Semiconductor Alignment Keys With Deep Trenches Under Thick Films
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Solution Overview
Problem
In semiconductor manufacturing, the original alignment marks are often obscured by thicker light-absorbing layers, leading to inadequate alignment during exposure and increased production costs due to the use of zero masks.
Innovation Solution
A method is developed to form alignment keys by defining voltage regions on a substrate, creating trenches and oxide portions through photoresist layers and ion implantation, eliminating the need for a traditional zero mask, thereby enhancing alignment depth and reducing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If thicker light absorbing layers are used to cover alignment marks, then film coverage is improved, but alignment depth becomes insufficient
Solution Approach 1:
The patent performs preliminary oxidation to form oxide portions in the substrate before depositing the light absorbing layer. These pre-formed oxide portions create alignment keys with sufficient depth even when covered by thick light absorbing layers, enabling the thick film coverage to be achieved without compromising alignment functionality.
2Manufacturing precision
If zero mask is used to form alignment marks, then alignment mark formation is achieved, but production cost increases
Solution Approach 1:
The patent makes the substrate serve itself by forming oxide portions directly within the substrate that act as alignment keys. This eliminates the need for external zero masks to create alignment marks, as the substrate's own oxidized regions provide the necessary alignment features, thereby reducing production costs while maintaining alignment precision.
3Manufacturing precision
If original alignment marks are formed by zero mask, then alignment marks are created, but both cost and alignment effectiveness deteriorate
Solution Approach 1:
The patent extracts the alignment mark formation process from the substrate surface and relocates it into the substrate bulk by forming oxide portions within the substrate. This extraction eliminates the need for zero masks and their associated costs, while the subsurface oxide portions provide effective alignment keys that are not obscured by overlying film layers.
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 improves wafer quality by providing deeper alignment keys that effectively guide subsequent exposure processes without the need for costly zero masks, ensuring better alignment and reduced production expenses.
Implementation Method 1
performing an oxidation process on the exposed part of the substrate in the groove to form an oxide portion on a part of the substrate
Implementation Method 2
using the second patterned photoresist layer as a mask to perform a first ion implantation on the medium voltage region and the low voltage region
Data Source
AI summary
A method for forming alignment keys of a semiconductor structure includes: forming an oxide pad layer and a passivation layer on a substrate; forming a patterned photoresist layer on the passivation layer, and using the patterned photoresist layer as a mask to remove part of the oxide pad layer and passivation layer and expose the substrate surface in the medium voltage and alignment mark regions; forming oxide portions on the exposed substrate surface, and the oxide portions extending into the first depth of the substrate; forming deep doped wells in the low voltage and medium voltage regions; thinning the oxide portions; forming high-voltage doped wells in the high voltage and alignment mark regions; performing an etching process on the high voltage and alignment mark regions to form a second trench, as an alignment key, having a second depth greater than the first depth in the alignment mark region.