T 1631/11 23-07-2013

Reasons for the Decision

1. Allowability of amendments made in claims 1 (Article 123(2) EPC)

Since the Board considers that process claim 1 of the main request contravenes Article 123(2) EPC, amongst others, for not defining that the measured concentration of the oxidiser and the detected flow rate of the slurry are used to determine fuzzy logic variables, which are then used for determining an injection rate for the oxidiser to control the concentration of the oxidiser (see points 1.1 to 1.7.7 below), which conclusion equally applies to the process claims 1 of the replacement first and second auxiliary requests (see point 1.8 below), there is no need to consider in this decision whether or not the amendments made in these three requests comply with Article 84 EPC.

Main request

1.1 The Board comes to the conclusion that process claim 1 of the main request in this respect does not comply with Article 123(2) EPC for the reasons that follow.

1.2 The present application as originally filed (corresponding to the published WO-A-01 89767 which in the following is quoted) comprises in total 14 pages of description consisting of the four paragraphs "Field of the Invention" (page 1, lines 6 to 9), "Background of the Invention" (page 1, line 11 to page 2, line 12), "Brief Description of the Drawings" (page 2, line 14 to page 3, line 16) and "Detailed Description of the Drawings" (page 3, line 18 to page 14, line 8. It further contains claims 1 to 10 and figures 1 to 6.

1.3 The description starts by stating that the invention relates, in general, to manufacturing semiconductor components, and more particularly, to detecting concentrations of components in mixtures used in the manufacturing of the same (see page 1, lines 6 to 9).

1.3.1 In the context of the background of invention it is described that CMP slurries can be used for planarising metal layers and that they can include a buffered solution, an oxidiser, and an abrasive. Such slurries for polishing tungsten metals require precise quantities of the oxidiser which has an extremely short useful lifetime so that new quantities must be added to the CMP slurry to maintain the necessary chemical activity of the oxidiser (see page 1, lines 12 to 18).

Prior art techniques for determining the oxidiser concentration include manual techniques such as titration which is time consuming and results in a poor process control (see page 1, lines 19 to 23).

This short useful lifetime also produces other problems in existing CMP systems which include, for example the use of large day tanks for holding significant quantities of CMP slurry. These day tanks consume large amounts of floor space and are expensive and large amounts of oxidiser must be added periodically to the slurry stored in such day tanks. Furthermore, there may exist residence time problems with these large quantities of CMP slurry resulting in that they must be rejuvenated via chemical additions (see page 1, line 24 to page 2, line 12).

1.3.2 Subsequently the object to be solved by the invention is stated as: "Accordingly, a need exists for a method of manufacturing semiconductor components that includes a process for easily, accurately, and cost-effectively detecting and controlling a concentration of a component in a mixture. As applied to CMP processing, a need exists for a CMP system that can easily, accurately, and cost-effectively detect and control a concentration of an oxidiser or other time-sensitive chemical components in a CMP slurry" (see page 2, lines 8 to 12).

1.3.3 There is no further general description of the different parts of the invention, nor of possible alternatives for these different parts. The following paragraph deals with the single embodiment of the figures and states that "The invention will be better understood from a reading of the following detailed description, taken in conjunction with the accompanying drawing figures". Figure 1 is stated to illustrate a cross-sectional view of a portion of a CMP system in accordance with "an" embodiment of the invention, figure 2 illustrates a flow chart of a method in accordance with "an" embodiment of the invention, figures 3 to 6 illustrate fuzzy logic graphs for the method of figure 2 in accordance with "an" embodiment of the invention.

The Board notes that the undefined article "an" in this respect does not imply more than one embodiment, since what follows is the description of only one and the same embodiment, as will be shown below.

Thereafter it is stated that for simplicity and clarity of illustration these drawing figures illustrate the general manner of construction, and elements in the drawing figures are not necessarily drawn to scale, as well as that descriptions and details of well-known features and techniques are omitted to avoid unnecessarily obscuring the invention. Moreover, the terms first, second, top, bottom, etc. "in the description and in the claims, if any, are used for distinguishing between similar elements and not necessarily for describing relative positions or a sequential or chronological order", and "that the embodiments described are capable of operation in other orientations or sequences than described or illustrated herein". Finally it is remarked in this paragraph "that the terms so used are interchangeable under appropriate circumstances" (see page 3, lines 5 to 16).

1.4 In the subsequent paragraph the single specific embodiment of a CMP system according to figure 1 is described which is used in the method 200 for manufacturing a semiconductor component as shown in the flowchart of figure 2 (see page 7, lines 10 and 11).

1.4.1 According to this specific method of figure 2 according to steps 205 to 215 semiconductor devices are formed in a semiconductor substrate and thereafter a layer is formed over the semiconductor substrate and the semiconductor devices (see page 7, lines 10 to 16).

1.4.2 According to step 220 first and second components of a mixture are provided and mixed together and in "the preferred embodiment, the mixture is a CMP slurry; the first component is an oxidiser, such as, for example, hydrogen peroxide; and the second component is an abrasive such as, for example, silica particles suspended in a liquid carrier. The mixture can also be comprised of other components known to those skilled in the art of CMP processing" (see page 7, line 20 to page 8, line 1). According to the preferred embodiment these two components are mixed or combined together within the reservoir 120 (i.e. in the vessel 110) of figure 1 (see page 8, lines 1 to 3).

1.4.3 Step 225 of figure 2 is then stated to be optional only but particularly useful if the oxidiser is hydrogen peroxide, since in that case the mixture has a limited lifetime due to the decomposition of the hydrogen peroxide into oxygen and water (see page 8, lines 7 to 15).

1.4.4 At a step 230 a concentration of the first component (i.e. the oxidiser) is optically detected or measured. As an example, refractometer 150 (figure 1) can be used to quickly perform step 230. In the preferred embodiment it is performed in-situ within reservoir 120 while dynamically mixing together the first and second components and this fast, automated, and in-situ measurement provides a more accurate measurement of the concentration of the first component than a slow titration process (see page 8, lines 16 to 21) by measuring an index of refraction of a portion of the mixture, which preferably is comprised of a boundary layer in the CMP slurry. As an example it is comprised of the first component, or the oxidiser, and is devoid of the second component, or the abrasive particles but is also comprised of other liquid components such as, for example, the liquid carrier for the abrasive particles (see page 8, line 22 to page 9, line 4). To measure the index of refraction of this boundary layer, the refractometer shines a light through a solid material such as, for example, a prism 151 toward interface 152 between prism 151 and the CMP slurry within reservoir 120 (figure 1) and optically detects the angle of the light reflected off the interface 152 to determine the index of refraction of the liquid boundary layer surrounding the CMP slurry abrasive particles. The measured index of refraction is directly and linearly proportional to the concentration of the first component within the mixture and the determined concentration is subsequently used to determine a second injection rate for the first component of the mixture (see page 9, lines 5 to 17).

1.4.5 Then at a step 235 of method 200 a flow rate of the mixture is detected or measured, as an example flow rate 160 in figure 1 can be used, and is subsequently used to determine a second injection rate for the first component of the mixture. It is also stated that steps 230 and 235 can be reversed (see page 9, lines 18 to 21).

1.4.6 Next, at step 240 of method 200, the concentration determined in step 230 and the flow rate determined in step 235 are used to determine fuzzy logic parameters or variables and the details of the conversions into fuzzy logic variables is described in more detail with respect to figures 3 and 4 (see page 9, line 22 to page 10, line 8).

1.4.7 At a step 245 the fuzzy logic variables are used to determine a second injection rate for the first component of the mixture and the details of this step are explained in more detail with reference to figures 5 and 6 (see page 10, lines 9 to 12).

1.4.8 Next at a step 250 a second additional amount of the first component is added to the mixture at a second injection rate which most likely will be different from the first rate (see page 10, lines 13 to 15).

1.4.9 Then at step 255 the mixture is applied to the first layer over the semiconductor substrate and at a step 260 the mixture is used to chemically-mechanically polish the first layer (see page 10, lines 20 to 22).

1.4.10 After the description of the fuzzy logic graphs of figures 3-6 it is then stated that an improved method of manufacturing a semiconductor component and CMP system therefor is provided to overcome the disadvantages of the prior art and that the thirty second optical detection cycle is much faster and more accurate than the fifteen minute titration cycle of the prior art. The optical detection is in-line and non-intrusive and also more cost effective. Moreover, the fuzzy logic control system provides a faster and more accurate response that will not overshoot the intended target and that will also not oscillate around the intended target (see page 13, lines 7 to 16).

1.4.11 Finally the description comprises the common statement that various changes can be made - amongst the examples the compositions of the mixture are mentioned. Further, the fuzzy logic can be used to adjust the pump stroke volume instead of, or in addition to, the pump stroke rate - and that "the scope of the invention shall be limited only to the extent required by the appended claims" (see page 13, line 17 to page 14, line 8).

1.5 The claims 1-10 of the application as originally filed are silent with respect to any controlling of the concentration of the first component or oxidiser as well as to the use of a fuzzy logic control system.

1.5.1 In particular, independent claim 1 defines: "A method of manufacturing a semiconductor component comprising: forming a first layer over a semiconductor substrate; providing a mixture comprised of a first component and a second component; optically detecting a concentration of the first component in the mixture; and applying the mixture to the first layer."

1.5.2 The dependent claims 2 and 3 quoted by the appellant define, respectively:

"The method of claim 1 further comprising: providing an oxidizer for the first component; and providing an abrasive for the second component." and "The method of claim 1 or 2 further comprising: adding a first additional amount of the first component to the mixture at a first rate before optically detecting the concentration; and adding a second additional amount of the first component of the mixture at a second rate different from the first rate after optically detecting the concentration."

1.6 The Board considers that for compliance with Article 123(2) EPC, amongst others, it needs to be decided what the relevant person skilled in the art - which in the present case is a chemical engineer having common general knowledge of process control, semiconductor manufacturing including CMP processing and at least basic knowledge of the chemistry and the possible reactions of the chemicals used therein - directly and unambiguously derives from the whole specification of the application as originally filed, i.e. the description, the claims and the figures as being the control of the oxidiser in the CMP method. Does it or not use any fuzzy logic variables? Consequently, the Board cannot see any deviation in its reasoning from the conclusion of decision T 2619/11 (supra) that the disclosure of an application is directed to a technical audience and what that audience can derive from the disclosure.

1.7 First of all, the skilled person knows from his common general knowledge that hydrogen peroxide is a commonly used oxidiser in CMP processing. However, hydrogen peroxide has a short lifetime due to its decomposition into water and oxygen. If he would not be aware of the latter fact then he could derive it in any case from the present application (see page 8, lines 7 and 8).

1.7.1 Consequently, by reading the problems described in the context of CMP processing in the prior art (see point 1.3.1 above) and the statement of the object to be solved by the present application (see point 1.3.2 above) in combination with the description of the specific embodiment illustrated in accordance with figures 1 and 2 it is clear to him that titration as well as the use of day storage tanks should be avoided. The latter particularly in view of the fact that said commonly used hydrogen peroxide has a short lifetime so that the process can be made more cost-effective by not wasting this expensive oxidiser unnecessarily while at the same time further saving money for not having the investment in these day tanks. Thus it is clear to him that the CMP slurry should be made from the two components oxidiser and abrasive such that any decomposition of the oxidiser is minimized, i.e. the invention requires that the CMP slurry should be made just in time before its intended use by mixing the two components in a mixing vessel wherein also the concentration measurement takes place to be used in the control of the amount of oxidiser added to that mixing vessel.

The teaching of claims 1 to 10 as originally filed is not helpful in this context to the person skilled in the art for the following reasons.

1.7.2 Firstly, original claim 1 only defines "providing a mixture comprised of a first component and a second component" (see point 1.5.1 above) which definition can be interpreted by the skilled person as covering a premixed mixture. Taking account of his considerations in point 1.7.1 above, it is, however, clear to him that a premixed CMP slurry - which could be read into this broad definition "providing a mixture comprising …" of claim 1 - such as a CMP slurry comprised in a day tank according to the prior art does not solve the technical problem underlying the present application as specified in point 1.3.2 above.

Therefore the appellant's arguments that the skilled person would comprehend that only a part of the prior art problems need be solved in view of claims 1 and 2 as originally filed cannot hold.

1.7.3 The two components of this mixture are specified in original claim 2 as "an oxidiser" and "an abrasive", respectively (see point 1.5.2 above). It is clear to the skilled person that a mixture of e.g. a solid oxidiser and a solid abrasive, as encompassed by original claim 2, does not result in a CMP slurry since a slurry requires the presence of a liquid or solvent.

It is likewise clear to the person skilled in the art from his common general knowledge that such a liquid or solvent is also necessary to dilute the oxidiser in said mixture since it is not possible to use a liquid oxidiser, for example simply using a solution of concentrated hydrogen peroxide, as the solvent for the abrasive since its concentration would be much too high for the intended use in CMP processing. In this context the skilled person is taught by the original application that the abrasive is in a liquid carrier or in a liquid suspension (see page 7, lines 20 to 23 and page 9, lines 3 and 4). Consequently, the appellant's arguments that a slurry of an oxidiser and abrasive comprising such a liquid carrier or solvent would represent only a preferred embodiment within an original broader disclosure cannot hold, either.

1.7.4 When reading the teaching of the broadly worded claims 1 to 10 as originally filed the person skilled in the art realises that their subject-matter cannot solve said technical problem since they are absolutely silent with respect to controlling the concentration of the oxidiser in the CMP process.

1.7.5 Thus it is clear to him that he has to derive the necessary information from the description and the figures, which give only one embodiment of the process using the apparatus of figure 1 and following the general process sequence of figure 2 in combination with the remaining figures 3-6, using his common general knowledge.

1.7.6 The appellant argued that the skilled person would derive from a combination of original claim 3 and the disclosures concerning measuring of the flow rate and the refractive index for determining the (second) flow rate of the first component, i.e. the oxidiser, into the vessel (see page 6, line 20 to page 7, line 2 and page 9, lines 19 to 21) that he can use a conventional control system for controlling the concentration of the oxidiser. These arguments cannot hold for the following reasons.

First of all, the flowchart of figure 2 teaches the skilled person a general process of manufacturing a semiconductor component comprising the process steps: 205, 210, 215, 220, 225, 230, 235, 240, 245, 250, 255 and 260. This process is much more specific than the respective process of original process claim 3 (which teaching correlates to process steps: 225 and 250 so that these steps of claim 3 when read together with those of claim 1 would correspond only to steps: 205, 210, 215, 225, 230, 250 and 255) but which likewise as claim 3 does not define the first and second components of the mixture.

This reading does not produce any information regarding the control of the concentration yet. The only information concerning this control relates to the use of the measured concentration of the first component in the mixture and the measured flow rate of this mixture (steps 230, 235) to determine fuzzy logic variables (step 240) which are subsequently used to determine a second injection rate for the first component of the mixture (step 245). From the description of figure 2 the skilled person will further derive that the process of figure 2 uses the CMP system depicted in figure 1 which includes an in-line refractometer for measuring the index of refraction of the liquid of the slurry in the vessel by detecting the light reflected off the interface between the slurry and the prism (see page 5, lines 17 to 21 and page 9, lines 5 to 10) and which also includes a flow rate sensor for measuring the flow rate of the CMP slurry out of the vessel. The use of the signal of this flow rate sensor for adjusting the flow rate of the first component is stated to be explained in more detail with reference to figures 2 to 5 (see page 6, line 19 to page 7, line 2).

In full agreement with the flowchart of figure 2 the description teaches the skilled person that the concentration determined in step 230 and the flow rate determined in step 235 are used in step 240 to determine fuzzy logic parameters or variables (see points 1.4.4 to 1.4.6 above) which in step 245 are then used to determine a second injection rate or pump stroke for the first component of the mixture. He is further taught that, as an example, steps 230 to 245 can be performed within 30 seconds (see page 10, lines 9 to 12).

Hence the application as originally filed and particularly the description of the specific embodiment is silent with respect to the use of any other, let alone a conventional, control system. To the contrary, its only teaching is the use of a fuzzy logic control system. The fuzzy logic control is not described as only "optional" (or "preferred") nor that it may be replaced by a conventional control system (see point 1.7.6 above).

This view is additionally supported by page 13, lines 7 to 16 of the application where it is stated that the improved inventive method results in a thirty second optical detection cycle and due to the fuzzy logic control system "provides a faster and more accurate response that will not overshoot the intended target and that will also not oscillate around the target". This paragraph clearly leads the skilled person to the conclusion that the invention needs the use of a fuzzy logic control system and not to a conventional control system since his general knowledge of process control (see point 1.6) tells him that these disadvantages particularly concern conventional control systems which are thus to be avoided. In view of the problem to be solved (see point 1.3.2 above) the invention as presented by the description and figures is for a fast and accurate method for controlling the oxidiser concentration in the CMP slurry, i.e. the fuzzy logic control system.

1.7.7 Consequently, the absence from the method of claim 1 of the main request of the use of fuzzy logic variables is not directly and unambiguously derivable from the specification as originally filed, contrary to Article 123(2) EPC.

1.7.8 Taking account of point 1.7.7 the appellant's further arguments relating to the other features missing in claim 1 as addressed by the Board, therefore need not be dealt with.

The Board nevertheless remarks that decision T 1067/97 (supra), which was quoted by the appellant for the first time at the oral proceedings, is not considered relevant since it actually concerns the issue of an intermediate generalisation without basis in the description due to the incorporation into the claim of a particularly preferred molar ratio (which was only disclosed in combination with other features) for the originally already claimed developer was objected to in inter-partes proceedings. In the present case there was not even a control mentioned in the original claims. As soon as a concentration control is added to the claimed method, the simple question is: which type of control is at all disclosed? That question finds its answer in point 1.7.6 above. Further, the application as originally filed underlying case T 1067/97 had a European style description comprising a counterpart to the claims and intermediate fall back positions and thus is not comparable with the US style description of the present application which does not contain a counterpart to the original claims, let alone any intermediate fall back positions for the concentration control, besides the single embodiment.

Replacement first and second auxiliary requests

1.8 The above conclusion in point 1.7.7 with respect to claim 1 of the main request applies mutatis mutandis to the claims 1 of the replacement first and second auxiliary requests which identically do not contain these fuzzy logic features (see points VIII and IX above).

The Board therefore concludes that the claims 1 of the replacement first and second auxiliary requests neither comply with the requirement of Article 123(2) EPC. The replacement first and second auxiliary requests are therefore not allowable.

Replacement third auxiliary request

1.9 Claim 1 of the replacement third auxiliary request is based on the process steps 205 to 260 of figure 2 (with the acceptable omission of the optional process step 225) and page 7, lines 21 to 23. The Board is therefore satisfied that claim 1 of this request complies with Article 123(2) EPC.

1.9.1 The Board is also satisfied that by the amendments made in claims 1-4 of this auxiliary request the clarity objections concerning claims 1 and 3 of the request underlying the impugned decision, raised in points 4.1 and 4.2 of its communication, have been overcome. Claims 1-4 of the replacement third auxiliary request are therefore considered to comply with Article 84 EPC as far as these issues are concerned.

2. Remittal to the department of first instance (Article 111(1) EPC)

2.1 The Board has come to the conclusion that the subject-matter of the replacement third auxiliary request meets the formal requirements and therefore, overcomes the main reasons for refusing the present patent application (see point III above).

2.2 Process claim 1 of the replacement third auxiliary request has been considerably amended compared to the process claim 1 underlying the impugned decision by incorporating from the description further process features linked to the use of the fuzzy logic variables (see point X above) whereby a fresh case has been created so that it is not appropriate for the Board to further deal with it.

2.3 The Board therefore considers it appropriate to remit the case in accordance with Article 111(1) EPC to the department of first instance for further prosecution on the basis of the claims 1-4 of the replacement third auxiliary request so that it firstly can decide whether or not an additional search is necessary (the system claims have been deleted), and secondly, can proceed to the assessment of inventive step. Thereby the appellant also has the benefit of having the case examined with respect to inventive step without loss of an instance.

Furthermore, the description has not yet been adapted to the present request and therefore contains passages which are inconsistent with claim 1.