Nitridation Layer Self-Stop Etch for Copper Interconnects
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Solution Overview
Problem
The existing methods for forming metal interconnections in semiconductor devices using the single damascene process often result in over-etching or under-etching, leading to openings and voids in copper interconnections, which increase resistance and degrade device characteristics.
Innovation Solution
A method involving the deposition and annealing of a nitridation layer on a semiconductor substrate before forming a trench, which acts as a self-stop layer to prevent over-etching or under-etching, ensuring a constant trench depth and uniform resistance by using nitride films formed through primary annealing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single damascene process is used to form copper interconnection in a trench, then the device complexity is reduced compared to dual damascene process, but over-etching or under-etching occurs leading to openings and voids in copper interconnection
Solution Approach 1:
A nitridation layer is formed on the lower IMD film before etching the trench. This preliminary formation of the nitridation layer acts as a self-stop etch layer that prevents over-etching through the trench, ensuring precise trench depth control while maintaining the simplicity of the single damascene process
Solution Approach 2:
The nitridation layer serves as an intermediary layer between the lower IMD film and the etching process. It mediates the etching depth by providing a controlled stop point, preventing both over-etching and under-etching while allowing the trench to be formed to the correct depth for copper interconnection
2Manufacturing precision
If under-etching occurs when forming the trench, then the trench depth is insufficient, but openings occur in the copper interconnection increasing resistance
Solution Approach 1:
The nitridation layer is formed in advance on the lower IMD film before trench etching. This preliminary layer provides a self-stop mechanism during etching, ensuring the trench reaches the precise required depth without stopping prematurely, thus preventing openings in the copper interconnection
Solution Approach 2:
The nitridation layer provides a self-stop feedback mechanism during the etching process. When the etch reaches the nitridation layer, the etch rate automatically decreases or stops, providing real-time depth control that prevents both under-etching and over-etching, ensuring reliable copper interconnection formation
3Manufacturing precision
If over-etching occurs when forming the trench, then the trench depth exceeds the required depth, but excessive deposition of copper barrier metal film occurs creating overhang and voids
Solution Approach 1:
The nitridation layer is formed before trench etching as a protective preliminary layer. This layer acts as a self-stop etch barrier that prevents the etch from penetrating too deeply, eliminating the root cause of over-etching that would otherwise lead to copper barrier metal film overhang and void formation
Solution Approach 2:
The nitridation layer serves as a cushioning layer formed beforehand to absorb or stop the etching process at the appropriate depth. This prior cushioning prevents the etch from going too deep, thereby preventing the subsequent problems of excessive copper barrier metal deposition, overhang formation, and void creation
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach effectively prevents openings and voids in copper interconnections, achieving uniform resistance and minimizing dielectric constants of the nitride films, thereby enhancing the reliability and performance of metal interconnections in semiconductor devices.
Implementation Method 1
forming nitride films on the semiconductor substrate by primary annealing
Implementation Method 2
removing the nitride films using a chemical
Data Source
AI summary
A method for forming a metal interconnection of a semiconductor device avoids over-etching and under-etching through the use of the “self-stop” function of a nitridation layer, to prevent the occurrence of openings and voids in a copper interconnection and to obtain a constant trench depth. The method includes forming nitride films on a semiconductor substrate by primary annealing, the semiconductor substrate being provided with a first IMD film and a tungsten plug; depositing a second IMD film on the semiconductor substrate on which the nitride films are formed; depositing a photoresist on the second IMD film and patterning the photoresist; etching the second IMD film using the patterned photoresist to form a trench; removing the nitride films using a chemical; depositing a copper barrier metal film and a copper seed layer in the trench from which the nitride films are removed, and depositing copper; secondarily annealing the substrate on which the copper is deposited; and planarizing the secondarily annealed substrate by chemical-mechanical polishing.