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SEMI E1.9-0701 E2 © SEMI 1994, 2004 19 APPENDIX 1 APPLICATION NOTES NOTE: The material in this appe ndix is an official part of SEMI E1.9 and was approved by full letter ballot procedures on December 18, 1998. The recom …

SEMI E1.9-0701

Symbol

Used

Figure

Number

Value Specified Datum Measured from Boundary or Feature Measured to

z28‡ 15 124.5 mm (4.90 in.)

minimum

horizontal datum plane top end of side cassette identification tag

area

z29 11 0.7 mm (0.028 in.)

maximum

each nominal wafer

seating plane

encroachment of cassette side domains

under wafer extraction volume

z99 15 94.5 mm (3.72 in.)

horizontal datum plane recommended center of label on side

cassette identification tag area

* These dimensions define external features that are also required for boxes.

† These dimensions define internal features that are also required for boxes with non-removable cassettes.

‡ These dimensions define optional features.

Table 2 Pitch and Capacity Options

Option

Number

Cassette Capacity

(c)

Wafer Pitch

(z12)

Wafer Clearance

(z11)

Resulting Cassette Height

(z8 – z1 + z12* (c – 1) + z18)

1 13 wafers 10 mm

(0.39 in.)

6 mm (0.24 in.)

minimum

183 mm (7.20 in.) maximum

2 25 wafers 10 mm

(0.39 in.)

6 mm (0.24 in.)

minimum

303 mm (11.93 in.) maximum

3 not yet defined

4 not yet defined

SEMI E1.9-0701

APPENDIX 1

APPLICATION NOTES

NOTE: The material in this appendix is an official part of

SEMI E1.9 and was approved by full letter ballot procedures

on December 18, 1998. The recommendations in this

appendix are optional and are not required to conform to this

standard.

A1-1 The cassette capacity is intended to include one

test wafer. It is recommended that process equipment

be designed for 12 or 24 product wafers, but tool

robotics should reach all slots.

NOTE: The carrier capacity need not be the same as the

transport group size, the process batch size, or the virtual

tracking unit size.

A1-2 The shape of the features holding the wafers is

not specified in this standard. However, a mizo tooth

shape (an exaggerated version of which is shown in

Figure A1-1) is recommended. It is also recommended

that the surface that touches the wafer have a large

radius to minimize stress on the wafer and the

supporting feature. It is recommended that the

supporting feature touch the wafer only on the back

side and far enough away from the edge to avoid

contact with the wafer notch (if any) in any radial

orientation.

wafer

tooth

Figure A1-1

Mizo Tooth

A1-3 In general, it is recommended that the wafer

notch and/or its fiducial identification marks be kept

toward the front of the cassette and the front of the

cassette top extend no farther than y14 from the facial

datum plane, so that the identification marks on the top

wafer can be read without removing the wafer.

A1-4 Extra clearance (larger than the pitch) has been

added below the bottom wafer (for non-random

sequential access to the wafers with a faster or less

precise robot) and above the top wafer (for accessing

the wafers in a vertical orientation), see Section 6.11.

A1-5 If wear at the kinematic couplings is a concern

with plastic cassettes, ceramic or metal inserts can be

used for the mating features.

A1-6 Skewness, warp, rock, and stiffness are implicitly

defined in the geometric tolerances.

A1-7 To increase the stability of the cassette on the

kinematic couplings, the points on the cassette bottom

that are the most distant from the lines connecting each

pair of coupling pins can be made as close as practical

to the horizontal datum plane so that the cassette cannot

tip very far off of the kinematic coupling pins.

A1-8 Figure A1-2 shows several paths for optically

sensing the presence and planarity of wafers in the

cassette. Also shown are the two vertical paths for

sensing how far the wafers protrude.

Figure A1-2

Optical Sensing Paths

SEMI E1.9-0701

A1-9 Figure A1-3 shows a small-footprint cassette that

conforms to the requirements of this specification. In

order to prevent such a small cassette from being set on

the kinematic couplings in the wrong orientation, a

frame such as shown in Figure A1-4 can be placed

around the couplings. In order to not interfere with the

kinematic couplings alignment function, the frame can

extend no further than r19 from the maximum

boundaries of a cassette.

NOTE: If the bottom of the cassette does not extend below

the bottom conveyor rail, the conveyor rail may become

contaminated and may distribute particles.

Figure A1-3

Small-Footprint Cassette

Figure A1-4

Frame to Prevent Misalignment

A1-10 Conveyor rail edges need to be well defined for

smooth guidance and to avoid vibration. Thus, the

minimum radius on the edge that does not create

particles is recommended. For similar reasons, the

tolerance on conveyor rail parallelism and on

dimension x16 should be kept as small as possible for

the materials used.

A1-11 Table A1-1 can be used for communicating

which optional features are present on cassettes that

comply with this specification.

A1-12 In general, info pad A (on the lower left in

Figure 5) was intended to indicates

the carrier capacity

(the number of wafers). For example, info pad A was

previously defined to be in the down position (at z2

above horizontal datum plane) if the carrier holds 13

wafers and was previously defined to be in the up

position (at z26 above horizontal datum plane) if the

carrier holds 25 wafers. Info pad A is intended to be

read with a mechanical switch or optical sensor.

A1-13 In general, info pad B (on the lower right in

Figure 5) was intended to indicates

the carrier type

(cassette or box, etc.). For example, info pad B was

previously defined to be in the down position (at z2

above horizontal datum plane) if the carrier is a cassette

and was previously defined to be in the up position (at

z26 above horizontal datum plane) if the carrier is a

box. Info pad B is intended to be read with a

mechanical switch or optical sensor.

A1-14 Info pads C and D (slightly forward and to the

outside of info pads A and B) are intended to show

whether the carrier is dedicated to the front-end-of-line

(FEOL) part of the fabrication process (before any

metal layers have been deposited on the wafer) or to the

back-end-of-line (BEOL) part of the fabrication process

(during which metal contamination may be present). If

such carrier differentiation is required by the user, info

pads C and D are recommended to be down and up

(respectively) for a front-end-of-line carrier and the

opposite for a back-end-of-line carrier. Info pads C and

D are intended to interact with a mechanical pin. See

application note R1-2 in SEMI 15.1 for a discussion of

how to use pins to differentiate FEOL and BEOL

carriers.