Memory Device Alignment via Nitrogen Plasma Cleaning
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Solution Overview
Problem
The manufacturing of integrated circuits faces challenges in accurately aligning patterns due to residues left in alignment mark trenches after planarization, which can affect subsequent alignment steps and reduce the yield of memory devices.
Innovation Solution
A nitrogen plasma step is performed to create a nitrogen-containing doped region on the dielectric layer, followed by the use of diluted hydrofluoric acid to remove residues in the alignment mark trenches, preventing damage to the surface and improving alignment accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If a planarization step is performed on the conductive layer, then the surface flatness is improved, but residues are left in the alignment mark trench affecting subsequent alignment
Solution Approach 1:
The patent performs a nitrogen plasma treatment before the cleaning step to modify the chemical composition of the dielectric layer surface. This preliminary action creates a nitrogen-containing doped region that enables selective removal of residues without damaging the dielectric layer in subsequent cleaning steps, thus resolving the contradiction between achieving surface flatness and maintaining alignment accuracy.
Solution Approach 2:
The patent changes the chemical parameters of the dielectric layer by introducing nitrogen through plasma treatment. This parameter change modifies the dielectric layer's composition to create a nitrogen-containing doped region, which allows for selective etching of residues while protecting the dielectric layer structure, thereby maintaining both surface flatness and alignment accuracy.
2Manufacturing precision
If diluted hydrofluoric acid is used to clean residues, then residues are removed, but the dielectric layer surface may be damaged
Solution Approach 1:
The nitrogen plasma treatment is performed as a preliminary action before cleaning with diluted hydrofluoric acid. This treatment modifies the dielectric layer surface by creating a nitrogen-containing doped region that is resistant to HF acid etching, while residues without nitrogen content are selectively removed. This preliminary modification protects the dielectric layer from damage during cleaning.
Solution Approach 2:
The nitrogen-containing doped region acts as an intermediary protective layer between the dielectric layer surface and the diluted hydrofluoric acid. This intermediary layer allows the cleaning agent to remove residues effectively while preventing the acid from damaging the underlying dielectric layer structure.
3Manufacturing precision
If alignment marks are used to assist alignment in exposure process, then alignment accuracy is improved, but process complexity increases
Solution Approach 1:
The dielectric layer serves multiple functions: it acts as both the structural layer requiring planarization and the source of alignment marks. By forming alignment mark trenches within the dielectric layer and using the dielectric layer itself as the alignment reference, the patent eliminates the need for separate alignment mark structures, thus maintaining alignment accuracy while reducing process complexity.
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 ensures complete removal of residues, enhancing the accuracy of subsequent alignment steps and increasing the yield of memory elements by protecting the dielectric layer from damage during cleaning.
Implementation Method 1
a nitrogen plasma step (N2 plasma) is performed on the dielectric layer
Implementation Method 2
uses diluted hydrofluoric acid to clean the residues while avoiding damaging the surface of the dielectric layer
Data Source
AI summary
A method for manufacturing a memory device is provided, the method includes the following steps: firstly, providing a dielectric layer, then simultaneously forming a contact window and an alignment mark trench in the dielectric layer, wherein the contact window exposes a lower metal line, then forming a conductive layer on the surface of the dielectric layer, in the contact window and in the alignment mark trench, performing a planarization step on the conductive layer, and leaving a residue in the alignment mark trench. Subsequently, a nitrogen plasma step (N2 plasma) is performed on the dielectric layer, a cleaning step is performed to remove the residue in the alignment mark trench, and a patterned magnetic tunneling junction, MTJ) film is laminated on the contact window.