Source: https://patents.google.com/patent/US20050074974
Timestamp: 2018-02-18 08:41:58
Document Index: 211878320

Matched Legal Cases: ['application No. 60', 'application No. 60', 'application No. 60', 'application No. 60', 'application No. 60', 'application No. 60', 'application No. 60', 'application No. 60', 'application No. 60', 'application No. 60', 'application No. 60', 'application No. 60', 'application No. 60', 'application No. 60']

US20050074974A1 - Semiconductor manufacturing using optical ablation - Google Patents
US20050074974A1
US20050074974A1 US10957271 US95727104A US20050074974A1 US 20050074974 A1 US20050074974 A1 US 20050074974A1 US 10957271 US10957271 US 10957271 US 95727104 A US95727104 A US 95727104A US 20050074974 A1 US20050074974 A1 US 20050074974A1
US7115514B2 (en )
This application claims priority to U.S. Provisional Application: entitled “Semiconductor Manufacturing Using Optical Ablation,” Ser. No. 60/508,136, filed Oct. 2, 2003 (Docket No. ABI-1025).
Laser machining can remove ablatively material by disassociate the surface atoms and melting the material. Laser ablation is efficiently done with a beam of short pulses (generally a pulse-duration of three picoseconds or less). Techniques for generating these ultra-short pulses (USP) are described,, e.g., in a book entitled “Femtosecond Laser Pulses” (C. Rulliere, editor), published 1998, Springer-Verlag Berlin Heidelberg New York. Generally large systems, such as Ti:Sapphire, are used for generating ultra-short pulses (USP).
Optical ablation can also be used as a method of removing material from surface of a semiconductor wafer including the steps of generating an initial wavelength-swept-with-time optical pulse in an optical pulse generator, amplifying the initial pulse, compressing the amplified pulse to a duration of less than about 10 picoseconds and applying the compressed optical pulse to the wafer surface, to remove material from wafer surface. The semiconductor wafer may have a substrate of silicon, GaAs, InP or combinations thereof. However, persons of ordinary skill in the art will recognize the semiconductor wafer substrate may be constructed of a variety of materials. The amplifying may be done with either a fiber-amplifier,, e.g., a erbium-doped fiber amplifier (or EDFA) or a Cr:YAG amplifier or a SOA (semiconductor optical amplifier). A semiconductor optical amplifier (SOA) preamplifier may be used to amplify the selected pulses before introduction into the optical amplifier. A sub-picosecond pulses of between about ten (10) picoseconds and one (1) nanosecond, followed by pulse selection, with the selected pulses amplified by an optical-amplifier. The optical amplifier may be an erbium-doped fiber amplifier (or EDFA) amplifier and compressed by an air-path between gratings compressor (e.g., a Treacy grating compressor), with the compression creating a sub-picosecond ablation pulse. Alternatively, the optical amplifier may be a Cr:YAG amplifier and compressed by an air-path between gratings compressor (e.g., a Treacy grating compressor), with the compression creating a sub-picosecond ablation pulse. Other embodiments may use multiple amplifiers.
Optical-amplifier and air-path between gratings compressor combination can be used to amplify and compress,, e.g., the amplified pulses between about ten picoseconds and one nanosecond. Alternatively, the amplifying and compressing can be done with a chirped fiber compressor combination,, e.g., the initial pulses between one and twenty nanoseconds. In one embodiment, the optical amplifier may be an erbium-doped fiber amplifier, and the air-path between gratings compressor,, e.g., a Treacy grating compressor. In one embodiment, more than one optical amplifier is used in parallel. In another embodiment, more than one semiconductor optical amplifier is used in parallel. Additionally, one compressor may be used in conjunction with one or more optical amplifiers.
Generally, the optically-pumped pulse amplifiers are optically-pumped continuous wave (CW) and are amplifying perhaps 100,000 times per second in 1 nanosecond pulses. Alternately, non-CW-pumping might be used in operating amplifiers, with amplifiers operate in a staggered fashion,, e.g., one on for a first half-second period and then turned off for a second half-second period, and another amplifier, dormant during the first-period, turned on during the second period, and so forth, to spread the heat load.
Many optically-pumped pulse amplifiers have a maximum power of four (4) MW, and thus a ten (10) microjoule-ablation pulse could be as short as two (2) picoseconds. Thus, a ten (10) picoseconds, ten (10) microjoule pulse, at 500 kHz (or 50 microjoule with 100 kHz), and, if heating becomes a problem, operating in a train mode and switching optically-pumped pulse amplifiers. For example, optically-pumped pulse amplifier system may rotate the operation of ten (10) optically-pumped pulse amplifiers such that only five (5) were operating at any one time (e.g., each on for {fraction (1/10)}th of a second and off for {fraction (1/10)}th of a second). In another embodiment, ten optically-pumped pulse amplifiers may be used with time spaced inputs,, e.g., by one (1) ns, to give a train of one to ten pulses. One example includes a five (5) W amplifiers operating at one hundred (100) kHz and fifty (50) microjoules this could step between one hundred (100) kHz and one (1) MHz. With 50% post-amplifier optical efficiency and fifty (50) microjoules, to get six (6) Joule per square centimeter on the target, the spot size would be about twenty (20) microns.
These optical amplifiers can be in systems described, operated, controlled, and/or used in systems in generally the same manner as the fiber amplifier of the four co-pending and co-owned applications noted below by docket number, title and provisional number, were filed May 20, 2003 and are hereby incorporated by reference herein: Docket number ABI-1 Laser Machining provisional application No. 60/471,922; ABI-4 “Camera Containing Medical Tool,” provisional application No. 60/472,071; ABI-6 “Scanned Small Spot Ablation With A High-Rep-Rate” provisional application No. 60/471,972; ABI-7 “Stretched Optical Pulse Amplification and Compression,” provisional application No. 60/471,971. These amplifiers can be controlled and/or used in systems in generally the same manner as the fiber amplifier of the eleven co-pending applications noted below by docket number, title and provisional number, were filed Aug. 11, 2003 and are hereby incorporated by reference herein: ABI-8 “Controlling Repetition Rate Of Fiber Amplifier”—provisional application No. 60/494,102; ABI-9 “Controlling Pulse Energy Of A Fiber Amplifier By Controlling Pump Diode Current” provisional application No. 60/494,275; ABI-10 “Pulse Energy Adjustment For Changes In Ablation Spot Size” provisional application No. 60/494,274; ABI-11 “Ablative Material Removal With A Preset Removal Rate or Volume or Depth” provisional application No. 60/494,273; ABI-12 “Fiber Amplifier With A Time Between Pulses Of A Fraction Of The Storage Lifetime”; ABI-13 “Man-Portable Optical Ablation System” provisional application No. 60/494321; ABI-14 “Controlling Temperature Of A Fiber Amplifier By Controlling Pump Diode Current” provisional application No. 60/494,322; ABI-15 “Altering The Emission Of An Ablation Beam for Safety or Control” provisional application No. 60/494,267; ABI-16 “Enabling Or Blocking The Emission Of An Ablation Beam Based On Color Of Target Area” provisional application No. 60/494,172; ABI-17 “Remotely-Controlled Ablation of Surfaces” provisional application No. 60/494,276 and ABI-18 “Ablation Of A Custom Shaped Area” provisional application No. 60/494,180. These amplifiers can be controlled and/or used in systems in generally the same manner as the fiber amplifier of the two co-pending applications noted below by docket number and, title that were filed on Sep. 12, 2003: co-owned ABI-20 “Spiral-Laser On-A-Disc” inventor—Richard Stoltz; and partially co-owned ABI-21 “Laser Beam Propagation in Air” inventors Jeff Bullington and Craig Siders.
1. A method of removing material from the surface of a semiconductor wafer comprising the steps of:
compressing the amplified pulse to a duration of less than about 10 picoseconds; and
applying the compressed optical pulse to the wafer surface, to remove material from the wafer surface.
2. The method of claim 1, wherein the wafer has a silicon, GaAs, or InP substrate.
3. The method of claim 1, wherein the amplifying is done with one or more fiber-amplifier, one or more SOA or combinations thereof.
4. The method of claim 1, wherein the ablation is done in a line to give minimal-pressure ablation scribing, wherein stress-increasing scratching of the surface is reduced.
5. The method of claim 1, wherein surface material is removed, wherein the surface cleaning.
6. The method of claim 1, further comprising the step of sensing the composition of material being removed.
7. The method of claim 6, wherein the composition of material being sensed is analyzed to determine when the ablation reaches an indication layer.
8. The method of claim 1, the optical ablation of material removal is used to replace a dry-etching step, whereby hard to materials such as copper or noble metals can be conveniently patterned.
9. The method of claim 1, wherein the step of amplifying uses one or more optical amplifiers in a train mode.
10. The method of claim 1, wherein the compressed optical pulse is generally circular with an area of between about 1 and 50 micron in diameter when applied to the surface.
11. The method of claim 1, wherein the step of amplifying is done with a fiber-amplifier and the step of compressing is done with an air-path between gratings compressor, and the initial pulses are between about 10 picoseconds and about 3 nanoseconds and the compressed optical pulse has a sub-picosecond duration and the energy density on the surface is between about 2 and about 10 times the optical ablation threshold of the surface.
12. The method of claim 1 1, wherein the fiber amplifier is an erbium-doped fiber amplifier.
13. The method of claim 11, wherein the air-path between gratings compressor is a Treacy grating compressor.
14. The method of claim 1, wherein two or more fiber amplifiers are used in a train mode and two or more fiber amplifiers are used with one compressor.
15. The method of claim 10, wherein the compressing is done with a chirped fiber compressor.
16. The method of claim 1, wherein pulse energy density and ablation rate are independently controlled.
17. The method of claim 1, wherein the pulse energy density, the fiber amplifier operating temperature and the ablation rate are independently controlled.
18. The method of claim 10, wherein the spot is scanned by one or more piezoelectrically driven mirror.
19. The method of claim 1, wherein the ablation is done in a line to give ablation trench digging.
US20050074974A1 true true US20050074974A1 (en) 2005-04-07
US7115514B2 US7115514B2 (en) 2006-10-03
US20140091069A1 (en) * 2006-05-25 2014-04-03 Electro Scientific Industries, Inc. Ultrashort laser pulse wafer scribing
US9221124B2 (en) * 2006-05-25 2015-12-29 Electro Scientific Industries, Inc. Ultrashort laser pulse wafer scribing
US7115514B2 (en) 2006-10-03 grant