T 0930/92 (Ion beam processing) 29-05-1995

Summary of Facts and Submissions

I. European patent No. 0 075 949 comprising eleven claims was granted to the Respondent.

Claim 1 of this patent reads:

"An ion-beam processing apparatus for correcting a defect consisting of the unwanted presence of material in a fine circuit pattern drawn on a surface of a specimen, said apparatus being provided within a vacuum container (39) including a specimen chamber (40) with a table (55) for mounting said specimen (90) therein, and comprising:

an ion source (65) facing said specimen chamber (40),

an extraction electrode (67) for extracting an ion beam (68) from said ion source (65),

a first aperture (69) for controlling the spot diameter and spot current of said ion beam (68) when focused to a spot on said specimen (90),

at least one set of electrostatic lenses (70, 71, 72) for focusing said ion beam (68) outputted through said first aperture (69) to form a spot (68) on the surface of said specimen (90),

X-axis and Y-axis deflection electrodes (75, 76) for scanning said ion beam spot (68') over said specimen (90) in two mutually orthogonal directions,

a secondary charged particles detector (86) for detecting the intensity of secondary charged particles emitted from said specimen (90) when subjected to the ion beam and for transducing said intensity into an electrical signal and

display means (87) receiving said signal from said detector (86) and X- and Y-deflection signals applied to said deflection electrodes (75, 76) for scanning a spot having an intensity proportional to said signal from said detector (86) in synchronism with said ion beam spot (68') scanning over said specimen (90) so as to allow observation of the surface of said specimen (90), wherein

said ion source (65) is of the liquid metal type or of the ultra-low temperature electric field ionisation type generating a high intensity ion beam (68) to form a spot (68') of less than or equal to 0.5 µm diameter on said surface of said specimen (90) through said first aperture (69) and said set of electrostatic lenses (70, 71, 72),

said apparatus further comprises setting means (696) for setting a range of co-ordinates (X1-X2, Y1-Y2) relative to said X- and Y-axes, said range defining a region of the surface of said specimen (90) to be processed and said range also being displayed on said display means (87),

a second aperture (74) is provided between at least a portion of said set of electrostatic lenses (70, 71, 72) and said deflection electrodes (75, 76) for interrupting the projection of said ion beam (68) onto said specimen (90),

a beam-blanking electrode (73) is disposed upstream said second aperture (74),

a power controller (85) is provided to supply a blanking signal, in dependence on said setting means (696) and said X- and Y-direction signals, so as to operate on the beam-blanking electrode (73) to deflect the ion beam out of said second aperture (74) except when the beam spot (68') lies within the said region to be processed and

switching means (112) are provided for switching power supplies (78, 79, 80,81) and said power controller (85) supplying said ion source, electrodes and lenses so as to selectively provide a low-power ion beam suitable for scanning the surface of said specimen (90) without damaging said pattern, so that said defect may be observed on said display means (87), and a high-power ion beam suitable for scanning the said region to be processed, which region may include said defect, and for sputtering the material constituting said defect so that said defect may be removed",

three minor spelling mistakes having been corrected in the claim.

Claims 2 to 10 are dependent upon Claim 1. Independent Claim 11 is a method claim which reads as follows:

"A method for correcting a defect consisting of the unwanted presence of material in a fine circuit pattern on a mask, said method comprising the steps of: extracting an ion beam (68) out of a high intensity ion source (65) by means of an extraction electrode (67),

focusing said ion beam (68) into a fine spot (68') having a spot diameter of less than or equal to 0.5 µm by means of an electro-optical system (70, 71, 72) and a first aperture (69),

deflecting said ion beam (68) by means of X-axis and Y-axis deflection electrodes (75, 76) along two mutually orthogonal directions for scanning said spot (68') over said mask (90) along said directions,

detecting the intensity of secondary charged particles emitted from said mask (90) when exposed to a low-power ion beam by means of a secondary charged particles detector (86) transducing said intensity into an electric signal,

displaying said intensity on a display means (87) through a spot having an intensity proportional to the output of said secondary charged particles detector (68) and being scanned over said display means (87) in synchronism with said ion beam (68) scanning an area of the surface of said mask (90) in accordance with deflection signals applied to said deflection electrodes (75, 76) so as to enable the observation of said surface area of said mask (90),

setting a defect portion to be corrected on said mask (90) by means of setting means (696) acting on said display means (87),

switching the power of said ion beam (68) irradiated onto said surface of said mask (90) between a low-power value for detecting a surface area to be corrected on said mask (90) by means of said secondary charged particles detector (86) and a high-power value for correcting a defect portion (92) indicated by said setting means (696) through said ion beam (68),

blanking said ion beam (68) by deflecting it out of a second aperture (74) by means of a beam blanking electrode (73) and deflecting said ion beam (68) be means of said deflection electrodes (75, 76) in accordance with a signal produced by said setting means (696) and

removing said defect portion (92) of said mask (90) by sputtering",

a minor spelling mistake having been corrected in the claim.

II. The Appellant filed an opposition against the above European patent, citing the documents

D1: "Scanning microbeam using a liquid metal ion source", T. Ishitani et al., J. Vac. Sci. Technol., 20(1), Jan. 1982, American Vacuum Society, pages 80-83,

D2: US-A-3 517 191,

D3: "Small area depth profiling with the ion microprode", T. A. Whatley et al., Surface Analysis Techniques for Metallurgical Applications, ASTM STP 596, American Society for Testing and Materials, 1976, pages 114-125, and

D4: "Microprobe for the ion bombard mass analyzer", H. Tamura et al., in "Recent Developments in Mass Spectroscopy: Proc. Int. Conf. on Mass Spectroscopy, Kyoto", ed. K. Ogata, publ. Baltimore, Univ. Park Press, 1970,

and requesting that said patent be revoked on each of the grounds mentioned in Article 100 EPC.

In the course of the proceedings before the Opposition Division, the Appellant additionally cited

D5: "The very bright field ionization and field evaporation ion sources. Some uses. A beam formation and scanning system", H. Heil et al., Proc. Symp. on Ion Sources and Formation of Ion Beams, Oct. 19-21, 1971, Brookhaven National Laboratory, Upton, NY, USA, pp. 183-189,

D6: "High-resolution, ion-beam processes for microstructure fabrication", R. L. Seliger et al., J. Vac. Sci. Technol. 16(6), Nov./Dec. 1979, pp. 1610-1612, and

D7: "In-depth analysis in selected area with ion microprobe analyser", H. Tamura et al., Proc. 6th Internl. Vacuum congr. 1974, Japan. J. Appl. Pys. Suppl. 2, Pt. 1, 1974, pp. 379-382,

whereas the Opposition Division drew attention to the following documents which had been cited in the European Search Report:

DD: Patents Abstracts of Japan, Vol. 5, No. 86 (E- 60)[758], 5th June 1981; & JP-A-56-33829, and

DE: Patents Abstracts of Japan, Vol. 5, No. 186 (E84)[858], 25th November 1981; & JP-A-56-111227.

During oral proceedings held on 24 June 1992 before the Opposition Division, the Appellant withdrew its objections under Article 100(b) and (c) EPC.

III. The Opposition Division rejected the opposition, grounding its decision in substance as follows:

The patent in suit validly claims the priority of a patent application filed in Japan before document (D1) was published. The latter, therefore, may not be taken into consideration. In pursuance of Article 114(2) EPC, this also applies to the late filed document (D7) which admittedly teaches that an etching rate can be adjusted by varying the intensity of an ion beam. This is not the same as using a low-power beam which does not damage the surface for observing a workpiece. Moreover, (D7) teaches to position the analysing beam at the preselected point, rather than scanning it over a region where it is desired to carry out an analysis.

The invention belongs to the technical field of pattern defect correction by micromachining. None of the documents cited by the Opponent (Appellant) and published before the priority date of the European patent belongs to this field: (D2), (D3) and (D4) relate to scanning ion microscopy; (D5) mentions micromachining as a possible application of ion beams, while (D6) describes micromachining of a gold layer on silicon. Furthermore, (D5) and (D6) are rather academic papers. Only document (DE) relates to pattern defect removal, and actually by means of a laser beam. Document (DE) also discloses setting means comprising an image control part (10) and two pairs of electronic cursors (13), which are positioned so as to bracket the defect (7).

The subject-matter of Claim 1 differs from the prior art known from (DE) in that defect detection and correction are carried out by a scanned ion beam produced from an ion source of the liquid metal or ultra-low temperature field emission type. Document (D5) would not have incited a skilled person to use such a source for it states that, "in order to work on such a new application ..., it is necessary ... to show its usefulness or relevance". Document (D6) is more relevant, since it discloses ion beam micromachining to produce features of such small width as 38 nm using a liquid gallium source. Nevertheless, there is a distinction between using an ion beam to draw a pattern and using an ion beam to correct pattern defects, which requires greater control of beam power and direction. A skilled person knowing that, in direct analogy to the teachings of (DE), a shaped ion beam could be used, would not be incited to adopt the ion beam scanning system of (D6), and no blanking electrode would be needed. Likewise, neither would the need for an ion beam scanning system in conjunction with a detector of secondary charged particles and synchronised display means be felt, since the device of (DE) provides a video image of the specimen surface. There would also be no need to switch between high and low power beams. As in (DE), cursors would locate the defect on the video screen, the specimen support table would be moved so as to centre the defect with respect to the ion beam, the latter would be appropriately shaped and the high-power beam would be switched on to sputter off the defect. Therefore, Claim 1 involves an inventive step and, for the same reasons, so does Claim 11.

IV. The Opponent lodged an appeal against the decision of the Opposition Division, requesting that said decision be set aside, that the European patent be revoked and, subsidiarily, that oral proceedings be scheduled if the Board intended to uphold the impugned decision.

In support of these requests, the Appellant argued in substance as follows:

The effect to be achieved by the invention, namely removing unwanted matter from a fine circuit pattern, does not involve a limitation of the claimed protection. For this reason, the patent in suit must be classified in the broader field of ion beam techniques for producing circuits. This field includes devices for making circuits as well as devices for correcting defects and, usually, the same apparatus carries out both tasks.

Document (D5) discloses an ion beam processing apparatus using a liquid metal ion source by means of which the beam diameter can be made as small as 1 nm. From Figure 1a and the related part of the description, the following features of the apparatus claimed in the European patent are known: extraction electrode, limiting aperture, electrostatic lens and electric deflection system. When envisaging to machine a workpiece in a selected region, however, it is of obvious necessity to provide setting means. Likewise, in order that material be removed only from the selected region, it is necessary to provide a second aperture (74) between at least a portion of the electrostatic lenses and the deflection electrodes, a beam blanking electrode and a power controller operating the latter except when the beam spot lies within the selected region to be processed. Finally, document (D5) also suggests the possibility of using a signal derived from the emission of secondary charged particles. This would incite the skilled person to provide a detector of such particles and a display device, whereby the necessity of switching between a low power and a high power of the ion beam would be obvious.

Therefore, the teachings of (D5) and the common general knowledge of the skilled person are already enough to arrive, without having to display inventive talent, at the subject-matter claimed in the European patent.

Document (D6) too relates to an ion beam processing apparatus of the kind referred to a Claim 1. The spot of the beam extracted from the liquid metal source mentioned there has a diameter in the range of 0.1 to 0.5. µm. In Figure 1, the following features of the claimed apparatus are represented: extraction electrode, aperture, lens and deflection. To the skilled person, providing the remaining features of said claimed apparatus is a mere question of routine.

The skilled person would also consider the teachings of (D7), since it discloses the removal of unwanted matter from a selected region by scanning an ion beam. Figure 2 shows a deflector, a collector of secondary charged particles and a cathode ray tube displaying an image of the workpiece's surface. Besides, the features necessary to produce the ion beam are implicitly disclosed and, here again, providing the remaining features of Claim 1 is a question of routine. Furthermore, varying the beam energy in accordance with the desired etching speed is also known from (D7). If only a display of the surface to be locally processed is wished, it is consequently obvious that the beam intensity must then be set at a low value.

V. The Respondent (Proprietor of the patent) requested that the appeal be dismissed, that the patent in suit be maintained as granted and, subsidiarily, that oral proceedings be held.

The Respondent's arguments, insofar as they do not repeat those of the Opposition Division, may be summarised as follows:

Micromachining to remove unwanted material in the mask pattern of integrated circuits requires apparatus different from those used for fabricating or analysing microstructured circuitry. This observation is actually the more relevant as the Appellant admitted that a plurality of features characterising the present invention are not found in the references cited.

Document (D5) just teaches that material can be sputtered off when a high brightness beam is used. Document (D5) thus discloses only one use of the ion beam and even leads away from using an ion beam both for detection and correction. Document (D6) teaches that resolution is improved if ion beams are patterned to small dimensions before they strike the surface to be machined. Finally, document (D7) only discloses a scan- stop method for performing in-depth analysis by means of a mass spectrometer. The primary ion beam is positioned at a selected point and the mass spectrometer is set at a pre-selected value of mass to determine the quantity of ions of the corresponding species. The difficulties found in the prior art and mentioned in the patent cannot be overcome by a combination of these teachings. It is by providing an apparatus using the same ion beam for detecting a defect and subsequently removing it, whereby only an increase of the beam power is needed, that the invention achieves this result.

VI. The Board summoned the parties to oral proceedings to be held on 19 October 1994, without issuing a communication pursuant to Article 11(2) RPBA.

VII. The Respondent's representative appeared at the date and time fixed for the oral proceedings, accompanied by two employees of the Respondent company, one being an inventor, and the other being a member of the Respondent's Patent Department.

The Appellant's representative did not appear and, in a phone call made by the Registrar of the Board before the proceedings began, he stated that he would not attend the proceedings.

The Chairman opened the oral proceedings, and stated that the Board intended to dismiss the appeal and to maintain the patent as granted, and that no further submissions from either party concerning the substantive issue of patentability would be admissible.

The Respondent's representative stated that a request for apportionment of costs would be filed in writing.

The Chairman stated that the appeal proceedings would be continued in writing with respect to the apportionment of costs, and closed the oral proceedings.

VIII. The Respondent's written request for apportionment of costs was filed on 21 November 1994, and contains a request that the following costs which were incurred by the Respondent should be awarded against the Appellant:

Flight tickets for the two employees of the Respondent company, Tokyo - Munich - Tokyo, (copies were enclosed): DM 20,927,20

Hotel expenses for the above two employees (a copy of the bill was enclosed) DM 2,812,20

Travel expenses for the above two employees Yokohama-Tokyo-Yokohama (estimated) DM 300,--

Extra expenses for the above two employees for food during their stay (estimated) DM 1,400,--

Public transport for the above two employees within Munich and to and from the airport (estimated) DM 50,--

Renting a video equipment DM 57,50

Renumeration of the professional representative (1 attorney, 3 1/2 days) DM 8,750,--

Total: DM 34,296,90

In support of the above request, the Respondent submitted essentially as follows:

Since the Board came to a preliminary opinion on the written submissions that the appeal should be dismissed, no oral proceedings were necessary from the Respondent's side. It is the duty of a party to inform the other party and the Board if he does not intend to appear as summoned, in order to avoid unnecessary costs being incurred.

The Appellant was informed by letter dated 29 July 1994 which was written in connection with fixing the date for oral proceedings that representatives of the patent Proprietor's company would attend the oral proceedings, and he indicated in reply to the Respondent (but not to the Board) that the Appellant might not attend the oral proceedings. However, such an indication was clearly too uncertain for the Respondent to cease preparation for the oral proceedings.

The Appellant therefore knew that the Respondent's preparations for the oral proceedings in October 1995 would incur high costs, and had plenty of time to make up his mind whether or not to attend such proceedings, and if not, to inform the Respondent and the Board in good time in advance of 19 October 1995.

IX. The Board invited the Appellant to respond to this request for costs within two months. The Appellant's reply was filed on 26 January 1995.

(1) The Appellant submitted that the Respondent's request for an award of costs should be rejected, essentially for the following reasons:

(a) According to Article 104(1) EPC, each party to opposition proceedings should bear its own costs, unless a different apportionment is ordered for reasons of equity. There are no reasons of equity in the present case to justify a different apportionment of costs.

In principle a party to opposition proceedings is free to choose whether or not to attend oral proceedings which have been arranged by an Opposition Division or a Board of Appeal, subject to the following exceptions:

(1) The first exception is when the parties can see that the oral proceedings have been arranged as a consequence of an auxiliary request of only one party. In such a case the party at whose request the oral proceedings have been arranged is obliged either to attend the oral proceedings or to notify the EPO in advance that it will not attend.

The present case is not such a case, because both parties had made an auxiliary request for oral proceedings so the oral proceedings had not been arranged specifically for either one of them. From the Appellant's point of view the oral proceedings had not been arranged specifically following its auxiliary request.

(2) A second exception is when the Opposition Division or Board of Appeal has issued a communication accompanying the invitation to oral proceedings, which indicated a preliminary view against a particular party. In such a case that party is also obliged to notify its intention not to attend the oral proceedings in good time in advance of the appointed day.

In the present case no such communication was issued by the Board of Appeal.

Furthermore:

(3) Since about July 1993 invitations to oral proceedings from the EPO have been accompanied by a form entitled "Important information concerning oral proceedings" (Form 2043.2.07.93) which states inter alia that a party who does not wish to attend oral proceedings on the date appointed is requested to notify the EPO immediately, and in urgent cases to notify other parties as well. This form also states that costs incurred by other parties may be charged to a party who either fails to notify such parties of his non-attendance, or does not notify them in good time.

In the present case no such form was sent with the invitation to oral proceedings.

(b) The Appellant also contested the extent of the costs claimed by the Respondent, as not being justified in equity, for the following reasons:

(1) The Japan-based Respondent is represented by a patent attorney based in Munich, who appeared alone at the oral proceedings before the Opposition Division. The patent Proprietor had no proper reason to send its employees to the oral proceedings before the Board of Appeal in addition to the patent attorney, and it would be unfair to award costs in respect of the attendance of the two employees from Japan.

(2) Furthermore the costs of two employees travelling from Japan goes beyond the scale envisaged under Article 104 EPC.

(3) The length of the two employees stay in Munich was also excessive for the preparation for oral proceedings.

(4) The preparations during three and a half days by the patent attorney were also excessively long.

X. The Respondent replied to these contentions in a letter filed on 21 February 1995.