JP3485538B2 - Plasma processing equipment - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma processing apparatus, and more particularly to a plasma control apparatus capable of controlling the in-plane temperature distribution of an object to be processed.

[0002]

2. Description of the Related Art Japanese Unexamined Patent Publication No. 7-86382 discloses a plasma processing apparatus for processing an object to be processed such as a wafer by using plasma in a vacuum chamber. In this device, the object to be processed on the mounting table is electrostatically adsorbed to the mounting table, and a cooling gas such as helium is supplied between the mounting table and the object to be processed while supplying a refrigerant from the outside to the mounting table. Have been shown to improve the heat transfer coefficient between the wafer and the mounting table.

By the way, the outer diameter of the semiconductor wafer, which is the object to be processed, is increasing, and the minimum processing dimension is becoming finer. Along with this, nonuniformity of plasma processing in the central portion and the outer peripheral portion of the wafer becomes apparent. As a countermeasure against this, a method is known in which the plasma processing is made uniform by making the cooling ability for the wafer different between the central portion and the outer peripheral portion of the wafer.

For example, Japanese Patent Laid-Open No. 7-249586 discloses that the pressure of the cooling gas supplied between the wafer and the mounting table is made different between the central portion and the outer peripheral portion of the wafer.
This method utilizes the fact that when the pressure of the cooling gas is increased, the heat transfer coefficient between the wafer and the mounting table is increased, so that the wafer in the region where the cooling gas pressure is high is more effective than the wafer in the region where the cooling gas pressure is low. Can be cooled.

In Japanese Unexamined Patent Publication No. 8-45909, a mounting table is divided into a plurality of blocks, and a plurality of heat exchangers are supplied with refrigerants having different temperatures for each of the divided blocks. It is shown that the in-plane temperatures of the arranged wafers are made different. in this way,
Since the pressure of the cooling gas supplied between the wafer and the mounting table is almost the same across the front surface of the wafer, the in-plane temperature distribution of the wafer is determined by the temperature of the refrigerant supplied to the mounting table and the arrangement of the refrigerant passages formed in the mounting table. To be done.

[0006]

[Patent Document 1] Japanese Patent Application Laid-Open No. 7-24958
In the plasma processing apparatus of the type in which the pressure of the cooling gas supplied between the wafer and the mounting table is different between the central portion and the outer peripheral portion of the wafer as disclosed in Japanese Patent No. 6, the wafer and the mounting table directly contact with each other. The portions where the cooling gas penetrates between the mounting tables are each configured in a predetermined pattern. Further, the pressure of the cooling gas is several hundreds to several thousands Pascal, and the thermal conductivity of the portion into which this gas penetrates tends to be saturated as the gas pressure increases.

Therefore, when the pressure of the cooling gas is changed, the wafer in the region where the cooling gas pressure is high is macroscopically
The wafer can be cooled more effectively than the wafer in the region where the cooling gas pressure is low. However, since the rate of change in thermal conductivity differs between the portion where the wafer directly contacts the mounting table and the portion where the cooling gas penetrates between the wafer and the mounting table, microscopic temperature variations based on the pattern increase. Further, there may be a case where the temperature of the wafer suddenly changes due to the stepwise pressure difference near the boundary between the central portion and the outer peripheral portion.

Further, the plasma processing apparatus disclosed in Japanese Unexamined Patent Publication No. 8-45909, in which the mounting table is divided into a plurality of blocks and a plurality of heat exchangers supply refrigerants having different temperatures to each of the divided blocks. Then, multiple external coolers are required. In this case, the heat exchange amount of each cooler can be reduced, but the flow rate cannot be reduced in order to keep the inlet / outlet temperature of the refrigerant constant. For this reason, the heat capacity of the entire system including the external cooler increases, resulting in a system with poor responsiveness. Further, since the piping connecting the mounting table and the external cooler increases, heat loss increases.

The present invention has been made in view of the above problems, and provides a plasma processing apparatus capable of controlling the temperature distribution of a mounting table in a short time and with high accuracy.

[0010]

The present invention adopts the following means in order to solve the above problems.

A plasma generating means for generating plasma in the vacuum processing chamber, a mounting table on which an object to be processed such as a semiconductor wafer is mounted and a plurality of refrigerant passages therein, and the plurality of refrigerant passages are sequentially arranged. In a plasma processing apparatus having a first heat exchanger that supplies a refrigerant to a circulation channel formed by connection, and a control unit that controls the temperature of the mounting table, the control unit is formed on the mounting table. The temperature distribution of the cutting table is controlled by controlling the heat exchange amount of the second heat exchanger that transfers heat between the inlet and outlet of the refrigerant flow path.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to FIGS. FIG. 1 is a diagram showing a plasma processing apparatus according to an embodiment of the present invention. In the figure,
Reference numeral 1 is an integrated mounting table, 2 to 4 are concentric refrigerant passages, 21 and 22 are inlets and outlets of the refrigerant passage 2, 31 and 32 are inlets and outlets of the refrigerant passage 3, 41 and 42, respectively. Is an inlet and an outlet of the refrigerant passage 4, 5 is a first heat exchanger installed outside, 6 is a pipe connecting the first exchanger 5 and the inlet 21, and 7 is a pipe connecting the outlet 22 and the inlet 31. , 8 is a pipe connecting the outlet 32 and the inlet 41, and 9 is a pipe connecting the outlet 42 and the heat exchanger 5.

A is a second heat exchanger provided between the inlet 21 and the outlet 22 of the refrigerant passage, B is a second heat exchanger provided between the inlet 31 and the outlet 32 of the refrigerant passage, and C is a refrigerant. It is a second heat exchanger provided between the inlet 41 and the outlet 42 of the flow passage, and the second heat exchangers A, B, C exchange heat between the inlet and outlet of each refrigerant flow passage. Reference numeral 10 is an object to be processed such as a semiconductor wafer mounted on the mounting table, and 11 is a cooling gas supplied between the mounting table 1 and the processing object 11. The heat exchange amounts of the first heat exchanger 5 and the second heat exchangers A, B, C are controlled by a controller (not shown).

FIG. 2 illustrates the temperature characteristics of the plasma processing apparatus.
FIG. In the figure, Q₁, Q_Two, Q_ThreeIs that
Amount of heat input to the refrigerant flow paths 2, 3, 4 Q_A, Q_B, Q
_CIs 2 from the primary side of the second heat exchangers A, B, C, respectively.
It is the amount of heat exchange to the next side. t ₀Is the outlet of the first heat exchanger
Temperature (deg), G is the refrigerant flow rate (Watt / deg)
is there.

[0015]

[Table 1] Table 1 is a table showing the inlet / outlet temperature of each of the second heat exchangers A, B, and C. Also, the second heat exchanger is
If there is no loss in heat exchange from the secondary side to the secondary side, the following equation holds.

(1) When Q _A = Q _B = Q _C = 0 t ₁ = t ₀ + Q ₁ / G (1) t ₂ = t ₀ + (Q ₁ + Q ₂ ) / G = t ₁ + Q ₂ / G (2) t ₃ = t ₀ + (Q _l + Q ₂ + Q ₃ ) / G = t ₂ + Q ₃ / G (3) (2) When Q _A ≠ 0, Q _B ≠ 0, and Q _C ≠ 0 t _{li = t 0 -Q A / G} (4) t lO = t li + Q l / G = t 0 + (Q l -Q A) / G (5) t l = t lO + Q A / G = t 0 + Q _{l / G (6) t 2i} = t l -Q B / G = t 0 + (Q l -Q B) / G (7) t 2O = t 2i + Q 2 / G = t 0 + (Q l + Q 2 _{-Q B) / G (8)} t 2 = t 2O + Q B / G = t 0 + (Q l + Q 2) / G (9) t 3i = t 2 -Q C / G = t 0 + (Q l + _Q 2 _-Q C) / _{(10) t 3O = t 3i} + Q 3 / G = t 0 + (Q l + Q 2 + Q 3 -Q C) / G (11) t 3 = t 3O + Q C / G = t 0 + (Q l + Q 2 + Q ₃ ) / G (12) In the above formulas (1) to (12), formula (1) = (6)
Formula, Formula (2) = Formula (9), Formula (3) = Formula (12).

That is, the temperature of the refrigerant in the pipes 6 to 9 does not change regardless of whether the second heat exchanger is operating. Therefore, the second heat exchanger can be operated to change only the inlet temperature and the outlet temperature of the flow paths 2, 3 and 4 independently of the other flow paths. That is, the second
It is possible to independently change the inlet temperature to each of the flow passages by operating the heat exchanger of 1., and thereby the temperature distribution of the object to be treated 10 can be arbitrarily controlled.

FIG. 3 is a diagram showing an example of temperature control. As shown by the thin line in the figure, when the second heat exchanger is not used, the temperature of the refrigerant rises every time it passes through the refrigerant passage 2 or the refrigerant passage 4. On the other hand, using the second heat exchanger,
As shown by the thick line in the figure, by performing control to increase the inlet temperature of the refrigerant channel 2 by the second heat exchanger A and decrease the inlet temperature of the refrigerant channel 4 by the second heat exchanger C, The inlet temperature of the refrigerant flowing into each refrigerant passage can be controlled to be equal as shown by the broken line in the figure. As a result, it is possible to make the temperatures of the respective refrigerant channels uniform.

FIG. 4 is a diagram showing details of the second heat exchanger. In the figure, 50 is a heat exchange block, 51 is a refrigerant inlet of the heat exchange block 50, 52 is a refrigerant outlet, 60 is a heat exchange block, 61 is a refrigerant inlet of the heat exchange block 60, 62 is a refrigerant outlet, 70 is a Peltier element, etc. Is a heat exchange element formed according to the polarity of the applied voltage. For example, when the voltage is positive, the heat exchange block 50 to the heat exchange block 60
Heat is transferred to the heat exchange block 60, and when the voltage is negative, the heat is transferred from the heat exchange block 60 to the heat exchange block 50. Reference numeral 80 denotes a heat insulating material that thermally insulates the heat exchange blocks 50 and 60 and the heat exchange element 70 from the outside.

The heat exchange blocks 50 and 60 are made of a good heat conductive material such as aluminum and have a medium passage (not shown) formed therein.

Next, the operation of the plasma processing apparatus according to this embodiment will be described. First, when the second heat exchanger is not used, temperature control similar to the conventional one is performed. That is, the refrigerant discharged from the first heat exchanger 5 circulates in the refrigerant passages 2, 3 and 4. As a result, the heat input to the object to be processed is absorbed by the refrigerant via the cooling gas supplied to the mounting table and the gap between the processing object and the mounting table.

The refrigerant passages 2, 3, 4 provided on the mounting table are concentrically provided in a plurality of zones, and the refrigerant passages in each zone are connected in series. Therefore, for example, from the outer peripheral side to the inner peripheral side. When the refrigerant is flown, the temperature of the object to be treated becomes higher on the outlet side than on the refrigerant inlet side, that is, on the mounting table inner peripheral side, even if the heat input distribution is uniform. Since the material of the mounting table is usually a material having a high thermal conductivity such as aluminum, if the mounting table has an integral structure, the temperature difference between the inner circumference and the outer circumference of the mounting table itself does not become extremely large. The temperature distribution becomes gentle even at the boundaries of the zones, and the object to be processed has a high temperature distribution on the inner circumference side and a low temperature distribution on the outer circumference side.

Next, a method for uniformly controlling the temperature of the object to be treated using the second heat exchanger will be described. When the heat transfer area of each zone is set to be equal, the second heat exchanger provided between the inlet and outlet of each zone may be controlled so that the inlet temperature of the refrigerant to each zone becomes equal. In addition,
When the heat transfer area of each zone is different, the temperature of the object to be processed can be made uniform by correcting the heat transfer area.

When the second heat exchanger is used to make the temperature distribution of the object to be treated non-uniform, the inlet temperature of the refrigerant to each zone determined by the first heat exchanger is set to the second temperature. It suffices to correct the temperature distribution so as to obtain the desired temperature distribution using the above heat exchanger.

As described above, according to the present embodiment, there is no sudden change in the temperature of the object to be processed at each zone boundary, and the number of the first heat exchangers installed outside is not increased, and the object to be processed is not increased. The temperature distribution can be controlled. Further, in the above description, the refrigerant flow path inside the mounting table 1 is divided into three and three second heat exchangers are used, but the number of the second heat exchangers may be reduced if necessary. You can Further, when the refrigerant passage is divided into two, the second heat exchanger may be provided only between the inlet and outlet of any of the refrigerant passages. Further, the circulation direction of the refrigerant of the first heat exchanger and the connection order of the refrigerant passages inside the mounting table may be arbitrarily selected according to the heat input condition to the mounting table and the like.

The mounting table of the plasma processing apparatus is usually placed in a vacuum processing chamber. For this reason, it is desirable that the second heat exchanger is arranged in the vacuum processing chamber where it is easy to shield the heat from the outside, but it can be installed in the atmosphere. Further, when the amount of heat exchanged by the second heat exchanger is small, it can be incorporated in the mounting table.

In the above embodiment, the temperature distribution control of the object to be treated has been described. However, by using the second heat exchanger as a heat exchanger capable of rapid heating or rapid cooling, the second heat exchanger can be used. The exchanger can be used alone or in conjunction with the first heat exchanger to rapidly heat or cool the mounting table. In this case, the heat capacity of the second heat exchanger is made significantly smaller than the heat capacity of the entire first heat exchanger, and the time constant of the temperature change of the mounting table is also made significantly small. This allows the temperature of the mounting table to be changed rapidly. When processing a multilayer film during etching or film formation, there are cases where it is preferable to change the processing temperature rapidly in terms of processing characteristics. This processing method is for controlling the mounting table temperature in such a case. Is effective for.

[0028]

As described above, according to the present invention, it is possible to provide the plasma processing apparatus capable of controlling the temperature distribution of the mounting table in a short time and with high accuracy.

[Brief description of drawings]

FIG. 1 is a diagram showing a plasma processing apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating temperature characteristics of a plasma processing apparatus.

FIG. 3 is a diagram illustrating an example of temperature control.

FIG. 4 is a diagram showing details of a second heat exchanger.

[Explanation of symbols]

1 Stable 2, 3, 4, refrigerant passage 5 First heat exchanger 6,7,8,9 piping 10 Processing object 11 cooling gas 12 Cooling gas 21, 31, 41 Refrigerant flow path entrance 22, 32, 42 Refrigerant flow path outlet 50,60 heat exchange block 51,61 Refrigerant inlet 52,62 Refrigerant outlet A, B, C Second heat exchanger

─────────────────────────────────────────────────── ─── Continuation of front page (56) Reference JP-A-2002-76103 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01L 21/205 H01L 21/3065 H01L 21/68

Claims (4)

(57) [Claims] 1. A plasma generating means for generating plasma in a vacuum processing chamber, a mounting table on which an object to be processed such as a semiconductor wafer is mounted and which has a plurality of refrigerant channels therein, and the plurality of refrigerant channels. In a plasma processing apparatus having a first heat exchanger that supplies a refrigerant to a circulation flow path formed by sequentially connecting the two, and a control unit that controls the temperature of the mounting table, the control unit is provided on the mounting table. A plasma processing apparatus comprising: a second heat exchanger for exchanging heat between the formed inlet and outlet of the refrigerant channel. 2. The apparatus according to claim 1, wherein the mounting table includes an electrostatic adsorption chuck that electrostatically adsorbs the object to be processed and a gas supply path that supplies a cooling gas between the mounting table and the object to be processed. A plasma processing apparatus characterized by the above. 3. The plasma processing apparatus according to claim 1, wherein the second heat exchanger is a Peltier element. 4. The plasma processing apparatus according to claim 1, wherein the second heat exchanger is provided in a vacuum processing chamber.