Subsurface damage in single-crystal silicon due to grinding and polishing

Abstract

Grinding and polishing are widely used surface finish operations for a variety of precision and delicate component of ceramics, such as silicon wafers and gauges. However, the formation and evaluation of the subsurface damage induced have not been investigated, although subsurface damage is extremely important to the quality of the products. Grinding and polishing are usually carried out by a series of steps, beginning with rough grinding with coarse abrasives, followed by fine grinding with fine abrasives and then finished by a final polishing with ultra-fine abrasives. Unfortunately, it is still the manufacturing practice that the thickness of material removal at every step is determined empirically according to a rough examination of the ground/ polished surface. This examination method is not reliable, as has been pointed out recently by the authors [1], and the subsurface damage of a component ean be severe even though its surface may look crack-free. The present work is to evaluate the subsurface damage in single-crystal silicon during grinding and polishing. The treated surface had (1 1 0) orientation. Rough grinding was conducted using coarse loose abrasives (silicon carbide) with a mean diameter of 50 pm and followed by grinding using abrasives of 25 #m. Fine grinding was carried out using loose abrasives (aluminium oxide) with mean diameters 15/~m, 9/~m, 5/~m and 1/~m, respectively. Polishing was arranged as a finishing procedure by ultra-fine particles (0.025/~m) using a matrix such as pitch with a suitable oxide slurry. The detailed grinding and polishing proeedure ean be found in [2]. It is important that at each grinding or polishing step, the depth of subsurface damage be determined such that this damaged layer can be removed in the next step. Subsurface damage was evaluated by means of transmission electron microscopy (TEM). To do this, a specimen after each grinding/polishing was sectioned perpendicular to the ground/polished surface to make cross-section view specimens for TEM. Details of the procedure can be found in [1]. This method of specimen preparation enables the subsurface damage to be investigated thoroughly in the plane perpendicular to the ground or polished