Fumikazu Itoh

Practical phase‐shifting mask technology for 0.3 μm large scale integrations

An i‐line phase‐shifting mask technology intended for practical use has been developed. The new technology can provide defect‐free phase‐shifting masks and can produce 0.3 μm large scale integration with large lithographic latitudes. The phase‐shifting masks manufactured here apply the following two major techniques. The first technique is to form phase‐shifting patterns on the chrome mask. This technique features single‐layer shifters using an organic spin on glass (SOG), a simple patterning process of the SOG, and a focused ion beam gas‐assisted etching repair process of shifter defects. The second technique is to create half‐micron chrome patterns using a high‐accuracy e‐beam writing system ‘‘EB‐MX’’ and high‐resolution chemically amplified e‐beam resist ‘‘PSR’’.

Mechanism of ion impact photoemission change of Si and Al during focused ion beam milling of LSI

Focused ion beam milling is an important tool for LSI modification and failure analysis. For both of these applications, the depth control in milling is a major requirement. The FIB machine we used was equipped with an ion impact photoemission detector for use with both Si and Al. We studied the photoemission change mechanism during LSI milling by altering the acquisition area of the photoemission, and by chemical analysis on the side walls of the milled holes. Si emission varies with the surface area of SiO2. Al emission originates in the edge lines of Al and SiO2 at the bottom of the hole, and from the Al redeposited on SiO2 of the side walls. On the edge lines and the side walls, ion mixing of SiO2 and Al enhances the Al photoemission. We demonstrated that an almost 100% modifying yield in both Al wire cutting and contact hole milling is possible by observing the variance of both emissions.

Focused Ion Beam Milling Technology for On-chip Wiring Modification System for LSI.

During debugging logic LSIs, a period to reproduce LSI in order to change the logic design is becoming longer. To reduce the period from several weeks down to one day, an on-chip direct wiring modification system, using the focused ion beam (FIB) milling and the laser CVD, has been developed.This paper describes a precise FIB milling technique for cutting the wirings and making the via holes to the wirings of the LSI. Milling depth control by monitoring the ion induced photo-emissions and the milling strategy to overcome the surface steps of the LSI resulted in the milling depth accuracy of ±0.25μm. The system, consist of the FIB milling described in this paper and the laser CVD, has been applied to the logic modification of the LSIs of Hitachi M880 mainframe computer. Several tens of cuts, vias on an LSI chip were made by FIB, and the several jumper wirings were made by laser CVD. The average yield of modified LSI chips of 91.8% was achieved.