Learn About Cleaving With LatticeGear
Mirror Finish? On and Off Crystal Plane Cleaving?
What do we mean when we ask, “do you need your cleaved facet to have a mirror finish?” or “do you need to cleave on or off crystal plane?
Here is a quick explanation. I will introduce these concepts using a crystalline (100) silicon substrate as the example.
Silicon (100) has cleave planes at 90 degrees to each other designated  and  (Figure 1A). When you dice a wafer on these planes, a mirror finish is achievable. If you cleave “off crystal plane” (Figure 1B) the cleaved edge will fracture in unwanted directions unless you use a special tool such as the FlipScribe or FlexScribe. To make a sample that is cleaved “off crystal axis” such as that shown in Figure 1B, you will need to scribe across the entire length of the sample (Figure 1C). A perfect mirror finish is only achievable when you make a short indent or scribe and cleave “on crystal plane”. In that case the cleave will propagate from the short indent along the crystal plane producing the mirror finish facet.
Figure 2 shows 2 cleaved facets. On the top, Figure 2A, is a substrate showing a mirror finish. You can see the reflection of the cleaving mat on the cleaved surface or facet. Figure 2B, bottom, shows the same substrate cleaved at 45 degrees to the silicon cleaving planes as drawn in Figure 1B. The top surface shows mirror quality but the bottom has some damage from the scribing process.
Figure 3 is a silicon (100) substrate cleaved “off axis” as described in Figure 1B using the FlipScribe.
You might ask, “Can I cleave off crystal plane with a handheld scriber. This may be possible with a lot of practice and skill but will likely not be repeatable. Using the right tools, such as the FlipScribe or FlexScribe will definitely improve success and repeatability.
FIG 2A (top). Cleave surface/facet shows mirror of the cleaving mat. and FIG 2B (bottom) show the mirror disrupted by the scribe line on the backside of the sample.
FIGURE 3 Silicon (100) cleaved at 46 degrees to the crystal plane (off crystal plane) with the FlipScribe