Bumping 

Today's bumping processes create features in a wide variety of shapes, densities, quantities and materials. Collectively, they create the connections that drive device functionality, quality and yield.

Cu Pillar and Microbump

Shrinking feature size, combined with increased I/O count, drive bumping processes toward tighter pitch and smaller sizes.

Bumping processes are trending toward smaller features to enable tighter integration and more functionality. The inspection and metrology required to ensure process control needs to have the resolution and accuracy to provide meaningful results that are well within the process tolerance window. Rudolph's 3D bump option can measure features down to 1um tall with diameters less than 10um. Balance accuracy and throughput for Cu pillar, microbumps and ball-drop bumps all on a single platform.

Accuracy of the measurement drives all results including die-based coplanarity, average bump heights, individual bump heights and all subsequent analysis. Rudolph's Truebump Technology leverages multiple technologies to help ensure that thin films present on the wafer do not falsely increase or decrease the resulting bump heights being reported.

Coplanarity

Successful electrical connections between devices and packages rely on bumps that are coplanar.

Devices with bumps become integrated into final packages several different ways, but all of them require that bumps are consistently the same height within a specified tolerance--referred to as coplanarity. Having metrology in place that can quickly and accurately calculate the coplanarity for each and every device on a wafer is imperative for all downstream packaging steps. Having flexibility to define methodology for calculating coplanarity and demonstrating repeatability that is significantly less than process tolerance are important aspects to providing coplanarity results in an HVM environment. Failure to accurately determine coplanarity can result in failures after packaging or a loss of yield of good devices.

Rudolph offers fast 3D measurement results at any given resolution with accuracy that is appropriate for the largest bumps in HVM down to the smallest features being developed for tomorrow's bumping needs.

RDL and UBM

Metal thickness metrology

Bumping processes are enabled by redistribution layers and under bump metallization. The increasing complexity of the process as the bumps get smaller along with the tighter process window a is driving the need for more front-end like automated and sophisticated metrology systems in the back-end packaging. Fully automated metrology solutions capable of measuring the multi-layer metal thickness complement the bump co-planarity measurements are needed during process development as well as during failure analysis and quality control to provide feedback for in-process control as well as improving yield.

Rudolph provides solutions for integrated interferometric structure step-height metrology as well as options for on-product film-stack metrology using acoustic wave technology. These 3D measurements can be augmented with high resolution 2D metrology and inspection of the same features to help ensure that RDL is meeting requirements based on design rules and that there are no process excursions leading to electrical failures.

Data Management

Combining defect inspection and 2D/3D metrology data can be overwhelming and actually make process control unrealistic. As bump densities increase, RDL line spacing decreases and processes become more sophisticated, the amount of data needed to properly optimize yield is truly massive.

A single wafer will go through multiple process steps in the bumping process. RDL, UBM and bumping with potentially multi-million bumps per wafer will generate layers of defect and metrology data that can be a powerful tool when handled correctly and efficiently.

Rudolph's yield management software gives users the analytical tools to visualize data, correct process variation, and improve yields by easily analyzing multi-layer, multi-wafer and multi-lot results that include defect, 2D and 3D metrology data all in a single database with a single user interface. Furthermore, the initial results being generated on the inspection system can be used to automatically identify wafer level signatures, repeaters and previous layer defects which drive optimized defect capture profiles. Defect images are automatically classified by one of the most powerful ADC engine available in the semiconductor industry today. What's left is a small subset of data for an operator to review to help ensure that all data that goes into the database is fully classified for the most effective analysis. Wafers per hour will not matter if an operator still needs to classify results before an answer can be obtained.

Consulting and Applications Services

Rudolph's process control consulting services allow busy manufacturers to focus on production while we examine how to improve the process.

The Rudolph applications teams have over twenty years of experience with hundreds of successful projects worldwide across multiple industries. Contact us today to discuss your application study needs.

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