DE4208103A1

DE4208103A1 - Auto-correlation of measuring inaccuracies in lithography system - forming superimposed images of linear and strip grids on high resolution film, subjecting to effect for set time, and observing using microscopic

Info

Publication number: DE4208103A1
Application number: DE19924208103
Authority: DE
Inventors: Bernd Huebner; Hans W P Dipl Phys Dr Koops
Original assignee: Individual
Current assignee: Individual
Priority date: 1992-03-13
Filing date: 1992-03-13
Publication date: 1993-09-16

Abstract

The method involves illuminating a linear grid with a corpuscular optical beam-system under investigation and using a high resolution recording film. An image of a strip grid of the same grid constant but slightly relatively rotated is superimposed onto the film after a finite period, table movement or other influence on the equipment. The resulting beam position error relative to the first image is magnified in the direction perpendicular to the grid direction by the reciprocal of the rotation angle. It can be directly read off in nanometres from the Moire strips using a microscope after developing the substrate. USE/ADVANTAGE - For quality control of lithographic processes, allowing measurement of position errors, thermal and mechanical instabilities, and image distortion. Accuracy of a few nm is achieved with direct read-out not requiring computer processing.

Description

State of the art

Meßverfahren mit wenigen nm Auflösung zur Qualitätskontrolle lithographischer Prozesse sind in Form von Biidauswertungsgeräten erhältlich, welche sehr teuer sind und dann stets vom verwendeten Prozeß der Registrierung abhängig sind. (1, 2, 3, 4). Geräte, welche die Leistungsfähigkeit eines Lithographiesystems mit nm Auflösung, auch zeitaufgelöst und unabhängig vom verwendeten Registrierprozeß vermessen, sind nicht bekannt. Mit dem Selbstvergleichsverfahren und der Kombination mit Nonius-Registrierung zur Klärung der Eindeutigkeit der Messung, sowie mit der Kombination mit Kontrast-Eich-Registrierungen steht ein hochauflösendes Meßverfahren zur Verfügung, das im nm-Bereich die Vermessung von Lithographiegeräten bezüglich der Driften, der thermischen und mechanischen Instabilitäten, der zeitaufgelösten Gerätestabilität, der Feldverzeichnungen und der Stitching-Fehler (Anschlußfehler benachbarter Registrierfelder) ermöglicht. Die Aussage ist direkt und unter Einsatz nur eines optischen Mikroskops sofort nach dem Entwickeln der Registrierung erhältlich und direkt klar ablesbar. Es ist kein Rechner zur Auswertung der Aussage nötig. Measurement methods with a few nm resolution for quality control of lithographic processes available in the form of image evaluation devices, which are very expensive and then always from used process of registration are dependent. (1, 2, 3, 4). Devices that the Performance of a lithography system with nm resolution, also time-resolved and measured regardless of the registration process used are not known. With the Self-comparison procedure and the combination with Nonius registration to clarify the Uniqueness of the measurement, as well as with the combination with contrast calibration registrations a high-resolution measuring method is available, which measures in the nm range Lithography devices regarding the drifts, the thermal and mechanical instabilities, the time-resolved device stability, field distortions and stitching errors (connection errors neighboring registration fields). The statement is direct and using only one optical microscope available immediately after developing the registry and immediately clear readable. No computer is required to evaluate the statement.

literature

1. Kanteneinfangmikroskopie und Linienbreitenmessung, Zusatz zum JSM840 Rastermikroskop, Firmenschrift JEOL Ltd
2. Nikon optisches Linienbreitenmeßgerät, Firmenschrift
3. Meßsystem mit Elektronenstrahlabtastung, Firmenschrift LEICA
4. Hitachi Linienbreitenmeßsystem, Firmenschrift1. Edge capture microscopy and line width measurement, addition to the JSM840 scanning microscope, company lettering JEOL Ltd
2. Nikon optical line width measuring device, company lettering
3. Measuring system with electron beam scanning, company name LEICA
4. Hitachi line width measuring system, company lettering

Captions

Fig. 1 Das Selbstvergleichsverfahren ergibt bei der Überlagerung eines geraden (1) und eines im kleinen Winkel dagegen verdrehten Meßgitters (2) bei Verschiebungen Moire-Streifen (3), aus deren Verlauf die Fehlplazierung der zweiten Registrierung mit nm- Genauigkeit im Lichtmikroskop abgelesen werden kann. Fig. 1 The self-comparison method results in the superposition of a straight ( 1 ) and a measuring grid ( 2 ) rotated against it at a small angle with displacements Moire stripes ( 3 ), from the course of which the incorrect placement of the second registration with nm accuracy can be read in the light microscope can.

Fig. 2 Nonius-Maßstäbe (4) in x- und y-Richtung zusammen mit den im Selbstvergleichsverfahren registrierten geraden (1) und schrägen (2) Gittern messen die Größe und Richtung der modulo der Meßgitterkonstante aufgetretenen Verschiebung. Fig. 2 vernier scales ( 4 ) in the x and y direction together with the straight ( 1 ) and oblique ( 2 ) grids registered in the self-comparison method measure the size and direction of the modulo of the measuring grid constant of the shift that has occurred.

Fig. 3 Überlagerungs-Registrierungen (5) aus geraden und definiert dazu verschobenen schiefen Gittern erzeugen Moire-Kontraste (3), die die Charakteristik des Registrierprozesses bei der lichtmikroskopischen Auslesung der im Selbstvergleichsverfahren erhaltenen Meßkontraste eliminieren. Fig. 3 overlay registrations ( 5 ) from straight and defined displaced inclined gratings generate moiré contrasts ( 3 ) which eliminate the characteristics of the registration process in the light microscopic reading of the measurement contrasts obtained in the self-comparison method.

Fig. 4 Selbstvergleichsverfahren, eine Methode zur Kontrolle der kritischen Plazierung von aufeinanderfolgenden Registrierfeldern (6), (7) mit dazwischen liegender Tischverschiebung, angewandt im lithographischen Produktionsprozeß von in ihrer relativen Lage zueinander sehr kritischen Strukturen. Fig. 4 self-comparison process, a method for checking the critical placement of successive registration fields ( 6 ), ( 7 ) with intermediate table displacement, used in the lithographic production process of structures which are very critical in their relative position to one another.

Claims

1. Self-comparison method, a method for measuring inaccuracies in lithography systems with a clear statement through the use of nonies and with a statement independent from the registration process through the use of defined misplaced calibration grid registrations, which are registered and developed under the same conditions as the grids of the Measurement examination, characterized in that, see Fig. 1, a straight grid ( 1 ) with z. B. 150 nm grating constant oriented in the x and y directions with the corpuscular-beam-optical device to be examined on a high-resolution recording film, and in a second step a line grating ( 2 ) of the same grating constant rotated by a very small angle over the first Registration is exposed after a finite time has passed, or a table movement, or a temperature change on the device, or after another thermal, mechanical, electromagnetic or acoustic influence acts on the device. Incorrect positioning of the beam in relation to the location of the first registration is shown, enlarged by the reciprocal of the angle of rotation in the direction perpendicular to the grating direction and can be read from the resulting Moire stripes directly in nm after the development of the substrate when viewed in an optical microscope .

2. Self-comparison method, a method for measuring inaccuracies in lithography systems according to claim 1, characterized in that the lack of uniqueness of the statement usual in the Moire method due to the parallel registration of vernier scales ( 3 ) with the resolution resolution of the measuring grid constant in the same Field of view in the x and y directions can also be registered and read out in the light microscope, see FIG. 2, whereby the size and direction of the shift occurring modulo of the measuring grid constant is recognized.

3. Self-comparison method, a method for measuring inaccuracies in lithography systems according to claim 1, characterized in that before the overlay registration of the measuring grids straight and oblique grids with a shift programmed in the nm range relative to one another as contrast calibration structures ( 5 ) in x- and y- Direction can be registered without large intermediate times and external influences superimposed. This makes the process independent of the registration process used and of the limits of the usable field size, in which the overlay registration can be defined without moving the table. The shift displayed in the moiré strip can be read out directly by comparing the contrasts obtained in the calibration field and in the measuring field with the light microscope using the calibration series required for small measuring fields.

4. Self-comparison method, a method for measuring inaccuracies in lithography systems according to claim 1, characterized in that, see Fig. 4, so that the placement of registrations in the critical joining of registration fields, for. B. after table shift, by cross-field overlay registration of the previous ( 6 ) with the subsequent field ( 7 ) using straight ( 1 ) and oblique ( 2 ) grids, by vernier scales ( 4 ) for uniqueness and comparison - Documentation with defined incorrect placement of the oblique grids for contrast uniqueness ( 5 ) is documented and checked with nm resolution.