Patent Application
20150014176
Semiconductor devices are used in a wide range of consumer electronics, computers, communication equipment, and various other products. They are made from silicon, or other semiconductor materials, that are often in disc-shaped wafers. The wafers undergo many manufacturing processes to form the microelectronic circuits. During various manufacturing steps, the wafers are processed using fluid chemicals (e.g., acids, caustics, etchants, photoresists, processing fluids, purified water, etc.) as well as gaseous chemicals. In one or more manufacturing steps, layers of the wafer may need to be accurately etched. However, it is often difficult to distribute the etching fluids evenly over the surface of the wafer, particularly when the diameter of the wafer is large.
The wafers are also rinsed and dried to remove contaminants (i.e., contaminants left by chemical mechanical polishing), which can cause defects in the end product devices or interfere with subsequent process steps. Rinsing typically takes place in a spray chamber. However, it may be difficult to ensure that all areas of the wafer surface have been properly rinsed in such chambers.
As greater emphasis is placed on the scaling down the size of microelectronics circuits, and wafers begin having larger diameters, new processes and apparatus must be developed and the accuracy of existing processes and apparatus must be honed. However, current single wafer processing apparatus increasingly do not meet these demands. The designs of such single wafer processing apparatus make it difficult to improve the accuracy of the processes they perform.
A wafer processing apparatus is disclosed that includes a wafer support and a processing base. The wafer support is configured to support a wafer at a processing position with respect to a processing base. The processing base includes a scroll pump oriented to pump a processing fluid in a substantially perpendicular direction with respect to the surface of the wafer when the wafer contacts the processing fluid while in the processing position. While in contact with the processing fluid, the wafer support may rotate the wafer in the processing fluid. In one embodiment, the diameter of the scroll pump is substantially the same as or greater than the diameter of the surface of the wafer being processed.
The wafer head 20 may also be driven along axis 45 by a still further motor 50. In this example, motor 50 is configured to drive the wafer head 20 and wafer support 35 between the elevated position shown in
The processing base 25 includes a shell assembly 55 that surrounds a processing space 60. Fluid passages are disposed through the processing base 25 and provide means for conducting processing fluids therethrough. In one example, the fluid passages may be configured to selectively recirculate and/or remove processing fluid from the processing space 60.
The processing space 60 is surrounded by the outer shell assembly 55 and contains a scroll pump 75. The scroll pump 75 is oriented to pump the processing fluid (i.e., liquids, gases, etc.) In a direction substantially perpendicular to the surface of the wafer 15. To promote even processing across the entire diameter of the wafer, the scroll pump 75 may have a diameter approximately equal to or greater than the diameter of the surface of the wafer to be processed.
The processing base 25 also includes a scroll pump drive 80. The scroll pump drive 80 includes a motor 85 including a rotor 90 having a cam 95. The cam 95 is configured to engage a cam follower disposed at a bottom, central portion of a moving scroll of the scroll pump 75 to oscillate the moving scroll with respect to a fixed scroll.
A control system 100 may govern the operation of the apparatus 10. In one example, the control system 100 includes a drive/valve controller 105 and a chemistry controller 115. The drive/valve controller 105 may direct operation of the various motors of the apparatus 10. For example, the drive/valve controller may: 1) elevate the wafer head 20 along axis 45 and rotate it to a wafer face-up orientation about axis 27 to receive the wafer 15 on the wafer support 35; 2) rotate the wafer head 20 about axis 27 to a wafer face-down orientation and drive it along axis 45 to place the wafer in a processing position in the processing base 25; and 3) drive the scroll pump 75. The drive/valve controller 105 may also direct the valves of the apparatus 10 to various states during processing to govern fluid flow into, through, and from the processing base 25.
The chemistry controller 115 governs the supply of various processing chemistries to the processing base 25 in cooperation with the drive/valve controller 105. For example, the chemistry controller 115 may operate to: 1) regulate the content of the processing fluid; 2) switch between processing chemistries at the same apparatus 10; 3) add constituents to processing chemistry; 4) regenerate used processing fluid for further use; and/or 5) regulate recirculation, waste treatment, and/or disposal of the processing fluid.
The interior of the inner shell 130 defines the processing space 60, which holds the scroll pump 75 and the processing fluid. The scroll pump 75 includes a first scroll 140, which is fixed, and a second scroll 145 which oscillates with respect to the first scroll 140. The material used for the scrolls depends on the processes that are to be executed by the apparatus 10. The materials of each scroll may be the same or different. One or both scrolls may be formed from materials having high thermal conductivity so they may be configured as heaters to provide localized heating of the processing fluid.
The scroll pump drive 80 includes a motor 85 that drives a rotor 90. The rotor 90 extends into a common chamber 170 and terminates at a cam 175 that engages a cam follower 180. In turn, the cam follower 180 is in fixed engagement with respect to a lower, central portion of the oscillating scroll 145. Referring to
The common chamber 170 includes an inlet 179 and an outlet 187. The processing fluid at the inlet 179 may be received through a recirculation path from the processing space 60, or from an inlet 183 connected to receive fresh processing fluid. The recirculation path includes the inlet 179 of the common chamber 170, and a horizontal conduit 195 extending from the outlet 187 to vertical conduit 200. Another horizontal conduit 205 extends between the vertical conduit 200 and an inlet 207 of the processing space 60.
During processing, before reaching a predetermined number of wafers to be processed with the recirculated processing fluid, the processing fluid may be passed through the recirculation path. Once the processing fluid has been used to process the predetermined number of wafers, however, the scroll pump 75 may be directed by the control system 100 to empty the processing space 60 instead of recirculating the processing fluid, after which a fresh supply of processing fluid is provided through inlet 183 and pumped into the processing space 60 by the scroll pump 75.
Depending on the process executed by the apparatus 10, the wafer support 35 may drive the wafer 15 to an elevated position in which the wafer 15 is substantially level with a catch 210 formed in the upper annulus 137. The wafer 15 may be elevated to this position while the processing space is still full. Once in this position, the wafer 15 may be subject to a spinoff operation in which residual processing fluid is directed to the catch 210 by centrifugal force and exits through exhaust channel 230. A drying gas may also be directed at the surface of the wafer 15 through one or more nozzles 220 disposed in the upper annulus 137. For example, the drying gas may be a vapor of an organic solvent, preferably isopropyl alcohol, which is introduced into the environment around the wafer through nozzles 220. The vapor may be non-condensing, and is mixed with nitrogen or other non-reacting gas. After the spinoff operation, the wafer 15 may be elevated to the positions shown in
In other processes, the processing space 60 may be emptied by the scroll pump 75, after which the wafer 15 is elevated to the catch 210 for a spinoff and/or drying process. At that time, a fresh supply of processing fluid may be provided through inlet 183 and pumped into the processing space 60 by the scroll pump 75. The wafer head 37 may then lower the wafer 15 to a position in which it is subject to further processing in the processing space 60.
Using a scroll pump 75 to pump the processing fluid may improve control of the process, and provide a processing fluid boundary at the surface of the wafer that is conformal across the diameter of the wafer 15. More particularly, since the flow of processing fluid from the scroll pump 75 is pumped in a direction substantially perpendicular to the surface of the wafer 15, the processing fluid is agitated at the processing fluid boundary. In cleaning and rinsing operations, this agitation assist in removing fluids and particles left over during prior processing operations.
The processes executed by the apparatus 10 are typically governed by prior processes executed on the wafer 15. When cleaning a copper surface of the wafer, the processing fluid in processing space 60 may be an alkaline solution that includes nitrogen to remove oxygen from the fluid, thereby reducing the oxidation potential of the solution and reducing the etch rate of the copper by the processing fluid.
Cleaning silicon wafers in particular present particular challenges. Silicon wafers often have a very thin oxide surface layer, such as a native or passivation oxide or a chemically grown oxide. Surface metal particles, which are contaminants which must be removed. These particles may be on top of the oxide, in the oxide or at the oxide/silicon interface. The oxide surface layer is typically less than 20 Angstroms (A) thick. Accordingly, a highly controlled etch must be used to remove contaminants from this layer. If the oxide is entirely removed, the surface becomes hydrophobic, and may become difficult to clean. Therefore, ideally, as much oxide as possible is etched away to remove contamination on the surface of the oxide layer, but without removing all of the oxide layer, to avoid having surface become hydrophobic.
Dilute hydrofluoric acid (HF) may be introduced into the processing space 60 to remove particles on top of the oxide, in the oxide, or at the oxide/silicon interface. Scroll pump 75 provides an even distribution of the HF across the diameter of the wafer and, further, facilitates control of the point at which the etching of the oxide ceases.
While the foregoing is directed to various embodiments of analog show plating apparatus, other and further embodiments may be devised without departing from the basic teachings herein, and the scope of the invention is determined, without limitation, by the following claims.
