Novel Solutions for ESD Sensitive Devices

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Myles Porter
6 years ago
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1 Novel Solutions for ESD Sensitive Devices Chris Schreiber Magnecomp

2 Safely Dissipating ESD Problem Static Charging is created by either Tribocharging or Induction and the uncontrolled transfer of this Electrostatic Charge is fatal to sensitive HDD Heads. Solution Bleed this charge to ground through a semi conductive suspension element 2

3 Increasing Head Sensitivities Giant Magneto-resistive (GMR) Heads Giant magneto-resistor (GMR) heads are the evolution of the MR designs. GMR heads offer enhanced signal fidelity thereby supporting the ever increasing areal density trend. This more dense GMR technology results in increased ESD sensitivity (30 V). Tunneling Magneto-Resistive (TMR) Heads Tunneling MR (TMR) head are the emerging technology which are even more sensitive to ESD (10V). 3

4 Semiconductor ESD Roadmap Static control recommendations of ITRS 2003 (most recent). Mid 90 s MR Head Introduced MR Head is ESD Sensitive <30V HDD leads Semicon by >10 years on ESD Device type MR heads & RF FETs Power MOSFETs laser diodes Pre VLSI Modern VSLI CMOS ESD withstand voltage sensitivity (V) HBM V V V V 4

5 Desirable ESD Coating Attributes Stable Resistivity between Ohm Achieve Tribocharge < 8 Volts Achieve Static Decay < 0.3 Sec Exceed OEM system LPC requirements Ambient Temperature T Process low residual stress Applicable regardless of circuit source No Solvents, Outgas or Chemical Effluent Durable, Immune to Chemistries, UV and Humidity 5

6 ESD Dissipative Materials Desired Range Conductive Polymers Sputtered Metals SP-3 Carbon Filler Ion Complex Surfactant Ohms/Square 6

Thin Metal Chrome SP-3 < 10 4 Ohm/square Humidity Dependant

7 Suspension Applicable Solutions Conductive Polymers Poor LPC < 10 5 Ohm/square Carbon >10 5 <10 9 Ohms/square Sputtered Thin Metal Chrome SP-3 < 10 4 Ohm/square Humidity Dependant DLC Ion Complex >10 5 <10 9 Ohms/square >10 5 <10 9 Ohm/square 7

8 Characteristics of ESD Solutions Property Ion Complex Carbon Black Conductive Polymer Metal SP-3 Transparency Excellent Poor Excellent No to Good Good Surface Resistivity > Water Resistance Poor Good Excellent Excellent Excellent Humidity Issues Yes No Few No to Marginal No Permanency Poor Yes Good Yes Yes LPC Marginal Poor Marginal to Good Low Low LT reliability Questionable Good Yes Yes Yes Ultrasonic Clean (V) Good Poor Good Good Excellent Application Dip Dip/Compound Dip Vac. Dep. Vac. Dep. Thickness (um) FTIR Pass Pass Pass Pass Pass Shelf Life Poor Poor Marginal to Good Good Good IC Poor Marginal Good Good Good 8

9 Film Structure Coating Structure 9

chamber RF ion beam Vacuum chamber plasma bridge neutralizer 100% ionized plasma Low Temperature coating

10 SP-3 3 Filtered Cathodic Vacuum Arc Technology (FCVA) Substrate bias Focusing magnetic field Carbon plasma Substrate Filter field arcing Etching source Striker Vacuum arc supply Optical viewport Gas discharge chamber RF ion beam Vacuum chamber plasma bridge neutralizer 100% ionized plasma Low Temperature coating Excellent uniformity (< 5%) Low residual stress and no out gassing In-line process for high volume production 10

11 High-resolution TEM image A A area HREM image Polyimide Carbon coating layer 1. The HREM Image showed an very smooth and clear interface. 2. The interface between carbon coating layer and coverlay showed very good bonding behavior. 3. All layers are amorphous. Coverlayer 11

12 ESD Coating KPOV s Stable Resistivity between Ohm Achieve Tribocharge < 8 Volts Achieve Static Decay < 0.3 Sec No significant effect on Impedance Exceed OEM system LPC requirements Immune to Ultrasonic Washing & Solvents 12

13 Electrical and HAST Conditions Ambient Environment o 65% RH Resistivity: 10 Volt/ 15 sec charge Tribocharge: Nitrile Glove - Rub 7-times Static Decay, 1KV charge, 10% cut off HAST Groups Group 1: Not Coated Group 2: SP-3 Coated Group 3: SP-3 85 o C, 85% RH 120 hrs. Group 4: SP-3 US 69Hz (18W/gal) 30 min Group 5: SP-3 US 69Hz (18W/gal) 90 min 13

14 Particle Counts 14

15 Impedance Impact TDR Diff. Impedance (ohm) Coated Rd 32ps Coated Rd 100ps Coated Rd 400ps Coated Rd 500ps NonCoated Rd 32ps NonCoated Rd 100ps NonCoated Rd 400ps NonCoated Rd 500ps Coated vs. Non-Coated SP Time (ps) Impedance exhibits no differences between coated and non-coated samples, Irrespective of rise time. 15

16 Tribocharge Only the Non Coated Parts Showed Tribocharge Above 8 Volts Tribocharge (Volt) Not coated SP-3 SP-3/Env SP-3/US-30min SP-3/US-90min

Robust Ground Interconnect Performance Target: Reliable ground path able to withstand 90 minutes ultrasonic cleaning Resistance < 1 Ohm Result of 0.

17 Robust Ground Interconnect Performance Target: Reliable ground path able to withstand 90 minutes ultrasonic cleaning Resistance < 1 Ohm Result of 0.3um thick coating between ground lead and SST. Resistance (Ohm) Ground to Lead Resistance Sample # 15 samples with stable Ohm resistance 17

18 Surface Resistivity 1.00E E+12 Resistivity (Ohm) 1.00E E E E E+07 SP-3 SP-3/Env SP-3/US-30min SP-3/US-90min Not Coated 1.00E+06 Sample# 1-15 The SP-3 Coating remains stable post 85/85 and 90 minutes Ultrasonic Cleaning 18

19 Static Decay Post HAST Test Decay (Sec) SP-3 SP-3/Env SP-3/US-30min SP-3/US-90min Sample# 1-15 The SP-3 Coating retains static decay <.3sec post HAST Testing 19

20 ESD Flexure Solution Summary Customers will need additional ESD protection in the future However, it is still unclear which ESD protection method will prevail. When more sensitive head designs emerge that require enhanced ESD protection, a few usable solutions exist. The industry must weigh the financial and performance tradeoffs to determine which ESD solution to implement. Tetrahedral Amorphous Carbon (ta-c) (SP-3); provides a robust and wear resistant solution for tribocharge regardless of circuit source. Metallic coatings particularly in additive circuits have numerous beneficial attributes. MPT is actively developing effective ESD Solutions with balanced trade-offs. 20

Measurement And Reduction of Particulate Contamination in HDD

Measurement And Reduction of Particulate Contamination in HDD Phil Lei Carl Newberg Chris Schreiber Magnecomp Precision Technology September, 2006 1 Overview The effect of particles in Hard Disk Drives