Surface Roughness

The surface roughness of the silicon wafer is an important factor leading to the decrease in electrical performance. MOSFET affects the mobility of electrons and holes, and this mobility is affected by the thickness of the wafer surface, the size and shape of the edge. Silicon wafers are polished to create a smooth surface when manufacturing semiconductor devices to produce higher yields. Surface roughness is a part of surface texture and is quantified by the deviation of the normal vector direction of the actual surface from its ideal form. If the deviation is large, the surface is rough; if the deviation is small, the surface is smooth. Alfa Chemistry provides customers with accurate wafer surface roughness testing services to meet customers' application requirements. You can rest assured of our test report.

Our Testing Methods

Alfa Chemistry conducts large-area inspections of test samples through atomic force microscopes to obtain high-resolution images and reliable sub-nanometer roughness measurements.

In addition, Alfa Chemistry uses Total Reflection X-ray Fluorescence (TXRF) to characterize the roughness on the wafer surface. The secondary fluorescence signal is obtained after irradiation with the primary X-ray beam. Plotting the primary scattered beam relative to the secondary fluorescent X-rays creates a linear trend specific to a particular wafer. The slope of this linear trend largely depends on the wafer surface roughness determined by AFM.

Surface Roughness Analysis Platforms

Alfa Chemistry has high-precision and advanced testing instruments, which can provide accurate test results. Our testing instruments include, but are not limited to, the following:

• Jupiter™ XR Large-Sample Atomic Force Microscopy (AFM)
• RIGAKU VPD-TXRF

Detectable Samples Include:

• Wafer specification diameter: 150mm, 200mm, 300mm.
• Material: Si, GaAs, Ge, SiC, InP.
• Conductivity: P or N type.
• Surface: Cutting, grinding, etching, polishing and patterned.
• Flat/notch: All SEMI standard flat or notch.

If you want to test other types of samples, please contact us for consultation.

Testing Standard

• ASTM F1810-1997 Standard Test Method for Optimum Statistics of Silicon Wafer Erosion or Surface Defects.
• ASTM F847-1994(1999) Standard Test Method for Crystallographic Orientation X-ray Measurement of Reference Surface of Single Crystal Silicon Wafer.
• BS ISO 14706-2014 Surface Chemical Analysis. Determination of Elemental Contaminants on the Surface of Silicon Wafers Using Total Reflection X-ray Fluorescence (TXRF) Spectroscopy.
• GB/T 24578-2015 Total Reflection X-ray Fluorescence Spectrum Test Method for Metal Contamination on Silicon Wafer Surface.

Reference

1. Noack B, et al. (1998). "Technique to analyze large-area surface roughness of a wafer using TXRF." Proc. SPIE 3509, In-Line Characterization Techniques for Performance and Yield Enhancement in Microelectronic Manufacturing II.