JP3736054B2

JP3736054B2 - Plasma processing equipment

Info

Publication number: JP3736054B2
Application number: JP18945297A
Authority: JP
Inventors: 仁田村; 成一渡辺; 宗雄古瀬; 誠浩角屋; 浩康助迫
Original assignee: Hitachi Ltd
Current assignee: Hitachi Ltd
Priority date: 1997-07-15
Filing date: 1997-07-15
Publication date: 2006-01-18
Anticipated expiration: 2017-07-15
Also published as: JPH1140394A

Description

【０００１】
【発明の属する技術分野】
半導体集積回路等の製造にあたり、膜の形成、加工等にプラズマ処理装置が用いられる。本発明は安定なプラズマを均一に生成することにより高品位なプラズマ処理を可能とするプラズマ処理装置を提供することに寄与する。
【０００２】
【従来の技術】
通常のプラズマ処理装置では処理室に処理に適したガスを所定の流量供給し、そのガスを排気する速度を調整して処理室を処理に適した圧力に制御することが行われる。さらに処理室に電磁波を供給してプラズマを発生させ、プラズマ処理を行う。プラズマは処理室内の電磁界分布に対応した分布で発生する。プラズマ中の電磁界分布は電磁波の供給方法、プラズマの密度、圧力などのプラズマ特性、処理室の形状等により決まる。従来のプラズマ処理装置ではプラズマ中の電磁界分布に関して十分考慮されておらず、電磁波電力の有効利用、プラズマ分布の制御などが必ずしも適切に行われていない問題があった。
【０００３】
【発明が解決しようとする課題】
前記従来技術によると処理室に投入した電磁波の電力が必ずしもプラズマの発生に有効に利用されていない問題があった。プラズマ中でとりやすい電磁界分布と投入する電磁波の電磁界分布が必ずしも対応しないため安定したプラズマの生成が行われないという問題があった。
【０００４】
【課題を解決するための手段】
上記課題は、その内側が排気される処理室と、この処理室内に配置され被処理基板が載置される電極と、この電極の上方の前記処理室の上部に配置され誘電体製の窓部材と、この窓部材の上方に配置されその上方から導入されたマイクロ波による放射状の表面電流が上面を流れる導電体製の部材であって前記マイクロ波を前記窓部材に導くための孔の複数が円周状に配置された部材と、前記処理室の周囲に配置されこの処理室内に静磁界を形成するための手段とを備えたプラズマ処理装置であって、前記マイクロ波のうち電界の方向が傾いて位相が異なる複数の波が重ね合わされて形成された右回りの円偏波が、前記孔の各々から前記窓部材へ放射され、この窓部材を介して前記処理室内に導入されるプラズマ処理装置により解決できる。
【０００５】
さらに、前記孔は複数の方形状を組み合わせた形状を備えたことにより解決できる。さらには、前記孔から、電界の方向が傾いて位相が異なる複数の波長の波が重ね合わされて放射されることにより解決できる。さらにまた、前記孔は、その内部に前記複数の波のうち一方の波とは異なる波長の波がその内側を通過して放射される誘電体製の部材を備えたことにより解決できる。
【０００６】
【発明の実施の形態】
本発明の第１の実施例を図１を用いて説明する。例えばマグネトロンなどのマイクロ波源１０１により発生した例えば周波数２．４５ＧＨｚのマイクロ波はアイソレー夕１０２、整合器１０３を介して同軸導波管変換器１０４に伝送される。同軸導波管変換器１０４によりマイクロ波は軸対称な同軸線路１０５の基本モードに変換され、整合室１０６を介してモード変換器１０７にもたらされる。整合室１０６は内部または外部導体の直径が同軸線路１０５と異なるサイズの同軸線路で長さが１／４波長の線路であり、モード変換器１０７と同軸線路１０５の接続部でインピーダンス不整合により発生する電力の反射を防止している。またモード変換器１０７は投入されたマイクロ波の電磁界を同軸線路の基本モードから以下に説明する部材１０９の励振に適した分布に変換する作用を持つ。
【０００７】
モード変換器１０７の下部には結合孔１０８を有する部材１０９があり、結合孔１０８、マイクロ波導入窓１１０を介して処理室１１１にマイクロ波が導入される。部材１０９はアルミニウム、銅などの導電率の高い金属でできている。マイクロ波導入窓はマイクロ波に対する損失が小さく、プラズマ処理に悪影響を与えにくい誘電体として例えば石英、アルミナセラミックなどでできている。処理室１１１には図示しないガス導入系および排気系が接続され、処理室をプラズマ処理に適した圧力、ガス雰囲気に保持することができる。処理室１１１の周囲には静磁界の発生装置１１２が設置され、処理室１１１内に電子サイクロトロン共鳴現象を発生させる程度の静磁界を発生させることができる。投入するマイクロ波の周波数が例えば２．４５ＧＨｚの場合、電子サイクロトロン共鳴は０．０８７５テスラで起きることが知られており、マイクロ波電力はプラズマに強く吸収され、低い圧力でも高密度のプラズマを容易に発生させることができる。また処理室内の静磁界分布を調整することで、処理室内のプラズマ分布等を制御することができる。静磁界の発生装置１１２として例えば電磁石、永久磁石などを用いることができる。
【０００８】
処理室１１１内には被処理基板１１３を設置するための電極１１４が設けられている。電極１１４には高周波電源１１５が整合器１１６を介して接続され、被処理基板１１３に例えば１３．５６ＭＨｚなどの周波数の高周波を加えることができる。
【０００９】
図２を用いて結合孔１０８を有する部材１０９の構造を示す。同軸状のモード変換器１０７により部材１０９の表面にはマイクロ波表面電流２０１が放射状に流れる。これに対し結合孔１０８は互いに直交する２つの長方形状の穴２０２および２０３からなっている。長方形状の穴２０２および２０３はそれぞれマイクロ波表面電流２０１に対し互いに逆方向に４５°傾斜しており、さらにこれらはある円周状に配置されている。また穴２０２には誘電体２０４が装荷されている。
【００１０】
一般に導電率の高い物質で囲まれた長方形状の穴は方形導波管として動作させることができ、長辺の長さが半波長以上の場合に穴を通してマイクロ波を伝送することができる。長方形状の穴２０２、２０３は方形導波管として動作するよう、長辺の長さがマイクロ波の波長の半波長以上の長さになっている。部材１０９の厚さ（穴２０２、２０３の深さ）は穴２０２を通ったマイクロ波と穴２０３を通ったマイクロ波で位相がおよそ９０度異なる厚さに設定されている。一般に誘電体中で電磁波の波長は真空または空気中の電磁波の波長に比べ短くなる。方形導波管の最低次のモードであるＴＥ１０モードの管内波長は式（１）の様にあらわされることが知られている。
【００１１】
【数１】

【００１２】
ただし
λ_g ：ＴＥ１０モードの管内波長
λ_o ：真空中の波長
ε_r ：導波管内の比誘電率
ａ：方形導波管の長辺の長さ
例えば導波管長辺の長さが６５ｍｍで内部に石英（比誘電率３．７８とする）を入れた方形導波管の管内波長は７１．９ｍｍとなる。また空気（比誘電率１．０とする。）が入った同じサイズの方形導波管の管内波長は３６２ｍｍとなる。従って両者の位相差が９０度になる導波管の長さは２２．４ｍｍとなる。実際には部材１０９の厚さは管内波長に比べて短いこと、穴２０２、２０３を組み合わせた十字形状の穴は厳密には式（１）を満たさないこと等から部材１０９の厚さの最適値は前記計算値を必ずしも満足しない場合がある。
【００１３】
長方形状の穴２０２と２０３は方形導波管として動作しているため、穴２０２、２０３内部でのマイクロ波電界の方向は図２に示すようにマイクロ波表面電流２０１に対し互いに逆方向に４５°傾いたマイクロ波電界２０５のようになる。前述のように部材１０９の厚さは穴２０２と２０３を通過するマイクロ波の位相差が９０度となるように設定されており、その両者のマイクロ波の電界は互いに９０度の角度をなすため、部材１０９とマイクロ波導入窓１１０の接続面では両者の合成により円偏波が形成される。図２の例では８組の穴２０２、２０３が設けられており、これらが同位相で励振されるため、前記円偏波がそれぞれの組から同じ位相で放射される。
【００１４】
磁化プラズマは静磁界の方向に対して右回りの円偏波（以下Ｒ波）と左回りの円偏波（以下Ｌ波）で異なる伝搬特性を示すことが知られている。Ｒ波は電子サイクロトロン共鳴を起こし、プラズマに強く吸収されるのに対し、Ｌ波は電子サイクロトロン共鳴を起こさないためあまり強く吸収されず、プラズマ端面で反射される割合が大きい。部材１０９によりＲ波を発生させることでマイクロ波電力を効率良くプラズマに吸収させることができる。そのため低出力のマイクロ波源を用いても高密度のプラズマを容易に発生させることができる。またプラズマに対するマイクロ波の吸収がよくなるため、マイクロ波立体回路部の余計な加熱が少なく、安定してプラズマを発生させることができる。
【００１５】
図３に部材１０９として使用可能な他の構造を示す。式（１）によれば方形導波管の管内波長は導波管の長辺の長さにより変ることがわかる。そこで誘電体を装荷した導波管にかわり長辺の長さの異なる導波管を用いることで同様の効果を持たせることができる。長辺の長さの異なる２つの長方形状の穴を互いに９０度傾けて組み合わせ、十字状の穴３０１を形成する。十字状の穴３０１は２つの方形導波管を組み合わせた構造と考えることができ、それぞれの導波管の管内波長は式（１）に従って求めることができる。例えば長辺の長さ６５ｍｍと８０ｍｍの２つの長方形を９０度傾けて組み合わせた場合、それぞれの管内波長は３６２ｍｍおよび１９０ｍｍとなるので位相差を９０度とするには導波管の長さ（部材１０９の高さ）を１００ｍｍとすればよい。この場合も図２に示した場合と同様、最適値は前記計算値を必ずしも満足しない場合がある。
【００１６】
図４に部材１０９として使用可能な他の構造を示す。誘電体板４０２を傾けて円形の穴４０１内に装荷した構造となっている。誘電体中を進む電磁波の波長は真空中と比べて短くなる。従って誘電体板４０２と平行な電界成分を持つ電磁波は誘電体板４０２と垂直な成分を持つ電磁波とで波長が異なり、この両者が重なりあって円偏波を発生させることができる。
【００１７】
磁化プラズマに吸収されやすい円偏波を発生させるには電界の方向が傾いた複数の波を位相をずらして重ねあわせればよい。前述の例では電界の傾きおよび位相差が９０度である２つの波を重ねあわせる例を示したが、位相差、電界の傾きは９０度に限定されるものではなく他の角度であってもよい。また重ねあわせる波の数は２つに限定されるものではなく更に多くてもよい。
【００１８】
【発明の効果】
本発明によれば、プラズマ中でとりやすい電磁界分布と投入する電磁波の電磁界分布を対応させることができるのでプラズマ発生に必要な電力を低減するとともに安定してプラズマを発生させることができる効果がある。
【図面の簡単な説明】
【図１】本発明に係わるマイクロ波プラズマ処理装置を説明する図面。
【図２】結合孔を有する部材１０９の構造の第一例を説明する図面。
【図３】結合孔を有する部材１０９の構造の第二例を説明する図面。
【図４】結合孔を有する部材１０９の構造の第三例を説明する図面。
【符号の説明】
１０１…マイクロ波源、１０２…アイソレー夕、１０３…整合器、１０４…同軸導波管変換器、１０５…同軸線路、１０６…整合室、１０７…モード変換器、１０８…結合孔、１０９…部材、１１０…マイクロ波導入窓、１１１…処理室、１１２…静磁界の発生装置、１１３…被処理基板、１１４…電極、１１５…高周波電源、１１６…整合器、２０１…マイクロ波表面電流、２０２…長方形状の穴、２０３…長方形状の穴、２０４…誘電体、２０５…マイクロ波電界、３０１…十字状の穴、４０１…円形の穴、４０２…誘電体板。[0001]
BACKGROUND OF THE INVENTION
In manufacturing a semiconductor integrated circuit or the like, a plasma processing apparatus is used for forming or processing a film. The present invention contributes to providing a plasma processing apparatus that enables high-quality plasma processing by uniformly generating stable plasma.
[0002]
[Prior art]
In a normal plasma processing apparatus, a gas suitable for processing is supplied to a processing chamber at a predetermined flow rate, and the processing chamber is controlled to a pressure suitable for processing by adjusting the speed of exhausting the gas. Further, an electromagnetic wave is supplied to the processing chamber to generate plasma and perform plasma processing. Plasma is generated in a distribution corresponding to the electromagnetic field distribution in the processing chamber. The electromagnetic field distribution in the plasma is determined by the electromagnetic wave supply method, plasma characteristics such as plasma density and pressure, the shape of the processing chamber, and the like. In the conventional plasma processing apparatus, the electromagnetic field distribution in the plasma is not sufficiently considered, and there is a problem that the electromagnetic wave power is not effectively used and the plasma distribution is not properly controlled.
[0003]
[Problems to be solved by the invention]
According to the prior art, there is a problem that the power of the electromagnetic wave input into the processing chamber is not always effectively used for generating plasma. There is a problem that stable plasma generation cannot be performed because the electromagnetic field distribution that is easy to take in the plasma does not necessarily correspond to the electromagnetic field distribution of the input electromagnetic wave.
[0004]
[Means for Solving the Problems]
The above-described problems include a processing chamber whose inside is evacuated, an electrode disposed in the processing chamber and on which a substrate to be processed is placed, and a dielectric window member disposed above the processing chamber above the electrode. And a member made of a conductor that is disposed above the window member and has a radial surface current due to the microwave introduced from above the window member, and a plurality of holes for guiding the microwave to the window member. A plasma processing apparatus comprising a circumferentially arranged member and means for forming a static magnetic field in the processing chamber disposed around the processing chamber, wherein an electric field direction of the microwave is A clockwise circularly polarized wave formed by superposing a plurality of waves that are inclined and different in phase is radiated from each of the holes to the window member and is introduced into the processing chamber through the window member. It can be solved by the device.
[0005]
Furthermore, the hole can be solved by providing a shape obtained by combining a plurality of square shapes. Furthermore, the problem can be solved by overlapping and radiating waves of a plurality of wavelengths whose phases are different from each other and whose phase is inclined from the hole . Furthermore, the hole can be solved by providing a dielectric member in which a wave having a wavelength different from one of the plurality of waves is radiated through the inside thereof.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
A first embodiment of the present invention will be described with reference to FIG. For example, a microwave having a frequency of 2.45 GHz generated by a microwave source 101 such as a magnetron is transmitted to the coaxial waveguide converter 104 via the isolator 102 and the matching unit 103. The microwave is converted by the coaxial waveguide converter 104 into the fundamental mode of the axially symmetric coaxial line 105, and is sent to the mode converter 107 through the matching chamber 106. The matching chamber 106 is a coaxial line whose inner or outer conductor diameter is different from that of the coaxial line 105 and has a length of ¼ wavelength, and is generated due to impedance mismatch at the connection between the mode converter 107 and the coaxial line 105. To prevent the reflection of power. The mode converter 107 has an effect of converting the input microwave electromagnetic field into a distribution suitable for excitation of the member 109 described below from the basic mode of the coaxial line.
[0007]
A member 109 having a coupling hole 108 is provided below the mode converter 107, and the microwave is introduced into the processing chamber 111 through the coupling hole 108 and the microwave introduction window 110. The member 109 is made of a metal having high conductivity such as aluminum or copper. The microwave introduction window is made of, for example, quartz, alumina ceramic or the like as a dielectric that has a small loss with respect to the microwave and does not adversely affect the plasma processing. A gas introduction system and an exhaust system (not shown) are connected to the processing chamber 111, and the processing chamber can be maintained at a pressure and gas atmosphere suitable for plasma processing. A static magnetic field generator 112 is installed around the processing chamber 111, and can generate a static magnetic field to the extent that an electron cyclotron resonance phenomenon is generated in the processing chamber 111. For example, when the frequency of the input microwave is 2.45 GHz, it is known that electron cyclotron resonance occurs at 0.0875 Tesla, and the microwave power is strongly absorbed by the plasma, so that a high-density plasma can be easily obtained even at a low pressure. Can be generated. Further, by adjusting the static magnetic field distribution in the processing chamber, the plasma distribution and the like in the processing chamber can be controlled. As the static magnetic field generator 112, for example, an electromagnet, a permanent magnet, or the like can be used.
[0008]
An electrode 114 for installing a substrate to be processed 113 is provided in the processing chamber 111. A high frequency power source 115 is connected to the electrode 114 via a matching unit 116, and a high frequency with a frequency such as 13.56 MHz can be applied to the substrate 113 to be processed.
[0009]
The structure of the member 109 having the coupling hole 108 will be described with reference to FIG. The microwave surface current 201 flows radially on the surface of the member 109 by the coaxial mode converter 107. On the other hand, the coupling hole 108 includes two

rectangular holes

202 and 203 that are orthogonal to each other. The

rectangular holes

202 and 203 are inclined 45 ° in opposite directions with respect to the microwave surface current 201, respectively, and are arranged in a certain circumferential shape. A dielectric 204 is loaded in the hole 202.
[0010]
In general, a rectangular hole surrounded by a material having high conductivity can be operated as a rectangular waveguide, and microwaves can be transmitted through the hole when the length of the long side is a half wavelength or more. The

rectangular holes

202 and 203 have a longer side length equal to or longer than a half wavelength of the microwave so that the

rectangular holes

202 and 203 operate as a rectangular waveguide. The thickness of member 109 (depth of holes 202 and 203) is set to a thickness that is approximately 90 degrees different in phase between the microwave passing through hole 202 and the microwave passing through hole 203. In general, the wavelength of electromagnetic waves in a dielectric is shorter than the wavelength of electromagnetic waves in vacuum or air. It is known that the in-tube wavelength of the TE10 mode, which is the lowest order mode of the rectangular waveguide, is expressed as shown in Equation (1).
[0011]
[Expression 1]

[0012]
However, λ _g : In-tube wavelength of TE10 mode λ _o : Wavelength in vacuum ε _r : Relative permittivity in waveguide a: Length of long side of rectangular waveguide, for example, length of long side of waveguide is 65 mm and inside The in-tube wavelength of a rectangular waveguide in which quartz (with a relative dielectric constant of 3.78) is placed is 71.9 mm. In addition, the in-tube wavelength of a rectangular waveguide of the same size containing air (with a relative dielectric constant of 1.0) is 362 mm. Therefore, the length of the waveguide where the phase difference between them is 90 degrees is 22.4 mm. Actually, the thickness of the member 109 is shorter than the in-tube wavelength, and the cross-shaped hole combining the

holes

202 and 203 does not strictly satisfy the formula (1). May not necessarily satisfy the calculated value.
[0013]
Since the

rectangular holes

202 and 203 operate as rectangular waveguides, the direction of the microwave electric field inside the

holes

202 and 203 is 45 opposite to the microwave surface current 201 as shown in FIG. It becomes like a microwave electric field 205 inclined by °. As described above, the thickness of the member 109 is set so that the phase difference between the microwaves passing through the

holes

202 and 203 is 90 degrees, and the electric fields of both microwaves form an angle of 90 degrees with each other. At the connecting surface of the member 109 and the microwave introduction window 110, circular polarization is formed by combining the two. In the example of FIG. 2, eight sets of

holes

202 and 203 are provided, and these are excited in the same phase, so that the circularly polarized wave is radiated from each set in the same phase.
[0014]
Magnetized plasma is known to exhibit different propagation characteristics for clockwise circularly polarized waves (hereinafter R waves) and counterclockwise circularly polarized waves (hereinafter L waves) with respect to the direction of the static magnetic field. The R wave causes electron cyclotron resonance and is strongly absorbed by the plasma, whereas the L wave does not cause electron cyclotron resonance and is not so strongly absorbed and is reflected at the plasma end face. By generating the R wave by the member 109, the microwave power can be efficiently absorbed by the plasma. Therefore, high-density plasma can be easily generated even when a low-power microwave source is used. Moreover, since the absorption of the microwave with respect to plasma becomes good, there is little extra heating of a microwave solid circuit part, and it can generate a plasma stably.
[0015]
FIG. 3 shows another structure that can be used as the member 109. According to equation (1), it is understood that the in-tube wavelength of the rectangular waveguide varies depending on the length of the long side of the waveguide. Therefore, the same effect can be obtained by using a waveguide having a different long side instead of the waveguide loaded with a dielectric. Two rectangular holes having different long sides are tilted and combined with each other by 90 degrees to form a cross-shaped hole 301. The cross-shaped hole 301 can be considered as a structure in which two rectangular waveguides are combined, and the in-tube wavelength of each waveguide can be obtained according to the equation (1). For example, when two long rectangles with a length of 65 mm and 80 mm are combined with an inclination of 90 degrees, the in-tube wavelengths are 362 mm and 190 mm, respectively. 109 height) may be 100 mm. In this case, as in the case shown in FIG. 2, the optimum value may not always satisfy the calculated value.
[0016]
FIG. 4 shows another structure that can be used as the member 109. The dielectric plate 402 is tilted and loaded into the circular hole 401. The wavelength of the electromagnetic wave traveling in the dielectric is shorter than in vacuum. Therefore, the electromagnetic wave having an electric field component parallel to the dielectric plate 402 has a wavelength different from that of the electromagnetic wave having a component perpendicular to the dielectric plate 402, and the two can overlap to generate a circularly polarized wave.
[0017]
In order to generate a circularly polarized wave that is easily absorbed by the magnetized plasma, a plurality of waves whose directions of electric fields are inclined may be superposed with their phases shifted. In the above example, two waves having an electric field inclination and phase difference of 90 degrees are superimposed. However, the phase difference and electric field inclination are not limited to 90 degrees, and may be at other angles. Good. Further, the number of waves to be superimposed is not limited to two, and may be larger.
[0018]
【The invention's effect】
According to the present invention, an electromagnetic field distribution that can be easily obtained in plasma and an electromagnetic field distribution of an electromagnetic wave to be input can be made to correspond to each other, so that the power required for plasma generation can be reduced and plasma can be generated stably. There is.
[Brief description of the drawings]
FIG. 1 illustrates a microwave plasma processing apparatus according to the present invention.
FIG. 2 is a drawing for explaining a first example of the structure of a member 109 having a coupling hole.
FIG. 3 is a view for explaining a second example of the structure of a member 109 having a coupling hole.
FIG. 4 is a drawing for explaining a third example of the structure of the member 109 having a coupling hole.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 101 ... Microwave source, 102 ... Isolay, 103 ... Matching device, 104 ... Coaxial waveguide converter, 105 ... Coaxial line, 106 ... Matching chamber, 107 ... Mode converter, 108 ... Coupling hole, 109 ... Member, 110 DESCRIPTION OF SYMBOLS ... Microwave introduction window, 111 ... Processing chamber, 112 ... Static magnetic field generator, 113 ... Substrate to be processed, 114 ... Electrode, 115 ... High frequency power supply, 116 ... Matching device, 201 ... Microwave surface current, 202 ... Rectangular shape , 203 ... rectangular hole, 204 ... dielectric, 205 ... microwave electric field, 301 ... cross-shaped hole, 401 ... circular hole, 402 ... dielectric plate.

Claims

A processing chamber whose inside is evacuated, an electrode which is disposed in the processing chamber and on which a substrate to be processed is placed, a dielectric window member which is disposed above the processing chamber above the electrode, and the window disposed above the members plurality of circumferential holes for guiding the window member to said microwave radiating surface currents by the introduced microwave is a member made of a conductor through the top surface from above A plasma processing apparatus comprising: a member disposed in the processing chamber; and means for forming a static magnetic field in the processing chamber disposed around the processing chamber,
A clockwise circularly polarized wave formed by superimposing a plurality of waves having different phases in the direction of the electric field of the microwave is radiated from each of the holes to the window member, and through the window member. A plasma processing apparatus introduced into the processing chamber.

The plasma processing apparatus according to claim 1, wherein the hole has a shape obtained by combining a plurality of square shapes.

3. The plasma processing apparatus according to claim 1, wherein waves having a plurality of wavelengths with different directions and different phases are superimposed and emitted from the hole .

4. The plasma processing apparatus according to claim 3, wherein the hole is a dielectric member through which a wave having a wavelength different from one of the plurality of waves is radiated through the hole. A plasma processing apparatus comprising: