Nanometer-Scale Metal Recessing via Cyclic Oxidation and Etching
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Solution Overview
Problem
In the semiconductor manufacturing process, achieving precise control over the etching of metal layers with accuracy in the range of nanometers or smaller is challenging, particularly in the back end of line (BEOL) process where fine metal interconnections and vias need to be formed with high accuracy.
Innovation Solution
A substrate processing method involving the formation of a metal oxide layer using an oxidizing fluid, followed by selective removal with an etchant, allowing for precise control of the etching amount by alternating between these steps to achieve accurate recessing of metal layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional wet etching is used to remove metal layer surface portions, then the metal layer can be etched, but the etching accuracy cannot be controlled within nanometer scale
Solution Approach 1:
The etching process is segmented into multiple cycles, where each cycle consists of oxidation followed by selective removal. This segmentation allows precise control of etching depth by controlling the number of cycles, achieving nanometer-scale accuracy that cannot be obtained through conventional single-step wet etching.
Solution Approach 2:
An oxide layer is introduced as an intermediary substance between the metal layer and the etchant. The oxide layer forms uniformly on the metal surface through oxidation, and its thickness can be precisely controlled. The etchant then selectively removes only this oxide layer, enabling precise control of metal layer removal depth at nanometer scale.
2Manufacturing precision
If the etching amount is increased to achieve desired recess depth, then the via can be formed, but the distance control between via and interconnection becomes inaccurate
Solution Approach 1:
The process uses feedback control where the oxide layer thickness (which directly determines etching depth) is controlled by parameters such as oxidation time, temperature, and oxidizing atmosphere composition. By monitoring and adjusting these parameters, the final via depth and distance to interconnection can be precisely controlled within nanometer accuracy.
Solution Approach 2:
The oxide layer formation is performed as a preliminary action before etching. The oxide layer thickness is predetermined by controlling oxidation conditions, which in turn determines the exact amount of metal that will be removed in the subsequent etching step. This preliminary control enables accurate prediction and achievement of the desired via-to-interconnection distance.
3Manufacturing precision
If multiple etching steps are performed to achieve precise control, then the etching accuracy improves, but the process complexity increases
Solution Approach 1:
Multiple etching operations are merged into a single integrated process sequence where oxidation and etching are alternately performed in a controlled cycle. This merging achieves the precision of multiple separate etching steps while reducing overall process complexity through systematic integration and automation of the cyclic process.
Solution Approach 2:
The etching process employs periodic action through cyclic repetition of oxidation followed by selective removal. Each cycle removes a controlled amount of metal (one atomic layer or several atomic layers), and by repeating the cycle a predetermined number of times, the total etching depth is precisely controlled. This periodic approach simplifies process control compared to continuously adjusting multiple independent etching parameters.
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 enables precise control of the etching amount with nanometer-scale accuracy, ensuring minimal distance between interconnections and maintaining the integrity of the metal layer, thereby improving the manufacturing process efficiency.
Implementation Method 1
forming a metal oxide layer formed of one atomic layer or several atomic layers on a surface layer of the metal layer by supplying an oxidizing fluid to the surface of the substrate
Implementation Method 2
selectively removing the metal oxide layer from the surface of the substrate by supplying an etchant to the surface of the substrate
Data Source
AI summary
A substrate processing method which processes a substrate having a metal layer on a surface thereof includes a metal oxide layer forming step of forming a metal oxide layer formed of one atomic layer or several atomic layers on a surface layer of the metal layer by supplying an oxidizing fluid to the surface of the substrate, and a metal oxide layer removing step of selectively removing the metal oxide layer from the surface of the substrate by supplying an etchant to the surface of the substrate.