Backside Contact Formation Using Ion-Implanted Etch Stop Layers
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Solution Overview
Problem
The challenge in forming backside contacts in semiconductor devices is the mis-alignment and difficulty in controlling the depth of trench placeholders, leading to process and performance variations in backside power distributed networks.
Innovation Solution
A method involving forming a trench in a stack of alternating layers, implanting an etch stop layer, creating a recess, filling it with a temporary material, and depositing source/drain and metal materials to form a backside contact, while using ion implantation and selective etching to control the process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If trench placeholders are used to solve mis-alignment issue, then mis-alignment is reduced, but the depth control becomes difficult leading to process variations
Solution Approach 1:
The patent replaces the mechanical placeholder structure with an ion-implanted etch stop layer. Instead of relying on physical placeholder depth control, the invention uses ion implantation to create a precise etch stop layer at a controlled depth, substituting mechanical depth control with a chemically-defined etch resistance boundary that provides both alignment precision and process consistency.
Solution Approach 2:
The invention changes the parameter of depth control from mechanical (placeholder physical depth) to chemical/physical (ion implantation depth and etch selectivity). By controlling ion implantation energy and dose, and utilizing etch selectivity between the implanted region and surrounding material, the etch stop layer depth is precisely controlled without the variability inherent in mechanical placeholder fabrication.
2Manufacturing precision
If ion implantation is used to form etch stop layer, then etch rate control is improved, but process complexity increases
Solution Approach 1:
The ion implantation step serves multiple functions: it creates the etch stop layer for depth control, provides doping of the semiconductor material, and defines the contact trench boundary. This multi-functionality reduces overall process complexity despite adding the ion implantation step, as it consolidates what would otherwise require separate processing steps.
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 enhances the precision and consistency of backside contact formation, reducing mis-alignment issues and improving process reliability in semiconductor devices.
Implementation Method 1
implanting the bottom of the trench to form an etch stop layer within the base layer
Implementation Method 2
forming a recess in the base layer by removing the base layer selective to the etch stop layer
Data Source
AI summary
Approaches of the disclosure relate to methods for forming self-aligned backside contacts in a semiconductor device. One method may include forming a trench in a stack of layers, wherein the stack of layers comprises a plurality of alternating first layers and second layers atop a base layer, and wherein the trench is defined by a set of sidewalls and a bottom extending between the set of sidewalls. The method may further include implanting the bottom of the trench to form an etch stop layer within the base layer, forming a recess in the base layer by removing the base layer selective to the etch stop layer, and filling the recess with a temporary material. The method may further include depositing a source/drain material within the trench, wherein the source/drain material is formed over the temporary material.