Kazumitsu Tanaka

Performance of improved e-beam lithography system JBX-9000MVII

An electron beam mask writing system JBX-9000MV for 150- 180nm technology node masks was developed by JEOL Ltd. and its design concept, technologies introduced and results of initial evaluation were reported in 1998. We have improved this system to cope with the production of masks for 130nm technology node. Some of the new technologies developed for the improvement of writing accuracy, especially CD accuracy, and the results are reported in this paper.

Shot number analysis at 65-nm node mask writing using VSB writer

It depends for the writing time of variable shaped electron-beam (VSB) writing system on the number of writing shots. For shortening of writing time, it is most effective to reduce the number of shots. However, Resolution Enhancement Technologies (RET), such as OPC and PSM, make the VSB shot number increase explosively, in addition to reduction of LSI pattern size, and worsens the writing throughput. This is a serious problem for VSB mask writer, and the improvement of a writing throughput is required. In order to solve this problem, we inquired towards diversifying beam shape only from a rectangle. First, we investigated about the curtailment effect of the number of shots by trapezoid aperture adoption. Some latest VSB writer has adopted a triangle shaped aperture to compose the slanting figure in the LSI pattern efficiently. We investigated the efficiency of forming the slanting figure with trapezoid or parallelogram apertures compared with initial triangle aperture shot number. As the result of that, shown in Fig.1, we obtained the result that the shots number was reduced into 50% or more compared with initial triangle shots number. And, we examined a possibility of uniting and applying the character projection (CP) technique, which is adopted as EB direct writing (DW), to mask writing. Since pattern size is, for example, 4 times larger in the case of mask writing compared with the case of EBDW, the area that can extract a common CP pattern out from LSI patterns at mask writing is smaller than EBDW. Then, we extracted CP aperture pattern from cell library data for logic LSI. We obtained the result, shown in Fig.2, that the shot number that was used CP aperture was reduced into about 35% compared with initial VSB shots number. However, the arrangement number of aperture has restriction, and if the arrangement number decreases, the curtailment rate of the shots number will fall. These two techniques are fundamentally effective in curtailment of writing shots number. Furthermore, we will discuss with the possibility of applying these techniques to mask writing and with some problems to solve for the application of these techniques.

Development of a next-generation e-beam lithography system for 1-Gb DRAM masks

A new electron beam lithography system for masks needed in production of 1Gbit DRAM devices was developed and evaluated. The system features a variable shaped beam, 50 kV accelerating voltage, and a step and repeat stage, and incorporates new technologies, including a high resolution high current density electron optical system, a per-shot beam correction unit, a high precision beam detection system utilizing the curve fitting method, and a single-stage 20 bit beam deflection unit. The system achieves a minimum linewidth of 200 nm or less, pattern uniformity of 20 nm within field, and a positional accuracy, including field stitching accuracy, of 20nm within a field, resulting in an exposure speed at least 5 times faster than the existing model, the JBX-7000MVII.

Performance of the improved JBX-9000MV e-beam lithography system

An electron beam mask writing system JBX-9000MV for 150- 190nm technical node masks was improved to cope with the production of masks for 130nm technology node. Some of the new technologies developed for the improvement and their results are reported in this paper.

Development of a Next Generation E-Beam Lithography System

One of the keys for ULSI lithography at a feature size ranging from 180 nm to 150 nm is a stable supply of ultra high precision reticle masks. To meet this demand, we have developed a new electron beam lithography system for reticle masks which offers an exposure accuracy of 20 to 30 nm. The system features a variable shaped beam, 50 kV accelerating voltage, a step-and-repeat stage, nd incorporates new technologies. These include a high resolution-high current density electron optical system, a per-shot focus and shot time correction unit, a high precision beam measurement system utilizing the fitting function method, a single-stage 20 bit electrostatic beam deflection unit and beam-shot smoothing technology. The system achieves a minimum line width of 100 nm or less, a pattern size uniformity of 16 nm (3 sigma) within a field, a field stitching accuracy of plus or minus 19 nm or smaller, and a pattern placement accuracy of plus or minus 29 nm or smaller, resulting in an exposure speed of 3 to 5 times faster than the existing model.

Development of EB lithography system for next generation photomasks

A higher quality electron beam (EB) mask lithography system is now required in an advanced field aimed at 1 Gbit DRAM chips. For this purpose, photomask accuracies of 0.03 micrometers to 0.02 micrometers are needed, for the feasibility of an EB lithography system with these accuracy levels is discussed. The error sources of a commercial EB lithography system with a variable shaped beam system and step and repeat writing strategy are examined. The development plans to minimize these errors are described and early results, specifically the field stitching error, obtained from these developments are shown. The mean stitching error was +/- 0.023 micrometers and the random stitching error was +/- 0.030 micrometers . From the analysis of error budget, it is shown that a field stitching accuracy level of 0.02 micrometers will be attainable after the completion of above-mentioned development plans.

Development of an e-beam lithography system for 100- to 90-nm node reticles

A new advanced electron beam lithography system JBX-3030MV has been developed to meet requirements for the production of masks for 100-90nm technology node. The system features a variable shaped beam, 50kV accelerating voltage, a step-and-repeat stage, and incorporates new technologies. These include a high resolution-high current density electron optical system, triangle beam shaping system, higher speed electro static beam deflection system, higher accuracy proximity effect correction system, and glass in glass out material handling system. The writing accuracy of the system has satisfied the specifications required for the production of 100-90nm node reticles with extendibility of 65nm node reticles.