Golden Ratio Dummy Structures for CMP Planarity
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Solution Overview
Problem
Chemical mechanical polishing (CMP) processes in semiconductor manufacturing face challenges with dishing and erosion due to non-uniform distribution of metal structures, which can lead to operational failures and planarity issues, necessitating the use of dummy structures to achieve uniform density.
Innovation Solution
A method is introduced to determine and fill selected portions of a die with dummy structures using a grid pattern and the golden ratio, ensuring uniform distribution and minimizing dishing and erosion during CMP by forming these structures in accordance with the golden ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If dummy structures are added to achieve uniform density distribution, then CMP process uniformity improves, but device complexity increases
Solution Approach 1:
The die surface is divided into a grid of cells, and dummy structures are selectively placed in specific cells to achieve uniform density. This segmentation approach transforms the complex problem of dummy structure placement into a systematic grid-based solution, where each cell can be independently evaluated and filled according to the golden ratio algorithm.
Solution Approach 2:
The patent applies the golden ratio (approximately 1.618) as a mathematical parameter to determine the spacing and distribution of dummy structures. By using this specific ratio between consecutive dummy structures, the method achieves optimal uniformity in density distribution across the die, resolving the contradiction between adding dummy structures and maintaining simplicity.
2Reliability
If dummy structures are placed uniformly across the die, then erosion and dishing are reduced, but manufacturing complexity increases
Solution Approach 1:
The method calculates and determines the optimal positions of dummy structures before the actual manufacturing process. By pre-determining the grid pattern and applying the golden ratio to identify specific fill locations, the complex placement strategy is established in advance, simplifying the actual manufacturing execution while achieving the desired erosion and dishing reduction.
Solution Approach 2:
The patent uses a standardized grid pattern that can be replicated across different dies and metal layers. This copying approach allows the same proven golden ratio-based distribution method to be applied universally, reducing manufacturing complexity by avoiding custom designs for each case while maintaining reliability improvements.
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 method significantly reduces dishing and erosion, enhancing the planarity and reliability of semiconductor devices by maintaining uniformity across the wafer and improving the CMP process outcomes.
Implementation Method 1
CMP takes advantage of cooperative effects of both physical and chemical forces acting on the surface of the wafer
Implementation Method 2
Hydrogen peroxide is often used as the slurry to remove copper, because hydrogen peroxide reacts with the copper form a soft layer that increases the removal rate
Implementation Method 3
an abrasive chemical solution, called a slurry, passes between the pad and the wafer
Data Source
AI summary
A method of forming dummy structures in accordance with the golden ratio to reduce dishing and erosion during a chemical mechanical polish. The method includes determining at least one unfilled portion of a die prior to a chemical mechanical planarization and filling the at least one unfilled portion with a plurality of dummy structures, a ratio of the dummy structures to a total area of the unfilled portion being in the range of 36 percent and 39 percent. A die formed in accordance with the method may include a plurality of metal levels and a plurality of regions at each metal level, each region having a plurality of dummy structures formed as golden rectangles.