US20260049928
2026-02-19
Physics
G01N21/3581
The patent application describes a measuring apparatus designed to effectively generate terahertz (THz) signals for analyzing semiconductor devices. The apparatus includes a stage with a transmissive wafer chuck for holding a sample wafer, which typically consists of a silicon substrate with additional material layers. A femtosecond laser beam is generated by a light source and is split into multiple sub-laser beams to facilitate multi-photon excitation at specific measurement positions on the wafer. This technique allows for detailed analysis of ion doping concentrations at various depths within the semiconductor material.
Terahertz signal spectroscopy is increasingly used in semiconductor measurement, integrating THz-generating and detecting devices. These devices emit THz waves to gather data about a sample. A distinctive approach in this field involves using probe light with a different wavelength from the THz signal, which interacts with a nonlinear crystal to convert wavelengths, allowing indirect detection of the THz signal. This background knowledge forms the basis for the innovative aspects of the current application.
The apparatus features a light source unit capable of generating a femtosecond laser beam. This beam is divided into four sub-laser beams by a confocal laser-induced THz emission microscopy (LTEM) unit. Three of these beams overlap at a targeted measurement position on the wafer, creating multi-photon excitation. The LTEM unit achieves this by directing the beams onto the lower surface of the silicon substrate, optimizing the generation of THz signals for measurement purposes.
The described method involves splitting the femtosecond laser into two primary beams, which are further divided for precise excitation and measurement. The multi-photon excitation process is crucial for generating a THz signal, which penetrates through any insulating layers to reach the silicon substrate's upper surface. This method enables the detection of changes in THz signal absorption, providing insights into the semiconductor's internal structure and doping levels.
The application includes several diagrams to illustrate the apparatus and its operation. For instance, FIG. 1 provides a block diagram of the THz signal measuring apparatus, while subsequent figures (FIGS. 2A-2C) detail the apparatus's components and functionality. Additional diagrams (FIGS. 3A-3C) demonstrate the generation and spatial resolution of THz signals, and flowcharts (FIGS. 8A and 8B) outline the measurement method. These visual aids help clarify the complex processes involved in the apparatus's operation.