Silicon Wafer Coring (Resizing)

A Laserod speciality is coring (resizing), dicing and scribing of silicon wafers, substrates, and laser machining silicon devices such as sensors, detectors, and solar cells

 

Laserod laser cores or resizes silicon wafers by downsizing large semiconductor wafers to smaller ones. Laserod also laser machines silicon sensors, solar cells, MEMS and other photovoltaic devices as shown below. We also do silicon wafer dicing by laser scribing, which is a two step scribe and break process to convert a wafer into dice, aka “chips”.

 

For information on laser hole drilling in silicon – go HERE.

 

Our standard kerf loss in coring, dicing or cutting is 30 microns. 10um is available on special order.

 

Laserod’s Wafer Processing Services Include:

 

Standard Wafer Coring Services:

 

  • Typically silicon, other materials are acceptable.
  • Resizing, coring, downsizing from 300mm max diameter to any smaller size and any wafer thickness up to 2mm.
  • Cut flats or notches
  • Tolerance on notches or flats is +/- 0.025mm
  • Gringing, typically a rounded edge or bevel
  • Video registration through the laser focusing lens, giving a magnified view of the worksite.  Laserod can register/align to circuitry, fiducial marks or on streets and avenues such as for dicing (see below).

 

Other Silicon Wafer Services include: 

 

  • Laser marking an ID on laser resized wafers
  • Polishing
  • Thinning by grinding/polishing
  • Hole drilling
  • Laser dicing or singulating
  • Topside or bottom side laser cutting, dicing, singulating or scribing
  • Anti-static mats
  • Wrist straps for ESD prevention
  • ESD dicing film
Laserod minimizes contaminants using a vacuum collection device. However, this is primarily used in laser scribing, not cutting. Laser debris on top of the wafer, especially after cutting, can be further minimized by use of a protective layer of photoresist which is then cleaned off by our customer.
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Silicon Wafer Coring

Silicon Wafer Coring (Resizing) by Laser Cutting

A commonly performed job is resizing 12″ to 8″ as shown here. Other common downsizings include: 8″ to 6″; 6″ to 4″; 12″, 8″, 6″ or 4″ down to multiple 2″ wafers. Practically any kind of downsizing (coring) by laser cutting is possible.

 

 

 

 

If you are interested in buying a laser coring machine, go  HERE  (and scroll down to third picture, LPS-300 System)

 

 

Large hole laser trepanned in silicon wafer.

 

Very Large Trepanned “Hole” or small resized wafer, whichever you want

Circular cuts in silicon wafers.
3mm (.125″) dia. Thickness is 175mm (.007″).

 

 

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Micromachining Drilled Holes

 

Array of Laser Drilled Percussion Holes in a Silicon Substrate

in 625um thickness Si

Overall 12mm dia

Small hole dia 0.125mm (125um)

 

 

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Silicon Drilling Example

 

Profile of Laser Trepanned Hole Drilled in Silicon

0.700mm dia.
Laser entrance side, cleaned mechanically. Thickness is 0.5mm (.020″).

 

Get More Info…

 Get More on Laser Hole Drilling

 

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Two Laser Drilled Holes In Silicon

 

Trepanned Silicon Hole Drilling and Laser Scribing

0.125mm (.005″) dia. holes

Debris is from a Styrofoam cup used to gently but effectively clean off laser debris – a nice mechanical cleaning trick. Thickness 0.5mm. Note the laser scribes at lower left – for Silicon Wafer Dicing

 

 

 

 

Silicon Wafer Cutting Sample

 

 

Laser Cutting a Silicon Edge at an Angle

Fancy laser cutting at a 45 degree angle.

 

 

 

 

 

 

 

 

Guidelines for Silicon Processing by Q-switched YAG Laser

 

These first three pertain to holes, cuts or scribes:

 

  • Max Depth: 2 mm
  • Min Depth: none
  • Typical Depth of Penetration: 0.5mm
  • Max Wafer Size:  300mm

 

These next six pertain to drilling holes only:

 

  • Max Dia of Trepanned Hole: none
  • Min Dia of Trepanned Hole: 50 microns
  • Max Dia of Percussion Hole: 50 microns (up to 25 mil thickness Si)
  • Min Dia of Percussion Hole: 15 microns
  • Taper of Trepanned Hole: (ask us)
  • Taper of Percussion Hole: (ask us)

 

The next two pertain to cutting or scribing.

 

  • Kerf Loss: Width of cut for 0.5 mm thick Si (full penetration cut) is 50 microns at top and 25 microns at bottom of cut.
  • Edge taper is best evaluated on samples we create for you.

 

These last two pertain to all: drilling, cutting and scribing.

Laser Debris: entrance side only, none on laser exit side. Debris field is an easily removable haze. If desired, remove with Q-tip, Styrofoam,fi DI water, ultrasonic cleaning, etc. For MEMS devices  special techniques are used.

 

Laser processing of silicon naturallly creates a hazy residue of redeposited silicon particles, again on only one side.

 

There are two basic methods of working silicon without contamination (others for MEMS):

 

Method #1: Back side drilling, cutting and scribing of silicon

Backside work requires registration to the front side which is achieved by the use of custom optical registration providing precise location.

 

Method #2: Front side drilling, cutting and scribing of silicon

Registration is through the laser focusing lens, allowing us to see with the same magnification as the laser sees. Fiducials work great for alignment. We align to +/- 5 to 10 microns typically. We can increase the laser magnification and improve this, if required.

 

Contamination control techniques include the use of photoresist or equivalent coatings. There are no post laser marks left on the silicon after cleaning off the coating. The coating must be removed, posing a problem for some devices.

 

Other contamination controls are the use of low power laser processing to minimize particulates and the use of vacuum exhaust. We can process parts in a full clean room.

 

Five Applications of Laser Machining in Silicon

 

Application # 1: Wafer Scribing for Subsequent Dicing (Singulation)

Wafer scribing for “scribe and break” is typically to a depth of up to 80% of the wafer thickness. The deeper the scribe, the easier the break. Avoidance of complete penetration (cutting, not scribing) keeps the die in place and prevents scattering due to shock waves created by laser vaporization. Of course, deeper scribes take more time, thus reducing throughput. There are yet more variables. We would enjoy discussing them with you.

 

For an informative 30 second  magnified video of laser scribing of silicon wafers, view this Scribing-1.

 

Application # 2: Via Drilling

Allows front to back surface contacts. Small percussion holes and trepanned larger diameter holes are both done.

 

Application # 3: MEMS  (Click to go to a MEMS webpage.)

Micro-electromechanical systems devices (MEMS) are laser machined to provide channels, pockets and through features (holes) with laser spot sizes down to 10um and positioning resolution of 2-5um. Channels and pockets allow the device to flex. Our backside processing techniques are particularly applicable.

 

Application # 4: Wafer Flats

Additional Wafer Flats to aid downstream wafer processing. By adding another flat to the wafer, it is possible to handle the wafer with greater ease during the production process.

 

Application # 5: Metal Contact Isolation

Involves laser cutting for electrical isolation. Depths of the cuts can be to 5-6 mils and widths down to 0.5 mil.

 

Whatever your requirements for silicon processing are, Laserod personnel are pleased to discuss it with you. Please call, e-mail or fax.