Plasma processing apparatus and plasma processing method

Abstract

There is provided a means for uniformly controlling the in-plane temperature of a semiconductor wafer at high speed in a high heat input etching process. A refrigerant channel structure in a circular shape is formed in a sample stage. Due to a fact that a heat transfer coefficient of a refrigerant is largely changed from a refrigerant supply port to a refrigerant outlet port, the cross sections of the channel structure is structured so as to be increased from a first channel areas towards a second channel areas in order to make the heat transfer coefficient of the refrigerant constant in the refrigerant channel structure. Thereby, the heat transfer coefficient of the refrigerant is prevented from increasing by reducing the flow rate of the refrigerant at a dry degree area where the heat transfer coefficient of the refrigerant is increased. Further, the cross section of the channel structure is structured so as to be reduced from the second channel areas towards a third channel areas, and thereby the heat transfer coefficient of the refrigerant is prevented from decreasing. Accordingly, the heat transfer coefficient of the refrigerant can be uniformed in the channel structure.

1 . A plasma processing apparatus which converts a process gas introduced inside a vacuum processing chamber into plasma and which performs surface processing, by using the plasma, on a sample that is placed on an electrostatic absorption electrode of a sample stage, the apparatus comprising:
 a refrigerant channel structure which is provided in the sample stage under the electrostatic absorption electrode, wherein the refrigerant channel structure configures an evaporator of a refrigeration cycle; and   a refrigerant supply port and a refrigerant outlet port which supplies and evacuates a refrigerant for cooling to/from the refrigerant channel structure,   wherein the refrigerant channel structure of the sample stage is formed between the refrigerant supply port and the refrigerant outlet port and have at least three channel areas that are sequentially connected to each other from the side of the refrigerant supply port to the side of the refrigerant outlet port, and the cross section of the middle channel area among at least three channel areas is larger than those of the other channel areas.   
   
   
       2 . The plasma processing apparatus according to  claim 1 ,
 wherein the refrigerant channel structure provided in the sample stage comprises a concentric circular channel having at least three channel areas, and the cross section of the middle channel area among the channel areas is larger than those of the other channel areas.   
   
   
       3 . The plasma processing apparatus according to  claim 1 ,
 wherein the refrigerant channel structure provided in the sample stage comprises a plurality of circular channels, and a plurality of channels that connect between the circular channels are arranged at positions opposed to each other in the in-plane of the sample stage.   
   
   
       4 . The plasma processing apparatus according to  claim 1 ,
 wherein irregularities are formed on inner walls of at least three channel areas, and the heights of the irregularities of the middle channel area among at least three channel areas are lower than those of the other channel areas.   
   
   
       5 . The plasma processing apparatus according to  claim 1 ,
 wherein the refrigerant channel structure of a swirl path provided in the sample stage is provided in the same in-plane, and a plurality of areas having different cross sections from each other are continuously provided.   
   
   
       6 . The plasma processing apparatus according to  claim 1 ,
 wherein the channel structure provided in the sample stage is provided in the same in-plane, and a plurality of refrigerant channels units each of in which a plurality of areas having different cross sections from each other are continuously provided are arranged in a diversified manner.   
   
   
       7 . The plasma processing apparatus according to  claim 1 ,
 wherein each cross section of the at least three channel areas is structured in such a manner that a heat transfer coefficient of a refrigerant in each channel area is made substantially constant irrespective of the dry degree of the refrigerant.   
   
   
       8 . The plasma processing apparatus according to  claim 1 ,
 wherein the refrigerant is excessively supplied in response to a heat input to the sample, and the refrigerant is evacuated from the sample stage at a dry degree X of approximately 0.5.   
   
   
       9 . The plasma processing apparatus according to  claim 1 ,
 wherein a means for increasing the dry degree X of the refrigerant to a predetermined value or more in advance before supplying to the sample stage is provided.   
   
   
       10 . A plasma processing method in which a process gas introduced inside a vacuum processing chamber is converted into plasma and surface processing is performed, by using the plasma, on a sample that is placed on an electrostatic absorption electrode of a sample stage by a plasma processing apparatus,
 wherein a refrigeration cycle including a compressor, a condenser and an expansion valve is configured with a refrigerant channel structure, as an evaporator, which is provided in a lower portion of the electrostatic absorption electrode of the sample stage in the plasma processing apparatus,   the refrigerant channel structure in the sample stage is formed between a refrigerant supply port and a refrigerant outlet port and have at least three channel areas that are sequentially connected to each other from the side of the refrigerant supply port to the side of the refrigerant outlet port, and the cross section of the middle channel area among at least three channel areas is larger than those of the other channel areas, and   a refrigerant supply port and a refrigerant outlet port which supplies and evacuates a refrigerant for cooling to/from the refrigerant channel structure,   the method comprising the step of:
 controlling the in-plane temperature distribution of the sample by adjusting the dry degree of the refrigerant that flows in the electrostatic absorption electrode. 
   
   
   
       11 . The plasma processing method according to  claim 10 , further comprising the steps of:
 excessively supplying the refrigerant to the refrigerant channel structure by the compressor in response to a heat input to the sample, and   controlling the flow volume of the refrigerant on the insufficient side within a range where the temperature rise of the sample that is detected by the temperature sensor reaches the upper limit.   
   
   
       12 . The plasma processing method according to  claim 10 , further comprising the step of:
 adjusting the dry degree of the refrigerant supplied to the refrigerant channel structure of the sample stage by a dry degree adjusting means provided between the sample stage and the expansion valve.