Electron Beam Direct Writing System Research Articles

Cost-effective and channel-scalable hardware decoders for multiple electron-beam direct-write systems

Data throughput is a critical metric in a multiple electron-beam direct-write (MEBDW) system so that heavy-duty data processing equipment is required. The main challenge is about how to achieve high performance with cost-effective techniques. We propose a high compression rate algorithm for efficient data transfer and high speed decompression hardware to raise data throughput of the system. The hardware decoder uses pipeline architecture, a run-length encoding first-in-first-out queue, and parallel dispatch logic to increase the throughput. The decoder is evaluated on field-programmable gate array and simulated with layout images that are compressed using the proposed compression software. The results demonstrate 18.2% better compression rate and 254.8% better throughput than the previous work with similar hardware cost. Because no static random-access memory is used in the design, the channel numbers of the system can be easily scaled up, which makes it possible for the next-generation MEBDW system to achieve higher wafer per hour targets.

Efficient layout data compression algorithm and its low-complexity, high-performance hardware decoder implementation for multiple electron-beam direct-write systems

A lossless electron-beam layout (EBL) data compression algorithm, LineDiff Entropy v2.0, and its low-complexity, high-performance hardware decoder for multiple electron-beam direct-write lithography systems are proposed. The algorithm compares consecutive data scanlines and encodes the data based on the change/no-change of pixel values and the lengths of pixel sequences. Then, the compaction steps of data omission, merging, and encoding of consecutive long identical scanlines are applied. Unique short codes are assigned to data with high occurrence frequency. The hardware decoder is designed as three circuit blocks that perform entropy decoding, decompaction, and EBL data generation through parallel outputs. The results demonstrate that our algorithm can achieve excellent compression performance and that the hardware decoder can decompress data at very high data rates.

Development of Multibeam Electron Beam Direct Writing System Using Third-Order Imaging Technique

We report the development of a new electron beam direct writing (EBDW) system embodying a concept that can realize both high throughput and fine resolution. The equipment has a multicolumn system with the third-order imaging technology, which obtains steep edge acuity with high current density as compared with conventional shaped beam methods. We attempt to apply this to via/contact layers, for which it is difficult to obtain resist patterns using any optical lithography systems. We also showed proof of concept of third-order imaging serving as a technique for simultaneously satisfying improvement in current density without beam blur and forming a beam to a desired shape. The advantage of the third-order imaging technique is a potential solution that may break through the technological impasse of high current density versus high resolution. We are currently engaged in enhancing the high-acceleration-energy and multicolumn system and in its development for mass production.

Electron-beam direct writing system employing character projection exposure with production dispatching rule

An electron-beam direct writing (EBDW) system with a character projection (CP) aperture is a promising candidate as an effective maskless lithography tool to realize a system on a chip fabrication process at low cost with quick turn-around time. We have proposed an approach to enhance the throughput of an EBDW system by using a production dispatching rule. Through an event-driven simulation analysis in the backend of the line, the effect of production dispatching rules on the throughput and the cost in an EBDW system is evaluated. We considered four kinds of dispatching rules, FIFO, APA, LWKR, and SLACK. FIFO is a usually used dispatching rule and gives the highest priority to the waiting lot that came in first at the EB lithography process. In APA, the highest priority is given to the waiting lot that does not require the CP aperture exchange. In LWKR, the highest priority is given to the waiting lot associated with the job having the least amount of total processing time remaining to be done. In SLACK, the highest priority is given to the waiting lot with the shortest slack. Simulated result shows that the EBDW system with APA enhances the throughput more than 1.2 times as compared to that with FIFO, LWKR, or SLACK, and has a throughput of 5wafers∕h or more. Furthermore, compared with the cost per chip for FIFO, the APA rule reduces the cost/chip by more than 30% at the cost minimum lot arrival rate point.

Improved Proximity Effect Correction Technique Suitable for Cell Projection Electron Beam Direct Writing System

Electron beam (EB) direct writing is expected to play an important role in the field of lithography for manufacturing future advanced ULSIs. Cell projection techniques are of particular interest, which may make the EB direct writing system practical for use in ULSI memories with many repeated patterns. However, the proximity effect of such systems disturbs the formation of fine 0.2 µ m level patterns throughout the patterning area. In order to solve this problem, we have developed an improved proximity effect correction technique suitable for use in a cell projection EB direct writing system. This technique makes use of smaller cell projection shot (CPS) size in the edge region than in the center region in the EB direct writing area with dose compensation between CPSs, based on the self-consistent method. Utilizing this technique, we can obtain fine 0.2 µ m patterns with 0.02 µ m critical dimension (CD) control patterns, which are required to manufacture 1Gbit dynamic random access memories (DRAMs).

Ten-Nanometer Resolution Nanolithography using Newly Developed 50-kV Electron Beam Direct Writing System

A high energy 50-kV electron beam direct writing system which has a gas introduction line has been developed. Several aspects of the performance of this system are demonstrated. The electron beam size has been improved to be less than 5 nm. 10-nm width line patterns with 50-nm periods in PMMA resist on a thick Si substrate are demonstrated. It is observed that fewer proximity effects occur when a high-energy electron beam is used. 20-nm-width lines and 20-nm-diameter Au-Pd metal patterns have been fabricated by a lift-off method. 14-nm-diameter carbon dot patterns were deposited on a Si substrate by electron-beam-induced deposition using Styrene gas.

Proximity effect correction for high-voltage electron beam lithography

A new proximity effect correction method using an approximate dose correction formula has been developed. The method is especially effective for a high acceleration voltage. In the case of an acceleration voltage of 40 kV, the correction error for the energy deposition in the resist was estimated analytically to be less than ±7%. The deviations of the line and space pattern dimensions were also evaluated experimentally to be less than ±0.03 μm. The calculation time for correcting a 4-Mbit dynamic random access memory (DRAM) was only 0.7 h using a large-scale computer of 15 MIPS (mega instructions per second). Even if the LSI patterns have no hierarchical structure, in an application specific integrated circuit (ASIC) pattern the calculation time would be 1 h or so. A 4-Mbit DRAM pattern can be written using the electron beam direct-writing system EX-7 with sufficient accuracy. These results suggest that the method is practical.