The capability and performance of the production-proven DUV ALTA 4300 system has been extended by the development of two new optical subsystems: a 0.9 NA, 42X reduction lens and a high-bandwidth acousto-optic deflector based beam position and intensity correction servo. The PSM overlay performance has been improved by modifications to the software algorithms. The enhanced performance, delivered by these subsystem improvements, has been introduced as a new product-the ALTA 4700. Characterization data show improved resolution performance in line end shortening, through pitch CD bias and feature corner acuity. The AOD subsystem reduces stripe beam placement errors and random and systematic beam intensity errors. This has enabled local CD uniformity to be reduced to 4.3 nm (3σ) and global CD uniformity to be reduced to 6 nm (3σ). Second layer overlay performance is now 20 nm (max error). This paper also demonstrates superior X-Architecture performance delivered by the ALTA 4700. Characterization data show global CD uniformity in 0°, 45°, 90°, and 135° orientations better than 6.5nm (3σ); mean CD control in all 4
orientations less than 3.6nm; and smooth angled lines through a wide range of angles. A split lot wafer evaluation demonstrates the equivalence of wafers produced DUV ALTA system reticles vs. those produced with reticles from a 50kV electron beam system. The evaluation shows the interchangeability of these two systems for 90nm Metal 1 applications-with no changes to the wafer OPC (originally optimized for the 50kV system). Characterization data focus on final wafer electrical performance-the performance characteristic that determines ultimate integrated circuit device yield.
The capability of the DUV ALTAÒ 4300 system has been extended by the development of two new optical subsystems: a 0.9 NA, 42X reduction lens and a high-bandwidth acousto-optic deflector based beam position and intensity correction servo. The PSM overlay performance has been improved by modifications to the software algorithms. Characterization data show improved resolution performance in line end shortening, through pitch CD bias and feature corner acuity. The AOD subsystem reduces stripe beam placement errors and random and systematic beam intensity errors. This has enabled local CD uniformity to be reduced to 4.3 nm (3σ) and global CD uniformity to be reduced to 5.8 nm (range/2). Second layer overlay performance is now 20 nm (max error). A split lot wafer evaluation has demonstrated the equivalence of unmodified ALTAÒ 4300 reticles to those printed on a 50 KeV electron beam system for a 130/110 nm device. Wafer lithography results show equivalent CD uniformity, depth of focus and pattern registration results.
Etec Systems, Inc., an Applied Materials company, has completed the implementation and characterization of a deep ultraviolet (DUV), multibeam, raster-scanned mask patterning and integrated process solution. The ALTA® 4000 mask pattern generation system integrates a new data path, environmental control system, DUV optics, a 257nm DUV continuous-wave laser source, and an environmentally stable chemically amplified resist (CAR) process to deliver superior productivity, improved resolution, and critical dimension (CD) control required for volume 130nm mask production. Additionally, to obtain the maximum benefit of this mask pattern generation system, Etec has completed development of an environmentally stable CAR process, which has been tailored to allow the maskmaking industry to continue to receive pre-coated mask blanks from commercial suppliers. This paper details the system architecture and presents system performance and characterization data. The characterization results of the integrated system and process solution are also presented. This integrated pattern generation and process solution continues the tradition of the production workhorse ALTA product line with the introduction of the ALTA 4000 scanned-laser mask pattern generation system.
Techniques used to optimize the alignment performance of the CORE-2564PSM reticle writer are presented. In particular, unique procedures for accurately locating alignment marks with nonuniform background intensities are discussed. Site-by-site automatic illumination control is implemented to ensure optimal image intensity and contrast for the CCD-based image capture system. Process and metrology considerations that affect error measurement are discussed. The mean + range/2 aligned overlay of the CORE-2564PSM is shown to be 35 - 55 nm.
Alignment performance data is presented on a high resolution laser scanning lithography system. The alignment system is a through-the-lens on-axis design which features multiple optical paths such as bright-field and dark-field illumination and high and low magnification legs. Total system overlay is better than 0. 10 tm. 1. DW ALIGNMENT REQUIREMENTS Translating design data into patterned photoresist on wafers typically requires two lithographic steps. First data is transferred to a mask or reticle using either a laser scanning tool such as the ATEQ CORE-2500 or an e-beam system. Next the patterned mask or reticle is projected onto a wafer coated with resist. Throughout this paper I shall refer to systems which use two lithographic steps to transfer a pattern as Indirect Writers (1W). This is in contrast to Direct Writers (DW). As the name implies a DW patterns a wafer without the need for creation of a mask or reticle. 1W alignment systems must accurately register a wafer pattern to a reticle pattern. The most straightforward technique is to directly reference the reticle to the wafer through the projection lens. This approach eliminates baseline problems. 1W alignment systems require high precision. However since they have a reticle to reference (either directly or indirectly) absolute accuracy is not required. Measurements (alignments) are concerned only with the relative offset of the projected reticle image to a pattern on the wafer. The alignment system