Radiant energy – Irradiation of objects or material – Irradiation of semiconductor devices
Reexamination Certificate
2000-11-27
2002-10-08
Anderson, Bruce (Department: 2881)
Radiant energy
Irradiation of objects or material
Irradiation of semiconductor devices
C250S297000, C250S310000
Reexamination Certificate
active
06462346
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an inspecting apparatus and an inspecting method of inspecting a defect of a mask used in an electron beam exposure system which carries out a pattern transcription by using an electron beam.
2. Description of the Related Art
Conventionally, a method of emitting a laser light to a mask, and comparing a pattern generated through its transmission light or its reflection light with a reference pattern to detect a defect of the mask has been well known as a method of inspecting a pattern of a mask used in an electron beam exposure system.
However, when a defect of a stencil mask or a membrane mask used in a recent electron beam exposure system is inspected, a laser light is not transmitted through the membrane. Thus, there is no method but the usage of the reflection light. It is easy to use the reflection light of the laser light to then inspect the defect. However, a film thickness of a scattering heavy metal of the membrane mask is typically thin. Hence, it is below a wave length of the laser light. This may result in a fear that the detection is impossible.
For this reason, the method of inspecting the defect of the membrane mask uses a transmission electron microscope (TEM) which uses an electron beam to thereby inspect the defect of the membrane mask. In this TEM, as shown in a schematic configuration of
FIG. 1
, an electron beam EB emitted by an electron gun
51
mounted above a mask M is converged by an optically emitting system
52
containing electron lens
53
,
54
, to be emitted to the mask M. The electron beam transmitted through the mask M is passed through an aperture
55
made of Cu material to be detected by an electron detector
56
. The pattern of the mask M is detected on the basis of a value of a current detected by the electron detector
56
. The detected pattern of the mask M is compared with a reference pattern to thereby inspect the defect of the mask M. This usage of the electron beam enables the defect of the stencil mask or the membrane mask to be detected. Such technique is disclosed in, for example, Japanese Laid Open Patent Application (JP-A-Heisei, 4-361544), although it does not describe the membrane mask or the stencil mask in particular.
A conventional apparatus for inspecting a defect of a mask is constituted as an apparatus dedicated to a mask inspection. For this reason, a factory for manufacturing a semiconductor apparatus requires an equipment of a mask inspecting apparatus, apart from an apparatus for manufacturing a semiconductor apparatus. It requires a reservation of space to install the mask inspecting apparatuses in addition to a space to install the apparatus for manufacturing the semiconductor apparatus in the manufacturing factory. Also, this type mask inspecting apparatus requires the configuration similar to that of the electron beam exposure system, as an electron gun or an optically emitting system for emitting an electron beam to a mask. This results in a problem that the mask inspecting apparatus becomes larger and more expensive.
Also, in the conventional inspection of the mask defect, the electron detector detects the electron beam transmitted through the mask to thereby detect the pattern of the mask. Then, the detected pattern is compared with the reference pattern. Thus, there may be a fear that a trouble is induced in a reliability of the mask defect inspection. That is, the detected pattern is made into signals in which the detected pattern is converted into binary values at a fine region unit. A binary signal of a fine detecting region of the detected pattern is compared with a binary signal of a region corresponding to the fine detecting region of the reference pattern. Accordingly, a portion where both the signals are not in coincidence with each other is judged as the defect of the mask. However, in this case, if an error is induced in a reference level when each of the fine regions of the detected pattern is converted into the binary value, the reliability of the binary value itself in which each of the fine regions of the detected pattern is converted into the binary value is dropped, which results in a drop of a reliability of the defect inspection.
Japanese Laid Open Patent Application (JP-A-Showa, 63-38149) discloses a pattern defect inspector as described below. The pattern defect inspector is provided with a device for scanning on a substrate in which one or more rectangular patterns are formed, a device for detecting a signal occurring from the substrate through the scanning operation, a device for treating the detected signal and thereby obtaining a binary information, a device for converting the binary information into a plurality of rectangular pattern information, a device for accumulating therein the rectangular pattern information, and a device for comparing the rectangular pattern information with a standard data corresponding to the rectangular pattern information.
SUMMARY OF THE INVENTION
The present invention is accomplished in view of the above mentioned problems. Therefore, an object of the present invention is to provide a mask inspecting apparatus which can inspect a mask by using an electron beam exposure system and accordingly cancel out a need for an independent installation of another mask inspecting apparatus. Another object of the present invention is to provide a mask inspecting method which can improve a reliability in an inspection of a defect of a mask.
In order to achieve an aspect of the present invention, a mask inspecting method, includes: (a) providing an electron beam exposure system used for patterning a wafer with a mask; (b) emitting electrons to the mask from the electron beam exposure system; (c) detecting an electron passing through the mask of the emitted electrons; and (d) inspecting the mask for a defect based on a detected result of the (c).
In this case, the (b) is performed such that the electrons emitted from the electron beam exposure system are not emitted to the wafer.
Also in this case, the mask inspecting method, further includes: (e) performing an exposure to the wafer through the mask for patterning by using the electron beam exposure system when the mask has no defect as a result of the (d).
Further in this case, in the (b) the electrons are emitted from the electron beam exposure system in such a manner that the (e) is performed.
In this case, the mask inspecting method, further includes: (f) providing a reference pattern data indicating a reference pattern of the mask; and (g) calculating an area rate implying a ratio of a black pattern to a white pattern included in a portion data corresponding to a inspecting region of the mask of the reference pattern data, and wherein the (d) includes inspecting the mask for the defect based on the detected result of the (c) and the area rate.
Also in this case, the (c) includes detecting a strength of the electron passing through the mask, and the mask inspecting method, further includes: (h) providing a reference pattern data indicating a reference pattern of the mask; and (i) calculating an area rate implying a ratio of a black pattern to a white pattern included in a portion data corresponding to a inspecting region of the mask of the reference pattern data, and wherein the (d) includes inspecting the mask for the defect based on the strength of the electron and the area rate.
Further in this case, the mask inspecting method, further includes: (j) calculating a correction value indicating a relation between the strength of the electron and the reference pattern, and wherein the (d) includes inspecting the mask for the defect based on the strength of the electron and the correction value, and the area rate.
In this case, the (c) is performed by an electron detector, and wherein the electron detector is automatically movable from a position where the electron detector covers a position of the wafer such that the electron passing through the mask is not emitted to the position of the wafer to another position where the electron d
Anderson Bruce
Hashmi Zia R.
McGinn & Gibb PLLC
NEC Corporation
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