Self-Aligned Buried Layer Fabrication via Oxide Masking
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Solution Overview
Problem
Traditional semiconductor buried layer fabrication processes are costly and prone to crystal defects, leading to prolonged development cycles and suboptimal electrical performance in integrated circuits.
Innovation Solution
A method involving a substrate with a first oxide layer, a first buried layer region with differential doping, and a self-alignment process using a second oxide layer as a mask, which reduces photolithography steps and avoids compressive stress, thereby simplifying the process and minimizing crystal defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional photolithography process is used to form buried layer with different impurity types, then selective implanting can be achieved, but the process complexity and cost increase due to requiring photolithography twice
Solution Approach 1:
The oxide layer automatically forms different thicknesses in different regions based on the doping concentration differences, serving as its own mask for the second ion implantation. The highly doped region forms a thicker oxide layer that blocks implantation, while the lightly doped region forms a thinner oxide layer that allows implantation, eliminating the need for additional photolithography steps.
Solution Approach 2:
The invention utilizes changes in oxide layer thickness as a function of underlying doping concentration. By controlling the oxidation process parameters and utilizing the relationship between doping concentration and oxide growth rate, the process creates self-aligned regions with different oxide thicknesses that automatically guide subsequent ion implantation.
2Manufacturing precision
If LPSIN layer is used as hard mask for self alignment implanting, then alignment precision is improved, but crystal defects increase due to compressive stress on substrate
Solution Approach 1:
The invention replaces the LPSIN hard mask with a naturally formed oxide layer that serves as a temporary mask during ion implantation. This oxide layer is easily removed afterward and does not introduce the compressive stress problems associated with LPSIN layers, effectively using a disposable masking approach without the harmful side effects.
Solution Approach 2:
The oxide layer acts as an intermediary between the substrate and the ion implantation process. It provides the necessary masking function for self-alignment while being compatible with the substrate, avoiding the direct contact and stress issues that arise when using LPSIN layers as masks.
3Reliability
If thick oxide layer is grown as mask for buried layer formation, then masking effectiveness is improved, but process time increases due to prolonged oxidation
Solution Approach 1:
The invention creates oxide layers with different thicknesses in different regions of the substrate, tailored to the specific requirements of each region. The highly doped regions form thicker oxide layers for effective masking, while other regions form thinner oxide layers, optimizing both masking effectiveness and process efficiency without requiring uniformly thick oxide layers across the entire substrate.
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 reduces process complexity and cost while minimizing crystal defects, enhancing the electrical performance of semiconductor devices by optimizing the buried layer formation.
Implementation Method 1
forming a thick oxide layer 12 on the substrate 11 by thermal oxidation process
Implementation Method 2
forming the first buried layer 16 in the substrate through ion implanting by using the oxide layer 12 as a mask layer
Data Source
AI summary
The present disclosure provides a semiconductor device and a method for fabricating a semiconductor buried layer. The method includes: preparing a substrate which includes a first oxide layer; forming a first buried layer region in the surface of the substrate by using a photoresist layer with a first buried layer region pattern as a mask, in which a doping state of the first buried layer region is different from a doping state of other region of the substrate; forming a second oxide layer on the surface of the substrate and the first buried layer region; and forming a second buried layer region in the surface of the substrate through self alignment process by using the second oxide layer as a mask. The method disclosed by the present disclosure reduces the complexity of the buried layer procedures and the cost thereof, as well as the probability of crystal defects.