Mask profile of chromeless phase-shifting lithography (CPL) defined by OCD has been investigated. In CPL masks,
unbalanced bombardments caused by different ion accelerations lead to the formation of micro-notch structures. A better
understanding of micro-notch structures is essential for quality gating of mask processes to improve of CPL mask
profiles. By measuring 12 of 16 elements of Mueller matrix, we are able to set up a model to simulate the depth of
micro-notch structure profile which shows good correlation with TEM images. Moreover, values of CD, quartz etching
depth and side wall angle acquired by OCD are presented and compared with those obtained by SEM, TEM and AFM,
The fundamentals of droplet-based cleaning of photomasks are investigated and performance regimes that enable the use
of binary spray technologies in advanced mask cleaning are identified. Using phase Doppler anemometry techniques, the
effect of key performance parameters such as liquid and gas flow rates and temperature, nozzle design, and surface
distance on droplet size, velocity, and distributions were studied. The data are correlated to particle removal efficiency
(PRE) and feature damage results obtained on advanced photomasks for 193-nm immersion lithography.
According to the ITRS roadmap for lithography (2008 edition), the CD uniformity requirement of optical masks beyond
32nm HP is less than 1.5nm (3σ). Especially for double patterning lithography, not only the global uniformity but also
the local uniformity is of very high concern. Therefore it is imperative that the develop process will yield CD-linewidth
control independent of pattern sizes or pattern loading, following precisely those pattern size image correction strategies
applied during mask writing (e.g. proximity and fogging correction). Conventional methods of resist develop cannot
meet such requirement without negative side effects (e.g. increased dark loss, pattern collapse, global CD-uniformity
degradation and/or defect issues). The ASonic® nozzle developed by HamaTech APE combines the very favorable dark
loss, defect and global CD-linewidth control benefits of a fast and uniform low impact initial develop dispense (surface
wetting), with an enhanced developer agitation through acoustic streaming, which provides improved local CD-control
independent of pattern size and loading.
The principle functionality of the ASonic® nozzle is described. Developing loading effect is examined with various
conditions and CD linearity, proximity and CD uniformity are also verified.
Laser pattern generators ALTA 3500 and 3700 are widely used for 0.18 micron and above technology nodes in photomask manufacturing. They have low butting, high throughput and high position accuracy, with some weaknesses such as, corner rounding, no proximity effect correction and poor CD linearity when compared to E-beam pattern generators. Optical Proximity Correction (OPC) software was thus created to extend the productivity of laser pattern generators. For contact holes serifs are typically added at the four corners to enhance pattern fidelity. However, the serifs or scattering bars can significantly increase the data size. In our study, we generated serifs for contact holes but applied different exposure strategies: (1) lumping serifs together with the main pattern; (2) exposing serifs and main pattern separately with same dosage; (3) exposing serifs and main pattern separately with different dosages. We examined the results of each approach in terms of contact hole quality, throughput, and inspection results.
Recently, the design of integrated circuits has become more and more complicated due to higher circuit densities. In particular for logic applications, the design is no longer uniform but combines different kinds of circuits into one mask layout resulting in stringent criteria for both wafer and photomask manufacturing. Photomask CD uniformity control and defectivity are two key criteria in manufacturing today’s high-end reticles, and they are both strongly impacted by the mask developing process.
A new photomask develop tool (ACT-M) designed by Tokyo Electron Limited (TEL) has been installed at the Advanced Mask Technology Center (AMTC) in Dresden, Germany. This ACT-M develop tool is equipped with a standard NLD nozzle as well as an SH nozzle which are both widely used in wafer developing applications. The AMTC and TEL used the ACT-M develop tool to adapt wafer puddle develop technology to photomask manufacturing, in an attempt to capture the same optimum CD control enjoyed by the wafer industry. In this study we used the ACT-M develop tool to examine CD uniformity, local loading and defect control on P-CAR and N-CAR photomasks exposed with 50keV e-beam pattern generators. Results with both nozzle types are reported. CD uniformity, loading, and defectivity results were sufficient to meet 65-nm technology node requirements with these nozzles and tailored made develop recipes for photomask processing.
A new photomask develop tool designed by Tokyo Electron Limited (TEL) with wafer puddle technology was evaluated at the Advanced Mask Technology Center (AMTC) in Dresden, Germany. Parameters selected for this evaluation were resist dark loss uniformity, critical dimension (CD) uniformity, loading, linearity, resist cross sectional images, and defects using chemically amplified resists (CARs) exposed with DUV (l=257nm) and 50KeV e-beam pattern generators. Implementing wafer puddle technology to photomask developing was not a simple, straightforward process. Standard CAR puddle recipes for wafer developing were inadequate to match CDU requirements for photomasks at the 130nm technology node using DUV exposure. While the results were disappointing, the TEL alpha develop tool cannot be held entirely responsible. Other, non-develop tool related factors such as resist, substrate, coating bake temperature and time, lithography tool, and post exposure bake temperature and time, all contributed to the final post develop results. Indeed, other CAR/substrate combinations exposed at 50keV e-beam and processed on the TEL alpha develop tool were markedly better in CD performance when compared to DUV results. The AMTC has recently taken delivery of a full scale, production worthy, TEL photomask develop tool for use at future technology nodes.
The challenges, mask manufacturing is faced with, are more and more dominating the semiconductor industry as the pattern sizes shrink. Today's mask patterns have reached sizes that are common in wafer manufacturing. Looking into the industry, we can see that some of the quality parameters - such as CD uniformity and defect control - are managed better in wafer than in mask manufacturing. Consequently, mask manufacturers have started to apply more wafer processing techniques to mask processes. Among others, develop process has a great impact on the quality of the mask manufacturing. This contribution describes how Tokyo Electron Limited (TEL) scanning (linear drive nozzle) developer processing (widely used in advanced wafer manufacturing) was adapted for mask development. Out of this technology transfer, a new alpha-type mask develop tool was launched at TEL and an evaluation of this tool was carried out at the Advanced Mask Technology Center (AMTC), Dresden, Germany. Target of this collaboration was to successfully transfer wafer processing technology to mask making. By this, valuable information was generated, that has been implemented into the production platform, which is commercialized since first half of 2004.