Drying and gas or vapor contact with solids – Process – Gas or vapor contact with treated material
Reexamination Certificate
2002-08-28
2003-09-09
Esquivel, Denise L. (Department: 3749)
Drying and gas or vapor contact with solids
Process
Gas or vapor contact with treated material
C034S348000, C034S630000, C034S218000, C034S444000, C034S487000
Reexamination Certificate
active
06615510
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to removing liquid from wafers, and more particularly to apparatus and methods for drying a wafer that has been wet in a liquid bath, after which the wafer and the bath are separated at a controlled rate to form a thin layer of liquid on the wafer as the wafer is positioned in a gas-filled volume, wherein the volume is defined by a hot chamber that continuously transfers thermal energy to the wafer in the volume, and wherein hot gas directed into the volume and across the wafer and out of the volume continuously transfers thermal energy to the wafer, so that the thermal energy transferred to the wafer in the volume evaporates the thin layer from the wafer without decreasing the rate of separation of the wafer and the bath below a maximum rate of such separation at which a meniscus will form between the bath and the surface of the wafer during such separation.
2. Description of the Related Art
In the manufacture of semiconductor devices, process chambers are interfaced to permit transfer of wafers between the interfaced chambers. Such wafer transfer is via transport modules that move the wafers, for example, through slots or ports that are provided in the adjacent walls of the interfaced chambers. For example, transport modules are generally used in conjunction with a variety of wafer processing modules, which may include semiconductor etching systems, material deposition systems, flat panel display etching systems, and wafer cleaning systems. Due to growing demands for cleanliness and high processing precision, there has been a greater need to reduce the amount of human interaction during, between, and after such processing steps. This need has been partially met with the implementation of vacuum transport modules which operate as an intermediate wafer handling apparatus (typically maintained at a reduced pressure, e.g., vacuum conditions). By way of example, a vacuum transport module may be physically located between one or more clean room storage facilities where wafers are stored, and multiple wafer processing modules where the wafers are actually processed, e.g., etched or have deposition performed thereon, or cleaned. In this manner, when a wafer is required for processing, a robot arm located within the transport module may be employed to retrieve a selected wafer from storage and place it into one of the multiple processing modules.
Despite use of such intermediate wafer handling apparatus, it is still necessary to clean and dry the wafers at the completion of such processing. As an example, after the wafers have been cleaned, the wafers may have a non-uniform coating of liquid. A wafer with such non-uniform coating of liquid, or with one or more drops of liquid thereon, or with any liquid thereon in any physical form, may be said to be “wet”. In contrast, a wafer having a uniform coating of liquid may be said to be “uniformly wet”.
In the past, annular-shaped pieceparts other than wafers have been subjected to a drying operation. After cleaning and while wet, such pieceparts have been placed in a tank containing a bath of hot liquid. In one type of drying operation, the hot liquid has been drained from the tank at a rate such that a thin layer of liquid, rather than one or more drops of liquid, forms on that portion of such piecepart that is out of the draining liquid. The thin layer has been preferred over one or more drops because a drop of liquid has a high volume, e.g., from about 0.001 ml. to about 0.020 ml. In comparison to the drop, a thin layer of liquid on a wafer such as a 200 mm. diameter wafer, may only have a volume at the maximum diameter of about 0.133 of 0.0105 ml., which is the middle of the above volume range of the drop, for example. Evaporation of a drop generally results in the concentration of small particles at the last small point at which the drop exists. When the piecepart is a wafer, such concentration may result in defects in a chip made from the wafer.
To remove the thin layer from such piecepart, reliance has been placed on the thermal energy stored in such piecepart to provide the thermal energy necessary to evaporate the thin layer. However, when such pieceparts are “wafers”, as defined above, problems have been experienced in not properly drying the thin layer from the wafer. For example, it appears that using only such stored thermal energy, the thin layer evaporates from the wafer at a rate less than the maximum rate of separation of the liquid bath and the wafer at which a meniscus will form between the liquid bath and the surface of the wafer during such separation. Thus, the rate at which the liquid is drained from the tank has to be decreased to match the rate of evaporation. Alternatively, the wafer would have to be retained in the tank after the draining has been completed. Each of such decreased rate of draining and such retaining increases the time required to dry the wafer, which increases the cost of fabricating devices based on the wafer.
In view of the forgoing, what is needed is apparatus and methods of efficiently drying wafers. Such efficient drying should allow the wafers and the liquid to be separated at a rate no less than the maximum rate of separation of the liquid and the wafer at which a meniscus will form between the liquid bath and the surface of the wafer. Also, the efficient drying should rapidly remove from the wafer a thin layer of liquid that forms on the wafer as the wafer and the bath are separated, wherein “rapidly” means such removal occurs before the wafer and the bath have been completely separated e.g., separated by about 0.004 inches.
SUMMARY OF THE INVENTION
Broadly speaking, the present invention fills these needs by providing apparatus and methods of efficiently removing fluid from wafers. The efficient removing is attained by providing apparatus and methods for drying a wafer that has been uniformly wet in a fluid bath, in which the wafer and the bath are separated at a controlled rate to form a thin layer of fluid on the wafer as the wafer is positioned in a gas-filled volume. In addition to such separation, the efficient removing is attained by defining the gas-filled volume by use of a hot chamber that continuously transfers thermal energy to the wafer in the volume. Further, hot gas directed into the volume and across the wafer and out of the volume continuously transfers thermal energy to the wafer. The directing of the gas out of the volume is independent of the separation of the bath and the wafer. The thermal energy transferred to the wafer in the volume evaporates the thin layer from the wafer without decreasing the rate of separation of the wafer and the bath below the maximum rate of such separation at which a meniscus will form between the bath and the surface of the wafer during such separation. In addition to such separation and directing of the hot gas across the wafer and out of the volume, the relative humidity in the volume is kept low to inhibit recondensation of the fluid on the wafers, for example.
Such efficient removal enables the wafer throughput of such apparatus and method to be limited only by the type of wafer that is being dried, and the type of fluid used to wet the wafer. For example, the characteristics of particular types of wafers and fluid dictate the maximum rate of such separation of the wafer and the bath at which a meniscus will form between the bath and the surface of the wafer during such separation and the wafer will be uniformly wet.
In one embodiment of the present invention a wafer drying system may include a bath enclosure configured to hold a fluid so that the fluid defines a top fluid surface. A temperature and humidity-controlled chamber may also be defined above the fluid surface. The chamber has a first opening at a first side proximate to the fluid surface and a second opening at a second side that is opposite to the first side.
In another embodiment of the present invention the wafers to be dried have opposite sides, and apparatus for drying the waf
Borkowski Jonathan E.
Jones Oliver David
McMahon Kenneth C.
Mehmandoust Yassin
Olivas James M.
Esquivel Denise L.
O'Malley Kathryn S.
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