Wafer alignment jig for wafer-handling systems

Details Wafer alignment jig for wafer-handling systems Wafer alignment jig for wafer-handling systems

1999-07-30

2002-07-30

Bennett, G. Bradley (Department: 2859)

Measuring and testing

Instrument proving or calibrating

Displacement, motion, distance, or position

C414S936000, C033S645000

Reexamination Certificate

active

06425280

ABSTRACT:

TECHNICAL FIELD
The present invention relates generally to semiconductor manufacture and, more specifically, to alignment of wafers within lithography tools.
BACKGROUND OF THE INVENTION
In the manufacture of semiconductors, circuitry patterns are commonly transferred by lithography to multiple chips on a single semiconductor wafer. The lithography process generally comprises coating the wafer with a photoresist, exposing the photoresist in a pattern corresponding to the circuitry pattern desired, and developing the wafer to remove the photoresist in the exposed areas. Further processing, such as etching steps, may then follow using the patterned photoresist as a mask.
Because of the submicron-level resolution of the circuitry patterns and the constant drive to produce quality products with zero defects, the importance of aligning semiconductor wafers properly on the lithography tools is increasing. In an exemplary lithography configuration
200
, as shown schematically in
FIG. 8
, each semiconductor wafer
202
is handled by a track system
204
that performs the step of coating the wafer with photoresist and then delivers the coated wafer to a lithography tool
206
at a pickup-dismount location
210
. Track system
204
typically uses a robot
212
to transfer wafer
202
. After wafer
202
is delivered by robot
212
of track system
204
, a robotic component of lithography tool
206
, such as a stepper robot
214
, typically picks up the wafer
202
and takes it to a pre-aligner
216
, where the center of the wafer
202
is determined. From the pre-aligner
216
, the wafer
202
travels to the exposure chuck (not shown), where the wafer
202
is precisely loaded for alignment and exposure.
The transfer of wafer
202
from one robot to the other at pickup-dismount location
210
is critical, because the wafer
202
must be perfectly aligned at each step of the process. If the robot
212
of the track system
204
somehow becomes misaligned with the stepper robot
214
of the lithography tool
206
, then the placement of wafer
202
within capture range of pre-aligner
216
(a range, for example a ±4 mm×±4 mm window, within which the wafer center must be located for the wafer
202
to be further processed correctly) may be out-of-tolerance, potentially affecting final product quality. Therefore, the alignment of the robots
212
,
214
with one other at pickup-dismount location
210
must be periodically re-calibrated.
Wafer-handling robots are generally of two types: edge-handling robots that handle the wafer from the edges, and center-handling robots that handle the wafer from the center. Stepper robots are almost exclusively center-handling robots, whereas track robots may generally be edge-handling or center-handling robots. Edge-handling robots are typically aligned to a wafer center position, whereas center-handling robots are typically aligned to a wafer edge position.
Referring now to
FIG. 1
, there is shown a tilt-plate assembly
10
. Tilt-plate assembly
10
is mounted to the lithography tool (not shown in
FIG. 1
) by placement of alignment pegs
20
in corresponding indents (not shown) in the tool. Tilt-plate assembly
10
has an upper side edge
66
and a lower side edge
68
. Tilt-plate assembly
10
is typically held in place by a tensioned cross-piece
22
inserted through a hole
24
and positioned crosswise within an indent
26
. The track system robot (not shown) typically places the wafer (not shown) on tilt-plate assembly
10
with its underside touching only the tool balls on the tooling arms
14
and the tooling post
16
that extend from the tilt-plate assembly
10
.
The lithography tool robot (not shown) then picks up the wafer from tilt-plate assembly
10
for further processing. A known method of calibrating the alignment of the respective robots with respect to wafer placement on the tilt-plate assembly
10
is to draw an arc on each robotic arm in the position where the edge of the wafer should be located when handled by that robot. Misalignment of the wafer edge with respect to the arc drawn on the robot arm indicates misalignment of the robots. To recalibrate, the robot positions are then adjusted by trial and error until the arcs and edges are aligned correctly. This process is time-consuming and not readily repeatable because there is no fixed reference point for both robots.
Thus, there is a need in the industry for a wafer alignment jig for a wafer-handling system that allows fast, repeatable calibration of the alignment of wafer-handling systems with one another.
SUMMARY OF THE INVENTION
To meet this and other needs, and in view of its purposes, the present invention provides a jig for aligning a wafer-handling system calibration location, such as a wafer pickup-dismount location, with respect to a wafer-processing tool. The jig comprises an alignment fixture adapted to be repeatably mounted on the tool and having one or more edge stops. The jig may further comprise an edge-to-center locator adapted to be mounted on the aunt fixture and having a peripheral edge and a center marker. The center marker identifies the precise center of the calibration location when the edge-to-center locator peripheral edge is positioned in contact with the one or more alignment fixture edge stops.
The present invention further comprises a method of aligning a wafer-handling system in a calibration location with respect to a wafer-processing tool. The method comprises the step of (a) mounting a pre-calibrated jig to the tool in the calibration location, the jig comprising an alignment fixture having one or more edge stops. Then, in step (b), a wafer is placed in the calibration location by the wafer-handling system. Next, in step (c), the alignment of the wafer with the alignment fixture is evaluated and, in step (d), the wafer-handling system is adjusted. Steps (b) through (d) are repeated as necessary, in step (e), until the wafer is placed in step (b) so that the wafer is considered aligned with the alignment fixture in step (c).
Before step (a), the jig may be pre-calibrated by (i) mounting the fixture to the tool in the calibration location; (ii) placing a wafer in the calibration location with the wafer-handling system, the wafer having been pre-aligned to the wafer-handling system by a sequentially adjacent processing tool; (iii) adjusting the one or more alignment fixture edge stops to be positioned in contact with the wafer peripheral edge; and (iv) fixing the one or more edge stops in such position.
The calibration location may be a wafer pickup-dismount location for more than one wafer-handling system, in which case the method comprises carrying out steps (a) through (e) for a first wafer-handling system, and then repeating steps (a) through (e) for additional wafer-handling systems until all the systems have been calibrated.
It is to be understood that both the foregoing general description and the following detailed description are exemplary, but are not restrictive, of the invention.


REFERENCES:
patent: 3790051 (1974-02-01), Moore
patent: 5125791 (1992-06-01), Volovich
patent: 5308222 (1994-05-01), Bacchi et al.
patent: 5438418 (1995-08-01), Fukui et al.
patent: 5642298 (1997-06-01), Mallory et al.
patent: 5822213 (1998-10-01), Huynh
patent: 5851102 (1998-12-01), Okawa et al.
patent: 5981966 (1999-11-01), Honma
patent: 6085967 (2000-07-01), Grande et al.
patent: 6131589 (2000-10-01), Vogtmann et al.
patent: 6164894 (2000-12-01), Cheng
patent: 6167322 (2000-12-01), Holbrooks
U.S. application No. 09/363,740, Dennis b. Ames et al., Filed Jul. 30, 1999, entitled Wafer Center Alignment Device and Method of Wafer Alignment.

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