Cooled Cleaving Implant Microbubble Control
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Solution Overview
Problem
The existing substrate cleaving process using ion implantation results in microbubbles that undergo Ostwald ripening, leading to increased surface roughness and the need for costly polishing steps due to uncontrolled microbubble size and diffusion during temperature increases, compromising the uniformity of silicon surfaces.
Innovation Solution
Implementing a method that controls the size of microbubbles in substrates by using a cooled ion implanter with backside gas cooling to maintain the substrate temperature between -150°C and 30°C during implantation, reducing the stability size of microbubbles and preventing diffusion, thereby minimizing surface roughness after cleavage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the substrate temperature is increased during implantation, then the implantation process can proceed, but Ostwald ripening occurs causing microbubble size to increase and surface roughness to worsen
Solution Approach 1:
The patent changes the temperature parameter from conventional high temperature to low temperature (below 50°C, preferably below 30°C, more preferably below 20°C) during ion implantation. This parameter change prevents Ostwald ripening by maintaining conditions where smaller microbubbles remain stable, thereby controlling microbubble size distribution and reducing surface roughness after cleavage while still enabling the implantation process to proceed
Solution Approach 2:
The patent applies preliminary cooling to the substrate before and during ion implantation to prevent Ostwald ripening before it can occur. By maintaining low temperature throughout the implantation process, the patent preemptively counteracts the thermodynamic tendency for larger microbubbles to grow at the expense of smaller ones, thus preventing surface roughness degradation before it happens
2Ease of manufacture
If conventional ion implantation is used without temperature control, then the process is simpler, but microbubble size is uncontrolled leading to increased surface roughness
Solution Approach 1:
The patent introduces temperature as a controlled parameter during ion implantation, changing it from an uncontrolled variable to a precisely managed condition. By maintaining substrate temperature below 50°C (preferably below 30°C or 20°C), the patent achieves control over microbubble nucleation and growth, ensuring uniform microbubble size distribution and smooth surfaces after cleavage
Solution Approach 2:
The patent implements temperature monitoring and control during the ion implantation process. By measuring the substrate temperature and adjusting cooling conditions to maintain temperature below critical thresholds, the patent creates a feedback loop that ensures microbubble size remains controlled throughout the implantation process, preventing Ostwald ripening while maintaining process simplicity
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 the mean void diameter of microbubbles from approximately 10 nm to 5 nm to 7 nm, eliminating the need for extensive polishing and ensuring a smoother surface, thus improving the substrate cleaving process and reducing the cost associated with surface preparation for device manufacture.
Implementation Method 1
backside gas cooling to maintain the substrate temperature between -150°C and 30°C during implantation
Implementation Method 2
Implantation of an ion species may allow a substrate to be cleaved. The species form microbubbles in the substrate material
Implementation Method 3
Ostwald ripening is a thermodynamic process where larger particles grow by drawing material from smaller particles because larger particles are more stable than smaller particles
Implementation Method 4
atoms or molecules on the surface of smaller, less stable particles will diffuse and add to the surface of the larger, more stable particles
Data Source
AI summary
A substrate is implanted with a species to form a layer of microbubbles in the substrate. The species may be hydrogen or helium in some embodiments. The size at which the microbubbles are stable within the substrate is controlled. In one example, this is by cooling the substrate. In one embodiment, the substrate is cooled to approximately between −150° C. and 30° C. This cooling also may reduce diffusion of the species in the substrate and will reduce surface roughness when the substrate is cleaved along the layer of microbubbles.