In-field CD uniformity control by altering transmission distribution of the photomask using ultra-fast pulsed laser technology

摘要

As pattern feature sizes on the wafer become smaller and smaller, requirements for CD variation control has become a critical issue. In order to correct CD uniformity on the wafer, the DUV light transmission distribution of the photomask was altered using an ultra-fast pulsed laser technology. By creating a small scattering pixel inside the quartz body of the mask, a multitude of such points creates Shading Elements inside the quartz according to a predetermined CD variations distribution map. These Shading Elements reduce the dose of scanner's laser illumination onto the wafer per a local area. Thus by changing the local light intensity, inside the exposure field, to a required level during the photolithographic process the wafer CD is changed locally inside the field. This complete process of writing a multitude of Shading Elements inside the mask in order to control the light transmission and hence wafer level CD locally is called the CD Control (CDC) process. We have evaluated the tool utilizing Ultra fast laser pulses (CDC 101) for local transmission and CD controllability on the wafer. We used Binary and Att-PSM test masks and three kinds of test patterns to confirm the sensitivity of transmission and CD change by the attenuation levels of Shading Elements which is sequentially changed from 0% to 10%. We will compare the AIMS results to printed CD on wafer or simulation results, so that we can correlate the transmission change and CD change by the attenuation levels. This paper also reports the CD uniformity correction performances by using attenuation mapping method on Binary mask. We also cover how Shading Elements affect the phase and transmission on the Att-PSM.