ME-250 Precision Machine Design Semiconductor Lithography Tool

1
ME-250 Precision Machine Design Semiconductor
Lithography Tool

• Alok Bhatt
• Sarang Deshpande
• Instructor Dr. B. J. Furman
• Mechanical and Aerospace Engineering Department
• San Jose State University
• Fall 2004
• 21st Oct 2004

2
Overview

• Traditional lithography tool
• Precision aspects involved
• Concept of HTM
• Moving interferometer wafer stage
• Precision aspects involved
• Precision concepts in interference lithography
• References

3
Schematic of Photolithography Tool
__________________________________________________
__________________________________________________
_______ Source www.binnard.com/SJSUlitho.ppt
4
Schematic Diagram of Photolithography Tool
Components of the lithography tool 10 Linear
Motor 66 Wafer Table 68 Wafer 72 Metrology
Frame 74 Illumination Assembly 76 Reticle 78
Lens 80 Photomask 102 Wafer Stage Base 104
Wafer Table 106 Flexures 112 - Encoders 122
Vibration Isolators 124 Vibration
Isolators 126 Air Bearings 201 AF/AL
Emitter 202 AF/AL Receiver 203 Voice coil
Motor
z
Reticle Stage
x
Y
Lens
Linear Motor 2X
Wafer Stage
Voice coil Motor 2X

• __________________________________________________
  __________________________________________________
  _____________
• Source www.uspto.gov (US Patent 6,686,991)

5
Precision Engineering Principles Involved

• Two linear motors provide motion to wafer stage
  in Y-axis. Plurality of motors eliminates Abbe
  Error
• Three voice coil motors for positioning the wafer
  table relative to wafer stage in Z-axis
• Two flexures to restrict the planner motion of
  the wafer table in X and Y axis, while allowing
  its motion in Z-direction
• Vibration isolators to resist the vibrations to
  transfer from base to wafer stage
• Air bearings are used between wafer stage and
  wafer base. A thinner layer of pressurized air is
  applied while vacuum holds the stage in position
• AF/AL (Auto Focus/ Auto Level) sensors provide
  the position of exposure point relative to the
  wafer
• Plurality of encoders (112) determines the
  position of wafer table relative to wafer stage

Flexures
Encoders
Vibration Isolators
Air Bearings

• __________________________________________________
  __________________________________________________
  _______
• Source www.uspto.gov (US Patent 6,686,991)

6
Concept of HTM Utilized In Positioning of Wafer
Stage

• r are position vectors
• R are the coordinate rotations
• Coordinate Frame O is reference coordinate
  system
• O1 is coordinate frame for wafer stage
• O2 is coordinate frame for wafer stage base
• O3 is coordinate frame for wafer table
• O4 is coordinate frame for lens
• Six different encoders determine position of each
  coordinate system and put them into a matrix form
• Position of each coordinate system relative to
  the reference coordinate system is then
  determined by homogeneous transformation matrices
  (HTM)

__________________________________________________
__________________________________________________
__________________ Source www.uspto.gov (US
Patent 6,686,991)
7
Moving Interferometer Wafer Stage (Vertically
Mounted)
Components of the wafer stage assembly 10
Wafer Stage 11 Right handed Cartesian
coordinate system 12 Wafer 14 16 Laser
Gauge Type Interferometers 22 24 Penta Prism
Beam Splitter 26, 28 38 Beam Folder/Fold
Mirror 34 Laser 37 Beam of light 40
Wavelength Monitor 30 32 Two Orthogonal
Reference Mirrors 35 - Travel of Mirror in
X-Direction
Present Invention of Moving Interferometer Wafer
stage
__________________________________________________
__________ Source www.uspto.gov (US Patent
5,757,160)
8
Moving Interferometer Wafer Stage (Vertically
Mounted)

• Distinct Features
• The wafer stage typically has 3 DOF
• Interferometers move with wafer stage
• Two stationary orthogaonal return interferometer
  mirrors for accurate alignment and positioning,
  placed off the moving stage
• Objectives
• To reduce the errors in positioning and alignment
  
• To reduce the size and weight / to increase the
  travel distance
• Advantages
• Lower power laser illumination source can be used
• It is more tolerant of rotation or twisting of
  the wafer stage
• Elimination of Abbe Offset error by mounting the
  interferometers in or close to the wafer plane

__________________________________________________
__________ Source www.uspto.gov (US Patent
5,757,160)
9
Moving Interferometer Wafer Stage (Perspective
View)

Components of the wafer stage assembly 12
Wafer Chuck 14 16 Laser Gauge Type
Interferometers 22 24 Penta Prism Beam
Splitter 30 32 Two Orthogonal Reference
Mirrors 34 Laser 37 Beam of light 42 Air
Bearing in triangular arrangement 44, 46, 48 52
Beam Folder/Fold Mirror 54 - Arm 56 Reference
Mirror 58 Counter Force Cylinder 60 Support
62 Liner Drive/ Motor 64 - Travel of wafer
table in X-Direction 66 Calibration Detector
__________________________________________________
__________________________________________________
____________________________ Source
www.uspto.gov (US Patent 5,757,160)
10
Precision Engineering Principles Involved

• Elimination of Abbe Offset error by mounting the
  interferometers in or close to the wafer plane
• The wafer stage rides on three air bearings
  placed in a triangular arrangement which is an
  example of a kinematically mounted wafer stage
• By placing the mirrors off the wafer stage, the
  mirrors can be made lager, more stable and can be
  manufactured more accurately at lower cost
• The wafer stage can be made smaller and of less
  weight
• Wafer stage rotation accuracy is also improved by
  increasing the separation of the paired
  interferometers without increasing the size of
  the wafer stage

__________________________________________________
__________________________________________________
____________________________ Source
www.uspto.gov (US Patent 5,757,160)
11
Precision Concepts In Interference Lithography
__________________________________________________
__________________________________________________
___________________ Source http//snl.mit.edu/pap
ers/presentations/2003/Schattenburg/Schattenburg-D
ARPA-2003.pdf
12
References

• 1) Precision Engineering in Semiconductor
  Lithography, Binnard M., Nikon Reaserch
  Incorporation of America, Oct 5, 2004.
• www.binnard.com/SJSUlitho.ppt
• 2) Wafer stage assembly, servo control
  system, and method for operating the same,
  Binnard, et al., US patent 6,686,991, Feb 3,
  2004.
• http//patft.uspto.gov/netahtml/srchnum
  .htm
• 3) Moving interferometer wafer stage,
  Kreuzer, US patent 5,757,160, May 26, 1998.
• http//patft.uspto.gov/netahtml/srchnum
  .htm
• 4) Nano-metrology using the Nanoruler, M.L.
  Schattenburg, P. Konkola, C. Chen, R.K. Heilmann,
  C. Joo, J. Montoya and C.-H. Chang, Defense
  Advanced Research Projects Agency (DARPA) -
  Advanced Lithography Program Review, Santa Fe,
  New Mexico, May 5-8, 2003.http//snl.mit.edu/pape
  rs/presentations/2003/Schattenburg/Schattenburg-DA
  RPA-2003.pdf