A method for controlling the flow of gas through a spectrometer, comprising: flowing a gas through a volume of the spectrometer, the volume being a volume through which light from a sample passes along a first path to reach a first detector and the gas being transparent to the light in a spectral region analysed by the spectrometer; transmitting light from a light source along a second path through the gas to a second detector; detecting an intensity of the light from the light source at the second detector at one or more wavelengths of the light; comparing the detected intensity of the light to a respective setpoint corresponding to a desired transmittance of the gas in the volume of the spectrometer and generating at least one error signal based on the comparison; and adjusting a flow rate of the gas through the volume of the spectrometer based on the error signal, in particular to minimise the difference between the detected intensity and setpoint.

Apparatus and methods for forming an image of an object which involves focusing partially to fully spatially-coherent radiation onto a sample and collecting the resulting scattered radiation (the “standard data set”) on an array detector. In addition to the standard dataset, an additional measurement or plurality of measurements is made of a relatively-unscattered beam, using the array detector, which comprises the “modulus enforced probe (MEP) dataset”. This MEP dataset serves as an extra constraint, called the MEP constraint, in the phase retrieval algorithm used to reconstruct the image of the object.

An apparatus and a method for correctly measuring a phase of an extreme ultraviolet (EUV) mask and a method of fabricating an EUV mask including the method are described. The apparatus for measuring the phase of the EUV mask includes an EUV light source configured to generate and output EUV light, at least one mirror configured to reflect the EUV light as reflected EUV light incident on an EUV mask to be measured, a mask stage on which the EUV mask is arranged, a detector configured to receive the EUV light reflected from the EUV mask, to obtain a two-dimensional (2D) image, and to measure reflectivity and diffraction efficiency of the EUV mask, and a processor configured to determine a phase of the EUV mask by using the reflectivity and diffraction efficiency of the EUV mask.

Methods and systems for determining one or more characteristics of light in an optical system are provided. One system includes first detector(s) configured to detect light having one or more wavelengths shorter than 190 nm emitted from a light source at one or more first angles mutually exclusive of one or more second angles at which the light is collected from the light source by an optical system for illumination of a specimen and to generate first output responsive to the light detected by the first detector(s). In addition, the system includes a control subsystem configured for determining one or more characteristics of the light at one or more planes in the optical system based on the first output.

An EUV light generation apparatus includes a chamber; a prepulse laser outputting prepulse laser light; a main pulse laser outputting main pulse laser light; a combiner combining optical paths of the prepulse laser light and the main pulse laser light; a light concentrating unit concentrating, on the target, the prepulse laser light and the main pulse laser light having the optical paths combined; a stage changing a position of the light concentrating unit; a first actuator changing a travel direction of the main pulse laser light; an EUV light sensor detecting EUV energy; a laser energy sensor detecting pulse energy of the main pulse laser light; and an EUV light generation control unit controlling the stage so that temporal variation of the EUV energy decreases and controlling the first actuator so that a ratio of the EUV energy to the pulse energy increases.

An apparatus and a method for correctly measuring a phase of an extreme ultraviolet (EUV) mask and a method of fabricating an EUV mask including the method are described. The apparatus for measuring the phase of the EUV mask includes an EUV light source configured to generate and output EUV light, at least one mirror configured to reflect the EUV light as reflected EUV light incident on an EUV mask to be measured, a mask stage on which the EUV mask is arranged, a detector configured to receive the EUV light reflected from the EUV mask, to obtain a two-dimensional (2D) image, and to measure reflectivity and diffraction efficiency of the EUV mask, and a processor configured to determine a phase of the EUV mask by using the reflectivity and diffraction efficiency of the EUV mask.

We have invented an EUV spectroscopic polarimeter including a light receiving element, a first polarizing modulation element, a second polarizing modulation element, an energy splitting element and a light detecting and analyzing apparatus. The light receiving element is for receiving a target light. The first polarizing modulation element is rotatably connected to the light receiving element for generating a first polarized light. The second polarizing modulation element is rotatably connected to the first polarizing modulation element for generating a second polarized light. The energy splitting element receives the second polarized light so as to generate a modulated-polarization and energy-resolved light. The light detecting and analyzing apparatus receiving the polarization-modulated and energy-resolved light and providing a spectrum information by an analyzing algorithm which is able to retrieve the helicity, ellipticity, tilt angle and the degree of polarization for the whole spectrum of the target light.

Methods, apparatus, and processes which use Extreme ultraviolet radiation (EUV) and/or soft X-ray wavelengths to read, image, edit, locate, identify, map, alter, delete, repair and sequence genes are described. An EUV scanning tool which allows high throughput genomic scanning of DNA, RNA and protein sequences is also described. A database which records characteristic absorption spectra of gene sequences is also described.

A device may be provided for element analysis of materials by means of optical emission spectroscopy, particularly by means of laser-induced plasma spectroscopy, said device having: means for exciting a plasma from a partial quantity of a test sample made of the material to be analyzed; means for detecting and for spectral analysis of optical radiation emitted from the plasma; beam guidance means for guiding at least a part of the optical radiation emitted from the plasma to the means for detecting and spectral analysis; and means for flushing at least one partial region of the device with an inert gas, wherein the beam guidance means are at least one capillary tube, which additionally serves to guide the inert gas. A method may be provided for element analysis of materials by means of optical emission spectroscopy using the device.

A method and apparatus for cleaning vacuum ultraviolet (VUV) optics (e.g., one or more mirrors of a VUV) of a substrate inspection system is disclosed. The cleaning system ionizes or disassociates hydrogen gas in a VUV optics environment to generate hydrogen radicals (e.g., H*) or ions (e.g., H.sup.+, H.sub.2.sup.+, H.sub.3.sup.+, which remove water or hydrocarbons from the surface of the one or more mirrors. The one or more VUV mirrors may include a reflective material, such as aluminum. The one or more VUV mirrors may have a protective coating to protect the reflective material from any detrimental reaction to the hydrogen radicals or ions. The protective coating may include a noble metal.