Radiation imagery chemistry: process – composition – or product th – Registration or layout process other than color proofing
Reexamination Certificate
1999-06-25
2001-06-19
Young, Christopher G. (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Registration or layout process other than color proofing
C430S311000, C430S313000, C430S314000, C430S315000, C438S401000
Reexamination Certificate
active
06248484
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to alignment systems for manufacturing and more particularly to alignment marks employed on parts to be aligned.
2. Description of Related Art
The present invention relates to structures such as semiconductor devices with combination of an active region such as a silicon layer or a silicon substrate. On the silicon layer or substrate there are contact layers and polysilicon layers. During front end processing steps, usually both the polysilicon layers and contact layers are aligned to the active layer; and in such a case, there is a possibility for misalignment between the contact layer and the polysilicon layer. Many circuit designs, demand good alignment of the contact layers with both the active layer and the polysilicon layers. A nine (9) mark Field Image Alignment (FIA) marking system is employed in a system manufactured by Nikon Corporation in which alignment markings are provided on a work piece.
U.S. Pat. No. 4,962,318 of Nishi for “Alignment System for Exposure Apparatus”, assigned to Nikon Corporation describes Field Image Alignment (FIA) markings at Col. 6, line 59 to Col. 7, line 61 and in FIG. 1A thereof. Light from a halogen lamp is directed onto an alignment mark. At Col. 10, line 15 to Col. 11, line 11, such an alignment marking is described as a pattern of stripes raised from the surface of a wafer covered with photoresist.
U.S. Pat. No. 5,808,910 of Irie et al., “Alignment Method” assigned to Nikon Corporation describes a Field Image Alignment (FIA) marking system at Col. 8, line 34 to Col. 9, line 7 and in FIG. 2 thereof.
U.S. Pat. No. 5,783,340 of Farino et al. “Method for Photolithographic Definition of Recessed Features on a Semiconductor Wafer Utilizing Auto-Focusing Alignment” discloses a method for forming an alignment marking formed a several marks in a trench for a stepper.
U.S. Pat. No. 5,401,691 of Caldwell “Method of Fabrication an Inverse Open Frame Alignment Mark” teaches a method of forming alignment marks.
U.S. Pat. No. 5,705,320 of Hsu et al. for “Recovery of Alignment Marks and Laser Marks after Chemical-Mechanical-Polishing” shows method steps for forming topographic alignment marks (topographical features or steps formed in a substrate) located in a window.
SUMMARY OF THE INVENTION
This invention provides a methods for combining a set of active area marks and an interleaved set of polysilicon marks to form a single composite alignment marking.
The invention teaches a method for making a hybrid alignment marking for optimal alignment of three (3) layers comprising:
(a) forming integral alignment marks in a lower layer from the material of the lower layer,
(b) forming alignment ribs on a surface of the lower layer interleaved with the integral alignment marks.
Alternatively this invention provides a method for making a hybrid alignment marking for optimal alignment of three (3) layers comprising:
(1) Forming CD alignment marks by as follows:
(a) forming shallow steps with shallow trenches with low mesas in silicon material,
(b) forming low polysilicon ribs on the low mesas adjacent interleaved with the shallow trenches, or
(2) Forming CD alignment marks as follows:
(a) forming shallow cavities with low ribs in silicon material exposing low cavity surfaces of the silicon material, and
(b) forming low polysilicon ribs in the shallow cavities on the exposed low cavity surfaces surfaces of the silicon material.
In accordance with this invention, a method is provided for forming hybrid alignment markings with a plurality of parallel marks on an active area of a silicon layer on which a multilayer structure are formed by forming initial marks in the active area by modifying the profile of the active area producing an active area surface of the active area with initial marks and then forming on the active area surface a set of interleaved marks from a second, polysilicon layer to form a single composite alignment marking composed of the initial marks and the interleaved marks. One technique is to form shallow steps with shallow trenches with low mesas in the silicon layer followed by forming low ribs of the second, polysilicon layer on the low mesas adjacent interleaved with the shallow trenches. Alternatively, form shallow cavities with low ribs in the silicon layer forming exposed low cavity surfaces of the silicon layer, and then form additional low ribs of a polysilicon layer in the shallow cavities on the exposed low cavity surfaces of the silicon layer.
In another aspect of this invention, the hybrid markings resulting from the process are provided on a workpiece.
REFERENCES:
patent: 4962318 (1990-10-01), Nishi
patent: 5401691 (1995-03-01), Caldwell
patent: 5705320 (1998-01-01), Hsu et al.
patent: 5783340 (1998-07-01), Farino et al.
patent: 5808910 (1998-09-01), Irie et al.
Cheng Alex (Tsun-Lung)
Sajan Marokkey Raphael
Chartered Semiconductor Manufacturing Ltd.
Pike Rosemary L. S.
Saile George O.
Young Christopher G.
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