SU1171703A1 - Method and apparatus for checking mask - Google Patents

Abstract

1. Method for controlling photomask including irradiating controlled and reference photomasks with electromagnetic radiation fluxes normal to their surfaces with opaque material, detecting radiation transmitted through photomasks, determining deviations of the topology of the surface of an opaque material of the controlled photomask compared to the topology of the reference photomask, measuring spatial parameters of deviations topology and comparing them with acceptable parameters, characterized in that, in order to expand For each class of monitored photomask surface defects, the radiation flux for each of the directions of the topological lines of the surface of the opaque material of the monitored photocable ICECO G3tMf S STH-s-13, il L 1 el, is additionally shifted. i 1 -. TgH (r {- ;, kAZ S "& S -l. On relative to the surface of the photomask at an angle Q in the interval" I / min (rciewrci 1 ZAti I in I (ks / V "KC / (ks where L is the wavelength of the radiation, And the coefficient depending on the resolution of the radiation recorder, c is the maximum allowable micro-relief of the surface of the opaque photoglass material, - / min the minimum distance between the surface elements of the opaque photoglass material, the spatial parameters of the topology deviations , compare them with the tolerance (L), and 2. A device for controlling a photomask, containing a backlight unit, two light-reflecting elements located on the optical axis of the illumination unit and forming control and reference channels, a photomask moving device, connected Kl to the control unit, a comparoscope, a photo registration unit and a signal control and processing unit, connected to a photo registration unit, characterized in that, in order to expand the class of monitored defects The surface of the photomask is additionally inserted into the device a unit for the angular displacement of the plane of the retro-reflecting element of the control channel relative to the optical axis of the backlight unit and the translational movement of the retro-reflecting element relative to the backlight unit.

Description

The invention relates to the field of quality control of the surface of the opaque photomask material by optical methods and can be used to detect defects in non-transparent photomask material. The aim of the invention is to expand the class of photodegree surface defects to be monitored. FIG. 1 shows a structural diagram of a device for controlling a photomask that implements the proposed method for controlling a photomask; on fkg. 2 is a block diagram of a device for moving a retro-reflective element of a control channel. The device comprises an illumination unit 1, reflective elements of a compact 2 and reference 3 channels, a photomask movement device 4, a comparoscope 5 containing beam splitters 6 and 7, a flap 8 and lenses 9-11, a photoregistration unit 12, a control unit including a block 13 determining the position of the photomasks, the control device 14 with the control panel and the synchronization generator 15, the signal processing unit including multiplexers 16 and 17, the quantizer 18, the video monitor 19, the analyzer 20, and the information representation unit 21, the block Another example of the light reflecting element 2 of the control channel 22, the conformable 23 and the reference 24 photomasks. The movement block of the light reflecting element of the control channel 22 contains a suspension 25 of the light reflecting element 2, a guide 26 a sliding bearing 27, a gearbox 28, an engine 29, a screw support 30, a screw guide 31, a gear 32 and an engine 33. The device operates as follows. at once. The backlight unit 1 and the light reflecting elements 2 and 3 direct the radiation beams along the normal to the surface of the photomasks .23 and 24. Using the photomask movement unit 4, the photomasks are set to the working position. The radiation beams that have passed through the controlled 23 and reference templates 24 are combined in a comparoscope 5 and recorded by the photo registration unit 12. The quantizer 18 normalizes the video signal from the threshold photographic recording unit 12 by the threshold voltage. The electcKjqi signal from the quantizer 18 is fed to the input of the analyzer .20, where the parameters of spatial deviations of the topology of the photomasks selected by the comparoscope 5 are determined. After finishing the analysis, the control device 14 transmits a signal to the input of the moving unit of the reflective element 2 of the control channel 22. the incidence of the radiation beam on the controlled photo mask in the specified interval, the angles by the angular displacement of the element 2 by means of the motor 29 and the gearbox 28 and elementa.2po ceiling elements movable guide 26 by the motor 33, the gear 32 and screw pair 30 and 31. In this case, an image is formed of an opaque material and the shadow mask of opaque material. The device then repeats the step of determining parameters of deviations of the photomask topology. The operations of varying the angle of incidence of the radiation beam on a controlled photomask and determining the parameters of the deflected photopaths trpology are carried out for each of the directions of topological lines of the surface of the opaque photomask material. Based on the results of determining the parameters of the deviations of the topography of the photomasks, the analyzer 20 determines the magnitudes of the deviations of the microrelief of the opaque photomask material, compares these values with the permissible parameters and collects information about the presence and coordinates of the photomask defects in the information representation unit 21. The synchronization generator 15 serves to synchronize the operation of the devices of the signal processing unit. The video monitor device 19 allows controlling the installation of the photomasks 23 and 24 and aligning the comparoscope 5 and adjusting the quantizer 18. Example. Photomasks with a topological width of strips of opaque material of 20 microns, a topological distance between strips of 20 microns, and a microrelief height in the range of 0.5-2.5 microns were monitored. The site of one of the photomasks was chosen as a model;

which did not detect defects in the topology of an opaque material, and the height of the microrelief of the surface of an opaque material varied by more than 0.1 µm. In the initial position, the model and controlled photomasks were installed in different channels of the comparoscope, the initial direction of the illuminating flux of electromagnetic radiation was established normal to the surface of the photomask.

The spatial parameters of the surface topology surface reflections of the opaque photomask material were measured and compared with the allowable values.

Then, the electromagnetic radiation flux was shifted for each direction of the topological lines of the opaque photocell material in the plane perpendicular to the direction of the topological lines of the photoglass opaque material relative to the normal to the surface with opaque material 10 by the angle & ".

The spatial parameters of the deviations obtained were measured and compared with the allowable values. f5 The results of the measurements are shown in the table in comparison with the measurement results by the limestone method.

Invalid Dark Point

It's clear

The roughness of the edge: just

topological microrelief

Protrusions:

total topological

topological sizes not allowed

mccorelief

microrelief unacceptable sizes

12 2

58

3

55

3 595 11

ABOUT

3,584

42

1

Claims (2)

1. A method for controlling a photomask, including irradiating the monitored and reference photomasks with electromagnetic radiation fluxes normal to their surfaces with opaque material, detecting radiation transmitted through the photomasks, determining deviations of the surface topology of the opaque material of the monitored photomask compared to the topology of the reference photomask, measuring spatial parameters of deviations topologies and comparing them with valid parameters, characterized in that, in order to expand cc of the controlled surface defects of the photomask, additionally shift the radiation flux for each of the directions of the topological lines of the surface of the opaque material of the monitored photomask by relative to the normal to the surface of the photomask by an angle Θ in the interval ~ ^ ^ '' Ч) ^) 'where L is the radiation wavelength, L coefficient depending on the resolving power of the radiation recorder, N _{M (LKS} ~ the maximum allowable height of the microrelief of the surface of the opaque material of the photomask, the minimum distance between The surfaces of the opaque material of the photomask, measure the spatial parameters of the deviations of the topology, compare them with the permissible parameters, and judge by the results of the main and additional comparisons the validity of the photomask. 2. A device for controlling a photomask, containing a backlight unit, two reflective elements located on the optical axis of the backlight unit and forming a control and reference channels, a device for moving photo masks connected to a control unit, a comparoscope, a photographic recording unit, and control and signal processing units connected to photoregistration unit, characterized in that, in order to expand the class of controlled surface defects of the photomask, the device is additionally connected connected to the control unit lock angular movement of the plane of the reflective element of the control channel relative to the optical axis of the backlight unit and the translational movement of the reflective element relative to the backlight unit.