copyright 1997 Donald M. Cameron
"There is good reason for adopting a purposive approach to the to the construction of the patents. It is not the inventor who drafts these texts. It is usually a legal advisor who presumably has some knowledge of the particular art to which the patent relates but who, for legal reasons related to the patenting process, adopts wording quite different from that in which most inventors would explain their invention. "
At p. 260-261
"The question which is left unanswered by the Catnic decision is whether knowledge at the date of the patent of the existence of variants generally, or of the particular variant in issue, is necessary in order to find that a variant was intended by the patentee to fall within the scope of the patent. As I understand counsel for the defendant's argument it is that since ion implantation was not known as a practical method of doping the source and drain as of the date on which the application for the patent was filed, it cannot possibly have been the patentee's intention to include that variant (if minor variant or equivalent it is) within the scope of the patent. I cannot disguise the fact that I have some difficulty interpreting part of the text of the Catnic decision, particularly those sentences which for purposes of convenience I will set out again below:
Nor does it [the question as to whether the patentee intended to exclude minor variants from his claim] arise unless at the date of publication of the specification it would be obvious to the informed reader that this was so. Where it is not obvious, in the light of the then-existing knowledge, the reader is entitled to assume that the patentee thought at the time of the specification that he had good reason for limiting his monopoly so strictly and had intended to do so even though subsequent work by him or others in the field of invention might show the limitation to have been unnecessary.
The Catnic decision did not deal with a situation where the variant in issue was not fully understood at the date of the patent. Nor did it deal with a situation in which it was alleged that there were no variants in existence at the date of the patent. I understand the portion of the decision in the Catnic case set out above to stand for no more than that, in determining whether a patentee intended to exclude equivalents or minor variants from his claims, that construction has to be determined as of the date of the patent."
"In my view, the relevant date to consider is the date as of which the patent application is filed. As counsel for the defendant argues such a conclusion accords with the basis principles governing the interpretation of any legal document, that such documents are interpreted in the light of the circumstances existing at the time they are written. It accords with section 52 to 54 of the Patent Rules, C.R.C. 1978, c. 1250 which state that no new matters can be added by amendment to an application. It avoids bizarre results which might arise in a fast moving area of technology if the issue of the patent is delayed. With respect to this last, it was noted that the issue of a patent can be held up for many years in the patent office when conflict proceedings are instituted. And, lastly, Mr. Justice Noel in American Cyanamid Co. v. Charles E. Frosst and Co. (1965), 47 C.P.R. 215 at p. 295,  2 Ex. C.R. 355, 29 Fox Pat. C. 153 at pp. 226-7 made reference to Frost, Patents, Law and Practice, 4th ed., at p. 204, and quoted a passage part of which reads as follows:
"It must not, however, be forgotten that the meaning of words is liable to change with progress of science and discovery, and a term which for the purpose of the specification, is sufficiently accurate, may, in future years include that which will not answer the purpose the patentee has in view. In such a case the specification will be read with to the state of knowledge at the time it was prepared..." [Emphasis added]"
At p. 265??Patentees intention re: minor variants
It must be asked, in accordance with the Catnic test, whether the patentee intended to exclude minor variants relating to the particular aspect of the patent in issue from the scope of the patent claim. As already noted, that intention is to be found in the text of the patent read in light of surrounding circumstances, particularly the knowledge of one skilled in the art. Applying that test, I do not find that the patentee intended to exclude minor variants in the way the source, drain and gate were doped from the scope of the patent in issue in this case.
In my view, the text of claim one does not expressly exclude such minor variants or equivalents. The claim does not specify that the diffusion has to take place by way of vapor deposition, although that is the process described in the preferred embodiment. The claim does not specify that the diffusion must occur by placing a film of impurity on the surface of and letting it soak in. The claim asserts no specificity with respect to the manner in which the impurities are to be introduced. The aspect in issue is described as "diffusing impurities into the semiconductor substrate to form the diffusion layer ... diffusing impurities into the silicon layer to render it conductive". It is clear from the evidence that the word "diffusing" or "diffusion" was and is used in a variety of ways, some more precise than others. I cannot conclude that the patentees intended to exclude, from the scope of claim one of the patent, methods of placing impurities into the source, drain and gate regions which do not involve an initial step of coating the surface of the exposed substrate with the impurity atoms and allowing them to soak into the area immediately below."
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