Laser Reflow of Wafer Conductive Elements Without Carrier Substrates
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Solution Overview
Problem
Conventional semiconductor device fabrication methods require costly and potentially damaging carrier substrates for reflowing electrically conductive elements, which can cause deformation and electrical short circuits, and involve inefficient bulk furnace reflow processes.
Innovation Solution
The method involves supporting semiconductor wafers on a film frame instead of a carrier substrate, using a laser to direct localized energy for reflowing electrically conductive elements, eliminating the need for bulk furnace reflow and reducing damage risks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If bulk furnace reflow is used to reflow electrically conductive elements, then the entire wafer surface is heated uniformly, but this causes deformation of conductive elements and potential electrical short circuits
Solution Approach 1:
The patent applies localized heating only to the specific regions containing conductive elements rather than uniform bulk heating of the entire wafer. This selective thermal treatment reflows solder balls or conductive pillars without subjecting the entire wafer structure to high temperatures, thereby preventing deformation and electrical short circuits while achieving the desired reflow effect.
Solution Approach 2:
The heating process is segmented into discrete localized zones corresponding to individual conductive elements or small groups of elements. Rather than treating the wafer as a single bulk object, the system divides the thermal treatment into multiple independent heating spots, allowing precise control over which areas receive thermal energy and for how long.
2Reliability
If carrier substrates are used to support wafers during reflow processing, then wafer stability is improved, but this increases processing costs and introduces potential damage from carrier removal
Solution Approach 1:
The patent extracts and eliminates the carrier substrate from the processing system entirely. By using localized heating that can be applied directly to the wafer surface without requiring carrier support, the method removes the intermediate carrier component, thereby reducing processing costs, simplifying the manufacturing workflow, and eliminating potential damage associated with carrier attachment and removal operations.
Solution Approach 2:
The wafer is processed in a self-supported manner during localized reflow, utilizing its own structural integrity to maintain stability during the heating process. The localized heating method is applied such that the wafer can withstand the thermal treatment without requiring external carrier support, enabling direct processing that reduces overall system complexity.
3Productivity
If conventional bulk furnace reflow is used, then all conductive elements on the wafer are treated simultaneously, but this increases thermal exposure time and reduces processing efficiency
Solution Approach 1:
The reflow process is segmented into multiple rapid, localized heating cycles that can be applied sequentially to different regions of the wafer. Instead of heating the entire wafer uniformly for a prolonged period, the system divides the wafer into multiple zones and applies brief, intense thermal pulses to each zone, significantly reducing the total thermal exposure time while maintaining effective reflow of all conductive elements.
Solution Approach 2:
The localized heating is applied in periodic pulses to different regions of the wafer rather than continuous bulk heating. The system moves through the wafer surface in a systematic pattern, applying short-duration thermal pulses to each location and then moving to the next, creating a periodic action that achieves complete reflow much faster than conventional continuous heating methods.
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 costs, minimizes damage to conductive elements, and enhances yield by allowing precise, efficient reflow of conductive elements without the need for carrier substrates, improving product quality and reducing thermal exposure times.
Implementation Method 1
apparatus for generating a laser beam in the infrared or visible green spectrum
Implementation Method 2
using a laser to direct localized energy for reflowing electrically conductive elements
Implementation Method 3
An infrared temperature sensor may be configured to measure a temperature of a surface during irradiation by the laser beam
Data Source
AI summary
Methods of reflowing electrically conductive elements on a wafer may involve directing a laser beam toward a region of a surface of a wafer supported on a film of a film frame to reflow at least one electrically conductive element on the surface of the wafer. In some embodiments, the wafer may be detached from a carrier substrate and be secured to the film frame before laser reflow. Apparatus for performing the methods, and methods of repairing previously reflowed conductive elements on a wafer are also disclosed.