The phase-shifting mask consists of a normal transmission mask that has been coated with a transparent layer patterned to ensure that the optical phases of nearest apertures are opposite. Destructive interference between waves from adjacent apertures cancels some diffraction effects and increases the spatial resolution with which such patterns can be projected. A simple theory predicts a near doubling of resolution for illumination with partial incoherence σ < 0.3, and substantial improvements in resolution for σ < 0.7. Initial results obtained with a phase-shifting mask patterned with typical device structures by electron-beam lithography and exposed using a Mann 4800 10× tool reveals a 40-percent increase in usuable resolution with some structures printed at a resolution of 1000 lines/mm. Phase-shifting mask structures can be used to facilitate proximity printing with larger gaps between mask and wafer. Theory indicates that the increase in resolution is accompanied by a minimal decrease in depth of focus. Thus the phase-shifting mask may be the most desirable device for enhancing optical lithography resolution in the VLSI/VHSIC era.

Improving resolution in photolithography with a phase-shifting mask

Provided is a light emitting diode (LED) manufactured by using a wafer bonding method and a method of manufacturing a LED by using a wafer bonding method. The wafer bonding method may include interposing a stress relaxation layer (33) formed of a metal between a semiconductor layer (20) and a bonding substrate (31). When the stress relaxation layer is used, stress between the bonding substrate and a growth substrate may be offset due to the flexibility of metal, and accordingly, bending or warpage of the bonding substrate may be reduced or prevented.

Light-emitting device and method of manufacturing the same

Nanofabrication by electron beam lithography and its applications

A process for removing at least a portion of a film from a substrate, such as a wafer of silicon or other similar materials, the film on the substrate typically being an oxide film, maintaining the atmosphere embracing the substrate at near room temperature and at near normal atmospheric pressure, flowing dry inert diluent gas over the substrate, introducing a flow of reactive gas, preferably an anhydrous hydrogen halide gas, namely anhydrous hydrogen flouride gas, for typically 5 to 30 seconds over the substrate and film to cause the removal of portions of the film, flowing water vapor laden inert gas, preferably nitrogen, over the substrate and film from a time prior to commencing flow of the reactive gas until flow of the reactive gas is terminated. In the case of non-hygroscopic film on the substrate, the flow of water vapor continues during the flow of the reactive gas and is terminated shortly after the termination of the flow of reactive gas. In the case of hygroscopic film, the flow of water vapor is discontinued prior to the start of flow of the reactive gas. In carrying out the process, a process chamber is needed to confine the substrate and have a vent, which though restricted, continuously open to the atmosphere.

Gaseous process and apparatus for removing films from substrates

A method and apparatus for creating a phase shifting mask and a structure mask for shrinking integrated circuit designs. One embodiment of the invention includes using a two mask process. The first mask is a phase shift mask and the second mask is a single phase structure mask. The phase shift mask primarily defines regions requiring phase shifting. The single phase structure mask primarily defines regions not requiring phase shifting. The single phase structure mask also prevents the erasure of the phase shifting regions and prevents the creation of undesirable artifact regions that would otherwise be created by the phase shift mask. Both masks are derived from a set of masks used in a larger minimum dimension process technology.

Phase shifting circuit manufacture method and apparatus

One drawback of phase-shifting lithography lies in the high printability of shifter defects. A transparent object on masks (shifter defects) produces lead or lag of the optical phase, which causes an unique printability with respect to focus level. We investigated the printability of shifter defects on phase-shifting masks in out-of-focus conditions. Two types of shifter defects related to the phase angle were investigated: (a) a phase error which is a shifter layer having an incorrect thickness and (b) a phase angle defect which is a defect having a phase angle other than 180°. Phase error causes asymmetrical pattern profiles. It was found that the illumination coherence factor (σ) has a strong influence on the allowance of the shifter thickness (phase error). The effect of phase angle defects located in a large clear area and in small features was investigated. The phase angle defects have an optimum focal plane other than the best focal plane. A defect with a low phase shift located in fine patterns has high printability. In order to establish a mask fabrication process for production-worthy phase-shifting masks, further investigation in the detection of low phase angle shifter defects is necessary.

Detection and Printability of Shifter Defects in Phase-Shifting Masks II. Defocus Characteristics

Because of the high printability of shifter defects in phase-shifting masks, it is worthwhile to characterize the inspection and printing of the shifter defects. The detectability and printability of shifter defects as a function of size and location have been investigated by experiments and simulation. A test mask with various programmed shifter defects was inspected by means of a die-to-die inspection system and printed in positive resist with an i-line stepper. Corner defects are difficult to detect and have low printability. A defect located in small features has high printability. We have also investigated the detectability and printability of the phase angle defects which have phase angles other than 180°. Defects with 120° to 180° phase angles have high printability. Defects with phase angles below 90° are not printed.

https://iopscience.iop.org/article/10.1143/JJAP.30.3016/pdf

Detection and printability of shifter defects in phase-shifting masks

Phase shifting technologies achieve significant improvement in both resolution and depth of focus (DOF). We have proposed a "transparent-type" phase shifting mask which has a simple structure (no Cr layer) that considerably improves the resolution limit of optical lithography.1) In this paper, we describe in detail pattern transfer characteristics of the transparent phase shifting mask with i-line steppers. The effects of numerical aperture (NA) and coherence factor (σ) on the resolution capability and DOF were investigated using simulations and experiments. Patterns are printed using i-line steppers with a numerical aperture (NA) of 0.45 and 0.65. A pattern of 0.23 µm lines and spaces is resolved with a 0.45 NA i-line stepper. DOF for 0.25-µm features is found to be in the 1.5-µm range. Well-resolved 0.18-µm lines and spaces are obtained with a 0.65-NA i-line stepper. Transparent phase shifting mask technologies extend the resolution limit of i-line lithography to the resist features below 0.2 µm.

Pattern Transfer Characteristics of Transparent Phase Shifting Mask

The invention discloses a heterojunction Type GaAs field-effect transistor of the type in which a channel region consists of an n-type GaAs layer with a higher mobility and a gate region consists of a p-type Ga 1-y Al y As layer which is grown heteroepitaxially. The length of the gate is of the order of microns, and a gate, source and drain electrodes are self-aligned. The gate region is etched in the form of a mushroom with the use of an etchant which etched the GaAlAs layer and the Ga-As layer at different etching rates so that the gate, source and drain electrodes may be formed by only one vacuum deposition of a metal such as aluminum.

Junction gate type gaas field-effect transistor and method of forming

Phase shifting technologies with an i‐line stepper are applied for the application of defining sub‐quarter‐micron gate patterns for GaAs field‐effect transistor (FET) devices. Transparent‐type phase‐shifting masks which have no chromium layer for printing the patterns are used. Using the phase‐shifting technologies for gate delineation, it is shown that fine gate patterns with large pad areas can be defined. We have fabricated gate patterns for high‐performance GaAs FET devices with gate lengths in the 0.15–0.5 μm range.

Morio Inoue

Papers

Detection and Printability of Shifter Defects in Phase-Shifting Masks II. Defocus Characteristics

Detection and printability of shifter defects in phase-shifting masks

Pattern Transfer Characteristics of Transparent Phase Shifting Mask

Junction gate type gaas field-effect transistor and method of forming

Sub‐quarter‐micron gate pattern fabrication using a transparent phase shifting mask