JPH05251197A - Dry etching method - Google Patents

Abstract

PURPOSE:To provide a dry etching method capable of preventing dust generation between a reverse surface of a base plate and an obverse surface of an electrode at the time of etching in an RF power applying method so as to enhance a yield of a product. CONSTITUTION:Required RF power is divided into a plurality of steps up to a predetermined value at the time of application of the RF power, to be increased. After etching, the RF power is divided into a plurality of steps to be decreased, thus obtaining an RF power applying method for stopping electric discharge.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dry etching method.

[0002]

2. Description of the Related Art In recent years, as semiconductor devices have become higher in performance and cost has been reduced, their patterns have been miniaturized. At this time, the dust attached to the back surface of the substrate has a great influence on the yield.

In order to reduce the cost of semiconductor devices, it is necessary to increase the etching rate and increase the processing capacity of the apparatus.

Therefore, there is a tendency to increase the RF power, but at this time, the rise of the substrate temperature during the etching process of the substrate becomes a problem. In order to solve this, it is necessary to increase the adhesion between the front surface of the electrode and the back surface of the substrate and to efficiently perform heat exchange between the electrode and the substrate.

A conventional dry etching method will be described below. FIG. 3 shows RF of a conventional dry etching method.
A power application method will be described. When the RF power is applied, the set RF power is instantly applied to the electrode, and the supply of the RF power is stopped after the etching is completed. R in Figure 2
The structure of the reaction chamber of the IE dry etching apparatus is shown. 11
Is an upper counter electrode, and an etching gas is supplied from a shower-shaped hole 11a on the lower surface of the electrode. Reference numeral 12 is a lower electrode to which RF is applied, and the inside has a structure in which cooling water flows. The surface thereof is covered with an insulating film 13 such as alumite. The substrate 14 is placed on the lower electrode 12,
The substrate 14 is etched by applying RF power to the substrate. Reference numeral 15 is an elevator unit for transferring the substrate 4, 16 is an insulator between the lower electrode 12 and the etching chamber, 17 is an RF power controller, and 18 is RF.
A substrate 14 showing a power source is placed and RF is applied to the lower electrode 12.
When power is applied, the substrate 14 is charged with static electricity, and due to the action of this static electricity, the substrate 14 moves to the lower electrode 1
The heat exchange between the substrate 14 and the lower electrode 12 is efficiently performed by adhering to the surface of the insulating film 13 on the substrate 2, and the temperature rise of the substrate 14 is suppressed.

[0006]

However, in the above-described conventional dry etching method, when RF power is applied,
A force that causes the substrate 14 to adhere to the lower electrode 12 suddenly occurs,
The back surface of the substrate 14 and the surface of the insulating film 13 on the lower electrode 12 are rubbed to generate dust. Furthermore, since static electricity charged on the substrate 14 is retained as it is even after the RF power is stopped after the etching is completed, the substrate 14 continues to adhere to the lower electrode 12 in such a state.
When the elevator unit 15 for transporting the substrate is operated to transport the substrate, a force is generated around the pin 25 of the substrate elevator unit as shown in FIG. 4, and the rear surface of the substrate 14 and the surface of the insulating film 13 on the lower electrode 12 are processed. Scrape and generate dust. The dust thus generated contaminates the reaction chamber and serves as a dust source for wafers to be processed thereafter, and the dust carried out of the apparatus while being attached to the back surface of the substrate 14 serves as a dust source for the next step. Become. As described above, the conventional RF power application method has a problem that the yield of the device is significantly reduced.

Further, after the etching is completed, the substrate 14 continues to adhere to the lower electrode 12 even after the RF power is stopped, so that the substrate 14 cannot be removed from the lower electrode 12 and a defective conveyance frequently occurs. I also had problems.

The present invention is intended to solve the above-mentioned conventional problems, and reduces the dust generated on the back surface of the substrate 14 and the surface of the insulating film on the lower electrode 12 and can dry the substrate to improve the transport failure. It is an object to provide an etching method.

[0009]

To achieve this object, the dry etching method of the present invention comprises a step of increasing the RF power to a predetermined value by dividing the step into a plurality of steps when applying the RF power, and ending the etching. After that, the process is divided into a plurality of steps to reduce the RF power and stop the discharge.

[0010]

By this method, the substrate does not suddenly adhere to the lower electrode at the start of application of RF power, and dust generated by rubbing the back surface of the substrate and the surface of the insulating film of the lower electrode at that time is reduced. Even after the etching is completed, by gradually reducing the RF power, the charged static electricity is discharged, the contact between the substrate and the lower electrode can be released, and the dust generated when the substrate transfer elevator unit is operated is generated. Will be reduced. Further, at this time, since the substrate and the lower electrode are not brought into close contact with each other, the defective conveyance of the substrate is also improved.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows RF when a SiN film is etched on a wafer by a dry etching apparatus of RIE system.
A power application method will be described. The etching conditions are RF power of 200 W, etching pressure of 400 mTon, etching gas of CF ₄ / O ₂ = 42/8 SCCM, and SiN etching rate of 1500Å / min.

From the start of RF power application, the required power is increased to 200 W in 30 seconds. The amount of increase at that time is 40 W in the first 10 seconds, 100 W in the next 10 seconds, and 200 W in the next 10 seconds. Such an RF power applying method was adopted. Then, etching is performed with RF power of 200 W for 90 seconds, and then discharge is stopped for 40 seconds, but the RF power is divided into four steps of 10 seconds each, and 100 W, 50 W, 20 W, and 0 W are obtained at each step. Set to.

FIG. 3 shows a conventional RF power applying method.
The etching conditions are the same as in the above embodiment. When the RF power was applied, the power was set to 200 W instantaneously, and after 90 seconds of etching, the RF application was stopped.

Table 1 shows a comparison of the number of dusts on the back surface of the wafer between the present invention and the conventional RF power applying method. It is a value measured by a dust counter on the back surface of the 6-inch Si wafer. The results are obtained by etching 5 pieces of dust each having a size of 0.3 μm or more, and the radius of about 2 from the center of the wafer because there was too much dust during the measurement of the conventional example.
Since the memory capacity of the dust counter was exceeded by measuring only in the range of 5 mm, the measurement result of the conventional example in (Table 1) shows the measured value in the range of 25 mm radius and the converted value on a 6-inch wafer. ..

[0016]

[Table 1]

Thus, the backside dust of the wafer was significantly reduced. Also, with the conventional RF power application method,
At the same time, the wafer transfer failure due to the fact that the contact between the wafer and the electrode was maintained after the etching was completed was also improved.

[0018]

As described above, according to the present invention, when the RF power is applied, the method is divided into a plurality of steps to increase the RF power to a predetermined value. By the RF power application method that combines the RF power reduction method of reducing the power and stopping the discharge, the dust generated between the back surface of the substrate and the electrode surface can be significantly reduced, and the product yield can be improved. In addition, a wafer transfer defect caused by maintaining close contact between the substrate and the electrode after the etching is also improved.

[Brief description of drawings]

FIG. 1 is a diagram showing an RF power applying method according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a dry etching apparatus.

FIG. 3 is a diagram showing a conventional RF power application method.

FIG. 4 is a view showing a wafer push-up state in a conventional dry etching method.

[Explanation of symbols]

 11 Upper Counter Electrode 12 Lower Electrode 14 Substrate

Claims (1)

[Claims] 1. A dry etching apparatus in which a substrate to be etched is placed on electrodes and RF power is applied, the RF power application is divided into a plurality of steps,
A dry etching method comprising a step of increasing the RF power to a predetermined value, and a step of dividing the RF power into a plurality of steps to reduce the RF power after the etching is finished and stopping the discharge.