KR100980972B1 - Plasma processing apparatus and method of plasma processing - Google Patents

Abstract

Also in the case of using a focus ring subjected to erosion by plasma, it is an object of the present invention to provide a plasma processing apparatus capable of maintaining etching characteristics and suppressing deterioration of a lower electrode, and a plasma processing method.

By providing a side protective ring on the side of the lower electrode, which is made of ceramic having a lower rate of erosion by the plasma than the material of the focus ring, the lower electrode side surface can be prevented from being damaged by the plasma. Even in the case where erosion proceeds, the etching characteristics can be maintained and the degradation of the lower electrode can be suppressed.

Description

Plasma processing apparatus and plasma processing method {PLASMA PROCESSING APPARATUS AND METHOD OF PLASMA PROCESSING}

1 is a schematic diagram of a plasma processing apparatus according to an embodiment of the present invention.

FIG. 2 is an enlarged view showing a relationship between a focus ring and a lower electrode on which a ceramic ring is disposed in the plasma processing apparatus shown in FIG. 1.

3 is a graph showing the relationship between the erosion amount of the focus ring and the cumulative RF discharge time of the focus ring in the conventional plasma processing apparatus.

4 is a graph showing the relationship between the temperature of the wafer end and the cumulative RF discharge time of the focus ring in the conventional plasma processing apparatus.

5 is a longitudinal sectional view showing the structure of the wafer W processed in the plasma processing apparatus.

6 is a graph showing a relationship between an etching rate of a silicon dioxide film at a wafer end and a focus ring cumulative RF discharge time in a conventional plasma processing apparatus.

7 is a graph showing the relationship between the silicon dioxide etching rate at the wafer end and the focus ring cumulative RF discharge time in the plasma processing apparatus according to the present invention.

8 is a graph showing the relationship between the etching rate of the silicon dioxide film at the wafer end and the cumulative RF discharge time of two focus rings used alternately in the plasma processing apparatus according to the present invention.

9 is a graph showing the relationship between the erosion amount of the ceramic ring and the cumulative RF discharge time of the ceramic ring.

10 is an enlarged view showing a relationship between a focus ring and an lower electrode which are not eroded in the conventional plasma processing apparatus.

11 is an enlarged view showing a relationship between an eroded focus ring and a lower electrode in the conventional plasma processing apparatus.

<Description of the symbols for the main parts of the drawings>

10 plasma processing apparatus 12 processing chamber

14 gas inlet port 16 upper electrode

18, 118: lower electrode 20, 120: electrostatic chuck

22: shield ring 24, 124: focus ring

26: RF power splitter 28: RF power

30: ceramic ring W: wafer

H: hole pattern M: photoresist mask pattern

S1: Si substrate S2: silicon dioxide film

The present invention relates to a plasma processing apparatus for treating a substrate surface using plasma and a plasma processing method for treating a substrate surface.

Plasma processing techniques such as dry etching techniques are widely used in the manufacture of semiconductor devices such as semiconductor integrated circuits. Plasma processing processes various thin films formed on the surface of a substrate, such as a semiconductor wafer, using a reaction gas excited by the plasma. The dry etching technique uses, for example, a photoresist pattern formed by a lithography technique as a mask to etch various thin films to form fine circuit patterns such as electrodes and wiring patterns.

Irrespective of the application method of the plasma treatment, the reaction gas excited by the plasma is inevitably in contact with the components in the processing chamber and erosion. In particular, for the treatment of the silicon oxide film, a high plasma due to the high bonding energy of Si-O is required. Output is required. Therefore, the treatment of the silicon oxide film causes severe damage to the components in the plasma.

In general, a so-called parallel plate type Reactive Ion Etcher (RIE) apparatus is mainly used as a dry etching apparatus for processing a silicon oxide film. In the parallel plate type RIE, high frequency power is applied to the upper and lower electrodes which face in parallel. In such an apparatus, a generally running wafer is placed on the bottom electrode and the plasma is concentrated between the electrodes to treat the surface of the wafer.

In order to concentrate the plasma between the electrodes, the periphery of the upper electrode and the lower electrode is surrounded by, for example, a ring of quartz material. Hereinafter, a ring of quartz material surrounding the upper electrode is referred to as a "shield ring," and a ring of quartz lipid surrounding the lower electrode is called a "focus ring."

In addition, in order to improve processing accuracy, an electrostatic chuck is widely employed as a means for placing a wafer on the wafer placing surface of the plasma processing apparatus. Compared with the mechanical clamp, the electrostatic chuck can improve the uniformity of the surface temperature of the wafer, thereby improving the processing accuracy.

The electrostatic chuck can be divided into two types. One is made of fluorocarbon resin and the other is made of ceramic. BACKGROUND ART An electrostatic chuck composed mainly of a fluorocarbon resin in which a conductive thin film is inserted into a fluorocarbon resin is used in a dry etching apparatus for processing a silicon oxide film. A DC high voltage is applied to the conductive thin film to generate a coulomb force between the conductive thin film and the wafer to fix the wafer to the upper surface of the electrostatic chuck.

10 is a partial cross-sectional view showing the periphery of the lower electrode of the plasma processing apparatus. As shown in FIG. 10, an electrostatic chuck 120 made of, for example, a fluorocarbon resin film 120a and a conductive thin film 120b inserted therein is provided on the upper surface 118a of the lower electrode 118. It is. The fluorocarbon resin film 120a also covers the side surface of the lower electrode 118.

The focus ring 124 is detachably disposed to surround the lower electrode 118. The processed wafer is placed on the top surface of the electrostatic chuck 120 and fixed by the electrostatic chuck. That is, the wafer W to be processed is placed on the upper surface 118a of the lower electrode 118, that is, the wafer placing surface, past the electrostatic chuck 120.

In the dry etching apparatus for processing the silicon oxide film described above, the most severely damaged by plasma is the focus ring 124 surrounding the lower electrode 118. If the focus ring continues to be used in the processing apparatus, its erosion proceeds slowly. Erosion mainly proceeds in the vertical direction at the stepped portion 124a near the inner circumference of the focus ring to form a groove. That is, erosion proceeds mainly in the vicinity of the outer circumference of the wafer (W).

As shown in FIG. 11, when the erosion reaches a certain level, the lower electrode side surface 118b is exposed to the plasma. Although the side surface 118b is covered with the fluorocarbon resin film 120a, the fluorocarbon resin film 120a is thin. Thereafter, the plasma may affect the temperature of the wafer W fixed by the electrostatic chuck 120 on the mounting surface 118a of the lower electrode 118.

As described above, wafer temperature management is important in etching fine patterns. However, as the erosion of the focus ring 124 proceeds as described above in the previous paragraph, the amount of plasma irradiation to the lower electrode 118 increases. The increased plasma dose increases the wafer W surface temperature, in particular the temperature at the end. This makes it difficult to maintain the required uniformity of etching.

In addition, exposure of the lower electrode 118 to the plasma accelerates deterioration, which shortens the life of the lower electrode 118. The lower electrode 118 to which the electrostatic chuck 120 is fixed is one of the most expensive components in the dry etching apparatus. Thus, shortening the life of the lower electrode 118 significantly increases the operating cost of the device.

That is, erosion of the focus ring 124 causes two problems, namely, change in etching characteristics and rapid deterioration of the lower electrode 118. Thus, the focus ring 124 was exchanged and / or repaired at short intervals before the focus ring 124 was severely damaged. As a result, the exchange and / or repair of the focus ring has to be made frequently, and the cost and throughput of manufacturing the semiconductor device by the processing device become worse. In the focus ring subjected to erosion by plasma, various improvements as disclosed in the patent literature have been proposed.

Patent Literature 1 discloses an electrode cover divided into an inner part and an outer part. The inner part is divided into a plurality of parts divided in the circumferential direction and surrounds the side of the lower electrode. The outer part is fixed to the outer surface of the inner part. Thus, the plurality of divided portions and portions combine to form a cover or focus ring and have an inner circumference that surrounds the side of the lower electrode.

Patent Document 2 discloses a quartz member coated with an insulating film having high resistance to erosion of plasma, that is, a focus ring. In particular, Patent Document 2 proposes the formation of an insulating film layer having a high resistance to erosion, for example, an alumina ceramic layer, on the surface of a quartz member in contact with plasma.

Japanese Patent Laid-Open No. 2-130823 (Patent Document 3) discloses a ring composed of an inner aluminum ring and an outer fluorinated resin ring to cover the periphery of a lower electrode. In particular, the aluminum ring disclosed in Patent Document 3 covers the side surface of the lower electrode, and a part of the aluminum ring is exposed to the plasma at a position adjacent to the outer circumference of the substrate to be processed outside. Patent document 3 explains that the plasma eroding the fluorinated resin ring does not erode the aluminum ring, and the aluminum ring can maintain the etching uniformity for a long time.

[Patent Document 1]

Japanese Patent Publication 2003-100713

[Patent Document 2]

Japanese Patent Publication Hei 8-339895

[Patent Document 3]

Japanese Patent Publication 2003-130823

The focus ring described in Patent Document 1 aims to reduce the clearance between the lower electrode and the focus ring. It is not intended to reduce the erosion of the focus ring.

In the quartz member described in Patent Document 2, an insulating film having a high erosion resistance is coded on the surface of the quartz member designed in a form suitable for use in a processing apparatus. Therefore, the thickness of the resistive coating film is limited so that the coating film cannot substantially change the shape of the quartz member. Thus, the ability to improve erosion resistance is limited.

In addition, in Patent Document 2, charged particles in the plasma accelerated in the direction perpendicular to the substrate surface to be treated are radiated to the insulating film. Similarly, in Patent Document 3, charged particles in the plasma accelerated in the direction perpendicular to the substrate surface to be treated are incident on the portion of the aluminum ring. Therefore, an insulating film having a secondary electron emission coefficient different from that of the quartz member, or an aluminum ring having a secondary electron emission coefficient different from the fluorinated resin ring affects the plasma characteristics.

As a result, the plasma discharge conditions used in the conventional plasma processing apparatus without the insulating film of Patent Document 2 or the aluminum ring of Patent Document 3 cannot be used when the insulating film or the aluminum ring is added to the processing apparatus. Therefore, neither the insulating film of patent document 2 nor the aluminum ring of patent document 3 is suitable as a means to retrofit an apparatus, for example.

Accordingly, in order to solve the above problems, an object of the present invention is to maintain a desirable etching characteristic without substantially changing the plasma discharge conditions used in the conventional apparatus and method even if the focus ring is severely eroded by the plasma. , And a plasma treatment method. Another object of the present invention is to provide an apparatus and method capable of preventing deterioration of the lower electrode without substantially changing the plasma discharge conditions used in the conventional apparatus and method even if the focus ring is severely eroded.

In order to solve the above problems, the present invention has a lower electrode having a supporting surface and a side surface connected to an outer circumference of the mounting surface, and the surface of the substrate to be mounted on the mounting surface is connected to the plasma. A plasma processing apparatus for processing by means of the present invention, comprising: a focus ring made of a first material, a focus ring made of a first material, and a side surface of the lower electrode, covered with a ceramic material different from the first material; It is made, and the outer periphery is provided with a plasma protection device characterized in that it has a side protective ring located inside the outer periphery of the substrate to be disposed on the mounting surface.

Moreover, in this invention, it is typical embodiment that the said 1st material and the said ceramic material have a different secondary electron emission coefficient. In addition, it is preferable that the erosion rate of the ceramic material by plasma is lower than the erosion rate of the first material.

In this invention, it is preferable that the said ceramic material is alumina. It is also preferable that the first material is quartz.

In addition, in order to solve the above-mentioned problem, the present invention provides a surface of a substrate to be placed on the mounting surface of the lower electrode having a mounting surface and a side surface connected to an outer circumference of the mounting surface. A method of treating a plasma by generating a plasma in a space facing a surface of the substrate, wherein the periphery of the substrate is covered with a focus ring made of a first material, and a side surface of the lower electrode is surrounded by an outer circumference. Covered with a side protection ring made of a ceramic material different from the first material, the plasma contacts the side of the lower electrode so as to be located inside the outer periphery of the substrate to be placed on the tooth surface. And charged particles accelerated by the substrate to be perpendicular to the surface of the substrate from the plasma. It provides a plasma processing method characterized in that the incident to the side protection ring.
In the present invention, before the erosion of the focus ring by the plasma proceeds, the substrate and the focus ring prevent the plasma from contacting the side protection ring and prevent the plasma from contacting the side protection ring. Even after the erosion of the focus ring progresses and the substrate to be processed and the focus ring cannot prevent the plasma from contacting the side protection ring, the plasma comes into contact with the side surface by the side protection ring. It is a typical embodiment to prevent it.

Preferably, the outer circumference of the side protection ring is positioned inside the outer circumference of the substrate to be processed mounted on the mounting surface.

Further, it is preferable that the substrate to be processed is a semiconductor substrate, and the processing is etching of an insulating film on the surface of the semiconductor substrate using a fluorocarbon plasma.

Embodiment of the Invention

EMBODIMENT OF THE INVENTION Below, the plasma processing apparatus and plasma processing method which concern on this invention are demonstrated in detail with reference to various preferable embodiment shown in an accompanying drawing.

1 is a schematic diagram of a plasma processing apparatus for performing a plasma processing method according to an embodiment of the present invention. As shown in FIG. 1, the plasma processing apparatus 10 is a dry etching apparatus for semiconductor device manufacture. The device 10 has a narrow planar parallel plate structure and etches oxide films such as silicon oxide films using radio frequency plasma.

The processing chamber 12 containing the wafer W, which is the substrate to be processed, may be evacuated to a pressure of about 10 ⁻⁶ Torr (10 ⁻⁴ Pa). Various components are provided in this chamber 12.

In the upper center of the chamber 12, the upper electrode 16 to which the gas inlet 14 which can introduce | transduce etching gas is connected is provided. In the lower center of the chamber 12, a lower electrode 18 is provided.

The lower electrode 18 is made of anodized aluminum. The upper surface 18a of the lower electrode 18, that is, the wafer placing surface, is approximately the same as the wafer W or slightly smaller. Inside the lower electrode 18, a circulation path (not shown) for circulating a refrigerant supplied from a cooling device (not shown) provided outside the chamber 12 is provided. Therefore, the upper surface 18a of the lower electrode 18 can be maintained at a desired temperature.

An electrostatic chuck 20 for fixing the wafer W is provided on the upper surface 18a of the lower electrode 18. The electrostatic chuck 20 is formed of a fluorocarbon resin film into which a metal thin film is inserted. The fluorocarbon resin film forms the electrostatic chuck 20 and covers the side surface of the lower electrode 18.

When a voltage is applied to the metal thin film from an external high voltage direct current power supply (not shown) provided outside the chamber 12, a coulomb force is generated between the metal thin film and the wafer (W). Thus, the wafer W is fixed to the upper surface of the electrostatic chuck 20. That is, the wafer W is fixed on the wafer placing surface 18a of the lower electrode 18 by the electrostatic chuck 20. The height of the upper surface 24b of the focus ring 24 is generally matched with the height of the wafer W placed on the wafer placing surface 18a.

In addition, the lower electrode 18 has a flow path (not shown) for supplying He gas. It is possible to increase the thermal conductivity between the wafer W and the lower electrode 18 by supplying He gas to the back surface of the wafer W fixed on the electrostatic chuck 20. The gas flow path is divided into two groups, and thus, the He gas pressure supplied to the center and the outside of the wafer W can be independently controlled.

The side surface 18b of the lower electrode 18 is provided with a side protective ring 30 formed of a ceramic material (hereinafter referred to as a 'ceramic ring'). That is, the ceramic ring 30 covers the surface of the fluorocarbon resin film 20a covering the side surface 18b of the lower electrode 18, more precisely, the side surface 18b of the lower electrode 18.

The circumference | surroundings of the upper electrode 16 and the lower electrode 18 are covered by the shield ring 22 and the focus ring 24, respectively. The shield ring 22 and the focus ring 24 together have a function of concentrating plasma between the parallel plate electrodes. The shield ring 22 and the focus ring 24 are removable for mechanical cleaning, for example.

An RF power splitter 26 and an RF power source 28 are provided outside the chamber 12. The RF power source 28 supplies radio frequency power to the RF power splitter 26, and the RF power splitter 26 supplies high frequency power (RF power) to both the lower electrode 18 and the upper electrode 16. Is applied. Therefore, RF plasma is generated in the chamber 12 and dry etching is performed.

The plasma processing apparatus 10 shown in FIG. 1 employs a split coupling method using an RF power splitter 26 as an example. However, any one of an anode coupling method, a cathode coupling method, and a split coupling method may be selected.

Next, the side protection ring (ceramic ring) 30 according to the embodiment of the present invention will be described. 2 is an enlarged view showing the relationship between the lower electrode 18 and the focus ring 24 in which the ceramic ring 30 according to the present invention is disposed.

The ceramic ring 30 has an annular structure and is formed of a ceramic material whose etching rate by plasma is lower than that of the material forming the focus ring 24.

As described above, the fluorocarbon resin film 20a constituting the electrostatic chuck 20 is covered on the side surface 18b of the lower electrode 18, and a focus ring 24 is disposed around the fluorocarbon resin film 20a. The ceramic ring 30 is inserted between the fluorocarbon resin film 20a covering the side surface 18b of the lower electrode 18 and the inner surface of the focus ring 24. That is, the side surface 18b of the lower electrode 18 is covered by the fluorocarbon resin film 20a, which is covered by the ceramic ring 30, and is then surrounded by the focus ring 24.

In the plasma processing apparatus 10 shown in FIG. 2, the ceramic ring 30 has a predetermined thickness (dimensions perpendicular to the side surface 18b of the lower electrode 18) and is formed inside the outer circumference of the wafer W. FIG. Is installed.

As the erosion of the focus ring 24 proceeds to some extent, the ceramic ring 30 is directly exposed to the plasma. Therefore, the ceramic ring 30 preferably has a sufficient thickness to improve durability or mechanical strength.

 However, if the thickness of the ceramic ring 30 is too thick, charged particles which extend from the outer circumference of the wafer W and are accelerated in a direction perpendicular to the surface of the wafer W may form the surface of the ceramic ring 30 from the plasma. Will be entered. As a result, the plasma characteristics fluctuate from the difference in the secondary electron emission coefficient generated from the ceramic ring 30 and the quartz focus ring 24. Such a change in plasma properties causes the etching conditions to change. Further, depending on the etching process, minute emissions from the ceramic ring 30 may shift the electrical characteristics of the semiconductor device itself.

Therefore, the dimension of the mounting surface 18a of the lower electrode 18 is made smaller than the dimension of the wafer W so that the outer circumference of the ceramic ring 30 is approximately equal to the outer circumference of the wafer W, or more preferably. Preferably located inside.

According to various embodiments of the present disclosure, the coating of the fluorocarbon resin film 20a on the side surface 18b of the lower electrode 18 is not essential. In addition, the material of the focus ring 24 is not limited to quartz. As a material for forming the focus ring 24, for example, silicon may be used. Engineering plastics (also called super engineering plastics) with high operating temperatures can be used. For example, VePel® Polymide from DuPot and Celazole® PolyzImidazole from Celanese Advanced Material can be used.

The material of the side protection ring 30 may preferably be alumina, for example, but is not limited to a specific material among various ceramic materials. Other ceramic materials can be used, such as aluminum nitride, silicon nitride, and silicon carbide. In addition, at least zirconia, titanium nitride, and YAG (Y ₃ Al ₅ 0 ₁₂ ) may be used in the processing apparatus for use in the back-end of the line (BEOL) treatment in the production of semiconductor devices. In addition, a solid solution comprising one or more of these materials such as alumina-silica solid solution, alumina-silicone solid solution and the like can be used. These ceramic materials can also include various additives.

The aforementioned materials for the focus ring 24 have different etching rates. In addition, the above-mentioned ceramic materials have different etching rates. Etch rates also vary depending on various conditions such as process gas and plasma discharge conditions. In addition, the actual etching rate of the material forming the focus ring 24 and the ceramic ring 30 also varies depending on the position of the components provided in the plasma processing apparatus 10.

In general, however, the above-mentioned ceramic material has an etching rate smaller than the etching rate of the above-mentioned material for the focus ring 24.

In order to perform etching using the plasma processing apparatus 10, after exhausting the inside of the chamber 12 to a predetermined pressure, a carbon fluoride-based etching gas is introduced from the gas inlet 14, and the electrode 16, 18) Form an etching gas atmosphere of constant pressure in the space between them. The fluorocarbon plasma is generated by supplying high frequency power between the electrodes 16 and 18 from the RF power splitter 26 to this constant pressure etching gas atmosphere. As a result, charged particles in this plasma are accelerated in a direction perpendicular to the surface of the wafer W located on the mounting surface 18a of the lower electrode 18, and the surface of the wafer W is etched.

In various embodiments according to the present invention, the side of the lower electrode 18 is protected by a ceramic ring 30 formed of a material having an etching rate lower than that of the material of the focus ring 24. Therefore, even after the focus ring 24 is eroded severely by the plasma, the side surface 18b of the lower electrode 18 is not exposed to the plasma and is not damaged. As a result, an increase in the surface temperature of the wafer end portion can be suppressed and the etching characteristics can be maintained.

In addition, the replacement cycle of the focus ring 24 can be extended because the desired etching characteristics can be maintained even after the focus ring is severely eroded. The result is lower maintenance costs.

In addition, since the ceramic ring 30 protects the side 18b of the lower electrode 18, the carbon fluorocarbon resin film covering the side 18b of the lower electrode 18 during physical attachment and detachment of the focus ring 24 is physically damaged. You can prevent receiving.

In the plasma processing apparatus of the present embodiment, before the erosion of the focus ring 24 proceeds, the wafer W and the focus ring 24 have a plasma side surface of the ceramic ring 30 and the lower electrode 18. 18b) can be prevented from being exposed to the plasma. On the other hand, after erosion of the focus ring 24 proceeds to the extent that the ceramic ring 30 cannot be exposed to the plasma, the ceramic ring 30 is exposed to the plasma by the side surface 18b of the lower electrode 18. Prevent it.

That is, even after the focus ring 24 is eroded to such an extent that the side 18b of the lower electrode 18 can not be prevented from being exposed to the plasma, the ceramic ring 30 remains at the side 18b of the lower electrode 18. This is prevented from being exposed to the plasma.

In addition, in the plasma processing apparatus 10 of the present embodiment, the dimension of the mounting surface 18a of the lower electrode 18 is made smaller than the dimension of the wafer W, and the outer circumference of the ceramic ring 30 is made into the wafer ( Either coincide with the outside circumference of W) or place it inside. Therefore, the charged particles accelerated in the direction perpendicular to the surface of the wafer W after the focus ring 24 is eroded can be prevented from entering the ceramic ring 30 from the plasma.

When the outer circumference of the ceramic ring 30 is located inside the outer circumference of the wafer W, the entire portion of the ceramic ring 30 is caused by charged particles in the plasma accelerated in a direction perpendicular to the surface of the wafer W. Incident is prevented.

When the dimensions of the ceramic ring 30 are designed so that the outer circumference of the ceramic ring 30 coincides with the outer circumference of the wafer W on the wafer placing surface 18a, a small portion of the ceramic ring 30 is not intended. The change in dimensions and the position of the wafer W and the ceramic ring 30 may extend outwardly from the outer circumference of the wafer W. In other words, the outer circumference of the ceramic ring 30 is actually aligned so as to approximately coincide with the outer circumference of the wafer W. As shown in FIG. Accelerated charged particles enter the extended portion of the ceramic ring 30. Nevertheless, accelerated charged particles are prevented from entering the remaining portion of the ceramic ring 30. Thus, the area of the portion of the ceramic ring 30 incident by the accelerated charged particles is much smaller than when the dimensions of the ceramic ring 30 are designed to extend outwardly from the outer circumference of the wafer W.

As a result, although the secondary electron emission coefficient of the ceramic material used for forming the ceramic ring 30 is different from the secondary electron emission coefficient of the material forming the focus ring 24, the ceramic ring 30 is substantially This does not affect the plasma characteristics. Therefore, the plasma emission conditions used in the conventional plasma processing apparatus without the ceramic ring can be used without changing essentially in the processing apparatus 10 with the ceramic ring 30.

The plasma processing apparatus and the plasma processing method according to the present invention are not limited to the above-described embodiment. For example, the plasma processing apparatus may be any type of plasma processing apparatus including an electrode having a substrate placing surface. In addition, the plasma processing apparatus according to the present invention is not limited to a semiconductor device manufacturing apparatus for surface treatment of a semiconductor substrate, but may be various apparatuses for processing various other substrates. In addition, various reaction gases except for fluorocarbon gas may be used.

Comparative Example 1

As a comparative example for confirming the effect of the ceramic ring 30 of the plasma processing apparatus 10 of this embodiment, etching was performed using the plasma processing apparatus of the conventional form in which the ceramic ring 30 is not attached.

3 shows the amount of erosion in the vertical direction of the focus ring 124 of the conventional plasma processing apparatus, that is, the surface of the wafer W placed on the wafer placing surface 18a and the cumulative RF discharge time of the focus ring 124. (Ie, cumulative RF discharge time made using the same focus ring 124).

11 shows the shape of the focus ring 124 when the erosion amount is about 1 mm. 3 shows that the focus ring 124 reaches this shape when the cumulative RF discharge reaches 300 hours. When the focus ring 124 is in the form of FIG. 11, desired etching characteristics cannot be maintained.

First, in order to examine the relationship between the erosion amount of the focus ring 24 and the temperature of the surface of the wafer W, the wafer surface temperature was measured while the plasma was generated. In particular, the surface temperature of 5 mm site | part was measured from the wafer edge.

As a processing gas for dry etching, a mixed gas of etching gas (CF ₄ , C ₄ F ₈ ), CO, and Ar was used. Table 1 shows the discharge conditions of the plasma when the temperature of the wafer surface is measured. Meanwhile, the plasma processing apparatus 10 is used for the production of semiconductor devices having different processing gases and different plasma discharge conditions shown in FIG. 2.

TABLE 1

Discharge pressure
[mTorr] RF power density
[wcm ^-2 ]      Gas flow rate [sccm]   Refrigerant temperature [℃] He pressure
[Torr] CF ₄ C ₄ F ₈  CO  Ar Upper electrode Bottom electrode center Tip    150    4.65  10  8  120 350    30   -10   10   19

TABLE 2

Discharge pressure
[mTorr] RF power density
[wcm ^-2 ]
Gas flow rate [sccm]    Refrigerant temperature [℃] He pressure
[Torr] CF ₄ CHF ₈  Ar Top
electrode bottom
electrode  center  Tip    300    4.65  40  30  500    30   -10   10   22

This measurement result is shown in FIG. 4 shows the change of the surface temperature of the end portion of the wafer W with respect to the cumulative RF discharge time of the focus ring 124. 4 shows that when the cumulative RF discharge time of the focus ring 124 exceeds 300 hours, the surface temperature of the end portion of the wafer W increases due to the increased radiation of the plasma to the side surface 118b of the lower electrode 118.

As shown in FIG. 11, the side surface 118b of the lower electrode 118 is covered with the carbon fluoride resin film 120a. Accordingly, the side surface 118b of the lower electrode 118 is not directly exposed to the plasma, but only through the carbon fluorocarbon resin film 120a. However, since the fluorocarbon resin film 120a is thin, heat energy received from the plasma is easily transferred to the lower electrode 18.

In addition, the lower electrode 118 is circulated with a refrigerant having a temperature shown in Table 1. Since there is some distance between the side and the circulation path, the temperature near the side 118b rises when the side 118b is exposed to the plasma. Therefore, the temperature of the end portion of the wafer W rises.

Next, dry etching was performed to investigate the change in the etching rate of the fine holes at the end of the wafer W as the cumulative RF discharge time of the focus ring 124 increased. In particular, the wafer W surface shown in FIG. 5 is etched according to the conditions shown in Table 1.

However, as described above, the device is used for production under the conditions shown in Table 2. Here, the conditions of Table 1 are suitable for etching fine holes, but are strongly influenced by the surface temperature of the wafer W.

In the wafer W shown in FIG. 5, the silicon dioxide film S2 is formed to a thickness of 2.0 μm on the silicon substrate S1, and the mask pattern M by photoresist is formed to a thickness of 1.2 μm thereon. It is. A hole H of 0.30 mu m is formed in the mask. As a processing gas for dry etching, an etching gas (CF ₄ , C ₄ F ₈ ), a mixed gas of CO and Ar was used. The etching rate was measured in the area of 5 mm from the extreme end of the wafer (W).

This measurement result is shown in FIG. 6 shows a change in the etching rate of the silicon dioxide film with respect to the cumulative RF discharge time of the focus ring 124. 6 shows that when the cumulative RF discharge time of the focus ring 124 exceeds 300 hours, the etching rate of the end portion of the wafer W decreases significantly.

The result is that 1) if the cumulative RF discharge time of the focus ring 124 exceeds 300 hours, the focus ring 124 is severely damaged and the amount of plasma irradiation to the side surface 118b of the lower electrode 118 increases, and 2) As a result, the wafer W end surface temperature is increased to show that the etching rate near the wafer W end is reduced. That is, if the cumulative RF discharge time exceeds 300 hours, it is impossible to maintain the desired etching characteristics.

In addition, in the conventional plasma processing apparatus, when the erosion of the focus ring 124 becomes the shape shown in Fig. 11, the lower electrode 118 is further damaged.

The fluorocarbon resin film 120a covering the side surface 118b of the lower electrode 118 does not have a strong resistance to the plasma. Therefore, as illustrated in FIG. 11, when the focus ring 124 is eroded, the fluorocarbon resin film 120a covering the side surface 118b of the lower electrode 118 may be easily deteriorated. In addition, in the conventional plasma processing apparatus, it is difficult to prevent damage to the fluorocarbon resin film 120a on the side surface 118b during attachment and detachment of the focus ring 124.

As a result, when the focus ring 124 is severely eroded as shown in FIG. 11, the carbon fluorocarbon resin 120a partially disappears at least on the side surface 118b of the lower electrode 118, thereby lowering the lower electrode 118. The plasma is directly irradiated on the side surface 118b. Direct irradiation of the plasma degrades the coated alumite on the side surface 118b of the lower electrode 118 and causes abnormal discharge or arcing from the portion where the insulation is broken.

When the abnormal discharge occurs, the lower electrode 118 can no longer be used. Therefore, the device must be stopped and replaced with a new lower electrode 118.

As described above, in the conventional plasma processing apparatus in which the ceramic ring 30 is not mounted, when the focus ring 124 is eroded, the etching rate fluctuates and the lower electrode 118 is damaged. Therefore, if the cumulative RF discharge time exceeds 300 hours or is visually eroded by about 1 mm in the vertical direction, the focus ring 124 needs to be replaced. The focus ring 124 used is discarded or repaired.

Example 1

Dry etching of the silicon dioxide film S2 on the surface of the wafer W shown in FIG. 5 was performed using the plasma processing apparatus 10 shown in FIG. And the change of the etching rate was observed.

As shown in FIG. 2, the outer periphery of the ceramic ring 30 was located inside the outer periphery of the wafer W. As shown in FIG. In particular, the dimension or diameter of the mounting surface 18a of the lower electrode 18 is made about 6 mm smaller than the dimension or diameter of the wafer W and the thickness or width of the ceramic ring 30 is 2 mm. Accordingly, the outer circumference of the ceramic ring 30 is located about 1 mm from the outer circumference of the wafer (W). The material of the ceramic ring is alumina.

In the experiment, a heavily eroded focus ring 24 was used. In particular, the focus ring 24 eroded to a depth of 3 mm in the vertical direction to the stepped portion 24a near the inner side toward the lower electrode 18 was used. This erosion amount is three times the maximum allowable erosion depth (1 mm) in the conventional plasma processing apparatus. That is, a cumulative RF discharge time of about 900 hours was used.

Etching was performed using the plasma discharge conditions shown in Table 3 to measure the etching rate. The device 10 is also used for the production of semiconductor devices using the conditions shown in Table 2.

TABLE 3

Discharge pressure
[mTorr] RF power density
[wcm ^-2 ]      Gas flow rate [sccm]   Refrigerant temperature [℃] He pressure
[Torr] CF ₄ C ₄ F ₈  CO  Ar Top
electrode bottom
electrode  center Tip    150    4.65  10  8  120  350   30  -10   10   16

Here, in the case where the ceramic ring 30 is mounted around the side surface 18b of the lower electrode 18, under the discharge conditions shown in Table 1, the surface temperature is about 5 ° C. in the region from the end of the wafer to about 5 mm. Lowers. This contributes to the fact that the plasma is not directly irradiated on the side surface of the lower electrode 18 as compared with the conventional state, and the difference in thermal conductivity between the ceramic ring 30 and the focus ring 24 is contributed. In particular, since the thermal conductivity of the ceramic is 20 times or more compared with that of quartz, which is the material of the focus ring 24, the cooling effect of the wafer end portion is improved.

Therefore, in order to make the surface temperature of the wafer W uniform, the etching rate was measured using the conditions shown in Table 3. In particular, as shown in Table 3, the He pressure supplied around the wafer backside was lowered by only about 3 Torr at the end compared with the conditions shown in Table 1. Otherwise, the conditions shown in Table 3 are the same as those shown in Table 1.

7 shows the change of silicon dioxide etching rate with respect to the cumulative RF discharge time of the focus ring 24 at this time. As shown in FIG. 7, even if the vertical erosion amount of the 3 mm focus ring 24 was used for 400 hours, the etching rate of 0.30 micrometer hole did not change significantly.

The result is that by mounting the ceramic ring 30, regardless of the amount of erosion of the focus ring 24, the surface temperature of the wafer W can be kept uniform at all times, which is stable regardless of the amount of erosion of the focus ring 24. It shows that the etching rate can be obtained. That is, even after the focus ring 24 is severely eroded, the ceramic ring 30 can maintain desired etching characteristics. In addition, since the etching rate is stabilized regardless of the amount of erosion, the use time of the focus ring 24 can be extended.

 In addition, as described above, it is not necessary to substantially change the etching conditions when using the ceramic ring 30. In particular, the etching conditions shown in Table 3 are the same as those of the conventional conditions shown in Table 1 except that the He pressure supplied to the backside of the wafer W is adjusted, so that the apparatus 10 using the ceramic ring 30 can be used. Can be. This result shows that the ceramic ring 30 does not substantially affect the plasma properties.

 In the present embodiment, since the focus ring 24 which has been eroded from the beginning is used, the ceramic ring 30 has been exposed to the plasma. However, since the outer circumference of the ceramic ring 30 is located inside the outer circumference of the wafer W, charged particles accelerated in a direction perpendicular to the surface of the wafer W are transferred from the plasma to the ceramic ring 30. Incident is prevented. Therefore, the plasma characteristics are not significantly changed.

[Example 2]

Next, using the plasma processing apparatus shown in FIG. 1, etching treatment was performed for a plurality of wafers W having the structure shown in FIG. 5. The thickness of the ceramic ring 30 was 2 mm. Further, two focus rings 30 without deterioration were prepared, and a running test was conducted while replacing the focus rings 30. That is, the device 10 was stopped every 50 hours after the application time of the RF for mechanical cleaning. The focus ring 24 is replaced with another one during mechanical cleaning.

Using the plasma discharge conditions shown in Table 3 was measured 0.30㎛ diameter etching rate at a predetermined interval. The device is used for other purposes under the conditions shown in Table 2.

8 shows the change in the etching rate of 0.30 mu m hole with respect to the focus ring 24 cumulative RF discharge time (i.e., the cumulative RF discharge time made using two focus rings 24). 8 shows that even when the cumulative RF discharge time of the focus ring 24 reaches 1200 hours, that is, when the cumulative RF discharge time of the focus ring 24 reaches 600 hours, the change in the etching rate is small.

On the other hand, in the conventional apparatus as shown in Fig. 6, when the cumulative RF discharge time of the focus ring reaches 300 hours, the change in the etching rate is large. Thus, it has been found that by employing the ceramic ring 30 the lifetime, i.e. the maximum usable time of the focus ring 24, can be extended at least twice.

During the running test, the lower electrode 18 was not damaged. In this test, the ceramic ring 30 was prepared as a separate part from the lower electrode 18 and mounted on the side surface 18b of the lower electrode 18 at the start of the test. Since the ceramic ring 30 has a smaller outer diameter and a lighter weight than the focus ring 24, the ceramic ring 30 can be easily mounted on the lower electrode 18. Therefore, the fluorocarbon resin film on the side surface 18b of the lower electrode 18 was not damaged during mounting. In addition, it is not necessary to remove the ceramic ring 30 at the time of mechanical cleaning.

Finally, FIG. 9 shows the amount of erosion to the change in the cumulative RF discharge time of the focus ring 24 or the cumulative RF discharge time using the two focus rings 24 and the ceramic ring 30 according to the present embodiment, that is, ceramics. The amount of reduction in the thickness of the ring 30 (dimension in the direction perpendicular to the side face 18b) is shown. In particular, FIG. 9 shows the maximum erosion measured at the portion near the end of the ceramic ring 30. 9 shows that the erosion amount is about 1 mm when the cumulative RF discharge time is 1200 hours. That is, for example, when the thickness of the ceramic ring 30 is 2 mm, even if the cumulative RF discharge time is at least 1200 hours, the shielding effect of preventing the plasma from contacting the side surface 18b of the lower electrode 18 can be sufficiently maintained. It can be seen that.

9 shows the etching rate of the ceramic material measuring the erosion amount of the ceramic ring 30 in the direction perpendicular to the side surface 18b of the lower electrode 18 during the initial time before the cumulative RF discharge time of less than about 300 hours. shows / min During the same time, FIG. 3 shows that the quartz etch rate, which measured the erosion of the focus ring in the vertical direction, that is, the direction perpendicular to the surface of the wafer W, was about 56 nm / min. That is, the etching rate of the ceramic material in which the erosion amount of the ceramic ring 30 is measured in the direction perpendicular to the side surface 18b of the lower electrode 18 is the erosion amount of the focus ring in the direction perpendicular to the surface of the wafer W. It is smaller than half of the measured quartz etching rate.

9 shows that the erosion amount of the ceramic ring 30 is saturated when the cumulative RF discharge time increases. That is, as the cumulative RF discharge time increases, the etching rate of the ceramic ring 30 decreases. The smaller etch rate compared to the focus ring 24, the ceramic ring 30 can be used for a considerable period of time even after the focus ring 24 is eroded badly.

The etch rate and its ratio calculated from the data shown in FIGS. 3 and 9 are determined not only by the difference in material properties but also by the position of the ceramic ring 30 and the focus ring 24 in the plasma processing apparatus 10. Notice. In fact, the etching rate of alumina measured by the etching rate of the aluminum oxide film on the wafer W surface located on the wafer placing surface 18a of the plasma processing apparatus 10 is the wafer W surface located on the wafer placing surface 18a. It can be seen that it is about 30 times smaller than the quartz etching rate measured by the etching rate of the silicon oxide film.

In practice, the actual etch rate of the ceramic ring 30 mounted within the processing apparatus 10 determines the life of the ceramic ring 30.

The present invention is basically as described above.

As mentioned above, although the plasma processing apparatus and plasma processing method of this invention were demonstrated in detail, this invention is not limited to the said embodiment, A various improvement and change may be made in the range which does not deviate from the main point of this invention. Of course.

For example, in the above embodiment, for comparison with the conventional plasma processing apparatus, the lower electrode 18 having the coating of the fluorocarbon resin film having the excellent plasma resistance in the resin material on the side surface 18b was used. However, even if the fluorocarbon resin film on the side surface is not provided, it is possible to prevent the plasma ring from contacting the side surface of the lower electrode 18 even when the focus ring 24 is eroded by the ceramic ring 30. . Therefore, even if the fluorocarbon resin film is not provided on the side surface 18b of the lower electrode 18, the life of the lower electrode 18 can be realized as in the case where the lower electrode 18 is provided.

In the above embodiment, the lower electrode 18 having the electrostatic chuck 20 made of fluorocarbon resin was used. However, it is similarly applicable to a plasma processing apparatus having a lower electrode 18 having an electrostatic chuck made of ceramic. Also in this case, coating with ceramics on the lower electrode 18 side surface is not essential, as in the case of providing an electrostatic chuck made of a fluorocarbon resin.

However, in the case where the ceramic coating is provided on the side surface 18 of the lower electrode 18, even when the focus ring 24 is eroded by the ceramic ring 30, plasma is applied to the side surface of the lower electrode 18. Can be prevented from contacting. It is also different from the ceramic coating formed on the side 18b of the lower electrode and can be replaced with a new one when the ceramic ring 30 prepared to fall off the lower electrode 18 is severely eroded. Thus, the ceramic ring 30 can greatly extend the life of the ceramic coating.

In this embodiment, the ceramic ring 30 has a constant thickness (dimensions perpendicular to the side 18b of the bottom electrode 18) over the entire height along the side 18b of the bottom electrode. Thus, the entire portion of the ceramic ring 30 is located inside the outer circumference of the wafer W placed on the mounting surface 18a. However, as in the case of the aluminum ring disclosed in Patent Document 3, the ceramic ring may extend below the focus ring 24. The focus ring 24 prevents charged particles from accelerating in the direction perpendicular to the substrate surface from entering such extended portions unless the overall thickness is eroded. Thus, the extended portion of the serimak ring 30 does not affect the plasma.

Thus, the portion of the ceramic ring 30 is outside of the wafer W as long as it prevents accelerated charged particles from entering the portion of the ceramic ring 30 even after the focus ring 24 or other component is severely eroded. It can be located outside of the perimeter. That is, a portion of the ceramic ring 30 that is exposed to the plasma when the focus ring 24 or other component is severely eroded may have the outer circumference substantially coincident with or located in the outer circumference of the wafer W. The other part of 30 may be located outside of the outer circumference of the wafer (W).

According to the plasma processing apparatus of the present invention, the outer circumference of the side protection ring is substantially coincident with or located inward of the outer circumference of the substrate placed on the mounting surface. In the plasma processing method according to the embodiment of the present invention, charged particles in the plasma accelerated in a direction perpendicular to the substrate surface placed on the mounting surface are prevented from entering the side protection ring. Thus, even if the side protection ring formed of a material different from that of the focus ring is used to cover the side of the lower electrode, the side protection ring does not substantially change plasma characteristics. As a result, even if the focus ring is severely eroded, desirable etching characteristics can be maintained without changing the plasma discharge conditions used in the conventional apparatus or method. In addition, the replacement period of the focus ring can be extended without changing the plasma discharge conditions used in the conventional apparatus or method, thereby reducing the cost of replacing the focus ring.

Claims (9)

Claims [1] A plasma processing apparatus comprising: a lower electrode having a supporting surface and a side electrode connected to an outer circumference of the mounting surface, the plasma processing apparatus processing a surface of a substrate to be mounted on the mounting surface by plasma; A focus ring made of quartz covering the periphery of the substrate to be mounted on the mounting surface; Covering the side of the lower electrode, made of a ceramic material different from the quartz, the outer periphery is provided with a side protection ring located inside the outer periphery of the substrate to be placed on the mounting surface Plasma processing apparatus. The plasma processing apparatus of claim 1, wherein the quartz and the ceramic material have different secondary electron emission coefficients. The plasma processing apparatus according to claim 1 or 2, wherein the erosion rate of the ceramic material by the plasma is lower than the erosion rate of the quartz. The plasma processing apparatus according to claim 1 or 2, wherein the ceramic material is alumina. delete By generating a plasma in a space of the lower electrode having a mounting surface and a side surface connected to an outer circumference of the mounting surface, the surface of the substrate to be mounted on the mounting surface facing the surface of the substrate to be processed. As a method of treatment, At the same time as covering the periphery of the substrate to be processed with a focus ring made of quartz, The side surface of the lower electrode is covered with a side protection ring made of a ceramic material different from the quartz so that the outer periphery is positioned inside the outer periphery of the substrate to be placed on the mounting surface, By the side protection ring, while preventing the plasma from contacting the side of the lower electrode, And said substrate to prevent charged particles accelerated in a direction perpendicular to the surface of said substrate to enter said side protection ring from said plasma. 7. The method of claim 6, wherein before the erosion of the focus ring by the plasma proceeds, the substrate and the focus ring prevent the plasma from contacting the side protection ring. Even after the erosion of the focus ring by the plasma progresses and the substrate to be processed and the focus ring cannot prevent the plasma from contacting the side protection ring, the plasma is prevented by the side protection ring. Preventing the contact with the side surface. 8. The plasma processing method according to claim 6 or 7, wherein the outer circumference of the side protection ring is positioned inside the outer circumference of the substrate to be processed mounted on the mounting surface. 8. The plasma processing method according to claim 6 or 7, wherein the substrate to be processed is a semiconductor substrate, and the processing is etching of an insulating film on the surface of the semiconductor substrate using a fluorocarbon plasma.

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