Self-Aligned Contact Formation with Reduced Step Height
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Solution Overview
Problem
The self-alignment process in semiconductor manufacturing introduces step height issues between poly gates and poly contacts, which reduces the chemical mechanical polishing (CMP) process window and leads to bridge issues.
Innovation Solution
A method is developed to form a semiconductor device with reduced step height by forming gates, buffer layers, and insulating layers, using strip-shaped photoresist patterns for self-aligned etching, followed by CMP processes to ensure the gate and conductive contact layers have the same height, thereby addressing step height issues and improving the CMP process window.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a self-alignment process is used to form contacts, then alignment precision is improved, but step height between poly gate and poly contact increases
Solution Approach 1:
The patent segments the contact formation process into multiple etching stages with different masks. First, a self-aligned etch creates initial contact holes with precise alignment to the gate. Then, a second etch completes the contact hole formation. This segmentation allows the self-alignment benefit to be captured while mitigating the step height issue through controlled etching depth at each stage.
Solution Approach 2:
The patent applies a preliminary etching step using the gate and strip-shaped photoresist patterns as masks before completing the contact hole formation. This preliminary action creates a controlled etch profile that reduces the final step height between the poly gate and poly contact, while still maintaining the alignment precision benefits of self-alignment.
2Manufacturing precision
If step height between poly gate and poly contact is reduced, then CMP process window is improved, but manufacturing complexity increases
Solution Approach 1:
The patent changes the etching parameters and sequence to control step height. By adjusting the etch depth, mask patterns, and etching chemistry in the preliminary etch step, the process achieves reduced step height that improves the CMP process window. The additional process steps are offset by the relaxation of CMP process constraints.
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 method effectively reduces step height between poly gates and poly contacts, enhancing the CMP process window and addressing bridge issues, thus improving the fabrication tolerances and efficiency in semiconductor manufacturing.
Implementation Method 1
performing a first chemical mechanical polish (CMP) process to the conductive contact layer removing the buffer layer; and performing a second chemical mechanical polish (CMP) process to the conductive contact layer
Data Source
AI summary
A method for forming a contact of a semiconductor device with reduced step height is disclosed, comprising forming a plurality of gates, forming a buffer layer on each of the gates, forming an insulating layer to fill spaces between the gates, forming strip-shaped photoresist patterns which cross the gates, etching the insulating layer to form first openings using a self-aligning process with the gates and the strip-shaped photoresist patterns as a mask, forming a conductive contact layer to fill the first openings, performing a first chemical mechanical polish (CMP) process to the conductive contact layer, removing the buffer layer, and forming a second chemical mechanical polish (CMP) process to the conductive contact layer.