Study of the Brittle Fracture of Monocrystalline Silicon Wafers

Abstract

There is a growing trend towards using thinner wafers in order to reduce the costs of solar energy. But the current tools employed during the solar cells production are not prepared to work with thinner wafers, decreasing the industrial yield due to the high number of wafers broken. To develop new tools, or modify existing ones, the mechanical properties have to be determined. This paper tackles an experimental study of the mechanical properties of wafers. First, the material characteristics are detailed and the process to obtain wafers is presented. Then, the complete test setup and the mechanical strength results interpreted by a described numerical model are shown.

Estudio de las propiedades mecánicas de obleas de silicio

“…Con el n de comprobar la inuencia de la estructura cristalina en la resistencia ( [5], [7]), se prepararon tres grupos con diferente orientación (Figura Figura 2.16: Fotografía de la supercie texturizada de una oblea monocristalina 2.17). Para ello se partió de tres lingotes crecidos según la dirección 100 y se recticaron dejando los planos {110} a 45 • de los bordes (como las comerciales) a 22,5 • y a 0 • .…”

Comparison of Different Finite Element Models for the Simulation of the Ring-Ball on Ring Test

“…Moreover, the wire cutting process may origin cracks on the wafer's surfaces. Therefore, the mechanical strength of silicon wafers depends on the cracks population residing in them ( [4], [5], [6]). …”

“…This test loads the zone between the lower supports so both types of cracks are stressed. Therefore, results are taking into account cracks in the central zone of the wafer generated by the wire sawing process as well as cracks near the edges generated by the cutting process to make pseudo square cross section wafers ( [6], [9]). This type of test has been employed by the authors in previous studies ( [4], [6]) but it's not concerning to the results that are presented in this paper.…”

“…These studies are usually carried out by means of tests and the development of numerical models simulating them [9]. In previous studies, the authors employed the four line bending test ([4], [6]). Another type of test has been used in recent studies.…”

“…Strength characterization becomes necessary in order to optimize the steps in the production process. Many studies concerning the mechanical properties of silicon wafers have been carried out last years ( [4], [6], [9], [11]). These studies are usually carried out by means of tests and the development of numerical models simulating them [9].…”