JPH0917773A - Dry etching apparatus - Google Patents

Abstract

PURPOSE: To obtain a dry etching apparatus by which the leak of cooling gas is detected in advance so as not to raise the temperature of a wafer and which prevents the defect of an etching pattern from being generated. CONSTITUTION: A pressure gage 1 is installed to detect the pressure of the cooling gas supplied to the rear of a wafer 8 and in contact with the wafer. The pressure dropped due to the leak of the cooling gas from the wafer 8 is preset. The pressure of the cooling gas is compared with the dropped pressure before an etching operation is started, and whether the gas leaks or not is judged surely.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dry etching apparatus for etching a semiconductor wafer, and more particularly to a dry etching apparatus having a temperature control mechanism for controlling the temperature of the semiconductor wafer.

[0002]

2. Description of the Related Art Conventionally, this type of dry etching apparatus has a chamber in which an etching gas is introduced and decompressed, a stage arranged in the chamber for holding a semiconductor wafer (hereinafter simply referred to as a wafer), and an aspect ratio. In order to improve the temperature, a temperature control mechanism for controlling the temperature of the wafer is provided.

In the wafer etching operation by this dry etching apparatus, first, the wafer is placed on a stage and held by a mechanical clamp or electrostatic force. Next, the chamber is evacuated to a high vacuum, and then an etching gas is introduced to maintain a constant pressure. Then, for example, the ECR plasma is generated by the introduction of microwaves, and the wafer is subjected to conductive heating and contact with a cooling gas supplied from below the stage to keep the temperature of the wafer constant and perform etching.

As described above, in this dry etching apparatus, the etching gas pressure is controlled and the temperature of the wafer is strictly controlled so that the etching pattern accuracy of the wafer can be stably obtained.

[0005]

However, in the above-mentioned conventional dry etching apparatus, cooling gas often leaks due to uncertain holding of the wafer on the stage. The leakage of this gas lowers the cooling capacity, and the temperature of the wafer rises due to one-sided heating of the heater. When the etching is performed in this state, there are problems that the lateral etching of the wafer is promoted and the etching pattern is destroyed, and the resist adhered to the wafer is burned due to the high temperature.

On the other hand, although the apparatus is provided with a thermocouple for detecting such a temperature rise, the thermocouple is not in direct contact with the wafer for measurement, but is arranged in the stage portion near the wafer. Therefore, even if the temperature of the wafer rises, it takes a long time to transmit the thermocouple to the thermocouple, and it is delayed to turn off the heater. As a result, etching progressed during that time, and it was not possible to prevent the above-described poor pattern accuracy.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a dry etching apparatus which detects a cooling gas leak which causes a rise in temperature of a wafer in advance and does not cause an etching pattern defect.

[0008]

A feature of the present invention is that a stage for holding a semiconductor wafer stored in a depressurized chamber into which a processing gas is introduced, and a constant flow rate of gas from below the stage are supplied. In a dry etching apparatus provided with a cooling mechanism for contacting the back surface of a semiconductor wafer and cooling the semiconductor wafer, a pressure gauge for measuring the pressure rise of the gas by supply and a pressure value measured by the pressure gauge are lower than a specified value. The dry etching apparatus is provided with an interlocking means for stopping the start of the etching operation.

Further, it is desirable to provide a memory device for storing a plurality of the specified values according to the thickness or the back surface state of the semiconductor wafer.

[0010]

Next, the present invention will be described with reference to the drawings.

FIG. 1 is a diagram showing a wafer cooling mechanism in an embodiment of the dry etching apparatus of the present invention. As shown in FIG. 1, this dry etching apparatus includes a pressure gauge 1 for measuring the pressure of a cooling gas supplied to a space 7 on the back surface of a wafer 8 on a stage 5 arranged in a chamber 6,
The pressure value of the space 7 measured by the pressure gauge 1 is input and compared with a specified value stored in the setting unit 3, and when it is lower than the specified value, an interlock signal for stopping the etching start operation is output to the controller 4. And a comparison calculation unit 2.

Although not shown in the drawing, the heater and thermocouple of the temperature control mechanism including this cooling mechanism are incorporated in the stage 5. Further, a pressure regulator provided with a relief valve is provided in the pipe on the supply device side so that the pressure of the cooling gas in the space 7 does not rise abnormally.

Next, the operation of this dry etching apparatus will be described. First, the wafer 8 is held on the stage 5.
Next, the chamber 6 is evacuated and the temperature control mechanism is operated to bring the chamber 6 to a high vacuum to raise the temperature of the wafer 8. Next, when the chamber 6 reaches a high vacuum, the etching gas is introduced into the chamber 6 while being evacuated to maintain a constant pressure. If the measured value of the pressure gauge 1 is equal to or greater than the specified value, the controller 4 does not output a signal from the comparison operation unit 2 and the sequence operation of the apparatus by the controller 4 proceeds as it is to start etching.

Further, when the holding of the wafer 8 is insufficient and the cooling gas leaks from the gap between the wafer 8 and the stage 5, the pressure in the space 7 decreases and the pressure is lower than the specified value stored in the memory 3. A signal is output from the computing unit 2 and the controller 4
The operation of the sequence controller is stopped and etching is not started. In this case, the introduction of gas is stopped, the chamber 6 is returned to the atmosphere, the wafer 6 is attached to the stage 5 again, and the chamber 6 is evacuated.

As described above, if the check operation for the presence or absence of the gas pressure drop before the start of etching is provided as an interlock for the sequence operation, pattern failure due to gas leakage can be prevented in advance.

FIG. 2 is a view showing a wafer cooling mechanism in another embodiment of the dry etching apparatus of the present invention. Normally, a wafer is completed through several hundreds of steps before it becomes a final semiconductor chip. Therefore, when compared with the wafer in the initial process, the wafer in the intermediate process, and the wafer in the final process, there are differences in thickness and back surface state. If there is such a difference, it becomes difficult to accurately detect the presence / absence of an actual gas leak if there is one specified value as in the above-described embodiment. Therefore, the dry etching apparatus of this embodiment can be applied to wafers of different types.

Now, taking only the case where the thicknesses are different, the wafer in the initial step has few films deposited, the thinnest and the rigidity is low, and the wafer in the final step is repeatedly formed. It is thick and has high rigidity. On the other hand, the wafer in the middle stage process is intermediate between the wafers in the initial stage and those in the final stage.

Therefore, when the wafer 8 is normally clamped on the stage 5, the wafer 8 is moved by the pressure difference between the gas pressure in the chamber 6 and the pressure in the space 7 to form the wafer 8a indicated by the chain line in FIG.
Paying attention to such deformation, the differential pressure corresponding to the degree of deformation at which leakage starts to occur is obtained and set to a specified value. For example, if the wafer in the initial process is 4 Torr, 4 Torr is stored in one register of the memory unit 3a, 6 Torr is stored in the middle stage wafer of 6 Torr, and 8 Torr is stored in the other register of the memory unit 3a. For example, it is set in the other register of the memory section 3a.

If the specified pressure values thus set are stored in the memory section 3a, when the respective wafers 8 are fixed to the stage 5, if the respective pressures are equal to or lower than the specified values, there is a leak. Can be confirmed. In addition, depending on the pre-process, the state of the back surface and the state of warpage may change, so if you classify this as well and obtain and set the specified values for each type, you can reliably detect the gas leakage from the wafer, Precise patterns can be stably obtained on various types of wafers.

[0020]

As described above, according to the present invention, a pressure gauge for detecting the pressure of the cooling gas supplied to the back surface of the wafer and contacting the wafer is provided, and the pressure value dropped due to the leakage of the cooling gas from the wafer. Is set and the pressure value of the cooling gas and the drop pressure value are compared before starting the etching to reliably judge the presence or absence of gas leakage, thereby stabilizing the wafer temperature without incurring a temperature rise due to gas leakage. There is an effect that a pattern can be formed.

[Brief description of the drawings]

FIG. 1 is a diagram showing a wafer cooling mechanism in an embodiment of a dry etching apparatus of the present invention.

FIG. 2 is a diagram showing a wafer cooling mechanism in another embodiment of the dry etching apparatus of the present invention.

[Explanation of symbols]

 1 Pressure gauge 2 Comparison calculation part 3 Setting part 3a Memory part 4 Controller 5 Stage 6 Chamber 7 Space part 8 Wafer

Claims (2)

[Claims] 1. A stage for holding a semiconductor wafer accommodated in a chamber in which a processing gas is introduced and decompressed, and a gas of a constant flow rate is supplied from below the stage to bring the gas into contact with the back surface of the semiconductor wafer. In a dry etching apparatus provided with a cooling mechanism for cooling the gas, a pressure gauge for measuring the pressure rise of the gas by supply, and an interface for stopping the etching operation start when the pressure value measured by the pressure gauge becomes lower than a specified value. A dry etching apparatus comprising: a locking unit. 2. The dry etching apparatus according to claim 1, further comprising a memory device that stores a plurality of the specified values according to a thickness or a back surface state of the semiconductor wafer.