Nobuo Gotoh

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.

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.

Development of an electron-beam optical column for the mask lithography system

Mask accuracies for the newest and next generation devices are very tight. The SIA Roadmap indicates writing accuracies (CD uniformity) of 18 nm and 13 nm for 1-Gbit and 4-Gbit DRAM 4X reticles, respectively. To meet this challenge, a new electron optical column is being developed for an electron beam mask writing system. The column has a beam current density of 20 A/cm2 (50 kV), a beam blurring of 0.06 micrometer at a 16 micrometer2 beam size, and a total aberration of less than 0.05 micrometer at 1 mm deflection length. The key technologies for this column are as follows: (1) Shorter column length and wider beam half-angle for reduction of Coulomb interaction; (2) Per shot focus correction of space charge effect; (3) In-lens, single stage electrostatic beam deflection system with focus and astigmatism correction. In this paper, we report the simulation results of this electron optical column design.

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.

Evaluation of overlay accuracy of phase-shift image for 65-nm node masks

A 65 nm node mask is required to have total alignment accuracy of 20 nm (3σ) or less for 1st and 2nd layers, including the positional accuracy of each layer. We have developed a new electron beam mask lithography process using “alignment-and-height” marks to minimize the displacement between two layers resulting from additional bowing and contraction on the blank surface after the 1st layer exposure. The new process consists of the following steps: 1. Write “alignment-and-height” marks on the edge of a mask simultaneously with the pattern of the 1st layer. 2. Measure the position and height of “alignment-and-height” marks before writing the 2nd layer. 3. Create a position/height correction map to write the 2nd layer. 4. Write the 2nd layer with reference to the correction map. Basic system attributes, such as beam origin and positional drift of mask blank, are monitored and adjusted throughout the process. We tested the process and achieved an alignment accuracy of 20 nm (3σ) between 1st and 2nd layers regardless of the density of the pattern area ratio, confirming that the process is effective for 65 nm node phase shift mask exposure.

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.