Cleavage Fracture of Brittle Semiconductors from the Nanometre to the Centimetre Scale

Abstract

The objective of this paper is to present the fundamental phenomena occurring during the scribing and subsequent fracturing process usually performed when preparing surfaces of brittle semiconductors. In the first part, an overview of nano‐scratching experiments of different semiconductor surfaces (InP, Si and GaAs) is given. It is shown how phase transformation can occur in Si under a diamond tip, how single dislocations can be induced in InP wafers and how higher scratching load of GaAs wafer leads to the apparition of a crack network below the surface. A nano‐scratching device, inside a scanning electron microscope (SEM), has been used to observe how spalling (crack and detachment of chips) and/or ductile formation of chips may happen at the semiconductor surface. In the second part cleavage experiments are described. The breaking load of thin GaAs (100) wafers is directly related to the presence of initial sharp cracks induced by scratching. By performing finite element modelling (FEM) of samples under specific loading conditions, it is found that the depth of the median crack below the scratch determines quantitatively the onset of crack propagation. By carefully controlling the position and measuring the force during the cleavage, it is demonstrated that crack propagation through a wafer can be controlled. Besides, the influence of the loading configuration on crack propagation and on the cleaved surface quality is explained.

Analysis of onset of dislocation nucleation during nanoindentation and nanoscratching of InP

“…1 This method has many other potential applications in diverse fields, e.g., investigation of phase transformations, 2,3 thin film delamination, 4 and/or cleavage of materials. 5,6 Thus, indentation mechanics is extensively described in several text books. 7,8 Most scientists agree that, in III-V semiconductors, the nucleation of dislocations, also called the elastic-plastic transition, is associated with the pop-in in the load-displacement curve in nanoindentation.…”

Scratching and Brittle Fracture of Semiconductor In-Situ Scanning Electron Microscope

“…Hence, its material properties will dependence on crystal orientation and the principal characteristics are given in Table 1. The preferential cleavage plane is known to be {110} which is consistent with the lowest K IC value in Table 1 [1,[7][8][9][10][11]. The average fracture strength of GaAs wafers measured from micromechanical cantilever beam structure tests is more or less 2.4 GPa [17].…”

“…It has already been observed that, by and large, 5 different phenomena occur when scratching semi-conductors [1] and glasses [4]. Figure 2, taken from [1], illustrated these 5 regimes.…”

“…It is followed by the elastoplastic regime. In the third region, subsurface cracking takes place which depends strongly on the tip geometry [1]. This includes the formation of lateral and median cracks.…”

“…The goal of the first operation is to create a subsurface crack aligned with a cleavage plane. This crack is required to be able to control the crack initiation and propagation, even in brittle materials such as Gallium-Arsenide (GaAs) so that atomically flat surfaces can be achieved [1]. Unfortunately, scribing semiconductors with a diamond tip does not only induce the defect needed but also some undesirable features such as radial cracks (chevrons) and particles.…”