Phase-Change Memory Bottom Electrode Polishing Control
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Solution Overview
Problem
In the manufacturing of phase-change random access memory, it is challenging to accurately control the chemical mechanical polishing process to prevent excessive loss of the bottom electrode, as the polishing time is difficult to manage due to uneven thickness of the insulating material layer and the relative thinness of the bottom electrode.
Innovation Solution
A stop layer with specific materials such as amorphous carbon, Al2O3, SiCNH, TiO2, HfO2, Ta2O5, or SiN is deposited above the bottom electrode to divide the chemical mechanical polishing process into two stages, allowing precise control of polishing time and preventing over-removal of the vertical portion of the bottom electrode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a single chemical mechanical polishing process is used to remove the upper horizontal portion of the bottom electrode, then the process is simple and fast, but it is difficult to accurately control the polishing time to prevent over-removal of the vertical portion of the bottom electrode
Solution Approach 1:
The single polishing process is divided into two separate polishing processes: a first polishing process that polishes the insulating material layer, and a second polishing process that polishes the bottom electrode. This segmentation allows each process to be optimized and controlled independently, solving the contradiction between efficiency and precision control.
Solution Approach 2:
The first polishing process is performed as a preliminary action to remove the insulating material layer before the second polishing process removes the upper horizontal portion of the bottom electrode. This preliminary action prepares the surface and establishes a clear stopping point, enabling precise control in the subsequent polishing step.
2Reliability
If the insulating material layer is made thicker to ensure complete coverage, then the coverage and insulation are improved, but the polishing time increases and makes precise control more difficult
Solution Approach 1:
The polishing process is segmented into two distinct steps, with the first step dedicated to removing the insulating material layer. This allows the insulating layer to be sufficiently thick for reliable coverage without excessively increasing total polishing time, as the second polishing step efficiently removes the remaining material.
Solution Approach 2:
The first polishing process acts as an intermediary step that prepares the surface by removing the insulating material layer, creating a transition state that facilitates precise control in the second polishing process. This intermediary action mediates between the need for thick insulation and the need for fast, controllable polishing.
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 approach enables precise control of the polishing process, reducing unnecessary loss of the bottom electrode and ensuring accurate planarization, thereby enhancing the manufacturing efficiency of semiconductor devices.
Implementation Method 1
performing a first chemical mechanical polishing until the stop layer is exposed; and thereafter performing a second chemical mechanical polishing to remove the upper horizontal portion of the bottom electrode
Data Source
AI summary
This invention discloses a semiconductor device and its manufacturing method. According to the method, a stop layer is deposited on a step-shaped bottom electrode, and then a first insulating layer is deposited through a high aspect ratio process. A first chemical mechanical polishing is performed until the stop layer. A second chemical mechanical polishing is then performed to remove the upper horizontal portion of the bottom electrode. Then, a phase-change material can be formed on the vertical portion of the bottom electrode to form a phase-change element. Through arranging a stop layer, the chemical mechanical polishing process is divided into two stages. Thus, during the second chemical mechanical polishing process preformed on the bottom electrode, polishing process can be precisely controlled to avoid the unnecessary loss of the bottom electrode.