Apparatus for cleaving crystals

Details Apparatus for cleaving crystals Apparatus for cleaving crystals

1999-04-22

2001-05-01

Rachuba, M. (Department: 3724)

Severing by tearing or breaking

Breaking or tearing apparatus

Movable breaking tool

C225S096500

Reexamination Certificate

active

06223961

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates generally to methods and apparatus for cleaving crystals, and particularly to methods and apparatus for cleaving crystals in preparation for defect analysis, such as by scanning electron microscopy (SEM).
BACKGROUND OF INVENTION
Cleaving apparatus for cleaving crystals or wafers are known. For example, U.S. Pat. Nos. 3,680,213 to Reichert, 4,228,937 to Tocci, and 4,775,085 to Ishizuka et al. describe various apparatus suitable for breaking or cleaving semiconductor wafers or crystals. In particular, accurate cleaving of wafers is disclosed in PCT published patent application WO 93/04497, corresponding to U.S. patent application Ser. No. 08/193,188, assigned to the present applicant/assignee, the disclosures of which are incorporated herein by reference.
An important application of cleaving is in preparing wafers for scanning electron microscopy (SEM), which is one method used to analyze defects of semiconductor wafers. The apparatus and methods of PCT published patent application WO 93/04497 can be successfully used to prepare wafers for SEM (and even transmission electron microscopy—TEM), but are limited to a minimum size of wafer, this size being about 40×13 mm, in length and width. It is desirable to have a method and apparatus for cleaving smaller crystalline segments, such as semiconductor dice, which are not readily and accurately cleaved with prior art apparatus and techniques.
SUMMARY OF THE INVENTION
The present invention seeks to provide improved methods and apparatus for cleaving small crystalline segments, such as semiconductor dice or small segments which cannot be cleaved with prior art apparatus.
There is thus provided in accordance with a preferred embodiment of the present invention apparatus for cleaving a crystalline segment, including a pair of aligning pins facing a first cleave plane formed on a first side of a crystalline segment, an impact pin facing a second cleave plane formed on a second side of the crystalline segment opposite to the first side, the crystalline segment having a cleave line extend between and generally perpendicular to the opposing leave planes, and an actuator connected to at least one of the aligning pins and the impact pin, for causing relative movement of the aligning pins and the impact pin towards each other, such that the aligning pins abut against the first cleave plane and the impact pin abuts against the second cleave plane.
In accordance with a preferred embodiment of the present invention the impact pin is aligned with the crystalline segment such that an imaginary line extending from the cleave line towards the impact pin substantially intersects a center of the impact pin.
Further in accordance with a preferred embodiment of the present invention the aligning pins are arranged generally symmetrically on opposite sides of the cleave line.
Still further in accordance with a preferred embodiment of the present invention the impact pin is connected to the actuator and the aligning pins are stationary.
In accordance with another preferred embodiment of the present invention the aligning pins are mechanically linked to a knife by means of linkage arms, the knife being movable by the actuator to impact the first cleave plane. Preferably, in such an embodiment, the impact pin is stationary.
Further in accordance with a preferred embodiment of the present invention the linkage arms permit moving the aligning pins and the knife together, but also permit moving the knife independently of the aligning pins.
Still further in accordance with a preferred embodiment of the present invention the aligning pins apply a preload to the crystalline segment.


REFERENCES:
patent: 3207398 (1965-09-01), Forsstrom et al.
patent: 3680213 (1972-08-01), Reichert
patent: 3998201 (1976-12-01), Miura et al.
patent: 4228937 (1980-10-01), Tocci
patent: 4256246 (1981-03-01), Kindel
patent: 4775085 (1988-10-01), Ishizuka et al.
patent: 4790465 (1988-12-01), Fellows et al.
patent: 4837915 (1989-06-01), Willms
patent: 5069195 (1991-12-01), Barozzi
patent: 5740953 (1998-04-01), Smith et al.
patent: WO 93/04497 (1993-03-01), None

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