Mask inspection

About: Mask inspection is a research topic. Over the lifetime, 1072 publications have been published within this topic receiving 8696 citations.

Mask inspection light source, wavelength conversion method and mask inspection device

Abstract: PROBLEM TO BE SOLVED: To provide a mask inspection light source capable of supplying a DUV laser beam at a sufficient power to be used as a mask inspection light source. SOLUTION: The mask inspection light source 101' includes: a laser device with a mode-lock titanium sapphire laser oscillator 111 that generates a laser beam and a titanium sapphire regenerative amplifier 112 that excites the laser beam generated from the mode-lock titanium sapphire laser oscillator 111 with a green laser beam in continuous operation; and a wavelength converting device that generates fourth harmonics of the laser beam extracted from the laser device. COPYRIGHT: (C)2009,JPO&INPIT

Single element and metal alloy novel EUV mask absorbers for improved imaging (Conference Presentation)

Abstract: Current EUV mask technology uses Ta-based metallic absorber layer, on top of a reflective multilayer mirror. Multiple studies have shown that the optical constants and the required 50-70nm thickness of Ta-based metallic absorber at EUV wavelength, do not offer an optimal wafer image, and, for example, produce images with pitch and illumination dependent best focus shifts for patterns at Foundry N5 dimensions. Alternative metal absorbers with higher absorptivity than Ta, such as Ni and Co have been proposed and, in simulation, show improved imaging at <40nm thickness. The replacement of a Ta- absorber by a new type of metal is a formidable task for the mask industry. A novel absorber must not only meet the criteria for improved imaging, but also must meet the required material properties that make it compatible with different steps in mask blank and subsequent mask manufacturing, such as a controlled deposition technique, availability of a patterning process for mask patterning, and be compatible with mask inspection, repair, and cleaning. We have started an experimental evaluation of the properties of thin metal Ni and Co films, and alloys of Ni, considering imaging performance and mask manufacturability. Rigorous lithographic simulations are used to screen potential absorber materials for their imaging properties at Foundry N5 dimensions, and find optimal thickness. The microscopic structure of the thin films was determined using X-ray, X-SEM and X-TEM techniques, and optical constants were measured using ellipsometry at EUV wavelength. Towards mask manufacturing, patterning performance, and resistance to typical mask cleaning chemicals was evaluated experimentally. Standard deposition of Ni and Co metals yielded polycrystalline thin films, that prove difficult to pattern using a traditional etch process. In addition, Co films were found to be affected by standard mask cleaning chemistry. Hence, if Ni and Co are required as new mask materials, also novel patterning techniques will have to be used, that may be additive rather than subtractive. To illustrate this, we show promising performance for area selective Co deposition techniques. To identify new materials, that have better properties towards manufacturing than single-element Ni and Co, we have started the evaluation of metal alloys, at different elemental ratios. This allows to combine Ni with an element that has refractive index closer to 1, or with an element that has even higher absorptivity. The films of metal alloys have been characterized in a similar way as the single element metals, so that they can be compared to single element metals as suitable materials for mask manufacturing.

Substrate inspection apparatus and mask inspection apparatus

Abstract: Substrate inspection apparatus, in which the acquisition of the inspection data for a defect and the acquisition of the focus data of the objective lens are performed in parallel, includes an autofocus apparatus for controlling position of the objective lens along its optical axis. The autofocus apparatus includes a focus error detection unit and a focus control signal generation unit for generating a focus control signal for controlling the position of the objective lens for each scan line using a focus data signal composed of an objective position signal or the objective position signal to which a focus error signal is added. When “i” is assumed as a positive integer and “m” is as a natural number, the focus data signal which was acquired during the scanning period of i-th scan line is used to produce the focus control signal used to scan the (i+2m)-th scan line.

Printability and inspectability of defects on EUV blank for 2xnm hp HVM application

Abstract: The availability of defect-free masks remains one of the key challenges for inserting extreme ultraviolet lithography (EUVL) into high volume manufacturing. Recently both blank suppliers achieved 1-digit number of defects at 60nm in size using their M1350s. In this paper, a full field EUV mask with Teron 61X blank inspection is fabricated to see the printability of various defects on the blank using NXE 3100. Minimum printable blank defect size is 23nm in SEVD using real blank defect. Current defect level on blank with Teron 61X Phasur has been up to 70 in 132 X 132mm2. More defect reduction as well as advanced blank inspection tools to capture all printable defects should be prepared for HVM. 3.6X reduction of blank defects per year is required to achieve the requirement of HVM in the application of memory device with EUVL. Furthermore, blank defect mitigation and compensational repair techniques during mask process needs to be developed to achieve printable defect free on the wafer.

Improving inspectability with KLA-Tencor TeraScan thin line de-sense

Abstract: In the ever-changing semi-conductor industry, new innovations and technical advances constantly bring new challenges to fabs, mask-shops and vendors. One of such advances is an aggressive optical proximity correction (OPC) method, sub-resolution assist features (SRAF). On one hand, SRAFs bring a leap forward in resolution improvement during wafer printing; on the other hand they bring new challenges to many processes in mask making. KLA-Tencor Corp. working together with Samsung Electronics Co. developed an additional function to the current HiRes 1 detector to increase inspectability and usable sensitivity during the inspection step of the mask making process. SRAFs bring an unique challenge to the mask inspection process, which mask shops had not experienced before. SRAF by nature do not resolve on wafer and thus have a higher tolerance in the CD (critical dimension) uniformity, edge roughness and pattern defects. This new function, Thin-Line De-sense (TLD), increase the inspectability and usable sensitivity by generating different regions of sensitivity and thus will match the defect requirement on a particular photomask with SRAFs better. The value of TLD was proven in a production setting with more than 30 masks inspected, and resulted in higher sensitivity on main features and a sharp decrease in the amount of defects that needed to be classified.