Resist reflow techniques have widely been adopted for lithography in resolution limited region. During the reflow process, resist patterns are heated over its glass temperature through number of temperature steps. Early works have focused how the temperature steps during heat-up process can be effectively controlled for critical dimension (CD) and the pattern profile after reflow. However, for a specific application that needs moderate CD and profile change, adjusting heat-up parameters would not be sufficient to achieve good CD and profile control and additional relevant parameters should be accounted.
In this paper, we count surface treatment condition on reflow process as an additional control parameter. We measured CDs with varying surface treatment parameters of substrate on square arrays of resist islands with 300 nm island-to-island gap space. We found that the amount of after develop CD to after reflow CD bias decreases as contact angles of substrates increases. In conclusion, we prove the resist reflow CD can be controlled precisely by adjusting the substrate coverage of hydroxyl groups during adhesion treatments in addition to the temperatures for the resist reflow process.
With the development of a CMOS Image Sensor (CIS), the pixel size of a CIS is continuously decreasing. It makes the
photo diode smaller and smaller in the unit pixel and, as a result, the sensitivity is reduced at the same time. A micro lens
(ML) is added to improve the sensitivity of CIS. The size of ML is reduced with the pixel size and it almost arrived at the
limitation of the size which is governed by diffraction. In this paper, we simulate the diffraction feature of a ML with an
electro-magnetic wave simulation. The efficiency and the crosstalk of some ML which have a size near the diffraction
limit are calculated and compared. From the simulation result, we suggest a guide line of the ML design.