Wafer lapping

Lapping(multlple wafer) medium good first poor... 

Wafers are wax mounted to the lapper using a hot plate, and are lapped on a machine exerting a set rotational speed and pressure. A lapping solution is fed onto the lapping surface and constitutes a slurry of aluminum oxide, glycerin and water. After a brief lapping period, the wafers are dismounted on a hot plate, rinsed in a soap solution and wiped dry. 

Backlapplng is done to remove deposited materials from the backside of the wafer. The wafers are wax mounted to a lapper plate and wet lapped with a colloidal silica slurry. 

The roughness of the finished surface is Rz 2-4 pm. Surfaces treated by lapping and microabrasion are similar. In contrast to what happens to photostructured glass, only the areas without a mask are processed the covered parts of the wafer surface remain virtually intact. Figure 2.20 shows various examples of one-sided and doublesided structuring. 

Fig. 65. Raman maps of the surface of a lapped Si wafer [275]. (a) Optical micrograph, (b) The ratio of transformed Si (amorphous material and metastable phases) to pristine Si-I. (c) The same, after the wafer surface was chemically etched. Here, all of the transformed phases are removed. Brighter areas in (b) and (c) correspond to higher content of transformed material.

The use of bulk p)Toelectiics in pyroelectric devices inevitably leads to a situation where the material must be cut, lapped, and polished to make a thin, thermally sensitive layer. If an array of detectors is required for a thermal goal, this must be metallized on both faces, processed photolithographically, and bonded to a silicon read-out circuit to yield a complete hybrid array. Clearly, it would be desirable if the material could be deposited as a thin film, to remove the requirement for lapping and polishing, if possible directly onto a complete wafer of chips, where it could be processed to yield an array of thin. 

FIGURE 2 Fabrication of heads for HDDs, (a) Thin film inductive and GMR heads are batch fabricated on ceramic wafers, (b) Wafers are sliced into rows. At the row level, the air bearing surface is first lapped to tight flatness specifications, and then lithographically patterned and etched to create air bearing features. Air bearing features are typically 0.1-2 om in height, (c) Finally, rows are parted into individual sliders 1 x 1.25 x 0.3 mm in size. SOURCE IBM. 

Figure 1.4 shows the surface profiles of multilayer LTCC substrates imder different conditions as-fired, lapped, and polished, and in contrast to a Si wafer. 

Surface profiles of LTCC substrates (a) as-fired, (b) lapped, (c) polished, and (d) in contrast to a Si wafer. AH vertical scales are in angstroms. 

---