Lithography

Claim 2

Apparatus for illuminating a substrate with a pattern determined by a shadow mask having transparent regions and opaque regions collectively defining a pattern to be illuminated on said substrate, comprising: a light source assembly of finite predetermined area having an effective brightness distribution incorporating a dark central region surrounded by a bright rim and producing substantially coherent light at a selected wavelength, a shadow mask bearing said pattern to be imaged on said substrate, means supporting said mask at a selected position between said substrate and said light source assembly in the path of the light therefrom, said selected position lying at a distance from said substrate of the same order as the width of said transparent portions of said mask, whereby diffraction of light passing through said transparent regions in said mask results in diffraction fringes which substantially cancel each other out at least adjacent the edges of the pattern determined by said transparent regions, so that a sharp image of said shadow mask is obtained on said substrate when illuminated by said source assembly.

Claim 3

Illumination means according to claim 1, in which said source assembly has an annular shape.

Claim 4

Illumination means according to claim 1, in which said effective brightness distribution of the source assembly comprises a number of bright zones distributed regularly in an annular pattern around the central dark zone.

Claim 5

Illumination means according to claim 1, in which the source assembly comprises a source and means effecting orbital movement of said source around a circular path to provide an annular effective brightness distribution over the period of an exposure.

Claim 6

Illumination means according to claim 1, in which the source assembly comprises a source providing a collimated light beam and means scanning said beam over a conical or cylindrical surface cyclically.

Claim 7

Illumination means according to claim 5, in which said scanning means comprises a reflecting element mounted for rotation in the path of said collimated light beam, and means rotating said element to effect scanning of said beam.

Claim 8

Illumination means according to claim 5, in which said scanning means comprises a refracting element mounted for rotation in the path of said collimated light beam, and means rotating said element to effect scanning of said beam.

Claim 9

Illumination means according to claim 7, in which the rotatable refracting element comprises a rotatable wedge prism mounted in the path of said light beam from said source, and a collimator through which said beam passes after traversing said prism, the resulting collimated beam performing a conical scan upon rotation of the wedge prism.

Claim 10

Illumination means according to claim 7, in which the rotatable refracting element comprises a rotatable wedge prism mounted in the path of the said beam, and including a collimator interposed between the prism and the source, so that the collimated beam upon emerging from the prism performs a conical scan upon rotation of the prism.

Claim 11

Illumination means according to claim 6, in which the rotatable reflecting element comprises a plane mirror mounted for rotation about an axis which is inclined to the normal to the reflecting surface of the mirror and including a collimator, said plane mirror being positioned in said light path between the light source and said collimator, the resulting collimated beam performing a conical scan upon rotation of the mirror.

Claim 12

Illumination means according to claim 7, in which the rotatable refracting element comprises a rhomb prism mounted for rotation about an axis perpendicular to two plane parallel faces through which said light beam passes.

Claim 13

Illumination means according to claim 1, in which the source assembly provides light having a wavelength of substantially 0.4 microns and said means supporting said mask a selected distance from said substrate supports said mask between about 9 and 12 microns from said substrate.

Claim 14

Illumination means according to claim 3, in which the source comprises in combination a single point source and a fixed multiple prism comprising a number of prism elements arranged in an annular array such that light from the point source passes through the said prism elements to provide the same number of component beams.

Claim 15

Illumination means according to claim 13 including a collimator through which said component beams pass to produce the said effective illumination condition in a printing plane.

Claim 16

Illumination means according to claim 14, including a collimator through which said component beams pass to produce the same illumination condition in a printing plane.

Claim 17

A method according to claim 15 in which the mean half-angle of the family of cones contained in the said envelope lies within the range 1 1/2 * to 5*.

Claim 18

Illumination means according to claim 3, in which the source comprises a single point source and a fixed composite reflector having a number of reflector elements arranged in an annular array such that light from the point source forms, by reflection in said reflector elements, the same number of component beams.

Claim 19

Apparatus for illuminating a substrate with a pattern determined by a shadow mask having transparent regions and opaque regions collectively defining a pattern to be illuminated on said substrate, comprising: a light source assembly of finite predetermined area having an effective brightness distribution incorporating a dark central region and a bright surrounding rim, said light source assembly including, in combination: a single point source of light of a given wavelength, a fixed composite optical arrangement having a plurality of optical elements in an annular array inclined such that light from said point source impinges on said optical elements and is formed thereby into a plurality of component beams in a corresponding annular array, and collimating lens means in the path of said plurality of component beams, a shadow mask having transparent regions and opaque regions collectively defining said pattern to be imaged on said substrate, and means supporting said mask at a selected position between said substrate and said light source assembly in the path of the light therefrom, said selected position lying at a distance from said substrate of the same order as the width of said transparent portions of said mask, whereby diffraction of light passing through said transparent regions in said mask results in diffraction fringes which substantially cancel each other out at least adjacent the edges of the pattern determined by said transparent regions, so that a sharp image of said shadow mask is obtained on said substrate when illuminated by said source assembly.

Claim 20

Apparatus for illuminating a substrate with a pattern determined by a shadow mask having transparent regions and opaque regions collectively defining a pattern to be illuminated on said substrate, comprising: a light source assembly of finite predetermined area having an effective brightness distribution incorporating a dark central region and a bright surrounding rim, said light source assembly including, in combination: a single point source of light of a given wavelength, a fixed composite optical arrangement having a plurality of optical elements in an annular array inclined such that light from said point source impinges on said optical elements and is formed thereby into a plurality of component beams in a corresponding annular array, and collimating lens means in the path of said plurality of component beams, a shadow mask having transparent regions and opaque regions collectively defining said pattern to be imaged on said substrate, and means supporting said mask at a selected position between said substrate and said light source assembly in the path of the light therefrom, said selected position lying at a distance from said substrate of the same order as the width of said transparent portions of said mask, whereby diffraction of light passing through said transparent regions in said mask results in diffraction fringes which substantially cancel each other out at least adjacent the edges of the pattern determined by said transparent regions, so that a sharp image of said shadow mask is obtained on said substrate when illuminated by said source assembly.

Claim 21

Illumination means according to claim 18, in which said optical arrangement comprises a fixed multiple prism comprising a number of prism elements arranged in an annular array, light from said point source passing through the said prism elements to provide the same number of component beams.

Claim 22

Illumination means according to claim 19, in which said prism comprises a number of identical adjacent prism elements of sector shape, each prism element tapering in thickness from a maximum at its vertex to a minimum at its outer edge.

Claim 23

Illumination means according to claim 20, in which the outer edges of the prism elements lie on a common circle.

Claim 24

Illumination means according to claim 20, in which each prism element is truncated at its vertex, said multiple prism having a central portion with plane parallel outer faces.

Claim 25

Illumination means according to claim 19, in which the two outer faces of each prism element are both inclined to the radial plane of the multiple prism.

Claim 26

Illumination means according to claim 23, in which the multiple prism comprises two parts, each ground to provide respective parts of said prism elements, and each having a plane radial face, said two parts being cemented together back-to-back at said plane faces with the parts of the prism elements in register with each other.

Claim 27

Illumination means according to claim 19, in which said multiple prism comprises at least six identical prism elements.

Claim 28

Illumination means according to claim 18, in which said optical elements are reflectors and are so arranged that they form virtual images of the said point light source in a common plane containing said point source.

Claim 29

Illumination means according to claim 18, including a stop arranged centrally of the annular array of reflector elements, preventing the direct passage of light through said array without reflection by the reflector elements.

Claim 30

Illumination means according to claim 18, including a fixed reflector between said array of optical elements and said collimator, the component beams emerging from said composite optical arrangement being deflected through substantially 90* by said fixed reflector before passing through said collimator.

Claim 33

The method according to claim 29 comprising the step of illuminating said shadow mask and substrate with light from a stationary source assembly of finite predetermined area and comprising: a single point source of light of a given wavelength, a fixed composite optical arrangement having a plurality of optical elements in an annular array inclined such that light from said point source impinges on said optical elements and is formed thereby into a plurality of component beams in a corresponding annular array, and lens means in the path of said plurality of component beams.

Claim 34

The method according to claim 29 wherein said given wavelength of light is substantially 0.4 microns and said mask is spaced from said substrate by substantially 9 microns.

Claim 35

The method according to claim 29, in which the source illuminates any point on the mask with radiation which lies between two cones having a common apex at said point and a common axis normal to the plane of the mask.

Claim 36

The method according to claim 32, in which said two cones have half-angles of 3 1/4 * and 4 3/4 *.