US5162251A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method for making thinned charge-coupled devices
Assignee: Goodrich Corp
•
Filing: 1991-03-18
•
Granted: 1992-11-10
•
Expires: 2011-03-18
Abstract
Abstract A standard thick silicon charge-coupled device (FIG. 1A) has its pixel face mounted to a transparent, optically flat glass substrate using a thin layer of thermoset epoxy. The backside silicon of the charge-coupled device is thinned to 10 ±0.5 um using a two-step chemi-mechanical process. The bulk silicon is thinned to 75 um with a 700 micro-grit aluminium oxide abrasive and is then thinned and polished to 10 um using 80 nm grit colloidal silica. Access from the backside to the aluminum bonding pads (36 of FIG. 5) of the device is achieved by photolithographic patterning and reactive ion etching of the silicon above the bonding pads. The charge-coupled device is then packaged and wire-bonded in a structure which offers support for the silicon membrane and allows for unobstructed backside illumination.
Inventors
- 👤 Richard R. Poole
- 👤 Enrique Garcia
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-05 14:07
CPC Classifications
H; H10; H10F; H10F39/00; H10F39/011; H10F39/026; H10P; H10P52/00; H10P52/40; H10P52/402; H10F30/00; H10F30/20; H10F30/21; H10F30/28; H10F30/2823; H10F39/80; H10P50/00; H10P50/60; H10P50/64; H10P50/642; Y; Y10; Y10S; Y10S148/00; Y10S148/012; Y10S148/135; Y10S438/00; Y10S438/977
Claims Analysis
Total Claims: 19
Claim 1
Independent Claim
114 words
A method for forming a thinned charge-coupled device, said method comprising the steps of: obtaining a charge-coupled device having a thickness greater than a preselected thickness, said charge-coupled device having a front pixel side and a backside; uniformly and permanently bonding, under a vacuum, said front side of said charge-coupled device to an optically flat glass substrate so that said charge-coupled device is supported while said backside is thinned, said optically flat glass substrate having front and back faces said front face being bonded to said front side of said charge-coupled device; and thinning said charge-coupled device to said preselected thickness using a two-step chemi-mechanical process including a lapping step and a polishing step.
Claim 2
Independent Claim
114 words
A method for forming a thinned charge-coupled device, said method comprising the steps of: obtaining a charge-coupled device having a thickness greater than a preselected thickness, said charge-coupled device having a front pixel side and a backside; uniformly and permanently bonding, under a vacuum, said front side of said charge-coupled device to an optically flat glass substrate so that said charge-coupled device is supported while said backside is thinned, said optically flat glass substrate having front and back faces said front face being bonded to said front side of said charge-coupled device; and thinning said charge-coupled device to said preselected thickness using a two-step chemi-mechanical process including a lapping step and a polishing step.
Claim 3
Dependent Claim
39 words
A method as described in claim 1, wherein said charge-coupled device and said optically flat glass substrate are bonded together so as to effect parallelism between pixels of the charge-coupled device and an optically flat surface of the substrate.
Claim 4
Dependent Claim
23 words
A method as described in claim 2, wherein said optically flat surface serves as a reference plane from which device thinning is controlled.
Claim 5
Dependent Claim
25 words
A method as described in claim 1, wherein the lapping step is used to reduce the thickness of the charge-coupled device to approximately 75 um.
Claim 6
Dependent Claim
24 words
A method as described in claim 4, wherein the lapping step is accomplished using an alumina grit having an approximate 700 micro-grit particle size.
Claim 7
Dependent Claim
18 words
A method as described in claim 1, wherein the polishing step is achieved using a colloidal silica abrasive.
Claim 8
Dependent Claim
19 words
A method as described in claim 6, wherein the colloidal silica has a particle size of approximately 80 nm.
Claim 9
Dependent Claim
19 words
A method as described in claim 7, wherein colloidal silica is used in conjunction with a polyurethane polishing pad.
Claim 10
Dependent Claim
33 words
A method as described in claim 1, wherein the charge-coupled device is uniformly bonded to a transparent optically flat glass substrate having a coefficient of expansion matched to that of the charge-coupled device.
Claim 11
Dependent Claim
24 words
A method as described in claim 9, wherein the charge-coupled device is uniformly bonded to the optically flat glass substrate using a thermoset epoxy.
Claim 12
Dependent Claim
37 words
A method as described in claim 1, additionally comprising the step of, after thinning said charge-coupled device, removing material from the backside of the charge-coupled device using etching techniques to expose bonding pads embedded in the device.
Claim 13
Dependent Claim
28 words
A method as described in claim 11, wherein the backside of the thinned charge-coupled device is photolithographically patterned and the etching is achieved using an ion etching technique.
Claim 14
Dependent Claim
31 words
A method as described in claim 12, additionally comprising the steps of mounting the thinned charge-coupled device in a package and wire-bonding the bonding pads to contact pins of said package.
Claim 15
Dependent Claim
28 words
A method as described in claim 1, wherein the glass substrate includes front and back faces, and the method additionally comprises the step of polishing said front faces.
Claim 16
Dependent Claim
51 words
A method as described in claim 1, wherein the charge-coupled device is mounted to the glass substrate in a bonding fixture and an interface between the charge-coupled device and the substrate is inspected under monochromatic light to detect the existence of particles by viewing a fringe pattern formed by the light.
Claim 17
Dependent Claim
112 words
A method as described in claim 15, wherein said bonding step is accomplished in a vacuum fixture, and the method includes the steps of: placing the charge-coupled device/substrate combination in the vacuum fixture; depositing the epoxy on the substrate adjacent the charge-coupled device; evacuating the fixture, so that the vacuum removes all air from between the charge-coupled device and the glass substrate and volatile organics from the epoxy; warming the charge-coupled device/substrate; moving the charge-coupled device on the glass substrate to the epoxy, causing the epoxy to be contacted and drawn under the charge-coupled device by capillary action; releasing the vacuum; and heating the charge-coupled device/substrate combination to partially cure the epoxy.
Claim 18
Dependent Claim
43 words
A method as described in claim 16, additionally comprising the steps of: inspecting the charge-coupled device/substrate combination and the epoxy layer for voids and unwanted particles; and thereafter finally curing the epoxy using a pneumatic press heater and a preselected time-temperature cure schedule.
Claim 19
Dependent Claim
26 words
A method as described in claim 1, additionally comprising the step of measuring the thickness of the thinned charge-coupled device using a laser thickness measuring instrument.
References Cited (Backward Citations)
US3965568A
Cited
US4197633A
Cited
US4321747A
Cited
US4266334A
Cited
EP0032565A1
Cited
US4465549A
Cited
US4876222A
Cited
US4814283A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1995-11-10 | 1996-05-11 | 1996-11-10 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1999-11-10 | 2000-05-11 | 2000-11-10 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2003-11-10 | 2004-05-11 | 2004-11-10 | $7700.00 | Window Closed / Lapsed |