Chemical Vapor Deposition

The ability to deposit thin films of materials onto a substrate is the foundation of semiconductor technology. Thin film deposition is primarily classified into two groups – processes that involve a chemical reaction and ones with a physical reaction.

There are various types of deposition processes caused by chemical reactions; such as Chemical Vapor Deposition (CVD), thermal oxidation, epitaxial growth, etc. During the course of the manufacturing cycle, depending on the device level, each wafer undergoes several deposition process steps that deposit films of various materials such as oxide, nitride, polysilicon, Si cap, etc. each with different material properties such as crystalline structure, chemical composition, etc.

Challenges

The quality of the thin films is critical to the chip performance and in addition, defines the performance of the subsequent processing steps, which makes it essential to monitor and control key characteristics of the deposition process.For example, film thickness uniformity after deposition impacts the performance of chemical mechanical planarization (CMP). With tightening process windows, thickness control is needed both at deposition and at CMP steps.

Another example is Si cap thickness control in SiGe channel. This impacts channel reliability, making  accurate and precise measurements of Si cap thickness on top of the SiGe channel critical. Scatterometry is the only non-destructive measurement method that can provide the full profile of the SiGe channel. This application presents a number of challenges, such as cross-talk between SiGe and Si height, that need to be addressed in order to provide a reliable and accurate measurement.

Nova offers metrology solutions to different deposition processes with the ability to measure thickness and other film properties of solid surfaces or complex profiles. As the process windows shrink, demand for high-precision thickness measurements is increasing. With the industry’s leading reflectometry design, Nova’s metrology systems provide the Å level precision needed for the thin-film thickness control.

For example, Nova solution for the measurements of SiGe channel is tailored to overcome the most troubling scatterometry challenges. Oblique channel in Nova T600 provides improved sensitivity required to separate the SiGe and Si cap films and the holistic metrology options in NovaMARS improve the accuracy of the channel profile parameters. Combination of hardware and software provides the required metrology for SiGe channel for advanced technology nodes.