High Resistivity Substrate Bottom Surface Ion Implantation
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Solution Overview
Problem
High resistivity substrates such as silicon carbide and gallium arsenide are difficult to process using electrostatic chucks due to weak clamping forces, leading to potential damage and contamination issues, as they do not generate sufficient electrostatic clamping forces and struggle with charge dissipation.
Innovation Solution
A method involving the implantation of resistivity-reducing species into the bottom surface of high resistivity substrates to create a low resistivity layer, allowing for effective electrostatic clamping, which includes applying a coating, flipping the substrate, and performing ion implantation to reduce the substrate's resistivity, enabling secure clamping to an electrostatic chuck.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If electrostatic clamping is used on high resistivity substrates, then contamination and damage are reduced, but clamping force is insufficient
Solution Approach 1:
The patent applies local quality by creating a low resistivity layer only at the bottom surface of the high resistivity substrate through ion implantation. This localized modification allows the substrate to maintain its high resistivity bulk properties while having a conductive surface layer that enables effective electrostatic clamping to the chuck.
Solution Approach 2:
The patent changes the electrical resistivity parameter of the substrate bottom surface from high resistivity to low resistivity through ion implantation of species such as phosphorus, boron, or silicon. This parameter change enables the substrate to work effectively with electrostatic chucks while maintaining the high resistivity properties needed for device processing in the substrate bulk.
2Reliability
If ion implantation is performed on high resistivity substrates, then electrostatic clamping is enabled, but additional fabrication processes are introduced
Solution Approach 1:
The patent merges the ion implantation step with existing fabrication processes. The ion implantation is performed using the same ion implantation equipment and process infrastructure already present in semiconductor manufacturing, combining a new function (enabling electrostatic clamping) with existing process capabilities rather than requiring separate dedicated equipment or processes.
Solution Approach 2:
The ion implantation process serves multiple functions: it creates the low resistivity layer for electrostatic clamping, and simultaneously can serve as part of the doping process for device formation. This multi-functionality reduces the need for additional separate fabrication steps.
3Force
If mechanical clamping is used, then substrate is securely held, but contamination and damage occur
Solution Approach 1:
The patent replaces the mechanical clamping system with an electrostatic clamping system. Instead of using mechanical fingers or edges to physically contact and hold the substrate, the system uses electrostatic forces generated by the electrostatic chuck to clamp the substrate, eliminating mechanical contact points that could cause contamination or damage.
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 enables secure electrostatic clamping of high resistivity substrates, reduces the risk of damage, and allows for efficient processing without introducing additional fabrication steps, improving throughput and reducing the risk of contamination.
Implementation Method 1
Electrostatic forces may be used to clamp the substrate to the chuck. Electric fields are created within the chuck. These electric fields cause electrons in the substrate to be drawn to the bottom surface of the substrate, where they are attracted to positive charges in the chuck. This attraction serves to clamp the substrate to the chuck.
Implementation Method 2
The ions are then implanted into the exposed bottom surface to create the low resistivity layer.
Data Source
AI summary
A method of modifying a high-resistivity substrate so that the substrate may be electrostatically clamped to a chuck is disclosed. The bottom surface is implanted with a resistivity-reducing species. In this way, resistivity of the bottom surface of the substrate may be greatly reduced. In some embodiments, to implant the bottom surface, a coating is applied to the top surface. After application of the coating, the substrate is flipped so that the front surface contacts the top surface of the chuck. The ions are then implanted into the exposed bottom surface to create the low resistivity layer. The resistivity of the low resistivity layer proximate the bottom surface after implant may be less than 1000 ohm-cm. Once the bottom surface has been implanted, the substrate may be processed conventionally. The low resistivity layer may later be removed by wafer backside thinning processes.