Illumination device using a pulsed laser source a Schlieren optical system and a matrix addressable surface light modulator for producing images with undifracted light

• US 5,486,851 A
• Filed: 07/19/1994
• Issued: 01/23/1996
• Est. Priority Date: 10/30/1991
• Status: Expired due to Term

• Current Assignee: Fraunhofer Gesellschaft Zur Foerderung Der Angewandten Forsching E.V.
• Original Assignee: Fraunhofer Gesellschaft Zur Foerderung Der Angewandten Forsching E.V.
• Inventors: Vogt, Holger, Kuck, Heinz, Hess, Gunther, Gehner, Andreas
• Primary Examiner(s): Fuller, Benjamin R.
• Assistant Examiner(s): Gordon, Raquel Yvette
• Application Number:
  US08/232,005
• Time in Patent Office: 553 Days
• Field of Search: 346/108, 346/160, 346/107 R, 355/73, 353/98, 347/241, 347/242, 347/258
• US Class Current: 347/258
• CPC Class Codes: G03F 7/70283 Mask effects on the imaging process
• CPC Class Codes: G03F 7/70291 Addressable masks, e.g. spatial light modulators [SLMs], digital micro-mirror devices [DMDs] or liquid crystal display [LCD] patterning devices
• CPC Class Codes: G03F 7/70358 Scanning exposure, i.e. relative movement of patterned beam and workpiece during imaging

Abstract

An illumination device for producing models used for manufacturing electronic elements, or for direct illumination of wafers or substrates during the photolithographic steps required for their production, or for direct illumination of structures including light-sensitive layers, comprises a pulsed laser light source and a pattern generator.

The pattern generator includes an optical Schlieren system and an active, matrix-addressable surface light modulator. The Schlieren system comprises a Schlieren lens arranged on a side of the surface light modulator, a projection lens facing away from the surface light modulator, and a mirror device which is arranged between the lenses for directing light coming from the light source onto the reflective surface on the surface light modulator. The Schlieren lens is arranged from the surface light modulator at a short distance relative to the focal length of the lens. A filter device is arranged in the diffraction image plane of the virtual point light source between the Schlieren lens and the projection lens, the filter device having a structural design of such a nature that it will either filter out the diffracted light reflected by the addressed surface areas of the surface light modulator or that it will filter out the undiffracted light. During the displacement of a positioning table, the model, the disk, the substrate or structure are composed of a plurality of partial images by adequate addressing of the surface light modulator.

Claims

1. An illumination device for producing models used for manufacturing electronic elements, or for direct illumination of wafers or substrates during photolithographic steps for producing the electronic elements, or for direct illumination of structures including light-sensitive layers, comprising:

a pulsed laser light source;

a pattern generator;

an object onto which light emitted by said laser light source is focussed, said object being selected from the group consisting of a model, a disk, a substrate and a structure;

said pattern generator includes an optical Schlieren system and an active, matrix-addressable surface light modulator,

said surface light modulator has a reflective surface having addressed surface areas which diffract incident light and non-addressed surface areas which reflect incident light,

said Schlieren system comprises a Schlieren lens arranged on a side of said surface light modulator, a projection lens facing away from said surface light modulator, and a mirror device which is arranged between said Schlieren lens and said projection lens for directing light coming from said pulsed laser light source onto said reflective surface on said surface light modulator,

wherein said Schlieren lens is arranged from said surface light modulator a distance less than a focal length of said Schierlen lens,

focussing means for focussing the light coming from said light source in at least one point which is spaced apart from said mirror device and which is adapted to have associated therewith at least one virtual point light source by reflecting a point at said mirror device,

a filter device arranged in a diffraction image plane of the virtual point light source between said Schlieren lens and said projection lens, said filter device being designed to filter out diffracted light reflected by the addressed surface areas of said surface light modulator and permit undiffracted light reflected by said non-addressed surface areas to pass through said projection lens to the model, the disk, the substrate, or the structure, and to filter out undiffracted light reflected by said non-addressed surface areas of said surface light modulator, and permit said diffracted light reflected by said addressed surface areas to pass through said projection lens to the model, the disk, the substrate, or the structure, and

a displaceable positioning table capable of having the model, the disk, the substrate or the structure secured thereon in position so that a sharp image of said surface areas of said surface light modulator can be formed on the model, the disk, the substrate, or the structure,

wherein said pulsed laser light source is constructed such that a pulse duration of said pulsed laser light source is shorter than a minimum structural dimension of the model, the disk, the substrate or the structure divided by a displacement rate of said positioning table, and

wherein, during the displacement of said positioning table, the model, the disk, the substrate or structure are composed of a plurality of partial images by adequate addressing of said surface light modulator.

2. An illumination device according to claim 1, wherein

said mirror device includes a semireflecting mirror arranged at an angle of 45°

relative to an optical axis determined by said Schierlen lens and said projection lens.

3. An illumination device according to claim 1, wherein

said filter device is arranged in a focal plane of said Schlieren lens, and

said focussing device produces a point at which the light from said light source is focussed, the point being located a distance from said mirror device so that a virtual point light source associated with the point by means of reflection at said mirror device is located in the focal plane of said Schlieren lens.

4. An illumination device according to claim 1, wherein

said focussing device produces a point at which the light from said light source is focussed, the point being located a distance from said mirror device so that a virtual point light source associated with the point by means of reflection at said mirror device is produced with a first displacement relative to a focal plane of said Schlieren lens in a direction of said Schlieren lens, and

said filter device being arranged with a second displacement relative to the focal plane of said Schlieren lens in a direction of the projection lens, said second displacement depending on said first displacement.

5. An illumination device according to claim 1, wherein

said focussing device and said mirror device are arranged such that light will fall at an oblique angle onto the reflective surface of said surface light modulator so that undiffracted light is reflected at an angle to an optical axis of said Schierlen lens and said projection lens, and

said filter device permits a lateral spectrum of light of a first order of diffraction and of higher orders of diffraction to pass to said projection lens to filter out zeroth-order light.

6. An illumination device according to claim 1, wherein

said pulsed laser light source is an excimer laser light source.

7. An illumination device according to claim 1, wherein a surface area of said surface light modulator has associated therewith two transistors, each transistor being provided with at least one pair of control electrodes and being capable of producing at least one diffraction grating with said reflective surface and a viscoelastic control layer covered by said reflective surface.

8. An illumination device according to claim 1, further comprising

an automatic loading and unloading device for wafers or substrates disposed adjacent to the displaced positioning table to fully automate illumination of a batch of wafers or substrates.

9. An illumination device according to claim 1, further comprising

preadjustment means and fine adjustment means for permitting accurate, repeated illuminations of the substrates during a production process.

10. An illumination device according to claim 9, wherein

said surface light modulator is used as a programmable reference mark during preadjustment and fine adjustment, said programmable reference mark being located on said surface light modulator.

11. An illumination device according to claim 1, wherein

said reflective surface of said surface light modulator is covered with a liquid-crystal layer, and

wherein said addressable surface areas cause a phase displacement and a diffraction of incident light.

12. An illumination device according to claim 1, wherein

said surface light modulator is provided with a reflective surface including addressable mechanical elements disposed thereon so that bending of said elements causes a phase displacement and a diffraction of the light.

13. An illumination device according to claim 12, wherein

said mechanical elements include reeds disposed on said surface light modulator which are adapted to be bent and which are provided with a reflecting surface.