US20050061447A1

US20050061447A1 - Plasma etching apparatus

Info

Publication number: US20050061447A1
Application number: US10/945,779
Authority: US
Inventors: Yong-Dae Kim; Soon-Ho Yon; Do-hyeong Kim; Doo-Won Lee
Original assignee: Samsung Electronics Co Ltd
Current assignee: Samsung Electronics Co Ltd
Priority date: 2003-09-19
Filing date: 2004-09-20
Publication date: 2005-03-24
Also published as: KR20050028629A; KR100578129B1

Abstract

A plasma etch apparatus is disclosed. The plasma etch apparatus includes an electrostatic chuck for loading a wafer; an insulation portion surrounding the electrostatic chuck; and a focus ring disposed on the electrostatic chuck and the insulation portion. The focus ring has a concave-convex configuration.

Description

This application claims priority from Korean Patent Application No. 2003-65129, filed on Sep. 19, 2004, the contents of which are incorporated herein by reference in their entirety.

BACKGROUND OF THE INVENTION

1. Field of this Invention
This disclosure relates to an apparatus for fabricating semiconductor devices, and more particularly, to a plasma etching apparatus for fabricating semiconductor devices.
2. Description of Prior Art
A process of fabricating semiconductor devices includes etching a material layer formed on a semiconductor wafer using a predetermined etching apparatus. For example, an insulation layer is etched to form a contact hole using a predetermined etching apparatus. The etching apparatus can be classified as a dry etch apparatus or wet etch apparatus. Although the wet etch apparatus can treat a plurality of wafers at once, an etch process of forming the contact hole can't be proceeded in the wet etch apparatus due to isotropy of the wet etch. However, the dry etch apparatus can anisotropically etch a material layer using plasma. Thus, the dry etch apparatus can be used in an etch process of forming the contact hole.
The dry etch apparatus can be classified into physical dry etch apparatus and chemical dry etch apparatus. The physical dry etch apparatus employs a process of accelerating ions formed in a plasma by an electric field and impacting the ions with respect to the material layer. The physical dry etch apparatus has a superior anisotropic etch characteristic but a bad etch selectivity with respect to a layer under the material layer. However, the chemical dry etch apparatus etches the material layer using a chemical reaction radicals formed in the plasma. The chemical dry etch apparatus has a superior etch selectivity but a possibility of an isotropic etch characteristic. Recently, by combining all advantages of the physical and chemical dry etch apparatuses, an ion-enhanced plasma etch method, having superior etch selectivity and anisotropic etch characteristics, may be used for the purposes described above.
A dry etch apparatus employing a plasma, which may be conducted using plasma etch apparatus, has been disclosed in a Korean patent application number 10-1996-0020284. Generally, a plasma etch apparatus includes a reaction chamber and an upper electrode and a lower electrode that are disposed in the reaction chamber. The lower electrode is used as a susceptor when a wafer is loaded. The upper electrode is disposed over the lower electrode so that it is parallel to the lower electrode.
In the plasma etch chamber, after a wafer is loaded onto the susceptor, high-frequency power is supplied to the upper and lower electrodes while an etch gas is supplied into the reaction chamber. The etch gas is ionized between the upper and lower electrodes to from an etch gas in a plasma state used for etching a material layer located on the wafer.
However, as semiconductor devices become more highly integrated, the plasma etch apparatus is required to have a finer and more uniform etch characteristic and/or a faster etch rate. On the contrary, the plasma etch apparatus has a problem related to the formation of by-products. For example, in the case that silicon oxide is etched using a gas containing carbon and fluorine, such as CF₄or CHF₃, by-products containing carbon can be generated of a polymeric type. Most of the by-products are generally exhausted out of for the reaction chamber with a carrier gas, but some of the by-products which is not fully exhausted can pollute the reaction chamber.
The Korean patent application number 10-1996-0020284 discloses a method of using a material having a high thermal conductivity as a part of the process chamber in order to minimize pollution of the reaction chamber due to the by-products. However, as illustrated in FIG. 1A, this method can't effectively prevent an electrostatic chuck 150, a focus ring 110 surrounding the electrostatic chuck 150, cover rings 130 and 140 and a bottom supporter 120 from being polluted by the polymer-typed by-product 155, thereby causing a problem. FIG. 1B is a photograph showing an edge surface of the electrostatic chuck 150 exposed by decomposing the focus ring 110. As seen in FIG. 1B, much of the polymer-type by-product 155 is attached to the edge of the electrostatic chuck 150. This polymer-type by-product may cause a problem in that the photoresist can become damaged.
Usually, an etch process is performed using a photoresist pattern as a etch mask pattern. In the case that the by-product 155 is accumulated on the edge of the electrostatic chuck 150, the photoresist may be damaged in the plasma etch process by using the high-frequency power. For example, the photoresist may be boiled or burnt (Refer to FIGS. 1C and 1D).
The chance that the photoresist will become damaged will increase as time goes on, even after maintaining the plasma etch apparatus. When the focus ring 110 is dismantled for maintenance, much of polymer 155 attached on a surface of the electrostatic chuck 150 can occur as shown in FIG. 1 b. The damage to the photoresist causes a failure of a product. For this reason, a new plasma etch apparatus is required to have more stable etch characteristics.

SUMMARY

One feature of the present invention is to provide a plasma etch apparatus having more stable etch characteristics.
A plasma etch apparatus according to an embodiment of the present invention includes a focus ring. More particularly, the plasma etch apparatus includes an electrostatic chuck for loading a wafer in the apparatus; an insulation portion surrounding the electrostatic chuck; and a focus ring disposed on the electrostatic chuck and the insulation portion. A portion of the focus ring has a concave-convex configuration.
The electrostatic chuck may include a center portion having a diameter shorter than the diameter of the wafer; and a peripheral portion having a top surface lower than the center portion and surrounding the center portion. The insulation portion may include a bottom supporter surrounding the electrostatic chuck; and a cover ring spaced from the electrostatic chuck and disposed on the bottom supporter. The focus ring may cover at least a section of a top surface of the peripheral portion and an inner top surface of the cover ring and have at least one protruded portion or at least one groove.
Preferably, the cover ring includes an outer cover ring disposed on edge of a top surface of the bottom supporter; and an inner cover ring disposed between the outer cover ring and the focus ring. At this time, the inner cover ring may have an extension portion which extends to a bottom of the focus ring. A top surface and an outer sidewall of the outer cover ring form a curved section and a section of the outer cover ring includes a curved fan shape. A bottom surface of the outer cover ring may be lower than the inner cover ring. At this time, the outer cover ring and the inner cover ring may be formed of quartz or aluminum coated with yttrium oxide (Y₂O₃), and the focus ring may be formed of silicon.
According to an embodiment of the present invention, the insulation portion has a groove of a generally circle shape and the focus ring has a protruded portion of a generally circle shape fittingly engaged within the groove. Particularly, the inner cover ring has a groove of a generally circle shape and the focus ring has a protruded portion of a circle shape fittingly engaged within the groove.
According to another embodiment of the present invention, the focus ring has a groove of a circle shape and the insulation portion has a generally circular-shaped protruded portion fittingly engaged within the groove. The focus ring has a groove of a generally circular shape and the inner cover ring has a generally circular-shaped protruded portion fittingly engaged within the groove.
According to still another embodiment of the present invention, sections of the focus ring and the insulation portion have ripple patterns fittingly engaged with respect to each other. Sections of the focus ring and the inner covering have ripple patterns which are fittingly engaged with respect to each other.
The gap between the focus ring and the center portion ranges preferably from about 0.01 to about 0.2 mm. The gap between the focus ring and the insulation portion ranges preferably from about 0.01 to about 0.2 mm. The top surface of the inner ring is lower than the top surface of the electrostatic chuck by a distance of from about 0.1 mm to 0.7 mm. Furthermore, the top surface of the insulation portion may have a height equal to or lower than an utmost surface of the focus ring.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a cross-sectional view showing portions of a plasma etch apparatus according to certain conventional technology.
FIG. 1B is a photograph showing polymer-typed by-products attached to an electrostatic chuck of a plasma etch apparatus according to certain conventional technology.
FIGS 1C and 1D are photographs showing examples of process failures that may occur in a plasma etch apparatus according to certain conventional technology.
FIG. 2 is a diagram showing a plasma etch apparatus according to an embodiment of the present invention.
FIGS. 3 through 5 are cross-sectional views showing embodiments of a plasma etch apparatus having a focus ring according to the present invention.
FIGS. 6A, 7A, 8A and 9A are perspective views showing embodiments of a plasma etch apparatus having a focus ring according to the present invention.
FIGS. 6B, 7B, 8B and 9B are perspective views showing embodiments of a plasma etch apparatus having an inner cover ring according to the present invention.
FIG. 10 is a cross-sectional view showing a position of a focus ring composing a plasma etch apparatus according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIG. 2, a plasma etch apparatus 1 according to an embodiment of the present invention includes a reaction chamber 5 wherein a wafer W is loaded. The reaction chamber 5 provides a space where an etch process can be performed with respect to the loaded wafer W, and preferably includes a susceptor 10 where the wafer W is loaded and an upper electrode 20 disposed on the susceptor 10. The susceptor 10 and the upper electrode 20 each are generally cylindrically shaped. The reaction chamber 5 is preferably grounded through a ground line 9.
According to an embodiment of the present invention, the susceptor 10 is connected to a first high-frequency power source 42 generating high-frequency electric power of about 2 MHz through a first matcher and used as a lower electrode. Additionally, the susceptor 10 includes a predetermined temperature controller (not illustrated), for example, a heater (not illustrated) such as a ceramic heater or a cooler such as a coolant-circulation line. The wafer W loaded on the susceptor 10 can be kept to have a constant temperature due to the temperature controller. Preferably, the temperature controller is controlled by a predetermined automatic controller having a temperature sensor in order to automatically keep the temperature of the susceptor 10 constant.
In order to fix the wafer W, an electrostatic chuck 12 is disposed on the susceptor 10. According to an embodiment of the present invention, the electrostatic chuck 12 includes two polyimide films and a conductive thin layer interposed between the films. At this time, the conductive thin layer is connected to a direct current power source 45 having a high voltage located outside of the reaction chamber 5. When a predetermined voltage is applied on the conductive thin layer from the direct current power source 45 of high voltage, charges are generated at surfaces of the polyimide film to generate a coulomb force fixing the wafer W on the electrostatic chuck 12. However, a method of fixing the wafer W is not limited as the method of using the electrostatic chuck 12. The wafer W can be fixed using a mechanical device such as a clamp. Furthermore, the susceptor 10 can include at least three lift pins 14 penetrating the electrostatic chuck 12. The lift pins 14 function for moving the wafer W loaded in the reaction chamber 5 down to the upper surface of the electrostatic chuck 12.
Insulation portions 30 surrounding the electrostatic chuck 12 are disposed at the upper edges of the susceptor 10. The insulation portions 30 are generally ring shaped and are preferably formed of quartz. A focus ring 50 having a generally ring shape is disposed on a boundary between the insulation portions 30 and the electrostatic chuck 12. The focus ring 50 and the insulation portions 30 are explained in detail by referring to FIGS. 3 through 10.
The upper electrode 20 is parallel to the susceptor 10 and disposed on the electrostatic chuck 12. The upper electrode 20 is connected to a second high-frequency power source 44 generating an electric power of high frequency of about 60 MHz through a second matcher 43. At this time, a gap “h₁” between a bottom surface of the upper electrode 20 and an upper surface of the electrostatic chuck 12 preferably ranges in size from about 20 mm to about 40 mm for imparting superior etch characteristics. However, a bottom surface of the upper electrode 20 (i.e., a surface 22 adjacent to the electrostatic chuck 12) is preferably formed of silicon in order to stabilize atmosphere in the reaction chamber 5 for the etch process. At this time, the silicon preferably has a predetermined thickness so that a high-frequency power used for the plasma etch can penetrate the silicon. Furthermore, the upper electrode 20 may be formed of components including aluminum and anodized aluminum.
A gas inlet 23 is disposed on the upper electrode 20 in order to supply gas for the etch process. The gas inlet 23 is connected to a reaction gas supply source 47 through a gas supply line 46, a valve 48, and a mass flow controller (MFC) 49, which are disposed in the gas supply line 46 for controlling flow rate. The upper electrode 20 may be a path for supplying the reaction gas into the reaction chamber 5. For this, the upper electrode 20 includes a plurality of layers having a plurality of holes 25. At this time, a bottom layer 22 of the upper electrode 20, composing an inner wall of the reaction chamber 5, which is formed of silicon as described above. Consequently, the upper electrode 20 preferably has both shower head structure and hollow structure for a uniform distribution of the supplied gas.
The reaction chamber 5 is connected to a predetermined decompression device 7, such as a vacuum pump through an exhaust pipe 6 disposed within a predetermined region. Thus, the reaction chamber 5 can be maintained at a low inner pressure required for a superior etch characteristic. According to an embodiment of the present invention, an inner pressure of the reaction chamber 5 is preferably from about 10 to 100 mTorr, more preferably from about 15 to about 75 mTorr, and most preferably from about 25 to about 50 mTorr. A pressure sensor 8 monitors the inner pressure of the reaction chamber 5 and a controller 3 processes the result measured by the pressure sensor 8. The pressure sensor 8 may be disposed in the plasma etch apparatus 1. The decompression device 7 is controlled by the controller 3 analyzing the result measured by the pressure sensor 8 to keep an inner pressure of the reaction chamber 5 at a predetermined value.
A gate valve 52 is disposed on a sidewall of the reaction chamber 5, and a loadlock chamber 50 is connected to the gate valve 52. A wafer transfer arm 54 is disposed at the loadlock chamber 50. When the gate valve 52 is opened, gases in the loadlock chamber 50 are transferred into the reaction chamber 5 to make the pressure of the reaction chamber 5 equal to that of the loadlock chamber 50. Thus, in the case that the pressure of the loadlock chamber 50 is excessively higher than that of the reaction chamber 5, a decompression process of decreasing the inner pressure of the reaction chamber 5 may take too long a time. Thus, before opening the gate valve 52, the pressure of the loadlock chamber 50 should be preferably controlled to a level similar with that of the reaction chamber 5.
Next, a method of using the plasma etch apparatus describe above is briefly explained by referring to a process of etching a silicon oxide on a wafer to form a contact hole.
After decompressing the pressure of the loadlock chamber 50 to a value similar with that of the reaction chamber 5, the wafer W is loaded from the loadlock chamber 50 into the reaction chamber 5 using the wafer transfer arm 54. The wafer W is loaded on the lift pins 14 and, then onto the electrostatic chuck 12 by moving down the lift pins 14. Then, after the wafer transfer arm 54 is transferred out of the reaction chamber 5 to the loadlock chamber 50, the gate valve 52 is closed. The inner pressure of the reaction chamber 5 is decompressed to a predetermined value using the decompression device 7, and then a predetermined reaction gas is supplied into the reaction chamber 5 from the reaction gas supply source 47.
A high-frequency electric power is supplied by operating the second high-frequency power source 44 to ionize the reaction gas. Thus, a reaction gas having a plasma state is formed between the upper electrode 20 and the loaded wafer W. The ions of the reaction gas of the plasma state are projected onto the wafer W and on the electrostatic chuck 12 to etch the silicon oxide formed on the wafer W. The incidence rate of the plasma is controlled by a power supplied by the first high-frequency power source 42. At this time, in order to prevent the wafer from being damaged by an over voltage, the power supplied to the susceptor 10 may be less than that supplied to the upper electrode 20. After finishing the etch process, the wafer W is unloaded from the reaction chamber 5. The unloading process is preferably performed in reverse order of the loading process of the wafer, but individual unloading steps may be changed.
Referring to FIGS. 2 and 3, the electrostatic chuck 12 having a generally cylinder shape is disposed on the susceptor 10. The electrostatic chuck 12 includes a center portion 16, where the wafer W is loaded, and a peripheral portion 18 having a top surface which is at a lower level than the center portion 16.
The electrostatic chuck 12 is surrounded by the insulation portion 30 having the generally circular shape. The insulation portion 30 is generally formed of quartz but may be formed of aluminum oxide (Al₂O₃) and aluminum coated by yttrium oxide (Y₂O₃). According to an embodiment of the present invention, the insulation portion 30 may include a bottom supporter 37, an outer cover ring 34 and an inner cover ring 33.
The bottom supporter 37 is formed of quartz and surrounds the electrostatic chuck 12. The height of the top surface of the bottom supporter 37 may be lowered along an outer direction with respect to the electrostatic chuck 12. According to an embodiment of the present invention, the bottom supporter 12 has first, second and third upper surfaces 37 a, 37 b and 37 c of different relative levels. The first upper surface 37 a is at the highest level of the three upper surfaces 37 a, 37 b and 37 c, and is preferably at the same level as the peripheral portion 18. The outer cover ring 34 is disposed on the third upper surface 37 c at the lowest level of the three upper surfaces 37 a, 37 b and 37 c. The inner cover ring 33 is disposed on the second upper surface 37 b at an intermediate level.
The outer cover ring 34 is formed of quartz or yttrium oxide (Y₂O₃) and, as described above, is disposed on the third upper surface 37 c. An outer arcuate portion 34 a of the outer cover ring has a generally curved configuration. That is, an upper surface and an outer sidewall of the outer cover ring 34 form a generally curved line so that a cross-sectional view of the outer cover ring 34 has a generally curved shape.
The inner cover ring 33, which is formed of quartz or aluminum coated by yttrium oxide (Y₂O₃), and as described above, is disposed on the second upper surface 37 b at an intermediate height. Consequently, the inner cover ring 33 is disposed between the outer cover ring 34 and the bottom supporter 37. The inner cover ring 33 includes an extension portion 31 adjacent to the electrostatic chuck 12 and an exposure portion 32 whose upper surface is exposed. The upper surface of the extension portion 31 is at the same level as the first top surface 37 a. The upper surfaces of the extension portion 31, the peripheral portion 18 and the first top surface 37 a have substantially the same height. However, various embodiments at differing heights of these surfaces may be possible. The exposure portion 32 preferably has the same height as the upper portion of the outer cover ring 34 but is lower than the upper surface of the focus ring 50.
The focus ring 50 of the circle type is disposed on the extension portion 31, the peripheral portion 18 and the first top surface 37 a, respectively, to focus the plasma on the wafer W. The focus ring 50 is generally formed of silicon and may include an inner ring 51 and an outer ring 52 thicker than the inner ring 51.
According to an embodiment of the present invention, the focus ring 50 and the inner cover ring 51 have concave-convex structures fittingly engaged with respect to each other. According to a preferred embodiment of the present invention, a protruding portion 90 is disposed under the focus ring 50 and a complimentary groove 92 fittingly engaged to the protruding portion 90 is formed on the extension portion 31 (Refer to FIGS. 3, 6A and 6B). The protruding portion 90 and the groove 92 may be formed at the outer bottom surface of the focus ring 50 and on the outer surface of the extension portion 31 as illustrated in FIGS. 7A and 7B, respectively.
According to another embodiment of the present invention, a groove 92′ is formed at the bottom surface of the focus ring 50 and a protruding portion 90′ may be formed at the inner cover ring 51 (Refer to FIGS. 4, 8A and 8B). The groove 92′ and the protruded portion 90′ also preferably have a generally circular shape. According to another embodiment of the present invention, the focus ring 50 and the insulation portion 30 can have complimentary ripple patterns 97 which fittingly engage each other (Refer to FIGS. 5, 9A and 9B). Preferably, the ripple patterns 97 are formed under the outer ring 52 and on the extension portion 31. The distance from a top surface of the exposure portion 32 to an inner bottom surface of the focus ring 50 will be lengthened due to this concave-convex structural configuration. The inner cover ring 51 of the quartz is etched during the etch process to lower the top surface of the exposure portion 32. The etching by-products may be accumulated at a bottom surface of the focus ring 50, but the concave-convex structure minimizes accumulation of these by-products.
However, referring to FIG. 10 showing a cross-sectional view 88 adjacent to the inner ring 51 in order to explain the structure and arrangement of the focus ring 50 in more detail, a radius r₁of the center portion 16 is shorter than a radius r₂of the wafer W. Thus, an edge of the wafer W disposed on the electrostatic chuck 12 overlaps the center portion 16 a distance equal to the difference of the respective radii, i.e., r₂-r₁. At this time, a thickness h₂of the inner ring 51 is thinner than a difference h₃of height of the center portion 16.
According to an embodiment of the present invention, a gap hd between a bottom surface of the wafer W and a top surface of the inner ring 51 is preferably ranging from about 0.1 to about 0.7 mm. By decreasing the gap h_d, it is possible to reduce the strength of an electric field applied between the wafer W and the focus ring 50 in step of applying a high-frequency power to generate plasma. Thus, it is possible to minimize the occurrence of problems such as electric discharge due to a concentration of the electric field.
According to other embodiment of the present invention, in order to minimize stacking of the by-product, a gap 1 ₁between the center 16 and the inner ring 51 is preferably ranging from about 0.01 to about 0.2 mm. For the same reason, a gap between the focus ring 50 and the insulation portion 30 is also preferably ranging from about 0.01 to about 0.2 mm. Furthermore, a top surface of the outer ring 52 preferably has a height equal to or higher than a top surface of the wafer W loaded on the electrostatic chuck 12.
As described above, the plasma etch apparatus having a focus ring of a concave-convex structure according to the present invention may provide more stable etch characteristics. For example, although photoresists on 137 wafers were damaged in a conventional etch apparatus, photoresist on only 4 wafers were damaged in the present etch apparatus. Consequently, the plasma etch apparatus according to the present invention can minimize failure such as the damage of the photoresist during the etch process.
Accordingly, a focus ring included in the plasma etch apparatus of the present invention has a concave-convex structure. Thus, an overall path where by-products penetrate to a bottom surface of the focus ring is lengthened to minimize occurrence of problems such as electric discharge due to an accumulation of the by-products. Consequently, it is possible to fabricate a plasma etch apparatus having more stable etch characteristics.
A person skilled in the art will be able to practice the present invention in view of the description present in this document, which is to be taken as a whole. Numerous details have been set forth in order to provide a more thorough understanding of the invention. In other instances, well-known features have not been described in detail in order not to obscure unnecessarily the invention.
While the invention has been disclosed in its preferred embodiments, the specific embodiments as disclosed and illustrated herein are not to be considered in a limiting sense. Indeed, it should be readily apparent to those skilled in the art in view of the present description that the invention may be modified in numerous ways. The inventor regards the subject matter of the invention to include all combinations and sub-combinations of the various elements, features, functions and/or properties disclosed herein.
The following claims define certain combinations and sub-combinations, which are regarded as novel and non-obvious. Additional claims for other combinations and sub-combinations of features, functions, elements and/or properties may be presented in this or a related document.

Claims

1. An apparatus for plasma etching a wafer, comprising:

an electrostatic chuck for loading said wafer in the apparatus;

an insulation portion surrounding the electrostatic chuck; and

a focus ring having a circular shape disposed on the electrostatic chuck and the insulation portion,

a portion of the focus ring having a concave-convex configuration.

2. The plasma etch apparatus of claim 1, wherein the focus ring has a concave-convex configuration at the interface where the focus ring contacts the insulation portion.

3. The plasma etch apparatus of claim 1, wherein the electrostatic chuck comprises:

a center portion having a diameter shorter than the diameter of the wafer; and

a peripheral portion having a top surface lower than the center portion and surrounding the center portion.

4. The plasma etch apparatus of claim 3, wherein the insulation portion comprises:

a bottom supporter surrounding the electrostatic chuck; and

a cover ring spaced from the electrostatic chuck and disposed on the bottom supporter,

wherein the focus ring covers at least a section of the top surface of the peripheral portion and an inner top surface of the cover ring.

5. The plasma etch apparatus of claim 4, wherein the cover ring comprises:

an outer cover ring disposed on an edge of a top surface of the bottom supporter; and

an inner cover ring disposed between the outer cover ring and the focus ring,

wherein the inner cover ring has an extension portion which extends to a bottom of the focus ring.

6. The plasma etch apparatus of claim 5, wherein a top surface and an outer sidewall of the outer cover ring form a curved fan-shaped section.

7. The plasma etch apparatus of claim 5, wherein a bottom surface of the outer cover ring is disposed at a location lower than the inner cover ring.

8. The plasma etch apparatus of claim 5, wherein the outer cover ring is formed of quartz or aluminum coated with yttrium oxide (Y₂O₃), the inner cover ring is formed of quartz or aluminum coated with yttrium oxide (Y₂O₃), and the focus ring is formed of silicon.

9. The plasma etch apparatus of claim 1, wherein the insulation portion has a circular-shaped groove and the focus ring has a circular-shaped protruding portion fittingly engaged within the groove.

10. The plasma etch apparatus of claim 5, wherein the inner cover ring has a circular-shaped groove and the focus ring has a circular-shaped protruding portion fittingly engaged within the groove.

11. The plasma etch apparatus of claim 1, wherein the focus ring has a circular-shaped groove and the insulation portion has a circular-shaped protruding portion fittingly engaged within the groove.

12. The plasma etch apparatus of claim 5, wherein the focus ring has a circular-shaped groove and the inner cover ring has a circular-shaped protruding portion fittingly engaged within the groove.

13. The plasma etch apparatus of claim 1, wherein sections of the focus ring and the insulation portion have complementary configurations comprising ripple patterns which are fittingly engaged with respect to each other.

14. The plasma etch apparatus of claim 5, wherein sections of the focus ring and the inner cover ring have complementary configurations comprising ripple patterns which are fitting engaged with respect to each other.

15. The plasma etch apparatus of claim 1, wherein the focus ring includes at least one protruding portion or at least one groove.

16. The plasma etch apparatus of claim 3, wherein a gap between the focus ring and the center portion is from about 0.01 mm to about 0.2 mm.

17. The plasma etch apparatus of claim 1, wherein a gap between the focus ring and the insulation portion is from about 0.01 mm to about 0.2 mm.

18. The plasma etch apparatus of claim 1, wherein the focus ring includes an inner ring adjacent to the electrostatic chuck and an outer ring adjacent to the insulation portion, wherein a top surface of the inner ring is lower than a top surface of the electrostatic chuck by a distance of from about 0.1 to 0.7 mm.

19. The plasma etch apparatus of claim 1, wherein a top surface of the insulation portion is equal to or lower than an top surface of the focus ring.

20. An apparatus for plasma etching a wafer, comprising:

an electrostatic chuck for loading said wafer in the apparatus;

an insulation portion surrounding the electrostatic chuck;

a focus ring disposed on the electrostatic chuck and the insulation portion, at least a portion of the focus ring comprising a concave-convex configuration;

a center portion having a diameter shorter than the diameter of the wafer;

a peripheral portion having a top surface lower than the center portion and surrounding the center portion;

a bottom supporter surrounding the electrostatic chuck; and

a cover ring spaced from the electrostatic chuck and disposed on the bottom supporter.