Semicon Europa Wafer Chucks for Lithography. Berliner Glas KGaA Herbert Kubatz GmbH & Co. Sven Götze

Transcription

1 Semicon Europa Wafer Chucks for Lithography. Berliner Glas KGaA Herbert Kubatz GmbH & Co. Sven Götze 1

2 Export driven, medium-sized, innovative. Solutions in Optics High Tech in Glass Legal form: private-owned company Executives: Dr. Herbert Kubatz, Dr. Andreas Nitze Sales 2010: 140 million Euro 2 Business areas: Photonics and Technical Glass

3 Close to the customer. Always there. Production area worldwide: 50,075 m 2 Staff worldwide: around 1,000 Sales worldwide: 5% Heerbrugg Berlin Schwäbisch Hall Syrgenstein Germany EU USA Asia 25% 31% 39% California Wuhan

4 A broad base. Highly specialized. Semicon Medical Applications Geosystems/ Metrology Industrial Solutions Defense Technical Glass Lithography/ EUV Inspection equipment Ophthalmology Dentistry Dermatology Endoscopy Fluorescence diagnostic Geodesy instrumentation Photogrammetry Laser tracker Scanning devices Quality control devices Space Film technology Printing technology Laser technology Day/Night observation Distance measurement Aiming optics Thermal imaging Warning-/ landing system Head-up display TV & Public Monitor & Mobile Glass for Devices Surface Technology Biometric detection

5 Products. Wafer Chucks. Applications of Wafer Chucks Vacuum Chucks for Deep UV Electrostatic Chucks for Extreme UV 5

6 Applications of Wafer Chucks. Wafer Chucks are not only used in lithography. Wafer Transport Coating Photolithography Nano-Imprint Plasma Etching Wafer Handling Wafer Inspection Wafer Bonding MEMS Packaging Fabless Waferfabs Inspection Chip Design Polishing Coating Lithography Post Treatment (Etching/Packaging/Dicing) 6

7 Vacuum Chucks for Deep UV Working Principle. When to use a Vacuum chuck: Atmospheric environment conditions (e.g. no vacuum) Very fast chucking and de-chucking (ms-regime) Flat and homogeneous chucking of the work piece Clamp function work in both directions: The chuck clamps on the ground (stage, work bench etc.) The chuck holds the work piece (e.g. wafer) The chucking and de-chucking speed depends on: The vacuum supply technology Chuck design (vacuum volume, required flow) Berliner Glas is used to support customized designs 7

8 Vacuum Chucks for Deep UV. Material. Ideal: Low density, low CTE, low wear, high stiffness, high elasticity, high heat conductivity This is the unobtainable unobtainium A compromise is to make use of compensating material parameters e.g. low heat conductivity can be compensated in some cases by a very low thermal expansion coefficient Two families of materials are used for litho chucks: Near Zero CTE materials (Zerodure, ULE, Cordierite) High heat conductivity materials (SiC, SiSiC, AIN3, SiN4) Another compromise is to use material combinations 8

9 Vacuum Chucks for Deep UV. Manufacturing scheme of a Wafer. Slicing the disk Precision CNC machinging of the raw blank Grinding and polishing of the blank Structuring Coating/qualification of the coating Interferometric measurement of flatness 9

10 Electrostatic Chucks for Extreme UV. Working principle. Electrostatic chucks use the electrostatic force of a potential difference between the chuck electrode and the substrate to chuck that substrat They can achieve clamping forces equal or higher then vacuum chucks If designed and driven in the right way they can achieve short clamping and de-clamping times of less then a second Electrostatic chucks are the chucks that are used for EUV lithography dielectricum electrodes insulating material 10

11 Electrostatic Chucks for Extreme UV. Electrostatic chucks principle. Johnsen-Rahbek chuck Potentially higher chuck field strength Often long chuck and de-chuck times (up to days) Volume resisitance about 10 9 to Ω cm e.g. Zerodure or BF33 Coulom chuck Chuck force limited by breaktrough voltage of dieletric Chucking force instandly follows applied voltage Less chuck force per voltage Volume resistance > Ω cm e.g. Quartz, Sapphire, ULE dielectric w/ finite resistance substrate dielectric electrode body dielectric = insulator The best solution for EUV-chucks are Coulomb chucks due to their fast chucking 11

12 Electrostatic Chucks for Extreme UV. Electrode principle. Unipolar chucks Only one eledtrode in the chuck Reticle or wafer has to be grounded Homogeneous force over the full wafer or reticle Bipolar chuck Two electrode areas with opposite polarity In the polarity change area a forceless line is unavoidable No grounding contact on reticle or wafer necessary The best solution for EUV-chucks are bipolar chucks to avoid wafer grounding 12

13 Electrostatic Chucks for Extreme UV. Materials. Combinations of different materials are needed (glass, glass-ceramics and ceramics) Electrostatic chucks typically consist of a base material and a dielectric layer with the conductive electrode layer in-between If the base material is conductive there needs to be an insulation layer between eletrode and base material It is advantageous to have very low CTE s like the 2*10-8 /K of Zerodur and ULE Bonding becomes one of the key technologies (gluing, physical bonding, anodic bonding) dielectric ( µm) electrode (nm) isolation (µm) body (mm) 13

14 Electrostatic Chucks for Extreme UV. Thermal stabilization. The Silicon wafer has a CTE of about 2*10-6 /K and changes size and shape if it is cooled or heated If a Zero CTE chuck is used with high clamp force, it can keep the wafer in its shape for the time that is needed for illumination If no Zero -CTE materials like Zerodur and ULE can be used the part which is chucked needs thermal stabilization This can be achieved by conditioning by a liquid that flows through buried channels of the base material Cooling channels in SiC In this case it is also important to use good heat conducting chuck materials If the contact surface is reduced by burls or rings a backfill gas between the burls can be used to allow a heat transfer between chuck and chucked part 14

15 Electrostatic Chucks for Extreme UV. Why do chucks need microstructures. Low sticking compared to flat non-structured surfaces Lower chance of particles to be printed through Typical structures to reduce the contact surface are Rings or spirals Uniform or non-uniform distributed burls Especially with burls the contact surface can be reduced up to a factor of 100 A burled or ring structured surface is more sensitive to wear and may need a protective coating Processes for structuring are etching, coating, sandblasting, laser 15

16 Test & Qualification. Electrostatic and Vacuum Chucks. Semiconductor applications require to prove flatness's of down to 100 nm global and 2 µrad local That is done by functional tests in a stack and direct surface measurements The stack measurement requires: Use of high precision reference wafers and reference reticles Advanced chuck and wafer cleaning to avoid particle between wafer and chuck Phase shifting interferometers matching the size of the test wafers 16

17 Reference S. Mack (1997) Eine vergleichende Untersuchung der physikalisch-chemischen Prozesse an der Grenzschicht direkt und anodischer verbundener Festkörper. VDI. (Report) Van Elp Jan et. al. Chuck, lithographic projection apparatus, method of manufacturing a chuck and device manufacturing method, US 2004/ E. Loopstra, J. Otten Lithographic apparatus and device manufacturing method United States Patent

18 The challenge is just around the corner. Let us create it together. Berliner Glas KGaA Herbert Kubatz GmbH & Co. Waldkraiburger Strasse Berlin Germany Phone: Fax: chucks@berlinerglas.de 18