TW201503281A - Plasma processing device and electrostatic chuck thereof - Google Patents

Abstract

The present invention discloses an electrostatic chuck, comprising an insulating layer embedded with electrodes for carrying semiconductor wafers, wherein the insulating layer has a main body portion and an annular flange extending outward along the sidewall level of the main body portion; a base located under the insulating layer; a binding layer located between the insulating layer and the base for binding the insulating layer and the base, wherein the annular flange exceeds the outer periphery of the binding layer; and an edge ring located above the annular flange, wherein a gap is arranged between the inner wall of the edge ring and the outer periphery of the main body portion, and partially overlaps the annular flange. The present invention can effectively prevent the damage on the electrostatic chuck caused by the bambardment of plasmas.

Description

Plasma processing device and its electrostatic chuck

The present invention relates to a semiconductor processing apparatus, and more particularly to an electrostatic chuck and a plasma processing apparatus having the same.

In recent years, with the development of semiconductor manufacturing processes, the integration and performance requirements of components are becoming higher and higher, and Plasma Technology plays an important role in the field of semiconductor manufacturing. Plasma technology is applied to many semiconductor processes by plasma generated by excitation of process gases, such as deposition processes (such as chemical vapor deposition), etching processes (such as dry etching), and the like. Generally speaking, in these processes, an electrostatic chuck (ESC) is generally used to fix, support and transport a semiconductor wafer to avoid a change or misalignment of the wafer during the process. The electrostatic chuck is usually disposed at the bottom of the chamber of the plasma processing apparatus, and is connected as a lower electrode to the RF power source, and a radio frequency electric field is formed between the upper electrode at the top of the chamber and the lower electrode, so that the electrons accelerated by the electric field are connected. The etching gas molecules entering the processing chamber undergo ionization collision, and the plasma that generates the process gas reacts with the wafer.

The electrostatic chuck uses electrostatic attraction to fix the semiconductor wafer. Compared with the mechanical chuck and the vacuum chuck, it can reduce the damage of the wafer caused by pressure, collision, etc., increase the area where the wafer can be effectively processed, and reduce the surface corrosion of the wafer. The deposition of particles, the wafer and the chuck can better conduct heat conduction, and can work in a vacuum environment. As shown in FIG. 1a, the prior art electrostatic chuck includes an insulating layer 10 and a pedestal 30, an edge ring 40. DC electrode layer 11 buried Hidden in the insulating layer 10, the electrostatic chuck utilizes a Coulomb force or a Johnsen-Rahbek force generated between the DC electrode layer 11 and the semiconductor wafer, so that the wafer is firmly adsorbed on the electrostatic chuck. Achieve the purpose of fixing the wafer. The susceptor 30 is used to support the insulating layer. The edge ring 40 encloses the semiconductor wafer for providing a relatively closed environment around the wafer. The insulating layer is generally made of a ceramic material, the base is generally made of a metal such as aluminum, and the surface of the base is covered with a protective film of chlorine dioxide, for example, and the edge ring 40 can be made of various materials such as alumina or other types of ceramics. The insulating layer 10 and the susceptor 30 are bonded by the adhesive 20, and the adhesive 20 (the reference numeral 20 in FIG. 1 is a bit sturdy, and the adhesive 20 is drawn in the form of a layer of material. The usual practice is generally silicone, with the insulating layer 10, the base 30 and the adhesive 20 having the same outer diameter.

However, when the plasma treatment process is performed, particularly in a treatment process performed at a high temperature, the electrostatic chuck is thermally expanded, and due to the difference in assembly and the difference in thermal expansion coefficients of the insulating layer 10, the adhesive 20 and the susceptor 30, The degree of thermal expansion is also different; in addition, the shear force generated by the susceptor 30 against the adhesive 20 during thermal expansion causes the adhesive 2 to expand beyond the insulating layer 30 and is no longer protected by the insulating layer, as shown in FIG. 1b. Shown. As a result, the adhesive 2 is easily attacked by the plasma. Since the binder 2 is usually doped with metal ions, arcing is likely to occur under the action of a strong electric field, and more serious will directly cause static electricity. Damage to the chuck is scrapped.

In order to solve this problem, in the prior art, by reducing the outer diameter of the adhesive 20, it is heated and expanded without exceeding the insulating layer to avoid the occurrence of arc discharge. However, this method is difficult to control the reduction of the outer diameter of the binder, and the process requirements are high.

SUMMARY OF THE INVENTION A primary object of the present invention is to overcome the deficiencies of the prior art and to provide an electrostatic chuck that is less susceptible to plasma damage.

In order to achieve the above object, the present invention provides an electrostatic chuck comprising: an insulating layer embedded with an electrode for carrying a semiconductor wafer, the insulating layer having a main body portion and an annular flange extending outward along a sidewall of the main body portion; Located below the insulating layer; a bonding layer between the insulating layer and the base for bonding the insulating layer and the base, wherein the annular flange extends beyond the periphery of the bonding layer And an edge ring located above the annular flange, the inner wall of the edge ring having a gap with the outer periphery of the body portion and partially overlapping the annular flange.

Preferably, the annular flange has a rectangular or L-shaped cross section.

Preferably, the bonding layer is concentric with the insulating layer and the diameter of the insulating layer is less than or equal to the diameter of the body portion.

Preferably, the annular flange is 0.5 to 3 mm beyond the outer circumference of the main body portion.

Preferably, the thickness of the annular flange is greater than or equal to one tenth of the thickness of the insulating layer.

Preferably, the edge ring is located at least 0.1 mm above the upper surface of the annular flange.

Preferably, the gap between the inner wall of the edge ring and the outer periphery of the main body portion is 0.1 to 2 mm.

Preferably, the outer periphery of the bonding layer is surrounded by an insulating shield that extends beyond the outer periphery of the insulating shield.

Preferably, the material of the insulating layer is ceramic, and the material of the bonding layer is silicone.

Preferably, the insulating protection member is an epoxy resin.

According to another aspect of the present invention, there is also provided a plasma processing apparatus having the above electrostatic chuck.

The invention has the beneficial effects that the annular flange structure of the insulating layer of the electrostatic chuck makes the bonding layer under the insulating layer always under the protection of the annular flange, and even if thermal expansion occurs, it is not exposed and is subjected to plasma bombardment to cause arc discharge. Even the destruction of the electrostatic chuck is caused. Therefore, the present invention can effectively improve the service life of the electrostatic chuck.

1‧‧‧plasma processing unit

10‧‧‧Insulation

11‧‧‧DC electrode layer

12‧‧‧ Main body

13‧‧‧Ring flange

20‧‧‧bonding layer

21‧‧‧Insulation protection

30‧‧‧Base

40‧‧‧Edge ring

2‧‧‧DC DC voltage source

3‧‧‧RF RF power source

P‧‧‧ plasma

1a is a schematic view of an electrostatic chuck in the prior art; FIG. 1b is a schematic view of a prior art electrostatic chuck after being thermally expanded; FIG. 2 is a schematic view of a plasma processing apparatus according to an embodiment of the present invention; 3b is a schematic view of the electrostatic chuck after being thermally expanded according to an embodiment of the present invention; and FIG. 4 is a schematic view of an electrostatic chuck according to another embodiment of the present invention.

In order to make the content of the present invention clearer and easier to understand, the contents of the present invention will be further described below in conjunction with the accompanying drawings. Of course, the invention is not limited to the specific embodiment, and general replacements well known to those skilled in the art are also encompassed within the scope of the invention.

2 shows a plasma processing apparatus 1 using an electrostatic chuck of the present invention provided by an embodiment of the present invention. It should be understood that the plasma processing apparatus 1 is merely exemplary, which may include fewer or more constituent elements, or the arrangement of the constituent elements may be different from that shown in FIG.

The plasma processing apparatus 1 includes an electrostatic chuck disposed within a chamber. A semiconductor wafer (not shown) is placed on the surface of the electrostatic chuck. Process gas source (not shown) to the chamber The process gas required in the plasma treatment process is supplied. An electrode 11 is embedded in the electrostatic chuck. The RF power source 3 is applied to the electrode 11, and a large electric field is generated inside the chamber, which excites electrons in the chamber to collide with gas molecules of the process gas to generate a plasma P. The DC DC voltage source 2 applies a high voltage DC power source to the electrode 11, causing a polarization charge on the surface of the electrostatic chuck, and further generating polarized charges of opposite polarities at corresponding positions on the surface of the semiconductor wafer, thereby passing through the semiconductor wafer and the electrostatic chuck Coulomb force or Jensen produced between. The force of Johnsen-Rahbek forces the wafer to be firmly attached to the electrostatic chuck. After the plasma processing is completed, the RF power source 3 is turned off, and a reverse DC voltage is applied to the electrode 11 through the DC DC voltage source 2 to release the semiconductor wafer from the electrostatic chuck.

3a and 3b are schematic views of an electrostatic chuck according to an embodiment of the present invention. Referring to FIG. 3a, the electrostatic chuck includes an insulating layer 10 and a base 30 and an edge ring 40. The insulating layer 10 and the base 30 are bonded by a bonding layer 20. The semiconductor wafer is placed on the upper surface of the insulating layer 10, and the shape of the insulating layer 10 conforms to the wafer and is generally circular. The insulating layer 10, the bonding layer 20, the base 30 and the edge ring 40 are concentrically disposed. The electrode 11 is embedded in the insulating layer 10, and an electrostatic force is generated between the semiconductor wafer and the insulating layer by applying a direct current power source, so that the wafer is firmly adsorbed on the electrostatic chuck. The insulating layer also typically includes a heating element that is applied to the heating element by an AC alternating current source to effect control of the wafer surface temperature. The insulating layer 10 is generally made of a ceramic material having high electrical resistivity, high thermal conductivity, and low radio frequency loss. It should be understood that the ceramic material may also be doped with materials such as tantalum carbide, aluminum nitride or aluminum oxide. The base 30 is used to support the insulating layer and is generally made of a metal material to facilitate the feeding of radio frequency energy. The surface of the base 30 is coated with a protective layer such as alumina. The insulating layer 10 and the susceptor 30 are bonded by a bonding layer 20, and the material of the bonding layer 20 may be a ruthenium adhesive.

In the present invention, the insulating layer 10 includes a body portion 12 and an annular flange 13 extending outwardly along the sidewall of the body portion 12, the annular flange 13 being formed on the lower surface of the electrostatic chuck. As shown in Figure 3b, the annular flange 13 extends beyond the outer periphery of the bonding layer 20 such that the diameter of the bonding layer 20 after thermal expansion is still less than the outer diameter of the annular flange 13, i.e., the bonding layer 20 does not exceed after thermal expansion. The outer periphery of the annular flange 13 such that the annular flange 13 can protect the bonding layer 20 from exposure. Wherein, the cross-sectional shape of the annular flange 13 may be a rectangle. In another embodiment of the invention, the annular flange 13 may also have a downwardly extending projection, the annular flange 13 having an L-shaped cross-sectional shape, which has the advantage that the side walls of the bonding layer 20 can be further shielded. Of course, the cross section of the annular flange may have other shapes, and the invention is not limited thereto. Preferably, the diameter of the bonding layer 20 is slightly smaller than or equal to the diameter of the insulating layer main body portion 12, and the annular flange 13 extends beyond the outer peripheral edge of the main body portion 12. In practical work, the specification of the semiconductor wafer is, for example, 200 mm, 300 mm or 450 mm or other dimensions, and the shape of the insulating layer 10 conforms to the wafer, and the annular flange 13 is 0.5 to 3 mm beyond the outer circumference of the main body portion 12 to achieve the shadow bonding. The purpose of layer 20. Further, the thickness of the annular flange 13 is not less than one tenth of the overall thickness of the insulating layer 10. When the plasma reaction is performed to cause thermal expansion of the electrostatic chuck, although the degree of expansion of the bonding layer 20 is greater than the degree of expansion of the insulating layer 10 due to the difference in thermal expansion coefficient of each portion of the electrostatic chuck, the annular flange by the insulating layer 13, the bonding layer 20 is still not exposed under the protection of the annular flange 13, and therefore, the plasma bombardment does not reach the bonding layer 20, thereby effectively avoiding the occurrence of arc discharge. In addition, it should be noted that the processing steps of the electrostatic chuck of the present invention are different from the prior art in that the insulating layer is disposed after the bonding layer 20 is coated on the upper surface of the base, and the bonding layer 20 is not required to have a radial dimension. For the reduced control, for the case where the diameter of the bonding layer 20 is slightly smaller than that of the insulating layer, it is only necessary to scrape off a thin outer layer of the bonding layer 20 after the bonding layer 20 is applied, and the process steps are relatively simple and convenient.

With continued reference to FIG. 3a, the edge ring 40 is disposed over the annular flange 13 of the insulating layer. The edge ring 40 is made of a non-metal material that surrounds the semiconductor wafer for providing a relatively closed environment around the wafer to improve plasma uniformity across the wafer surface while also avoiding plasma on the back side of the wafer edge. The effects of the body treatment process cause pollution. There is a gap between the inner wall of the edge ring 40 and the outer periphery of the insulating layer main body portion 12, and the gap can be used to prevent damage between the edge ring 40 and the semiconductor wafer due to the difference in thermal expansion coefficient; The edge ring 40 has a portion overlapping the annular flange 13 in the vertical direction. As shown in FIG. 3b, when thermal expansion of the electrostatic chuck occurs, the bonding layer 20 is still under the protection of the annular flange 13, and the overlapping portion of the edge ring 40 and the annular flange 13 further blocks the plasma from the annular flange 13. The bonding layer 20 is externally reached to effectively avoid the occurrence of arc discharge. In a preferred embodiment, the edge ring 40 is located at least 0.1 mm above the upper surface of the annular flange 13, and the gap between the inner wall of the edge ring and the outer periphery of the body portion is 0.1 to 2 mm.

Please continue to refer to FIG. 4, which is a schematic diagram of an electrostatic chuck according to another embodiment of the present invention. The electrostatic chuck includes an insulating layer 10 in which the electrode 11 is buried and a base 30, and the insulating layer 10 and the base 30 are bonded by a bonding layer 20. The material of the bonding layer 20 may be a tantalum adhesive. The outer periphery of the bonding layer 20 is also surrounded by a thinner insulating shield 21 for sealing the exposed side walls of the bonding layer 20. The material of the insulating shield 21 is, for example, an epoxy resin. When the plasma reaction is performed and the electrostatic chuck is thermally expanded, the bonding layer 20 is still protected by the annular flange 13, and therefore, the plasma bombardment does not reach the bonding layer 20. In addition, the insulating shield 21 further forms an additional sealing layer that further prevents the bonding layer 20 from being exposed to the plasma environment. Preferably, the annular flange 13 extends beyond the outer periphery of the insulating shield 21 such that the bonding layer 20 and the insulating shield 21 are not covered beyond the outer periphery of the annular flange 13 by thermal expansion and are obscured by the annular flange 13. Further, the edge ring 40 is provided above the upper surface of the annular flange 13 of the insulating layer, and a gap exists between the inner wall of the edge ring 40 and the outer peripheral edge of the insulating layer main body portion 12, overlapping the portion of the annular flange 13. Since the arrangement of the edge ring 40 is similar to that of the first embodiment of the present invention, it will not be described herein.

In summary, in the present invention, by using an insulating layer having an annular flange structure in the electrostatic chuck, even in the plasma processing process, even if the electrostatic chuck is thermally expanded, the bonding layer of the bonding insulating layer and the base is still It is possible to avoid the range in which the plasma reaches and avoid arcing due to bombardment of the plasma. Therefore, the present invention improves the defects in the prior art that the adhesive layer is exposed due to thermal expansion mismatch, thereby causing arc discharge, causing damage to the electrostatic chuck, and effectively improving the service life of the electrostatic chuck.

The present invention has been described in terms of the preferred embodiments of the present invention, and the present invention is intended to be illustrative only, and is not intended to limit the scope of the invention. In the case of a number of changes and refinements, the scope of protection claimed in the present invention shall be as defined in the claims.

10‧‧‧Insulation

11‧‧‧DC electrode layer

12‧‧‧ Main body

13‧‧‧Ring flange

20‧‧‧bonding layer

30‧‧‧Base

40‧‧‧Edge ring

Claims (11)

An electrostatic chuck for a plasma processing apparatus, comprising: an insulating layer embedded with a DC electrode for carrying a semiconductor wafer, the insulating layer having a body portion and an annular flange extending outward along a sidewall of the body portion; Located below the insulating layer; a bonding layer between the insulating layer and the base for bonding the insulating layer and the base, wherein the annular flange extends beyond the periphery of the bonding layer And an edge ring located above the annular flange, the inner wall of the edge ring having a gap with the outer periphery of the body portion and having a partial overlap with the annular flange in a vertical direction. The electrostatic chuck according to claim 1, wherein the annular flange has a rectangular or L-shaped cross section. The electrostatic chuck according to claim 2, wherein the bonding layer is disposed concentrically with the insulating layer and the diameter of the insulating layer is less than or equal to a diameter of the body portion. The electrostatic chuck according to claim 3, wherein the annular flange is 0.5 to 3 mm beyond the outer circumference of the body portion. The electrostatic chuck of claim 1, wherein the annular flange has a thickness greater than or equal to one tenth of a thickness of the insulating layer. The electrostatic chuck of claim 1, wherein the edge ring is located on an upper surface of the annular flange At least 0.1 mm above. The electrostatic chuck according to claim 1, wherein a gap between the inner wall of the edge ring and the outer periphery of the main body portion is 0.1 to 2 mm. The electrostatic chuck of claim 1, wherein an outer periphery of the bonding layer is surrounded by an insulating shield that extends beyond an outer circumference of the insulating shield. The electrostatic chuck according to claim 1, wherein the material of the insulating layer is ceramic, and the material of the bonding layer is silicone. The electrostatic chuck of claim 7, wherein the insulating shield is an epoxy resin. A plasma processing apparatus having a plasma processing chamber containing the electrostatic chuck described in claims 1-10.