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In this paper we demonstrate the feasibility of Negative Tone Development (NTD) process to pattern 22nm node contact holes leveraging freeform source and model based assist features. We demonstrate this combined technology with detailed simulation and wafer results. Analysis also includes further improvement achievable using a freeform source compared to a conventional standard source while keeping the mask optimization approaches the same. Similar studies are performed using the Positive Tone Development (PTD) process to demonstrate the benefits of the NTD process.

A strong demand exists for techniques that can further extend the application of ArF immersion lithography. Besides techniques like litho-friendly design, dual exposure or patterning schemes, customized illumination modes, also alternative processing schemes are viable candidates to reach this goal. One of the most promising alternative process flows uses image reversal by means of a negative tone development (NTD) step with a FUJIFILM solvent-based developer. Traditionally, the printing of contacts and trenches is done by using a dark field mask in combination with positive tone resist and positive tone development. With NTD, the same features can be printed in positive resist using a light field mask, and consequently with a much better image contrast. In this paper, we present an overview of applications for the NTD technique, both for trench and contact patterning, comparing the NTD performance to that of the traditional positive tone development (PTD). This experimental work was performed on an ASML Twinscan XT:1900i scanner at 1.35 NA, and targets the contact/metal layers of the 32 & 22 nm node. For contact hole printing, we consider both single and dual exposure schemes for regular arrays and 2D patterns. For trench printing, we compare the NTD and PTD performance for one-dimensional patterns, line ends and twodimensional structures. We also assess the etch capability and CDU performance of the NTD process. This experimental study proves the added value of the NTD scheme. For contacts and trenches, it allows achieving a broader pitch range and/or smaller litho targets, which makes this process flow attractive for the most advanced lithography applications, including double patterning.

Contact patterning for advanced lithography generations is increasingly being viewed as a major threat to the continuation of Moore's Law. There are no easy patterning strategies which enable dense through isolated contacts of very small size. Lack of isolated contact focus latitude, high dense contact mask error factor and incredibly low defectivity rate requirements are severe issues to overcome. These difficulties mean that new and complex patterning methods for contacts at the 90nm and 65nm device generations are being considered. One possible option for improving the process window of contact patterning is resist reflow. Resist reflow can supplement almost any other optical extension method for contact lithography. Previous results have shown the significant benefits of this method for CD control on semi-dense and isolated contact for the 100nm device generation. This work extends the previous work by investigating very dense pitch through isolated contact patterning at 193nm low K1 lithography regimes. The encouraging overall CD control and process window of reflowed contacts using the ARCH TIS2000 bilayer resist system is analyzed through pitch for different imaging options. An investigation of the capability of resist reflow in combination with optimized reticle and illumination for the 65nm device generation is also presented as are details of defectivity levels for reflowed contacts on 90nm device products.

A preponderance of critical levels for the 90-nanometer (nm) process technology node utilize 193 nm lithography. The resist systems used in this processing show a much higher sensitivity to line width slimming at the traditional electron beam energies encountered in Critical Dimension Scanning Electron Microscope (CD SEM) metrology than do previous generations of chemically amplified resists. The uncertainty that results from this undesirable interaction can consume more than the entire process control budget for advanced devices. This paper reports measurements of resist CD uniformity taken with a new CD SEM metrology technology based on ultra low voltage, that significantly reduces the impact of the electron beam on 193 nm resist systems. Over the past several months this technology has been used for 193 nm resist development studies at ARCH Chemicals. Several examples, demonstrating the effectiveness of this new technology using the Yosemite Ultra Low voltage CD SEM will be presented and contrasted against results obtained at higher voltages.

In this work, die-to-die CD-variations across a wafer are investigated as a potential important contribution to the global gate CD-control. Measuring the non-uniformity in different experiments using CD-SEM and ELM revealed different parameters, impacting the measured non-uniformity value. It will be pointed out that the measurement itself can have a significant contribution to the measured 3(sigma) -value, especially using CD-SEM, if the level in non-uniformity is low. Further on, it will be shown that the choice of resist and developer chemistry can have a high impact on the i-W CD non-uniformity. Moreover, the potential impact of exposure and track processing will be outlined, and an optimization methodology will be presented. Finally, it will be shown that gate process integration, in particular BARC- and POLY-etching, is increasing the i-W CD non-uniformity. This is affecting the ELM-results, despite the high precision and repeatability of these measurements. This ELM-variation, as well as the overall i-W CD non- uniformity should be taken into account when using ELM or CD-SEM as a metrology tool for process window characterization.

A strong demand exists for techniques that extend application of ArF immersion lithography. Besides techniques such as litho-friendly design, dual exposure/patterning schemes, customized illumination, alternative processing schemes are also viable candidates. One of the most promising alternative flows uses image reversal by means of a negative tone development (NTD) step with a Fujifilm solvent-based developer. Traditionally, contact and trench printing uses a dark-field mask in combination with positive tone resist and positive tone development. With NTD, the same features are printed in positive resist using light-field masks, and consequently with better image contrast. We present an overview of NTD applications, comparing the NTD performance to that of the traditional development. Experimental work is performed at a 1.35 numerical aperture, targeting the contact/metal layers of the 32- and 22-nm nodes. For contact printing, we consider both single- and dual-exposure schemes for regular arrays and 2-D patterns. For trench printing, we study 1-D, line end, and 2-D patterns. We also assess the etch capability and critical dimension uniformity performance of the NTD process. We proves the added value of NTD. It enables us to achieve a broader pitch range and/or smaller litho targets, which makes NTD attractive for the most advanced lithography applications, including double patterning.