Advances in Disk Metrology

Transcription

1 Advances in Disk Metrology Robert Kertayasa Zeta Instruments March Concourse Drive San Jose CA PHONE (408) FAX (408)

2 Agenda Introduction Technology Sample Results Other Applications Summary 2

3 Introduction Challenges in Data Storage Metrology Concourse Drive San Jose CA PHONE (408) FAX (408)

4 Cost of Data Storage is going DOWN! Yeah, we knew that! 10 cents / GB How do we maintain our competitive edge over SSD while keeping up quality and reliability? HDD is still ahead of the game compared to SSD. SSD is not a cost effective solution for the everyday user Courtesy : Frys.Com website SSD drive not available 4

5 Data Storage Trends Fly height was 25nm in 1999 In 2011 it is ~ 2nm Magnetic Spacing is decreasing as the areal density is increasing. Disk roughness 1Å Ra TPI (tracks per inch) is increasing Read write heads are flying lower than ever Higher percentage of the disk is being used to write data with the advent of ramp load / unload Data Zones are being pushed to the very edge of the hard disk surface 5

6 Challenges - Disk Stylus profilers and interferometers have been traditionally used in disk metrology, to measure surface roughness, disk edge roll-off (dub-off) Defect inspection tools have been used to detect defects and bin them out by size New challenges Drive performance at the very edge of the disk is governed in part by the edge chamfer profile there is a urgent need for a chamfer metrology solution Defects detected on the disk are channeled through a time consuming Failure Analysis process, via optical microscope inspection, AFM and SEM. Given the short product life cycles, there is a need to reduce the time to defect resolution 6

7 Challenges Drive FA Modern disk drive have a lot of mission critical components that are beyond the measurement capability of the current metrology toolset Some examples Defects on the HGA Defects on the drive casing Ramp wear Lube pickup on read/write heads There is a need to create a Complete Metrology solution for the drive industry, that will help detect and measure defects that can measure from nanometers to millimeters complementary solution for high resolution instruments such as AFMs and SEMs 7

8 Zeta Technology Chamfer Metrology Solution Concourse Drive San Jose CA PHONE (408) FAX (408)

9 Zeta-CM 3D Imaging and Metrology Microscope for Data Storage Applications 9

10 Disk Chamfer Measurement technique Multiple slices are used to create the 3D view q Can be selected to optimize chamfer imaging q On the Zeta-CM, disks can be tilted for optimal imaging of the chamfer. For example, a disk with a nominal 45 chamfer can be tilted to 45. The chamfer will be in the horizontal plane for optimal 3D measurement. The Zeta-CM then scans the chamfer over a specified vertical range to generate a 3D image. Both OD and ID of the disk can be inspected with this technique. 10

11 350µm Limitations of 2D Microscopy Typical Microscope Image from a µscope without 3D Conventional 2D Microscope cannot image the Chamfer Top view of the chamfer 50X 470µm Side Wall Chamfer Data Zone When viewing the chamfer using a 2D microscope, one has to use a high powered objective. The chamfer goes out of focus as it rolls-off due to depth of focus (DOF) limitation. Engineers typically use 10X objectives for a higher DOF and wider field of view. However, it is not possible to get height or angle information using a small magnification. 11

12 880 µm Side Wall (not visible) Chamfer Data Zone Disk Chamfer Zeta-CM view 2D Microscope view Top view of the chamfer 20X Zeta 3D Image view After scanning the chamfer 1170 µm On the Zeta-CM, a lower magnification can be used to capture a larger portion of the chamfer. In this case a 20X objective has been used. 12

13 Comparison of 3D metrology techniques Attribute AFM STYLUS PROFILER ZETA INTERFEROMETER CONFOCAL MICROSCOPE Large vertical range > 1mm No Yes Yes Yes Yes High Z resolution over the large range ~ sub-µm No Yes Yes Yes Yes Very low reflectivity surface < 1% reflectivity Yes Yes Yes Yes Yes Very high reflectivity surface > 90% reflectivity Yes Yes Yes Yes Yes Very high roughness surface > 100µm Rpv No Yes, BUT! Yes No No Large area imaging - single image > 200µm X 200µm No Yes, BUT! Yes Yes Yes Large area imaging - stitching mm X mm No Yes, BUT! Yes Yes Yes Speed of data acquisition < 1 min per scan No No Yes Yes Yes True color imaging distinguish contaminants No No Yes No Sometimes Cost of ownership LOW! No No Yes No No 13

14 Results Chamfer Metrology Disk Drive Defects Concourse Drive San Jose CA PHONE (408) FAX (408)

15 Chamfer Image Comparison 3 different vendors Vendor A Chamfer Rough with some ridges Side wall Rough Vendor B Chamfer Smooth Side wall Slightly Rough Vendor C Chamfer Very rough with lots of ridges Side wall Smooth 15

16 Curser Pair 1 Curser Pair 2 Disk Chamfer Analysis Marker 2 Marker 3 Marker 4 Markers for feature angle and single point height and width information Marker 1 Two measurement cursors for feature width and step height measurement. The roughness between the two cursors is also reported in a separate log. Chamfer width = µm Marker 1-2 angle = 43.5 Marker 3-4 angle = 6.9 Since the disk was rotated by 45, actual slope of the chamfer is

17 Chamfer Parameter Comparison 3 different vendors Vendor A Vendor B Vendor C Comparison of the multiple cross-sections across the chamfer and side wall allows the users to quantify the chamfer parameters. 17

18 Chamfer roughness and defects 70nm protrusion defect in the chamfer zone Contamination at the edge/chamfer 18

19 Drive & Disk Failure Analysis - Today Current Time To Defect Resolution ~ Hours Disk Defect Inspection - Minutes Optical Microscope Inspection AFM or Stylus Profiler Defect Inspection Minutes Re-scan and Scribe - Minutes Manual process - Minutes Finding correct site minutes Scan Minutes SEM to Hours Sample Prep / Destructive process Minutes Defect Imaging Minutes to Hours 19

20 Drive & Disk Failure Analysis with Zeta Time To Defect Resolution with Zeta ~ Minutes for most defects Disk Defect Inspection - Minutes Defect Inspection Minutes Re-scan and Scribe - Minutes Zeta Metrology Microscope Seconds to Minutes Auto or semiautomated process seconds to minutes Defect Metrology for most defects that are of the order of nanometers to microns AFM or Stylus Profiler (As needed) Minutes to Hours Finding correct site minutes Scan Minutes to Hours SEM (As needed) Minutes to Hours Sample Prep / Destructive process Minutes Defect Imaging Minutes to Hours 20

21 Chamfer Defects: Chip on Glass Substrate. Image taken with regular microscope Zeta-CM image Higher resolution with quantitative height information 21

22 Defect on the side wall of a disk 0.1 micron chip 20um 22

23 Lube Pickup on a Read-Write Head Automated analysis to quantify lube pickup Note : This is an example of a custom application for the data storage industry 23

24 Read-Write Head Analysis Measurement of the dimensions and surface roughness 24

25 Read-Write Head Analysis Full head analysis using the interferometer option 25

26 Summary A new technology for next generation Defect Metrology Concourse Drive San Jose CA PHONE (408) FAX (408)

27 Summary Part 1/2 27

28 Summary Part 2/2 28

29 Zeta Technology Summary 3D Imaging AND Metrology in one compact package Cost effective metrology solution for a broad range of applications Handles very high roughness, very low reflectivity True color imaging Flexible and easy to use software Custom applications developed for customers as required Example : Diamond counts, area, volume on a CMP pad conditioning disk Largest vertical scan capability in its class (from µm to mm) Non-contact, no consumable costs Optional Film thickness, Nomarski and Interferometer make the Zeta-20 a very versatile and powerful metrology and imaging tool 29

30 References Where would be without the Internet? Concourse Drive San Jose CA PHONE (408) FAX (408)

31 References & Courtesy Disk Drive Contamination and Defect Sensitivity Trends Thomas M. Coughlin, Coughlin Associates, Ramp Load/Unload Technology in Hard Disk Drives (White Paper) Patricia Kim & Mike Suk, HGST Western Digital White Paper Fly Height Monitor Improves Hard Drive Reliability

32 BACKUP Concourse Drive San Jose CA PHONE (408) FAX (408)

33 Zeta Technology 1 CCD Color Camera Digital camera to capture sample images and focus map data 2 Zeta Optics Module Focus map signal generator High intensity white light LED to preserve sample color High efficiency optics design to optimize illumination 3 Z-drive Conventional microscopes have a very limited depth of focus. Test surfaces and features are clearly visible ONLY when they are within the focal depth. The Zeta system scans a sample over a user specified vertical (or Z) range. At each Z position, it records the XY location and the precise Z height of the pixels using the Zeta Optics Module. This information is used to create a true color 3D image and a 2D composite image. The resulting image has a extended depth of focus so the entire surface is seen clearly. The Zeta 3D software can be used to ascertain dimensional and roughness information Conventional Microscope (2D Only) Precision mechanism for submicron vertical resolution 4 Zeta Control Box FMM and Z-drive electronics controller 5 XY Stage 4 Zeta Images (2D & 3D) Convenient sample positioning 33

34 Disk Chamfer Parameters Data Zone Chamfer Mean Chamfer Angle Note that the chamfer may have 2 discrete angles in some cases Important Chamfer Parameters Projected Chamfer Width Affects flying characteristics of the read write head at the disk edge. Affects the available data zone closer to the disk edge. Affects disk clamping at the ID and vibration / stability at run time Mean Chamfer Angle Critical for proper handling of the substrate during the disk manufacturing process. Affects the uniformity of the films deposited near the edge. Chamfer Roughness & Finish Improper chamfer finish may leave residue or defects that will affect long term drive reliability 34

35 Zeta Capability Current Measurement Methodology Measurement Current Technique Challenges Chamfer Width Chamfer Angle Measured using optical microscope and dark field illumination. Measured using a Shadow Graph at some substrate manufacturers. Limited field of view. Not automated. Manual process, not very repeatable. Shadow does not define the chamfer accurately. Only large variations in chamfer angle can be captured, finer variations cannot be captured. Chamfer Roughness No method available at present. Measuring the roughness on a surface with a varying slope Chamfer Defects Roll-Off Visual inspection using microscope. Disk inspection tool, Interferometer Very subjective, current methodology does not allow accurate sizing, binning or classification of the defects. Cannot correlate between tools. Cannot get accurate disk center and edge information. Not enough depth of field. 35