Work Function Metal Undercut Control via Polymer Brush Protection
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Solution Overview
Problem
Conventional lateral etch processes limit the minimum distance between n-type and p-type nanosheet devices in semiconductor manufacturing, restricting device density due to excessive work function metal (WFM) removal requirements.
Innovation Solution
A method involving the formation of a polymer brush layer to prevent lateral removal of WFM portions between nanosheet devices, using an organic planarization layer to protect certain WFM regions and selectively removing WFM layers, allowing for narrower WFM regions and reduced distance between devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional lateral etch processes are used to remove work function metal layers, then WFM layers can be removed, but excessive WFM removal occurs between nanosheet devices requiring compensation and limiting minimum device spacing
Solution Approach 1:
A polymer brush layer is introduced as an intermediary protective coating on the work function metal layers between nanosheet devices. This polymer brush layer selectively prevents lateral etch removal of WFM in the regions between devices while allowing complete removal of WFM from the nanosheet device regions, thereby eliminating the need for compensation and enabling tighter device spacing
Solution Approach 2:
The etch protection is applied locally only to specific regions between nanosheet devices through the polymer brush layer. This creates different etch resistance properties in different spatial locations: protected regions between devices versus unprotected regions on devices, achieving precise spatial control over WFM removal
2Ease of manufacture
If extensive over-etching is performed to remove WFM layers between nanosheets, then WFM removal is achieved, but the minimum distance between n-type and p-type nanosheet devices is limited
Solution Approach 1:
The polymer brush layer serves as a protective intermediary that enables extensive over-etching to be performed without damaging the WFM layers between devices. The polymer brush remains intact during etching, allowing complete WFM removal from device regions while preserving WFM in inter-device regions, thus reducing the minimum required distance between devices
3Productivity
If WFM layers are removed to increase device density, then more devices can be packed, but lateral etch causes unwanted WFM removal between devices
Solution Approach 1:
The polymer brush layer acts as a protective intermediary that enables aggressive lateral etching processes to be used for increasing device density. The polymer brush selectively shields WFM layers between devices from etch damage while allowing complete WFM removal from device regions, thereby enabling higher device density without compromising WFM layer integrity
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 narrower WFM regions and reduced distance between nanosheet devices, increasing device density without the need for excessive WFM removal compensation, thereby enhancing semiconductor device packing efficiency.
Implementation Method 1
a polymer brush layer is formed on exposed portions of the work function metal layers and the high-k dielectric layers
Implementation Method 2
The polymer brush layer prevents removal of the work function metal portions in between the nanosheet devices
Implementation Method 3
The OPL covers the second nanosheet device and a first part of the work function metal layer in the space between the first and second nanosheet devices
Implementation Method 4
the first plurality of work function metal layers is selectively removed from the first region with respect to the polymer brush layer
Data Source
AI summary
A method for manufacturing a semiconductor device includes forming a first nanosheet device and forming a second nanosheet device spaced apart from the first nanosheet device in respective first and second regions corresponding to first and second types. The first and second nanosheet devices respectively include a first and a second plurality of work function metal layers, and a work function metal layer extends from the first and second plurality of work function metal layers in the space between the nanosheet devices. In the method, part of the work function metal layer is removed from the space between the nanosheet devices, and the removed part of the work function metal layer is replaced with a polymer brush layer. The first plurality of work function metal layers is selectively removed from the first region with respect to the polymer brush layer.