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Monocrystalline silicon is currently one of the most used materials in the semiconductor industry. However, being hard and brittle, a silicon wafer commonly suffers from machining-induced subsurface damage (SSD). Detecting SSD is important for optimizing the machining process in order to improve the surface integrity of a machined wafer. Among the various detection methods, the polarized laser scattering (PLS) method has a huge potential in highly efficient detection. However, the surface scattering mechanism is not fully understood so far, which impedes the optimization of the PLS detection processes. This study resolves surface scattering based on the electromagnetic scattering theory. It is found that the depolarization caused by surface scattering increases with the surface roughness and the incident angle. With the consideration of the subsurface scattering characteristics and the distribution of the SSD, this study provides a solution for the PLS detection that comprises of the use of a horizontally polarized laser with vertical incidence to minimize the influence of surface scattering. This study provides a theoretical analysis of both surface and subsurface scattering to facilitate an optimized PLS detection. [Display omitted] • A laser scattering model is built based on the electromagnetic scattering theory. • The depolarization of surface scattering in the PLS detection is resolved. • A solution to minimizing the surface roughness effect in PLS detection is proposed. • The influence of surface roughness and SSD depth are experimentally verified. • The solution is experimentally demonstrated effective to detect SSD. [ABSTRACT FROM AUTHOR]

• A new nondestructive method for detecting the damage in CMC is proposed. • The feasibility of the polarized laser scattering detection is demonstrated. • The sensitivity of PLS detection is dependent on the laser radiation spot size. • Small laser radiation spot size enlarges the influence of the pre-existed defects. Given the urgent demand in the effective method for detecting the machining-induced damage (MID) of ceramic matrix composite (CMC). This study first time proposes the polarized laser scattering (PLS) method to detect the grinding-induced damage of silicon carbide fiber reinforced silicon carbide (SiC f /SiC). The feasibility of the PLS detection is demonstrated. Moreover, the sensitivity of PLS detection is found dependent on the radiation spot size of the laser beam. Decreasing the radiation spot size, the sensitivity to MID increases. However, the sensitivity to the pre-existed defects also increases, which would disturb the detection of MID. While increasing the radiation spot size, the intensity of the PLS detection decreases. In this study, when the radiation spot size is 66, 132, or 264 μm, the PLS method is suitable for detecting the grinding-induced damage of SiC f /SiC. This study is important for expanding the detection of the MID of CMC. [ABSTRACT FROM AUTHOR]

Silicon is the primary substrate material in the semiconductor industry. Since surface integrity of a silicon wafer is crucial to the performance of an IC chip made of the wafer, the subsurface damage (SSD) induced by machining to a silicon wafer has been intensively investigated. However, detecting SSD is a challenge due to a lack of an effective method. This study presents a novel method, the polarized laser scattering (PLS) method, for detecting SSD in ground silicon wafers. A PLS system is established to detect the grinding-induced SSD which is also evaluated by the destructive methods. The study shows that the PLS signal is sensitive to the SSD depth with a detection resolution of approximately 0.1 μm. In addition, the detectability of the PLS method is demonstrated and a relationship between the PLS signal and SSD depth is established to facilitate the practical applications of the PLS method. • The sensitivity of the PLS detection to SSD in ground wafers is revealed. • The minimum detected SSD depth by the PLS detection is 0.1 μm. • The PLS detection signal monotonically increases with SSD depth. • The relationship between the PLS signal and the SSD depth is built. [ABSTRACT FROM AUTHOR]

• Polarized laser scattering can detect subsurface cracks without the influence of residual stress and surface roughness. • A polarized laser scattering signal is affected by both the depth and density of the subsurface cracks in a ground wafer. • The depth of subsurface cracks is more dominant than crack density in the detection by using the polarized laser scattering. This study proposes a polarized laser scattering (PLS) method for detection of the two-dimensional distribution of the grinding-induced subsurface damage (SSD). This study also uses two destructive methods to observe the distribution of SSD in the ground silicon wafers by cross-sectional microscopy and by layer-by-layer microscopy. An experimental investigation is arranged for detecting the two-dimensional damage from diamond wheel grinding of silicon wafers through wafer sample preparation and SSD observations with the cross-sectional and layer-by-layer microcopy. It also includes PLS detection of the ground silicon wafers for SSD information. The results show that both the depth of SSD and the crack density contribute to the PLS detection signals. The study reveals the characteristics of the PLS detection, which illustrates the potential application of the PLS method to in-process detection. [ABSTRACT FROM AUTHOR]