In today’s highly competitive markets, it is imperative for a manufacturing fab to perform with a high capability to adapt to the latest technologies, while being flexible to change part mix to meet dynamic market demands and at the same time achieve a high throughput to maximize productivity. The ability for a fab to adjust in this multi-part, mixed technology environment requires advanced control mechanisms to ensure that the correct control settings are used for each wafer processed. These circumstances are compelling fabs globally to gain the ability to introduce a multitude of parts with the correct control settings without having to relearn before processing. In this paper the concept of controller state is explored to address these issues by studying mechanisms to predict post-event settings. The concept of inheritance is explored to expand the controller state capability to predict optimized process settings across parts and tools. This paper explores the development and implementation of these mechanisms at Infineon Technologies, Richmond to reduce send-ahead (SAHD) and rework events. The benefits of controller state to handle tool events and part introductions are illustrated using events such as scheduled preventive maintenance, hardware upgrades, porting parts across tools and reintroduction of low runner parts back into production.
This study characterizes the process influence on the alignment signal of deep trench (DT) process, and correlates product overlay with alignment results based on volume production data. The affecting processes include various steps of polysilicon thickness, nitride and oxide films, recess etch depth control, and resist thickness impact. Correlation also proves that the alignment signal plays an important role at the resulted long-term overlay stability. In order to improve the signal strength, further study focuses on the alignment optimization through mark design for deep trench process. The alignment marks evaluated include Scribe-lane Primary Marks (SPM) with difference process segmentations, short SPM marks and Versatile SPM marks. A good correlation is established between varying trench width or line width of mark segmentation and alignment signal strength. Comparison is also done for the signal strength between SPM mark and SSPM marks, between standard SPM mark and pure higher order marks.
Alignment performance and overlay control of metal layer from W-CMP process highly depends on the process influence on the alignment mark. While in a manufacturing environment, there could be introduced many changes into W-CMP process for defect reduction, cost reduction and yield improvement to further guarantee our success in this highly competitive industry. This study characterizes the CMP effect, especially erosion and dishing effect, polishing selectivity on alignment mark profile, which results in different alignment performance. We illustrate that how we seek solution to achieve an optimal alignment performance with the existing mark in according to different CMP slurry process by further fine tuning W-CMP process, such as over-polishing, final polish. The CMP effect on different alignment mark types is also evaluated; future alignment mark selection and design based on future CMP process, film deposition can thus be proposed. This work explains a good working method of optimizing alignment for process, fine tuning process for alignment mark, feed-backing solutions for mark selection while taking into considerations of cost, throughput, defect, yield.
Overlay control of printed layers onto processed metal levels highly depends on the process influences to the alignment and overlay measurement targets. This study characterizes the systematic influence to both alignment and overlay metrology based on AlCu deposition and W CMP. The systematic influence of AlCu deposition to alignment and overlay targets are explored in theory and then verified experimentally. Both theory and experimental results are then validated empirically as “non-zero” overlay control is applied to high volume production to increase wafer edge yield. The influence of W CMP on lot-to-lot overlay performance is also characterized and accounted for to further improve metal one overlay performance.
The emphasis of this paper will be model-based Advanced Process Control (APC). Methods used to characterize process influence on overlay for a back-end metal process will be discussed. We will then describe how predictive overlay was modeled in terms of AlCu deposition target life, W CMP endpoint as well as normal control context such as exposure tool and part id. The challenge of implementing APC for increased context partitioning is discussed and the need for a model-based approach is stressed. The methodology used for lot disposition in the case of “non-zero” targeted overlay is also explained.
This study is to establish the relationship of lens heating (LH) performance with related process variables and develop the methodology for reducing LH induced focus drift for different products based on ASML LH algorithms and experiment data. Focus drift data is collected at certain LH machine constants for different process settings, such as different clear window images (CLW) in stepper jobs, different exposure doses, reticle transmission rates, and substrates. The further study is done at different illumination settings to establish the correlation between NA/sigma settings, focus drift and LH scaling factors ((mu) <SUB>1</SUB> (mu) <SUB>2</SUB>). The characteristic (mu) <SUB>1</SUB>, (mu) <SUB>2</SUB> -- NA/Ill relationship for this i-line stepper is generated using production batches. LH machine constants are fine-tuned based on the Poly layer for 0.30 micrometer Logic Mix-mode, 0.30 micrometer SRAM and 0.35 micrometer Embedded SRAM products. This work provides an accurate and practical way to fine-tune LH for all the i-line/DUV steppers based on the critical layer of representative products in a foundry fab.
A robust characterization procedure of the focus drift during the lens heating effect is introduced. Through the optimized lens heating factors, we could keep the better wafer image control when exposure. Result in better critical dimension uniformity across wafer and across one field. This paper will present a detailed optimization procedure for lens heating and the benefit to fix the edge and alterative yield loss. There are several methods to characterize the total focus drift during exposure and how to keep the best focus of the image to the center of the focal plan deviation to get the more better image printing control. These methods including the image sensor scan, measurement the alignment offset of the focal mark, exposure-defocus window and CD measurement. The focus drift could be exactly compensated base on the different saturated data and keep the BF in the center of the FPD.