SMART Pad for CMP. Sunghoon Lee 1, David A. Dornfeld 1 Hae Do Jeong 2. University of California, Berkeley, USA 2

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1 SMART Pad for CMP Sunghoon Lee 1, David A. Dornfeld 1 Hae Do Jeong 2 1 University of California, Berkeley, USA 2 Pusan National University, Pusan, KOREA

2 Features SMART pad is composed of two stacks of soft and hard portions, with micro-scale structures fabricated by micro molding technology. Hard pad elements polish patterned/metal layers for ILD/metal CMP. Soft pad elements allow for pad compliance for repeatability and topography independence. Potential for sensor integration for in-situ process characterization (ie. end-point detection). Ultrasonic pad cleaning/conditioning reduces pad deterioration.

3 What s SMART pad? No No Thinning, Thinning, Dishing, Dishing, or or Erosion Erosion Signals For End Point Detection Signals from Pad MAintenance easy pad SMART PAD Topography Independence Longer Pad Life WIWNU WTWNU Repeatability

4 CMP pad topography(ic1400 K-Groove) pore, wall and groove Wafer 1.Pore 2.Wall 3.Groove (side view) 300um Pad Abrasives Wafer Pore Wall Pad Topography of pad surface (source : Rodel (Zygo profile)) New pad (open pores/smooth wall) After Stabilization (open pores/rough wall) After CMP (glazed pores/smooth wall) After Conditioning (open pores/rough wall)

5 Schematic of SMART pad 150um Top View 50um(space) Groove & Pore Hard Material (i.e. high stiffness) Wall Side View Soft Material (i.e. low stiffness) Protrusion for rough wall

6 Fabrication process of SMART pad for CMP 1. Silicon etching 3. Silicon removal Soft polymer 5. Soft part molding Si 2. Metal deposition for pad mold 4. Hard part molding Hard polymer 6. SMART pad for CMP Mold for pad Si

7 Signals for end point detection Sensors Field Oxide ILD Si Wafer Initial state Field Oxide ILD Si Wafer End point Non-uniform pressure distribution Uniform pressure distribution

8 MAintenance easy pad Conventional pad maintenance (diamond conditioning) Pressure & movement SLURRY WAFER Pad removal by diamond grits 200~300 um SMART pad maintenance (ultrasonic cleaning) Deformation part(soft) No deformation on pad surface (hard) fluid - No pad surface deformation - Only cleaning pad surface needed -Ultrasonic cleaning

9 Repeatability Field Oxide ILD Si Wafer Deformation part(soft) No deformation on pad surface (hard) Non-deformable pad surface No pad surface deformation Pressure sustained by soft part Constant contact area Longer pad life Conventional Pad Top View Pore, Groove Wall Side View Well defined geometry Space between hard parts acts as new pores in conventional pad Well defined pores in SMART pad Changeable pores width Finer pores than conventional pad No pore glazing

10 Topography independence Chip topography independence by SMART pad No pressure concentration in high pattern density area Field Oxide ILD Si Wafer Even pressure distribution Constant pressure maintenance by hard pad surface No deformation No deformation stop Line stop Line

11 Conclusions A new pad design with micro structures is suggested. End point detection in CMP is possible through sensor integration. Ultrasonic cleaning provides more efficient cleaning than conventional techniques. Well defined pad surface is effective for uniformity. Combination of hard/soft pad elements with microscale features reduce traditional CMP defects (dishing, erosion, etc ).