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Cleaving Sapphire

Sapphire Cleaving Applications

Cleaving is a simple and fast technique used to prepare samples of silicon and other semiconductor materials, but sapphire, even though it is a single crystal, does not cleave well. Current methods for downsizing sapphire involve sawing and cleaving but yields are unsatisfactory due to fractures in unwanted directions and loss of material during the process. Laser scribing and cryogenic cooling are mentioned in literature as methods that can reduce unwanted fractures, delamination, chipping and loss of material but these methods are costly, time consuming and can present other undesired issues like edge quality and thermal damage due to temperature changes.

As cleaving is fast, low cost with no loss of material, several 3” sapphire wafers were acquired by LatticeGear to revisit cleaving of sapphire using two recently developed methods. These methods are differentiated from handheld scribing and cleaving because they integrate diamond indenting, scribing and cleaving into a mechanical platform. The “smart” mechanics (knobs, levers, dials) enable a repeatable process and remove variation in results based on the operator. It also allows for new test conditions that are not possible with handheld processes. READ MORE

Sapphire wafer downsized with the LatticeAx and FlexScribe
Weak points made by scribers, FlipScribe and LatticeAx
2" Sapphire wafer cleave into quarters
3" sapphire wafer cleaved into quarters

Cleaving explained

Step 1. Weak point creation

The weak point is a defect created on the sample. It will be the initiation point for the cleave. It is not possible to split a substrate into two pieces without first making a weak point using a diamond scriber or indenter. The weak point is made on the edge of the sample (Right) and is very important as it defines the accuracy and quality of the cleave because the cleave propagates from the weak point. If the weak point is made at an angle, is wide, or causes fractures both accuracy and quality of the cleaved surface will be negatively effected.If you need to cleave the sample counter to crystal planes or on amorphous materials you must make a long scribe. These materials will "want" to cleave on crystal planes or the path of least resistance.

Weak points made by scribers, FlipScribe and LatticeAx
Weak points made by scribers, FlipScribe and LatticeAx
Short scribe for crystalline and long scribe for amorphous material
Short scribe used for crystalline materials and long scribe for amorphous or a cleave counter to a crystal plane. The orange lines show the direction of the cleave.

 

Step 2. Cleaving

The second step in preparing a cleaved sample is cleaving. Cleaving occurs by creating stress on the weak point. The cleave is then initiated and propagates across the sample. If the sample is crystalline, the best weak point is short as it initiates a cleave following a crystal plane. The resulting cross section will have a mirror finish (Right). If the sample is amorphous, the sample will break but without a crystal plane, the cleave will propagate in the direction of the weak point but may not be straight unless a long scribe is made scribed across the entire desired line of cleavage. The resulting cross section will not have a mirror finish. This “long scribe” approach is also used on crystalline material when the line of cleavage needs to be counter to the crystal plane. The far right images shows a silicon sample cleaved at 45 degrees to the (100) crystal plane. Note that because the cleave is counter to the crystal plane the edge is rough. Cleaving can be done by splitting the sample in two with fingers, pins, pliers, or indenting and cleaving tool such as the LatticeAx.

Weak points made by scribers, FlipScribe and LatticeAx
Mirror finish facet on crystal plane cleave
Short scribe for crystalline and long scribe for amorphous material
Silicon sample cleaved counter to crystal plane.

Solutions

When cleaving sapphire, since it is hexagonal in crystal structure and very hard, it is very important to understand the orientation of your wafer prior to cleaving. In addition, you need to know whether crystal facets are required and/or downsizing along patterned structures is needed. The cleaving process flow and tools needed will be depend on the desired outcome. So ask yourself?Do I need mirror finish edges (typically needed for photonics devices)?

 The solution may require one or more tools to get the job done. For instance:

Don't see your application here, CONTACT US for a recommendation.

Products for Cleaving Sapphire

Sapphire can be difficult to downsize cleanly and safely. Based on your application LatticeGear can recommend the right tool set. Please contact us!

 

 

Important Accessories

The are a number of accessories that consumables that will be important for your laboratory. 

CleanBreak Pliers with 3 Sets of Jaws. After scribing you will need to cleave your sample. It is possible to cleave over a sharp edge but the pliers provide symmetrical force when cleaving sapphire. Cleanbreak pliers are used for samples 20mm/.75" and larger. For thick 6" sapphire wafers, the FlexScribe and FlipScribe will be your go to tools. Cleave with heavy duty 8" Cleanbreak pliers, for more info ASK US.

Small sample cleaving pliers. For samples <20mm/.75" small sample cleaving pliers are required. They will work well for samples up to 1mm thick. For thicker samples cleave over an edge or with the Small sample cleaver.
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Videos

Watch videos showing the operation of the scribing and cleaving tools and systems.

 

Downsizing samples with the FlexScribe
Operating the LatticeAx 120
Operating the FlipScribe
Downsizing a 2" Sapphire wafer by cleaving

 

Using the small sample cleaver
Cleaving using Cleanbreak pliers
 
Scribing glass on the backside with the FlipScribe
 
Downsizing a thick, 6" sapphire wafer
 

 

Publications

Publications (for copies, contact lg@latticegear.com) or for downloadable copies of these publications you must be registered and signed in

Download
LatticeGear White paper, Cleaving Substrates for Photonics Technologies-New Downsizing methods for Glass and Sapphire
scribers and cleavers

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