Dark Field Technologies In-Situ Defect Detection Practical Considerations and Results

Transcription

1 Dark Field Technologies In-Situ Defect Detection Practical Considerations and Results June 21, 2017

2 In-Situ Defect Detection The need for In-Situ Defect Detection Solid State Laser Reflection Practical considerations Application results

3 In-Situ Defect Detection - The Problem Vacuum deposition operations are very high value-added; the product must be defect-free. Defect/Particle detection to 1µm is required. Deposition takes place inside a vacuum chamber. Conventional inspection solutions cannot be utilized inside a vacuum chamber due to vacuum, space constraints, alignment challenges, maintenance, etc.

4 In-Situ Detection - continued Operators are blind. Manual inspection is impossible: Small defect sizes. Limited viewing access. Only severe quality excursions MAY be caught. During process upsets, the deposition process continues in free fall until a quality alert is sounded or the roll has been completed. Defects may only be detected after the roll or campaign has been completed.

5 In-Situ Detection - continued The quality of the film produced is suspect. Extensive manual quality audits may be required to avoid shipping rejectable material. This additional handling (film unwind, inspect, rewind) adds costs and defects. Quality-critical operations required a solution. A new Solid State Laser Reflection (SSLR) was developed.

6 In-Situ Defect Detection The need for In-Situ Defect Detection Solid State Laser Reflection (SSLR) Practical considerations Application results

7 SSLR - How it works SSLR Scanner Defect Outgoing Beam Laser Reflector SSLR Scanner Defect Return Beam Laser Reflector

8 Why a Laser Reflector is not a Mirror Incident Beam Mirrors Reflected Beam SSLR Laser Reflector Incident Beam θ θ Mirror Mirrors reflect light at an EQUAL angle. Laser Reflector SSLR Laser Reflector reflects the light BACK ALONG the PATH OF INCIDENCE. Laser reflector is composed of small glass spheres

9 SSLR in Reflection- How it works Generate and capture the light in the same module. Sheet or Web SSLR Production worthy, self-aligning

10 In-Situ Defect Detection The need for In-Situ Defect Detection Solid State Laser Reflection (SSLR) Practical considerations Application results

11 Practical Considerations, In-Situ Inspection Four Daunting Problems Active modules must be OUTSIDE the chamber. 1. Standoff distance must be practical 2. Optical path: High resolution means that every element in the optical path is critical. Transforming a SSLR scanner into a microscope. 3. Working depth of field consistent with the application including film/glass bounce and thickness variations. 4. System must be self-aligning. Constant tuning is not acceptable.

12 1. Standoff Distance 1.5μm SSLR Transmission Configuration

13 1. Stand Off Distance 1.5µm SSLR SIDE VIEW Stand off distance increases significantly as resolution becomes coarser: 3μm resolution = 130mm 5μm resolution = 180mm Film or Sheet Laser Reflector Chamber Window Vacuum Chamber 95mm for 1.5μm resolution

14 2. Optical Path Quality, Chamber Window Chamber windows are poor optical quality relative to the needs of high-resolution scanning. Window Critical window requirements 1.5μm SSLR Transmitted wavefront error at 632nm = 1/10 wave (when mounted and vacuum pulled). Minimum deformation. High efficiency broadband Anti-Reflection coating, both sides, peaked at 400nm to 700nm region at normal angle of incidence.

15 3. Transforming a SSLR into a microscope Working depth of field Depth of field: As system resolution becomes tighter, optical depth of field is reduced dramatically. Film or glass presentation: The sum of thickness variations and flutter/bounce (z-axis variation) must be minimized.

16 3. Defect Detection and Depth of Field How important is depth of field to detection? What happens if depth of field is violated? 1 DOF 2 DOF 3 DOF Array of coating voids 1 DOF 2 DOF Glass Sheet 3 DOF Depth of field 1.5μm SSLR ±35μm. 1.5μm SSLR Good detection at least 3 DOF away from film plane = ±105μm 3μm SSLR = ±100μm. Allowable z-axis range ±300μm 5μm SSLR = ±220μm. Allowable z-axis range

17 Four Daunting Problems, Four Solutions Practical Standoff distance Optical path solution for chamber window Working depth of field consistent with the application including film/glass bounce and thickness variations. SSLR is self-aligning

18 High-Resolution In-Situ Defect Detection The need for In-Situ Defect Detection Solid State Laser Reflection (SSLR) Practical considerations Application results

19 Coated Film, Particle Detection 5μm PSL Spheres Raw SSLR Image Thresholded Image 5um Spheres 3 pixels Detection Limit = 1.7um

20 Coated Film, Particle Detection 10μm PSL Spheres Raw SSLR Image Thresholded Image 10um Spheres 6 pixels Detection Limit = 1.7um

21 Application Observations SSLR Detection limit = resolution. Defect detection limit defines system resolution. System resolution determines Standoff distance Optical path constraints Working depth of field (flutter, bounce) System Resolution = Defect Detection Limit Standoff Distance Working Depth Of Field 1.5μm 95mm ±105μm 3μm 130mm ±300μm 5μm 180mm ±660μm

22 In-Situ Defect Detection - Summary High-value vacuum deposition operations need a robust, high-resolution, in-situ inspection solution. Conventional camera/vision/aoi systems do not meet these in-situ requirements. SSLR technology solves the problems associated with conventional inspection systems and Delivers 1.5μm defect detection at achievable standoff distances. Practical installation and optical path considerations. Is tolerant of film movement outside the depth of field. Active modules installed outside the vacuum chamber. Self aligning.

23 Visit us at booth #2008 Thank You! Grand Prize Winner New Technology