TWI397100B - Plasma reactor and method for using the same - Google Patents

Description

Plasma reactor and method of use thereof

The present invention relates to semiconductor fabrication. More specifically, the present invention relates to a plasma etching apparatus.

A typical plasma etching apparatus includes a reactor in which a chamber is present through which a reactive gas flows. Within the chamber, the gas is typically ionized into a plasma by radio frequency energy. The highly reactive ions of the plasma can be used to form a semiconductor circuit into a bulk circuit (IC) and a material (such as a dielectric between the interconnects or a polymer on one surface of the semiconductor wafer) Mask) reaction. Prior to etching, the wafer is placed in a chamber and held in place by a chuck or holder that exposes the top surface of one of the wafers to the plasma.

In semiconductor processing, the etch rate or deposition rate uniformity on the wafer in each process directly affects product yield. This has become one of the main quality requirements for a process reactor and is therefore considered a very important parameter during the design and development of the reactor. As each of the diameters of the wafers increases, the problem of ensuring the consistency of each batch of integrated circuits becomes more difficult. For example, as the wafer size and the smaller circuit size per wafer increase from 200 mm to 300 mm, the edge exclusion area shrinks to, for example, 2 mm. Therefore, it has become very important to have consistent etch rates, profiles and critical dimensions up to 2 mm from the edge of the wafer.

In a plasma etch reactor, the consistency of the etch parameters (etch rate, profile, CD, etc.) is affected by several parameters. Consistent plasma discharge and therefore plasma chemistry over the wafer has become critical to improving consistency. Many attempts have been made to improve wafer uniformity by injecting a jet of gas through a nozzle, modifying the design of the nozzle, and placing edge rings around the wafer.

One problem in capacitively coupled etch reactors is the lack of consistent RF coupling, especially around the edges of the wafer. 1 illustrates a conventional capacitively coupled plasma processing chamber 100 that represents an exemplary plasma processing chamber of the type typically used to etch a substrate. The plasma reactor 100 includes a chamber 102, a bottom electrode 104, and a top electrode 106. The bottom electrode 104 includes a center bottom electrode 108 and an edge bottom electrode 110. The top electrode 106 includes a center top electrode 112 and an edge top electrode 114. The edge top electrode 114 and the edge bottom electrode 110 each have an annular shape surrounding the center top electrode 112 and the center bottom electrode 108 to form a single plane.

The center bottom electrode 108 is connected to the RF power supply 118, while the top electrode 106 and the edge bottom electrode 110 are grounded to discharge charge generated in the plasma 116 between the top electrode 106 and the bottom electrode 104. As illustrated in FIG. 1, the shape of the glow discharge region (plasma 116) is distorted near the edge of the center bottom electrode 108 due to the grounded edge bottom electrode 110. This distortion causes an inconsistent etch rate on a substrate (not shown) placed on the central bottom electrode 108.

During plasma processing, positive ions accelerate through the equipotential field lines to strike the surface of the substrate, thereby providing the desired etching effect, such as improved etch directivity. Due to the geometry of the upper electrode 106 and the bottom electrode 104, the field lines across the wafer surface may be inconsistent and may vary significantly at the edges of the wafer 104. Therefore, the ground ring 110 is typically provided to improve processing uniformity across the wafer surface.

Because the portion of the top electrode 106 is static, the etch rate at the center and edges of the wafer cannot be individually controlled. Inconsistencies during the etching process can result in different sizes between the center and the edges, thereby reducing the yield of reliable products per wafer.

Therefore, there is a need for a method and apparatus for independently controlling the etch rate at the center and edges of a wafer. One primary object of the present invention is to address such requirements and to provide further related advantages.

A plasma reactor comprising a chamber, a bottom electrode, a top electrode, a ground extension adjacent the bottom electrode and substantially surrounding the bottom electrode. A top ground extension extends adjacent to the top electrode and is substantially parallel to the top electrode. The top electrode is also grounded. The top ground extension can be independently raised or lowered to extend into an area above the bottom ground extension.

Embodiments of the invention describe a plasma reactor herein. It will be appreciated by those skilled in the art that the following detailed description of the invention is intended to be illustrative and not restrictive. Other embodiments of the present invention will be readily apparent to those skilled in the art having the benefit of this disclosure. Reference will now be made in detail to the embodiments of the invention illustrated The same reference indicators will be used in the drawings and the detailed description below to refer to the same.

For the sake of clarity, not all of the conventional features of the embodiments described herein are shown and described. However, it should be understood that in the development of any such actual embodiment, in order to achieve a developer's specific objectives (such as compliance with application and commercialization constraints), many embodiment specific decisions must be made, and such specific objectives It will vary from one embodiment to another and from one developer to another. Moreover, it should be appreciated that this development work can be complex and time consuming, but it is still a routine engineering task for those of ordinary skill in the art having the benefit of this disclosure.

2 illustrates an embodiment of a plasma reactor 200 that includes a chamber 202, a bottom electrode 208, a bottom electrode extension 210, a top electrode 212, and a top electrode extension 214. According to an embodiment, the bottom electrode extension 210 includes a ground ring 210 that is parallel and adjacent to the bottom electrode 208 and that surrounds the bottom electrode 208. The top electrode extension 214 includes an adjustable ground ring 214 that is parallel and adjacent to the top electrode 212 and that surrounds the top electrode 212.

The bottom electrode 208 is coupled to the RF power supply 218, while the top electrode 212, the top electrode extension 214, and the bottom electrode extension 210 are grounded for discharging charge from the plasma 216 generated between the top electrode 212 and the bottom electrode 208. For example, bottom electrode extension 210 and top electrode extension 212 can be made of a conductive material such as aluminum. As illustrated in FIG. 2, the plasma 216 includes two regions 220 and 222 that have different plasma densities based on the location (height) of the top electrode region 214.

The bottom electrode 208 is configured to receive a workpiece and includes an associated bottom electrode region that is adapted to accommodate the workpiece. The bottom electrode 208 is coupled to at least one power supply 218. Power supply 218 is configured to generate RF power that is delivered to bottom electrode 208. For illustrative purposes only, a dual frequency power supply 218 can be used to generate a high potential that is applied to a gas to produce plasma 216. More specifically, the illustrated power supply 218 is a dual supply frequency power supply operating at 2 MHz and 27 MHz, which is included in an etching system manufactured by Lam Research. Those skilled in the art will appreciate that other power supplies capable of producing plasma in the processing chamber 202 can also be used. Those skilled in the art will appreciate that the present invention is not limited to RF frequencies of 2 MHz and 27 MHz, but can be applied to a wide range of frequencies. The invention is also not limited to dual frequency power supplies, but can also be applied to systems having three or more RF power sources over a wide range of frequencies.

The top electrode 212 is disposed a predetermined distance above the bottom electrode 208. Top electrode 212, top electrode extension 214, and ground extension 210 are configured to provide a complete circuit for RF power delivered from bottom electrode 208. The top electrode extension 214 can move up and down independently of the top electrode 212 to control the plasma density at the edge of the bottom electrode 208 (plasma zone 222). As the plasma density at the edge of the bottom electrode 208 changes, the etch rate (whether faster or slower) on that region can be controlled independently of the etch rate in the plasma region 220. Those of ordinary skill in the art will appreciate that there are many ways to reduce and raise the top electrode extension 214. For example, a mechanical or electric knob can be used to raise or lower the top electrode extension 214 without opening and entering the interior of the chamber 202.

During plasma processing, positive ions accelerate through the equipotential field lines to strike the surface of the substrate, thereby providing the desired etching effect, such as improved etch directivity. Due to the geometry of the top electrode 212 and the bottom electrode 208, the field lines across the wafer surface may be inconsistent and may vary significantly at the edge of the wafer. Thus, a top electrode extension 214 and a bottom electrode extension 210 are provided to improve processing uniformity across the wafer surface.

The plasma reactor 200 is configured to house a gas (not shown) that is converted to a slurry 216 by the plasma reactor 200. By way of example and without limitation, a relatively high gas flow rate into the chamber is 1500 sccm. Gas flow rates of less than 1500 sccm and greater than 1500 sccm can also be applied.

To generate plasma 216 within chamber 202, power supply 218 is used and RF power is transferred between bottom electrode 208 and top ground electrode 212. The gas is then converted into a plasma 216 for processing the workpiece or a semiconductor substrate. For example and without limitation, an RF power level of 2 W per cubic centimeter of plasma volume can be applied. An RF power level of less than 2 W per cubic centimeter of plasma volume can also be applied.

For illustrative purposes, the plasma reactor 200 depicted in FIG. 2 uses capacitive coupling to create a plasma 216 in the processing chamber 202. Those skilled in the art will appreciate that the apparatus and method of the present invention can be adapted for use with inductively coupled plasma.

It will be understood by those skilled in the art that the above configuration shown in FIG. 2 is not intended to be limiting, and other configurations may be used without departing from the inventive concepts disclosed herein. For example, two or more adjacent top electrode extensions 214 can be positioned to further control the etch rate on the edge of the bottom electrode 208.

Figure 3 illustrates a method of using the plasma reactor illustrated in Figure 2. At 302, the position (raised or lowered) of the top electrode extension 214 is selected. The top electrode extension 214 can be raised and lowered to extend into a region above the bottom electrode extension. At 304, the plasma reactor 200 processes a wafer supported by the bottom electrode 208. At 306, the wafer is inspected to determine etch uniformity across the wafer surface. At 308, the position of the top electrode extension 214 is adjusted based on the analysis in 306 to further improve the etch rate uniformity across the wafer surface.

Although the embodiments and applications of the present invention have been shown and described, it will be apparent to those skilled in the art <RTIgt; </ RTI> <RTIgt; </ RTI> <RTIgt; Many modifications have been made to the changes. Therefore, the invention is not limited unless it is in the spirit of the appended claims.

100. . . Capacitively coupled plasma processing chamber/plasma reactor

102. . . Chamber

104. . . Bottom electrode

106. . . Top electrode

108. . . Center bottom electrode

110. . . Bottom bottom electrode

112. . . Center top electrode

114. . . Edge top electrode

116. . . Plasma

118. . . RF power supply

200. . . Plasma reactor

202. . . Chamber

208. . . Bottom electrode

210. . . Bottom electrode extension

212. . . Top electrode

214. . . Top electrode extension

216. . . Plasma

218. . . RF power supply

220. . . Plasma zone

222. . . Plasma zone

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a view schematically showing a plasma reactor according to a prior art.

2 is a diagram schematically illustrating a plasma reactor in accordance with an embodiment.

Figure 3 is a flow chart that schematically illustrates a method of operating the plasma reactor illustrated in Figure 2.

200. . . Plasma reactor

202. . . Chamber

208. . . Bottom electrode

210. . . Bottom electrode extension

212. . . Top electrode

214. . . Top electrode extension

216. . . Plasma

218. . . RF power supply

220. . . Plasma zone

222. . . Plasma zone

Claims (14)

A plasma reactor comprising: a body defining a chamber; a bottom electrode disposed within the chamber and configured to receive a workpiece, the bottom electrode being in a first plane; a top An electrode disposed in the chamber, the top electrode being located in a second plane of a predetermined distance from the bottom electrode, the second plane being substantially parallel to the first plane; a bottom extending to the bottom, adjacent to the bottom An electrode is substantially concentric with the bottom electrical portion, the bottom ground extension extending substantially in the first plane; a top ground extending adjacent to the top electrode and substantially concentric with the top electrode, the top grounded The extension is configured to independently move up or down from the top electrode and move away from or toward the bottom electrode to control a surrounding electric field strength and thereby change a surrounding plasma density in the chamber The top ground extension is further disposed to be substantially disposed in a third plane that is substantially parallel to the first plane and the second plane; a radio frequency source, Bonding the bottom electrode and the top electrode is grounded. The plasma reactor of claim 1 wherein the top ground extension comprises a ring. The plasma reactor of claim 1 wherein the bottom ground extension comprises a ring. A plasma reactor as claimed in claim 1, wherein the radio frequency source is configured to produce a widely variable frequency. A method of using a plasma reactor having a body defining a chamber having a bottom plate and a top plate spaced apart by a predetermined distance, the bottom plate being located in a first plane Wherein the top plate is located in a second plane, and the first plane is substantially parallel to the second plane, the plasma reactor also has a first electrode ring and a second electrode ring, the electrode rings are mutually Separated and grounded, and placed in the chamber and configured to be substantially parallel to the first plane and the second plane, the method includes: positioning the bottom panel and the top panel to substantially align with each other, wherein the chamber a portion is disposed between the electrode plates and defines a processing region; the first electrode ring surrounds the bottom plate to place the first electrode ring in the first plane and spaced apart from the bottom plate; RF power is supplied to the bottom plate, and the top plate is grounded; a surrounding electric field strength is controlled, and thus the second electrode ring is placed in position to surround the processing region and is spaced apart from the first plane and the second plane open A change in plasma density around the chamber. The method of claim 5, wherein the providing the RF power source further comprises providing a RF power source having a wide variety of frequencies. The method of claim 5, further comprising forming a plasma in the chamber such that a density system of a portion of the plasma present in the chamber of the first electrode ring and the second electrode ring A density of the plasma that is different from the chamber present in the processing region. A plasma reactor comprising: a body defining a chamber; a pair of electrode plates disposed in the chamber and spaced apart, wherein the first electrode plate of the pair of spaced electrode plates is located at a first In the plane, the second electrode plate of one of the pair of spaced electrode plates is located in a second plane and is spaced apart from the first electrode plate by a predetermined distance from the pair of spaced electrode plates, and the second plane is substantially separated Parallel to the first plane. a first ground electrode ring located in the first plane to surround the first electrode plate and spaced apart from the first electrode plate; a second ground electrode ring substantially parallel to the first ground electrode ring Separating from the first ground electrode ring, and the second ground electrode ring is configured to independently move upward or downward from the second electrode plate and to move away from or move toward the first electrode a plate to control a surrounding electric field strength and thereby change a surrounding plasma density in the chamber; and a source of radio frequency coupled to one of the first electrode plates of the pair of spaced electrode plates, and the pair The second electrode plate of the phase separation electrode plate is grounded. A plasma reactor as claimed in claim 8, wherein the RF source is configured to produce a widely variable frequency. The plasma reactor of claim 8, wherein the second ground electrode ring is movably disposed in the chamber to facilitate the first volume of the second ground electrode ring being placed in the first of the pair of spaced electrode plates And separating the electrode plate and the second electrode plate of the pair of spaced electrode plates from the first electrode plate of the pair of spaced electrode plates and the second electrode plate of the pair of spaced electrode plates. The plasma reactor of claim 8, wherein the surface of one of the first electrode plates of the pair of spaced apart electrode plates extending into the first plane and the pair of spaced apart electrode plates extending into the second plane One of the surfaces of the two electrode plates is coextensive. The plasma reactor of claim 8, wherein a surface of one of the first ground electrode rings extending into the first plane is coextensive with a surface of the second ground electrode ring. The plasma reactor of claim 8, wherein the surface of one of the first electrode plates of the pair of spaced apart electrode plates extending into the first plane and the pair of spaced apart electrode plates extending into the second plane One surface of the two electrode plates is coextensive, and one surface of the first ground electrode ring extending into the first plane is coextensive with a surface of the second ground electrode ring facing the first ground electrode ring of. The plasma reactor of claim 13, wherein the second ground electrode ring is movably disposed in the chamber to facilitate the first volume of the second ground electrode ring being placed in the first of the pair of spaced electrode plates And separating the electrode plate and the second electrode plate of the pair of spaced electrode plates from the first electrode plate of the pair of spaced electrode plates and the second electrode plate of the pair of spaced electrode plates.