Image analysis – Applications – Manufacturing or product inspection
Reexamination Certificate
2000-10-10
2004-04-13
Mehta, Bhavesh M. (Department: 2625)
Image analysis
Applications
Manufacturing or product inspection
C382S145000, C219S121690, C219S216000
Reexamination Certificate
active
06721443
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a method of reading a mark and an apparatus for the same in which a mark formed on a functional device formation body where predetermined functional devices are formed on a base is optically read.
2. Description of the Related Art
A magnetic head slider used when recording/reproducing data on/from an information recording media such as a fixed disk device is generally fabricated using a photolithography technique, a thin film formation technique, an etching technique, a polishing process technique and the like as follows: A plurality of thin film magnetic head devices is formed on a wafer and the wafer is cut so as to be separated into individual magnetic head sliders, each of which includes at least one of the thin film magnetic head device.
When manufacturing a large quantity of magnetic head sliders, an identification mark is provided on a predetermined surface of each magnetic head slider through a series of manufacturing processes. This identification mark provides, for example, manufacturing information of the magnetic head slider, such as date manufactured, manufacturing specifications, material used, manufacturing number and the like. The identification mark is provided for the purpose of managing the manufacturing history of the magnetic head slider. With mass-manufacturing, process management utilizing manufacturing information provided through the identification code makes it possible to avoid confusion of products with different manufacturing specifications and to keep track of the number of manufactured products and the whole manufacturing process accurately. When a defective part is used in a product during the manufacturing process, or when a product fails in performance or the like is found after completing the manufacturing process, a scale of occurrence of the defect is quickly and accurately detected and the defective products are effectively removed by performing a performance evaluation or the like for every identification code of a series of products manufactured.
Here, examples of the identification mark generally provided are an identification mark constituted with a string of character symbols as an arrangement of characters or numbers (called as a “character symbol” hereinafter) and an identification mark constituted with a graphical pattern as an arrangement of predetermined graphics. As to the identification mark constituted with the string of character symbols, a single character symbol or a combination of a plurality of character symbols indicates the specific manufacturing information. As to the identification mark constituted with the graphical pattern, the number, shape, size, arrangement or the like of the graphical symbols indicates the specific manufacturing information.
An example of a method of providing the identification mark on the magnetic head slider and a method of forming the identification mark is a method in Japanese Patent Laid-open No. Hei 9-50606 applied by this applicant. In this bulletin, two types of ultra-minute identification marks, where one is constituted with a string of character symbols and the other is constituted with a graphical pattern, are provided on a surface of a magnetic head slider, on the surface thin film magnetic head devices being formed, to indicate manufacturing information of the magnetic head slider. In this case, the identification code constituted with the string of character symbols is formed simultaneously with a magnetic layer as a part of the thin film magnetic head device, whereas the identification mark constituted with the graphical pattern is formed on a predetermined region on a protection film formed on the surface of the thin film magnetic head by irradiating a laser.
The ultra-minute identification mark provided on the magnetic head slider is visually identified using a microscope or the like by a worker or the like. The identification mark is just an arrangement of characters and graphics, so the identification mark is converted into corresponding manufacturing information by the worker or the like using a conversion chart. If needed, conversion may be performed more than once. In this way, the necessary identifying information is obtained from the identification mark provided on the magnetic head slider.
The above-described conventional method of reading the identification mark of the magnetic head slider has the following problems to be improved.
First, with the conventional method of reading the identification mark, onerous work such as the recognition of the ultra-minute identification mark, conversion into the manufacturing information or the like needs to be performed using manpower. Therefore, conducting the work requires a lot of time, which is a great obstacle to improvement of productivity.
Second, recognition of the ultra-minute identification mark, conversion into the manufacturing information, and the like are performed using manpower, so that there exists the risk of a mistake caused by human error such as a mistake in reading character symbols and a mistake in counting numbers of graphical symbols when recognizing the identification mark, a mistake in conversion from the identification number into the manufacturing information or the like.
In the semiconductor field, for example, as in Japanese Patent Laid-open No. Hei. 8-130171, No. Hei 7-141461 and No. Hei 6-52138, a technique to optically read the identification mark provided on each semiconductor wafer is disclosed, for example.
In these bulletins, the technique for reading the identification mark is disclosed on the assumption that the identification mark is formed on a semiconductor wafer itself, i.e., a base where semiconductor devices are formed. However, as in the aforementioned Japanese Patent Laid-open No. Hei 9-50606 applied by this applicant, a technique for reading the identification mark formed on a portion, for example, a part of the thin film magnetic head device or the protection film other than the base has not been disclosed. Further, the above three bulletins regarding a semiconductor process are described based on the premise that the identification mark is read in a wafer process and there is no description with regard to management of the identification information after the base is separated into individual members (semiconductor chip).
SUMMARY OF THE INVENTION
This invention is designed to overcome the aforementioned problems. It is an object of the invention to provide a method of reading a mark and an apparatus for the same in which even a mark formed on a portion other than a base in a functional device formation body such as a magnetic head slider can be accurately and quickly read.
According to the invention, the method of reading a mark, formed on a functional device structure layer or a protection layer in a functional device formation body including at least a base, the functional device structure layer including a predetermined functional device structure formed on the base through a thin film process and the protection layer covering the functional device structure layer, the method includes steps of irradiating an illumination light of an normal incident illumination onto the functional device formation body and reading the mark formed on the functional device structure layer or the protection layer based on a reflected light from the functional device formation body.
Here, the “functional device structure” is a device structure having a predetermined function including a magnetic, electric, optic function such as a magnetic recording/reproducing device structure, a semiconductor device structure, an optical recording/reproducing structure, or the like. Examples of the “functional device formation body” are a magnetic head slider wherein a magnetic recording device or a magnetic reproducing device are formed, a semiconductor chip wherein a semiconductor device is formed, an optical pickup wherein an optical recording/reproducing device is formed or the like. The “mark” denotes an object of perception used
Bayat Ali
Mehta Bhavesh M.
Oliff & Berridg,e PLC
TDK Corporation
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