631 A5 JP 2004193631A5
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- 229910010271 silicon carbide Inorganic materials 0.000 claims description 67
- 239000013078 crystal Substances 0.000 claims description 61
- HBMJWWWQQXIZIP-UHFFFAOYSA-N silicon carbide Chemical compound [Si+]#[C-] HBMJWWWQQXIZIP-UHFFFAOYSA-N 0.000 claims description 39
- 239000010409 thin film Substances 0.000 claims description 30
- 239000000758 substrate Substances 0.000 description 34
- 229910052799 carbon Inorganic materials 0.000 description 29
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 26
- 125000004429 atom Chemical group 0.000 description 18
- 238000003763 carbonization Methods 0.000 description 11
- 229910052710 silicon Inorganic materials 0.000 description 9
- 230000007547 defect Effects 0.000 description 6
- 238000000034 method Methods 0.000 description 6
- 238000010586 diagram Methods 0.000 description 5
- 230000008707 rearrangement Effects 0.000 description 5
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 4
- 150000001721 carbon Chemical group 0.000 description 4
- 238000001362 electron spin resonance spectrum Methods 0.000 description 4
- 238000004519 manufacturing process Methods 0.000 description 4
- 239000010703 silicon Substances 0.000 description 4
- 230000015572 biosynthetic process Effects 0.000 description 3
- 238000010894 electron beam technology Methods 0.000 description 3
- 239000010408 film Substances 0.000 description 3
- 239000007789 gas Substances 0.000 description 3
- 125000004432 carbon atom Chemical group C* 0.000 description 2
- 229910021419 crystalline silicon Inorganic materials 0.000 description 2
- 238000002128 reflection high energy electron diffraction Methods 0.000 description 2
- 239000004065 semiconductor Substances 0.000 description 2
- 239000004215 Carbon black (E152) Substances 0.000 description 1
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- 229910018540 Si C Inorganic materials 0.000 description 1
- OKTJSMMVPCPJKN-YPZZEJLDSA-N carbon-10 atom Chemical compound [10C] OKTJSMMVPCPJKN-YPZZEJLDSA-N 0.000 description 1
- 238000010000 carbonizing Methods 0.000 description 1
- 230000000052 comparative effect Effects 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 229910002804 graphite Inorganic materials 0.000 description 1
- 239000010439 graphite Substances 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 229930195733 hydrocarbon Natural products 0.000 description 1
- 150000002430 hydrocarbons Chemical class 0.000 description 1
- 238000010249 in-situ analysis Methods 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 230000009257 reactivity Effects 0.000 description 1
- 230000000717 retained effect Effects 0.000 description 1
- 238000001228 spectrum Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
Description
本発明は、高パワーデバイス・高温デバイス・耐環境性デバイスなどの半導体素子に応用可能なワイドバンドギャップ半導体材料である炭化珪素（SiC）の単結晶薄膜に関する。特に、Si基板表面にヘテロエピタキシャル成長させることにより、Siウェハ上に形成される結晶欠陥の少ない単相の3C-SiC単結晶薄膜に関する。 The present invention relates to a single crystal thin film of silicon carbide (SiC), which is a wide band gap semiconductor material applicable to semiconductor elements such as high power devices, high temperature devices, and environment resistant devices. In particular, the present invention relates to a single-phase 3C-SiC single crystal thin film with few crystal defects formed on a Si wafer by heteroepitaxial growth on the Si substrate surface.
従来、6H型、4H型のSiC単結晶基板は市販されているが、移動度が最も大きい3C-SiCに関しては、Si基板上にヘテロエピタキシャル成長させた結晶が形成されていた。Si基板表面に炭化珪素を成長させる場合は、まずSi表面に炭素水素ガスを供給し加熱して炭化させ、その後に炭素と珪素を供給して炭化珪素をヘテロエピタキシャル成長させていた（特許文献１）。
この従来の技術によって形成された炭化珪素薄膜は、SiC/Si界面において、高密度の格子欠陥・ツウィン等の成長が起こり、電子デバイスを形成するための炭化珪素基板を作成するためには問題であった。更に、Si基板上に２種類のフェーズの単結晶粒が成長し、お互いに異なるフェーズの２種類の結晶粒の界面にアンチフェーズバウンダリー(APB)が形成されて、欠陥が多数導入されて問題であった。 The silicon carbide thin film formed by this conventional technique grows at a high density of lattice defects, twins, etc. at the SiC / Si interface, which is a problem for producing a silicon carbide substrate for forming an electronic device. there were. Furthermore, single crystal grains of two types of phases grow on the Si substrate, and anti-phase boundary (APB) is formed at the interface between the two types of crystal grains of different phases. Met.
図１にSi表面に炭素を供給して加熱し、炭化させてSiC結晶粒を形成するプロセスのメカニズムの概念図を示す。清浄なSi(001)表面において、２本のダングリングボンドを有するSi原子が[110]方向に連なっている。このダングリングボンドを炭素原子によりコンペンセイトすると、Si-C-Si..と連なったSi-C原子列が[110]方向に連なって形成される。ここで、炭素原子１と結合したSi原子２とそのもう一層下のSi原子３との間のボンドが切断されると、上記[110]方向に連なるSi-C-Si..原子列１−２がSi[110]方向に収縮し、SiC原子構造が形成される。off-cutの無いjust Si(001)表面においては、Si[110]方向と直行する下記式（数１）方向は区別することができず、Si(001)表面に同じ確立で現れる。 FIG. 1 shows a conceptual diagram of a process mechanism for forming SiC crystal grains by supplying carbon to the Si surface, heating it, and carbonizing it. On a clean Si (001) surface, Si atoms having two dangling bonds are connected in the [110] direction. When this dangling bond is compensated by carbon atoms, a Si-C atom string connected to Si-C-Si .. is formed in the [110] direction. Here, when the bond between the Si atom 2 bonded to the carbon atom 1 and the Si atom 3 therebelow is cut, the Si—C—Si.. 2 contracts in the Si [110] direction to form a SiC atomic structure. On the just Si (001) surface without off-cut, the direction of the following formula (Equation 1) perpendicular to the Si [110] direction cannot be distinguished, and appears on the Si (001) surface with the same probability.
このため、上記Si[110]方向への収縮は互いに直行する２方向に対してほぼ同じ確立で起こり、この異なる方向性を有する２種類のSiC結晶粒は互いに異なるフェーズを有する。異なるフェーズを有するSiC結晶粒は、成長によって互いに結合して一体になることが出来ず、界面にAPBを含む２フェーズの薄膜となってしまい問題であった。 For this reason, the shrinkage in the Si [110] direction occurs with almost the same probability with respect to the two directions orthogonal to each other, and the two types of SiC crystal grains having different directions have phases different from each other. The SiC crystal grains having different phases cannot be bonded to each other by growth and become a two-phase thin film containing APB at the interface.
本発明は、前記従来の問題を解決するため、Si基板表面にヘテロエピタキシャル成長させることにより、Siウェハ上に結晶欠陥の少ない単相の3C-SiC単結晶薄膜を提供することを目的とする。 An object of the present invention is to provide a single-phase 3C—SiC single crystal thin film with few crystal defects on a Si wafer by heteroepitaxial growth on the surface of the Si substrate in order to solve the conventional problems.
前記目的を達成するため、本発明の炭化珪素薄膜は、炭化珪素結晶であって、方向のそろった異方性を有する炭化珪素結晶粒から構成される部分を含み、前記炭化珪素結晶粒は炭化珪素結晶3C-SiC[110]方向に短く前記結晶方向と垂直な3C-SiC[110]方向に長い異方性を有する結晶粒であることを特徴とする。 In order to achieve the above object, a silicon carbide thin film of the present invention includes a portion composed of silicon carbide crystals having silicon carbide crystals having uniform anisotropy, and the silicon carbide crystals are carbonized. The crystal grains are characterized by being short in the silicon crystal 3C-SiC [110] direction and having long anisotropy in the 3C-SiC [110] direction perpendicular to the crystal direction.
本発明によれば、炭化珪素結晶であって、方向のそろった異方性を有する炭化珪素結晶粒から構成される部分を含み、前記炭化珪素結晶粒は炭化珪素結晶3C-SiC[110]方向に短く前記結晶方向と垂直な3C-SiC[110]方向に長い異方性を有する結晶粒であることを特徴とすることにより、Si基板表面にヘテロエピタキシャル成長させ、Siウェハ上に結晶欠陥の少ない単相の3C-SiC単結晶薄膜を得ることができる。 According to the present invention, the silicon carbide crystal includes a portion composed of silicon carbide crystal grains having uniform anisotropy, and the silicon carbide crystal grains have a silicon carbide crystal 3C-SiC [110] direction. It is characterized by the fact that the crystal grains have a short anisotropy in the 3C-SiC [110] direction perpendicular to the crystal direction, so that they are heteroepitaxially grown on the surface of the Si substrate and have few crystal defects on the Si wafer. A single phase 3C-SiC single crystal thin film can be obtained.
また本発明の炭化珪素薄膜により、APBを含まない単相の3C-SiC単結晶薄膜が制御性良く成長可能となり、電子デバイスに応用可能な3C-SiC単結晶薄膜が、Si基板上に形成できるようになった。 In addition, the silicon carbide thin film of the present invention allows a single-phase 3C-SiC single crystal thin film containing no APB to be grown with good controllability, and a 3C-SiC single crystal thin film applicable to electronic devices can be formed on a Si substrate. It became so.
本発明の異方性をつけてテラスとステップを導入したSi基板表面の模式図を図２に示す。Si(001)表面４が[110]方向に傾けてoff-cutされており、テラス５とステップ６が導入されている。テラスの幅（ステップエッジと垂直方向：図２中のN方向７）は、ステップエッジと平行（図２中のP方向８）なテラスの長さに比べて非常に短く、off-cut角度が４度でステップ６の高さが１原子層の場合は、20オングストローム程度である。この短く連なったSi[110]原子列（図２のN方向７）は、長く連なっている図２のP方向８のSi[110]原子列に比べて、炭素と反応して収縮しSiC原子構造を形成することが容易である。つまり、テラスとステップが導入された表面においては、テラスの幅方向（図２のN方向７）のSi[110]原子列が選択的に収縮し供給炭素９とともにSiC原子構造を形成する。このように、just Si(001)表面に形成され問題であった２つのフェーズのSi結晶粒が、テラスとステップの導入により１つのフェーズに限定され単相のSiC単結晶薄膜となることを本発明者は確認した。 FIG. 2 shows a schematic diagram of the Si substrate surface with terraces and steps with anisotropy of the present invention. The Si (001) surface 4 is tilted in the [110] direction and is off-cut, and the terrace 5 and step 6 are introduced. The terrace width (perpendicular to the step edge: N direction 7 in FIG. 2) is very short compared to the terrace length parallel to the step edge (P direction 8 in FIG. 2), and the off-cut angle is If it is 4 degrees and the height of step 6 is one atomic layer, it is about 20 angstroms. This short chain of Si [110] atoms (N direction 7 in FIG. 2) reacts with carbon and contracts with SiC atoms compared to the long chain of Si [110] atoms in P direction 8 in FIG. It is easy to form a structure. That is, on the surface where the terrace and the step are introduced, the Si [110] atomic sequence in the terrace width direction (N direction 7 in FIG. 2) selectively contracts to form a SiC atomic structure with the supplied carbon 9. In this way, the two-phase Si crystal grains formed on the surface of just Si (001) are limited to one phase by the introduction of terraces and steps and become a single-phase SiC single crystal thin film. The inventor confirmed.
テラス５とステップ６を含むSi(001)表面に炭素９を供給し炭化しSiC結晶粒を形成する場合、炭素９を炭化水素などのガス状の物質として供給するとツウィンが形成されやすく、例えば炭素原子などの分子線を含む炭素源を供給するとツウィンの形成が抑制されることも、本発明者は確認した。これは、次のような理由によると考えられる。ガスフェーズの炭素源とSi表面との反応を考えると、Si表面で最も反応性の高い状態にある原子から炭素との反応が始まると考えられる。Si表面で最も反応性の高い状態にあるSi原子は、表面に存在するステップエッジ１０の位置にある原子であり、ガスフェーズの炭素９によるSi表面４の炭化は、ステップエッジ１０から始まると考えられる。ステップエッジ１０においては、基板のSi原子配列に段差が存在するため、その位置から方位の異なるツウィンが成長しやすい。一方、ガスフェーズの炭素だけでなく、例えば炭素原子などの分子線を含む炭素源を供給すると、Si基板との反応が、炭素が供給された任意の位置から起こり、ステップエッジ１０の位置から選択的に起こることが抑制されテラス５上で起こる。このため、ステップエッジ１０の位置からのツウィンの成長も抑制され、ツウィンの少ないSiC結晶薄膜が形成されることを確認した。 When carbon 9 is supplied to the Si (001) surface including terrace 5 and step 6 and carbonized to form SiC crystal grains, twins are easily formed when carbon 9 is supplied as a gaseous substance such as hydrocarbon. The present inventor has also confirmed that formation of twins is suppressed when a carbon source including a molecular beam such as an atom is supplied. This is considered to be due to the following reasons. Considering the reaction between the carbon source in the gas phase and the Si surface, it is considered that the reaction with the carbon starts from the atom in the most reactive state on the Si surface. The Si atom in the most reactive state on the Si surface is the atom at the position of the step edge 10 existing on the surface, and the carbonization of the Si surface 4 by the carbon 9 in the gas phase starts from the step edge 10. It is done. At the step edge 10, there is a step in the Si atom arrangement of the substrate, and thus twins with different orientations are likely to grow from that position. On the other hand, when supplying not only carbon in the gas phase but also a carbon source including a molecular beam such as a carbon atom, the reaction with the Si substrate occurs from any position where the carbon is supplied, and is selected from the position of the step edge 10. Happening on the terrace 5 is suppressed. For this reason, it was confirmed that the growth of twins from the position of the step edge 10 was suppressed and a SiC crystal thin film with few twins was formed.
以下実施例により本発明をさらに具体的に説明する。 Hereinafter, the present invention will be described more specifically with reference to examples.
（実施例１）
まず、Si(001) 4度-offcut基板をMBE装置内に導入し、10-9Torr以下の高真空下で９００℃以上に加熱し、RHEED観察によりSi(001)(2x1)表面再配列が観測されるSi清浄表面を形成した。この清浄表面を４００℃以下に冷却した後、昇温速度１００−２５０℃／分で昇温した。基板温度が４００℃に達した時点から、黒鉛粒を充填した坩堝に電子銃を照射する電子線蒸着器から炭素原子を蒸発させて、基板表面に供給した。この場合の坩堝から基板までの距離は４０ｃｍ程度で、電子線蒸着器への供給電力は、８kV,100mA程度が適当であった。基板温度は、炭素の供給を受けつつ昇温され、昇温過程で炭化処理がなされた。この場合、上記offcut基板を用いると、炭化過程で形成されるSiC結晶粒の結晶方向が揃うことが確認された。これは、図２に示したように、offcut基板表面にはテラス５とステップ６が多数存在し、ステップエッジ１０に平行な長く連なる原子列のＰ方向８と、ステップエッジ１０に垂直でステップエッジ１０により分断された短いテラス上の原子列のＮ方向７について異なった表面反応性を示すためである。
(Example 1)
First, a Si (001) 4 degree-offcut substrate was introduced into the MBE apparatus, heated to 900 ° C or higher under high vacuum of 10 -9 Torr or less, and Si (001) (2x1) surface rearrangement was observed by RHEED observation. The observed Si clean surface was formed. After this clean surface was cooled to 400 ° C. or lower, the temperature was increased at a temperature increase rate of 100-250 ° C./min. When the substrate temperature reached 400 ° C., carbon atoms were evaporated from an electron beam evaporator that irradiates an electron gun onto a crucible filled with graphite grains, and supplied to the substrate surface. In this case, the distance from the crucible to the substrate was about 40 cm, and the power supplied to the electron beam evaporator was suitably about 8 kV, 100 mA. The substrate temperature was raised while receiving the supply of carbon, and carbonization was performed during the temperature raising process. In this case, it was confirmed that when the above-mentioned offcut substrate was used, the crystal directions of the SiC crystal grains formed during the carbonization process were aligned. As shown in FIG. 2, there are a large number of terraces 5 and steps 6 on the surface of the offcut substrate, the P direction 8 of the long atomic sequence parallel to the step edge 10, and the step edge perpendicular to the step edge 10. This is because different surface reactivity is exhibited in the N direction 7 of the atomic column on the short terrace divided by 10.
炭素原子１がSi(001)表面のSi[110]原子列２と反応して収縮することが、炭化の基本メカニズムであるため、Si[110]の原子列の連なりが短い方がより容易に収縮することができ、均一な3C-SiC(001)/Si(001)界面が形成できると考えられる。上記図２のoffcut基板表面においては、上記Ｎ方向にSi[110]原子列の収縮が容易に起こり、3C-SiC結晶の[110]のSi(下)C(上)方向がＮ方向と一致する。 Since the basic mechanism of carbonization is that carbon atom 1 reacts with Si [110] atom sequence 2 on the Si (001) surface and contracts, it is easier when the sequence of Si [110] atom sequences is shorter. It can be shrunk and a uniform 3C-SiC (001) / Si (001) interface can be formed. On the surface of the offcut substrate in FIG. 2 above, the Si [110] atomic column easily contracts in the N direction, and the [110] Si (lower) C (upper) direction of the 3C-SiC crystal coincides with the N direction. To do.
基板温度が１０５０℃に達した時点から、炭素に加えて珪素もクヌーセンセルから供給され、その後は１０５０℃に保持された。この場合のSiクヌーセンセルの温度は１３５７℃に保たれた。基板表面の結晶性は、MBEの成長室中で常にRHEEDにより観測されており、in-situ分析が行われている。3C-SiC(001)成長表面に供給されるC/Si量は、3C-SiC(001)表面が安定な(3x2)表面再配列構造を常に保つように制御された（表面制御成長）。3C-SiC(001)(3x2)表面は、Si-terminated表面に過剰なSi原子が付加された構造を有し、C/Si=1のSiCの構造に比べてSi過剰な表面となっている。この表面制御成長による3C-SiC(001)表面の成長は、常にSi過剰な表面からSi原子が供給されるため、Si(上)C(下)の方向への成長が選択的に起こり結晶粒がこの方向へより長く成長する。この結晶粒の選択成長方向がoff-cut基板表面のテラス上に長く連なっている図２中のＰ方向８に一致していれば、結晶粒の成長がテラス上でステップによる妨害無しに進行し、容易に単相の3C-SiC単結晶の成長が得られる。一方上記結晶方向と９０度の関係にあるアンチフェーズドメインは、選択成長方向が図２中のＮ方向７となり、成長がステップによって常に阻害される。上記２種類のアンチフェーズドメインが成長する場合には、選択成長方向がＰ方向８に一致している結晶粒が選択的に成長し、もう一方のアンチフェーズドメインは成長に伴って消失してゆくと考えられる。上記、off-cut表面の炭化によって形成される3C-SiCの結晶方向はSi(下)C(上)//N方向であったが、この結晶方位は、テラス上の選択成長を考慮したSi(上)C(下)//P方向と一致する。つまり、上記炭化処理と表面制御成長を行えば、方位の揃った3C-SiC単結晶が選択的に成長し、他のアンイフェーズドメインの成長は阻害され、ある程度の膜厚を成長させれば単相の3C-SiC単結晶薄膜が得られる。 When the substrate temperature reached 1050 ° C., silicon was also supplied from the Knudsen cell in addition to carbon, and thereafter maintained at 1050 ° C. The temperature of the Si Knudsen cell in this case was maintained at 1357 ° C. The crystallinity of the substrate surface is always observed by RHEED in the MBE growth chamber, and in-situ analysis is performed. The amount of C / Si supplied to the 3C-SiC (001) growth surface was controlled so that the 3C-SiC (001) surface always maintained a stable (3x2) surface rearrangement structure (surface controlled growth). The 3C-SiC (001) (3x2) surface has a structure in which excess Si atoms are added to the Si-terminated surface, and has a Si-rich surface compared to the structure of SiC with C / Si = 1. . The growth of 3C-SiC (001) surface by this surface-controlled growth is always supplied with Si atoms from the Si-rich surface, so that the growth in the direction of Si (upper) and C (lower) occurs selectively. Grow longer in this direction. If the selective growth direction of the crystal grains coincides with the P direction 8 in FIG. 2 which is long and continuous on the terrace on the surface of the off-cut substrate, the growth of the crystal grains proceeds on the terrace without interference by steps. Therefore, single-phase 3C-SiC single crystal growth can be easily obtained. On the other hand, in the anti-phase domain having a relationship of 90 degrees with the crystal direction, the selective growth direction is the N direction 7 in FIG. 2, and the growth is always inhibited by the step. When the above two types of anti-phase domains grow, crystal grains whose selective growth direction coincides with the P direction 8 selectively grow, and the other anti-phase domain disappears with the growth. it is conceivable that. The crystal orientation of 3C-SiC formed by carbonization of the off-cut surface was the Si (lower) C (upper) // N direction, but this crystal orientation was determined by considering the selective growth on the terrace. (Upper) C (Lower) Aligns with // P direction. In other words, if the above carbonization treatment and surface controlled growth are performed, 3C-SiC single crystals with uniform orientation grow selectively, the growth of other aninphase domains is inhibited, and if a certain amount of film thickness is grown, the single crystal is grown. Phase 3C-SiC single crystal thin film is obtained.
図３に上記表面制御成長を３時間行った１０００オングストローム（１００ｎｍ）膜厚の単相3C-SiC(001)表面のSEM写真を示す。方位の揃った結晶粒がテラス上を選択的に成長しコアレスして大型の単結晶を形成していっているのが観察できる。膜厚１０００オングストローム（１００ｎｍ）に対して、観測されるそれぞれの結晶粒の大きさは１０００オングストローム（１００ｎｍ）程度であった。さらにこの薄膜の成長を続けると、膜厚の増大に伴ってこれらの結晶粒は更に大きくコアレスして大きな単結晶粒を形成した。 FIG. 3 shows a SEM photograph of a single-phase 3C—SiC (001) surface having a thickness of 1000 Å (100 nm) obtained by performing the above surface-controlled growth for 3 hours. It can be observed that crystal grains with uniform orientation are selectively grown on the terrace and coreless to form a large single crystal. For a film thickness of 1000 angstroms (100 nm), the size of each observed crystal grain was about 1000 angstroms (100 nm). Further, when the growth of this thin film was continued, as the film thickness increased, these crystal grains became more coreless and formed large single crystal grains.
図４に、この(a)１０００オングストローム（１００ｎｍ）厚の単相3C-SiC単結晶薄膜のESRスペクトルを、(b)just-cut Si(001)表面上に形成されたAPBを含む２フェーズの薄膜のESRスペクトルと比較して示す。(b)において観測される格子欠陥に対応するSiダングリングボンドのスペクトルが、本発明の炭化珪素薄膜の製造方法により形成された(a)においては確認されず,薄膜中のAPBに起因する格子欠陥が飛躍的に減少していることが確認された。 Figure 4 shows the ESR spectrum of this (a) 1000 angstrom (100 nm) thick single-phase 3C-SiC single crystal thin film, and (b) two-phase including APB formed on the just-cut Si (001) surface. It shows in comparison with the ESR spectrum of the thin film. The spectrum of Si dangling bonds corresponding to the lattice defects observed in (b) was not confirmed in (a) formed by the method for producing a silicon carbide thin film of the present invention, and was caused by APB in the thin film. It was confirmed that defects were dramatically reduced.
本実施例においては、異方性を有するSi基板としてoff-cut基板を用いたが、表面に異方性がありテラスとステップを含んでいれば、just-cut基板であって異方性エッチングなどにより表面に凸凹を付けた表面でも良く、off-cutの方向も[110]方向に限るものではなく、[110]方向と下記式（数２）方向について同等でなく異方性があればどの方向にoff-cutしたものでも良い。 In this example, an off-cut substrate was used as the Si substrate having anisotropy. However, if the surface has anisotropy and includes a terrace and a step, the substrate is a just-cut substrate and is anisotropically etched. For example, the surface may be uneven, and the off-cut direction is not limited to the [110] direction. If the [110] direction and the following equation (Equation 2) are not equal and anisotropic, It may be off-cut in any direction.
本実施例において、off-cutの角度は４度でテラスの幅は20オングストローム（２ｎｍ）程度であったが、off-cutの角度を変化させてテラス幅を変えても、テラス幅が５オングストローム（０．５ｎｍ）−１０００オングストローム（１００ｎｍ）の範囲では、良好な単相の3C-SiC単結晶薄膜が得られた。５オングストローム（０．５ｎｍ）以下のテラス幅の場合は、炭化によって多数のツウィンが形成され、単相の単結晶薄膜が形成できない。また、１０００オングストローム（１００ｎｍ）以上のテラス幅においては、炭化メカニズムにおいて異方性が有効に機能せず、APBを含む２フェーズの薄膜となった。 In this embodiment, the off-cut angle is 4 degrees and the terrace width is about 20 angstroms (2 nm). However, even if the terrace width is changed by changing the off-cut angle, the terrace width is 5 angstroms. In the range of (0.5 nm) -1000 angstroms (100 nm), a good single-phase 3C—SiC single crystal thin film was obtained. In the case of a terrace width of 5 angstroms (0.5 nm) or less, a large number of twins are formed by carbonization, and a single-phase single crystal thin film cannot be formed. In addition, at a terrace width of 1000 angstroms (100 nm) or more, anisotropy did not function effectively in the carbonization mechanism, resulting in a two-phase thin film containing APB.
本実施例においては、炭化処理において基板の昇温中に４００℃から炭素の供給を始めたが、６００℃以下の温度であれば適用でき、４００℃に限るものではない。６００℃以上の温度から炭素を供給し炭化するとSiC/Si界面にピットが形成され易くなり、薄膜中に結晶方位の異なる結晶粒が成長しやすい。 In the present embodiment, the carbon supply is started from 400 ° C. during the temperature raising of the substrate in the carbonization treatment, but it can be applied at a temperature of 600 ° C. or lower, and is not limited to 400 ° C. When carbon is supplied from a temperature of 600 ° C. or more and carbonized, pits are easily formed at the SiC / Si interface, and crystal grains having different crystal orientations are likely to grow in the thin film.
本実施例において、炭素は電子線蒸着器から原子またはクラスターの形で供給されており、ガス状の炭素の供給とは異なっている。本実施例の薄膜形成中にC2H4等のガス状の炭素源を5x10-8Torr以上供給すると、実施例で述べた単相の3C-SiCの形成が悪化、多数のツウィンが形成されることが確認された。このことより、本発明の炭化珪素薄膜の形成方法の実現のためには、ガス状ではない分子線の炭素の供給が必要であることが確認された。 In this embodiment, carbon is supplied in the form of atoms or clusters from an electron beam evaporator, which is different from the supply of gaseous carbon. When a gaseous carbon source such as C 2 H 4 is supplied in an amount of 5 × 10 −8 Torr or more during the thin film formation of this example, the formation of single-phase 3C—SiC described in the example deteriorates, and a large number of twins are formed. It was confirmed that From this, it was confirmed that the supply of molecular beam carbon that is not gaseous is necessary to realize the method for forming a silicon carbide thin film of the present invention.
本実施例においては、炭化後に炭素と珪素を供給して炭化珪素を成長させるプロセスにおいて、3C-SiC(001)表面が(3x2)の表面再配列を有しSiターミネイト(001)表面上に付加Siが存在するSi過剰な表面を保持して成長させた。表面再配列がSi過剰な他の再配列構造(5x2),(7x2),・・(2n+1,2)（nは任意の正の整数）を保持するように成長させた場合も本発明は有効であった。また、Siターミネイト(001)表面である(2x1)表面でも有効であった。 In this example, in the process of growing silicon carbide by supplying carbon and silicon after carbonization, the 3C-SiC (001) surface has a (3x2) surface rearrangement and is added onto the Si terminator (001) surface. The Si-excess surface where Si was present was retained and grown. The present invention also includes a case where the surface rearrangement is grown so as to retain other rearrangement structures (5x2), (7x2), ... (2n + 1,2) (n is an arbitrary positive integer) containing Si. Was effective. It was also effective on the (2x1) surface, which is the Si terminator (001) surface.
本実施例においては、Si(001)表面について説明したが、例えばSi(111)面のようなSi基板の他の表面でも本発明が有効であることを発明者は確認した。 In the present embodiment, the Si (001) surface has been described, but the inventors have confirmed that the present invention is effective for other surfaces of the Si substrate such as the Si (111) surface.
１ 炭素原子
２ 炭素と結合したSi基板原子（Si[110]原子列）
３ 炭素と結合したSi原子の一層下のSi基板原子
４ Si基板表面
５ テラス
６ ステップ
７ ステップエッジと垂直なＮ方向
８ ステップエッジと平行なＰ方向
９ 供給炭素
１０ ステップエッジ
1 carbon atom 2 Si substrate atom bonded to carbon (Si [110] atomic sequence)
3 Si substrate atom below Si atom bonded to carbon 4 Si substrate surface 5 Terrace 6 Step 7 N direction perpendicular to step edge 8 P direction parallel to step edge 9 Supply carbon 10 Step edge
Claims (1)
A silicon carbide crystal comprising a portion composed of silicon carbide crystal grains having uniform anisotropy, wherein the silicon carbide crystal grains are short in the direction of silicon carbide crystal 3C-SiC [110] and A silicon carbide thin film comprising crystal grains having long anisotropy in a vertical 3C-SiC [110] direction .
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