成果報告書詳細
管理番号20120000000873
タイトル*平成23年度中間年報 ナノテク・先端部材実用化研究開発/水素拡散を制御した高信頼性絶縁膜の開発とフラッシュメモリーへの応用
公開日2012/7/10
報告書年度2011 - 2011
委託先名独立行政法人物質・材料研究機構 ルネサスエレクトロニクス株式会社 独立行政法人産業技術総合研究所 国立大学法人東京大学 株式会社日立国際電気
プロジェクト番号P05023
部署名電子・材料・ナノテクノロジー部
和文要約和文要約等以下本編抜粋:
1. 研究開発の内容及び成果等
本研究では、次世代フラッシュメモリーを高密度化し絶縁膜の信頼性を向上するために、膜中にナノレベルの水素貯蔵層を埋め込み、酸化物/Si 界面の劣化を抑制するための新材料の開発をコンビナトリアル手法で探索することを目的としている。そのために、独立行政法人物質・材料研究機構、ルネサスエレクトロニクス株式会社、独立行政法人産業技術総合研究所、東京大学、株式会社日立国際電気がそれぞれ協力し、目標を実現するための研究開発項目を実施している。その中で、独立行政法人 物質・材料研究機構では平成23 年?平成24 年3 月までに、
1) ?2「現行フラッシュメモリーの水素貯蔵層の組成と構造の解明」の理論解析
2) 「コンビナトリアル手法による水素貯蔵層超薄膜の探索と機構解明」
3) ?1「プレーナー型電極/水素貯蔵層/SiN/SiO2/Si の作製と特性評価」
4) ?3「トンネル領域形状が及ぼすトンネル絶縁膜信頼性への影響調査」
を行った。
英文要約 In this research project, to achieve a highly reliable insulating film for future flash memory, we are making effort to develop a hydrogen storage layer at the gate and nitride layer. One of the candidates for the hydrogen reservoir is Si-N-O films which is formed by oxidation of SiN grown on Si by plasma CVD.
In this year, we could make clear that the ideal hydrogen reserving structure was found to be Al2O3/SiAlON stacked layer by first principle calculation and NRA measurements.
The Al2O3/SiAlON stacked layers showed that there was less leak current and less defect , meaning the film had less fixed charge. These materials and stacked structure information was informed to AIST team to make Fin type flash memory device, which is the final goal of this project.
 We also made important progress on process development aiming at the reliability improvement for tunnel dielectrics. With the newly developed nitridation process; we succeeded in preparing the CVD dielectrics with two N-rich interfaces. Based on the lifetime evaluation and the cumulative charge stress per P/E cycle, average P/E endurance of the new oxynitride dielectrics is estimated to reach 300k cycles,
We further developed the new nitridation method by adding the surface treatment on the oxynitride surface. It was confirmed that water steam treatment followed after the air exposure can make remarkable decrease of a minority group, which happened in the cumulative failure distribution. This surface treatment was expected to have great potential for application. Moreover, the desorption behaviors of SiO and the H2 species observed by thermal desorption spectrometry (TDS) indicated that the additional surface treatments likely related to the formation of the hydrogen storage layer. We suggest again therefore that constructing an H-storage layer to resist against the penetration of H-related species into the tunnel dielectric is promising way for enhancing the reliability of the tunnel dielectrics.
Based on these research, we have developed device fabrication processes for the FinFET flash memory. By using the developed processes, we have succeeded in the fabrications of (1) split-gate type FinFET flash memories, for the first time, (2) double-gate (DG) and tri-gate (TG) flash memories, (3)poly-Si channel FinFET flash memories. The electrical characteristics of the fabricated devices have been investigated systematically. The split-gate type cell transistors with the same control gate-length (LCG) of 176 nm show much smaller Vt distribution. The measured source-drain (SD) breakdown voltage (BVDS) is higher than 3.1 V even the LCG was down to 76 nm. This indicates that the developed split-gate type tri-gate flash memory is very effective for scaled NOR-type flash memory. It was found that some superior Id-Vg characteristics are observed in the scaled poly-Si channel FinFETs with gate length (Lg) down to 54 nm or less.
To detect stability and diffusivity of hydrogen in the devices, the devices were investigated by nuclear reaction analysis. From the results, the hydrogen species at the SiAlON (12nm)/Si3N4 (10nm) interface was found to be more stable.
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