JPH09162176A - Plasma processing system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a plasma processing system for a single wafer dry etcher having enhanced yield of processing. SOLUTION: A sheet heater 28 is provided on a cooling table 12 for setting a wafer 24 to be processed in a processing chamber 10A and a lamp heater 32 is disposed above the wafer 24 through a transparent plate 30. Cooling agent of 10 deg.C is circulated constantly through the cooling table 12 by means of a temperature regulator 20 thus sustaining the temperature at point A at a constant level. When the wafer 2 is etched using plasma and gas, temperature at point B becomes 20 deg.C or thereabout and a heating control section 34 controls the heaters 28, 32 such that the temperature at point B becomes 20 deg.C even during the waiting time. The heater 32 may be eliminated.

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 such as a single-wafer dry etcher, and in particular, it is intended to improve a processing yield by providing a heating means for heating a wafer cooling table during a processing standby. .

[0002]

2. Description of the Related Art Conventionally, as a single-wafer dry etcher,
The one shown in FIG. 5 has been proposed.

The processing chamber 10A has a conductive container 10 which also functions as an anode electrode, a conductive cooling table 12 which is provided in the container 10 and also functions as a cathode electrode, and a cooling table 12 thereof.
And an annular insulator 14 provided so as to electrically insulate the container 10 from the container 10 so as to surround the lower opening 10L of the container 10.

While the container 10 is grounded, a high frequency power supply 16 is connected to the cooling table 12 via a matching circuit 18.

The cooling table 12 is provided with a circulation path 12a for circulating a coolant. In the circuit 12a,
The coolant is supplied from the temperature control device 20 through the pipe 22A, and the coolant that has passed through the circulation path 12a returns to the temperature control device 20 through the pipe 22B. The temperature control device 20 constantly cools the cooling table 12 by controlling the temperature of the coolant to be constant (for example, 10 [° C.]).

In the dry etching process, a wafer to be processed 24 such as a semiconductor wafer is placed on the upper surface of the cooling table 12 and fixed by a clamp 26. Then, after the etching gas is introduced into the processing chamber 10A from the gas inlet IN, plasma discharge is generated by the high frequency power from the high frequency power source 16 to perform the dry etching process.

After that, the gas in the processing chamber 10A is exhausted from the exhaust port OUT. Then, the clamp 26 is removed and the processed wafer 24 is taken out from the processing chamber 10A. After that, the series of steps from the wafer set to the wafer removal can be applied to other wafers. By repeating such processing for each wafer, a large number of wafers can be continuously processed.

[0008]

According to the above-mentioned conventional technique, since a large amount of heat is generated during the etching process, the wafer 2
The temperature of No. 4 is rising, and a temperature gradient is generated from the wafer mounting surface to the circulation path 12a even in the cooling table.

When a large number of wafers are continuously processed, equilibrium is achieved with a temperature gradient on the cooling table. Therefore, cooling conditions are set so that optimum etching can be performed in the equilibrium processing. Often. However, during the processing standby such as the start of the operation of the etcher or the end of the continuous processing, there is no heat source other than the cooling, so that the cooling table 12 is sufficiently cooled and the temperature gradient disappears.

FIG. 6 shows a portion B near the surface on which the wafer 24 is set on the cooling table 12 and a portion A near the circulation path 12a.
It is shown that a thermocouple is provided in and to measure the temperature. Although the cooling table 12 is in a standing state as shown in FIG. 5, it is shown in a state of being laid sideways in FIG. 6 for convenience. x is
The distance from the bottom surface of the cooling table 12 to the wafer mounting surface is shown.

FIG. 7 shows a state in which the cooling table 12 is sufficiently cooled during the processing standby. The temperatures T _A and T _{B at} points _A and _B are both cooling temperatures T _O (for example, 10 [° C.]). ), There is no temperature gradient. In contrast, in the continuous process, the temperature T _B is the cooling temperature T of the point B as shown in FIG. 8
Higher than the temperature T _{A O} and the point A, the temperature gradient is generated.

FIG. 9 shows the processing steps for each wafer when the wafers numbered 1 to 5 are continuously processed. GS is an etching gas introduction step, and RF is an etching step by applying high frequency power. , VAC represent the exhaust steps, respectively. FIG. 10 shows changes in the wafer temperature for each wafer in the process of FIG. 9 and 10, t indicates time, and t
_c indicates the wafer transfer time from the start of the removal of a certain wafer to the end of the setting of the next wafer.

At the start of the operation of the etcher, there is no temperature gradient in the cooling table 12 as shown in FIG.
As shown in 0, the smaller the number among the wafers numbered 1 to 4, the lower the wafer temperature during etching and the greater the temperature fluctuation. In such a wafer, a desired etching shape cannot be obtained, and it is often difficult to remove residues, which causes a decrease in yield.

In order to deal with such a situation, it has been proposed to flow several wafers as dummy wafers from the start of operation until the wafer temperature stabilizes. But,
In this way, the wafer material is unavoidably wasted.

An object of the present invention is to provide a novel plasma processing apparatus which can improve the processing yield.

[0016]

A plasma processing apparatus according to the present invention is a plasma processing apparatus for performing plasma processing on a wafer to be processed while the wafer to be processed is set on a cooling table in a processing chamber. A cooling means for cooling the cooling table by circulating a cooling agent inside the cooling table during the middle and plasma processing standby; and a heating means for heating the wafer mounting surface of the cooling table during the plasma processing standby. It is a thing.

According to the configuration of the present invention, since the wafer mounting surface of the cooling table is heated during the plasma processing standby, it is possible to reduce the fluctuation of the wafer temperature when the plasma processing is started.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a single-wafer dry etcher according to the present invention. In FIG. 1, the same parts as those in FIG. 5 are designated by the same reference numerals, and detailed description thereof will be omitted.

The feature of the etcher shown in FIG. 1 is that a sheet heater 28 such as a rubber heater is provided on the upper surface of the cooling table 12.
In addition to the above, the lamp heater 32 is provided outside the container 10, and the heaters 28 and 32 are controlled by the heating controller 34.

A wafer to be processed 24 such as a semiconductor wafer is placed on the heater 28, and the cooling table 1 is clamped by a clamp 26.
Fixed to 2.

A transparent plate 30 such as a quartz plate is provided so as to cover the upper opening 10U of the container 10, and a heater 32 is installed so as to heat the wafer 24 via the transparent plate 30.

On the cooling table 12, a portion B near the heater 28
And a portion A near the circulation path 12a are provided with a thermocouple, and the temperature gradient during continuous processing as shown in FIG. 8 is obtained using these thermocouples. That is, for example, five or more wafers are continuously processed under the same dry etching conditions as described later, and when the wafer temperature is stable as in the fourth to fifth wafers shown in FIG. Measure temperatures T _A and T _B at point _B.

The temperature adjusting device 20 is constantly connected to the pipe 22A through the circulation path 12a and the pipe 22B, for example, 10
[° C] The cooling table is cooled by circulating a constant coolant. Therefore, the temperature T A at the point _A is, for example, a temperature close to 10 ° C. as shown in FIG. On the other hand, the temperature at the point B is, for example, 20 [° C.] due to heat generated by the sequential etching process. The temperature T thus measured
_A, T _B is stored in memory in the heating control unit 34 as the target temperature to form a temperature gradient as shown in FIG.

The temperature measurement as described above may be performed at least once for the etcher of FIG. 1, and in the etching process after the measurement, the temperature control can be performed based on the stored temperature data. It is also possible to perform temperature control using temperature data measured by another etcher of the same kind as the dry etcher of FIG.

The etching process is performed for each wafer in steps as shown in FIG. FIG. 3 shows a heating sequence by the heaters 28 and 32 associated with the processing of FIG.
Shows a change in wafer temperature accompanying the processing of FIG. Figure 2
4, the same symbols as those in FIGS. 9 and 10 mean the same items as described above. 3, the vertical axis represents the heating amount [kcal / sec], H is a relatively high heating amount by the heater 28, M is a relatively low heating amount by the heater 28, and L is the heater 32. Each heating amount lower than M is shown.

When the operation of the etcher shown in FIG. 1 is started, the cooling table 12 is cooled by the temperature controller 20 and the wafer is placed on the cooling table 12 with the heating amount H by the heater 28 as shown in FIG. The surface is heated. At this time, the heating control unit 34 controls the heater 28 so that the temperatures at points A and B become substantially equal to the temperatures T _A and T _B stored in the memory, respectively. As a result, in the cooling table 12, a temperature gradient that is similar to or coincides with that during continuous processing is formed.

Next, the first wafer is processed according to the processing steps of FIG. That is, the first wafer is placed on the heater 28 and fixed to the cooling table 12 by the clamp 26. Then, at the same time when the heater 28 is turned off, the gas introduction step GS is started and the etching gas is introduced into the processing chamber 10A from the gas introduction port IN. The etching gas is, for example, CF ₄ / CHF ₃ / Ar = 5/30
/ 60 [sccm] is introduced. While the etching gas is being introduced, the wafer 24 is heated with the heating amount L by the heater 32 as shown in FIG. Heating amount L of the heater 32 at this time
Are determined to maintain the temperature gradient created by the heater 28.

After that, the heater 32 is turned off and the etching step RF is started at the same time. That is, the container 10 is fed from the high frequency power source 16 through the matching circuit 18.
High-frequency power is supplied to the (anode electrode) and the cooling table 12 (cathode electrode) to generate plasma discharge in the processing chamber 10A, so that the wafer 24 is etched. In this etching process, as an example, the high frequency power is set to 700 [W] and the pressure in the processing chamber 10A is set to 160.
It can be [mTorr]. During the etching process, both the heaters 28 and 32 are off.

After the etching process is completed, the exhaust step V
AC is started, and at the same time, as shown in FIG.
8 is operated with heating amount M. The heating amount M is determined so as to form a temperature gradient that is similar or coincident with that during the continuous processing. In the exhaust step VAC, the gas in the processing chamber 10A is exhausted from the exhaust port OUT.

When the exhaust step VAC is completed, the clamp 2
6 is removed and the wafer 24 is taken out. Then, after the wafer transfer time t _c , the second wafer is set on the cooling table 12 via the heater 28 in the same manner as the previous time.

Thereafter, the gas introduction step GS is started for the second wafer, and at the same time, the heater 28 is turned off and the heater 32 is operated at the heating amount L. Then, when the gas introduction step GS ends, the heater 32 is turned off and the etching step RF is performed in the same manner as the previous time.

When the etching step RF is finished, the exhaust step VAC is started, and at the same time, the heater 28 is operated with the heating amount M. After that, the above steps GS, RF, VAC and heating control are repeated for each of the third and subsequent wafers.

FIG. 4 shows a change in the wafer temperature due to the above-mentioned processing. T _O is a cooling temperature (for example, 10 ° C.).
[° C.]). It can be seen from FIG. 4 that the wafer temperature varies little from the first wafer. Further, comparing FIG. 4 and FIG. 10, in the case of FIG. 4 according to the present invention, the wafer temperature at the start of etching is higher for the first to third wafers, and there is less fluctuation in the wafer temperature during etching. Recognize.

According to the above embodiment, the cooling table 12
Has a temperature gradient that is similar to or coincides with that during the etching process even when the etching process is on standby, and therefore the fluctuation of the wafer temperature at the time of shifting to the etching process is extremely small. Therefore, variations in etching shape are reduced, residue removal is facilitated, and the yield of etching processing can be significantly improved.

Further, as shown in FIG. 4, since the etching process is performed on the first wafer under stable temperature conditions, it is not necessary to flow the dummy wafer.

The present invention is not limited to the above-described embodiment, but can be implemented in various modified forms. For example, the following changes (1) to (3) are possible.

(1) The heater 28 may be embedded in the upper surface of the cooling table 12.

(2) The heater 32 may be provided in the processing chamber 10A. In some cases, the heater 32 may be omitted, and the heater 28 may generate a heating amount corresponding to the heating amount L of the heater 32 in FIG.

(3) The present invention can be applied not only to the etching process using plasma but also to the film forming process using plasma.

[0040]

As described above, according to the present invention, since the heating means for heating the wafer mounting surface of the cooling table in the processing chamber during the plasma processing standby is provided, the wafer temperature at the time of the plasma processing is changed. Can be reduced, the processing yield can be improved, and the use of dummy wafers can be avoided.

Further, when a temperature gradient similar to or coincident with that during plasma processing is formed on the cooling table while waiting for plasma processing, there is an effect that fluctuation of the wafer temperature at the time of shifting to plasma processing can be minimized.

Furthermore, providing an auxiliary heating means for heating the wafer on the cooling table while waiting for the plasma processing has the effect of enabling more precise wafer temperature control.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a single-wafer dry etcher according to the present invention.

2 is a time chart showing processing steps for each wafer in the apparatus of FIG. 1. FIG.

3 is a time chart showing a heating sequence in the apparatus of FIG.

FIG. 4 is a time chart showing changes in wafer temperature in the apparatus of FIG.

FIG. 5 is a sectional view showing a conventional single-wafer dry etcher.

FIG. 6 is a cross-sectional view showing a state in which the cooling table of the apparatus of FIG. 5 is laid sideways.

FIG. 7 is a graph showing a temperature distribution of the cooling table in FIG. 6 during standby for processing.

8 is a graph showing a temperature distribution of the cooling table in FIG. 6 during continuous processing.

9 is a time chart showing processing steps for each wafer in the apparatus of FIG.

10 is a time chart showing changes in wafer temperature in the apparatus of FIG.

[Explanation of symbols]

10: container, 10A: processing chamber, 12: cooling stand, 14: insulator, 16: high frequency power supply, 18: matching circuit, 2
0: temperature control device, 22A, 22B: piping, 24: wafer to be processed, 26: clamp, 28: sheet heater, 3
0: transparent plate, 32: lamp heater, 34: heating controller.

Claims (4)

[Claims] 1. A plasma processing apparatus for subjecting a wafer to be processed to plasma processing in a state where the wafer to be processed is set on a cooling table in a processing chamber, wherein the inside of the cooling table is provided during plasma processing and during standby for plasma processing. A plasma processing apparatus comprising: a cooling unit that circulates a cooling agent to cool the cooling table; and a heating unit that heats a wafer mounting surface of the cooling table while waiting for plasma processing. 2. The control means for controlling the heating means so that a temperature gradient close to or coincident with a temperature gradient generated during plasma processing is generated on the cooling table in the cooling table while waiting for plasma processing. 1. The plasma processing apparatus according to 1. 3. The plasma processing apparatus according to claim 1, further comprising auxiliary heating means for heating the wafer to be processed on the cooling table while the plasma processing is on standby. 4. The plasma processing apparatus according to claim 3, wherein the control means is configured to control the heating means and the auxiliary heating means so that the approximate or coincident temperature gradient is generated.