Research Papers

In-Line Dimensional Metrology in Nanomanufacturing Systems Enabled by a Passive Semiconductor Wafer Alignment Mechanism

[+] Author and Article Information
Tsung-Fu Yao, Andrew Duenner, Michael Cullinan

University of Texas at Austin,
Austin, TX 78712

Contributed by the Manufacturing Engineering Division of ASME for publication in the JOURNAL OF MICRO- AND NANO-MANUFACTURING. Manuscript received August 24, 2016; final manuscript received September 1, 2016; published online November 9, 2016. Editor: Jian Cao.

J. Micro Nano-Manuf 5(1), 011001 (Nov 09, 2016) (8 pages) Paper No: JMNM-16-1036; doi: 10.1115/1.4034634 History: Received August 24, 2016; Revised September 01, 2016

One of the major challenges in nanoscale manufacturing is defect control because it is difficult to measure nanoscale features in-line with the manufacturing process. Optical inspection typically is not an option at the nanoscale level due to the diffraction limit of light, and without inspection high scrap rates can occur. Therefore, this paper presents an atomic force microscopy (AFM)-based inspection system that can be rapidly implemented in-line with other nanomanufacturing processes. Atomic force microscopy is capable of producing very high resolution (subnanometer-scale) surface topology measurements and is widely utilized in scientific and industrial applications, but has not been implemented in-line with manufacturing systems, primarily because of the large setup time typically required to take an AFM measurement. This paper introduces the design of a mechanical wafer-alignment device to enable in-line AFM metrology in nanoscale manufacturing by dramatically reducing AFM metrology setup time. The device consists of three pins that exactly constrain the wafer and a nesting force applied by a flexure to keep the wafer in contact with the pins. Kinematic couplings precisely mate the device below a flexure stage containing an array of AFM microchips which are used to make nanoscale measurements on the surface of the semiconductor wafer. This passive alignment system reduces the wafer setup time to less than 1 min and produces a lateral positioning accuracy that is on the order of ∼1 μm.

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Fig. 1

(a) A single chip AFM, (b) packaged instrument, and (c) layout of MEMS chip [2]

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Fig. 2

(a) Designed XY precision stage for multiple single-chip AFMs inspection, (b) in-line dimensional metrology system setup, (c) Z-axis approach mechanism, (d) prototype alignment mechanism, and (e) measurement procedure

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Fig. 3

Wafer alignment naming conventions

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Fig. 4

Instantaneous centers of rotation

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Fig. 5

Nesting force window

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Fig. 6

Experimental setup

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Fig. 7

Translational repeatability results

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Fig. 8

Rotational repeatability results

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Fig. 9

X-axis repeatability trials

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Fig. 10

Y-axis repeatability trials

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Fig. 11

Angular repeatability trials

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Fig. 12

Simple model of double parallelogram flexure mechanism

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Fig. 13

XY precision stage with the double parallelogram flexure mechanism

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Fig. 14

Mapping of stiffness varied with beam length (L) and flexure width (w)

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Fig. 15

A demonstration of how to securely assembly micrometer with truncated balls

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Fig. 16

Fine Z motion by symmetric flexure design coupled with voice coil actuator

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Fig. 17

Photos show (a) flexure-based stage, (b) specimen stage, (c) stage assembly, and (d) AFM chip put underneath of flexure stage

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Fig. 18

Setup for parasitic motion test

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Fig. 19

Capacitance probe setup

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Fig. 20

Schematic drawing for the single-chip stage parallelism

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Fig. 21

AFM images taken using fast setup system: (a) One-dimensional grating sample which is 500 nm step structures with 3 μm pitch and (b) Two-dimensional grating sample, 100 nm height grid with 500 nm spacing. The units are shown in pixels.




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