Self-Aligned Deep Implantation Using Sacrificial Fillers
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Solution Overview
Problem
In semiconductor manufacturing, deep implantation processes face challenges with high aspect ratio openings in implantation masks, leading to tapered profiles that reduce the effectiveness of dopant implantation and increase costs due to the need for thicker masks and multiple photolithography steps, which can result in defects and inefficiencies as feature sizes decrease.
Innovation Solution
A method for self-aligned deep implantation that uses a thick oxide hardmask with a high aspect ratio, followed by a sacrificial filler material and etch stop layer to control dopant implantation, allowing for precise placement of dopants without the need for a second photomask, thereby reducing tapering and overlay margin issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional dry etch techniques are used to create high aspect ratio openings in implantation masks, then the mask thickness can be increased to prevent unwanted doping, but the openings develop a tapered profile that reduces implantation mask effectiveness
Solution Approach 1:
A sacrificial filler material is deposited into the high aspect ratio opening before the implantation mask is formed. This preliminary action provides structural support during the etching process, enabling the formation of vertical-walled openings without tapering. The filler material is later removed after serving its temporary structural purpose.
Solution Approach 2:
The sacrificial filler material acts as an intermediary element that temporarily occupies the high aspect ratio opening space. It serves as a placeholder that maintains the opening geometry during mask formation and is subsequently removed, having fulfilled its mediating function of enabling vertical profile formation.
2Manufacturing precision
If multiple photolithography exposure operations are used to create deep implantation features, then the overlay margin increases to account for alignment errors, but this limits the reduction of feature sizes
Solution Approach 1:
The method combines the formation of high aspect ratio openings and implantation mask patterns into a single photolithography exposure operation. By using the sacrificial filler material to define the opening geometry, the implantation mask can be directly patterned in the same step, eliminating the need for separate exposure operations and their associated overlay margins.
Solution Approach 2:
The sacrificial filler material serves multiple functions: it defines the opening geometry, provides structural support during etching, and acts as a self-aligned reference for subsequent mask formation. This self-service approach eliminates the need for separate alignment operations and reduces dependency on overlay accuracy between multiple photolithography steps.
3Length of moving object
If higher implantation energy is applied to implant dopants in smaller surface areas, then deep implantation is achieved, but a thicker implantation mask is required which increases the aspect ratio and reduces mask effectiveness
Solution Approach 1:
The sacrificial filler material is deposited into the opening before the implantation mask is formed, providing pre-structured support that enables the formation of vertical-walled openings. This preliminary structuring allows for thinner, more effective implantation masks that maintain their blocking capability even at higher aspect ratios, enabling deep implantation without proportionally increasing mask thickness.
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 more accurate and efficient deep implantation with reduced tapering and costs, allowing for smaller critical dimensions and improved semiconductor device area utilization, while maintaining electrical properties without defects.
Implementation Method 1
deep implantation uses a higher implantation energy to drive the dopants deeper into the surface area
Data Source
AI summary
Methods of forming self-aligned patterns for performing oppositely doped deep implantations in a semiconductor substrate are disclosed. The semiconductor substrate has implantation and non-implantation regions. The methods include forming a hardmask pattern for a first implantation with a first conductivity-type dopant, depositing an etch stop layer, filling trenches between the hardmask pattern with a sacrificial filler material having a higher wet etch resistance than the hardmask, removing a top portion of the sacrificial filler material and the etch stop layer over a top surface of the hardmask pattern, removing the hardmask pattern in the implantation region by wet etching, and performing a second ion implantation with a second conductivity type dopant opposite of the first conductivity type.