Substrate Processing with Backside Laser Alignment Marks
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Solution Overview
Problem
Current methods for processing substrates, such as semiconductor wafers, face challenges in achieving accurate and efficient cutting along division lines without compromising the quality of devices on the surface, particularly due to issues like front side and back side chipping and degradation of die strength, especially when a backside layer is present.
Innovation Solution
A method involving the attachment of a protective sheeting to the substrate's surface, where a laser beam forms alignment marks on the sheeting to guide the cutting process from the opposite side, allowing for precise alignment and reduction of division line width, thereby enhancing production efficiency and minimizing material waste.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the substrate is cut from the front side where division lines are formed, then alignment of cutting means is greatly facilitated, but the quality of devices may be affected by chipping and degradation of die strength
Solution Approach 1:
The patent applies inversion by cutting the substrate from the back side instead of the front side. This reverses the conventional cutting approach, allowing the cutting means to remove substrate material from the back surface while the division lines remain on the front side for alignment reference. This resolves the contradiction by maintaining alignment accuracy through front-side division lines while preventing device damage through back-side cutting.
Solution Approach 2:
The patent segments the substrate processing into distinct functions: the front side retains division lines for alignment purposes, while the back side performs the actual cutting operation. This segmentation allows each side to serve its optimal function without interfering with the other, resolving the conflict between alignment requirements and device protection.
2Reliability
If the substrate is cut from the back side to avoid chipping, then device quality is preserved, but alignment accuracy is significantly reduced
Solution Approach 1:
The patent maintains the inverted approach of back-side cutting while keeping front-side division lines visible for alignment. This allows the cutting operation to occur on the back side (preserving device quality) while the division lines on the front side continue to provide accurate alignment references for the cutting means.
Solution Approach 2:
The division lines on the front side serve as an intermediary reference system that mediates between the back-side cutting operation and the alignment requirements. The cutting means can align to these front-side division lines while actually cutting from the back side, resolving the alignment accuracy issue.
3Measurement precision
If division lines are widened to compensate for reduced alignment accuracy, then positioning tolerances are increased, but the number of devices that can be accommodated is reduced
Solution Approach 1:
By inverting the cutting approach to back-side cutting with front-side alignment references, the patent maintains high alignment accuracy without needing to widen division lines. This preserves the substrate area available for devices while providing sufficient positioning tolerances through accurate alignment to the narrow division lines.
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 ensures accurate and efficient substrate processing by preventing surface integrity compromise, reducing chipping and degradation, and allowing for a higher density of devices on the substrate, particularly beneficial for expensive materials like SiC and GaAs.
Implementation Method 1
applying a laser beam to the protective sheeting so as to form a plurality of alignment marks in the protective sheeting
Data Source
AI summary
A substrate having a first surface with at least one division line and an opposite second surface is processed by attaching a protective sheeting to the first surface and applying a laser beam to the protective sheeting to form a plurality of alignment marks in the protective sheeting. The substrate has a backside layer on the second surface. A laser beam is applied to the substrate from the side of the first surface. The substrate is transparent to the laser beam and the focal point of the laser beam is located inside the substrate which is closer to the second surface than to the first surface, to form a plurality of alignment marks in the backside layer. Substrate material is removed along the division line from the side of the second surface. The alignment marks are used for aligning the substrate material removing means relative to the division line.