JPH02135753A - Sample holding device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] Ll. The present invention relates to a sample holding device, and more particularly to a sample holding device such as an electrostatic chuck that uses electrostatic adsorption to attract and hold a sample, and in particular, in the manufacture of semiconductor integrated circuits.
The present invention relates to a sample holding device used when holding a sample by suction under high vacuum.

For example, electron cyclotron resonance (Electron resonance)
C V D (Chem
ical Vaper Dep.

In a semiconductor integrated circuit manufacturing apparatus such as a dry etching apparatus that forms a fine circuit pattern on the surface of a sample, the sample is
Electrostatic chuck-type sample holding devices that utilize electrostatic adsorption force are widely used to hold samples in processing chambers maintained in a high vacuum state.

A conventional sample holding device of this type has a structure as shown in FIG. That is, a sample stage IJ is placed on a base 1O, and a flow path 12 for circulating a cooling liquid is formed in this sample stage 11. An inlet pipe 13 and an outlet pipe 14 are connected to the flow path 12, and the cooling liquid is configured to be discharged from the inlet pipe 13, through the flow path 12, and out of the outlet pipe 14. An electrode 15 is placed above the sample stage 11 via a heat transfer member 16 such as silicone rubber, and a sample 17 is placed on top of this electrode 15. The electrode 15 is formed with an electrode layer 19 embedded inside an insulator 18 made of, for example, ceramic. 20 are connected.

[Base 10 and sample stage] An insulating tube 21 is interposed in the portion of the base 1 through which the electrode rod 20 is passed.

The electrode 15 is fixed to the sample stage 11 by joining a flange portion 22 formed on the lower outer peripheral surface of the electrode 15 and a flange portion 24 formed on the upper inner peripheral surface of the electrode layer 23.
This is done by bolting the electrode layer 23 to the sample stage 11 (not shown).

In the sample holding device configured as described above, in order to adsorb and hold the sample 17, which is an object to be adsorbed, the electrode rod 20 is connected to a power source (not shown), and the sample 17 is connected to the electrode 15.
The surface of the sample 17 is irradiated with plasma in order to perform a film forming process or an etching process. Due to this plasma irradiation, the electrode 15 is charged positively or negatively, while the sample 17 is grounded through the plasma. As a result, an electrostatic force is generated between the sample 17 and the electrode 15, and the sample 17 is grounded through the plasma.
is attracted and held on the surface of the insulator 18 by this electrostatic force.

In this way, the temperature of the sample 17 that is attracted and held by the electrode 15 due to plasma irradiation is unavoidably increased due to the influence of the plasma, but if this temperature increase is excessive, the growth of the sample 17 The film or etching will be inhibited. Controlling this temperature rise is becoming an essential element in the production of future ultra-fine LSIs.

Therefore, in the past, in order to control the temperature of the sample 17, the sample stage 11 was cooled by injecting water or antifreeze from the inlet pipe 13, passing through the channel 12, and discharging it from the outlet pipe 14. Furthermore, a heat transfer body 16 made of silicone rubber or the like is interposed between the electrode 15 and the sample stage 11 in an attempt to increase the contact heat transfer area, which is extremely small when contact between rigid bodies.

However, in the conventional sample holding device as mentioned above, although heat transfer between the sample stage 11 and the electrodes 15 is carried out through a good heat transfer body 16, it is still difficult to conduct heat transfer between solids. Since there is a limit to the increase in the heat transfer contact area, the sample stage 11
There was a limit to the cooling of the electrode 15 due to the cooling of the electrode 15. This limit in temperature control has caused a limit to the etching rate, etc., which are associated with higher integration and miniaturization of ultra-LSIs, for example.

The present invention was invented in view of the above problems, and provides a sample holding device that can reliably and easily maintain and control the temperature of a sample placed on an electrode at a low temperature. The purpose is to facilitate the progress of miniaturization.

Steps for Solving the Problems In order to achieve the above-mentioned objects, the sample holding device according to the present invention includes a sample stage having a flow path into which a cooling medium is introduced, and an insulator or A voltage is applied between the electrode and a sample in contact with the surface of the electrode, and the electrostatic force generated between the insulator and the sample causes the sample to An electrostatic chuck type sample holding device that is attracted onto an electrode, characterized in that a gas introduction part for introducing gas is formed between the sample stage and the electrode, and the above sample holding device , on the top surface of the electrode.

It is characterized in that a gas introduction part for introducing gas is formed between the sample and the electrode, and a flow path into which a cooling medium is introduced is formed inside the electrode, while the electrode has a
It is characterized in that a gas introduction part is formed between the sample and the electrode to introduce gas.

1. According to the above configuration, heat transfer between the sample stage and the electrodes is not carried out via a heat transfer body such as silicone rubber, but is carried out via a gas fluid with extremely high conductivity. Na ^
The Rukoto.

That is, the thermal conductivity of gas in the free molecular region is extremely high (for example, λ, for example, helium gas + 3 Torr 1830 W -
cm-"-'C-', 0 in silicone rubber
, 24 W = cm-2·'C-' is an incomparably high value.

In addition, if a gas introduction part is formed on the top surface of the electrode to introduce gas between the sample and the electrode, heat transfer will occur not only between the sample stage and the electrode but also between the electrode and the sample. This can be done through a gas fluid with very high conductivity.

In addition, if a flow path for introducing a cooling medium is formed inside the electrode, and a gas introduction part for introducing gas between the sample and the electrode is formed in the electrode, the sample is placed on the electrode. Since the electrodes are directly cooled by the cooling medium,
Temperature control of the sample can be performed more easily and reliably.

X Onitate Hereinafter, embodiments of the present invention will be described based on the drawings. Note that the same parts as in the prior art are given the same reference numerals.

(A) In FIG. 1, lO is a base, and this base 10
A disk-shaped sample stand 11 is placed on top, and an annular flow path 12 for circulating a cooling liquid is formed inside this sample stand 11. An inlet pipe 13 and an outlet pipe 14 are connected to this flow path 12, and the cooling liquid is supplied to the inlet pipe 13.
The liquid is configured to pass through the flow path 12 and be discharged from the outlet pipe 14. Water or antifreeze is used as the coolant.

An electrode 15 is placed on the upper surface of the sample stage 11 via a spacer 30, and the spacer 30 serves as a gas introduction section 31 for introducing gas between the sample stage 11 and the electrode 15. Space is secured. The gas introducing portion 31 is a groove-shaped gas reservoir with a diameter of, for example, about 10 μm, in which a molecular flow of the gas inserted between the sample stage 11 and the electrode 15 can be formed. As for the type of gas used, any gas other than corrosive gas can be used as long as the gas does not leak, but He, Ar, etc. are convenient for handling. The spacer 30 is formed in a ring shape with an outer peripheral surface that almost matches the outer peripheral surface of the electrode 15, and a gas introduction tube 32 is provided in the gas introduction section 31, passing through the base 10 and the sample stage 11. It is connected. A sufficient seal (not shown) is provided between the sample stage 11, spacer 30, and electrode 15 to prevent gas from leaking.

The electrode 15 is made of, for example, ceramic (A1□0
3), an electrode layer 1 is placed inside the insulator 18 composed of
9 is buried, and this electrode layer 19
An electrode rod 20 is connected to the electrode rod 20 by penetrating the base IO and the sample stage 11. Since the sample 17 is placed on the electrode 15 and is attracted thereto, the upper surface of the electrode 15, which serves as the attraction surface for the sample 17, is polished to obtain a predetermined surface smoothness. In addition, an electrode rod 20 is mounted on the base 10 and the sample stage 11.
An insulating tube 21 is interposed in the portion where the insulating tube 21 is penetrated.

The electrode 15 is fixed to the sample stage i1 by a flange portion 22 formed on the lower outer periphery of the electrode 15 and this flange portion 2.
A flange portion 24 formed on the upper inner periphery of the electrode layer 23 facing the electrode layer 23 is joined to the electrode layer 23, and this electrode layer 23 is bolted to the sample stage 11 (not shown). There is.

In order to adsorb and hold the sample 17, which is an object to be adsorbed, in the sample holding device configured as described above, the electrode rod 20 is connected to a power source (not shown), and the sample 17 is placed on the sample stand.
1 and irradiates the surface of the sample 17 with plasma in order to perform a film forming process or an etching process. As a result of this plasma irradiation, the insulator 18 is positively or negatively charged, while the sample 17 is grounded via the plasma. As a result, an electrostatic force is generated between the sample 17 and the insulator 18, and the sample 17 is This electrostatic force attracts it onto the surface of the insulator 18,
It will be retained.

Furthermore, in the sample holding device of this embodiment, the cooling liquid is circulated through the flow path I2 of the sample stage 11, so that the sample stage 11 is sufficiently cooled, and the heat transfer between the sample stage 11 and the electrodes 15 is This is carried out by gas conduction via gas, and the electrode 15 is efficiently cooled by the sufficiently cooled sample stage 11. In other words, as mentioned in the operation section, the thermal conductivity of gas in the free molecular region is extremely high; for example, helium gas: 3 Torr, 1830 W-c
m-”・℃-1, 0,24 in silicone rubber
This is an incomparably high value compared to W-am-".°C"1.

In addition, by using vacuum technology, we are able to minimize the amount of gas leaks that may affect processes, etc., and no adverse effects have been observed.

Note that in this embodiment, for introducing gas to the electrodes and the sample stage, a gas introduction pipe 3 that passes through the base 10 and the sample stage 11 is used.
Although the example according to No. 2 has been shown, this gas introduction tube may be introduced into the electrode from the side of the electrode without passing through the sample stage 11.

Next, the sample holding device according to the above-described embodiment and the sample stage 11
The results of an experiment using a conventional sample holding device in which silicone rubber was interposed between the electrode 15 and the electrode 15 will be compared.

As an experimental method, the temperature of the sample 17 was raised to 200° C., and then the samples were cooled using each device for comparison. Further, the temperature of the coolant on the inflow side is always adjusted to 10°C.

The temperature change of sample 17 and the temperature change of the cooling liquid on the return side are
As shown in the figure.

According to this experiment, in the case of the present invention in which a gas is interposed between the sample stage 11 and the electrode 15, the cooling time is about half that of the conventional example, and the same effect is obtained. Regarding the temperature change of the circulating coolant on the return side,
In contrast to the conventional case, where almost no change is observed,
In the case of this example, a temperature increase of 5° C. to 10° C. was observed, proving that a sufficient cooling effect was obtained.

In another embodiment, instead of using the spacer 30, an IO
By forming a groove having a depth of about μm, it is also easy to form a gas introduction part between the sample stage 11 and the electrode 15 (not shown).

(B) Next, another embodiment is shown in FIGS. 3 and 4.

In this embodiment, the gas introduction part 35 is formed on the upper surface of the electrode 34, so that the heat transfer efficiency is particularly enhanced between the electrode 34 and the sample 17. The gas introduction part 35 has a depth of 10 μm on the upper surface of the electrode 34, leaving a peripheral part of the upper surface.
It is constructed by forming a groove 36 of about m length.

A gas introduction path 37 that passes through the base 10, the sample stage 11, and the electrode 34 is connected to the gas introduction section 35. The upper surface of the peripheral part of the electrode 34 is configured to be a smooth surface by polishing, and by increasing the smoothness of the peripheral part of the upper surface of the electrode 34 in this way, the upper surface of the electrode 34 and the sample 17
The structure is such that gas can be sealed between the lower surface and the lower surface. Further, the portions of the gas introduction portion 35 other than the portion 36 have a structure that can support the sample 17 and prevent the sample 17 from being deformed.

In this embodiment, a heat transfer body 1 made of silicone rubber or the like is placed between the electrode 34 and the sample stage 11, as in the conventional example.
6 is interposed. The configuration of other parts is similar to that of the above-described embodiment.

The results of experiments conducted in this example are shown below.

The experiment was conducted by filling room temperature helium gas between the silicon wafer, which is the sample 17, and the electrode 34. Silicone rubber, which is a good heat conductor, is interposed between the electrode 34 and the sample stage 11. A fluorescence thermometer was used to measure the wafer temperature.

The plasma conditions are as follows.

Microwave in CV D; 2 kw + gas flow rate: 02 to 1505 CCU, electrostatic chuck voltage: lkV
, Coolant temperature: 10℃, Plasma irradiation time: 6m1
n Figure 5 shows a graph of the results of this experiment.

When no gas is introduced between the electrode 34 and the sample 17, the sample 17, which had a temperature of nearly 200°C, is exposed to H under the same conditions.
It was observed that by introducing e-gas, the temperature was lowered by 100° C. or more when the introduced He gas pressure was 5 Torr. Sample 17 again? Dependency of the M degree on gas pressure was observed, which indicates that the gas acts effectively as a heat transfer medium.

Although not shown, the wafer temperature was investigated by changing the He gas flow rate instead of the He gas pressure, and it was confirmed that the higher the He gas flow rate, the lower the wafer temperature.

As yet another embodiment, a configuration in which gas is also introduced between the sample stage 39 and the electrode 34 is shown in FIGS. 6 and 7. In this embodiment, the groove 41 is A gas introduction section 40 is formed. Also, the electrode presser 4
2 is brought into close contact with the electrode 34 by tight fitting such as shrinkage fitting, and the structure is such that no gas leaks from between the electrode 34 and the electrode holder 42. Furthermore, an O-ring 43 is interposed between the sample stage 39 and the electrode holder 42.
The structure is such that gas does not leak between the sample stage 39 and the electrode holder 42.

In the embodiment with the above configuration, the sample stage 39 and the electrode 3
4 is further improved, and the sample 17 can be cooled more efficiently and easily.

(C) Yet another embodiment is shown in FIGS. 8 and 9.

In this embodiment, the sample stage 45 does not have a flow path for flowing the coolant, but a flow path 47 for flowing the coolant is formed inside the electrode 46. and electrode 46
A gas introduction section 48 consisting of a groove 49 is formed on the upper surface, and a structure in which the sample 17 can be supported in a portion of the gas introduction section 48 other than the groove 49, and the sample 17 is not deformed. It becomes. The depth of this groove 49 is
It is approximately 20 μm, and the area ratio of the groove 49 on the upper surface of the electrode 46 is approximately 40%.

Although not shown in FIG. 8, a flow path for cooling liquid may be provided on the sample stage together with the electrodes.

Further, the structure of the grooves in the electrodes is not the one shown in FIG. 9, but may be formed as shown in FIG. 11.

In FIG. 11, a groove 53 is formed in the electrode 51.
Although an example is shown in which a gas inlet 54 and a gas outlet 55 are connected to the gas inlet 52 connected to the gas inlet 52, it is also possible to seal the gas between the sample and the sample without providing the gas outlet 55. good.

The area ratio of the grooves must be determined taking into account the electrostatic adsorption force, and it is desirable that the groove area be as large as possible within the range that can secure the adsorption force for the sample.The groove pattern should be concentrically symmetrical. It is excellent in terms of uniform cooling.

In the configurations according to the two embodiments described above, the cooling liquid is
6 (Fig. 8) or the inside of the electrode 51 (Fig. 11), and the heat transfer between the electrode 46 (51) and the sample 17 is by gas conduction via gas, which is extremely efficient. 17 is cooling and gaining weight.

The results of an experiment in which the device according to this example was used in a plasma device are shown below.

In the experiment, an electrode 46 with a gas introduction groove was used, a helium gas sample at room temperature, a silicon wafer 417, and an electrode 46.
This was done by enclosing it between the

Plasma conditions Microwave; 1 kw, RF; 40 W, gas flow rate; Ct, l03 (: CM, electrostatic chuck voltage; 80
0v, He gas pressure; 20 Torr, plasma irradiation time: min The experiment was conducted under the above conditions, and compared to when helium gas was not introduced, it was found that the temperature of sample 17 was 200°C or higher when helium gas was not introduced. However, when helium gas was introduced, the temperature dropped to below 50℃, and 1
A temperature difference of 50°C or more was confirmed. Furthermore, by lowering the temperature of the coolant flowing inside the electrode 46, the sample 17
It was confirmed that the temperature also decreased accordingly.

(D) Next, in the case of the embodiment shown in FIG. 1 of the present invention, the case of the embodiment shown in FIG. 3, the case of the embodiment shown in FIG. 6, and the case of the conventional example. The results of an experimental comparison under the same conditions are shown below, and the comparison was made with an increase in wafer temperature from the start of the experiment.

Plasma irradiation conditions 02 flow rate: 1505CCU, microwave: 2kw.

Plasma irradiation time: 6m1n, groove depth: 5-10μm
, Thickness of gas introduction part between sample stage and electrode: 10 μm, Helium gas pressure: 10 Torr, Silicon rubber thickness: 0.
2mm In the case of the embodiment shown in Fig. 1: 29°C In the case of the embodiment shown in Fig. 3; 41°C In the case of the embodiment shown in Fig. 6; 18°C in the case of the conventional example When using silicone rubber as the heating body: 70°C When using vacuum grease as the heat transfer body in the case of the conventional example: 49°C As is clear from the above explanation, the sample according to the present invention The holding device is composed of a sample stage having a flow path into which a cooling medium is introduced, and an electrode whose surface is made of an insulator or at least an insulating layer, and a sample that is in contact with the surface of the electrode. In an electrostatic chuck type sample holding device in which a voltage is applied between the electrode and the sample is attracted onto the electrode by an electrostatic force generated between the insulator and the sample, the sample stage and A gas introduction part for introducing gas between the sample and the electrode is formed, and a gas introduction part for introducing gas between the sample and the electrode is formed on the upper surface of the electrode. In addition, a flow path through which a cooling medium is introduced is formed inside the electrode, and a gas introduction section is formed in the electrode to introduce gas between the sample and the electrode. Conventionally, this was an inefficient heat transfer mechanism with a small heat transfer contact area between a rigid body and an elastic body, but in the case of the present invention, a gas conduction method using gas is used. By doing so,
An extremely efficient heat transfer mechanism can be constructed, and the temperature of the sample placed on the electrode can be easily maintained and controlled at a low temperature. Therefore, for example, higher integration and miniaturization of LSI can be more easily achieved.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view showing an embodiment of the sample holding device according to the present invention, FIG. 2 is a graph showing the relationship between sample temperature and time, and the relationship between return side cooling liquid temperature and time. The figure is a schematic sectional view showing another embodiment, FIG. 4 is a plan view of the apparatus shown in FIG. 3, FIG. 5 is a graph showing the relationship between wafer temperature and helium gas pressure, and FIG. 6 is another embodiment. A schematic sectional view showing an example, FIG. 7 a plan view of the device shown in FIG. 6, FIG. 8 a schematic sectional view showing another embodiment, FIG. 9 a plan view, and FIG. 10 an inflow side cooling fluid A graph showing the relationship between temperature and sample temperature,
FIG. 11 is a plan view showing another embodiment of the electrode, and FIG. 12 is a schematic sectional view showing a conventional example.

Claims (3)

[Claims] (1) Consisting of a sample stage having a flow path into which a cooling medium is introduced, and an electrode whose surface is made of an insulator or at least an insulating layer, the electrode is connected to the sample in contact with the surface of the electrode. In an electrostatic chuck type sample holding device in which a voltage is applied between the sample stage and the electrode, the sample is attracted to the electrode by an electrostatic force generated between the insulator and the sample. A sample holding device characterized in that a gas introduction part for introducing gas is formed between the parts. (2) The sample holding device according to claim 1, wherein a gas introduction portion for introducing gas between the sample and the electrode is formed on the upper surface of the electrode. (3) It is composed of a sample stage and an insulator or an electrode whose surface is made of an insulating layer, and a voltage is applied between the sample in contact with the surface of the electrode and the electrode, and the insulator and the In an electrostatic chuck type sample holding device in which the sample is attracted onto the electrode by an electrostatic force generated between the sample and the sample, a flow path is formed into the electrode through which a cooling medium is introduced, and the sample is attracted to the electrode. A sample holding device characterized in that a gas introduction part for introducing gas between a sample and an electrode is formed.