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Www.fairchildsemi.com 1 Wafer Level Reliability. 2 Raw Material Supplier (i.e. Leadframe) Component Manufacturing PC Board Assembly System Assembly End-Use.

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Presentation on theme: "Www.fairchildsemi.com 1 Wafer Level Reliability. 2 Raw Material Supplier (i.e. Leadframe) Component Manufacturing PC Board Assembly System Assembly End-Use."— Presentation transcript:

1 1 Wafer Level Reliability

2 2 Raw Material Supplier (i.e. Leadframe) Component Manufacturing PC Board Assembly System Assembly End-Use Customer Control Points for Emphasis Development Manufacturing FSC Worldwide Quality & Reliability Built-In Reliability Initiative

3 3 8. PERFORM MATERIAL ANALYSIS 8. PERFORM MATERIAL ANALYSIS 3. DEFINE POTENTIAL RELIABILITY FAILURE MECHANISMS 3. DEFINE POTENTIAL RELIABILITY FAILURE MECHANISMS 4. DEFINE RELEVANT RELIABILITY MODELS 4. DEFINE RELEVANT RELIABILITY MODELS 5. IDENTIFY ACCELERATING FACTORS 5. IDENTIFY ACCELERATING FACTORS 2. DEFINE QUALITY AND RELIABILITY EXPECTATIONS 2. DEFINE QUALITY AND RELIABILITY EXPECTATIONS 1. DEFINE WORST CASE USE ENVIRONMENT 1. DEFINE WORST CASE USE ENVIRONMENT 9. PERFORM PKG / PROCESS SIMULATIONS 9. PERFORM PKG / PROCESS SIMULATIONS 10. ALR / WLR TEST CHARACTERIZATION 10. ALR / WLR TEST CHARACTERIZATION 11. FINALIZE POR (Process of Record) 11. FINALIZE POR (Process of Record) 6. DEFINE STRESS LIMITATIONS 6. DEFINE STRESS LIMITATIONS 7. PERFORM CONSTRUCTION ANALYSIS 7. PERFORM CONSTRUCTION ANALYSIS Temp, RH, # On/Off Cycles Max. ppm allowable, product lifetime, cumulative ppm Corrosion, electromigration, intermetallic growth Arrhenius, Eyring, Coffin-Manson Temperature, voltage, current density, RH Max. temperature, max. current density Demonstrated mfg. construction quality, compliance to design rules Dry vs. wet Tg, CTE1, CTE2, Youngs Modulus Thermal, electrical, mechanical, Gate Oxide QBD, Hot E Gm degradation, bond shear, DEA Built-In Reliability Approach Failure Mechanism Driven Reliability Characterization Methodology

4 4 Coffin Manson Reliability Model * Note: enter data inputs into appropriate grey shaded fields

5 5 Agenda What is Wafer Level Reliability (WLR)? Advantages over traditional Reliability Design for Reliability Develop for Reliability Manufacture for Reliability

6 WLR Definition and Advantages Reliability: The probability that a component will perform a specific function under specific conditions for a specific period of time. Wafer Level Reliability uses mechanismspecific test structures under accelerated conditions to assess the reliability impacts of process and tool changes Advantages over Conventional Reliability Can be done at wafer leveldoesnt need packaging Accelerated conditions (i.e. voltage, current, temp) speeds-up testing Specific failure mechanisms can be analyzed individually Results are process based and can be applied to multiple products Reduced time to market for new products 6

7 7 Examples of WLR Applications HC Degradation : Splits: 3 spacers and 5 LDD dose splits15 splits; each split needs 2 or 3 weeks HCS in PL; total: 20 weeks or more; new technology ~ 9 months to a year! Need WLR!!! Compare the degradation rate between PLR and WLR. Each split just needs one hour stress, total 15 hours Payoff: 15 hours vs hours; WLR: 200 times FAST

8 Reliability Objectives Allow more aggressive performance without increased failure rate Eliminate reliability concerns prior to qualification Meet customers demands and expectations How long should product last (i.e. 2 years to 20 years) Expected failures in time (i.e.1 FIT =1 failure in 10^9 power on hrs.) 8

9 9 WLR Applications Infant Mortality: Device failures due to built-in defects. WLR stress can help to determine the root cause. The WLR stress: such as PIC, Dielectric BV, Qbd test Wearout Failures: The failure rate is increasing. The failures are caused by mechanisms such as electromigration, time dependent dielectric breakdown, and hot carrier degradation.

10 10 WLR Correlation If there is no statistical difference in the performance of subsequent product---subsequent product will have the same reliability as the qualification product. Otherwise the subsequent lot is anomalous material needing further engineering study. Build up the correlation between WLR and PLR. Effects of assembly and packaging The figure for EM of 12-inch and 8- inch wafers from a supplier.

11 WLR Objectives Design for Reliability Develop tools for and consult with Designers to maximize performance of new products without impacting reliability Develop for Reliability Use mechanism-specific test structures under accelerated conditions to eliminate reliability concerns prior to qualification Manufacture for Reliability Use the same test structures to make tool and process improvements and act as a line monitor 11

12 Design for Reliability 12

13 Design for Reliability Provide the reliability data to designer through the reliability calculator. Hot Carrier, Mobile ion, TDDB, EM Updated on an ongoing basis Assess reliability risk for new designs and update the reliability design rules: Design needs to increase operating voltage in gate oxide, current density in metal, and operating voltage on caps (such as HV poly sink caps). How to screen out the defect for gate oxide extrinsic failure. Consulting available upon request Develop AC hot carrier stress Methodology Confirm Berkeley Model for HC degradation in AC application. 13

14 Develop for Reliability 14

15 15 Gate Oxide Integrity

16 16 GOI Test Methodology JRAMP J-Ramp test searches for the breakdown voltage (Vbd) and then calculates the breakdown charge (Qbd) of thin oxide capacitors. JRAMP Test Sequence Makes timing measurements of all procedures used during the ramp Checks the integrity of the structure to be stressed (leakage current test at use voltage) Logarithmically ramps current (5 pS ramp rate) Records current, voltage, and time at each step/interval Terminates the test when - Voltage compliance is reached - Max Qbd is reached - Next current step (if allowed) exceeds max current density - Elapsed time exceeds pre-set max test time - Percentage decrease in measured voltage from previously measured voltage exceeds specified ratio. Calculates outputs/results

17 17 Plasma Induced Charging (PIC) or Antenna

18 18 Antenna Test Methodology VRAMP V-Ramp test searches for the breakdown voltage (Vbd) and then calculates the breakdown charge (Qbd) of thin oxide capacitors. VRAMP Test Sequence Makes timing measurements of all procedures used during the ramp Checks the integrity of the structure to be stressed (leakage current test at use voltage) Linearly ramps the voltage (5 pS ramp rate) Records voltage, current, and time at each step/interval Terminates the test when - Measured current exceeds breakdown current - Max Qbd is reached - Next current step (if allowed) exceeds max current density - Elapsed time exceeds pre-set max test time - Shift in slope of the resultant I/V curve is excessive or slope goes negative Calculates outputs/results Linear Voltage Ramp

19 19 Mobile Ionics

20 20 Test Methodology Effect of Mobile Ion under an Applied Field Test Sequence 1. Initial threshold voltage is measured. Vt#1 2. Stress #1: NMOS a negative bias is applied. PMOS a positive bias is applied. 3. Vt#2 is measured. 4. Delta Vt between Vt#1 and Vt#2 5. Stress #2: NMOS a positive bias is applied. PMOS a negative bias is applied. 6. Final threshold voltage is measured. Vt#3 7. Delta Vt between Vt#2 and Vt#3. Test Method & Conditions Poly heater 250C Bias gate to ±100v

21 Manufacture for Reliability 21

22 Manufacture for Reliability is the application of WLR for monitoring and process changes. Process Qualification (PQPs) FMDRC (identify reliability concerns, possibly new structures or test methods) Define WLR & PLR (Wear-out) test plans to complete Stage IV (Qualification) Execute testing, analyze and publish results Define & execute test plan and publish results at Stage VI (Line Warming) Process Change Support (Change Review Board) Define failure mechanism risks and WLR test plan, analyze and publish results Examples: Gate pre-clean (SP-RCA0) and DUV Qualification Plan Production Monitor Minimum one lot per week sampling across key technologies Monthly presentation of yield compliance for critical parameters by technology and drive W3 improvement plans; initiated 2011 P01 22 Manufacture for Reliability 22


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