Method to form code marks on mask ROM products

{
  "publication_number": "US6623911B1",
  "country": "US",
  "kind": "B1",
  "title": "Method to form code marks on mask ROM products",
  "abstract": "A method for forming a clear code mark that is independent of backend planarization by adding an extra exposing step to the normal photolithography process is described. A layer to be patterned is provided on a substrate. A photoresist layer is coated overlying the layer to be patterned. The photoresist layer is first exposed through a code mask and second exposed through a patterning mask. The photoresist layer is developed to form a photoresist mask having a code mark pattern from the code mask and a device pattern from the patterning mask. The layer to be patterned is etched away where it is not covered by the photoresist mask to form simultaneously device structures and a code mark in the fabrication of an integrated circuit device.",
  "claims": [
    "1. A method of forming a code mark in the fabrication of an integrated circuit device comprising: providing a layer to be patterned on a substrate; coating a photoresist layer overlying said layer to be patterned; exposing said photoresist layer through a code mask wherein said exposing comprises a first low energy and defocused conditions; exposing said photoresist layer through a patterning mask wherein said exposing comprises a second energy higher than said first energy wherein said first energy is less than half of said second energy; developing said photoresist layer to form a photoresist mask having a code mark pattern from said code mask and a device pattern from said patterning mask; and etching away said layer to be patterned where it is not covered by said photoresist mask to form simultaneously device structures and said code mark in the fabrication of said integrated circuit device.",
    "2. The method according to claim 1 wherein said layer to be patterned is a metal layer and wherein said device structures are metal lines.",
    "3. The method according to claim 1 wherein said layer to be patterned is a dielectric layer and wherein said device structures are vias.",
    "4. The method according to claim 1 wherein said code mask comprises a code window pattern and a code mark pattern and wherein said low energy and said defocused condition causes said code window pattern to be strongly under-developed while said code mark pattern is well-developed whereby said code window pattern is not transferred to said device structures.",
    "5. A method of forming a code mark in the fabrication of an integrated circuit device comprising: providing a layer to be patterned on a substrate; coating a photoresist layer overlying said layer to be patterned; exposing said photoresist layer through a code mask wherein said exposing comprises a first energy and defocused conditions; exposing said photoresist layer through a patterning mask wherein said exposing comprises a second energy higher than said first energy; developing said photoresist layer to form a photoresist mask having a code mark pattern from said code mask and a device pattern from said patterning mask; and etching away said layer to be patterned where it is not covered by said photoresist mask to form simultaneously device structures and said code mark in the fabrication of said integrated circuit device.",
    "6. The method according to claim 5 wherein said layer to be patterned is a metal layer and wherein said device structures are metal lines.",
    "7. The method according to claim 5 wherein said layer to be patterned is a dielectric layer and wherein said device structures are vias.",
    "8. The method according to claim 5 wherein said first energy is between less than half of said second energy.",
    "9. The method according to claim 5 wherein said code mask comprises a code window pattern and a code mark pattern and wherein said first energy smaller than said second energy and said defocused condition cuases said code window pattern to be strongly under-developed while said code mark pattern is well-developed whereby said code window pattern is not transferred to said device structures.",
    "10. A method of forming a code mark in the fabrication of an integrated circuit device comprising: providing a layer to be patterned on a substrate; coating a photoresist layer overlying said layer to be patterned; exposing said photoresist layer through a code mask wherein said code mask comprises a code window pattern and a code mark pattern wherein said exposing comprises a first energy and defocused conditions whereby said code window pattern is strongly under-developed while said code mark pattern is well-developed; exposing said photoresist layer through a patterning mask wherein said exposing comprises a second energy higher than said first energy; developing said photoresist layer to form a photoresist mask having a code mark pattern from said code mask and a device pattern from said patterning mask; and etching away said layer to be patterned where it is not covered by said photoresist mask to form simultaneously device structures and said code mark wherein said code window pattern is not transferred to said device structures in the fabrication of said integrated circuit device.",
    "11. The method according to claim 10 wherein said layer to be patterned is a metal layer and wherein said device structures are metal lines.",
    "12. The method according to claim 10 wherein said layer to be patterned is a dielectric layer and wherein said device structures are vias.",
    "13. The method according to claim 10 wherein said first energy is less than half of said second energy."
  ],
  "cpc": [
    "H10W 46/00",
    "G03F 7/203",
    "H10W 46/401",
    "H10W 46/501"
  ],
  "assignees": [
    "TAIWAN SEMICONDUCTOR MFG"
  ],
  "filing_date": "2001-09-17",
  "publication_date": "2003-09-23",
  "grant_date": "2003-09-23",
  "priority_date": "2001-09-17",
  "application_number": "US-95352401-A",
  "family_id": "28042474",
  "citations": [
    "US5051374A",
    "US5316966A",
    "US5393233A",
    "US5576236A",
    "US5668030A",
    "US5705404A",
    "US6187638B1",
    "US6312876B1"
  ]
}