Electricity: measuring and testing – Fault detecting in electric circuits and of electric components – Of individual circuit component or element
Reexamination Certificate
2003-05-07
2004-03-09
Pert, Evan (Department: 2829)
Electricity: measuring and testing
Fault detecting in electric circuits and of electric components
Of individual circuit component or element
C250S310000
Reexamination Certificate
active
06703850
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a manufacturing method and device of a board having a fine circuit pattern such as a semiconductor device or a liquid crystal and more particularly to a pattern inspection art of a semiconductor device and a photo mask such as a pattern inspection art on a wafer during the semiconductor device manufacturing process and a comparison inspection art using an electron beam.
Inspection of a semiconductor wafer will be explained as an example.
A semiconductor device is manufactured by repeating the step of transferring a pattern formed on a photo mask onto a semiconductor wafer by the lithographic process and etching process. In the semiconductor device manufacturing process, acceptance or rejection of the lithographic process, etching process, and others and an occurrence of a foreign substance greatly affect the yield rate of semiconductor devices, so that to detect an error or failure generation early or beforehand, the method for inspecting a pattern on a semiconductor wafer in the manufacturing process has been conventionally executed.
As a method for inspecting a defect existing in a pattern on a semiconductor wafer, a defect inspection device for irradiating white light to a semiconductor wafer and comparing the same kind of circuit patterns of a plurality of LSIs using an optical image is in practical use and the outline of the inspection method is described in “Monthly Semiconductor World”, August issue, 1995, pp 96 to 99. As an inspection method using an optical image, a method for imaging an optically irradiated area on a board by a time delay integration sensor and detecting a defect by comparing the image with a preinput design characteristic is disclosed in Japanese Patent Application Laid-Open 3-167456 and a method for monitoring image deterioration at the time of image acquisition and correcting it at the time of image detection and thereby executing a comparison inspection using a stable optical image is disclosed in Japanese Patent Publication 6-58220. When a semiconductor wafer in the manufacturing process is inspected by such an optical inspection system, pattern remains and defects having a silicon oxide film or photosensitive resist material on the surface through which light transmits cannot:be detected. Etching remains and an unopened failure of the minute contact hole lower than the resolution of the optical system cannot be detected. Furthermore, a defect generated at the step bottom of the line pattern cannot be detected.
As mentioned above, as refinement of the circuit pattern, complication of the circuit pattern shape, and diversification of the material advance, defect detection by an optical image becomes difficult, so that a method for comparing and inspecting the circuit pattern using an electron beam image having a higher resolution than that of an optical image is proposed. When the circuit pattern is to be compared and inspected by an electron beam image, to obtain a practical inspection time, it is necessary to obtain an image at a very higher speed than that of observation by a scanning electron microscope (hereinafter abbreviated to SEM). It is also necessary to ensure the resolution of the image obtained at high speed and the SN ratio of the image.
As a pattern comparison inspection device using an electron beam, in J. Vac. Sci., Tech. B, Vol. 9, No. 6, pp 3005 to 3009 (1991), J. Vac. Sci., Tech. B, Vol. 10, No. 6, pp 2804 to 2808 (1992), Japanese Patent Application Laid-Open 5-258703, and USP 5502306, a method for irradiating an electron beam having an electron beam current 100 times or more: (10 nA or more) of that of a normal SEM to a conductive board (X-raymask, etc.), detecting any of generated secondary electrons, reflected electrons, and transmitted electrons, and comparing and inspecting images formed from the signal and thereby automatically detecting a defect is disclosed.
As a method for inspecting or observing a circuit board having an insulator by an electron beam, in Japanese Patent Application Laid-Open 59-155941 and Electron, Ion Beam Handbook (Nikkan Kogyo Shimbunsha), pp 622 and 623, a method:for obtaining a stable image by irradiating a low velocity electron beam of 2 keV or less so as to reduce the effect of charging is disclosed. Furthermore, in Japanese Patent Application Laid-Open 2-15546, a method for irradiating ions from the back of a semiconductor board is disclosed and in Japanese Patent Application Laid-Open 6-338280, a method for canceling charging an insulator by irradiating light to the surface of a semiconductor board is disclosed.
By a large current and low velocity electron beam, it is difficult to obtain an image with high resolution due to the space charge effect. However, as a method for solving it, in Japanese Patent Application Laid-Open 5-258703, a method for decelerating a high velocity electron beam immediately before a sample and irradiating it practically as a low velocity electron beam on the sample is disclosed.
As a method for obtaining an electron beam image at high speed, a method for obtaining an electron beam image by continuously irradiating an electron beam on a semiconductor wafer on a sample carrier by continuously moving the sample carrier is disclosed in Japanese Patent Application Laid-Open 59-160948 and Japanese Patent Application Laid-Open 5-258703. As a secondary electron detection device used in a conventional SEM, a constitution of a scintillator (aluminum deposited phosphor), a light guide, and a photoelectric multiplier is used. However, this kind of detection device detects light emitted from the phosphor, so that the frequency responsibility is bad and the detection device is not suited to high-speed formation of an electron beam image. To solve this problem, as a detection device for detecting a secondary electron signal of high frequency, a detection means using a semiconductor detector is disclosed in Japanese Patent Application Laid-Open 5-258703. Furthermore, an art for scanning an electron beam at the same location on a semiconductor wafer on a sample carrier once or several times at high speed by continuously moving the sample carrier, obtaining an image at high speed, and automatically inspecting a defect by image comparison is disclosed in Japanese Patent Application Laid-Open
10-294345.
When the circuit pattern in the manufacturing process of a semiconductor device having a minute structure is inspected using the aforementioned optical inspection system of the prior art, remains of a silicon oxide film which is an optically transmissive material and whose optical distance depending on the optical wave length and refractive index used for inspection is sufficiently small and a photosensitive resist material cannot be detected and it is difficult to detect etching remains whose linear short width is smaller than the resolution and an unopened failure of the minute contact hole.
On the other hand, in observation and inspection using an SEM, the conventional electron beam image forming method using an SEM requires an extremely long time, so that inspection of the circuit pattern overall a semiconductor wafer requires an extremely longtime. Therefore, to obtain a practical throughput in the semiconductor device manufacturing process, it is necessary to obtain an electron beam image at a very high speed, ensure the S/N ratio of an electron beam image obtained at high speed, and maintain the predetermined accuracy. When the material constituting the circuit pattern to be inspected is formed by an insulating material such as a photo resist or a silicon oxide film and formed by coexistence of an insulating material and a conductive material, it is difficult to obtain an image of stable brightness by inspection by an electron beam and obtain the predetermined inspection accuracy. The reason is that when an electron beam is irradiated to a substance, secondary electrons are generated from the portion, but since the irradiated current is not equal to the secondary electron current, when the inspection object is an i
Miyai Hiroshi
Morioka Hiroshi
Nozoe Mari
Saiki Keiichi
Shinada Hiroyuki
Hitachi , Ltd.
Kobert Russell M.
Mattingly Stanger & Malur, P.C.
Pert Evan
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