Semiconductor Contact Pad Oxide Resistivity Reduction
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Solution Overview
Problem
In semiconductor devices, particularly DRAMs, the oxidation of tungsten contact pads by O3 gas used in forming metal oxide films as lower electrodes leads to increased electric resistivity, disrupting the continuity between the lower electrode and the pad, causing malfunction and yield reduction.
Innovation Solution
A semiconductor device structure and manufacturing method involving a contact pad with a three-layer structure, where the sacrifice film (second conductive film) is made of a metal like molybdenum, which forms a molybdenum dioxide oxide film with lower electric resistivity than tungsten dioxide, preventing oxidation of the tungsten conductive film and maintaining low pad resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If O3 gas is used to oxidize metal material for forming lower electrode, then the lower electrode can be formed with good step coverage and miniaturization capability, but the pad formed of tungsten is oxidized to increase electric resistivity, inhibiting electric continuity
Solution Approach 1:
A conductor layer comprising a first conductive film (tungsten pad) and a second conductive film (molybdenum) is introduced as an intermediary structure between the pad and lower electrode. The second conductive film is selectively oxidized to form an oxide film that serves as the lower electrode, while the first conductive film remains protected. This intermediary structure allows the oxidation process to proceed without damaging the pad's electric continuity.
Solution Approach 2:
The conductor layer is designed with different local properties: the first conductive film (tungsten) has high electric conductivity and is protected from oxidation, while the second conductive film (molybdenum) is selectively oxidized to form the lower electrode. This local differentiation of material properties and oxidation resistance enables simultaneous achievement of good step coverage and maintained electric continuity.
2Reliability
If a three-layer conductor structure with sacrifice film is used, then electric resistivity of contact pad is reduced and electric continuity is maintained, but device structure becomes more complex
Solution Approach 1:
The second conductive film (molybdenum) serves multiple functions: it acts as a protective layer during oxidation, forms the lower electrode through selective oxidation, and provides a transition layer between the pad and capacitive insulating film. This multi-functionality reduces the need for separate structural elements, thereby limiting the increase in device complexity.
Solution Approach 2:
The oxidation state of the conductor layer is changed as a key parameter: the second conductive film is selectively oxidized to form the oxide film (lower electrode), while the first conductive film remains in its metallic state. This parameter change (oxidation state) transforms the structure from a simple conductor to a functional lower electrode without requiring additional processing 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
The approach effectively reduces the electric resistivity of the contact pad, enhancing the electrical characteristics and yield of semiconductor devices by using a molybdenum dioxide oxide film with significantly lower resistivity than tungsten dioxide, thus preventing increased resistivity and malfunction.
Implementation Method 1
the oxide film of the second metal has a lower electric resistivity than an oxide film of the first metal
Implementation Method 2
O3 gas, which has high oxidizability, is used to oxidize a metal material
Data Source
AI summary
A semiconductor device comprises a conductor film and a capacitor comprising a lower electrode provided on the conductor film. The conductor film includes a first conductive film containing a first metal, a second conductive film containing a second metal on the first conductive film, and an oxide film of the second metal on the second conductive film. The oxide film of the second metal has a lower electric resistivity than an oxide film of the first metal.