Etch Stop Layer Breakthrough for Protected FinFET Contact Etching
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Solution Overview
Problem
In semiconductor manufacturing, particularly for FinFETs, there is a challenge in efficiently forming contacts while protecting metal features and dielectric layers, as existing methods often require removing photo mask layers, which can lead to damage during subsequent etching processes.
Innovation Solution
A process where a photo mask layer is left in place to protect dielectric layers and embedded metal features, using selective etchants to break through etch stop layers without removing the mask, allowing for precise patterning and protection of sensitive areas during etching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the photo mask layer is removed before etching the etch stop layer, then the etching process can proceed without mask interference, but the dielectric layer and embedded metal features become vulnerable to damage
Solution Approach 1:
The patent uses a sacrificial etch stop layer as an intermediary that absorbs the etching action, protecting the underlying dielectric layer and metal features. The etch stop layer is specifically designed to be etched by the selected etchant while the other layers remain protected, thus mediating between the etching process and the sensitive structures.
Solution Approach 2:
The patent changes the chemical parameters of the etching process by selecting an etchant that is highly selective to the etch stop layer material. This parameter change allows the etching to proceed efficiently through the etch stop layer while automatically stopping at the protected layers, resolving the contradiction between etching efficiency and damage prevention.
2Manufacturing precision
If a separate etching process is used to break through the etch stop layer, then precise control over etching depth is achieved, but the process complexity and time increase
Solution Approach 1:
The patent incorporates the etch stop layer breaking function into the existing dielectric layer etching process. By designing the etch stop layer with specific etch selectivity, the breaking action is achieved as a preliminary result of the main etching process, eliminating the need for a completely separate etching step while maintaining precision control.
Solution Approach 2:
The etching process is designed to serve multiple functions simultaneously: removing the dielectric layer, breaking through the etch stop layer, and exposing the underlying structures. This multi-functionality reduces process complexity while maintaining the precision benefits of controlled etching depth.
3Reliability
If the photo mask layer is left in place during etch stop layer etching, then protection of dielectric layer and metal features is maintained, but the etching process may be hindered by mask presence
Solution Approach 1:
The patent applies local quality by making the etch stop layer have different etch resistance properties compared to the dielectric layer. The etch stop layer is specifically engineered to be vulnerable to the selected etchant, creating a localized weakness that allows etching to proceed through it while the mask-protected areas remain intact.
Solution Approach 2:
The patent converts the potential harm of mask presence (which could interfere with etching) into a benefit by using the mask to define precise etching boundaries. The mask's protective effect is transformed into a precision tool that enables controlled etching through the etch stop layer only in desired locations.
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 the formation of contacts with reduced risk of damage to dielectric layers and metal features, improving the reliability and precision of contact formation in semiconductor devices.
Implementation Method 1
The etchant used to etch the dielectric layer is selective to the dielectric layer such that the etch rate with respect to the dielectric layer is greater than the etch rate with respect to the etch stop layer
Implementation Method 2
A separate etchant is then used to break through the etch stop layer. This next etchant is selective to the etch stop layer and will not significantly etch the dielectric layer
Data Source
AI summary
A photo resist layer is used to protect a dielectric layer and conductive elements embedded in the dielectric layer when patterning an etch stop layer underlying the dielectric layer. The photo resist layer may further be used to etch another dielectric layer underlying the etch stop layer, where etching the next dielectric layer exposes a contact, such as a gate contact. The bottom layer can be used to protect the conductive elements embedded in the dielectric layer from a wet etchant used to etch the etch stop layer.