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Home > Nanotechnology Columns > Magda Carvalho PhD, JD > Ex parte Reexamination and Nanotechnology.

Magda Carvalho
Patent Attorney
Patent Law at M. Carvalho

We should not take for granted that just because a patent has issued it is valid. Patent validity may be resolved in a reexamination process and anyone can request it. When a patent owner becomes aware of a problematic reference that may have an impact on the validity of a patent, he or she can bring that prior art and propose amendments to get around the prior art to the attention of the U.S. Patent and Trademark Office (PTO) to get a second review of the patent and hopefully a second stamp of approval. It is more difficult to break a patent in court if the PTO has already examined the prior art. The major advantage in choosing to seek a reexamination over litigation is that the reexamination costs in terms of time and money are much lower. But reexamination is limited to the review of published documents; other grounds of invalidity such as lack of enablement, prior use, or form requirements are not considered. The issue that the requester has with the patent is its broad and sometimes sweeping coverage of a very familiar application of the technology. In nanotechnology, this question highlights the complexities of the subject matter of a technology where definitions are still unsettled.

October 3rd, 2008

Ex parte Reexamination and Nanotechnology.

Reexamination can be either ex parte (1) or inter parte.(2) Reexaminations are on the rise and about 96% of requests for ex parte reexaminations are granted.(3) This column focuses on the ex parte reexamination. Ex parte reexamination means the reexamination proceedings are primarily between an Examiner and a patent owner. Any member of the public can invoke an ex parte reexamination. Patent owners have a unique motivation to turn to ex parte reexamination because they can control the process. They may rewrite the claims so that the new evidence does not invalidate them, present arguments to the Examiner and interview the Examiner. A patent remains enforceable during the reexamination process. But reexamination is not without risk. The consequences include a patent being invalidated (all claims rejected) or limited (claims narrowed, less than all allowed). Therefore, a significant risk for patent owners is invalidation of their patent if the Examiner and appeals process finally rejects all the claims. This column focuses on an ex parte reexamination initiated by a patent owner who tried to correct an otherwise overbroad patent. In the Ex-parte Massachusetts Institute of Technology (Appeal 2008-0333, June 30, 2008) the Board of Patent Appeals and Interferences (BPAI) sustained the Examiner's rejections of several claims on a patent involving optics art, specifically on nanolithography (lithography below 100 nm sizes). The invention provided a system and method of performing maskless lithography that preserved the attractive high-resolution capabilities of x-ray lithography, manufacturing semiconductor products with minimum size features of 100 nm and below. The novelty included the replacement of a mask by a multiplexed array of Fresnel zone plates (focusing elements). On appeal the issue was the definition of "Fresnel phase zone plate" as applied to similar optical structures. The result was that several claims of the patent were held invalid for obviousness.

The Process of Ex-parte Reexamination: 35 U.S.C. 301 et seq.

In a reexamination, the PTO puts the patent through a second examination with relevant published prior art references laid out. The PTO determines whether the claims of that patent are valid (and patentable) in view of prior art reference(s). The prior art reference(s) must raise "a substantial new question of patentability" as required by 35 U.S.C. § 303. A particularity of ex parte reexamination is that the PTO can invalidate a patent previously held valid by a court.

There are procedural differences that distinguish reexamination from the ordinary patent prosecution. In a way reexaminations resemble patent prosecution since they include office actions and responses, but the response periods are shorter and there is no continuation practice. Reexaminations are conducted at the Examiner level. But these Examiners are considered experts on patent law and are part of the Central Reexamination Unit made up of "twenty highly skilled primary examiners who have a full understanding of reexamination practice and relevant case law [and] will concentrate solely on reexamination."(4) Ordinarily, the reexamination will be assigned to an Examiner who was not involved in the original prosecution of the patent.(5) Also, there is a requirement for a three-member "patentability review conference" at several key points in the reexamination process, including prior to issuing a final rejection and prior to issuing a notice of intent to issue a Reexamination Certificate.(6)

The challenger can be anyone else: the inventor, the patent assignee, an infringer, a potential infringer and the public. Also, the PTO may institute a reexamination proceeding on its own motion.(7) In an ex parte reexamination, the challenger's identity may be kept secret. Eligible prior art consists only of printed documents such as patents and publications. (8) Also, affidavits or declarations are allowed but only to explain the contents or dates of the prior art.(9)

The PTO will grant a reexamination if it determines that prior art patents or printed publications raise a "substantial new question of patentability." This question must be raised by "prior art patents or printed publications" cited by the requester or found by the Examiner.(10) The statute does not specifically states what constitutes a "substantial new question of patentability." The PTO takes the view that a requester raises a substantial new question of patentability when "there is a substantial likelihood that a reasonable examiner would consider the prior art patent or printed publication important in deciding whether or not the claim is patentable," unless the same issue of patentability has already been decided by the federal court system or by the PTO.(11)

Last September, the CAFC explained the scope of "substantial new question of patentability." Specifically, the CAFC allowed consideration in a reexamination of a prior art reference used both in a previous litigation and in the original patent examination by the PTO as long as the issue raised by the prior art reference was never before addressed by the PTO. Thus, the PTO can find a "substantial new question of patentability" under §303, despite the fact that (i) the prior art was previously considered in the PTO, (ii) a District Court has considered the same art, and (iii) the CAFC has agreed with the District Court.(12,13)

During reexamination, the evidential threshold which a requester must meet is proof by a preponderance of evidence. This generally means that a requester will win if he or she can show that it is more likely than not that his or her contention is true.(14) The patent will be examined without a presumption of validity,(15) and the patent claims will be given ‘their broadest reasonable interpretation, consistent with the specification . . ."(16)

The first Response comes within three months after the request is filed.(17) The PTO decides whether it is going to take the case or not.(18) A determination that there is no "substantial new question" is final and non-appealable.(19) Once a reexamination has been ordered, the PTO has discretion to reexamine all the claims of a patent or limit reexamination to those claims for which a "substantial new question" has been found.(20) In case the patent holder is not satisfied with the results of a reexamination, he can appeal to the BPAI. Furthermore, the patent holder can appeal the determination of the BPAI to the CAFC. The patent under reexamination remains in force as issued until a reexamination certificate cancelling its claims is issued. A certificate is issued after all actions closing prosecution are dispositive, and all appeals have been exhausted.

Ex-parte Massachusetts Institute of Technology, Appeal 2008-0333 (June 30, 2008).

Massachusetts Institute of Technology (MIT) is the patent owner of the U.S. Patent No. 5,900,637 (‘637 patent) entitled "Maskless lithography using a multiplexed array of fresnel zone plates" which covers nanolithography. MIT determined that this patent was overbroad since the term "Fresnel zone plates" as used in the claim language included both amplitude-type and phase-type zone plates and should be limited specifically to "phase zone plates." MIT invoked a reexamination and proposed amendments to get around a combination of references. The Examiner found several claims invalid as obvious over the prior art references. The Board upheld the Examiner's rejection of several claims since the patentee failed to overcome the obviousness rejection. On appeal, the dispositive issue was whether the Examiner was correct in equating "micro-Fresnel lenses" to "Fresnel zone plates."

The ‘637 patent was on the art of optics. The patent covered "Fresnel zone plates," which are focusing structures widely used in the modern optical instrumentation. Fresnel is a type of diffraction known since the late 19th century. A Fresnel zone plate or just "zone plate," is a device used to focus light. It consists of a series of radially symmetric rings (known as Fresnel zones) having very specific diameters and the rings are alternated between clear and dark. Zone plates use diffraction from a dark ring. The zones can be spaced so that the diffracted light constructively interferes at the desired focus, creating an image there. There are two types of binary zone plates: amplitude zone plates and phase zone plates. In amplitude zone plates, either all the odd or even ring numbers are opaque. If either the odd or even ring numbers have a different index of refraction that induces a phase change over the zone plate's thickness, such zone plates are called "phase zone plates." In the phase-type zone plate each ring comprises some finite thickness of the original layer which is in contrast with the amplitude-type. The main advantage of phase zone plates is their high diffraction efficiency.

The ‘637 patent, published in 1997, disclosed a system and method of performing lithography without the need for a mask that contains the pattern to be exposed. Specifically, it employs an array of Fresnel zone plates to focus parallel beamlets of electromagnetic radiation so that they converge to foci on a substrate. All of the original claims recited "Fresnel zone plates," but this term appeared to be generic to include both "amplitude zone plates" and the "phase zone plates." The patent employed the phase-type zone plate structures and it did explain that the phase-types provide greater focusing efficiency than do "amplitude-types." During the reexamination the word "Fresnel" was deleted from claims 1 and 16 so that the claims read "phase zone plates."

The Examiner rejected several of the claims at issue as obvious under 35 U.S.C. § 103, in light of two combinations of references: Johnson and Kirz. The Examiner found that Johnson patent also disclosed a projection system which focuses an image source onto a focusing structure made up of an array of "microlenses" or "micro-Fresnel lenses (or binary optics)." In Johnson the light source is described "a continuous deep-UV laser light." MIT made the distinction that Johnson did not indicate that the microlenses could take the form of "phase zone plates" as claimed. However, the Examiner found that Johnson's statement that the microlenses may be "micro-Fresnel" meaning that it encompasses "Fresnel zone plates." Also, Johnson disclosed that the micro-Fresnel lenses may be "binary optics" which term also includes "Fresnel zone plates." Although, Johnson did not specifically teach "phase zone plates" this missing element was found in the Kirz reference entitled "Phase zone plates for x rays and the extreme UV" which taught that "phase zone plates" were superior to "Fresnel zone plates." The patentee argued that in Kirz, published in 1974, the term "Fresnel zone plate" referred only to "amplitude zone plates." Therefore, Kirz failed to teach "phase zone plates." The examiner concluded that Johnson and Kirz each disclosed a system that is similar to that disclosed by the patentee, and that it would have been obvious to replace the "Fresnel zone plate" in Johnson with a "phase zone plate" in view of Kirz.

The Board affirmed the examiner's rejections since the patentee failed to successfully to differentiate his invention over Johnson and Kirz. First, the Board rejected the patentee's argument that Johnson lacks teaching for "zone plates" and thence to "Fresnel zone plates" since it refers to lenses, not "plate," and more specifically to "micro-Fresnel lenses." The Board also rejected the patentee's argument that in Fresnel zone plates the lenses have "grooves cut therein" while Fresnel lenses are sloped. The Board agreed with the Examiner's structural definition found in the Handbook of Optics, that Fresnel lenses are lenses composed of many divided annular zones, each zone having a smooth contour and that "Fresnel lenses are closely related to Fresnel zone plates." A Fresnel lens has a smooth contour in each zone while a Fresnel zone plate has stepped contour in each zone. Also, the term "binary optics" was defined as the equivalent of micro-Fresnel lenses since it was defined as being "stepped approximation of" a micro-Fresnel lens. It therefore was reasoned that since micro-Fresnel includes Fresnel zone plates, so does "binary optics." Second, the Board rejected the patentee's figures distinguishing "Fresnel lens" as having either stepped or sloped contours as distinct from a "zone plate" which has "grooves cut therein" since the designs lacked the characteristic Fresnel annular zones; it failed to depict the radial distribution of the profiles. Lastly, the Board found that the Swanson patent, which is assigned to MIT, illustrated a radial distribution of different profiles of "Fresnel zone plates" having a stepped contour in each zone. Therefore, MIT failed to persuade the Board that "Fresnel zone plates" are structurally built with "grooves cut therein."

In summary, in the context of this invention a "Fresnel zone plate" is not patentable because it is still a "phase zone plate. "Phase zone plates," or its equivalents, were previously known to work as intended in the optics art. There has been no transformation of the "zone plate" in a physical way, so there was nothing nonobvious. The inventor only stated that "[i]f deep UV radiation is used…..the zone plates could be made from phase zone plates, i.e. grooves cut into the glass membrane."(21) Here, it seems that a successful inventor would have to built a Fresnel zone plate having "grooves cut therein" and showed that it worked as intended, which would have been physically different from the Fresnel zone plates recognized by the skilled artisan which have stepped contours.

(1) 35 USC Section 301, et seq.
(2) 35 USC Section 311, et seq.
(3) See PatentlyO, Ex Parte Reexamination Statistics I, (June 05, 2008)
(4) See, USPTO Press Release #05-38, USPTO Improves Process For Reviewing Patents (July 29, 2005), copy available at
(5) See, MPEP §§ 2236, 2636.
(6) See, MPEP §§ 2271.01, 2671.03.
(7)35 U.S.C. §§ 303-04.
(8) 35 U.S.C. §§ 301, 302, 37 CFR §1.510.
(9) See, MPEP §§ 2258(H), 2658(H). See also MPEP § 2258 (identifying sections of 35 U.S.C. § 102 upon which prior art rejections may be based in ex parte reexamination), § 2658 (same for inter partes reexamination).
(10) See, MPEP §§ 2244, 2644 (emphasis added); 35 U.S.C. § 301.
(11) See, MPEP § 2242 ("The meaning and scope of the term ‘a substantial new question of patentability' is not defined in the statute and must be developed to some extent on a case-by-case basis, using the case law to provide guidance").
(12) 35 USC §303 "The existence of a substantial new question of patentability is not precluded by the fact that a patent or printed publication was previously cited by or to the Office or considered by the Office."
(13) In ree Swanson, September 4, 2008 (07-1534).
(14) In re Caveney, 761 F.2d 671, 674 (Fed. Cir. 1985).
(15) In re Etter, 756 F.2d 852, 856-58 (Fed. Cir. 1985). The "examiner is not attacking the validity of the patent but is conducting a subjective examination of the claims in light of prior art."
(16) In re Trans Tex. Holdings Corp, 498 F.3d 1290, 1298 (Fed. Circ. 2007). Distinct from district courts, in reexamination proceedings "[c]laims are given ‘their broadest reasonable interpretation, consistent with the specification . . . .'" (quoting In re Yamamoto, 740 F.2d 1569, 1571 (Fed. Cir. 1984).
(17) 35 U.S.C. §§ 303, 37 CFR §1.515.
(18) 35 U.S.C. § 304, 37 CFR §1.525.
(19) 35 U.S.C. § 303.
(20) Sony Computer Entm't Am., Inc. v. Dudas, No. 05CV1447, 2006 WL 1472462, *9 (E.D. Va. May 22,
(21) See, U.S. Patent No. 5,900,637 at Detailed Description of the Illustrated Embodiments.

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