Vertical wafer cleaning and drying system

• US 6,082,377 A
• Filed: 05/21/1999
• Issued: 07/04/2000
• Est. Priority Date: 11/18/1997
• Status: Expired due to Fees

• Current Assignee: Bernhard M. Frey
• Original Assignee: Bernhard M. Frey
• Inventors: Frey, Bernhard M.
• Primary Examiner(s): Markoff, Alexander
• Application Number:
  US09/316,676
• Time in Patent Office: 410 Days
• Field of Search: 134/6, 134/9, 134/2, 134/3, 134/1.3, 134/18, 134/32, 134/33, 134/34, 134/902, 15/102, 15/97.1, 15/51, 15/99, 15/103.5
• US Class Current: 134/6
• CPC Class Codes: B08B 1/30 by movement of cleaning members over a surface
• CPC Class Codes: B08B 1/32 using rotary cleaning members
• CPC Class Codes: B08B 11/02 Devices for holding articles during cleaning B08B9/42 takes precedence
• CPC Class Codes: B08B 3/02 Cleaning by the force of jets or sprays
• CPC Class Codes: H01L 21/67028 for cleaning followed by drying, rinsing, stripping, blasting or the like
• CPC Class Codes: Y10S 134/902 Semiconductor wafer

Abstract

A wafer cleaning and drying apparatus comprises a vertical wafer drive assembly providing two-sided wafer cleaning by symmetrically disposed brushes. Each wafer brush comprises two parallel rotatable shafts within the lumen of a substantially tubular sponge, with an adjustable distance between the two shafts, which is narrowed to facilitate insertion into the sponge and widened to stretch the sponge into a substantially oval cross-sectional shape, thereby improving traction. One or more nonrotating perforated fluid delivery tubes are mounted within the lumen of the sponge in the space between the two shafts. The apparatus further comprises a minimal volume rinse/dry enclosure that conserves water and process chemicals; and a wafer transport assembly configured to transfer multiple wafers simultaneously between multiple process stations.

Claims

1. A method for cleaning and drying a semiconductor wafer having a first planar surface and a second planar surface opposite said first planar surface and having a midplane parallel to and equidistant between said first and second planar surfaces, comprising the steps of:

placing a wafer in a wafer drive assembly;

rotating said wafer about a rotation axis in said wafer drive assembly with said planar surfaces of said wafer oriented in a vertical plane and with said rotation axis aligned perpendicular to said planar surfaces;

cleaning said wafer with first and second wafer cleaning brushes disposed symmetrically with respect to said midplane of said wafer, said first and second wafer cleaning brushes comprising, respectively, first and second substantially tubular sponges rotatable beltwise about respective brush axes parallel to said planar surfaces, said first wafer cleaning brush comprising a first brush shaft and a second brush shaft, said first and second brush shafts being rotatable about mutually parallel axes and spaced laterally from each other, said first and second brush shafts being mounted within a lumen of said first substantially tubular sponge;

rotating said first sponge in a first direction while said first sponge is in contact with said first planar surface of said wafer, and rotating said second sponge in a second direction opposite said first direction while said second sponge is in contact with said second planar surface of said wafer, said cleaning step being performed concurrently with said rotating step; and

removing said wafer from said wafer drive assembly.

2. The method according to claim 1, wherein said first and second brush shafts are spaced laterally from each other by an adjustable distance.

3. The method according to claim 2, wherein said first wafer cleaning brush further comprises at least one fluid delivery tube mounted within said lumen of said first sponge, said fluid delivery tube being nonrotating and aligned parallel with said first and second brush shafts and containing perforations for dispensing fluid uniformly along substantially the lengths of said brush shafts.

4. The method according to claim 3, wherein the step of cleaning further comprises dispensing fluid from said fluid delivery tube concurrent with the rotation of said first sponge of said first wafer cleaning brush, such that said fluid irrigates a portion of an inner surface of said first sponge directly after said portion passes around said first brush shaft.

5. The method according to claim 3, wherein the step of cleaning further comprises dispensing fluid from said fluid delivery tube concurrent with the rotation of said first sponge of said first wafer cleaning brush, such that said fluid irrigates a portion of an inner surface of said first sponge directly after said portion passes around said second brush shaft.

6. The method according to claim 2, wherein the steps of placing and removing a wafer further comprise swiveling said first wafer cleaning brush about an axis concentric with said first brush shaft clear of said wafer drive assembly before placing said wafer.

7. The method according to claim 1, wherein the steps of placing a wafer and removing a wafer further comprise transferring said wafer in a wafer transport assembly configured to transfer at least two wafers simultaneously, comprising the steps of:

rotating a substantially cylindrical member having a longitudinal axis and being mounted in a housing from a home position by substantially ninety degrees in a first rotational direction about said longitudinal axis, said housing being translatable parallel to said longitudinal axis, said substantially cylindrical member being attached to at least two substantially parallel members disposed radially relative to said substantially cylindrical member, said at least two substantially parallel members each interconnected radially to said substantially cylindrical member through a mounting/alignment block, said mounting/alignment block enabling alignment between each of said at least two substantially parallel members and said substantially cylindrical member, an end effector being swivelably connected to each of said at least two substantially parallel members;

swiveling said end effector in a first swivel direction relative to each of said at least two substantially parallel members, thereby receiving said wafer;

swiveling said end effector in a second swivel direction opposite said first swivel direction, thereby capturing and holding an edge of said wafer in a precise position and orientation relative to said at least two substantially parallel members;

rotating said substantially cylindrical member by substantially ninety degrees in a second rotational direction opposite said first rotational direction, thereby removing said wafer;

translating said housing by a predetermined distance in a first longitudinal direction;

rotating said substantially cylindrical member by substantially ninety degrees in said first rotational direction;

swiveling said end effector in said first swivel direction, thereby releasing said wafer;

rotating said substantially cylindrical member by substantially ninety degrees in said second rotational direction; and

translating said housing by said predetermined distance in a second longitudinal direction opposite said first longitudinal direction, thereby returning said housing to said home position, said translation in said second longitudinal direction occurring concurrently with said steps of rotating and cleaning said wafer.

8. The method according to claim 7, further comprising directing a fluid spray from a fluid dispensing nozzle onto said wafer substantially, continuously during said transfer of said wafer by said wafer transport assembly, said fluid dispensing nozzle being attached to at least one of said at least two substantially parallel members in a substantially constant position and orientation relative to said wafer.

9. The method according to claim 7, wherein said mounting/alignment block enables alignment between each of said at least two substantially parallel members and said substantially cylindrical member in three translational and three rotational degrees of freedom.

10. The method according to claim 1, further comprising the steps of:

placing said wafer into an open rinse/dry enclosure having an inner surface;

directing a fluid spray from at least one fluid dispensing nozzle adjacent said enclosure onto said wafer and said inner surface of said enclosure;

closing and sealing said rinse/dry enclosure to enclose said wafer, such that said wafer is stationary and all points on said planar surfaces of said wafer are located at a distance no greater than six millimeters from said inner surface;

immersing said wafer in a fluid within said rinse/dry enclosure;

draining said fluid through an outlet valve;

drying said wafer by exposing the surfaces of said wafer to a chemical vapor within said rinse/dry enclosure;

opening said rinse/dry enclosure, thereby providing access to a dry wafer; and

removing said dry wafer from said rinse dry enclosure.

11. The method according to claim 10, wherein the steps of placing a wafer and removing a wafer further comprise transferring said wafer in a wafer transport assembly configured to transfer at least two wafers simultaneously, comprising the steps of:

rotating a substantially cylindrical member having a longitudinal axis and being mounted in a housing from a home position by substantially ninety degrees in a first rotational direction about said longitudinal axis, said housing being translatable parallel to said longitudinal axis, said substantially cylindrical member being attached to at least two substantially parallel members disposed radially relative to said substantially cylindrical member, said at least two substantially parallel members each interconnected radially to said substantially cylindrical member through a mounting/alignment block, said mounting/alignment block enabling alignment between each of said at least two substantially parallel members and said substantially cylindrical member, an end effector being swivelably connected to each of said at least two substantially parallel members;

swiveling said end effector in a first swivel direction relative to each of said at least two substantially parallel members, thereby receiving said wafer;

swiveling said end effector in a second swivel direction opposite said first swivel direction, thereby capturing and holding an edge of said wafer in a precise position and orientation relative to said at least two substantially parallel members;

rotating said substantially cylindrical member by substantially ninety degrees in a second rotational direction opposite said first rotational direction, thereby removing said wafer;

translating said housing by a predetermined distance in a first longitudinal direction;

rotating said substantially cylindrical member by substantially ninety degrees in said first rotational direction;

swiveling said end effector in said first swivel direction, thereby releasing said wafer;

rotating said substantially cylindrical member by substantially ninety degrees in said second rotational direction; and

translating said housing by said predetermined distance in a second longitudinal direction opposite said first longitudinal direction, thereby returning said housing to said home position, said translation in said second longitudinal direction occurring concurrently with said steps of rotating and cleaning said wafer.

12. The method according to claim 11, further comprising directing a fluid spray from a fluid dispensing nozzle onto said wafer substantially continuously during said transfer of said wafer by said wafer transport assembly, said fluid dispensing nozzle being attached to at least one of said at least two substantially parallel members in a substantially constant position and orientation relative to said wafer.

13. The method according to claim 11, wherein said mounting/alignment block enables alignment between each of said at least two substantially parallel members and said substantially cylindrical member in three translational and three rotational degrees of freedom.

14. The method according to claim 1, wherein the step of rotating is performed using a wafer drive assembly comprising a rotatable ring assembly incorporating an annular ring and means for clamping said wafer in a plane offset from and parallel to the plane of said ring assembly.

15. The method according to claim 14, wherein said means for clamping comprises:

a preloaded torsion spring lever swivelably attached to said annular ring;

a slidable clamp attached to said preloaded torsion spring lever adjacent a first end of said preloaded torsion spring lever, said slidable clamp gripping an edge of said wafer throughout the step of rotating;

a contact pin attached to said preloaded torsion spring lever adjacent a second end of said preloaded torsion spring lever opposite said first end; and

an actuator that applies pressure radially to said contact pin, causing said preloaded torsion spring lever to swivel on said annular ring, thereby withdrawing said slidable clamp from said wafer, said preloaded torsion spring lever returning under spring tension to engage said wafer with said slidable clamp, when said actuator ceases to apply pressure to said contact pin.