As the critical dimensions (CDs) become smaller as semiconductor device patterns become finer, there is a problem that the depth of focus (DOF) becomes shallow at formation of contact holes. To solve this problem, we at Gigaphoton have developed the technology that allows expansion of the DOF by greatly varying the spectrum bandwidth of a laser.
Figure 10 shows variation of the DOF when simulator “prolith v9.3” was used to change the spectrum bandwidth.
As the result, a DOF 4.5 times that of the conventional DOF can be achieved by increasing the spectrum bandwidth up to E95=2.4 pm from the conventional bandwidth of E95=0.3 pm.
At Gigaphoton, as shown in figure 11, we have succeeded in developing a technology that can increase the E95 more than 2.4 pm while maintaining the output of E95=0.3 pm by using the method for switching the mode in the line narrowing module (LNM). At this time, the spectrum waveform is almost symmetrical, thus causing no problem in lens design for lithography tools.
This sMPL technology was tested in a high-volume manufacturing environment in partnership with a leading scanner manufacturer and device manufacturer.