Drying and gas or vapor contact with solids – Apparatus – With automatic control
Reexamination Certificate
2000-05-26
2002-08-13
Lazarus, Ira S. (Department: 3749)
Drying and gas or vapor contact with solids
Apparatus
With automatic control
C034S196000, C034S197000, C034S228000, C034S527000, C134S061000, C134S104400, C134S137000
Reexamination Certificate
active
06430841
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to removing liquid from substrates, and more particularly to apparatus and methods for drying batches of substrates that have been wet in a liquid bath, after which the batches of substrates and the bath are separated at a controlled rate to form a thin layer of liquid on each substrate of the batches as the batches of substrates are positioned in a gas-filled volume, wherein the volume is defined by an elongated hot chamber that continuously transfers thermal energy to the batches of substrates in the volume, and wherein curtains of hot gas directed into the volume and across the batches of substrates and out of the volume continuously transfer thermal energy to the batches of substrates, so that the thermal energy transferred to the batches of substrates in the volume evaporates the thin layer from each of the substrates without decreasing the rate of separation of the batches of substrates and the bath below a maximum rate of such separation at which a meniscus will form between the bath and the surface of each substrate during such separation.
2. Description of the Related Art
In the manufacture of semiconductor devices, process chambers are interfaced to permit transfer of substrates (such as semiconductor wafers of any of various sizes) between the interfaced chambers. Such transfer is via transport modules that move the substrates, 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 substrate processing modules, which may include semiconductor etching systems, material deposition systems, flat panel display etching systems, and substrate 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 substrate 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 substrates are stored, and multiple substrate processing modules where the substrate are actually processed, e.g., etched or have deposition performed thereon, or cleaned. In this manner, when a substrate is required for processing, a robot arm located within the transport module may be employed to retrieve a selected substrate from storage and place it into one of the multiple processing modules.
Despite use of such intermediate substrate handling apparatus, it is still necessary to clean and dry the substrate at the completion of such processing. As an example, after the substrate have been cleaned, the substrate may have a non-uniform coating of liquid. A substrate 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 substrate having a uniform coating of liquid may be said to be “uniformly wet”.
In the past, substrates such as annular-shaped disks of many various sizes have been used for manufacturing data storage devices, for example. Such substrates have also been subjected to a drying operation. After cleaning and while wet, such substrates 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 substrate 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 substrate such as a 95 mm diameter disk, may only have a volume of at the maximum diameter of the disk of about 0.0007 ml, for example. Evaporation of a drop generally results in the concentration of small particles at the last small point on the disk at which the drop exists. When the substrate is a wafer, such concentration may result in defects in a chip made from the wafer.
To remove the thin layer from such substrate, reliance has been placed on the thermal energy stored in such substrate to provide the thermal energy necessary to evaporate the thin layer. However, when such substrate is a “wafer”, 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.
Additionally, when the substrate is a disk that is used to manufacture generally low-cost data storage devices, for example, it is necessary to process large numbers of such substrates at the same time. However, difficulties have been experienced in assuring uniform drying of each of such substrates. As an example, if the flow rate of the hot gas into the volume is increased in an attempt to process a large number of substrates, the higher flow rate gas may disturb the surface of the liquid bath, resulting in splashing of the liquid onto the surfaces of the substrates. Such splashing may form drops on one or more of the surfaces. Also, even when more than one substrate is processed at the same time, use of a uniform rate of movement of the substrates into, within, and out of the liquid result in inefficiencies, such as relatively long periods of time of a drying cycle. In addition, when more than one substrate is processed at the same time relative humidity problems within the gas volume affect processing of more than one substrate at a time.
In view of the forgoing, what is needed is apparatus and methods of efficiently drying substrates. Such efficient drying should allow batches of the substrates to be efficiently processed. Such efficient drying should also allow the rate of movement of the batches of the substrates to be controlled according to the nature of the movement, e.g., entry of the substrates into the liquid, or movement of the substrates from a deep immersion position to a shallow immersion position in the liquid, or suspense of movement of the substrates, for example. Such control should also allow the liquid and the substrates to be separated at a rate no less than the maximum rate of separation of the liquid and the substrates at which a meniscus will form between the liquid bath and the surface of the substrate. In addition, the efficient drying should assure that the upper surface of the liquid is smooth during such separation. Further, the efficient drying should minimize the effect of relative humidity on the drying of batches of the substrates. Also, the efficient drying should very rapidly remove from the substrate a thin layer of liquid that forms on the substrate as the substrate and the bath are separated, wherein “rapidly” means such removal occurs before the substrate and the bath have been completely separated e.g., separated by 0.004 inches, for example.
SUMMARY OF THE INVENTION
Broadly speaking, the present invention fills these needs by providing apparatus and methods of efficiently removing fluid from batches of substrates. The efficient removing is attained by providing apparatus and methods for drying
Borkowski Jonathan
Jones Oliver David
McMahon Kenneth C.
Mehmandoust Yassin
Olivas James M.
Lam Research Corporation
Lazarus Ira S.
Martine & Penilla LLP
O'Malley Kathryn S.
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