It is often difficult to know when a photoresist problem is affecting the productivity of a 300mm PVD system. Even small amounts of residual resist, when introduced over a prolonged period, can reduce yields, cause particle contamination or slowly contaminate process chambers, thereby requiring premature kit changes. Major photoresist hits can be very costly, upwards of hundreds of thousands of dollars for lost wafers, especialy if the tantalum/copper target becomes contaminated.
Resist can be inadvertently introduced to PVD systems in a number of ways. Rushing Hot Lots through opens the door to skipping steps like the resist strip or even the complete etch and strip cycle. This could result in contamination throughout the process tool if the wafer is not stopped at the degas chamber. Such process flow errors can impact PVD tool performance, immediately, from a single wafer. More common, however, is the incomplete removal of resist. This can happen due to a poorly controlled end point in the asher such as from first-wafer, cold-chamber effects, or from faults on integrated etch/strip tools.
Each of these mechanisms can leave resist contamination on wafers which eventually is seen as a loss of die or high particle densities in sputter etch process chambers. Resist contamination can be the cause of a series of factors, all of Installation Schematic which work to reduce tool availability, increase COO, and decrease the overall yield of a process flow.
The 300mm Resist-Torr®
The 300mm Resist-Torr consist of an optimum combination of a closed ion source quadrupole mass analyser with fast response capilary inlet, together with advanced proprietary algorithms developed exclusively for the degas chambers on industry leading 300mm PVD cluster tools. When utilised with the powerful features of Process Eye™ sensor control software package, the result is completely automated operation and highly reliable photoresist detection. Unscheduled downtimes are reduced and device yields are improved.
The 300mm Resist-Torr considers many different parameters of the degas step and combines that data provide information in the form of a meaningful number, without the need for user-interpretation. This measurement, termed the PR Index®, is a normalised measure of wafer borne photoresist contamination that can be presented in various forms to compare data over time. The 300mm Resist-Tor can interrupt the processing of any wafer automatically, without operator intervention, if a wafer enters the vacuum system with detrimental levels of residual photoresist, as determined by the PR Index.Click the picture for a closer lookBenefits
• Fully automated process monitoring – no operator necessary
• Detection of photoresist contamination during high pressure (~8 Torr) degas, before wafers enter into 300mm PVD chambers
• Calculation of the PR Index® - a measure of photoresist contamination level in the degas chamber
- WARN and STOP levels for photoresist contamination
- Can stop the progress of a contaminated wafer through the tool
- Sensitive enough to detect even smal amounts of resist commonly found on product wafers
- Increase die yield asociated with reduced particle contamination
• Built in calibration standard with automatic calibration routine enables long-term data comparison and proper system operation
• Variable alarm sensitivity to match the conditions of your product in your fab or process tool
• Powerful optional data review feature to maximise ROI
- Faster PM recovery through vacuum analysis helps minimise chamber turnaround time
- Highlights chronic, low-level residual photoresist contamination that can cause reduced PreClean kit-life and excess particles
- Reports of gases and PR Index for comparisons, as well as for long term trend analysis