SAMSUNG Advanced Institute of Technology 2nd Asian IM User Group Meeting in Japan SAMSUNG

SAMSUNG Advanced Institute of Technology T his TRIZ application case was done by researchers of SAIT(Samsung Advanced Institute of Technology), not by TRIZ specialist, although there was help from TRIZ specialist. They had 40 hours TRIZ lesson at company, so they just knew the concept of Contradiction and could use Techoptimizer A s in #9 slide, as soon as they encountered problem, they recognized it as physical contradiction. But with that contradiction expression they could not adopt 4 principles of solving physical contradiction. At that time, TRIZ specialist helped them and converted physical contradiction in another expression : TRIZ specialist thought earlier expression was the result of mental inertial of professional of specific area which had deep relationship with process of manufacturing, dry etching process. As soon as converting physical contradiction, they could solve it by "Separation by Space Principles". A s in #15, 16, the typical process of solving problem could be shown. In generally, although they could solve one problem, frequently, another problem occur after solving one problem. As in this presentation, researchers regarded it as Technical Contradiction. So they used Contradiction Table in Techoptimizer. In this case, they could find exactly the same example of principle named "self-aligned process". Besides solving current loss problem by uniform shape of p-metal, they could additionally remove the most critical and difficult process, so they achieved quantum increase in yield. In this case, some guy could say they are too lucky. But it is the more difficult to deny the powerfulness of contradiction table and Principle module of Techoptimizer. I n summary, from the first case, SAIT TRIZ specialist (Hyo June Kim, Nikolai Shpakovsky) learned the importance of expression of Contradiction and role of mental inertia at expression. From the second case, also learned how to formulate the technical contradiction from typical problem solving process. Short Summary

SAMSUNG Advanced Institute of Technology GaN Laser Diode 6  Process for GaN Laser Diode   Process Mapping - Selecting Essential steps for CTQ   Ridge shape change by TRIZ   p-metal process Improvement by TRIZ   Oxidation Process optimization by DOE   Strategy - Reducing Ith by Ridge shape change - Reducing variance of Ith by p-metal process improvement and optimization of oxide process   Project definition - Technology Roadmap - Voice of customer   CTQ selecting - Threshold Current (Ith) - Variance of Ith   Property evaluation   Verification of variance of Ith Measure Define Analyze Design Verify - Reducing Ith  Ridge shape change  TRIZ - Reducing variance of Ith  p-metal process improvement  TRIZ - Reducing variance of Ith  optimization of oxide process  DOE

SAMSUNG Advanced Institute of Technology Before TRIZ in 6 sigma D D A V M 40 mA, 6V 200mA, 6.7V

SAMSUNG Advanced Institute of Technology Project Definition Problem Statement - Life time of GaN Laser Diode present : 1.7 hr (at CW 1mW, 20 o C) - Threshold Current (Ith) present : 200 mA variance of Ith : 105 mA Objectives - Life time of GaN Laser Diode > 1000 hr - Reducing of Ith : Ith >200 mA → Ith ≤ 50 mA - Improvement of Ith variance :  (Ith) = 105 mA →  (Ith)≤ 10 mA CTQ Selection D D A V M Operating Current: 140mA Life time: 1.7 hr Time (min) Current (mA)

SAMSUNG Advanced Institute of Technology Process Mapping Fabrication Process Critical step for CTQ Ith Critical step for CTQ variance of Ith Critical step for CTQ variance of Ith D D A V M

SAMSUNG Advanced Institute of Technology Preparing strategy Strategy for each critical process step Ith dry etching for ridge formation - present : 0.2  m etching depth from active layer Variance of Ith p-metal layer deposition - present : formation of 1.5  m width p-metal on the 2  m ridge passivation layer deposition - present : BOE time < 40 sec TRIZ TRIZ DOE DD A V M

SAMSUNG Advanced Institute of Technology D DA V M Dry Etching for Ridge Formation:TRIZ Initial situation n Device Fabrication w Ridge wave guide etching w Facet Etching w Passivation layer deposition w Formation of n-electrode w Formation of p-electrode w Bonding metal & mirror coating n Ridge wave guide part : Critical effect to electric property of LD. Especially depending on depth of ridge. (0001)Sapphire Substrate n-GaN /n-Al 0.14 Ga 0.86 N n-GaN p-Al 0.2 Ga 0.8 N InGaN/ MQW p-GaN /p-Al 0.14 Ga 0.86 N p-electrode n-electrode SiO 2 MD-SLS Cladding layer Ridge wave guide

SAMSUNG Advanced Institute of Technology Problem refinement n Shallow ridge etching depth w Current spreading problem w Threshold current Increase Physical Contradiction : Ridge etching depth must deep and must not deep n Deep ridge etching depth w Optical Loss w Threshold current Increase Sapphire Substrate GaN/n-Al 0.14 Ga 0.86 N n-GaN Sapphire Substrate GaN/n-Al 0.14 Ga 0.86 N n-GaN Optical loss D DA V M Dry Etching for Ridge Formation:TRIZ

SAMSUNG Advanced Institute of Technology D DA V M Solution of Contradiction Dry Etching for Ridge Formation:TRIZ Physical Contradiction : Ridge etching depth must deep and must not deep Separation by Time Separation by Space … Must Deep Must Not Deep

SAMSUNG Advanced Institute of Technology D DA V M Solution of Contradiction Dry Etching for Ridge Formation:TRIZ Physical Contradiction : Ridge etching depth must deep and must not deep Physical Contradiction : Ridge etching depth must wide and must not wide Must Wide Must Not Wide

SAMSUNG Advanced Institute of Technology D DA V M Dry Etching for Ridge Formation:TRIZ Solution of Contradiction Physical Contradiction : Ridge etching depth must wide and must not wide Principle of Separation by Space Upper part : narrow ridge prevent current spreading Lower part : wide ridge prevent optical loss

SAMSUNG Advanced Institute of Technology D DA V M Solution of Contradiction Dry Etching for Ridge Formation:TRIZ

SAMSUNG Advanced Institute of Technology D DA V M Previous Ridge Ith > 200 mA Improved Ridge Ith < 50 mA Breakthrough ! Result Dry Etching for Ridge Formation:TRIZ

SAMSUNG Advanced Institute of Technology P-metal Layer Deposition : TRIZ D DA V M Initial Situation Old structure of P-metal : Narrow P-metal Demerit : 1. Not enough removal of heat generated in GaN. Critical effect to life time 2. Too narrow P-metal make process difficult

SAMSUNG Advanced Institute of Technology P-metal Layer Deposition : TRIZ D DA V M Initial Situation New structure of P-metal : Wide P-metal Merit : Enough removal of heat generated in GaN. Good effect to life time Another problem appear : Loss of current Typical process of Problem solving.

SAMSUNG Advanced Institute of Technology P-metal Layer Deposition : TRIZ Initial Situation D DA V M (0001)Sapphire Substrate n-GaN /n-Al 0.14 Ga 0.86 N n-GaN p-Al 0.2 Ga 0.8 N InGaN/ MQW p-GaN /p-Al 0.14 Ga 0.86 N p-electrode n-electrode SiO 2 MD-SLS Cladding layer 1.5  m (Contact hole width) 2  m (Ridge Width) n Device Fabrication w Ridge & Mesa Etching w Passivation layer deposition w Formation of n-electrode w Formation of contact hole w Formation of p-electrode w Bonding metal & mirror coating 1 Fine contact hole patterning (1.5  m x 500  m) Too fine 1.5  m width etching unstable process large variance of Ith Loss of current appear 2

SAMSUNG Advanced Institute of Technology D DA V M P-metal Layer Deposition : TRIZ Problem refinement  Length of stationary object  Loss of energy 6. Multifunctionality 28.Mechanical interaction substitution TechnicalContradiction  Improving feature : increase P-metal width.  Worsening feature : current loss at P-metal at outside of ridge

SAMSUNG Advanced Institute of Technology D DA V M P-metal Layer Deposition : TRIZ Solution of Contradiction Ridge Etching with PR/SiO 2 mask Sapphire Substrate GaN/n-Al 0.14 Ga 0.86 N n-GaN SiO 2 PR Reused PR mask (Multifunction) Oxide passivation layer Self-aligned Contact hole Sapphire Substrate GaN/n-Al 0.14 Ga 0.86 N n-GaN Sapphire Substrate GaN/n-Al 0.14 Ga 0.86 N n-GaN Reused SiO2 mask (Multifunction) Oxidation of etching surface 1.5  m width etching, contact hole patterning process was disappeared.

SAMSUNG Advanced Institute of Technology D DA V M P-metal Layer Deposition : TRIZ 않고 Contact hole formation with self-aligned process. Removing of most difficult process. No current loss by uniform shape of p-metal. Solution of Contradiction Saving of process time. Improved reliability of process (yield) Improved reliability of product (variance of Ith)

SAMSUNG Advanced Institute of Technology Passivation Layer Deposition : DOE D DA V M n Needs of DOE n n n n Results of DOE Not enough PECVD condition for SiO2 passivation layer. Optimization need 1st DOE : 2(4) + 2, selecting meaning factor : N2Ogas and Temperature. No corelationship between factors. 2nd DOE : 2(2) rd DOE : 2(2) + 2(2) + center point, another meaning factor No corelationship between factors. 2nd DOE : 2(2) rd DOE : 2(2) + 2(2) + center point, another meaning factor SiH4/N2O ratio. SiH4/N2O ratio. 4th Response Surface Analysis

SAMSUNG Advanced Institute of Technology DDA V M After TRIZ in 6 sigma 산포 105 mA  16 mA Before After 260 mA 42 mA 임계전류 (Ith) Variance of Ith : From 105mA to 16mA

SAMSUNG Advanced Institute of Technology 45 mA, 5V, 5mW 30 mA, 5.8V, 3mW DDA V M After TRIZ in 6 sigma