LSI - LSI

Abbreviation for large scale integration. Also called large-scale integrated circuit. Using photolithography technology, minute transistors and diodes are fabricated on a silicon substrate and wired to realize many functions. A chip with more than several thousand circuit elements is called LSI, a chip with more than 100,000 is called VLSI (very large scale integration), and a chip with much more than that is called ULSI (ultra large scale integration). Currently, more than 40 million transistors are built into a single chip. The advantage of LSI is that it is smaller, which allows for higher performance and speed, and also improves yield. However, as the chip becomes smaller, the thickness of the _SiO2 film becomes less than 20 nm, which increases leakage current and causes problems with power consumption when the chip is off. High-permittivity films, which can achieve a thickness equivalent to _SiO2 with a thicker film, are attracting attention as a new gate insulating film. In addition, circuit design has become very complex as the number of wiring layers has now reached 10, and the proportion of the wiring layer in circuit operation compared to transistors has increased dramatically. For this reason, even if transistors are miniaturized to achieve high performance, it is difficult to achieve high speeds as a system, so Cu, which has a lower resistivity than Al and is more resistant to electromigration, is used for the wiring metal, and low-k films with a lower dielectric constant than _SiO2 are used to separate wiring. The former processes related to the gate insulating film and the structure of the transistor itself are called front-end processes, and the latter processes related to wiring are called back-end processes. [See alternative terms] Integrated circuits, copper wiring

Source: Morikita Publishing "Chemical Dictionary (2nd Edition)" Information about the Chemical Dictionary 2nd Edition

large scale integrationの略称．大規模集積回路ともよばれる．フォトリソグラフィー技術を駆使して，シリコンの基板上へ微細なトランジスターやダイオードなどをつくり込み，配線して多くの機能を実現している．数千個以上の回路素子が集積されているものをLSI，10万個以上をVLSI(超LSI)，さらにこれを大きく超えるものをULSI(超々LSI)とよぶ．現在では4000万個以上のトランジスターが一つのチップに組み込まれている．LSIのメリットとして，小さくすることで高性能・高速化を実現し，歩留まりも向上している．しかし，微細化に伴い，SiO₂膜の膜厚が20 nm 以下となりリーク電流が増加し，オフ時の消費電力の問題が生じ，より厚い膜厚でSiO₂に等価な膜厚が得られる高誘電率膜が，あらたなゲート用絶縁膜として注目されている．また，高機能化に伴い回路設計が非常に複雑になり，配線層数が現在では10層にも及び，トランジスターに比べて回路動作に占める割合が極度に増した．このため，トランジスターを微細化して高性能にしても，システムとして高速化を実現することが難しくなり，配線金属にAlよりも抵抗率が低く，エレクトロマイグレーションに強いCuが用いられ，配線間の分離にSiO₂よりも誘電率の低い低誘電率膜が用いられるようになっている．前者のゲート絶縁膜やトランジスター自体の構造に関連するプロセスをフロントエンドプロセス，後者の配線関連のプロセスをバックエンドプロセスとよぶ．[別用語参照]集積回路，銅配線

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