Aggressive line width control requirements for leading edge IC fabrication necessitate integration of novel techniques such as DoseMapper into the lithography process flow. DoseMapper is based on the simple concept that CD uniformity (CDU) can be improved through compensation of CD errors by using the scanner actuators. Specifically, the DoseMapper system allows for compensation of interfield and intrafield CD non-uniformity, based on the spatial distribution of in-line CD measurements or end-of-line electrical parameters for a stable process. This approach is supported by the fact that small variations of linewidth are correlated to exposure dose in a linear fashion. In this work we describe strategies for and results of the application of DoseMapper in a lithographic process for gate layer in a 65nm technology. We will highlight the potential strengths and weaknesses of various DoseMapper strategies to. For instance, we have learned that dose adjustments which are based on post-etch CD signature can lead to degradation of the lithography-based process window especially for 2 -dimensional features due to high MEEF. Therefore, it is asserted that application of DoseMapper in a high-volume manufacturing process requires consideration of such rational tradeoffs as mentioned above. Impact of Mask CD variation on DoseMapper effectiveness will also be discussed. This has the potential to have a significant impact on manufacturability of photo masks for the 65nm node and beyond
Mask CD resolution and uniformity requirements for back end of line (BEOL) layers for the 90nm Technology Node push the capability of I-line mask writers; yet, do not require the capability offered by more expensive 50KeV ebeam mask writers. This suite of mask layers seems to be a perfect match for the capabilities of the DUV mask writing tools, which offer a lower cost option to the 50KeV platforms.
This paper will evaluate both the mask and wafer results from all three platforms of mask writers (50KeV VSB,ETEC Alta 4300TM DUV laser and ETEC Alta 3500TM I-line laser) for a Cypress 90nm node Metal 1 layer, and demonstrate the benefits of the DUV platform with no change to OPC for this layer.
The development of 100-nm design rule technologies is currently taking place in many R&D facilities across the world. For some critical alyers, the transition to 193-nm resist technology has been required to meet this leading edge design rule. As with previous technology node transitions, the materials and processes available are undergoing changes and improvements as vendors encounter and solve problems. The initial implementation of the 193-nm resits process did not meet the photolithography requirements of some IC manufacturers due to very high Post Exposure Bake temperature sensitivity and consequently high wafer to wafer CD variation. The photoresist vendors have been working to improve the performance of the 193-nm resists to meet their customer's requirements. Characterization of these new resists needs to be carried out prior to implementation in the R&D line. Initial results on the second-generation resists evaluated at Cypress Semicondcutor showed better CD control compared to the aelrier resist with comparable Depth of Focus (DOF), Exposure Latitute, Etch Resistance, etc. In addition to the standard lithography parameters, resist characterization needs to include defect density studies. It was found that the new resists process with the best CD control, resulted in the introduction of orders of magnitude higher yield limiting defects at Gate, Contact adn Local Interconnect. The defect data were shared with the resists vendor and within days of the discovery the resist vendor was able to pinpoint the source of the problem. The fix was confirmed and the new resists were successfully released to production. By including defect monitoring into the resist qualification process, Cypress Semiconductor was able to 1) drive correction actions earlier resulting in faster ramp and 2) eliminate potential yield loss. We will discuss in this paper how to apply the Micro Photo Cell Monitoring methodology for defect monitoring in the photolithogprhay module and the qualification of 193nm resist processes.
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