Radiant energy – Photocells; circuits and apparatus – With circuit for evaluating a web – strand – strip – or sheet
Reexamination Certificate
1999-11-23
2002-06-04
Le, Que T. (Department: 2878)
Radiant energy
Photocells; circuits and apparatus
With circuit for evaluating a web, strand, strip, or sheet
C356S237400
Reexamination Certificate
active
06399957
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an appearance inspection method and appearance inspection apparatus for performing appearance inspection for uneven exposure, de-focusing, poor coating, scratches, and the like of an inspection object, by irradiating illumination light on objects to be inspected such as substrates which are used in the production of micro devices such as semiconductor elements, imaging elements (CCDs, etc.) liquid crystal displays and thin film magnetic heads.
2. Description of the Related Art
Recently with the advance in high integration of semiconductor devices, in the fields of inspection and measurement, the resolution which is required with respect to inspection devices for observing and inspecting for defects in patterns on wafers and reticules has followed continual refinements with each successive generation.
Despite the low level of demand for improvements in resolution for inspection in the area of appearance inspection for inspecting for uneven coating, uneven exposure, de-focusing, poor coating, scratches and the like of resist on a wafer, the importance which is being placed on reducing production costs has resulted in expectations for realizing an automated inspection device for automatically carrying out the aforementioned appearance inspections which have heretofore relied upon visual inspection.
In the past, for this kind of appearance inspection apparatus, a method is adopted where the entire wafer surface being the object to be inspected, on an inspection stage, is illuminated with a uniform light source, and the entire wafer surface is photographed at one time using a two-dimensional camera and taken as an inspection image. Furthermore, Japanese Patent Application, First Publication No. 8-75661, discloses a method for inspecting for defects such as scratches, impurities and stains on substrates, by receiving diffracted light from repeated patterns on the substrate.
Since when a substrate is inspected according to this method, the same level of throughput is required as with a conventional inspection carried out visually by a trained inspector, it is necessary for example, to make the amount of time taken to photograph an image of the substrate the same as that taken in a visual inspection. Hence, the method of photographing the entire substrate at the same time has recently been adopted in an attempt to increase throughput.
However, the following type of problems are to be found with regard to the aforementioned conventional appearance inspection methods and appearance inspection apparatuses.
The detection of the above-mentioned defects differs greatly according to the type of fault. For instance, in the inspection for impurities and scratches on the surface of the object to be inspected, through the use of light illumination, scattered light emanating from a defect on the surface being inspected is utilized. Additionally, in the inspection for uneven coating, uneven exposure, de-focusing and poor coating on the resist, the diffracted light which is generated from the object to be inspected by light illumination is used.
What is more, the main objective of automating an inspection which has until now relied upon visual inspection, necessitates the implementation of an inspection which follows the inspection procedure which has heretofore been carried out by an inspector. Accordingly, it is necessary to follow in order the several inspection steps which, with conventional appearance inspection methods and appearance inspection apparatuses, entail such things as separately photographing the substrates in accordance with the aforementioned various inspection procedures. Hence there is the disadvantage that inspection throughput time is increased.
SUMMARY OF THE INVENTION
The present invention takes into consideration the above points with the object of providing an appearance inspection method and an appearance inspection apparatus which has the ability to shorten the inspection throughput time, even when carrying out automatically the same inspection as that carried out visually.
In order to achieve the above objective, an appearance inspection method according to the present invention is characterized in comprising: a first step for inspecting an object to be inspected by illuminating the object to be inspected mounted on a first stage and receiving scattered light therefrom, a second step for inspecting the object to be inspected by illuminating the object to be inspected mounted on a second stage and receiving diffracted light therefrom, and a transfer step for transferring the object to be inspected between the first stage and the second stage so that either one of the first step and the second step is carried out after the other.
Accordingly, with the appearance inspection method of the present invention, in the case where the object to be inspected is a substrate which has been coated with resist, then while inspecting in the first step for scratches and impurities on the surface of the object to be inspected using the scattered light generated from the object to be inspected on the first stage, it is possible to inspect concurrently in the second step for uneven coating, uneven exposure, de-focusing and poor coating on the resist using the diffracted light generated from the object to be inspected on the second stage. Furthermore, when either one of the first step or the second step is completed, then in the transfer step the object to be inspected is transferred between the first stage and the second stage. After this, the inspection of the other step is carried out on the transferred object to be inspected.
As a result, with this appearance inspection method, the effect is obtained that it is possible to prevent a lengthening in the throughput time even when a plurality of inspections are automatically carried out, while maintaining the same functions as for the conventional inspection which is carried out visually.
With an appearance inspection method of an embodiment of the present invention, in accordance with the transfer by the transfer step of the object to be inspected from one stage of either the first stage and the second stage, a new object to be inspected is transferred to the one stage.
According to this appearance inspection method, it is possible to simultaneously execute the first step and the second step concurrently, enabling a substantial improvement in the inspection throughput.
With an appearance inspection method of another embodiment of the present invention, prior to inspection of the object to be inspected, an alignment step is carried out for aligning the object to be inspected at a predetermined location by moving a stage.
According to this appearance inspection method, it is possible to perform inspection at the optimum position corresponding to the object to be inspected, and thereby improve inspection accuracy. Furthermore, the inspection not only makes it possible to detect the presence of defects, but also enables the coordinate position where the defects occurs to be specified. Therefore, it is easy to undertake a subsequent so-called micro inspection for making a concentrated inspection of the region.
With an appearance inspection method of another embodiment of the present invention, after completion of one step of the first and second steps, the object to be inspected is pre-aligned to a direction required for the other step, while remaining mounted on the stage used for the one step, after which the object to be inspected is transferred to the stage of the other step by the transfer step.
According to this appearance inspection method, inspection at the optimum position corresponding to the object to be inspected is also possible in the other step, enabling an improvement in inspection accuracy. Furthermore, as with the first inspection, it is possible to specify the coordinate position where the defect occurs, and hence post inspection micro inspection can be easily performed. In addition, since it is no longer necessary to provide a separate m
Le Que T.
Luu Thanh X.
Nikon Corporation
Oliff & Berridg,e PLC
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