Laser-Plasma Integrated IC Surface Exposure
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Solution Overview
Problem
Current methods for exposing integrated circuits by ablation of polymer envelopes are either too aggressive, damaging the silicon, or inefficient, requiring multiple steps and lengthy processes, such as mechanical or chemical thinning followed by plasma etching, which can damage the circuit or connections.
Innovation Solution
A method combining the application of laser radiation and plasma in the same enclosure to ablate the polymer envelope, allowing precise control and quick exposure of the integrated circuit surface, with the laser initially removing most of the polymer thickness and the plasma completing the removal of the residual layer under vacuum conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a high power laser beam is applied to the polymer envelope, then the ablation speed increases, but the silicon and circuit are attacked and deteriorated
Solution Approach 1:
The ablation process is divided into two distinct stages: first, a moderate power laser removes the bulk of the polymer envelope at a controlled rate; second, a plasma source completes the removal of residual polymer. This segmentation allows each method to operate within its optimal safety and efficiency parameters without causing damage to the underlying circuit.
Solution Approach 2:
The invention changes the operational parameters by introducing a plasma source with different energy characteristics compared to the laser. The plasma operates at lower power levels suitable for microelectronics, transforming the energy delivery mechanism from high-power laser ablation to controlled plasma etching for the final exposure stage.
2Reliability
If the laser is applied in a moderate manner to avoid damage, then the circuit integrity is preserved, but islands of polymer remain on the circuit
Solution Approach 1:
A plasma source is introduced as an intermediary tool to complete the ablation process. The plasma acts as a gentle finishing mechanism that can remove residual polymer islands without the aggressive energy delivery that would damage the circuit, thereby achieving complete exposure while maintaining circuit integrity.
Solution Approach 2:
The invention combines two different energy delivery systems (laser and plasma) into a composite processing approach. Each system contributes its strengths: the laser provides rapid bulk removal with controlled damage risk, while the plasma provides gentle complete removal, together achieving both speed and completeness.
3Reliability
If plasma is used to attack the polymer envelope, then the circuit is not damaged, but the ablation is very slow and only removes a very small thickness
Solution Approach 1:
The laser performs preliminary ablation to remove the majority of the polymer envelope thickness before the plasma source is applied. This preliminary action reduces the workload for the plasma, allowing it to complete the exposure quickly without being rate-limited, thereby achieving both safety and acceptable productivity.
Solution Approach 2:
The ablation task is segmented into two phases: high-speed bulk removal by laser and low-speed precision completion by plasma. This segmentation allows the system to leverage the high productivity of laser for the majority of the work while using plasma only for the final, safety-critical stage.
4Manufacturing precision
If mechanical or chemical methods are used to thin the polymer envelope, then the thickness is reduced, but additional handling steps are required increasing oxidation risk
Solution Approach 1:
The invention merges the thinning and exposure operations into a single integrated laser-plasma process that occurs in one enclosure without intermediate handling. The laser and plasma sources work sequentially on the same sample in situ, eliminating the need for separate mechanical or chemical thinning steps and their associated handling and oxidation risks.
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 rapid and precise exposure of integrated circuits with minimal risk of damage, maintaining the integrity of the circuit and connections, and allows for quick and easy stripping of the polymer envelope, reducing handling and oxidation risks.
Implementation Method 1
For the ablation of the polymer envelope, it is known to apply a high power laser beam to the polymer envelope and to scan the integrated circuit in order to cause the degradation of the envelope
Implementation Method 2
it comprises a combined application of laser radiation and plasma on the envelope initially covering the integrated circuit
Data Source
Figure 1
Figure 2
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AI summary
The invention relates to a method for exposing an integrated circuit by ablating the polymer coating initially covering the integrated circuit, characterised in that it comprises the combined application of a laser radiation and a plasma onto the coating initially covering the integrated circuit.