Backside CMP Marker Layer With Carbon-Boron Diffusion Control
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Solution Overview
Problem
Determining the optimal stopping point for chemical-mechanical planarization (CMP) process to achieve the desired thickness for backside power delivery networks in semiconductor devices is non-trivial, leading to potential yield degradation due to increased parasitic capacitance or etch stop layer etching.
Innovation Solution
A method involving the formation of a CMP marker layer using a boron-rich layer sandwiched by ion implants to control the CMP process, with carbon ions suppressing boron diffusion, ensuring consistent thickness control during thinning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the workpiece is thinned to achieve desired thickness for backside power delivery network, then parasitic capacitance is reduced and device performance is improved, but determining the stopping point becomes non-trivial leading to yield degradation
Solution Approach 1:
A CMP marker layer is formed at the desired final thickness depth before the CMP process begins. This marker layer serves as a pre-positioned indicator that will be exposed when the CMP process reaches the target depth, eliminating the need for complex real-time monitoring and making the stopping point easily identifiable.
Solution Approach 2:
The CMP marker layer acts as an intermediary between the CMP process and the stopping criterion. Instead of directly measuring thickness during CMP or relying on complex process control, the marker layer provides a visual or detectable signal (such as a color change or contrast difference) that indicates when the target depth is reached, simplifying the control mechanism.
2Productivity
If the workpiece is thinned too much, then backside power delivery network is achieved, but etch stop layer may be etched resulting in yield degradation
Solution Approach 1:
The CMP marker layer is positioned at the exact depth where the CMP process should stop, before the thinning begins. This pre-positioned marker provides a clear visual indication to prevent over-thinning and etching of the etch stop layer, ensuring the process stops at the optimal point.
Solution Approach 2:
The CMP marker layer provides real-time visual feedback during the CMP process. When the marker layer is exposed, it signals that the target depth has been reached, allowing operators to stop the CMP process immediately to prevent further thinning that could expose the etch stop layer.
3Manufacturing precision
If CMP process is slowed by adding CMP marker layer, then thickness control is improved, but additional implantation steps are required increasing process complexity
Solution Approach 1:
The formation of the CMP marker layer is merged with the existing ion implantation process used for creating the backside power delivery network. The marker layer is formed by implanting ions (such as boron) at a specific depth, combining the marker layer creation with the doping process rather than adding a separate deposition step.
Solution Approach 2:
The ion implantation process serves multiple functions: it creates the backside power delivery network by doping the substrate and simultaneously forms the CMP marker layer at the desired depth. This multi-functionality eliminates the need for separate marker layer formation steps, reducing overall process complexity despite the added precision capability.
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 allows for precise control of workpiece thickness, reducing variability and improving yield and device performance by slowing the CMP process effectively.
Implementation Method 1
To minimize the diffusion of boron in this boron-rich layer, the boron-rich layer is sandwiched by implants of a first species of ions, where this first species of ions serves to slow the diffusion of the boron. In certain embodiments, carbon is used as the first species of ions.
Data Source
AI summary
A method of processing a workpiece that will include a backside power delivery network is disclosed. The method includes forming a CMP marker layer in the workpiece at the depth to which the workpiece is to be thinned. This CMP marker layer, which may be a boron-rich layer, serves to slow the chemical-mechanical planarization (CMP) process. To minimize the diffusion of boron in this boron-rich layer, the boron-rich layer is sandwiched by implants of a first species of ions, where this first species of ions serves to slow the diffusion of the boron. In certain embodiments, carbon is used as the first species of ions.