me-250 precision machine design semiconductor lithography tool
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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
ME-250 Fall 2004
Overview
Traditional lithography tool Precision aspects involved Concept of HTM Moving interferometer wafer stage Precision aspects involved Precision concepts in interference lithography References
ME-250 Fall 2004
Schematic of Photolithography Tool
___________________________________________________________________________________________________________Source: www.binnard.com/SJSUlitho.ppt
ME-250 Fall 2004
_________________________________________________________________________________________________________________
Source: www.uspto.gov (US Patent # 6,686,991)
Reticle Stage
Lens
Wafer Stage Voice coil Motor
2X
Schematic Diagram of Photolithography Tool
Linear Motor 2X
Components of the lithography tool10 – Linear Motor66 – Wafer Table68 – Wafer72 – Metrology Frame74 – Illumination Assembly76 – Reticle78 – Lens80 – Photomask102 – Wafer Stage Base104 – Wafer Table106 – Flexures112 - Encoders122 – Vibration Isolators 124 – Vibration Isolators126 – Air Bearings201 – AF/AL Emitter202 – AF/AL Receiver203 – Voice coil Motor
x
z
Y
ME-250 Fall 2004
Precision Engineering Principles Involved
Vibration Isolators
Flexures
Encoders
Air Bearings
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
___________________________________________________________________________________________________________
Source: www.uspto.gov (US Patent # 6,686,991)
ME-250 Fall 2004
______________________________________________________________________________________________________________________
Source: www.uspto.gov (US Patent # 6,686,991)
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)
ME-250 Fall 2004
Moving Interferometer Wafer Stage (Vertically Mounted)
____________________________________________________________Source: www.uspto.gov (US Patent # 5,757,160)
Components of the wafer stage assembly
10 – Wafer Stage11 – Right handed Cartesian coordinate system12 – Wafer14 & 16 – Laser Gauge Type Interferometers22 & 24 – Penta Prism Beam Splitter26, 28 & 38 – Beam Folder/Fold Mirror34 – Laser37 – Beam of light40 – Wavelength Monitor30 & 32 – Two Orthogonal Reference Mirrors35 - Travel of Mirror in X-Direction
Present Invention of Moving Interferometer Wafer stage
ME-250 Fall 2004
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
Moving Interferometer Wafer Stage (Vertically Mounted)
____________________________________________________________Source: www.uspto.gov (US Patent # 5,757,160)
ME-250 Fall 2004
Moving Interferometer Wafer Stage (Perspective View)
________________________________________________________________________________________________________________________________Source: www.uspto.gov (US Patent # 5,757,160)
Components of the wafer stage assembly
12 – Wafer Chuck14 & 16 – Laser Gauge Type Interferometers22 & 24 – Penta Prism Beam Splitter30 & 32 – Two Orthogonal Reference Mirrors34 – Laser37 – Beam of light42 – Air Bearing in triangular arrangement44, 46, 48 & 52 – Beam Folder/Fold Mirror54 - Arm56 – Reference Mirror58 – Counter Force Cylinder60 – Support 62 – Liner Drive/ Motor 64 - Travel of wafer table in X-Direction66 – Calibration Detector
ME-250 Fall 2004
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)
ME-250 Fall 2004
Precision Concepts In Interference Lithography
_______________________________________________________________________________________________________________________Source: http://snl.mit.edu/papers/presentations/2003/Schattenburg/Schattenburg-DARPA-2003.pdf
ME-250 Fall 2004
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/papers/presentations/2003/Schattenburg/Schattenburg-DARPA-2003.pdf
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