Mask Defect Repair Research Articles

APPLICATION OF EQUIPMENT FOR AUTOMATIC CONTROL OF PLANAR STRUCTURES IN MANUFACTURING MASTER MASKS OF INTEGRATED CIRCUITS ON PHOTO-MASKS

Following the concept of defect-free manufacturing of master masks of IC on photo-masks, two Belarusian sets of optomechanical equipment for 0,3 5 p and 90 nanometers are presented in the paper. Each of the sets comprises:Multi-channel laser pattern generator;Automatic mask defect inspection system;Laser-based mask defect repair system.The paper contains description of automatic mask defect inspection process during photo-mask manufacturing and respective basic technological operations of the processes.Advantages of a complex approach to the development of a set of opto-mechanical equipment for defect-free manufacturing of photo-masks have been analyzed in the paper.Fig. 2. Tab. 3. Ref: 6 titles.

Progress in extreme ultraviolet mask repair using a focused ion beam

The key challenge in extreme ultraviolet (EUV) mask defect repair is to avoid or limit the damage to the sensitive reflective multilayer (ML) stacks on the mask substrate and repair <55 nm mask defects. Our EUV mask design employs an oxide buffer layer between the ML and the absorber to protect the ML during repair. We have developed both opaque and clear EUV mask defect repair processes using focus ion beam (FIB) based gas-assisted etching (GAE) and ion-induced deposition. The process has been successfully demonstrated on our TiN baseline mask by 10× EUV print tests of 100 nm resist lines/spaces. More importantly we have assessed the current FIB tool performance capability and compared it with the general requirements for repairing the EUV mask for the 70 nm lithography node. The characterization includes minimum “effective” beam size, etch selectivity, and edge placement precision. We discussed the required improvements and future directions in repair tool research and development in order for the mask repair technology to keep pace with lithography scaling in future generations.

Optimization of FIB methods for phase shift mask defect repair

Two new methods have been proposed to optimize the focused ion beam (FIB) technique for repair of phase shift masks (PSMs). The alternating box method is used to eliminate the post FIB repair phase trench defect and the biased method to eliminate the gallium staining effect. Both methods require only a change of sputtering or beam scanning strategy. Rim, halftone and embedded PSMs for contact hole and poly line features with programmed defects have been fabricated and repaired by the new methods. Computer simulation and experimental photolithography have confirmed that opaque defects can be repaired by the optimized FIB technique without leaving any post repair “ghost” defects.

Focused-Ion-Beam-Induced Gas Etching

Focused ion beam (FIB)-assisted gas etching has several advantages over physical sputtering in many applications. Advantages include etch rate enhancements of one to two orders of magnitude, dramatically reduced redeposition of etched material on sidewalls in high-aspect-ratio structures, etch selectivity, and reduced implantation of the primary ion species in the sample. Applications which benefit from focused ion beam (FIB) gas etching include photomask and X-ray mask defect repair, integrated circuit modification for failure analysis, and sample preparation for scanning electron microscope and transmission electron microscope analysis. This paper describes a simple phenomenological model which takes into account the ion beam and scanning parameters, gas flux, and basic material constants. Approximate formulas are given in terms of these parameters and compared to experimental results.

Reflection mask defect repair

We developed a new technique for the repair of opaque defects on soft-x-ray projection lithography reflection masks by using ion-beam etching and a thin Si overcoat on the multilayer mirror. This technique clears the defect without damaging the multilayer mirror or introducing an absorptive element into the multilayer. Our procedure uses a beam of low atomic number ions (Si or Ar) of reduced beam energy and a thin Si overcoat to protect the multilayer mirror.

Digital scan model for focused ion beam induced gas etching

Focused ion beam (FIB), assisted, gas etching has several advantages over physical sputtering in many FIB applications. Advantages include etch rate enhancements of 1–2 orders of magnitude, dramatically reduced redeposition of etched material on sidewalls in high-aspect ratio structures, and reduced implantation of the primary ion species in the sample. Applications which benefit from FIB gas etching include photomask and x-ray mask defect repair, integrated circuit modification for failure analysis, and sample preparation for scanning electron microscope and transmission electron microscope analysis. In this article, a simple model is presented which takes into account the ion beam and scanning parameters, gas flux, and basic material constants. Approximate formulas are given in terms of these parameters and compared to experimental results.

Phase-shifting lithography: Maskmaking and its application

The use of phase-shifting masks (PSMs) allows substantial improvement in resolution and depth-of-focus of optical systems. Before the advantages of PSMs can be realized in a production process, several problems of mask technology must be solved. In order to advance PSMs from a development tool to a production tool for very large scale integration (VLSI) devices, the technologies concerning mask fabrication, mask inspection, and mask repair have been investigated. A silicone-based resist has been developed for simplifying the mask fabrication processes. The printability and detectability of shifter defects have been investigated in order to specify the requirements of systems of PSM manufacture and inspection. The developed silicone-based resist has been applied for mask defect repair. These technologies can bring PSMs closer to being a practical production tool for VLSI. To verify the effectiveness of PSMs for device manufacturing, PSMs have been successfully applied to gate definition of a high-speed GaAs field effect transistor, contact hole fabrication, and storage node (cell capacitor) fabrication of a dynamic random access memory device.