Bowl for processing semiconductor wafers

Details Bowl for processing semiconductor wafers Bowl for processing semiconductor wafers

1999-12-23

2002-07-09

Stinson, Frankie L. (Department: 1746)

Cleaning and liquid contact with solids

Apparatus

With non-impelling fluid deflector or baffle other than...

C134S902000, C134S186000

Reexamination Certificate

active

06415804

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates generally to semiconductor fabrication and, more particularly, to a bowl, a spin, rinse, and dry (SRD) module including the bowl, and a method for loading a semiconductor wafer into an SRD module.
As the semiconductor industry moves to larger, e.g., 300 mm, wafers and to smaller, e.g., 0.18 &mgr;m and smaller, feature sizes, it is becoming increasingly more important to control wafer contamination on both the top side and also the bottom side, i.e., the backside, of wafers during wafer preparation operations. In one conventional wafer preparation operation, a wafer is spin rinsed in a spin, rinse, and dry (SRD) module. During this spin rinsing operation, deionized (DI) water is sprayed onto the top and bottom sides of a wafer as the wafer is spun at high speed. One problem with this spin rinsing operation is that particle recontamination often occurs because of turbulent air above the surface of the wafer.
FIG. 1
is a simplified schematic diagram
10
illustrating the airflow around a wafer in a conventional bowl, which forms part of an SRD module. As shown therein, wafer
12
is disposed in bowl
14
. For sake of simplicity, the spindle, which spins the wafer, and the spindle fingers, which support the wafer above the spindle, have been omitted from FIG.
1
. As wafer
12
spins in bowl
14
, the spinning action of the wafer transfers energy to the air flowing to the surface of the wafer. This transferred energy causes the airflow above the surface of wafer
12
to become turbulent and creates recirculating air, i.e., eddies, as indicated by the arrows in FIG.
1
. The amount of energy transferred to the air flowing to the surface of wafer
12
depends on the diameter and the rotational speed of the wafer. In general, the greater the amount of energy transferred to the air, the higher the eddies extend above the surface of wafer
12
. The presence of eddies above the surface of wafer
12
is undesirable because particles or DI water droplets removed from the wafer can circulate in the eddies and be redeposited on an otherwise clean surface of the wafer, thereby causing recontamination.
In view of the foregoing, there is a need for a device for managing the airflow above the surface of a wafer to minimize the recontamination caused by particles and DI water droplets circulating in eddies above the wafer.
SUMMARY OF THE INVENTION
Broadly speaking, the present invention fills this need by providing a bowl that is configured to control the airflow around a wafer. The present invention also provides a spin, rinse, and dry (SRD) module including the bowl and a method for loading a semiconductor wafer into an SRI) module.
In accordance with one aspect of the present invention, a bowl is provided. The bowl includes a bottom wall having a generally circular shape. A sidewall extends upwardly from the bottom wall to define a cylindrical chamber. The sidewall has a projection that extends into the cylindrical chamber. The projection has a top surface that defines a step in the cylindrical chamber and a sloped surface that extends between the top surface and an inner surface of the sidewall. The top surface of the projection is sloped slightly downwardly. The sloped surface of the projection is oriented relative to the top surface such that extensions of the top surface and the sloped surface define an angle in a range from about 30 degrees to about 45 degrees.
In one embodiment, the top surface of the projection defines an angle in a range from about 2 degrees to about 5 degrees relative to a plane perpendicular to an inner surface of the sidewall. In one preferred embodiment, the top surface of the projection defines an angle of about 3 degrees relative to a plane perpendicular to an inner surface of the sidewall and the sloped surface is oriented relative to the top surface such that extensions of the top surface and the sloped surface define an angle of about 34 degrees.
In one embodiment, an annular flow guide disposed in the bowl below the projection such that an annular exhaust opening is defined between an outer edge of the annular flow guide and an inner surface of the sidewall. In one embodiment, the distance between the outer edge of the annular flow guide and the inner surface of the sidewall is in a range from about 0.125 inch to about 0.25 inch. In one embodiment, the annular flow guide is disposed on a separator tube, which is disposed on the bottom wall. In one embodiment, the separator tube has at least three notches formed at one end thereof. The at least three notches and a bottom surface of the annular flow guide define air inlet ports that permit air to flow into the separator tube. In one embodiment, the portion of the bottom wall encompassed by the separator tube has an air exhaust port formed therein.
In accordance with another aspect of the present invention, an SRD module is provided. The SRD module includes a cylindrical tube having an upper end, a lower end, and a wafer port formed therein. The cylindrical tube also has a stop formed on an inner surface thereof. A bowl, which is configured to nest within the lower end of the cylindrical tube, is mounted on a bracket. A spindle for rotating a semiconductor wafer is mounted on a frame and extends into the bowl. A drive mechanism is coupled to the bracket for moving the bowl between a lower position and an upper position. In the lower position, the bowl is clear of the wafer port so that a wafer can be passed into and out of the cylindrical tube. In the upper position, the bowl seals off the wafer port so that a semiconductor wafer mounted on the spindle can be subjected to a spin rinsing operation.
In one embodiment, the bowl in the SRD module has the features of the bowl of the present invention. In one embodiment, an upper edge of the bowl engages the stop formed on the inner surface of the cylindrical tube when the bowl is in the upper position. In one embodiment, the upper end of the cylindrical tube has a filter disposed thereon. In one embodiment, the filter is either a HEPA filter or an ULPA filter. In one embodiment, the drive mechanism is an air cylinder.
In accordance with yet another aspect of the present invention, a method for loading a semiconductor wafer into an SRD module is provided. In this method a bowl is nested within a lower end of a cylindrical tube having a wafer port formed therein. The bowl is then moved from an upper position to a lower position to expose the wafer port. Once the bowl is in the lower position, a semiconductor wafer is passed into the cylindrical tube through the wafer port.
In one embodiment, the cylindrical tube has a wafer inlet port and a wafer outlet port formed therein. In this embodiment, the operation of moving the bowl from the upper position to the lower position exposes the wafer inlet port and the wafer outlet port. Before the semiconductor wafer is passed into the cylindrical tube through the wafer inlet port, the method further includes the operation of removing a semiconductor wafer from the cylindrical tube through the wafer outlet port.
In one embodiment, the method further includes the operations of moving the bowl from the lower position to the upper position to seal off the wafer port, and performing a spin rinsing operation on the semiconductor wafer with the bowl in the upper position. In one embodiment, the bowl is moved between the upper position and the lower position by an air cylinder. In one embodiment, the upper position is defined by a stop provided on an inner surface of the cylindrical tube.
The bowl of the present invention is configured to control the airflow around a wafer so that recontamination caused by recirculating particles and DI water droplets is minimized. In particular, the airflow directs contaminated air and particles away from the wafer. The configuration of the SRD module of the present invention in which the bowl moves allows for “open architecture” with respect to wafer loading because wafers can be loaded into the module from any direction by simply clocking,

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