Patent Application
20140053982
1. Field of the Invention
The invention relates to a device and a method for processing wafer-shaped articles, such as semiconductor wafers, flat panel displays or optical discs.
2. Description of Related Art
Semiconductor wafers are subjected to various surface treatment processes such as etching, cleaning, polishing and material deposition. To accommodate such processes, a single wafer may be supported in relation to one or more treatment fluid nozzles by a chuck associated with a rotatable carrier, as is described for example in U.S. Pat. Nos. 4,903,717 and 5,513,668.
U.S. Pat. No. 4,903,717 discloses that its spin-chuck may be raised and lowered relative to a surrounding liquid collector that has plural liquid collecting levels and a common exhaust for collecting gas from the interior of the liquid collector.
U.S. Pat. No. 7,837,803 discloses an improved liquid and gas collector in which the exhaust at each of the levels may be individually controlled via valves provided at each of the levels. However, depending upon the particular process being performed upon the wafer-shaped article, the valves of that patent will come in contact with chemically aggressive fumes. It can be difficult to maintain such valves in good working order under such conditions.
There is therefore a need for a collector structure that can better prevent fumes from various media (e.g., acid, base, organic) from intermingling in a common process chamber, so as to prevent vapor cross-contamination. Such cross-contamination could result in the deposition of crystalline solids on delicate processing equipment, as well as various safety issues.
The invention in one aspect thus pertains to an apparatus for processing wafer-shaped articles, comprising a spin chuck for holding and rotating a wafer-shaped article about a rotation axis. The spin chuck is displaceable along the rotation axis between at least two positions. At least one liquid dispenser supplies liquid to a rotating wafer-shaped article when mounted on the spin chuck. A collector surrounds the spin chuck, and has at least two exhaust levels for exhausting gas from an interior of the collector, the at least two exhaust levels corresponding to the at least two positions of the spin chuck. A gas supply system supplies gas to an interior of the collector, and comprises ducts for supplying gas separately to a first interior region above the spin chuck when the spin chuck is positioned in one of its at least two positions and a second interior region below the spin chuck when the spin chuck is positioned in that same one of its at least two positions.
In preferred embodiments of the apparatus according to the present invention, the ducts comprise separately controllable valves so that gas flows to the first and second interior regions can be controlled independently of one another.
In preferred embodiments of the apparatus according to the present invention, the spin chuck is displaceable along said rotation axis between at least three positions, and wherein said collector has at least three exhaust levels corresponding to said at least three positions of said spin chuck.
In preferred embodiments of the apparatus according to the present invention, said spin chuck is displaceable along said rotation axis between at least four positions, and wherein said collector has at least four exhaust levels corresponding to said at least four positions of said spin chuck.
In preferred embodiments of the apparatus according to the present invention, the collector comprises a gas distribution plate positioned above and overlying the spin chuck.
In preferred embodiments of the apparatus according to the present invention, said valves are manually controlled.
In preferred embodiments of the apparatus according to the present invention, said valves are automatically controlled.
In preferred embodiments of the apparatus according to the present invention, pressure sensors are positioned in said first and second regions, said valves being automatically controlled based upon readings of said pressure sensors.
In preferred embodiments of the apparatus according to the present invention, a shutter is positioned in an uppermost exhaust level of said collector.
In preferred embodiments of the apparatus according to the present invention, said shutter is automatically controlled so as to open in response to said spin chuck being displaced to said uppermost exhaust level, and to close when said spin chuck is displaced to a lower exhaust level of said collector.
In preferred embodiments of the apparatus according to the present invention, each of said valves comprises at least three flow settings.
In preferred embodiments of the apparatus according to the present invention, said valves are controlled such that a relatively greater gas flow is provided to said first region and a relatively lesser gas flow is provided to said second region, when said spin chuck is positioned at a lower one of said at least two exhaust levels, and a relatively lesser gas flow is provided to said first region and a relatively greater gas flow is provided to said second region, when said spin chuck is positioned at a lower one of said at least two exhaust levels.
In another aspect, the present invention relates to a method for processing wafer-shaped articles, comprising positioning a wafer-shaped article on a spin chuck that is surrounded by a collector, displacing said spin chuck vertically so as to position the spin chuck and the wafer-shaped article at a first level within said collector, supplying gas interiorly of said collector separately at a first flow rate to a first region above the wafer shaped article and at a second flow rate to a second region below the wafer-shaped article, displacing the spin chuck vertically so as to move the spin chuck to a second level within the collector that is above the first level, and supplying gas interiorly of said collector separately at a third flow rate to a third region above the wafer shaped article and at a fourth flow rate to a fourth region below the wafer-shaped article, wherein the first flow rate is greater than the third flow rate, and wherein the second flow rate is less than the fourth flow rate.
In preferred embodiments of the method according to the present invention, ambient pressure is measured in each of the first and second regions, and the first and second flow rates are controlled such that a pressure differential between said first and second regions is maintained at less than a predetermined value.
In preferred embodiments of the method according to the present invention, the wafer-shaped article is loaded and unloaded at an uppermost level within the collector, while keeping open a shutter provided in the uppermost level of the collector.
In preferred embodiments of the method according to the present invention, an ambient pressure outside of the collector is monitored, and the first and second flow rates are controlled such that a pressure differential between the ambient pressure outside of the collector and each of said first and second regions is maintained at less than a predetermined value.
Other objects, features and advantages of the invention will become more apparent after reading the following detailed description of preferred embodiments of the invention, given with reference to the accompanying drawings, in which:
However, when the chuck 1 is raised to one of its upper level positions as shown in
Turning now to
Wafer W is preferably a semiconductor wafer and chuck is preferably a component of a single-wafer wet processing tool for such semiconductor wafers. As those skilled in the art are aware, such chucks are designed to receive a wafer W of a specified diameter, with examples being 200 mm, 300 mm and 450 mm.
Spin chuck 10 is shown as being rotated by motor 15 via shaft 13, and this drive also serves to displace the spin chuck 10 axially between each of the four collector levels. Such a spin chuck may comprise a series of gripping pins (not shown) for holding a wafer W at its edge, or may support a wafer W on a cushion of flowing gas by implementation of the Bernoulli principle as described in U.S. Pat. No. 4,903,717. Chuck 10 could alternatively take the form of a magnetic rotor that is rotated and displaced axially via a surrounding stator, as described for example in commonly-owned co-pending U.S. application Pub. No. 2012/0018940.
At least one liquid dispenser 49 is provided. In this embodiment, a liquid dispenser is provided at each of the three process levels, although only the lowermost liquid dispenser 49 is illustrated in
The apparatus of this embodiment also includes a gas supply system 50, which is preferably based upon a filter fan unit 51 designed to provide particle-free air (or extremely low particle air) to the interior of collector 40. Other gases than air can be supplied through the filter fan unit 51, for example nitrogen or air that is enriched in nitrogen and correspondingly impoverished of oxygen. Downstream of filter fan unit 51 the gas flow is divided between an upper duct 53 and a lower duct 55. A respective control valve 57, 59 is associated with each of these ducts 53, 55. Elements 57, 59 may for example be butterfly valves. Furthermore, although elements 57, 59 are referred to herein as “valves”, it is to be understood that in this context that term encompasses other structures for controlling the rate of gas flow to the ducts 53, 55, such as adjustable shutters, vents and the like.
Duct 53 preferably terminates in a gas showerhead 52, such as that described for example in U.S. Pat. No. 6,715,943. Duct 55 leads into an annular pressure distribution chamber 58, from which gas is upplied into the wafer ambient via lateral distribution plate 54. Also visible in
Spin chuck 10 is in its lowermost position in
Valves 57, 59 thus preferably each have at least three open positions, corresponding to low, moderate and high rates of flow, or stated differently, nearly closed, partly open and fully open. The state of valves 57, 59 can be changed manually is some embodiments, but in more preferred embodiments the valves 57, 59 are set autoamtically based upon detecting the position of chuck 10 at one of the four exhaust levels, or based upon an ambient pressure measurement, or based upon a combination of these parameters.
Further precision in controlling the pressures P1 and P2 can be achieved by the use of pressure sensors 61, 63, which detect ambient pressure inside the collector 40 in the regions above and below the chuck, respectively. If the detected pressures differ from one another by more than a predetermined threshold, for example about 5 Pa, then the flow rate through one or both of valves 57, 59 is adjusted until the pressure difference falls below that threshold, and the ongoing monitoring of the ambient pressures P1 and P2 and associated control of valves 57, 59 maintains the pressure differential below the chosen threshold.
The apparatus may also be equipped with an external ambient pressure sensor 65, with valves 57, 59 being controlled to maintain the difference between each of pressures P1 and P2 and the external ambient pressure within a predetermined limit, for example about 5 Pa.
In case of using pressure sensors 61, 63 and optionally 65, valves 57, 59 preferably have a much greater number of positions, inclusive of valves whose degree of opening is continuously variable.
Referring now to
In
Finally, in
Although the invention has been described in connection with several preferred embodiments in the foregoing description, it will be appreciated by those skilled in the art that various modifications are possible without departing from the true scope and spirit of the invention as disclosed herein and as set forth in the appended claims.
