Selective Metal Silicide Formation in Semiconductor Memory Gates
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Solution Overview
Problem
The formation of metal silicide films over control and memory gate electrodes in semiconductor devices can lead to short-circuit faults due to the thin ONO film, resulting in reduced production yield and increased costs, while omitting these films increases resistance and decreases memory operation speed.
Innovation Solution
A semiconductor device structure where a metal silicide film is formed only over the control gate electrode, avoiding its formation at the end portion and nearby region of the memory gate electrode, and the memory gate electrode is formed with a lower height than the control gate electrode to prevent short-circuit faults and maintain low resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If metal silicide films are formed over both control gate electrode and memory gate electrode, then resistance is reduced and memory operation speed is increased, but short-circuit faults occur between the electrodes
Solution Approach 1:
The patent applies local quality by forming metal silicide films selectively only on the control gate electrode while deliberately excluding the memory gate electrode. This localized application of the conductive material optimizes resistance reduction in the control gate region without creating short-circuit risks between adjacent electrodes, thus resolving the contradiction between speed improvement and reliability maintenance.
2Reliability
If metal silicide films are omitted from gate electrodes, then short-circuit faults are prevented, but resistance increases and memory operation speed decreases
Solution Approach 1:
The patent implements local quality by applying metal silicide films selectively to specific regions (control gate electrode) while omitting them from other regions (memory gate electrode). This selective application maintains reliability by preventing short-circuits in critical areas while still achieving resistance reduction and speed improvement in areas where the films are applied.
3Use of energy by moving object
If the ONO film thickness is reduced to decrease program and erase voltages, then voltage requirements are lowered, but short-circuit risk between adjacent gates increases
Solution Approach 1:
The patent applies local quality by forming metal silicide films selectively on the control gate electrode while excluding the memory gate electrode. This selective metallization compensates for the reduced insulation provided by the thin ONO film, maintaining adequate electrical isolation between adjacent gates while still benefiting from the lower voltage requirements enabled by the thin insulator.
Solution Approach 2:
The patent uses the selective metal silicide film formation as an intermediary measure to manage the trade-off between thin ONO film benefits and short-circuit risks. By strategically placing conductive material only where needed, the invention mediates between the conflicting requirements of low voltage operation and reliable electrical isolation.
Data Source
AI summary
Provided is a semiconductor device having, over a semiconductor substrate, a control gate electrode and a memory gate electrode which are adjacent to each other and constitute a nonvolatile memory. The height of the memory gate electrode is lower than the height of the control gate electrode. A metal silicide film is formed over the upper surface of the control gate electrode, but not formed over the upper surface of the memory gate electrode. The memory gate electrode has, over the upper surface thereof, a sidewall insulating film made of silicon oxide. This sidewall insulating film is formed in the same step as that for the formation of respective sidewall insulating films over the sidewalls of the memory gate electrode and the control gate electrode. The present invention makes it possible to improve the production yield and performance of the semiconductor device having a nonvolatile memory.