| Popis: |
We demonstrate an approach to cross-section and measure sub- 0.25 micrometer photoresist profiles in both a manual and an automated fashion. This approach includes the use of a focused ion beam (FIB) system to cut small trenches through photoresist lines, leaving a clean, vertical face to measure. We demonstrate the advantage of using this process over existing techniques in the semiconductor industry. A FIB can locally cross-section the photoresist, resulting in a side- wall that is comparable to that of a mechanical cleave. It can then measure the profile of the photoresist at multiple points using a 5 nm gallium probe. The system accomplishes the entire process inside one vacuum chamber with a limited number of steps. In contrast, when using a SEM to measure profiles, the sample must be mechanically cleaved outside of the vacuum chamber, potentially destroying the entire part and leaving a slightly distorted viewing face. Also, a SEM probe can cause swelling of the photoresist due to higher currents and penetration depths than a FIB probe and must therefore be used at low accelerating voltages. When operated at these low accelerating voltages, the SEM has degraded resolution with a spot size near 10 nm. A scanning probe microscope (SPM), on the other hand, can non-destructively measure profiles, but it is slow and less automated than the FIB or SEM. Unlike a FIB, the SPM lacks the ability to image the material transition directly beneath the photoresist. We also address concerns of sample damage, gallium contamination, and image quality. |
