Hirohiko Shinonaga

New distortion metrology using reticle coordinate error

There are several ways to measure distortion of lithography exposure equipment, and with each of the distortion metrology technique, coordinate errors of distortion measurement pattern on the reticle affect distortion measurements. The most common way to remove the impact of the reticle coordinate error is to measure such errors in advance using a pattern placement metrology tool and correct distortion measurements based on the coordinate error. We have found, however, that when measuring distortion using two different reticles on the same exposure tool, the two measurement results did not agree with each other with a difference at a 20 nm level (3 sigma) even after being corrected according to the measured reticle coordinate error. After studying this problem, we successfully had distortion measurements on the wafer using two different reticles agree with each other at a 10 nm level (3 sigma) by introducing a technique called STofs., system offset, method. This paper reports that exposure tool distortion can be extracted with more precision by applying the new reticle coordinate error measurement technique.

Stepper exposure system for the quarter-micrometer age

We at Canon are ready to offer three types of steppers as a solution of 0.25micrometers age photolithography. The feature summary of the respective steppers are shown. These three steppers share the same body structure and software platform for perfect mix and match usage. The combination of these three systems should allow the chip manufacturers to achieve the most cost effective 0.25 micrometers ULSI mass production. This paper focuses on the following two points: (1) the outcome of the performance on the new KrF laser based exposure system (FPA-3000EX3); (2) overlay experimental results (mix and match with FPA-3000i4 and FPA- 3000iW). The FPA-3000 EX3 is a newly introduced KrF laser based stepper for 0.25micrometers resolution, having a high numerical aperture and wide image field. The basic printing performance of the system, such as DOF and CD LINEARITY are explained in this paper. The cost effective production, with the mix and match of the lithographic tools, is becoming more important in the 0.25micrometers age. The performance of the high throughput stepper, FPA-3000iW is discussed from the viewpoint of mix and match with critical layer steppers.

High volume production trial of mirror segments for the Thirty Meter Telescope

The Thirty Meter Telescope is a next-generation optical/infrared telescope to be constructed on Mauna Kea, Hawaii toward the end of this decade, as an international project. Its 30 m primary mirror consists of 492 off-axis aspheric segmented mirrors. High volume production of hundreds of segments has started in 2013 based on the contract between National Astronomical Observatory of Japan and Canon Inc.. This paper describes the achievements of the high volume production trials. The Stressed Mirror Figuring technique which is established by Keck Telescope engineers is arranged and adopted. To measure the segment surface figure, a novel stitching algorithm is evaluated by experiment. The integration procedure is checked with prototype segment.

Test production of a mirror segment for the Thirty Meter Telescope

The Thirty Meter Telescope (TMT) is a next-generation optical/infrared telescope to be constructed on Mauna Kea, Hawaii toward the end of this decade, as an international project. Its 30 m primary mirror consists of 492 off-axis aspheric segmented mirrors. This paper describes the progress of the test fabrication of an outermost mirror segment for the TMT as a joint R&D program between National Astronomical Observatory and Canon. A zero-expansion glass CLEARCERAM™ blank was polished by a computer-controlled small-tool polishing machine (CSSP, Canon) and its surface shape was measured by a touch-probe measuring machine(A-Ruler, Canon). Residuals of lower Zernike terms of the surface shape were 11 nmRMS, clearing the original specifications based on the structure function. There remains, however, a need to fulfill latest revised specifications. Possible solutions to improve and achieve the new specifications and a plan for revising the process for mass production are also described.