JP4886876B2 - Plasma processing apparatus and plasma processing method - Google Patents

Plasma processing apparatus and plasma processing method Download PDF

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JP4886876B2
JP4886876B2 JP2010123716A JP2010123716A JP4886876B2 JP 4886876 B2 JP4886876 B2 JP 4886876B2 JP 2010123716 A JP2010123716 A JP 2010123716A JP 2010123716 A JP2010123716 A JP 2010123716A JP 4886876 B2 JP4886876 B2 JP 4886876B2
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refrigerant
flow path
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temperature
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JP2010272873A (en
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匠 丹藤
賢悦 横川
勝 伊澤
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Hitachi High Tech Corp
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本発明は半導体製造工程においてウエハなどの試料に微細加工を施すプラズマ処理装置及びプラズマ処理方法にかかり、特に、半導体ウエハを保持固定する電極部の温度制御装置及び温度制御方法に関する。   The present invention relates to a plasma processing apparatus and a plasma processing method for performing microfabrication on a sample such as a wafer in a semiconductor manufacturing process, and more particularly to a temperature control apparatus and a temperature control method for an electrode unit for holding and fixing a semiconductor wafer.

半導体デバイスの微細化に伴い、試料のエッチング処理に求められる加工精度はますます厳しくなっている。プラズマ処理装置にてウエハ表面の微細パターンに高精度な加工を施すためには、エッチング中のウエハ表面の温度管理が重要である。しかし、ウエハの大面積化やエッチングレートの向上の要求から、プラズマ処理装置に印加される高周波電力は増加傾向にあり、特に絶縁膜のエッチングにおいてはキロワットオーダの大電力が印加され始めている。大電力の印加により、ウエハ表面へのイオンの衝撃エネルギが増加し、エッチング中におけるウエハの過度な温度上昇が問題となっている。また、形状精度の更なる向上の要求から、プロセス中においてウエハの温度を高速かつ精密に制御できる手段が求められている。   With the miniaturization of semiconductor devices, the processing accuracy required for the etching process of samples has become increasingly severe. In order to perform high-precision processing on a fine pattern on a wafer surface with a plasma processing apparatus, temperature control of the wafer surface during etching is important. However, high-frequency power applied to the plasma processing apparatus tends to increase due to demands for an increase in wafer area and an etching rate, and in particular, in the etching of insulating films, large power on the order of kilowatts has begun to be applied. The application of high power increases the impact energy of ions on the wafer surface, causing an excessive temperature rise of the wafer during etching. In addition, due to the demand for further improvement in shape accuracy, a means capable of controlling the temperature of the wafer at high speed and precisely during the process is required.

プラズマ処理装置内においてウエハの表面温度を制御するためには、ウエハの裏面と熱伝達媒体を介して接する静電吸着電極（以下、電極と記す）の表面温度を制御すればよい。従来の電極では内部に冷媒の流路を形成し、流路内に液体冷媒を流すことにより電極表面の温度を制御していた。液体冷媒は冷媒供給装置内の冷却装置又は加熱装置により目標温度に調節された後に電極流路内に供給されている。このような冷媒供給装置では液体冷媒を一度タンクに溜めて温度調節後に送り出す構造であり、また液体冷媒自体の熱容量が大きいため、ウエハの表面温度を一定に保つ際には有効である。しかし、温度レスポンスが悪く、高速温度制御が困難であり、また熱交換効率が低い。そのため、近年の大入熱化に伴い装置が大型化し、またエッチングの進行に応じてウエハ表面の温度を最適にコントロールすることが困難であった。   In order to control the surface temperature of the wafer in the plasma processing apparatus, the surface temperature of an electrostatic adsorption electrode (hereinafter referred to as an electrode) contacting the back surface of the wafer via a heat transfer medium may be controlled. In the conventional electrode, the flow path of the refrigerant is formed inside, and the temperature of the electrode surface is controlled by flowing the liquid refrigerant in the flow path. The liquid refrigerant is supplied to the electrode flow path after being adjusted to a target temperature by a cooling device or a heating device in the refrigerant supply device. Such a refrigerant supply device has a structure in which the liquid refrigerant is once stored in the tank and sent out after the temperature adjustment, and since the heat capacity of the liquid refrigerant itself is large, it is effective for keeping the wafer surface temperature constant. However, the temperature response is poor, high-speed temperature control is difficult, and the heat exchange efficiency is low. For this reason, the apparatus has become larger with the recent increase in heat input, and it has been difficult to optimally control the temperature of the wafer surface in accordance with the progress of etching.

このようなことから、冷媒循環系が冷媒を高圧化する圧縮機と、高圧化された冷媒を凝縮する凝縮器と、冷媒を膨張させる膨張弁を電極に設置し、電極の冷媒流路内にて冷媒を蒸発させて冷却を行う直接膨張式の冷媒供給装置（以下直膨式冷凍サイクル）が、例えば特許文献１により提案されている。直膨式冷凍サイクルでは冷媒の蒸発潜熱を利用するため冷却効率が高く、また冷媒の蒸発温度が圧力によって高速に制御可能である。上記より、電極への冷媒供給装置として直膨式を採用することによって、大入熱エッチング処理時における半導体ウエハの温度を、高効率かつ高速に制御することができる。   For this reason, the refrigerant circulation system has a compressor for increasing the pressure of the refrigerant, a condenser for condensing the increased pressure refrigerant, and an expansion valve for expanding the refrigerant. For example, Patent Document 1 proposes a direct expansion refrigerant supply device (hereinafter referred to as a direct expansion refrigeration cycle) that cools by evaporating the refrigerant. The direct expansion refrigeration cycle uses the latent heat of vaporization of the refrigerant, so that the cooling efficiency is high, and the evaporation temperature of the refrigerant can be controlled at high speed by the pressure. As described above, by adopting the direct expansion type as the coolant supply device to the electrodes, the temperature of the semiconductor wafer during the high heat input etching process can be controlled with high efficiency and high speed.

特開２００５−８９８６４号公報JP 2005-89864 A

直膨式冷凍サイクルは、冷媒が液体から気体に蒸発する際の潜熱を利用して冷却を行い、冷媒の蒸発温度は圧力によって制御可能である。電極の冷媒流路内において、冷媒の圧力が一定であれば蒸発温度も一定である。しかし、冷媒は流路内で熱を吸収して蒸発しながら流れているため、相変化に伴い熱伝達率が変化する。つまり、電極の面内温度均一性を考えて冷媒流路内において冷媒圧力を一定に保った場合でも、冷媒流路内で熱伝達率が不均一となり、電極の表面温度、ひいてはウエハの温度を面内均一に制御することは難しい。これにより、直膨式冷凍サイクルを電極の冷却機構として採用する際には、面内の温度分布均一制御が技術的な課題となっている。   In the direct expansion refrigeration cycle, cooling is performed using latent heat when the refrigerant evaporates from a liquid to a gas, and the evaporation temperature of the refrigerant can be controlled by pressure. In the refrigerant flow path of the electrode, if the refrigerant pressure is constant, the evaporation temperature is also constant. However, since the refrigerant flows while absorbing heat in the flow path and evaporating, the heat transfer coefficient changes with the phase change. In other words, even when the in-plane temperature uniformity of the electrode is taken into consideration, even when the refrigerant pressure is kept constant in the refrigerant flow path, the heat transfer coefficient becomes non-uniform in the refrigerant flow path, and the surface temperature of the electrode and thus the temperature of the wafer are reduced. It is difficult to control the surface uniformly. Accordingly, when the direct expansion refrigeration cycle is employed as an electrode cooling mechanism, in-plane temperature distribution uniform control is a technical issue.

上記問題に対して特許文献１では、ウエハを設置する電極面に熱拡散プレートを用いて、冷媒の熱伝達の不均一を熱拡散プレートで補正し、ウエハの面内温度を均一にする方法が提案されている。これにより、直膨式冷凍サイクルを電極の冷却機構として採用しても、ウエハの面内温度を高冷却効率、かつ面内均一に温度制御することができる。しかし、今後ウエハの温度を高速に制御する場合には、電極の低熱容量化が必要となる。冷媒の蒸発温度を高速に可変可能であっても、電極の熱容量が大きい場合にはウエハの温度制御速度が低下する。電極の低熱容量化には、構成部材の低質量化が必要となるが、熱拡散プレートを使用する場合には、熱拡散領域を確保するためにプレートに相応の厚みが必要となる。更に、近年の高ウエハバイアス印加による大入熱化により、面内の温度差が拡大し、熱拡散プレートに必要とされる厚みは増している。これにより、直膨式冷凍サイクルを用いて電極上のウエハの温度を高効率、高速かつ面内均一に制御するためには、電極構造について新たな検討が必要となった。   With respect to the above problem, Patent Document 1 discloses a method in which a heat diffusion plate is used on the electrode surface on which the wafer is placed, and the non-uniformity in heat transfer of the refrigerant is corrected with the heat diffusion plate to make the in-plane temperature of the wafer uniform. Proposed. As a result, even if the direct expansion type refrigeration cycle is employed as the electrode cooling mechanism, the in-plane temperature of the wafer can be controlled with high cooling efficiency and uniformly in the plane. However, if the temperature of the wafer is to be controlled at a high speed in the future, it is necessary to reduce the heat capacity of the electrodes. Even if the evaporation temperature of the refrigerant can be varied at a high speed, the temperature control speed of the wafer decreases when the heat capacity of the electrode is large. In order to reduce the heat capacity of the electrode, it is necessary to reduce the mass of the constituent members. However, when a heat diffusion plate is used, the plate needs to have a corresponding thickness in order to secure a heat diffusion region. Furthermore, due to the recent increase in heat input by applying a high wafer bias, the in-plane temperature difference has increased, and the thickness required for the thermal diffusion plate has increased. As a result, in order to control the temperature of the wafer on the electrode with high efficiency, high speed, and in-plane uniformity using a direct expansion type refrigeration cycle, a new examination of the electrode structure is required.

本発明の目的は、被加工試料の面内温度を高冷却効率、かつ面内均一に制御することができると共に、電極の低熱容量化を可能にするプラズマ処理装置及びプラズマ処理方法を提供することにある。   An object of the present invention is to provide a plasma processing apparatus and a plasma processing method capable of controlling the in-plane temperature of a sample to be processed with high cooling efficiency and uniform in-plane, and enabling the heat capacity of an electrode to be reduced. It is in.

本発明の他の目的は、電極の面内における冷媒の熱伝達率αの変化を抑制し、被加工試料の面内の温度を高効率、高速かつ均一に制御可能なプラズマ処理装置及びプラズマ処理方法を提供することにある。   Another object of the present invention is to suppress a change in the heat transfer coefficient α of the refrigerant in the surface of the electrode and to control the temperature in the surface of the sample to be processed with high efficiency, high speed and uniformly, and a plasma processing apparatus and plasma processing It is to provide a method.

本発明の他の目的は、電極の面内における冷媒の熱伝達率αを制御し、被加工試料の面内の温度分布を任意に制御できるようにしたプラズマ処理装置及びプラズマ処理方法を提供することにある。   Another object of the present invention is to provide a plasma processing apparatus and a plasma processing method which control the heat transfer coefficient α of the refrigerant in the surface of the electrode and can arbitrarily control the temperature distribution in the surface of the sample to be processed. There is.

上記課題を解決するために、本発明のプラズマ処理装置は、真空処理室内に導入された処理ガスをプラズマ化し、該プラズマにて試料台の試料載置面に載置された被処理基板の表面処理を行うプラズマ処理装置において、前記試料台でかつ前記試料載置面の下部に設けられた冷媒流路を有し、前記試料台の冷媒流路と圧縮機と凝縮器と膨張弁とがこの順に連結され前記試料台の冷媒流路が蒸発器として動作する冷凍サイクルを構成し、前記試料台の冷媒流路が、冷媒供給口と冷媒排出口との間に形成された、断面積が増大していく流路または減少していく流路あるいは増大した後減少していく流路のいずれかを有し、前記冷凍サイクルを構成する圧縮機の入口側と前記冷媒排出口との間に設置された気化器を有し、前記冷凍サイクルにおいて気液二相の状態にある前記冷媒の乾き度を前記冷媒流路の断面積が最大となる位置で冷媒の熱伝達率が最大値になるように調節すると共に、該冷媒を前記冷媒排出口から完全蒸発させずに排出し、前記気化器で蒸発させることを特徴とする。 In order to solve the above problems, a plasma processing apparatus of the present invention converts a processing gas introduced into a vacuum processing chamber into plasma, and the surface of the substrate to be processed placed on the sample placement surface of the sample stage with the plasma. In the plasma processing apparatus for performing the processing, the sample stage has a refrigerant channel provided at a lower portion of the sample mounting surface, and the refrigerant channel, the compressor, the condenser, and the expansion valve of the sample stage are provided with the refrigerant channel. The refrigerant flow path of the sample stage is connected in order to form a refrigeration cycle that operates as an evaporator, and the refrigerant flow path of the sample stage is formed between the refrigerant supply port and the refrigerant discharge port, and the cross-sectional area increases. A flow path that decreases, a flow path that decreases, or a flow path that decreases after increasing, and is installed between the inlet side of the compressor constituting the refrigeration cycle and the refrigerant discharge port by having a carburetor, in the refrigeration cycle With heat transfer coefficient of the refrigerant is adjusted to a maximum value at a position where the dryness of the refrigerant in the state of the liquid two-phase cross-sectional area of the refrigerant passage becomes maximum, the coolant from the coolant outlet port It discharges without completely evaporating, It evaporates with the said vaporizer, It is characterized by the above-mentioned.

本発明によれば、冷媒の相変化に伴う熱伝達率の変化に応じて、電極内の冷媒流路の断面積を変化させることで、冷媒の流速を制御し、流路内での熱伝達率の不均一を低減し、電極面内の温度を均一に保つことが可能となる。また、電極の冷媒流路内に流入する冷媒の乾き度、流量、圧力を制御することにより、電極上のウエハの面内温度分布を任意に制御することができる。   According to the present invention, the flow rate of the refrigerant is controlled by changing the cross-sectional area of the refrigerant flow path in the electrode in accordance with the change in the heat transfer coefficient accompanying the phase change of the refrigerant, and the heat transfer in the flow path. It is possible to reduce the non-uniformity of the rate and keep the temperature in the electrode surface uniform. Further, by controlling the dryness, flow rate, and pressure of the refrigerant flowing into the refrigerant flow path of the electrode, the in-plane temperature distribution of the wafer on the electrode can be arbitrarily controlled.

さらに、本発明により、高ウエハバイアス電力の印加による大入熱エッチング時のウエハの温度を、高効率、高速かつ面内均一に制御することが可能な電極用の温調ユニットを提供できる。   Furthermore, according to the present invention, it is possible to provide a temperature control unit for an electrode capable of controlling the temperature of a wafer during high heat input etching by applying a high wafer bias power with high efficiency, high speed and uniform in-plane.

本発明にかかるプラズマ処理装置の、全体的なシステム構成を示す概略図である。It is the schematic which shows the whole system configuration | structure of the plasma processing apparatus concerning this invention. 本発明にかかる試料台内の流路構成の、第一の実施例を示す概略図である。It is the schematic which shows the 1st Example of the flow-path structure in the sample stand concerning this invention. 本発明に採用されている冷凍サイクルにおける、冷媒の一般的な特性を示すグラフである。It is a graph which shows the general characteristic of the refrigerant | coolant in the refrigerating cycle employ | adopted for this invention. 冷媒の蒸発温度の一般的な特性を示す説明図である。It is explanatory drawing which shows the general characteristic of the evaporation temperature of a refrigerant | coolant. 冷媒の熱伝達率の一般的な特性を示す説明図である。It is explanatory drawing which shows the general characteristic of the heat transfer rate of a refrigerant | coolant. 本発明の第一の実施例における、冷媒の熱伝達率の特性を示す説明図である。It is explanatory drawing which shows the characteristic of the heat transfer coefficient of a refrigerant | coolant in the 1st Example of this invention. 本発明にかかる試料台内の流路構成の、第二例を示す概略図である。It is the schematic which shows the 2nd example of the flow-path structure in the sample stand concerning this invention. 本発明にかかる試料台内の流路構成の、第三例を示す概略図である。It is the schematic which shows the 3rd example of the flow-path structure in the sample stand concerning this invention. 本発明にかかる試料台内の流路構成の、第四例を示す概略図である。It is the schematic which shows the 4th example of the flow-path structure in the sample stand concerning this invention. 本発明にかかる試料台内の流路構成の、第五例を示す概略図である。It is the schematic which shows the 5th example of the flow-path structure in the sample stand concerning this invention. 本発明にかかる面内温度制御の他の例を示す説明図である。It is explanatory drawing which shows the other example of in-plane temperature control concerning this invention. 本発明にかかるプラズマ処理装置の他の実施例を示す概略図である。It is the schematic which shows the other Example of the plasma processing apparatus concerning this invention. 本発明にかかる試料台内の流路構成の、第六例を示す概略図である。It is the schematic which shows the 6th example of the flow-path structure in the sample stand concerning this invention. 本発明にかかる試料台内の流路構成の、第七例を示す概略図である。It is the schematic which shows the 7th example of the flow-path structure in the sample stand concerning this invention.

本発明を実施するための最良の形態を以下に示す。   The best mode for carrying out the present invention will be described below.

本発明の第一の実施例を図１乃至図４で説明する。
図１は、本発明の一実施例になるプラズマ処理装置の全体的なシステム構成を示す模式図である。プラズマ処理装置は、真空容器内に配置された処理室１００を有し、この処理室１００の内部には静電吸着電極を備えた試料台１が配置されている。また、処理室１００にはその内部を排気して減圧するための真空ポンプ等の真空排気装置２０が接続されている。処理室１００の上部には電極プレート１５が設けられており、これにアンテナ電源２１が接続されている。なお、処理室１００の上部には、処理ガスを供給するシャワープレート（図示略）などのガス導入手段も設けられている。 A first embodiment of the present invention will be described with reference to FIGS.
FIG. 1 is a schematic diagram showing an overall system configuration of a plasma processing apparatus according to an embodiment of the present invention. The plasma processing apparatus has a processing chamber 100 disposed in a vacuum vessel, and a sample stage 1 having an electrostatic adsorption electrode is disposed inside the processing chamber 100. Further, the processing chamber 100 is connected with a vacuum exhaust device 20 such as a vacuum pump for exhausting the inside thereof and reducing the pressure. An electrode plate 15 is provided above the processing chamber 100, and an antenna power source 21 is connected to the electrode plate 15. A gas introducing means such as a shower plate (not shown) for supplying a processing gas is also provided at the upper part of the processing chamber 100.

試料台１は、基材部１Ａと下部電極（静電吸着電極）１Ｂとを備えている。基材部１Ａには、内部を冷媒が循環する冷媒流路２が設けられている。下部電極１Ｂは静電吸着用の誘電体膜が設けられると共に、この電極の上表面部は被処理基板(ウエハ)Ｗを載置するための試料載置面として構成されている。試料台１の試料載置面上でかつウエハの裏面側の微小隙間には、伝熱ガス供給系１１から熱伝達用のＨｅガス１２が供給される。試料台１には、バイアス電源２２や静電吸着用の直流電源（図示略）が続されている。   The sample stage 1 includes a base part 1A and a lower electrode (electrostatic adsorption electrode) 1B. The base material portion 1A is provided with a refrigerant flow path 2 through which the refrigerant circulates. The lower electrode 1B is provided with a dielectric film for electrostatic adsorption, and the upper surface portion of this electrode is configured as a sample mounting surface for mounting a substrate (wafer) W to be processed. A heat transfer He gas 12 is supplied from a heat transfer gas supply system 11 to a minute gap on the sample mounting surface of the sample stage 1 and on the back side of the wafer. The sample table 1 is connected to a bias power source 22 and a DC power source (not shown) for electrostatic adsorption.

試料台１の基材部１Ａに設けられた冷媒流路２には、冷媒供給口３及び冷媒排出口４が接続されている。冷媒流路２は、圧縮機７、凝縮器８、膨張弁９、冷媒蒸発器１０と共に、冷凍サイクルを構成している。試料台１に設けられた冷媒流路２は、直膨式冷凍サイクルの蒸発器を構成するものである。すなわち、試料台１内の冷媒の流路２内において冷媒が蒸発する際の潜熱(気化熱)により、冷媒と接している試料台１の冷却が行われる。冷媒には、例えばR４１０（ハイドロフルオロカーボン）を用いる。   A refrigerant supply port 3 and a refrigerant discharge port 4 are connected to the refrigerant flow path 2 provided in the base portion 1A of the sample stage 1. The refrigerant flow path 2 constitutes a refrigeration cycle together with the compressor 7, the condenser 8, the expansion valve 9, and the refrigerant evaporator 10. The refrigerant flow path 2 provided in the sample stage 1 constitutes an evaporator of a direct expansion type refrigeration cycle. That is, the sample stage 1 in contact with the refrigerant is cooled by latent heat (heat of vaporization) when the refrigerant evaporates in the refrigerant flow path 2 in the sample stage 1. For example, R410 (hydrofluorocarbon) is used as the refrigerant.

６は、試料載置面に近接して複数個所に設けられた温度センサである、１０１は温度制御システムであり、温度センサ６からの出力を受けて圧縮機７や膨張弁９を制御することにより、試料載置面上の被処理基板(ウエハ)Ｗの温度が目標値になるように制御する。ウエハＷの温度は、プラズマエッチ等の処理条件、すなわちプラズマからウエハＷのへの入熱状況により変化する。そのため、温度センサ６で検出された温度に基づいて、冷媒流路２を流れる冷媒流量、冷媒圧力（冷媒蒸発温度）などを制御することで、ウエハＷの温度が目標値に維持されるように制御する。   Reference numeral 6 denotes a temperature sensor provided at a plurality of locations in the vicinity of the sample mounting surface. Reference numeral 101 denotes a temperature control system which receives the output from the temperature sensor 6 and controls the compressor 7 and the expansion valve 9. Thus, the temperature of the substrate to be processed (wafer) W on the sample mounting surface is controlled to be a target value. The temperature of the wafer W varies depending on processing conditions such as plasma etching, that is, the heat input state from the plasma to the wafer W. Therefore, the temperature of the wafer W is maintained at the target value by controlling the flow rate of the refrigerant flowing through the refrigerant flow path 2, the refrigerant pressure (refrigerant evaporation temperature), and the like based on the temperature detected by the temperature sensor 6. Control.

本発明において、蒸発器を構成する冷媒流路２は、少なくとも３つの流路領域を有し、これらの流路領域のうちで中間部領域の断面積が他の流路領域よりも大きくなるように構成されている。これを図２で説明する。図２は、図１のＡ−Ａ断面を示すものである。   In the present invention, the refrigerant flow path 2 constituting the evaporator has at least three flow path areas, and among these flow path areas, the cross-sectional area of the intermediate area is larger than the other flow path areas. It is configured. This will be described with reference to FIG. FIG. 2 shows an AA cross section of FIG.

図２において、基材部１Ａの同じ高さの位置に、環状の冷媒流路２が形成されている。冷媒流路２は、冷媒供給口３に接続され左右２方向に分岐した第一流路２−１と、第一の連絡流路２Ｂ−１を経て左右２方向に分岐した第二流路２−２と、第二の連絡流路２Ｂ−２を経て左右２方向に分岐した第三流路２−３とを有し、第三流路２−３は冷媒排出口４に接続されている。   In FIG. 2, an annular coolant channel 2 is formed at the same height position of the base material portion 1 </ b> A. The refrigerant flow path 2 includes a first flow path 2-1 that is connected to the refrigerant supply port 3 and branches in the left and right directions, and a second flow path 2 that branches in the left and right directions through the first connection flow path 2B-1. 2 and a third flow path 2-3 branched in two left and right directions through the second communication flow path 2B-2, and the third flow path 2-3 is connected to the refrigerant discharge port 4.

冷媒は、液体状態にて冷媒供給口３から冷媒流路２内に流入し、蒸発潜熱にて試料台１を冷却し、気体状態にて冷媒排出口４から流出する。冷媒の熱伝達率αは冷媒供給口３から冷媒排出口４に向けて大きく変化することから、冷媒の熱伝達率αを冷媒流路２内で一定にするために、冷媒流路２の断面積は第一流路２−１から第二流路２−２に向けて増加する構造とした。   The refrigerant flows into the refrigerant flow path 2 from the refrigerant supply port 3 in a liquid state, cools the sample stage 1 with latent heat of vaporization, and flows out from the refrigerant discharge port 4 in a gas state. Since the heat transfer coefficient α of the refrigerant changes greatly from the refrigerant supply port 3 toward the refrigerant discharge port 4, in order to make the heat transfer coefficient α of the refrigerant constant in the refrigerant flow channel 2, the interruption of the refrigerant flow channel 2 The area increased from the first flow path 2-1 toward the second flow path 2-2.

これにより、冷媒の熱伝達率が上昇する乾き度領域において冷媒の流速を下げることで、冷媒の熱伝達率の上昇を抑制した。また、第二流路２−２から第三流路２−３に向けては、冷媒流路２の断面積を減少することで、冷媒の熱伝達率の低下を抑制した。   Accordingly, the increase in the heat transfer coefficient of the refrigerant is suppressed by reducing the flow rate of the refrigerant in the dryness region where the heat transfer coefficient of the refrigerant increases. Moreover, the reduction | decrease of the heat transfer rate of a refrigerant | coolant was suppressed by reducing the cross-sectional area of the refrigerant | coolant flow path 2 toward the 3rd flow path 2-3 from the 2nd flow path 2-2.

ここで、本発明の特徴である冷媒流路の断面積と冷媒乾き度（Ｘ）及び熱伝達率（α）の関係について、図３（Ａ，Ｂ）、図４（Ａ，Ｂ）を用いて説明する。   Here, with respect to the relationship between the cross-sectional area of the refrigerant flow path, the refrigerant dryness (X), and the heat transfer coefficient (α), which is a feature of the present invention, FIG. 3 (A, B) and FIG. 4 (A, B) are used. I will explain.

図３Ａは、本実施例に採用されている冷凍サイクルにおける冷媒の一般的な特性を示すグラフである。本実施例では、試料台１内の冷媒流路２内において冷媒が蒸発する際の潜熱(気化熱)により冷媒と接している試料台１の冷却が行われる構成である。この冷媒の熱交換(蒸発)が生じている流路２内では冷媒が気液二相の状態であり（乾き度Ｘ＝０〜１）、この状態で冷媒の圧力Ｐが一定である限り冷媒の蒸発温度（以下、温度）は理論的に一定である。一方、図３Ｂに示すように、冷媒の温度ＴEは基本的に冷媒の圧力Ｐが増大するにつれて大きくなる。   FIG. 3A is a graph showing general characteristics of the refrigerant in the refrigeration cycle employed in this example. In the present embodiment, the sample stage 1 in contact with the refrigerant is cooled by latent heat (heat of vaporization) when the refrigerant evaporates in the refrigerant flow path 2 in the sample stage 1. In the flow path 2 where heat exchange (evaporation) of the refrigerant occurs, the refrigerant is in a gas-liquid two-phase state (dryness X = 0 to 1), and as long as the refrigerant pressure P is constant in this state, the refrigerant The evaporation temperature (hereinafter referred to as temperature) is theoretically constant. On the other hand, as shown in FIG. 3B, the temperature TE of the refrigerant basically increases as the pressure P of the refrigerant increases.

そこで本発明では、冷媒の圧力Ｐや圧縮機７の回転数などを制御して冷媒の流量Ｑを調節する通常の温度調節機構に加えて、冷媒流路２の入口３から出口４までの間の冷媒の乾き度を制御することで、試料載置面内を所定の温度に制御するようにしたものである。   Therefore, in the present invention, in addition to the normal temperature adjustment mechanism that adjusts the refrigerant flow rate Q by controlling the refrigerant pressure P, the rotational speed of the compressor 7, etc., the interval from the inlet 3 to the outlet 4 of the refrigerant flow path 2 is as follows. By controlling the dryness of the refrigerant, the inside of the sample mounting surface is controlled to a predetermined temperature.

図４Ａに、直膨式冷凍サイクルの冷媒熱伝達率の特性を示す。直膨式冷凍サイクルは、冷媒が液体から気体に蒸発する際の潜熱を利用して冷却を行い、冷媒の蒸発温度は圧力によって制御可能である。   FIG. 4A shows the characteristics of the refrigerant heat transfer coefficient of the direct expansion refrigeration cycle. In the direct expansion refrigeration cycle, cooling is performed using latent heat when the refrigerant evaporates from a liquid to a gas, and the evaporation temperature of the refrigerant can be controlled by pressure.

図３Ｂで説明したように、冷媒は、液体と気体の割合（乾き度Ｘ）が変化しても、圧力Ｐが一定であれば、蒸発温度ＴEは変化しない。しかし、冷媒の蒸発が進行して乾き度が変化すると、図４Ａに示すように、熱伝達率αが変化してしまう。図４Ａの破線で示した「流路断面積一定」のグラフは、従来の一般な流路構成、すなわち、冷媒流路２の入口３から出口４までの間の流路断面積が一定の場合における、乾き度Ｘと熱伝達率αの関係を示したものである。直膨式冷凍サイクルでは、液体から気体に相変化する過程において、冷媒の伝熱様式が強制対流蒸発、ドライアウトと変化する。冷媒の蒸発初期から強制対流蒸発が開始し、その後、乾き度Xの上昇に伴って熱伝達率αが上昇する。そして、冷媒の乾き度Ｘが一定に達すると、ドライアウト（液膜の消失）が発生して熱伝達率αは低下する。このように直膨式冷凍サイクルでは冷媒の乾き度Ｘによって冷媒の熱伝達率αが大きく変化する。そのため、直膨式冷凍サイクルをウエハ用の冷却機構として採用する際には、ウエハ面内の温度分布制御が技術的な課題となっている。   As described with reference to FIG. 3B, the refrigerant does not change the evaporation temperature TE if the pressure P is constant even if the ratio of liquid to gas (dryness X) changes. However, when the evaporation of the refrigerant proceeds and the dryness changes, the heat transfer coefficient α changes as shown in FIG. 4A. The graph of “constant flow path cross-sectional area” shown by a broken line in FIG. 4A shows a conventional general flow path configuration, that is, a flow path cross-sectional area from the inlet 3 to the outlet 4 of the refrigerant flow path 2 is constant. 3 shows the relationship between the dryness X and the heat transfer coefficient α. In the direct expansion refrigeration cycle, the heat transfer mode of the refrigerant changes between forced convection evaporation and dryout in the process of phase change from liquid to gas. Forced convection evaporation starts from the beginning of the evaporation of the refrigerant, and then the heat transfer coefficient α increases as the dryness X increases. When the dryness X of the refrigerant reaches a certain level, dryout (disappearance of the liquid film) occurs and the heat transfer coefficient α decreases. In this way, in the direct expansion refrigeration cycle, the heat transfer coefficient α of the refrigerant varies greatly depending on the dryness X of the refrigerant. Therefore, when the direct expansion refrigeration cycle is employed as a cooling mechanism for a wafer, temperature distribution control within the wafer surface is a technical issue.

例えば、２ｋW級の直膨式冷凍サイクルにて、冷媒にR４１０、冷媒流路に１/４インチ管（内径４.８ｍｍ、内壁の凹凸無）を用いて、冷媒流量を７．５m3/sとした場合、熱伝達率の最大値は約４２００W/m２K（乾き度約０.５時）に達し、蒸発の終了直前には約５００W/m２K（乾き度約０.９９時）まで低下する。このように、直膨式冷凍サイクルでは、冷媒の熱伝達率αが液相から気相にかけて約９倍も変化するため、これを考慮しなければウエハの温度を面内均一に温度制御することはできない。 For example, in a 2 kW class direct expansion refrigeration cycle, the refrigerant flow rate is 7.5 m 3 / s using R410 as the refrigerant and a 1/4 inch tube (inner diameter 4.8 mm, no irregularities on the inner wall) as the refrigerant flow path. The maximum value of the heat transfer coefficient reaches about 4200 W / m 2 K (dryness of about 0.5 hour), and about 500 W / m 2 K (dryness of about 0.99 hour) immediately before the end of evaporation. To fall. As described above, in the direct expansion refrigeration cycle, the heat transfer coefficient α of the refrigerant changes by about 9 times from the liquid phase to the gas phase. Therefore, if this is not taken into account, the temperature of the wafer is uniformly controlled in the surface. I can't.

上記のとおり、本発明では冷媒の相変化に伴う熱伝達率αの変化に応じて、基材部１Ａに設けられた冷媒流路２の入口３から出口４までの間における流路断面積を、中間部領域の断面積が前後の他の流路領域よりも大きくなるように変化させている。   As described above, in the present invention, the flow path cross-sectional area between the inlet 3 and the outlet 4 of the refrigerant flow path 2 provided in the base 1A is changed according to the change in the heat transfer coefficient α accompanying the phase change of the refrigerant. The cross-sectional area of the intermediate area is changed so as to be larger than the other flow path areas before and after.

このように、本発明では、試料台１における冷媒の熱伝達率αが試料載置面に対応する面内において所望の熱伝達率になるように、冷媒の乾き度と熱伝達率αの関係を与える特性に基づいて、冷媒流路２の入口３から出口４までの間における冷媒の乾き度に応じて、流路断面積を変更することが特徴である。すなわち、図４Ａに示す流路断面積が一定の一般的な特性において冷媒の熱伝達率αの大きい所（乾き度Ｘ＝０．５付近）では、流路断面積を大きくして冷媒の流速を低下させることで冷媒の熱伝達率αを下げる。逆に、冷媒の乾き度の小さい所（乾き度Ｘ＝０付近）や大きい所（乾き度Ｘ＝１付近）では、流路断面積を小さくして冷媒の流速を増大させることで冷媒の熱伝達率αを上げる。このようにして、試料台１の試料載置面に対応する全面内における、換言すると冷媒流路２の入口３から出口４までの間における熱伝達率αの特性をフラットなものにできる。   Thus, in the present invention, the relationship between the dryness of the refrigerant and the heat transfer coefficient α so that the heat transfer coefficient α of the refrigerant in the sample stage 1 becomes a desired heat transfer coefficient in the plane corresponding to the sample mounting surface. Is characterized in that the cross-sectional area of the flow path is changed in accordance with the dryness of the refrigerant between the inlet 3 and the outlet 4 of the refrigerant flow path 2 based on the characteristic that gives That is, in a general characteristic where the flow path cross-sectional area shown in FIG. 4A is constant, where the heat transfer coefficient α of the refrigerant is large (in the vicinity of dryness X = 0.5), the flow cross-sectional area is increased to increase the flow velocity of the refrigerant. Is reduced to reduce the heat transfer coefficient α of the refrigerant. On the other hand, in places where the dryness of the refrigerant is small (around dryness X = 0) or large (in the vicinity of dryness X = 1), the flow rate of the refrigerant is increased by reducing the cross-sectional area of the flow path, thereby increasing the heat of the refrigerant. Increase transmission rate α. In this way, the characteristic of the heat transfer coefficient α in the entire surface corresponding to the sample placement surface of the sample stage 1, in other words, from the inlet 3 to the outlet 4 of the refrigerant flow path 2 can be made flat.

このような観点で、冷媒流路の断面積を、冷媒の熱伝達率αが最大となる位置で冷媒流路２の断面積が最大となるように連続的に変化させた理想的な状態（＝「流路断面積最適化」）では、図４Ｂに実線で示すように、冷媒の乾き度Ｘの大小に拘わらず、冷媒の熱伝達率αを一定にすることができる。   From such a viewpoint, an ideal state in which the cross-sectional area of the refrigerant flow path is continuously changed so that the cross-sectional area of the refrigerant flow path 2 is maximized at a position where the heat transfer coefficient α of the refrigerant is maximized ( = “Channel cross-sectional area optimization”), as indicated by a solid line in FIG. 4B, the heat transfer coefficient α of the refrigerant can be made constant regardless of the dryness X of the refrigerant.

流路溝の加工の容易性を考慮して、冷媒流路２の入口３から出口４までの間の流路領域の中間部領域の断面積が他の流路領域よりも大きくなるように、段階的に変化させることでも、冷媒の乾き度の如何に関わらず流路内における冷媒の熱伝達率をフラットな特性に近いものとすることができる。   In consideration of the ease of processing of the flow channel, the cross-sectional area of the intermediate region of the flow channel region from the inlet 3 to the outlet 4 of the refrigerant flow channel 2 is larger than the other flow channel regions, By changing in stages, the heat transfer coefficient of the refrigerant in the flow path can be close to a flat characteristic regardless of the dryness of the refrigerant.

例えば、図２の実施例に示したように、冷媒流路の断面積を３段階に変化させた場合、冷媒の熱伝達率αは、図４Ｂに破線で示すように冷媒の乾き度Ｘの大小に応じて変化するが、断面積一定の場合に比べるとその変化量は半分以下となる。   For example, as shown in the embodiment of FIG. 2, when the cross-sectional area of the refrigerant flow path is changed in three stages, the heat transfer coefficient α of the refrigerant is equal to the dryness X of the refrigerant as shown by the broken line in FIG. 4B. Although it changes according to the size, the amount of change is less than half compared to the case where the cross-sectional area is constant.

このように、基材部１Ａに設けられた冷媒流路の断面積を出入り口部付近よりも途中で大きくなるように構成することで、冷媒流路２内で冷媒の熱伝達率の均一化を図ることができる。   In this way, the cross-sectional area of the refrigerant flow path provided in the base portion 1A is configured to be larger in the middle than the vicinity of the entrance / exit part, thereby making the heat transfer coefficient of the refrigerant uniform in the refrigerant flow path 2. Can be planned.

つまり、冷媒流路２に少なくとも３つ以上の流路領域を設置し、領域の中間部領域の断面積が他の流路領域よりも大きくなる流路構造とすることで、冷媒の乾き度の如何に関わらず冷媒流路２内における冷媒の熱伝達率を略一定にすることができる。   In other words, by providing at least three or more flow channel regions in the refrigerant flow channel 2 and having a flow channel structure in which the cross-sectional area of the intermediate region of the region is larger than that of other flow channel regions, the dryness of the refrigerant can be improved. Regardless, the heat transfer coefficient of the refrigerant in the refrigerant flow path 2 can be made substantially constant.

尚、直膨式冷凍サイクルの気液二相流においても、冷媒の流量を増すと、通常の流体と同様に流速の増加に伴い、熱伝達率αは向上する。   In the gas-liquid two-phase flow of the direct expansion type refrigeration cycle, when the flow rate of the refrigerant is increased, the heat transfer rate α is improved as the flow rate is increased as in the case of a normal fluid.

冷媒流路２の断面積Ａは、図２の実施例に示したような３段階に変化させる場合、第三流路の断面積Ａ３≦第一流路の断面積Ａ１＜第二流路の断面積Ａ２とすればよい。尚、冷媒流路２には各流路間を接続する２個の連絡流路２Ｂ（２Ｂ−１、２Ｂ−２）が必要となる。連絡流路２Ｂの配置位置は、冷媒流路２内に冷媒を均等に流入させることを考えて、各々を下部電極１Ｂの中心を挟んで対向する位置に設置するとよい。更に、連絡流路２Ｂ−１の断面積は第一流路２−１の断面積Ａ２と同等、またはそれ以上であることが望ましい。また、連絡流路２Ｂ−２の断面積は第三流路２−３の断面積Ａ３と同等、またはそれ以上であることが望ましい。   When the cross-sectional area A of the refrigerant flow path 2 is changed in three stages as shown in the embodiment of FIG. 2, the cross-sectional area A3 of the third flow path ≦ the cross-sectional area A1 of the first flow path <the break of the second flow path The area may be A2. In addition, the refrigerant | coolant flow path 2 requires the two communication flow paths 2B (2B-1, 2B-2) which connect between each flow path. The arrangement position of the communication channel 2B is preferably set at a position facing each other across the center of the lower electrode 1B in consideration of allowing the refrigerant to uniformly flow into the refrigerant channel 2. Furthermore, it is desirable that the cross-sectional area of the communication channel 2B-1 is equal to or larger than the cross-sectional area A2 of the first channel 2-1. The cross-sectional area of the communication channel 2B-2 is desirably equal to or larger than the cross-sectional area A3 of the third channel 2-3.

次に、図１の装置でウエハWのエッチング処理を行う場合の手順について、簡単に説明する。まず、ウエハWは図示しない被処理体搬送装置から処理室１００に搬入され、試料台１の試料載置面上に載置され、静電吸着により固定される。ついで、ウエハWのエッチングに必要なプロセスガスが図示しないガスラインより供給され、真空排気系２０により処理室１００は所定の処理圧力に調整される。次に、アンテナ電源２１及びバイアス電源２２の電力供給と、図示されない磁場形成手段の作用によりプラズマが生成され、このプラズマを用いたエッチング処理が開始される。プロセス中のウエハ温度の制御は、温度センサ６からの温度情報をモニタしながら温度制御システム１０１にてフィードバック制御を行い、圧縮機７、膨張弁９を調節して、冷媒の流量、蒸発温度を調節する。この際、試料台１内の冷媒流路２が、図２に示したように、冷媒の熱伝達率の変化に応じて断面積が変化する構造となっていることで、冷媒の相変化に起因する冷却能力の面内分布が低減され、試料台１の面内温度を均一かつ高速に制御することが可能となる。   Next, a procedure for performing the etching process on the wafer W with the apparatus of FIG. 1 will be briefly described. First, the wafer W is carried into the processing chamber 100 from a workpiece transfer apparatus (not shown), placed on the sample placement surface of the sample stage 1, and fixed by electrostatic adsorption. Next, a process gas necessary for etching the wafer W is supplied from a gas line (not shown), and the processing chamber 100 is adjusted to a predetermined processing pressure by the vacuum exhaust system 20. Next, plasma is generated by the power supply of the antenna power source 21 and the bias power source 22 and the action of magnetic field forming means (not shown), and an etching process using this plasma is started. The wafer temperature during the process is controlled by feedback control by the temperature control system 101 while monitoring the temperature information from the temperature sensor 6, and the compressor 7 and the expansion valve 9 are adjusted to adjust the flow rate of the refrigerant and the evaporation temperature. Adjust. At this time, as shown in FIG. 2, the refrigerant flow path 2 in the sample stage 1 has a structure in which the cross-sectional area changes in accordance with the change in the heat transfer coefficient of the refrigerant. The resulting in-plane distribution of the cooling capacity is reduced, and the in-plane temperature of the sample stage 1 can be controlled uniformly and at high speed.

尚、試料台１の温度分布をより精度良く均一に制御したい場合には、冷媒流路２を多元化すればよい。本発明の実施例２として、冷媒流路を多元化した（５段階変化）例を図５に示す。冷媒流路２は、冷媒供給口３に接続され左右２方向に分岐した第一流路２−１と、第一の連絡流路２Ｂ−１を経て左右２方向に分岐した第二流路２−２と、第二の連絡流路２Ｂ−２を経て左右２方向に分岐した第三流路２−３と、第三の連絡流路２Ｂ−３を経て左右２方向に分岐した第四流路２−４と、第四の連絡流路２Ｂ−４を経て左右２方向に分岐した第五流路２−５とを有し、第五流路２−５は冷媒排出口４に接続されている。   If the temperature distribution of the sample stage 1 is desired to be more accurately and uniformly controlled, the refrigerant flow path 2 may be multiple. As Example 2 of the present invention, FIG. 5 shows an example in which the refrigerant flow path is multi-dimensional (change in five steps). The refrigerant flow path 2 includes a first flow path 2-1 that is connected to the refrigerant supply port 3 and branches in the left and right directions, and a second flow path 2 that branches in the left and right directions through the first connection flow path 2B-1. 2, a third channel 2-3 branched in the left and right directions through the second connecting channel 2B-2, and a fourth channel branched in the left and right directions through the third connecting channel 2B-3 2-4 and a fifth flow path 2-5 branched in two left and right directions through the fourth communication flow path 2B-4, and the fifth flow path 2-5 is connected to the refrigerant outlet 4 Yes.

ここでも、冷媒の熱伝達率αが最大となる位置（ここでは第三の連絡流路２Ｂ−３と想定）で冷媒流路２の断面積が最大となるような構造とすることで、図４Ｂに実線で示したフラットな（最適化）特性により近い特性を得ることが出来、これにより、試料台１上のウエハの温度を面内均一に制御することが容易となる。   Here too, the structure is such that the cross-sectional area of the refrigerant flow path 2 is maximized at the position where the heat transfer coefficient α of the refrigerant is maximized (assumed here as the third communication flow path 2B-3). A characteristic closer to the flat (optimized) characteristic indicated by the solid line in FIG. 4B can be obtained, which makes it easy to control the temperature of the wafer on the sample stage 1 uniformly in the surface.

上記の図２や図５に示した例において、冷媒供給口３と冷媒排出口４の設置位置は逆転してもよい。ただしその場合には、図２を例として挙げれば、第一流路２−１と第三流路２−３の断面積Ａの関係が逆転し、また連絡流路２Ｂ−１と２Ｂ−２の断面積の関係も逆転させなければならない。   In the examples shown in FIG. 2 and FIG. 5, the installation positions of the refrigerant supply port 3 and the refrigerant discharge port 4 may be reversed. However, in that case, taking FIG. 2 as an example, the relationship between the cross-sectional areas A of the first flow path 2-1 and the third flow path 2-3 is reversed, and the connection flow paths 2B-1 and 2B-2 The cross-sectional area relationship must also be reversed.

図６に、冷媒流路内で断面積Ａが多段的に変化する冷媒流路の構造の例を示す。冷媒流路２は、各々の流路（２−１、２−２、２−３）内で多段的に断面積を拡大・縮小する構造とした。すなわち、流路（２−１）内で、２−１−１、２−１−２、流路（２−２）内で２−２−１、２−２−２、流路（２−３）内で２−３−１、２−３−２と夫々２段階に変化する。また、冷媒流路２の断面積は各々の流路内で連続的に変化する構造であってもよい。これにより、各流路内における冷媒の熱伝達率αの変化を抑制可能となり、図４Ｂに実線で示したフラットな（最適化）特性により近い特性を得ることが出来、周方向のウエハの温度差を低減することができる。   FIG. 6 shows an example of the structure of the refrigerant flow path in which the cross-sectional area A changes in a multistage manner in the refrigerant flow path. The refrigerant flow path 2 has a structure in which the cross-sectional area is expanded / reduced in a multistage manner in each flow path (2-1, 2-2, 2-3). That is, 2-1-1, 2-1-2 in the channel (2-1), 2-2-1, 2-2-2 in the channel (2-2), (2- Within 3), there are two stages, 2-3-1 and 2-3-2. Moreover, the cross-sectional area of the refrigerant | coolant flow path 2 may be a structure which changes continuously in each flow path. This makes it possible to suppress the change in the heat transfer coefficient α of the refrigerant in each flow path, and to obtain characteristics closer to the flat (optimized) characteristics shown by the solid line in FIG. 4B. The difference can be reduced.

図７に、本発明の他の実施例として、流路本数にて冷媒流路２の断面積を拡大・縮小した例を示す。各流路の断面積Ａはほぼ同等とし、冷媒供給口３から２つに分岐した流路２を、冷媒の熱伝達率αが最大となる乾き度領域においては連絡流路２Ｂ−１．２Ｂ−２により４本に増やし、結果として冷媒の断面積を増加させ、これら４本の流路を連絡流路２Ｂ−３で２本に集約したのち冷媒排出口４に接続している。これにより、冷媒の熱伝達率αが最大となる乾き度領域における冷媒の熱伝達率αの上昇を抑制し、冷媒の熱伝達率を冷媒流路２内にて略一定にし、試料台１上のウエハの温度を面内均一に制御できる。   FIG. 7 shows an example in which the cross-sectional area of the refrigerant flow path 2 is enlarged or reduced by the number of flow paths as another embodiment of the present invention. The cross-sectional areas A of the respective flow paths are substantially equal, and the flow path 2 branched into two from the refrigerant supply port 3 is connected to the flow path 2B-1.2B in the dryness region where the heat transfer coefficient α of the refrigerant is maximum. -2, the cross-sectional area of the refrigerant is increased. As a result, the four flow paths are combined into two by the communication flow path 2B-3 and then connected to the refrigerant discharge port 4. As a result, an increase in the heat transfer coefficient α of the refrigerant in the dryness region where the heat transfer coefficient α of the refrigerant is maximized is suppressed, the heat transfer coefficient of the refrigerant is made substantially constant in the refrigerant flow path 2, and The wafer temperature can be controlled uniformly in the surface.

図８に冷媒流路２の内壁の形状にて流路内の熱伝達率を制御した、他の実施例を示す。冷媒流路２の内壁に凹凸形状を設ければ、冷媒の攪拌（対流）、及び伝熱面積が向上するため、熱伝達率αが上昇する。そこで、冷媒の熱伝達率が高い乾き度領域（図中２−２）では、冷媒流路２の内壁の凹凸を低くして（無しにしてもよい）熱伝達率の上昇を抑制し、冷媒の熱伝達率が低い乾き度領域（図中２−１、２−３）では凹凸を高くして熱伝達率を上昇させることで、冷媒流路２内において熱伝達率αを一定に保つことができる。尚、冷媒流路幅（径）に対して凹凸の高さが２%以上あれば熱伝達率の向上が図れる。凹凸が過度に高い場合は圧力損失も問題となるため、凹凸の高さは冷媒流路幅（径）に対して２〜１０%程度とすることが望ましい。また、凹凸を冷媒進行方向に対して斜めに設置すると、圧力損失を抑えながら、熱伝達率を向上させることができる。   FIG. 8 shows another embodiment in which the heat transfer coefficient in the flow path is controlled by the shape of the inner wall of the refrigerant flow path 2. If the concave and convex shape is provided on the inner wall of the refrigerant flow path 2, the refrigerant agitation (convection) and the heat transfer area are improved, so that the heat transfer coefficient α is increased. Therefore, in the dryness region (2-2 in the figure) where the heat transfer coefficient of the refrigerant is high, the unevenness of the inner wall of the refrigerant flow path 2 is lowered (may be omitted) to suppress an increase in the heat transfer coefficient. In the dryness region (2-1, 2-3 in the figure) where the heat transfer coefficient is low, the heat transfer coefficient α is kept constant in the refrigerant flow path 2 by increasing the unevenness and increasing the heat transfer coefficient. Can do. In addition, if the height of the unevenness is 2% or more with respect to the refrigerant flow path width (diameter), the heat transfer coefficient can be improved. When the unevenness is excessively high, pressure loss is also a problem. Therefore, the height of the unevenness is desirably about 2 to 10% with respect to the refrigerant flow path width (diameter). Further, if the unevenness is installed obliquely with respect to the direction of travel of the refrigerant, the heat transfer rate can be improved while suppressing pressure loss.

尚、上記に示した本発明の計算例では、乾き度が約０.５の時に冷媒の熱伝達率αが最大値となったが、実条件においては、使用する冷媒の種類や冷媒流路の内壁形状、または冷媒流量などによって熱伝達率が最大となる乾き度Ｘが変化する。   In the calculation example of the present invention described above, the heat transfer coefficient α of the refrigerant becomes the maximum value when the dryness is about 0.5. However, under actual conditions, the type of refrigerant used and the refrigerant flow path The dryness X at which the heat transfer coefficient is maximized varies depending on the shape of the inner wall or the flow rate of the refrigerant.

例えば、冷媒流路内の凹凸を最適化してドライアウトの発生を抑制できれば、乾き度が０.５〜０.９の間で熱伝達率が最大になることも考えられる。その場合には、本発明の図２〜６における冷媒流路断面積Ａの最大拡大位置を、冷媒の最大熱伝達率αが発生する乾き度領域に合わせればよい。尚、上記のように冷媒の熱伝達率が最大となるのは乾き度が０.５〜０.９の間であると考えられるため、流路長の半分以上の位置（後半位置）において、冷媒流路の最大拡大位置が存在することになる。   For example, if the unevenness in the refrigerant flow path is optimized to suppress the occurrence of dryout, the heat transfer coefficient may be maximized when the dryness is between 0.5 and 0.9. In that case, the maximum expansion position of the refrigerant flow path cross-sectional area A in FIGS. 2 to 6 of the present invention may be matched with the dryness region where the maximum heat transfer coefficient α of the refrigerant is generated. In addition, since it is thought that the dryness is between 0.5 and 0.9 that the heat transfer coefficient of the refrigerant is maximized as described above, at a position more than half of the flow path length (second half position) There will be a maximum expansion position of the refrigerant flow path.

図９に、本発明の他の実施例として、直膨式冷凍サイクルの熱伝達率の変化を利用して、ウエハの面内温度を制御する例を示す。通常の直膨式冷凍サイクルでは、ウエハの入熱に対応する冷媒量Ｑを試料台内の冷媒流路に供給する。これにより、図９中、領域（１）のように、冷媒は試料台内で液相から気相（乾き度Ｘ＝０→１）に完全蒸発する。   FIG. 9 shows an example in which the in-plane temperature of the wafer is controlled using the change in the heat transfer coefficient of the direct expansion refrigeration cycle as another embodiment of the present invention. In a normal direct expansion refrigeration cycle, the refrigerant quantity Q corresponding to the heat input of the wafer is supplied to the refrigerant flow path in the sample stage. Accordingly, as shown in region (1) in FIG. 9, the refrigerant completely evaporates from the liquid phase to the gas phase (dryness X = 0 → 1) in the sample stage.

これに対し、冷媒をウエハの入熱に対して過度に供給すると、冷媒は完全蒸発せずに試料台より排出されることになり、冷媒流路内の熱伝達率の分布は領域（２）のようになる。領域（２）では、乾き度Ｘ＝０.５程度で試料台から冷媒を排出している。これにより、冷媒流路内の熱伝達率の分布は領域（１）から領域（２）に変化し、冷媒流路内における後半の冷媒熱伝達率αが増加する。この機能を利用すれば、ウエハ面内の温度分布制御が可能となる。   On the other hand, if the refrigerant is excessively supplied to the heat input of the wafer, the refrigerant is not completely evaporated and is discharged from the sample stage, and the distribution of the heat transfer coefficient in the refrigerant flow path is the region (2). become that way. In the area (2), the refrigerant is discharged from the sample stage with a dryness X of about 0.5. As a result, the distribution of the heat transfer coefficient in the refrigerant flow path changes from the region (1) to the region (2), and the second half heat transfer coefficient α in the refrigerant flow channel increases. If this function is used, the temperature distribution in the wafer surface can be controlled.

尚、図中領域（３）のように、試料台に供給する前にあらかじめ冷媒の乾き度Ｘを上げておく（領域（３）ではＸ＝０.５程度まで上昇）ことが出来れば、冷媒流路２の前半部分の冷媒熱伝達率αが増加し、これによってもウエハ面内の温度分布制御が可能となる。領域（２）の分布制御を行う場合には、直膨式冷凍サイクル内の圧縮機の回転数をコントロールすればよい。   As shown in the area (3) in the figure, if the dryness X of the refrigerant can be increased in advance before being supplied to the sample stage (in the area (3), X can be increased to about 0.5), the refrigerant The refrigerant heat transfer coefficient α in the first half of the flow path 2 increases, and this also enables temperature distribution control within the wafer surface. When the distribution control of the region (2) is performed, the rotational speed of the compressor in the direct expansion refrigeration cycle may be controlled.

また、領域（３）の分布制御は、試料台の前の冷凍サイクル中にヒータなどの冷媒気化手段を設置し、乾き度Ｘを制御すればよい。尚、冷媒流量を増加させることにより生じる冷媒の熱伝達率の全体的な増加は、冷媒の圧力（冷媒蒸発温度）を上昇させ、冷却能力を抑制することにより対応すればよい。   Further, the distribution control of the region (3) may be performed by controlling the degree of dryness X by installing a refrigerant vaporization means such as a heater in the refrigeration cycle in front of the sample stage. Note that the overall increase in the heat transfer coefficient of the refrigerant caused by increasing the refrigerant flow rate may be dealt with by increasing the refrigerant pressure (refrigerant evaporation temperature) and suppressing the cooling capacity.

更に、領域（２）、領域（３）の制御が可能であるならば、下記のような方法でウエハの面内温度分布の均一化を図ってもよい。   Furthermore, if the control of the region (2) and the region (3) is possible, the in-plane temperature distribution of the wafer may be made uniform by the following method.

上記（２）領域の制御と、試料台の冷媒流路２の流路断面積を冷媒供給口から冷媒排出口にむけて連続的に拡大させる構造を組合わせることで、乾き度Ｘ＝０〜０．５付近の範囲で、冷媒熱伝達率αが右肩上がりの直線で表される特性の右肩上がりを抑制し、ウエハの面内温度分布を均一にできる。   By combining the control of the above (2) region and the structure in which the channel cross-sectional area of the coolant channel 2 of the sample stage is continuously expanded from the coolant supply port to the coolant discharge port, the dryness X = 0 to 0 Within the range of about 0.5, the heat transfer coefficient α of the refrigerant can be suppressed from rising to the right with the characteristic represented by the straight line rising to the right, and the in-plane temperature distribution of the wafer can be made uniform.

また、上記（３）領域の制御と、試料台の冷媒流路２の流路断面積を冷媒供給口から冷媒排出口にむけて連続的に縮小させる構造を組合わせることで、乾き度Ｘ＝０．５付近〜１の範囲で、冷媒熱伝達率αが右肩下がり直線で表される特性の右肩下がりを抑制し、ウエハの面内温度分布を均一にできる。   Further, by combining the control of the above (3) region and the structure in which the channel cross-sectional area of the coolant channel 2 of the sample stage is continuously reduced from the coolant supply port to the coolant discharge port, the dryness X = In the range from about 0.5 to 1, the heat transfer coefficient α of the refrigerant can be suppressed from decreasing to the right, which is a characteristic represented by a straight line with a downward slope.

尚、冷媒が完全蒸発せずに冷媒流路２を通過する場合には、冷媒が液体のまま圧縮機に流入し、圧縮機を破損する恐れがある。その場合には、圧縮機直前の流路中に冷媒を完全蒸発させる気化器の設置が必要となる。気化器の例としてはサクションタンクなどが考えられる。   When the refrigerant passes through the refrigerant flow path 2 without completely evaporating, the refrigerant may flow into the compressor as a liquid, and the compressor may be damaged. In that case, it is necessary to install a vaporizer that completely evaporates the refrigerant in the flow path immediately before the compressor. An example of a vaporizer is a suction tank.

図１０に、本発明の他の実施例になるプラズマ処理装置の全体的なシステム構成を示す。この実施例のプラズマ処理装置は、図１の実施例の構成に加えて、下部電極（静電吸着電極）１Ｂの誘電体膜中にヒータ層１３が設けられている。ヒータ層１３は、例えば、円板状の下部電極１Ｂの中央部分、リング状の外周部分及びこれら２つの部分の間に位置する中間部分の３領域に分かれて形成されている。   FIG. 10 shows an overall system configuration of a plasma processing apparatus according to another embodiment of the present invention. In the plasma processing apparatus of this embodiment, in addition to the configuration of the embodiment of FIG. 1, a heater layer 13 is provided in the dielectric film of the lower electrode (electrostatic adsorption electrode) 1B. The heater layer 13 is divided into three regions, for example, a central portion of the disk-shaped lower electrode 1B, a ring-shaped outer peripheral portion, and an intermediate portion located between these two portions.

ウエハＷの温度は、プラズマエッチ等の処理条件、すなわちプラズマからウエハＷのへの入熱状況と、各ヒータ領域の出力と、冷媒流路２内の冷媒による冷却状況により変化する。ヒータ層１３の３つ領域には夫々温度センサが設けられ、ヒータ電源１４から各ヒータ領域へ供給される電力が、冷凍サイクルの流路２を流れる冷媒流量などと共に、温度制御システム１０１で制御される。   The temperature of the wafer W varies depending on processing conditions such as plasma etching, that is, the heat input state from the plasma to the wafer W, the output of each heater region, and the cooling state by the refrigerant in the refrigerant flow path 2. A temperature sensor is provided in each of the three regions of the heater layer 13, and the electric power supplied from the heater power source 14 to each heater region is controlled by the temperature control system 101 together with the flow rate of the refrigerant flowing through the flow path 2 of the refrigeration cycle. The

次に、図１０の装置の動作について、簡単に説明する。まずウエハWが処理室１００に搬入され、下部電極１上に載置、固定される。ついで、プロセスガスが供給され、処理室１００は所定の処理圧力に調整される。次に、アンテナ電源２１及びバイアス電源２２の電力供給と、図示されない磁場形成手段の作用によりプラズマが生成され、このプラズマを用いたエッチング処理がなされる。プロセス中のウエハ温度の制御は、温度センサ６からの温度情報をモニタしながら温度制御システム１０１にてフィードバック制御を行い、圧縮機７、膨張弁９、ヒータ電源１４を調節して、冷媒の流量、蒸発温度、及びヒータ層１３の各領域の加熱量を調節することによって行なわれる。
この際、試料台１内の冷媒流路２が、冷媒の熱伝達率の変化に応じて断面積が変化する構造と成っていることで、冷媒の相変化に起因する冷却能力の面内分布が低減され、試料の面内温度を均一かつ高速に制御可能となる。 Next, the operation of the apparatus shown in FIG. 10 will be briefly described. First, the wafer W is loaded into the processing chamber 100 and placed and fixed on the lower electrode 1. Then, process gas is supplied, and the processing chamber 100 is adjusted to a predetermined processing pressure. Next, plasma is generated by the power supply of the antenna power source 21 and the bias power source 22 and the action of a magnetic field forming unit (not shown), and an etching process using the plasma is performed. The wafer temperature during the process is controlled by feedback control by the temperature control system 101 while monitoring the temperature information from the temperature sensor 6, and by adjusting the compressor 7, the expansion valve 9, and the heater power supply 14, the flow rate of the refrigerant. It is performed by adjusting the evaporation temperature and the heating amount of each region of the heater layer 13.
At this time, the refrigerant flow path 2 in the sample stage 1 has a structure in which the cross-sectional area changes according to the change in the heat transfer coefficient of the refrigerant, so that the in-plane distribution of the cooling capacity due to the phase change of the refrigerant. And the in-plane temperature of the sample can be controlled uniformly and at high speed.

さらに、図９で説明した以下の方法を併せ採用することにより、ウエハの面内温度分布を任意に制御できる。   Furthermore, by adopting the following method described with reference to FIG. 9, the in-plane temperature distribution of the wafer can be arbitrarily controlled.

（１）圧縮機７により冷媒流路２へ冷媒を過度に（入熱量以上に）供給する。または、ウエハWの温度上昇の上限を考慮しながら、冷媒を不足側に制御してもよい。   (1) The refrigerant is supplied to the refrigerant flow path 2 excessively (more than the heat input amount) by the compressor 7. Alternatively, the refrigerant may be controlled to the shortage side while considering the upper limit of the temperature rise of the wafer W.

（２）試料台１と膨張弁９の間に乾き度調節手段１０を設置して、試料台１に供給する冷媒の乾き度を調節する。   (2) A dryness adjusting means 10 is installed between the sample stage 1 and the expansion valve 9 to adjust the dryness of the refrigerant supplied to the sample stage 1.

これらの構成及び制御方法を採用することにより、高ウエハバイアス電力の印加による大入熱エッチング条件においても、ウエハWの面内全体で高精度な加工が可能となる。   By employing these configurations and control methods, high-precision processing can be performed on the entire surface of the wafer W even under high heat input etching conditions by applying high wafer bias power.

このようなプロセスを経てエッチングが完了し、電力、磁場及びプロセスガスの供給が停止される。   Etching is completed through such a process, and the supply of power, magnetic field and process gas is stopped.

尚、プラズマの生成手段が、ウエハWの対面に配置された電極にウエハWに印加されるのとは別の高周波電力を印加する方式、誘導結合方式、磁場と高周波電力の相互作用方式、試料台１に高周波電力を印加する方式のいずれの方式であっても、本発明が有効であることは言うまでもない。
また、本発明はウエハWに３W/cm２以上の高周波電力を印加するような大入熱が生じる加工条件に対応し、アスペクト比が１５以上となる高アスペクトの深孔加工を行なう際にも有効である。プラズマ処理を行なう薄膜は、SiO２、Si３N４、SiOC、SiOCH、SiCのいずれか１種類を主成分とする単一の膜、または２種類以上の膜種にて構成される多層膜などが想定される。 The plasma generating means applies a high frequency power different from that applied to the wafer W to the electrode disposed on the opposite side of the wafer W, an inductive coupling method, a magnetic field and high frequency power interaction method, a sample Needless to say, the present invention is effective for any method of applying high-frequency power to the table 1.
In addition, the present invention corresponds to a processing condition in which a large heat input such as applying a high frequency power of 3 W / cm 2 or more is applied to the wafer W, and also when performing high aspect deep hole processing with an aspect ratio of 15 or more. It is valid. The thin film to be subjected to the plasma treatment is a single film mainly composed of any one of SiO 2 , Si 3 N 4 , SiOC, SiOCH, and SiC, or a multilayer film composed of two or more kinds of films. Is assumed.

図１１に、蒸発器を構成する冷媒流路２の他の実施例として、冷媒流路が一本の連続した流路であり、その流路内の断面積が拡大・縮小している例を示す。冷媒流路２は、冷媒供給口３に接続され断面積が２段に拡大した第一流路２−１（２−１−１、２−１−２）と、第一流路よりも断面積が拡大した第二流路２−２と、第二流路よりも断面積が縮小した第三流路２−３とを有し、第三流路２−３は冷媒排出口４に接続されている。冷媒流路２を一本の連続した流路とすることで、冷媒の分岐部において冷媒が均等に分岐せず、面内の温度差が発生するリスクを低減できる。直膨式冷凍サイクルでは冷媒の蒸発潜熱を利用することから、単位流量あたりの冷却能力が高く、冷媒の流量が従来の液体冷媒方式などに比べて少ない。そのため、冷媒流路２内に冷媒の分岐部を設ける場合には、流路１本に対して分岐数を２〜４本程度までに抑えた方がよい。これより多い分岐数には、冷媒用のディストリビュータ（分配器）を設置することが望ましい。   FIG. 11 shows another example of the refrigerant flow path 2 constituting the evaporator, in which the refrigerant flow path is a single continuous flow path, and the cross-sectional area in the flow path is enlarged or reduced. Show. The refrigerant flow path 2 is connected to the refrigerant supply port 3 and has a first flow path 2-1 (2-1-1, 1-2-1-2) whose cross-sectional area is expanded in two stages, and a cross-sectional area larger than that of the first flow path. The enlarged second flow path 2-2 and the third flow path 2-3 having a smaller cross-sectional area than the second flow path are connected to the refrigerant discharge port 4. Yes. By making the refrigerant flow path 2 one continuous flow path, it is possible to reduce the risk that the refrigerant is not evenly branched at the refrigerant branching portion and an in-plane temperature difference occurs. Since the direct expansion refrigeration cycle uses the latent heat of vaporization of the refrigerant, the cooling capacity per unit flow rate is high, and the flow rate of the refrigerant is smaller than that of the conventional liquid refrigerant method. Therefore, when providing the refrigerant | coolant branch part in the refrigerant | coolant flow path 2, it is better to suppress the number of branches to about 2-4 with respect to one flow path. For a larger number of branches, it is desirable to install a refrigerant distributor.

図１２に、蒸発器を構成する冷媒流路２の他の実施例として、冷媒流路が一本の連続した流路であり、その流路内の断面積が拡大・縮小して、かつその流路が多元的に設置されている例を示す。冷媒流路２は、２つの冷媒供給口３、３’に接続された第一流路２−１、２−１’及び、断面積が拡大した第二流路２−２、２−２’及び、の断面積が縮小した第三流路２−３、２−３’を有し、２つの第三流路は２つの冷媒排出口４、４’に接続されている。   In FIG. 12, as another embodiment of the refrigerant flow path 2 constituting the evaporator, the refrigerant flow path is a single continuous flow path, the cross-sectional area in the flow path is enlarged / reduced, and An example in which the flow paths are installed in a pluralistic manner is shown. The refrigerant flow path 2 includes first flow paths 2-1 and 2-1 ′ connected to two refrigerant supply ports 3 and 3 ′, and second flow paths 2-2 and 2-2 ′ having an enlarged cross-sectional area, and The third flow paths 2-3 and 2-3 ′ have a reduced cross-sectional area, and the two third flow paths are connected to the two refrigerant discharge ports 4 and 4 ′.

冷媒流路２が各々独立した構造であることから、各流路の冷媒の圧力（冷媒蒸発温度）を別々に制御することで、試料台１上のウエハの面内温度分布を任意に制御することもできる。   Since each of the refrigerant flow paths 2 has an independent structure, the in-plane temperature distribution of the wafer on the sample stage 1 is arbitrarily controlled by separately controlling the refrigerant pressure (refrigerant evaporation temperature) in each flow path. You can also.

尚、図１２の例は２つの冷媒流路２が示されているが、独立した冷媒流路２を更に多元化する、例えば、試料台１の試料載置面に対応する面を３等分あるいは４等分し、分割された各面内において一本の連続した冷媒流路の断面積を前記各実施例のように途中で変更する構成とすることにより、ウエハの面内温度分布のより緻密な制御を行うようにしても良い。   In the example of FIG. 12, two refrigerant flow paths 2 are shown. However, the independent refrigerant flow paths 2 are further diversified, for example, the surface corresponding to the sample mounting surface of the sample stage 1 is divided into three equal parts. Alternatively, it is divided into four equal parts, and the sectional area of one continuous refrigerant flow path is changed in the middle as in each of the above-described embodiments, so that the in-plane temperature distribution of the wafer can be changed. Fine control may be performed.

本発明が提案するプラズマ処理装置における温調ユニットは、上記の実施例のみに限定されず、アッシング装置、スパッタ装置、イオン注入装置、レジスト塗布装置、プラズマCVD装置などの高速かつ面内均一なウエハの温度制御を必要とする装置にも転用が可能である。   The temperature control unit in the plasma processing apparatus proposed by the present invention is not limited to the above-described embodiment, but a high-speed and in-plane uniform wafer such as an ashing apparatus, a sputtering apparatus, an ion implantation apparatus, a resist coating apparatus, and a plasma CVD apparatus. It can be diverted to a device that requires temperature control.

１…試料台、１Ａ…基材部、１Ｂ…下部電極（静電吸着電極）、２…冷媒流路、３…冷媒供給口、４…冷媒排出口、６…温度センサ、７…圧縮機、８…凝縮器、９…膨張弁、１０…冷媒蒸発器、１１…伝熱ガス供給系、１３…ヒータ、１４…ヒータ電源、１５…電極プレート、２０…真空排気系、２１…アンテナ電源、２２…バイアス電源、１００…処理室、１０１…温度制御システム、W…ウエハ。   DESCRIPTION OF SYMBOLS 1 ... Sample stand, 1A ... Base material part, 1B ... Lower electrode (electrostatic adsorption electrode), 2 ... Refrigerant flow path, 3 ... Refrigerant supply port, 4 ... Refrigerant discharge port, 6 ... Temperature sensor, 7 ... Compressor, DESCRIPTION OF SYMBOLS 8 ... Condenser, 9 ... Expansion valve, 10 ... Refrigerant evaporator, 11 ... Heat transfer gas supply system, 13 ... Heater, 14 ... Heater power supply, 15 ... Electrode plate, 20 ... Vacuum exhaust system, 21 ... Antenna power supply, 22 ... bias power supply, 100 ... processing chamber, 101 ... temperature control system, W ... wafer.

Claims (3)

真空処理室内に導入された処理ガスをプラズマ化し、該プラズマにて試料台の試料載置面に載置された被処理基板の表面処理を行うプラズマ処理装置において、
前記試料台でかつ前記試料載置面の下部に設けられた冷媒流路を有し、
前記試料台の冷媒流路と圧縮機と凝縮器と膨張弁とがこの順に連結され前記試料台の冷媒流路が蒸発器として動作する冷凍サイクルを構成し、
前記試料台の冷媒流路が、冷媒供給口と冷媒排出口との間に形成された、断面積が増大していく流路または減少していく流路あるいは増大した後減少していく流路のいずれかを有し、
前記冷凍サイクルを構成する圧縮機の入口側と前記冷媒排出口との間に設置された気化器を有し、
前記冷凍サイクルにおいて気液二相の状態にある前記冷媒の乾き度を前記冷媒流路の断面積が最大となる位置で冷媒の熱伝達率が最大値になるように調節すると共に、該冷媒を前記冷媒排出口から完全蒸発させずに排出し、前記気化器で蒸発させることを特徴とするプラズマ処理装置。 In a plasma processing apparatus for converting a processing gas introduced into a vacuum processing chamber into plasma and performing surface treatment of a substrate to be processed placed on a sample placement surface of a sample stage with the plasma,
A coolant channel provided at a lower portion of the sample stage and the sample mounting surface;
The refrigerant path of the sample stage, the compressor, the condenser, and the expansion valve are connected in this order to constitute a refrigeration cycle in which the refrigerant path of the sample stage operates as an evaporator,
The refrigerant channel of the sample stage is formed between the refrigerant supply port and the refrigerant discharge port, and the cross-sectional area increases, decreases, or increases and decreases. One of
Having a vaporizer installed between the inlet side of the compressor constituting the refrigeration cycle and the refrigerant outlet;
Adjusting the degree of dryness of the refrigerant in a gas-liquid two-phase state in the refrigeration cycle so that the heat transfer coefficient of the refrigerant reaches a maximum value at a position where the cross-sectional area of the refrigerant flow path becomes maximum ; The plasma processing apparatus is characterized in that it is discharged from the refrigerant discharge port without being completely evaporated and evaporated by the vaporizer. 請求項１に記載のプラズマ処理装置において、前記試料台の冷媒流路の冷媒供給口と前記膨張弁との間に配置された別の冷媒の気化器を有し、
前記冷凍サイクルにおいて冷媒の流量、冷媒の圧力の調節または前記別の気化器の動作により前記冷媒の乾き度を前記冷媒流路の断面積が最大となる位置で冷媒の熱伝達率が最大値になるように調節することを特徴とするプラズマ処理装置。 The plasma processing apparatus according to claim 1, further comprising another refrigerant vaporizer disposed between the refrigerant supply port of the refrigerant flow path of the sample stage and the expansion valve.
In the refrigeration cycle, the refrigerant heat transfer coefficient is maximized at the position where the cross-sectional area of the refrigerant flow path is maximized by adjusting the flow rate of refrigerant, the pressure of the refrigerant, or the operation of the separate vaporizer. It adjusts so that it may become . The plasma processing apparatus characterized by the above-mentioned . プラズマ処理装置により、真空処理室内に導入された処理ガスをプラズマ化し、該プラズマにて試料台の試料載置面に載置された被処理基板の表面処理を行うプラズマ処理方法において、
前記試料台の試料載置面の下方に設けられた冷媒流路を蒸発器として、圧縮機、凝縮器、膨張弁をこの順に連結されて備える冷凍サイクルが構成されており、
前記試料台の冷媒流路が冷媒供給口と冷媒排出口との間に形成され、断面積が増大していく流路または減少していく流路あるいは増大した後減少していく流路のいずれかを有し、
前記試料台の試料載置面に近接して設けられた温度センサと、
前記圧縮機の入口側と前記冷媒排出口との間の流路中に設置された気化器と、
前記冷凍サイクルの動作を調節して前記試料載置面の温度を制御する温度調節機構とを有し、
前記プラズマにて前記試料載置面に載置された前記被処理基板の表面処理を行い、
前記温度センサで検出された温度に基づいて、前記冷媒の圧力や前記圧縮機の回転数を制御して前記冷媒の流量及び前記冷媒の圧力を制御する、または冷媒の乾き度を調節することで、前記冷媒流路内における前記気液二相の状態の前記冷媒の乾き度を前記冷媒流路の断面積が最大となる位置で冷媒の熱伝達率が最大値になるように調節し、前記試料載置面内の温度分布が目標値になるように制御すると共に、
前記冷媒を、前記冷媒排出口から完全蒸発させずに排出し、該冷媒を前記気化器で蒸発させることを特徴とするプラズマ処理方法。 In a plasma processing method for converting a processing gas introduced into a vacuum processing chamber into a plasma by a plasma processing apparatus and performing a surface treatment of a substrate to be processed mounted on a sample mounting surface of a sample stage with the plasma,
The refrigerant flow path provided below the sample mounting surface of the sample stage is an evaporator, and a refrigeration cycle including a compressor, a condenser, and an expansion valve connected in this order is configured.
The refrigerant channel of the sample stage is formed between the refrigerant supply port and the refrigerant discharge port, and either the channel whose cross-sectional area increases, the channel that decreases, or the channel that decreases after increasing Have
A temperature sensor provided in proximity to the sample mounting surface of the sample stage;
A vaporizer installed in a flow path between the inlet side of the compressor and the refrigerant outlet;
A temperature adjusting mechanism that controls the temperature of the sample mounting surface by adjusting the operation of the refrigeration cycle ,
Surface treatment of the substrate to be processed placed on the sample placement surface with the plasma,
Based on the temperature detected by the temperature sensor, the flow rate of the refrigerant and the pressure of the refrigerant are controlled by controlling the pressure of the refrigerant and the rotation speed of the compressor , or by adjusting the dryness of the refrigerant. Adjusting the dryness of the refrigerant in the gas-liquid two-phase state in the refrigerant flow path so that the heat transfer coefficient of the refrigerant is maximized at a position where the cross-sectional area of the refrigerant flow path is maximized , While controlling so that the temperature distribution in the sample mounting surface becomes the target value,
A plasma processing method, wherein the refrigerant is discharged from the refrigerant discharge port without being completely evaporated, and the refrigerant is evaporated by the vaporizer.
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