The PREM PEAQS center recently published a paper, “Real-time optical thickness determination for producing ultra-thin silicon membranes using anisotropic potassium hydroxide etching” in MRS Advances.

The paper focuses on the team’s efforts to control the thickness of bio-membranes that are used for lung-on-a-chip applications—tools designed to simulate the function of lung tissues. Typically, researchers thin silicon wafers via a process called wet etching, which involves submerging the wafer in a chemical solution that selectively removes silicon to thin the wafer or shape it into specific designs. Researchers commonly use this technique to create intricate, precise features in microelectromechanical systems.

Instead, the PEAQS team wanted to determine the membranes’ thickness in a non-invasive way—creating a tool to measure the thickness of silicon membranes using light. As part of that effort, they made very thin silicon membranes and took pictures of how light passed through them. They compared the brightness of the light in the pictures with precise thickness measurements from a specialized tool called a scanning electron microscope. The paper shares the relationship they found between the light data and the actual thickness.

Read the paper.

^{Here, we see a thinned membrane that’s approximately 5 micrometers thick.}