Intra-cell mask alignment for improved overlay

Details Intra-cell mask alignment for improved overlay Intra-cell mask alignment for improved overlay

2002-12-03

2004-08-31

Tsai, H. Jey (Department: 2812)

Semiconductor device manufacturing: process

Formation of electrically isolated lateral semiconductive...

Having substrate registration feature

C438S381000, C438S945000

Reexamination Certificate

active

06784070

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method and apparatus for aligning masks with semiconductor wafers.
2. Discussion of Related Art
Referring to
FIG. 1
, photolithography typically involves a substrate
101
covered with a photosensitive material or a resist that can be patterned. Patterns to be formed on the substrate
101
can be etched on a mask
102
. The mask
102
can be used to transfer a pattern to the imageable photoresist layer of the substrate
101
. Reduction optics
103
can be used to focus radiation from a light source
104
onto an area of the substrate
101
.
Alignment of the mask
102
to the substrate
101
is important to manufacturing functional devices, and in particular to forming devices having small design rules, e.g., small critical dimensions. Alignment is the process of positioning the mask
102
over a predetermined position on the substrate
101
, wherein the position can be determined relative to alignment marks. Alignment marks help ensure that the mask
102
can be aligned precisely with respect to the wafer
101
.
Traditional alignment methods, wherein the alignment marks are located on a periphery of the chip, show limited performance for small ground rules. This is because, for example, the alignment marks in the periphery can be far away from the structure being patterned, wherein small deviations of the mask from the substrate can be exaggerated as the distance from the alignment mark increases.
Therefore, a need exists for a high-contrast, small alignment mark that can be implemented as means for an intra-cell alignment.
SUMMARY OF THE INVENTION
According to an embodiment of the present invention, a method for intra-cell alignment of a substrate and a mask comprises providing the substrate comprising a photosensitive material and an alignment structure in an intra-cell region of the substrate, providing a mask comprising a phase-shift region, and aligning the phase-shift region to the alignment structure of the substrate.
The method further comprises determining a phase conflict region, and determining the alignment structure of the substrate.
The method further comprises exposing a field of the substrate to actinic light to pattern the photosensitive material.
The alignment structure comprises a dot, a line, and/or a rectangle.
According to an embodiment of the present invention, a wafer comprises a first alignment structure positioned in a periphery of the chip, a plurality of cells formed on a surface of the wafer, and at least one second alignment structure formed between the plurality of cells.
According to an embodiment of the present invention, a method for intra-cell alignment of a substrate and a mask comprises providing the substrate comprising a photosensitive material, a first alignment structure in a periphery region of the substrate and a second alignment structure in an intra-cell region of the substrate. The method comprises providing a mask comprising a phase-shift region, pre-aligning the phase-shift region to the first alignment structure of the substrate, and aligning the phase-shift region to the second alignment structure of the substrate.
Pre-aligning comprises determining a phase conflict region, and determining the first alignment structure of the substrate.
The method comprises exposing a field of the substrate to actinic light to pattern the photosensitive material.
The second alignment structure comprises a dot, a line, and/or a rectangle.


REFERENCES:
patent: 5550074 (1996-08-01), Lin
Liebman, Lars et al.,High Resolution Ultraviolet Defect Inspection of DAP Reticles, Proc. of SPIE 3873, 19thAnnual BACUS Symposium on Photomask Technology, (Dec. 1999), pp. 148-160.

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