VEECO FPP-5000 4-Point Probe Operating Manual Version: 1.0 May 2013 UNIVERSITY OF TEXAS AT ARLINGTON Nanofabrication Research and Teaching Facility
TABLE OF CONTENTS 1. Introduction....2 1.1 Scope of Work....2 1.2 Description.. 3 1.3 Safety.....3 2. Hardware.......4 3. Requirements.......5 3.1 Training.......5 3.2 System Restrictions........5 4 Operating Procedures........6 4.1 System Pre-Checks....6 4.2 Operating the VEECO FPP-5000 4-Point Probe..7 5 Recipes........ 11 5.1 Technical Information...11 1.0 INTRODUCTION 1.1 Scope These procedures apply to the VEECO FPP-5000 4-Point Probe test unit. All maintenance should follow the procedures set forth in the manufacturer s maintenance and operations manuals. This document is for reference only. Users must be trained by Nanofab staff before operating this equipment. 2
1.2 Description The VEECO FPP-5000 4-Point Probe simplifies the measurement of resistive properties of semiconductor wafers and resistive films. FPP-5000 has been designed to permit direct computation of V/I, sheet ( / ) or bulk resistivity, metallization thickness and P-N type testing. The unit supplies a constant current and displays either the resultant V/I, sheet resistance of the sample in ohms/square ( / ), bulk resistivity, thickness and dopant type depending on which keyboard programming function has been selected. The tool also has a penetrate function that permits a high energy pulse to be applied to break through the thicker native or surface oxide layers. Resistive properties can be measured on samples ranging from 5mm X 5mm to 5 diameter wafers and with wafer or film thickness < ½ probe spacing ( S ). 1.3 Safety 1.3.1 This machine is connected to HIGH VOLTAGE. Be very careful and remain aware of electrical hazards. If you encounter any electrical malfunctions, contact NanoFAB staff immediately 1.3.2 The probehead can easily be damaged; do not bump anything in to the probes. 3
1.3.3 Users are not allowed to adjust the platen height or clean the probe-head For any platen or probe-head issues call staff. 1.3.4 Read any posted NanoFab Engineering Change Notices (ECN) for any hardware, process or safety changes before running the tool.. 2.0 HARDWARE 2.0 Microprocessor based electronics permits direct computation of V/I, sheet resistance ( / ), bulk resistivity ρ (ohm-cm), metallization thickness ( µ, Å, mils ) and PN type testing. 2.1 Stage can accommodate 5mm X 5mm samples to 5 diameter wafer. 2.2 Indexing wafers holders allows repeatable probe positioning at the center of wafers and samples. 2.3 PEN function will supply short low-energy, high voltage pulse to penetrate thicker surface oxides (1kÅ SiO 2 and up to 2kÅ Al 2 O 3 ) 2.4 Keyboard programming of sheet resistance, bulk resistivity, layer thickness ( if ρ ohm-cm is known), RETEST button. 2.5 Probehead is material is made of Tungsten Carbide (WC) with 50um tip radius and probe spacing of 1.588mm. 2.6 Sheet resistance ( / ) measurement range is from 1.1x 10-3 / to 4.50 x 10 5 /. 2.7 Bulk resistivity ( ρ ) range from 4.19 x 10-5 Ohm-cm to 1.71x 10 3 Ohm-cm. 4
3.0 REQUIREMENTS 3.1 Training All users must be trained and authorized on the VEECO FPP-5000 4-Point Probe. Training is supplied by a Nanofab staff member please contact the tool owner to schedule training. 3.2 System Restrictions 3.2.1 Users are NOT allowed to adjust, clean or remove probe-head. Users are also NOT allowed to adjust the platen height. For any probe-head contact issues call staff. 3.2.2 The probehead can easily be damaged; do not bump anything in to the probes. 3.2.3 The material must be capable of being probed (Ge, Si, and metals).if you are not sure ask staff about the material you want to probe. 3.2.4 Only measure clean dry samples. Native oxide will impede good ohmic contact. 3.2.5 If a sample has a layer it must be opposite conductivity type to the substrate in order to electrically insulate this layer from the substrate. The doped layers should also have uniform homogenous doping. 3.2.6 FPP can measure very resistive materials such as metals to higher resistivity materials with thickness from 100A to 1µm. Bulk resistivity range from 4.19 x 10-5 Ohm-cm to 1.71x 10 3 Ohm-cm. 3.2.7 Sheet resistance ( / ) measurement range is from 1.1x 10-3 / to 4.50 x 10 5 /. 3.2.8 For thin layers (< 1µm) avoid puncturing the layer by excessive needle loading or rapid decent velocity of the platen cover. 3.2.9 This system requires a NanoFab Management System reservation before using. http://nanofabreservation.uta.edu/ 5
4.0 OPERATING PROCEDURES 4.1. System Pre-Checks 4.1.1. The FPP 5000 should already be plug into the power strip, check for this before you start. If the tool is ON as shown continue to the next section. (To recalibrate the unit you will need to power down and power up the unit) 4.1.2. Lift the platen lid carefully and inspect for broken wafer chips or debris. If platen or plastic wafer holders are dirty clean with IPA and clean room paper. If you see the probe tips are dirty call staff to inspect and wipe clean using a non-abrasive method. 6
4.2. Operating VEECO FPP-5000 Four-point Probe System 4.2.1. If you have not completed the System Pre-Checks in steps 4.1.1 4.1.2 then you must complete those before proceeding. 4.2.2. Raise the platen lid and place the appropriate size wafer holder on the platen and adjust the rear stop adjustment thumbscrew to prevent the wafer from moving and to center the probes near the center of you wafer. 3 wafer holder small sample holder 4.2.3. Place your wafer or sample you want to probe with the film or wafer side facing down to contact the probes. Note: For small sample pieces place the sample on the probes so the probes are contacting the sample within 10% of the samples center area and the probes are approximately equidistant from the sample edges. This will minimize edge measurement affects. For extremely small samples where the sample Diameter (D) divided by the probe spacing (S) is less than 40 (D/S < 40) geometric correction factor should be used. Enter the correction factor using the keyboard. Once entered subsequent V/I, Sheet Resistance and resistivity will be multiplied by this correction factor. See section: Samples close to the thickness of a typical silicon wafer 100 m to 1 mm (1000 m ) can only be measured 7
4.2.4. Place the appropriate size backing plate with the spiral side facing the wafer or sample. 4.2.5. Turn the FPP 5000 power switch ON located on the back cover. The front panel LED display will initialize and do a self-test. All LED will turn ON as shown All LED s turn ON 4.2.6. Press the CLEAR button, then press the SLICE button (ρ measurement). 4.2.7. Press the PGRM button to enter the samples thickness.. PGRM 8
4.2.8. Enter your samples thickness using the numeric keypad. The 1 st three digits entered are the thickness entries. The 4 TH digit is the X10 exponent value. As an example 5250Å thickness would be entered as follows: The 1 st three digits entered are the thickness entries. 5 entered: display shows 0.5 2 entered: display shows 0.52 5 entered: display shows 0.525 The 4 TH digit is the X10 exponent value 4 entered: display shows 0.525 X 10 4 After the exponent has been entered select the unit s button µ, Å, or MIL. 4.2.9. Then press the STORE button to save the thickness value in the program. Press the PRGM to exit the programming mode. STORE PRGM 9
4.2.10. Slowly lower the platen cover to make contact between the probes and wafer surface. Do not use excessive downward velocity or force, use enough force to make contact for the measurement. 4.2.11. Press the test button as shown to measure ρ measurement. 4.2.12. To calculate V/I, Sheet Resistance, PN Type press the appropriate buttons. 4.2.13. When finished measuring your sample, raise the platen lid and remove your sample. Lower the platen lid after removing your wafer. 10
4.2.14. Turn the FPP 5000 power switch OFF located on the back cover. 4.2.15. Enter the required information in the logbook. 5 Technical Information 5.1 Calculation of resistivity 5.1.1 For bulk resistivity for wafers and films where t s < 0.5 and where t is thickness in cm. ρ = R sh x t { for t/s < 0.5 } 5.1.2 For wafer thicknesses that exceed 0.625 x probe spacing use the following FPP thickness correction factors. 5.1.3 For small size sample geometries of the testing area use the following FPP sample diameters correction factors 5.1.4 References and links : 11
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