Copper Interconnection Thermal Stabilization
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Solution Overview
Problem
In semiconductor devices with copper interconnections, the formation of hillocks and voids due to thermal and mechanical stress hinders high-speed operation and reliability, as copper interconnections are prone to oxidation and resistivity increases, affecting the performance of metal interconnections.
Innovation Solution
A method involving thermal treatments at different temperatures to stabilize copper layers, followed by forming an anti-oxidation layer at a specific temperature to prevent oxidation and reduce stress, which includes a first thermal treatment for stabilization, a second thermal treatment to apply stress, and a planarization process to form copper interconnections, with the anti-oxidation layer formed at a temperature equal to or higher than the second thermal treatment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If copper is used as interconnection material to reduce resistivity and improve conductivity, then electrical performance is improved, but the copper becomes prone to oxidation and hillock formation
Solution Approach 1:
A barrier layer comprising TiN and WN is introduced as an intermediary between the copper interconnection and the environment. The TiN layer (50-100 nm) and WN layer (50-100 nm) act as protective mediators that prevent copper oxidation while maintaining electrical conductivity. This barrier layer structure resolves the contradiction by providing chemical protection without significantly impeding electrical performance.
2Stability of the object's composition
If copper layer is thermally treated to stabilize the structure, then structural stability is improved, but thermal stress causes hillock formation
Solution Approach 1:
The patent applies preliminary anti-action by performing thermal treatment at a controlled temperature range (200-400°C) before copper interconnection formation to pre-stabilize the copper layer structure. This preliminary stabilization reduces subsequent thermal stress that would otherwise cause hillock formation during later processing steps. The barrier layer is also formed in advance to prevent oxidation before hillocks can develop.
Solution Approach 2:
The patent controls the temperature parameter during thermal treatment within a specific range (200-400°C) to achieve stable copper crystal structure without excessive thermal stress. By optimizing this parameter, the patent prevents hillock formation while maintaining structural stability. The barrier layer thickness parameters (TiN: 50-100 nm, WN: 50-100 nm) are also controlled to balance protection and stress management.
3Reliability
If multiple thermal treatment steps are performed to prevent oxidation and stabilize copper, then reliability is improved, but process complexity increases
Solution Approach 1:
The patent merges the oxidation protection function and thermal stabilization function into a single integrated barrier layer structure comprising TiN and WN layers. This combined structure performs multiple functions simultaneously: preventing copper oxidation, managing thermal stress, and providing mechanical support. By merging these functions into one barrier layer system, the patent reduces process complexity compared to applying separate protective layers and treatment steps.
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 method effectively inhibits the formation of hillocks and voids, enhancing the reliability and performance of copper interconnections by reducing thermal and mechanical stress, thereby improving the characteristics of semiconductor devices, particularly in MIM capacitors.
Implementation Method 1
thermally treating the copper layer at a first temperature; thermally treating the copper layer at a second temperature
Implementation Method 2
thermal and mechanical stress hinders high-speed operation
Implementation Method 3
forming an anti-oxidation layer on the copper interconnection at a third temperature
Data Source
AI summary
A metal interconnection method of a semiconductor device includes forming a copper layer on a semiconductor substrate and planarizing the copper layer. Two thermal treatments are performed at different temperatures between formation of the copper layer and planarization of the copper layer.