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AssigneeHitachi, Ltd.
InventorsAtsushi Shimoda, Masahiro Watanabe, Syunji Maeda, Hiroshi Goto, Tadashi Suzuki
Estimating the term…
The present invention provides an image detection system capable of picking up a high resolution image of the surface condition of a circuit pattern-formed wafer without being affected by steep pattern steps, discontinuous reflectance distributions and optically transparent substances which are formed after resist patterns are formed and removed. A defect detection apparatus using such an image detection apparatus is also provided by the invention. The present invention is implemented by a configuration comprising a scanning stage having a sample mounted thereon, an image pickup system for picking up a surface image of the sample, height detection means for detecting the surface height of the sample at plural points including two points which are respectively on the opposite sides of the image pickup position in the scanning direction, sample height calculation means for calculating the height of the sample at the image pickup position by using the detected heights and focusing means for focusing the image pickup system by using the calculated sample height.
An image detection method comprising the steps of:
An image detection apparatus comprising:
A defect detection method comprising the steps of:
A defect detection method comprising the steps of:
A defect detection method comprising the steps of:
A defect detection method comprising the steps of:
A defect detection apparatus comprising:
A defect detection apparatus comprising:
Dependencies are inferred from the claim text.
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From the US filing history. Foreign family members aren’t listed.
Devices for focusing: using auxiliary sources, detectors
Inspecting patterns on the surface of objects: patterns showing highly reflecting parts, e.g. metallic elements
Image analysis: inspection of images, e.g. flaw detection
Industrial image inspection: using an image reference approach
Term ended 11 Aug 2024 (estimated)
The present invention relates to an image detection apparatus which captures a high resolution surface image of a sample made of various materials and having an uneven surface, such as a semiconductor wafer on which fine circuit patterns are formed, and a defect detection/measurement apparatus using that image. In particular, this invention is preferably applicable to an apparatus which employs a high resolution and narrow focal depth optical system such as an optical microscope using a DUV light source.
As systems for picking up a high resolution surface image of a sample made of various materials and having an uneven surface, there are pattern defect detection apparatuses for semiconductor wafers.
In Japanese Patent Laid-Open No. 4-76450, a focus detection method is disclosed for semiconductor wafer pattern defect detection apparatuses. In this conventional method, a reticule inserted in an illuminating light path is projected onto the sample via an objective lens and an image of the reticule pattern reflected from the sample is shaded by another reticule placed in the detection light path. The height of the sample is detected by the increase or decrease in the quantity of light which has passed the reticule.
FIG. 1(a) is a sectional view of a semiconductor wafer, FIG. 1(b) illustrate an image of the uppermost layer pattern, FIG. 1(c) is a sectional view of a semiconductor wafer and FIG. 1(d) is a diagram for explaining errors induced when wafer heights are detected by optical means;
FIG. 2 is a schematic diagram showing a general configuration of a semiconductor wafer defect detection apparatus according to a first embodiment of the present invention;
FIG. 3 is a diagram for explaining wafer surface image pickup operation;
Embodiments of the present invention will thereinafter be described with reference to the drawings.
Described below are embodiments of optical inspection systems according to the present invention to inspect/measure fine circuit patterns formed on a semiconductor wafer, an object to be inspected. Defect inspection of a fine circuit pattern formed on a semiconductor wafer or the like is done by comparing the pattern with a reference pattern or a pattern of the same kind on the wafer. In this comparison inspection method, however, reliability of the inspection result is much affected by the quality of the obtained image since the image must be compared with a similar image. Image quality may be deteriorated by various factors and the largest factor is defocus. To pick up a high-resolution image of a fine circuit pattern without defocus, it is necessary to accurately detect the surface height of the sample and keep the focus aligned to the surface.
FIG. 1 explains how height errors are induced when the height of a wafer is detected by optical means. FIG. 1(a) is a cross sectional view of the semiconductor wafer. The semiconductor wafer has multiple circuit pattern layers stacked and insulated with each other by optically transparent inter-layer films 1. Circuit patterns on the respective layers are connected with each other through contact holes 2. Used to find what problem remains to be solved in each manufacture process is an optical inspection system. Immediately after a process is completed, the optical inspection system is used to pick up an image of a fine circuit pattern for detecting defects, such as short and open, in the circuit pattern. To sensitively detect micro-defects, the sample surface must be aligned to within the focal depth 3 so that a clear pattern image can be obtained. A broken line 4 is drawn along the center of the focal depth when the wafer surface is positioned ideally. As the result, a clear image of the uppermost layer circuit pattern 5 is obtained as shown in FIG. 5(b). Note that the lower most layer pattern 6 is defocused and its image is not picked up. For inspection of a semiconductor wafer having multiple layers, it is necessary to identify which manufacture process involves a problem and must be improved. For this purpose, after a circuit pattern is formed, it is preferable to detect only the defects in the uppermost layer by defocusing the lower layer patterns so that the inspection result is not affected by defects in the lower layers.