JP3298341B2 - 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 an etching apparatus, a CV
The present invention relates to a plasma processing apparatus for processing a sample such as a wafer using plasma, using a plasma processing apparatus.

[0002]

2. Description of the Related Art A plasma processing apparatus such as an RIE (Reactive Ion Etching) apparatus has a high processing efficiency and processing quality because a chemical reaction proceeds rapidly by processing a sample using plasma. It is already industrially established in the field.

For example, a plasma etching apparatus is shown in FIG.
As shown in FIG. 1, a wafer 22 is etched by plasma generated by glow discharge of an etching gas filled in a chamber (not shown) by a high-frequency power supply 21. The wafer 22 is mounted on a lower electrode 23 fixed in the chamber via an insulating film 24. In this plasma etching apparatus, an electrostatic force is generated by a self-bias voltage of the wafer 22 generated by the generation of plasma and a DC voltage applied from the DC power supply 25 to the lower electrode 23, and the wafer 22 is placed on the lower electrode 23. To be held by suction.

[0004]

The above-mentioned electrostatic force is generated by the high frequency power of the high frequency power supply 21, the DC voltage of the DC power supply 25,
It depends on the dielectric constant, thickness, etc. of the insulating film 24. Therefore, even when the high-frequency power is set to be constant, the electrostatic force varies depending on the state of the insulating film 24 and the wafer 22.

If the electrostatic force is different, the degree of adhesion between the wafer 22 and the insulating film 24 is not constant, and the heat flow from the wafer 22 to the lower electrode 23 is different. Such a temperature change due to the difference in heat flow causes a change in the etching rate of the wafer 22. For example, when etching an Al alloy film, temperature dependence is increased because Al mainly reacts chemically with chlorine (processing gas). Therefore, when the temperature change as described above occurs, the uniformity of the etching also changes accordingly, and the wafer 22
This leads to a disadvantage that the uniformity of the etching is lowered every time.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and makes it possible to maintain the degree of adhesion between an object to be processed and an insulating film by correcting an electrostatic force in accordance with the holding force of the object. It is intended to be.

[0007]

According to the plasma processing apparatus of the present invention, an object to be processed such as a wafer mounted on an electrode via an insulating film is applied to the electrode by using a high-frequency wave. The process is performed by the plasma generated by the application of the electric power, and is generated by applying the DC voltage to the electrode and the electrostatic force generated by the self-bias voltage generated on the object to be processed by the generation of the plasma. A gas pressure is applied so that the back surface side of the object to be processed has a pressure different from that of the front side while the object to be processed is in close contact with the insulating film while being attracted and held on the electrode by electrostatic force. Further, a detecting means for detecting the gas pressure on the back side of the object to be processed and a pressure detected by the detecting means are compared with a predetermined value, and the DC voltage is corrected so that the difference between the two is eliminated. It is characterized in that a that correction means.

[0008]

In the above arrangement, for example, a space is provided in a part of the back surface of the object to be processed, and the space is filled with gas to apply pressure (the pressure is increased from the front side of the object to be processed). Is high), when the above-mentioned degree of adhesion is reduced and a gap is formed between the insulating film and the object to be processed, gas flows out from the gap and the pressure in the space (the back side of the object to be processed) is increased. Decrease. When the pressure is detected by the detecting means and a decrease in the pressure is recognized, the DC voltage is corrected by the correcting means so that the difference between the detected pressure and the predetermined value disappears. Thus, when the gas pressure reaches a predetermined value, the holding power of the object by the electrode is increased, and the degree of adhesion between the object and the insulating film is kept constant.

Further, when a low pressure state is maintained by discharging gas from the same space as described above (when the pressure is lower than the surface side of the object to be processed), the above-mentioned degree of adhesion is reduced and the insulating film is formed. When a gap is formed between the workpiece and the object, gas flows in from the gap and the pressure on the back side of the object increases. If an increase in the pressure is detected by the detection of the pressure by the detection means, the DC voltage is corrected by the correction means so that the difference between the detected pressure and the predetermined value is eliminated. This allows
When the gas pressure reaches a predetermined value, the holding power of the object by the electrode is increased, and the degree of adhesion between the object and the insulating film is kept constant.

As described above, according to the above configuration, if the degree of adhesion differs depending on the state of the insulating film and the object to be processed, the gas pressure on the back surface side of the object to be processed also varies, thereby reducing the degree of adhesion. Can be monitored. When the degree of adhesion decreases, the DC voltage is corrected to increase the holding force of the object to be processed and maintain the degree of adhesion constant, so that the heat flow from the object to the electrode side is kept constant. Can be.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIG.

The plasma etching apparatus according to the present embodiment includes a chamber (not shown) as a processing chamber. The chamber is evacuated and filled with an etching gas introduced from a gas inlet. ing. This chamber has a function as an anode and is grounded.

The present plasma etching apparatus includes a lower electrode 1 as an electrode. This lower electrode 1
A stepped hole 1a is provided in the above chamber and penetrates vertically in the center. The inner peripheral surface of the hole 1a is covered with a cylindrical insulating sleeve 2 along the stepped shape.

On the upper end surface of the lower electrode 1, an insulating film 3 having a diameter smaller than that of the lower electrode 1 is provided. This insulating film 3
A hole 3a substantially equal to the inner diameter of the upper portion 2a of the insulating sleeve 2 is provided at the center, and a wafer 4 as an object to be processed is placed on the upper end surface.

A bellows 5 which expands and contracts in the vertical direction is attached to the lower end surface of the lower electrode 1 around the opening of the hole 1a. The bellows 5 is entirely formed of metal, and is provided so that the inside is airtight to the atmosphere as in the chamber, while the bottom surface 5a is provided with an air cylinder via an insulator (not shown). (Not shown) so as to be driven in the vertical direction. A pedestal 6 for raising and lowering the wafer 4 at a transfer position by a transfer arm (not shown) is fixed on the bottom surface 5a.

The pedestal 6 as an elevating member has a mounting table 6a on which the wafer 4 is mounted and a shaft 6b for supporting the mounting table 6a, which are integrally formed.
“b” is provided so as to slide on the lower portion 2 b of the insulating sleeve 2. The pedestal 6 thus has the shaft 6b
Is held by the lower portion 2b, so that it can be moved up and down without causing shaft deviation.

A high frequency power supply 7 is connected to the lower electrode 1 via a matching network (not shown), and a DC power supply 8 provided in parallel with the high frequency power supply 7.
Is connected. Further, an LC circuit 9 is provided between the DC power supply 8 and the lower electrode 1 for the purpose of blocking the high frequency from the high frequency power supply 7 and measuring the bias voltage of the wafer 4.

A gas pipe 10 is connected to the bottom 5a of the bellows 5, and a gas is introduced from a mass flow controller 11 through the gas pipe 10. The gas pipe 10 is provided with a valve 12, and the supply or stop of the gas is performed by opening and closing the valve 12. The pressure in the bellows 5 is set to be higher than the pressure in the chamber, and to be a predetermined value in a state where the wafer 4 is normally in close contact with the insulating film 3. This pressure setting is performed by adjusting the flow rate of the mass flow controller 11.

The gas pipe 10 is provided with a pressure gauge 13 for measuring the pressure in the gas pipe 10 as detecting means. The measurement value of the pressure gauge 13 is provided to the control device 14. The control device 14 controls the operation of the present plasma etching apparatus, controls the operation of the mass flow controller 11, compares the measured value of the pressure gauge 13 with a predetermined value, and deviates the measured value from the predetermined value. In such a case, the voltage of the DC power supply 8 is controlled so that the difference disappears. That is, the control device 14
Has a function as correction means.

It is desirable to use the same gas as the etching gas in consideration of the fact that the gas introduced into the bellows 5 flows out of the bellows 5 into the chamber. Alternatively, the gas may be an inert gas.

In the above configuration, when performing the etching process, first, high frequency power is applied to the lower electrode 1 by the high frequency power supply 7, and plasma is generated by glow discharge in a chamber filled with the etching gas. hand,
The wafer 4 is etched by this plasma. At this time, a self-bias voltage is generated in the wafer 4 due to the generation of plasma. In addition, a DC voltage is applied to the lower electrode 1 by the DC power supply 8 with the application of the high frequency power. Then, the wafer 4 is attracted and held on the lower electrode 1 by the electrostatic force generated by the DC voltage and the electrostatic force generated by the self-bias voltage, and adheres to the insulating film 3.

In the etching process, when the gas supplied from the mass flow controller 11 is filled in the bellows 5, the bellows 5 is also filled in the hole 1a opened on the back surface side of the wafer 4 through the gap between the lower portion 2b and the shaft 6b. The gas is filled. In this state, when the wafer 4 is in close contact with the insulating film 3 with a normal degree of adhesion, the gas in the hole 1 a does not flow out from between the wafer 4 and the insulating film 3. Is kept constant. Therefore, in this case, the output of the DC power supply 8 becomes a constant value without being corrected by the control device 14.

However, when the degree of adhesion is reduced, a gap is formed between the wafer 4 and the insulating film 3, and the gas in the hole 1a flows out of the gap into the chamber, and the pressure in the bellows 5 is greatly reduced. I do. When the pressure at this time is detected by the pressure gauge 13, the processing device 14 recognizes that the measured value of the pressure is lower than a predetermined value, and increases the output of the DC power supply 8. Thereby, the holding force of the wafer 4 by the DC voltage is increased, and the above-mentioned degree of adhesion is kept constant.

As described above, in the present embodiment, the gas pressure on the back side of the wafer 4 is monitored, and when the gas pressure decreases, the DC voltage is adjusted, so that the holding force, that is, the electrostatic force of the wafer 4 is kept constant. To keep it. Therefore, the degree of adhesion between the wafer 4 and the insulating film 3 can be kept constant regardless of the state of the insulating film 3 or the wafer 4.
As described above, by controlling the degree of adhesion based on the gas pressure, the temperature difference of each wafer 4 under the same conditions can be controlled by ±
It could be controlled within 5 ° C. As a result, wafer 4
The variation in etching for each etching could be kept within ± 5%, and high uniformity could be secured.

Next, a modified example of this embodiment will be described. In this modification, as shown by a broken line in FIG. 1, a hole 1b vertically penetrating the lower electrode 1 is provided, and a hole 3b corresponding to the hole 1b is provided in the insulating film 3. The gas pressure is applied to the wafer 4 from the lower end surface side of the wafer 1 through the holes 1b and 3b. Therefore, as shown by a two-dot chain line in FIG.
The gas pipe 10 is connected, and gas from the mass flow controller 11 is introduced.

According to this configuration, similarly to the above configuration, when a gap is formed between the wafer 4 and the insulating film 3, the gas filled in the holes 1b and 3b flows out of the gap into the chamber. As a result, the pressure in the holes 1b and 3b is greatly reduced, so that the output of the DC power supply 8 is adjusted by the processing device 14, and the degree of adhesion is maintained substantially constant.

In both of the above configurations, the gas is filled in the bellows 5 or the holes 1b and 3b. On the contrary, the gas in the bellows 5 or the holes 1b and 3b is extracted and May be in a low pressure state (a state with a high degree of vacuum). In this case, since the pressure in the space becomes lower than the pressure in the chamber, when a gap is formed between the wafer 4 and the insulating film 3, the gas in the chamber is moved from the gap into the bellows 5 or the hole 1b. 3b, the pressure in the space increases. Therefore, if the DC voltage is adjusted by the controller 14 so that the pressure is reduced (to a predetermined value), the degree of adhesion can be kept constant as described above.

In this embodiment, the case where the present invention is applied to a plasma etching apparatus has been described.
Of course, the above-described configuration can be applied to a plasma processing apparatus such as a D apparatus.

[0029]

According to the plasma processing apparatus of the present invention, as described above, the processing object mounted on the electrode via the insulating film can be
The electrode is treated with plasma generated by applying high-frequency power, and at the same time, an electrostatic force generated by a self-bias voltage generated on the object to be processed due to plasma generation and a DC voltage are applied to the electrode. The gas pressure is adjusted so that the back surface of the object has a different pressure from the front surface while the object is in close contact with the insulating film while being attracted and held on the electrode by the electrostatic force generated thereby. Further, a detecting means for detecting the gas pressure on the back side of the object to be processed and a pressure detected by the detecting means are compared with a predetermined value, and a DC voltage is applied so as to eliminate the difference between the two. And a correction means for correcting

If the degree of adhesion between the insulating film and the object differs depending on the state of the insulating film or the object, the gas pressure on the back side of the object also differs. The decline can be monitored. When the degree of adhesion decreases, the DC voltage is corrected to increase the holding force of the object to be processed and maintain the degree of adhesion constant, so that the heat flow from the object to the electrode side is kept constant. Can be.

Therefore, when the plasma processing apparatus of the present invention is employed, there is an effect that the uniformity of etching for each processing object can be kept constant regardless of the state of the insulating film or the processing object.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a main part of a plasma etching apparatus according to one embodiment of the present invention.

FIG. 2 is a configuration diagram showing a main part of a conventional plasma etching apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Lower electrode (electrode) 1a hole 1b hole 3 Insulating film 3b hole 4 Wafer (workpiece) 5 Bellows 7 High frequency power supply 8 DC power supply 10 Gas pipe 11 Mass flow controller 11 13 Pressure gauge (detection means) 14 Control device (correction means) )

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) C23F 4/00 C23C 16/50 H01L 21/302 H05H 1/46

Claims (1)

(57) [Claims] An object to be processed placed on an electrode via an insulating film is processed with plasma generated by applying high-frequency power to the electrode, and the object to be processed is generated by plasma. While the electrostatic force generated by the self-bias voltage generated and the electrostatic force generated by the application of the DC voltage to the electrode is attracted and held on the electrode, the object adheres to the insulating film. In the state, the gas pressure is applied such that the back side of the object to be processed has a pressure different from that of the front side, and further, detecting means for detecting the gas pressure on the back side of the object, and this detecting means A plasma processing apparatus comprising: a correction unit that compares a detected pressure with a predetermined value and corrects a DC voltage so that a difference between the two values is eliminated.