Multiple patterning ArF immersion lithography has been expected as the promising technology to meet tighter leading edge device requirements. To enhance the resolution and productivity for multiple-patterning application, key light source performances are spectral bandwidth stability and wavelength stability. The increased spectral bandwidth stability contributes to more precise critical dimension (CD) control and improves device yield. The increased wavelength stability can realize accurate focus and improve overlay accuracy. Our new spectral bandwidth control module improves E95 spectral bandwidth stability. The spectral bandwidth has deviations by thermal history with light source operations. It should be always controlled tightly even after a quiescent interval, such as wafer loading. In our laser system, a spectral bandwidth is controlled by adjusting the wavefront of a laser beam using a two-lens optical system within a resonator. A high speed actuator equipped the movable lens enables E95 spectral bandwidth stability to be less variation. New designs of drive mechanism suppress the lens vibration and spectral bandwidth error. This technology enables 3-sigma of E95 spectral bandwidth field average to be under 5 fm. This large shrinkage for E95 spectral bandwidth stability is the key to improve larger focus budgets for a leading edge processes. A new designed line narrowing module (LNM) improves wavelength stability. The wavelength is controlled by changing the rotation of a beam expander prism using actuator. Wavelength stability is improved further by the anti-vibration structure of the actuated prism in the LNM. The new design prism holding mechanisms reduce the mass of actuator load. This increases the stiffness of the system and suppresses the vibration of the prism rotation. New LNM reduce wavelength stability about 20%. The improvement in wavelength stability contributes to accurate focus and overlay. In addition, the lifetime of LNM is extending to reduce the Cost of Operation (CoO) and the light source downtime. A new ArF excimer laser, GT66A, maximizes device yield, process productivity and minimizes the operational costs for chipmakers.