Wafer planarization using a uniform layer of material and method and apparatus for forming uniform layer of material used in semiconductor processing

• US 20020187650A1
• Filed: 05/28/2002
• Published: 12/12/2002
• Est. Priority Date: 09/02/1999
• Status: Active Grant

• Current Assignee: Micron Technology, Inc.
• Original Assignee: Micron Technology, Inc.
• Inventors: Gordon, Brian F., Blalock, Guy T., Stroupe, Hugh E.
• Granted Patent: US 6,624,089 B2
• Time in Patent Office: Days
• US Class Current: 438/760
• CPC Class Codes: B29C 2035/0827 using UV radiation
• CPC Class Codes: B29C 43/021 characterised by the shape of the surface
• CPC Class Codes: B29K 2023/16 EPM, i.e. ethylene-propylene copolymers; EPDM, i.e. ethylene-propylene-diene copolymers; EPT, i.e. ethylene-propylene terpolymers
• CPC Class Codes: B29K 2027/12 containing fluorine
• CPC Class Codes: B29K 2063/00 Use of EP, i.e. epoxy resins or derivatives thereof, as moulding material
• CPC Class Codes: B29L 2031/3061 Number plates
• CPC Class Codes: B29L 2031/7728 Disc-shaped records B29L2017/003
• CPC Class Codes: H01L 21/67092 Apparatus for mechanical treatment or grinding or cutting, see the relevant groups in subclasses B24B or B28D
• CPC Class Codes: Y10T 428/3154 Of fluorinated addition polymer from unsaturated monomers

Abstract

In connection with wafer planarization, an apparatus for forming a layer of material having a substantially uniform thickness and substantially parallel first and second major surfaces includes a pair of pressing elements and a stop. Each of the pair of pressing elements has a flat pressing surface. The pressing surfaces are opposed to one another and operable to compress a quantity of the material therebetween. The stop is positioned at least partially between the pressing surfaces and has a thickness substantially equal to the desired uniform thickness of the layer. The stop is positioned to establish a spacing between the flat pressing surfaces that is substantially equal to the thickness of the stop and thereby to the desired uniform thickness of the layer when the pressing elements engage the stop. As a result, engagement of the stop by the pressing surfaces during pressing of the material forms a layer of the material of substantially uniform thickness with substantially parallel major surfaces formed by the flat pressing surfaces. The layer is then used in semiconductor processing to provide a flat surface on a layer of a substrate assembly, thereby enhancing the planarization of the substrate assembly.

Claims

1. In semiconductor processing, an apparatus for compressing material into a layer of substantially uniform thickness for use in forming a flat surface on a substrate assembly, the material being of a type which is capable of being heated to a temperature where the material flows without melting, the apparatus comprising:

first and second pressing elements, each pressing element having a respective pressing surface, the pressing surfaces being opposed to one another;

a shim positioned between the pressing surfaces, the shim having an open center area and a stop portion having a thickness equal to the desired uniform thickness of the layer;

a heater that heats the material to a temperature where the material flows without melting; and

a compression force applicator coupled to each of the pair of pressing elements, the compression force applicator moving at least a first pressing surface of the pair of pressing surfaces toward the other of the pressing surfaces and against the stop portion of the shim to press a quantity of the material positioned between the pair of pressing surfaces and within the open center area of the shim into the layer having the substantially uniform thickness.

2. The apparatus of claim 1 wherein the compression force applicator moves only the first pressing surface during pressing of the material.

3. The apparatus of claim 1 wherein the compression force applicator comprises a plurality of biasing elements coupled to the first and second opposed pressing surfaces so as to bias the pressing surfaces toward one another.

4. The apparatus of claim 1 wherein the compression force applicator comprises a plurality of elongated fasteners each interconnecting the respective pressing elements and the shim, the pressing element which includes said first pressing surface being slidably coupled to the elongated fasteners such that said first pressing surface is slidable toward the other of the pressing surfaces, and a plurality of biasing spring elements coupled to said pressing elements to bias said first pressing surface toward the other of the pressing surfaces.

5. An apparatus for use in forming a sheet of material for use in semiconductor processing, comprising:

an annular shim having a border portion and a plurality of projections extending inwardly from the border portion, the projections having a first thickness, a shim open area positioned inwardly of the projections, overflow material recesses being positioned between the projections and communicating with the shim open area; and

first and second pressing surfaces positioned on opposite sides of the shim, the first and second pressing surfaces contacting the shim at least along the projections to compress material on at least one of the first and second pressing surfaces within the shim open area to a substantially uniform thickness equal to the first thickness,

wherein any material in excess of the volume defined by the shim opening and the first and second pressing surfaces passes outwardly from the shim opening and into the recesses.

6. The apparatus of claim 5 wherein the first and second pressing surfaces each comprise an optical flat.

7. The apparatus of claim 6 further comprising a pressure applicator coupled to the first and second pressing surfaces for pressing together the first and second pressing surfaces.

8. The apparatus of claim 5 wherein the projections are of a triangular shape.

9. The apparatus of claim 5 including an oven which receives at least the first and second pressing surfaces and shim for heating the material during pressing.

10. In semiconductor processing, an apparatus for forming a layer of a material having a substantially uniform thickness and substantially parallel first and second major surfaces, the material being for use in producing a flat on a semiconductor, the apparatus having:

a pair of pressing elements each having a flat pressing surface, the pressing surfaces being opposed to one another and operable to compress a quantity of the material therebetween;

a stop positioned at least partially between the pressing surfaces, the stop having a thickness substantially equal to the desired uniform thickness of the layer and being positioned to establish a spacing between the flat pressing surfaces which is substantially equal to the thickness of the stop and thereby to the desired uniform thickness of the layer when the pressing elements engage the stop; and

whereby engagement of the stop by the pressing surfaces during pressing of the material forms a layer of the material for use in producing a flat on a semiconductor, the layer of material being of substantially uniform thickness with substantially parallel major surfaces formed by the flat pressing surfaces.

12. A release member according to claim 10 wherein the first and second major surfaces are at least within fifty angstroms of being flat.

11. A release member for preventing a surface layer on a semiconductor substrate assembly from adhering to a surface of a press, the release member comprising:

a body in the form of a sheet having first and second major surfaces;

the first and second major surfaces each being within one hundred angstroms of being flat;

the first and second major surfaces being at least within five millionths of an inch of being parallel to one another;

the body being of a material which releases from the press surface when engaged by the press surface; and

whereby when the first major surface is pressed against the press surface and the second major surface is positioned against the surface layer on the semiconductor substrate assembly, the release member prevents the layer on the semiconductor substrate assembly from adhering to the press surface.

13. A release member according to claim 11 wherein the surface layer on the semiconductor substrate assembly contains a layer of epoxy.

15. A sheet according to claim 14 wherein the material is ultraviolet transmissive FEP.

16. A sheet according to claim 14 wherein the material is PTFE.

18. A stop according to claim 17 wherein the stop portion comprises a plurality of projecting fingers extending inwardly into the central portion.

19. A stop according to claim 17 wherein the stop portion is about twenty-thousandths of an inch thick.

20. A stop according to claim 18 wherein the fingers comprise triangular teeth extending radially inwardly into the central portion from the annulus.

21. A stop according to claim 18 wherein each of the fingers comprises a tooth which is triangular in shape with an apex positioned inwardly of a base, the tooth having first and second sides intersecting one another at the apex, the first and second sides defining an acute angle therebetween.

22. A stop according to claim 21 wherein the acute angle is about thirty degrees.

24. The method of claim 23 wherein the heating act comprises heating the material until the material transitions to a plastic state without melting the material.

25. The method of claim 23 wherein the substrate assembly has an epoxy layer and the applying act comprises applying one of the first and second major surfaces of the layer to a surface of the epoxy layer of the substrate assembly.

27. The method of claim 26 further comprising heating the layer.

28. The method of claim 26 wherein the material is FEP and comprising heating the layer to a temperature at which the layer becomes plastic but remains below the melting point temperature.

29. The method of claim 26 wherein the material is PTFE and comprising heating the layer to a temperature at which the layer becomes plastic but remains below the melting point temperature.

30. The method of claim 26 further comprising removing excess material from the peripheries of the first and second pressing surfaces and thereafter allowing the formed layer to cool.

14. A sheet of a material used in producing a flat on a substrate assembly, the sheet of material being capable of flowing without melting when heated to a temperature below the melting point of the material, the sheet comprising:

a body having a central region with first and second opposed major working surfaces;

the first and second major working surfaces each being within fifty angstroms of being flat and being at least within five millionths of an inch of being parallel to one another.

17. In an apparatus for producing a sheet of material for use in semiconductor processing, a stop for positioning between first and second pressing elements to limit the extent to which the pressing elements approach one another during a pressing operation, the stop comprising a reinforcing section of a first thickness and a stop section of a second thickness which is less than the first thickness;

the reinforcing section comprising a closed geometric shape which bounds a central portion of the stop; and

the stop portion extending inwardly into the central portion from the reinforcing portion, the stop portion spanning less than the entire area of the central portion to provide a void in the central portion.

23. A method of forming a layer of a material on a substrate assembly comprising:

heating the material;

pressing the material between first and second flat pressing surfaces;

disposing a stop between the first and second pressing surfaces to limit the extent to which the first and second pressing surfaces approach one another during pressing to thereby form a layer of a substantially uniform thickness having first and second major surfaces with the first and second major surfaces being formed by the flat pressing surfaces; and

applying one of the first and second major surfaces to a surface of a substrate assembly.

26. A method of forming a layer of material for use in forming a flat on a semiconductor, the material having first and second major surfaces which are substantially parallel to one another and substantially flat, the method comprising:

pressing first and second optical flats toward one another;

disposing a shim at least partially between the optical flats to limit the extent to which the optical flats approach one another and to thereby establish the uniform thickness of the layer;

providing an open central region in the shim for receiving the material to be formed onto the layer; and

flowing excess material outwardly from the central region into pockets provided in the shim during pressing.

31. A semiconductor substrate assembly in production comprising:

a semiconductor flat comprised of semiconductor material and having a first surface with at least one surface feature formed therein;

an epoxy layer covering the first surface and the surface feature, the epoxy layer having a covering material engaging surface spaced from the first surface;

a cover layer overlying the covering material engaging surface of the epoxy layer, the cover layer having first and second major opposed surfaces with a thickness between the first and second major opposed surfaces which is within at least five millionths of an inch of being uniform, the first and second major opposed surfaces being within one hundred angstroms of being flat.

32. The semiconductor substrate assembly of claim 31 wherein the cover layer is formed of FEP.

33. The semiconductor substrate assembly of claim 31 wherein the cover layer is formed from PTFE.

34. The semiconductor substrate assembly of claim 31 wherein the substantially uniform thickness of the cover layer is about twenty-thousandth of an inch.

35. The semiconductor substrate assembly of claim 31 wherein the first and second major surfaces are within fifty angstroms of being flat.

36. The semiconductor substrate assembly of claim 31 wherein the cover layer is transparent to ultraviolet radiation.

38. A method according to claim 37 including the step of curing the epoxy layer through the sheet of material.

37. A method of planarizing a semiconductor wafer comprising:

applying one major working surface of a sheet of material having first and second opposed major working surfaces to an epoxy layer of a substrate assembly, the first and second major working surfaces each being within fifty angstroms of being flat and being at least within five millionths of an inch of being parallel to one another;

pressing an optical flat against the sheet of material and substrate assembly to planarize the epoxy layer; and

removing the sheet of material.