Room Temperature Ionic Liquid Contact Etchback for Ruthenium
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Solution Overview
Problem
The semiconductor industry faces challenges in reducing contact resistance and preventing oxide formation during the etching of contact features in integrated circuits, particularly with metals like ruthenium, which can lead to contamination and increased complexity due to the volatility and toxicity of ruthenium oxide.
Innovation Solution
The use of a room temperature ionic liquid to recess contact features without forming metal oxides, combined with optional techniques such as ligand addition and anodic oxidation, reduces contact resistance and eliminates the need for additional toxic gas treatment equipment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional etching methods are used to reduce contact resistance, then contact resistance is lowered, but metal oxide formation occurs leading to contamination and increased device complexity
Solution Approach 1:
The patent changes the chemical parameters of the etching environment by using ionic liquids with specific compositions (containing anions like PF6-, BF4-, Tf2N- and cations like imidazolium, pyridinium, ammonium) instead of conventional aqueous or organic etchants. This parameter change enables etching of ruthenium and other metals without forming volatile oxides, thus reducing contamination while maintaining low contact resistance
Solution Approach 2:
The ionic liquid acts as an intermediary substance that facilitates the etching process without producing harmful byproducts. The specific ionic liquid composition mediates between the etching requirement (to reduce contact resistance) and the contamination prevention requirement (to avoid oxide formation), enabling both goals to be achieved simultaneously
2Object-generated harmful factors
If ruthenium oxide formation is prevented, then contamination is reduced, but additional toxic gas treatment equipment is required
Solution Approach 1:
The patent converts the harmful aspect of ruthenium etching (oxide formation requiring complex treatment equipment) into a beneficial process by using ionic liquids that prevent oxide formation altogether. The ionic liquid etching process transforms a potentially harmful volatile oxide byproduct into a non-volatile ionic complex that remains in the liquid phase, eliminating the need for complex gas treatment equipment
3Manufacturing precision
If etching precision is improved, then contact feature dimensions are controlled better, but process complexity increases
Solution Approach 1:
The patent achieves improved etching precision by changing the physical and chemical parameters of the etchant to ionic liquids with controlled viscosity, conductivity, and chemical composition. These parameter changes enable precise control over etching rate and selectivity, achieving better dimensional control of contact features while maintaining relatively simple process steps
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 effectively lowers contact resistance, reduces oxide formation, and facilitates the recycling of ruthenium, improving process yield and safety by avoiding volatile and toxic byproducts.
Implementation Method 1
recessing the contact using an etchant solution comprising a room temperature ionic liquid, wherein material forming the contact is soluble in the room temperature ionic liquid
Implementation Method 2
optional techniques such as ligand addition
Data Source
AI summary
The present disclosure provides an integrated circuit with an interconnect structure and a method for forming the integrated circuit. In one embodiment, a method of the present disclosure includes receiving a workpiece that includes a first recess in a dielectric layer over the workpiece, depositing a contact fill in the first recess and over the dielectric layer to form a contact feature, planarizing a top surface of the workpiece to remove the contact fill over the dielectric layer, depositing an interlayer dielectric layer over the planarized top surface of the workpiece, forming a second recess in the interlayer dielectric layer to expose the contact fill in the dielectric layer, recessing the contact fill by soaking the workpiece in a room temperature ionic liquid, and depositing a conductive layer over the recessed contact fill. The material forming the contact fill is soluble in the room temperature ionic liquid.