KR20040005968A - Hollow anode plasma reactor and method - Google Patents

Abstract

The plasma processing apparatus according to the present invention includes a plasma chamber, a first electrode, a second electrode, and a plasma suppression apparatus. The plasma suppression device has a plurality of slots and is electrically connected to the first electrode. The suppressor functions to confine the plasma in the interelectrode space while maximizing the process gas flow as much as possible. When plasma is generated by applying an electric field to the process gas in the inter-electrode space, the suppressor electrically confines the plasma to the inter-electrode space without significantly limiting gas flow from the inter-electrode space.

Description

Anode plasma reactor and method {HOLLOW ANODE PLASMA REACTOR AND METHOD}

Dry etching processes may be used in semiconductor wafer processes that remove material from the film deposited on the wafer or by exposure to the plasma, or from the wafer surface. The plasma is electrically neutral and partially ionized. In addition to generating plasma, the etch reactor can control chemical / physical reactions occurring on the film surface or on the wafer. Through the etching process, the material is removed from the wafer or the film surface of the etch area to form a profile and size that partially creates the circuit elements.

In known plasma reactors, plasma is formed in the space adjacent to the wafer, extending to fill most or all of the reactor chamber total volume. The plasma reacts with every surface that the plasma contacts. Outside the space adjacent to the wafer, the reaction between the plasma and the wall can produce unwanted results. For example, sputtering of wall material, or, more commonly, deposits can occur on or near the wall. As the wall deposit continues to increase in thickness, the wall deposits can peel off, creating contaminating particles. In addition, because the wall deposits have different electrical and chemical properties than the walls themselves, the deposits can change the way the plasma reacts to the wall and can change the plasma properties over time. Therefore, wall deposits must be removed periodically. While in-situ plasma cleaning is preferred, this cleaning method is often difficult or very slow due to the low energy of some plasma-wall interactions. Thus, manual cleaning of the reactor is often required, which results in cost and lowers system productivity.

1 is a side cross-sectional view of a conventional plasma reactor. The apparatus utilizes a chamber housing 110 forming a reactor or chamber 100. The first electrode 112 is positioned on the housing 110. As shown, the first electrode 112 and the housing 110 are electrically connected to the ground portion 134. The second electrode 114 is disposed below the housing 110 and lies opposite and parallel to the upper electrode 112. The second electrode 114 is electrically isolated from the housing 110 by the insulator ring 116. The substrate or wafer 118 to be etched is located on the inner side of the second electrode 114 which is set as a clamping or cooling device. Wafer 118 is surrounded by a thin plate 120 made of an insulating material, such as quartz.

The etchant gas is supplied to the reactor 100 by an etchant gas source 122 and a supply line 124. The supply line 124 is connected to the reactor 100 through the port along the first electrode 112 to carry etchant gas into the reactor 100. Low pressure is maintained in the reactor 100 by the vacuum pump 128, which is connected to the reactor 126 via the vacuum line 126. RF power is supplied to the second electrode 114 using the RF power source 130 and the impedance matching network 132. When the etchant gas is maintained at a suitable low pressure in the reactor 100 and the appropriate RF power is supplied to the second electrode 114, the inter-electrode space between the first electrode 112 and the second electrode 114 ( Plasma is formed in 146 and spreads out of the space 142 outside the first and second electrodes 112 and 114. The plasma gas in this space 142 may interact with the exposed inner wall 144 of the chamber housing 110.

Attempts have been made to confine the plasma to a portion adjacent to the wafer 118. Some known devices use two or more annular rings 150 near the interelectrode space 146 between two parallel disk electrodes, as in FIG. Several annular rings 150 are added to the reactor 100 of FIG. 1 to fill the space between the upper electrode 112 and the lower electrode 114 about its circumference. The annular ring 150 is made of quartz-like non-conductor and there is a small gap 152 between the rings. This spacing allows gas to flow from the interelectrode space 146 to the outer space 148 and to the vacuum pump 128. This spacing 152 is sufficiently narrow and the width of the annular ring 150 is wide enough so that there is a significant loss of gas flow through the small spacing 152. This gas flow loss creates a pressure difference between the interelectrode space 146 and the outer space 148. The plasma generated in the interelectrode space 146 is confined to the interelectrode space 146 due to the ultra low pressure and the narrow space 152 present in the outer space 148.

The plasma limited approach is problematic in that the process window is limited. In low pressure plasma operating environments (eg, less than 60 mTorr), the effect of the annular ring 150 may not always establish a beneficial pressure drop. In addition, in cases where plasma is confined, the small gas flow generated by the annular ring 150 limits the gas flow rates that are available.

FIELD OF THE INVENTION The present invention relates to integrated circuit fabrication, and more particularly, to apparatus and methods for removing material from surfaces.

1 is a side cross-sectional view of a known art reactor.

2 is a side cross-sectional view of a second known technology reactor.

3 is a cross-sectional side view of a preferred embodiment.

4 is a cross-sectional plan view taken along line 2-2 of FIG.

5 is a flow chart of FIG. 3.

6 is a side cross-sectional view of another preferred embodiment.

7 is a side cross-sectional view of another preferred embodiment.

8 is a side cross-sectional view of another preferred embodiment.

9 is a plan sectional view taken along line A-A of FIG.

10 is a cross sectional plan view taken along line A-A of the preferred embodiment of FIG.

If the plasma can be confined to a space near the wafer, there are several advantages, such as improved process stability and repeatability, less system management burden. Therefore, there is a need for a method and apparatus that confine plasma to a space near the wafer while not significantly limiting the flow rate and pressure.

Preferred embodiments of the apparatus and method of the invention described below minimize the surface area to which the plasma reacts while confining the plasma in the space near the wafer. Preferred embodiments provide a high gas flow out of the interelectrode space. Preferred apparatus and methods utilize localized methods that localize the electric field in the plasma region of the chamber. Preferred apparatus and methods may be individual parts of several plasma processing systems, or may be integrated into several plasma processing systems. Preferred apparatus and methods minimize plasma-wall interactions, reduce system management burden, improve processing stability, and reduce intersystem variation.

According to FIGS. 3 and 4, the device preferably uses a chamber housing 202 forming a reactor or chamber 200. The first electrode 210 is disposed on the chamber housing 202. In one preferred embodiment, the first electrode 210 may be made of silicon (Si) or silicon carbide (SiC) having a disk shape and having an electrical resistance of less than 1 ohm / cm. The first electrode 210 and the chamber housing 202 are connected to the ground portion 254. The second electrode 220 is disposed below the chamber housing 202 and is disposed opposite to and parallel to the first electrode 210. It is preferable that the second electrode 220 takes the form of a disk. In alternative embodiments, the first and second electrodes 210, 220 may assume different forms and may be made of different materials. Preferably, the distance between the first and second electrodes 210 and 220 can be adjusted manually or automatically. In addition, it is preferable that the second electrode 220 is electrically insulated from the chamber housing 202 by the insulator ring 230, and the insulator ring 230 is made of a non-conductive solid material such as quartz (SiO 2) or alumina (Al 2 O 3). Is made. The substrate or wafer 232 to be etched is supported at the inner surface or surface of the second electrode 220, and the second electrode 220 is provided with the fixing means and the temperature of the wafer 232 to fix the wafer 232 to the inner surface. It is preferable to function as a control means for controlling. This fixed and temperature control means is a liquid used with a helium (He) gas arranged between the wafer 232 and the second electrode 220 to improve thermal conductivity between the wafer 232 and the second electrode 220. Cooled and electrostatically fixed second electrode 220 may be included. A focus ring 234, made of an insulator material such as quartz (SiO 2), is set around the wafer 232. In alternative embodiments, focus ring 234 may be made of two concentric adjacent rings. That is, it may be composed of an inner ring made of silicon (Si) or silicon carbide (SiC) and an outer ring made of quartz (SiO 2). In another embodiment, the focus ring 234 may take many different forms and be made of different materials.

An etchant gas is supplied to the chamber 200 via an etchant gas source 240 and a supply line 242. Supply line 242 is preferably connected to chamber 200 through one or more ports passing through first electrode 210. Thus, the etchant gas can be uniformly spread in the interelectrode space 260. The gases are discharged from the chamber 200 and the vacuum pressure is maintained by the vacuum pump 246. The vacuum pump 246 is preferably connected to the reactor by a vacuum line 244. RF power is preferably supplied to the second electrode 220 by an RF power source 250 connected to the second electrode 220 through the impedance matching network 252.

The outer edge of the first electrode 210 is bent downward to form a cylindrical wall or "shroud" 212 with respect to the interelectrode space 260. The curtain 212 has a lower surface portion 262 adjacent to the top 208 of the chamber 200 or the surface of the focus ring 234. The bottom surface 262 of the curtain 212 establishes electrical connections with the upper edge of the chamber 200. The electrical connection is shorter in RF conduction from the RF power source 250 to ground 254 as compared to the conduction path from the RF power source 250 to ground 254 through the wall 204 of the chamber 200. Create a route. The curtain 212 minimizes the closed electric and magnetic fields within the outer chamber space 206 and improves plasma confinement.

The curtain 212 has a plurality of holes or vertical slots 214 passing through the curtain 212 and allows the etchant gas in the interelectrode space 260 to be discharged. The vertical slot 214 takes the vertical direction and its width is 0.8-3.0 mm. In an alternative preferred embodiment, the vertical slot 214 can assume many different shapes and can have different widths.

The number, shape, size of the vertical slots 214 and the thickness of the curtain 212 are selected to obtain the desired gas flow rate or gas residence time in the interelectrode space 260. It is also chosen in such a way as to interfere with plasma localization. In a preferred embodiment, the vertical slot 214 includes 180 vertical slots with a width of 2.5 mm and an inter-electrode spacing of 20 mm. The wall thickness of the curtain 212 is 6 mm. In other embodiments, the size, number, shape of the holes may vary, and the thickness of the curtain 212 may likewise vary.

Plasma is formed in the interelectrode space 260 when the etchant gas is placed at an appropriate pressure level in the interelectrode space 260 and the appropriate RF power is supplied to the second electrode 220. The plasma is confined by the envelope 212, and the plasma-surface interaction is limited to a relatively small area. In an embodiment capable of etching a 200 mm wafer, the curtain 212 has a height in the range of 14-25 mm. The tabernacle 212 has an inner diameter of 220 mm and an outer diameter of 235 mm. The vertical slot 214 has a width of 2.0 mm and a length of 12 to 24 mm and is spaced by 2.0 degrees. In the above embodiments, the first electrode 210 and the single film 212 is made of silicon (Si) or silicon carbide (SiC). Moreover, 3000 Watt 27 MHz Rf power was used with 3000W 2 MHz RF power. In another embodiment, including those embodiments that can etch a 200 mm or 300 mm wafer, the width, diameter, size of the vertical slots, and materials that can be used to make the curtain 212 can vary. Moreover, frequency and RF power levels may also vary.

In operation, the wafer 232 is located on the inner surface of the second electrode 220 as in step 502 of FIG. Chamber 200 is evacuated (504). Fixing means, such as a wafer anchoring ring or electrostatic charge, secures the wafer 232 to the second electrode 220. Process gas is supplied 506 through the distribution source 240. Process gas enters the interelectrode space 260 through a gas supply line 242 and a distribution device (eg, a showerhead). The interelectrode space 260 pressure selection can be obtained by controlling the rate of gas removal or process gas inlet. Pumps, such as mechanical vacuum pumps (eg, turbopumps), remove process gas from the interelectrode space 260 through the discharge port and vacuum line 244.

RF power is supplied to the second electrode 220 to generate a high energy electric field in the interelectrode space 260 and generate a plasma (508). The plasma then reacts with the exposed surface of wafer 232 (510). The steps shown in FIG. 5 may be reversed and additional steps may be included.

The curtain 212 blocks the electric field formed in the interelectrode space 260 and prevents the electric field from penetrating into the outer chamber space 206. Vertical slots 214 in the curtain 212 allow the process gas to flow between the interelectrode space 260 and the vacuum line 244 with minimal pressure loss, thus achieving high flow rates at low treatment pressures.

In some embodiments, the curtain 212 effectively modifies the electric field near the wafer 232 and modifies the process. In some oxide etching devices, the barrier film 212 increases the etch rate at the outer edge of the wafer 232. One advantage of this embodiment is that the etch rate is uniform between the wafers 232.

If the curtain 212 terminates the electric field near the perimeter of the interelectrode space 260 and exhibits limited resistance to gas flow, the curtain 212 includes a structure to achieve this function. Thus, the curtain 212 is not limited to a containment structure having only vertical slots 214. In an alternate embodiment, the curtain 212 includes horizontal slots parallel to the inner surfaces of the first and second electrodes 210, 220. The curtain 212 includes any suitable arrangement and combination of holes, slots, gaps, channels, etc. (with a uniform or non-uniform cross section) that flows the process gas from the inter-electrode space 260 to the vacuum line 244. You may. It is preferable that the curtain 212 can obtain the maximum gas flow rate. Furthermore, because the curtain 212 is at ground potential, the size of the first electrode 210 can be reduced without changing the electrical state of the plasma formed in the inter-electrode space 260.

From the foregoing, it can be seen that the curtain 212 may be a single portion of the first electrode 210 and may be separated from the first electrode 210, but is electrically connected to the first electrode 210. . It is preferable that the curtain 212 is mobile. That is, it is desirable that the curtain 212 can be raised or lowered manually or automatically with respect to the second electrode 220 while the apparatus and method are in operation. As in FIG. 6, the curtain 212 is physically spaced from the first electrode 210 and mechanically and electrically coupled to the plate 217. Three or more lift pins 218 are equally attached around the plate 217 and help raise and lower the tabernacle 212. Six or more flexible conductive straps 219 provide electrical contact between the plate 217 and the chamber 200. In a preferred embodiment, when the curtain 212 moves to the lowest position, the bottom 216 of the curtain 212 establishes mechanical and electrical contact with the upper side 208 of the chamber 200. This contact is from RF power source 250 to ground 254 as compared to the RF reverse path from RF power source 250 to ground 254 including the wall 204 of chamber 200. Create a shorter RF reverse path. This short conduction path towards ground 254 minimizes field strength in the outer chamber space and improves plasma confinement.

As shown in FIG. 7, the curtain 212 is physically spaced apart from the first electrode 210 and electrically and mechanically connected to the lower half of the chamber 200 near the second electrode 220. The bottom 216 of the curtain 212 is mechanically and electrically connected to the conductive ring 213. The conductive ring 213 is mechanically and electrically connected to the upper side 208 of the chamber 200.

FIG. 8 is an alternative embodiment diagram of a curtain 450 included in a plasma reactor including two electrodes that are independently RF powered. Such reactors are also called "triodes". That is, it has two RF electrodes and one ground plane. 8, 9, and 10, the triode reactor 400 is composed of a chamber 402, an upper electrode 410, and a lower electrode 420. Chamber 402 is electrically connected to ground 420. The upper electrode 402 is electrically isolated from the chamber 402 by the upper insulator ring 414. The upper electrode 410 has a plate 412 of silicon (Si), silicon carbide (SiC), or other suitable material that is electrically and mechanically connected to the inner surface of the chamber 402. The upper electrode 410 is connected to the RF power source 444 through an impedance matching network 446.

The lower electrode 420 is electrically isolated from the chamber 402 by the lower insulator ring 422, and provides electrical and mechanical non-cooling of the substrate or wafer 424 located on the inner surface of the lower electrode 420 as described above. Means for; Focus ring 426 made of an insulating material is located around wafer 424. RF power is supplied to the lower electrode 420 by an RF power source 440 and an impedance matching network 442.

An etchant gas is supplied to the reactor 400 using an etchant gas source 430 and a supply line 432. Supply line 432 is connected to reactor 400 through one or more ports through top electrode 410 such that etchant gas is uniformly delivered to inter-electrode space 460. Gases are discharged from the reactor 400 and the vacuum level is maintained in the chamber 402 by the vacuum pump 434. Vacuum pump 434 is connected to reactor 400 via vacuum line 436.

The tabernacle 450 is located in an annular space around the lower electrode 420, and forms a barrier between the interelectrode space 460 and the space 404 in which the curtain 450 is located in the lower half of the chamber 402. . The tabernacle 450 is electrically and mechanically connected to the chamber 402 at the inner and outer peripheral portions of the tabernacle 450. Shroud 450 includes a plurality of slots or holes 452, through which the process gas can easily move, but their size effectively blocks all electric fields formed within plasma space 460. Should be sufficient. Thus, substantially no electric field is present in the lower portion 404 of the chamber 402. The width of this slot 452 is 0.8-3.0 mm, and the thickness of the curtain 450 is 6-12 mm. The direction of the slot 452 may extend radially, circumferentially, or in any other suitable direction.

As in FIGS. 9 and 10, the serm 450 slots extending radially and circumferentially, respectively, are aligned with the radial slots and the circumferential slots 456 of the cover plate 454. As in FIGS. 9 and 10, the curtain 450 may be a monolithic piece of cover plate 454, and in some embodiments the curtain 450 and cover plate 454 may be separate components. Slot 456 of cover plate 454 is aligned with slot 452 of tabernacle 450. Cover plate 454 is made of silicon (Si), silicon carbide (SiC), or other suitable material.

Claims (42)

As a plasma processing apparatus, this apparatus, -Earthing, A vacuum chamber connected to the ground, A first electrode disposed in the vacuum chamber having a planar surface facing inside the vacuum chamber connected to the ground, A second electrode of the vacuum chamber having a planar surface parallel to and adjacent to the first electrode, A power source connected to the second electrode, and A suppression device located along the circumference of the first and second electrodes in the vacuum chamber, comprising a membrane having a plurality of apertures which facilitates gas flow and is electrically connected to the ground; Skirting suppressor Plasma processing apparatus comprising a. The plasma processing apparatus of claim 1, wherein the suppression apparatus comprises a unitary part of the first electrode. The plasma processing apparatus of claim 1, wherein the suppression apparatus comprises an integrated part of the first electrode. The plasma processing apparatus of claim 1, wherein the suppressor is located adjacent to the second electrode. The plasma processing apparatus of claim 1, wherein the holes of the suppression apparatus include vertical slots. The plasma processing apparatus of claim 1, wherein the plurality of holes of the suppression apparatus include horizontal slots. 10. The plasma processing apparatus of claim 1, wherein the suppression device is adjustablely positioned relative to the second electrode such that the suppression device can be moved near or away from the planar surface of the second electrode. As an etching apparatus, this apparatus, -Earthing, A plasma chamber connected to the ground, A vacuum pump connected to the plasma chamber, A process gas source connected to the plasma chamber, A first electrode having a planar surface facing inside the plasma chamber and connected to the ground, A second electrode having a planar surface facing parallel to the first electrode, A power supply connected to the second electrode, An interelectrode region disposed between the first and second electrodes, and A suppression device enclosed within the plasma chamber and electrically connected to the first electrode, the apparatus comprising: a plurality of slots configured to facilitate gas flow between the fluid path and the interelectrode region terminating at the vacuum pump input, and confining the electric field to the interelectrode region Restraining device having a conductive section Etching apparatus comprising a. 9. An etching apparatus according to claim 8, wherein the slots of the suppressor comprise vertical slots extending between the planar surfaces of the first and second electrodes. 9. An etching apparatus according to claim 8, wherein the slots of the suppression apparatus comprise horizontal slots. 9. An etching apparatus according to claim 8, wherein said suppression apparatus is set to confine the plasma in the suppression apparatus. 9. An etching apparatus according to claim 8, wherein said suppression apparatus is mechanically connected to the first electrode. 9. An etching apparatus according to claim 8, wherein said suppression apparatus comprises a unitary part of a first electrode. 9. The etching apparatus of claim 8, wherein the suppressor is set to confine the plasma to the interelectrode region with minimal constraints on the gas flow between the interelectrode region and the remaining chamber space. 9. The etching apparatus of claim 8, wherein the fluid path is further defined by an inner chamber wall and an exhaust port. 9. An etching apparatus according to claim 8, wherein said suppression apparatus is located around an edge of the first electrode. 9. An etching apparatus according to claim 8, wherein said suppression apparatus is located around the edges of the first and second electrodes. 9. An etching apparatus according to claim 8, wherein said slots have a uniform cross section. 9. An etching apparatus according to claim 8, wherein said slots have a non-uniform cross section. 9. An etching apparatus according to claim 8, wherein said power supply source is a radio frequency (RF) power supply source. 9. An etching apparatus according to claim 8, wherein said power source is two RF power sources with different RF ratings. 23. The etching apparatus of claim 21, wherein the frequency ratings of the two RF power sources are 2 MHz and 27 MHz. 9. An etching apparatus according to claim 8, wherein the surface of the first electrode is made of silicon. 24. The etching apparatus of claim 23, wherein the silicon has an electrical resistance of less than 1 ohm / cm. 9. An etching apparatus according to claim 8, wherein the first electrode surface is made of silicon carbide (SiC). The etching apparatus according to claim 25, wherein the electrical resistance of the silicon carbide (SiC) is less than 1 ohm / cm. As an etching apparatus, this apparatus, -Earthing, A plasma chamber connected to the ground, A vacuum pump connected to the plasma chamber, A process gas source connected to the plasma chamber, A first electrode having a surface facing inside the plasma chamber, A second electrode having a surface parallel to and adjacent to the first electrode and facing inside the plasma chamber, A first power supply connected to the first electrode, A power supply connected to the second electrode, An interelectrode region disposed between the first and second electrodes, and A suppression device enclosed within the plasma chamber and electrically connected to the ground, comprising: a suppression having a plurality of slots set to promote gas flow between the vacuum pump and the interelectrode region, and a conducting portion to confine the electric field to the interelectrode region; Device Etching apparatus comprising a. 28. The apparatus of claim 27, wherein the etching apparatus further comprises a vacuum line, wherein the suppression apparatus comprises an annular apparatus disposed adjacent the second electrode to space the inter-electrode region from the vacuum line. Etching apparatus. 28. The etching apparatus of claim 27, wherein the slots of the suppressor comprise radially extending slots. 28. The etching apparatus of claim 27, wherein the slots of the suppressor comprise circumferentially extending slots. 28. The etching apparatus according to claim 27, wherein said suppression apparatus is set to electrically confine plasma to an interelectrode region. 28. The etching apparatus of claim 27, wherein said suppression apparatus is mechanically connected to a plasma chamber. 28. The etching apparatus of claim 27, wherein said suppression apparatus is set to confine the plasma with minimal gas flow restriction between the inter-electrode region and the remaining chamber space. 28. The etching apparatus of claim 27, wherein said slots have a uniform cross section. 28. The etching apparatus of claim 27, wherein said slots have a non-uniform cross section. 28. The etching apparatus of claim 27, wherein said power supply has at least two RF power supplies. 28. The etching apparatus of claim 27, wherein said first and second power sources comprise two RF power sources tuned to different RF frequencies. 37. The etching apparatus of claim 36, wherein the first power source is tuned to 27 MHz and the second power source is tuned to 2 MHz. As a substrate processing method, this method is A suppression device is set up to position the substrate on the substrate support in the plasma chamber, wherein the suppression device is electrically confined within the interelectrode region on the substrate without resistance to gas flow, the suppression apparatus being an interelectrode region on the substrate. Surround the ground and connect to the ground, Vacuum the plasma chamber through a vacuum pump, Providing a process gas to the interelectrode region via a supply line, wherein the process gas is mechanically induced to travel from the interelectrode region through the suppression device, and Excitation of the process gas into the plasma by applying an electric field to the interelectrode region, Substrate processing method comprising the above step. 40. The method of claim 39, wherein the containment device comprises an annular structure consisting of a conductive wall having a vertical slot through the conductive wall. 40. The method of claim 39, further comprising etching the material from the substrate exposed surface. 40. The method of claim 39, further comprising depositing a material on the substrate exposed surface.