US5679267A
Expired / Lapsed
US
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Dual etching of ceramic materials with an elevated thin film
Assignee: L3 Technologies Inc
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Filing: 1996-01-16
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Granted: 1997-10-21
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Expires: 2016-01-16
Abstract
Abstract A novel reticulated array comprises islands of ceramic (e.g. BST 40) which are fabricated from novel materials using unique methods of patterning. A shallow etch stop trench (46) is first ion milled around each ceramic island on the front side and then filled with an etch step material (e.g. parylene 48). An optical coat (e.g transparent metal layer 54, transparent organic layer 56 and conductive metallic layer 58) is elevated above the etch step material by an elevation layer (e.g. polyimide 49). For some applications, it has been experimentally verified that there is no loss, and sometimes a measured increase, in optical efficiency when the optical coating is not planar in topology. Novel fabrication methods also provide for the convenient electrical and mechanical bonding of each of the massive number of ceramic islands to a signal processor substrate (e.g. Si 86) containing a massive array of sensing circuits.
Inventors
- 👤 James F. Belcher
- 👤 Robert A. Owen
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 15:32
CPC Classifications
H; H10; H10N; H10N15/00; H10N15/10; H10F; H10F39/00; H10F39/10; H10F39/12; H10F39/18; H10F39/184; H10F39/1843
Claims Analysis
Total Claims: 23
Claim 1
Independent Claim
262 words
A method of forming a reticulated infrared array detector said method comprising steps: (a) providing a ceramic substrate having a front side and a back side; (b) forming a first mask layer on said front side of said ceramic substrate, etching a first pattern partially into said front side of said ceramic substrate, and removing said first mask layer, thereby forming etch stop trenches having said first pattern; (c) filling said etch stop trenches with an etch stop material; (d) forming an elevation layer having a second pattern on said front side of said ceramic substrate, said elevation layer aligned with said etch stop trenches and covering at least said etch stop material in said etch stop trenches; (e) depositing an optical coating on said front side of said ceramic substrate and on said elevation layer, thereby forming elevated portions of said optical coating above said etch stop trenches; (f) forming a backside mask layer on said back side of said ceramic substrate, etching a third pattern into said back side of said ceramic substrate, and removing said backside mask layer, said third pattern the same as said first pattern, and aligned with said etch stop trenches on said front side, thereby forming cavities extending down to and into said etch stop material, but not extending to said optical coating; (g) removing said etch stop material; and (h) removing said elevation layer, thereby forming isolated islands of said ceramic substrate connected by said optical coating, whereby the optical coating has not been exposed to the etching processes of steps (b) and (f).
Claim 2
Independent Claim
262 words
A method of forming a reticulated infrared array detector said method comprising steps: (a) providing a ceramic substrate having a front side and a back side; (b) forming a first mask layer on said front side of said ceramic substrate, etching a first pattern partially into said front side of said ceramic substrate, and removing said first mask layer, thereby forming etch stop trenches having said first pattern; (c) filling said etch stop trenches with an etch stop material; (d) forming an elevation layer having a second pattern on said front side of said ceramic substrate, said elevation layer aligned with said etch stop trenches and covering at least said etch stop material in said etch stop trenches; (e) depositing an optical coating on said front side of said ceramic substrate and on said elevation layer, thereby forming elevated portions of said optical coating above said etch stop trenches; (f) forming a backside mask layer on said back side of said ceramic substrate, etching a third pattern into said back side of said ceramic substrate, and removing said backside mask layer, said third pattern the same as said first pattern, and aligned with said etch stop trenches on said front side, thereby forming cavities extending down to and into said etch stop material, but not extending to said optical coating; (g) removing said etch stop material; and (h) removing said elevation layer, thereby forming isolated islands of said ceramic substrate connected by said optical coating, whereby the optical coating has not been exposed to the etching processes of steps (b) and (f).
Claim 3
Dependent Claim
14 words
The method according to claim 1, wherein said ceramic substrate is barium strontium titanate.
Claim 4
Dependent Claim
45 words
The method according to claim 1, said method further comprising depositing a protective metal layer on said front side of said ceramic substrate before said step of etching said first pattern, and then etching said metal layer during said step of etching said first pattern.
Claim 5
Dependent Claim
108 words
The method according to claim 1, wherein said first mask layer is a first tri-level resist, and said step of forming said first mask layer further comprises: forming a first thick photoresist layer on said front side of said ceramic substrate; forming a first metal mask layer on said first thick photoresist layer; forming a first thin photoresist layer on said first metal mask layer; patterning said first thin photoresist layer using photolithography; patterning said first metal mask layer using said first thin photoresist layer as a first etch mask; and patterning said first thick photoresist layer using said first metal mask layer as a second etch mask.
Claim 6
Dependent Claim
27 words
The method according to claim 1, wherein said etch stop material is selected from the group consisting of: photoresist, silicon oxide, polyimide, parylene, epoxy, and silicon nitride.
Claim 7
Dependent Claim
32 words
The method according to claim 1, said step (c) further comprising: planarizing said etch stop material and said front side of said ceramic substrate after said filling of said etch stop trenches.
Claim 8
Dependent Claim
40 words
The method according to claim 6, said method further comprising depositing a protective metal layer on said front side of said ceramic substrate after said step of planarizing said etch stop material and said front side of said ceramic substrate.
Claim 9
Dependent Claim
54 words
The method according to claim 1, said step (d) further comprising: depositing a first organic layer on said front side of said ceramic substrate; forming a second mask layer on said first organic layer; etching said first organic layer to form said elevation layer having said second pattern; and removing said second mask layer.
Claim 10
Dependent Claim
21 words
The method according to claim 1, wherein said elevation layer is selected from the group consisting of: photoresist, parylene, and polyimide.
Claim 11
Dependent Claim
33 words
The method according to claim 1, wherein said steps (c) and (d) are performed at the same time, and said etch stop material and said elevation layer are composed of the same material.
Claim 12
Dependent Claim
63 words
The method according to claim 1, wherein said optical coating comprises multiple layers, and said step of depositing said optical coating further comprises: depositing a conductive metallic layer on said front side of said ceramic substrate and on said elevation layer; depositing a transparent organic layer on said conductive metallic layer; and depositing a thin transparent metal layer on said transparent organic layer.
Claim 13
Dependent Claim
27 words
The method according to claim 11, wherein said conductive metallic layer is NiCr, said transparent organic layer is parylene, and said thin transparent metal layer is NiCr.
Claim 14
Dependent Claim
42 words
The method according to claim 1, wherein a top surface of said optical coating opposite said ceramic substrate is mounted to a removable carrier after said step of depositing said optical coating wherein said carrier provides mechanical support for subsequent process steps.
Claim 15
Dependent Claim
32 words
The method according to claim 1, said method further comprising thinning said ceramic substrate by mechanically polishing said back side of said ceramic substrate before said step of etching said third pattern.
Claim 16
Dependent Claim
45 words
The method according to claim 14, said method further comprising depositing a thin electrical contact on said back side of said ceramic substrate after said step of thinning said ceramic substrate, and etching said thin electrical contact during said step of etching said third pattern.
Claim 17
Dependent Claim
13 words
The method according to claim 15, wherein said islands form infrared sensitive capacitors.
Claim 18
Dependent Claim
19 words
The method according to claim 15, wherein said thin electrical contact comprises two or more layers, and comprises indium.
Claim 19
Dependent Claim
108 words
The method according to claim 1, wherein said backside mask layer is a second tri-level resist, and said step of forming said backside mask layer further comprises: forming a second thick photoresist layer on said back side of said ceramic substrate; forming a second metal mask layer on said second thick photoresist layer; forming a second thin photoresist layer on said second metal mask layer; patterning said second thin photoresist layer using photolithography; patterning said second metal mask layer using said second thin photoresist layer as a third etch mask; and patterning said second thick photoresist layer using said second metal mask layer as a fourth etch mask.
Claim 20
Dependent Claim
30 words
The method according to claim 1, said step (f) further comprising forming said cavities extending down to and partially into said elevation layer, but not extending to said optical coating.
Claim 21
Dependent Claim
19 words
The method according to claim 1, wherein said steps of etching said first and third patterns comprise ion milling.
Claim 22
Dependent Claim
33 words
The method according to claim 1, wherein said elevation layer and said etch stop material are composed of the same material, and said steps (g) and (h) are performed at the same time.
Claim 23
Dependent Claim
32 words
The method according to claim 1, said method further comprising bump bonding said back side of said ceramic substrate to a signal processing substrate after said step of removing said elevation layer.
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