This application is based on and hereby claims priority to Japanese Patent Application No. 2005-176156 filed on Jun. 16, 2005, the contents of which are hereby incorporated by reference.
The present invention relates to a charged particle beam apparatus for observing, inspecting and working the surface of a semiconductor wafer, a photomask or the like sample which is liable to be charged by charged particle beam irradiation and to have its image observation hampered, and a method for generating a charged particle beam image.
Heretofore, a field emission type scanning electron microscope (FE-SEM) has been employed for the observation and pattern length measurement of a semiconductor wafer or photomask surface. Besides, a focused ion beam apparatus (FIB) has been employed for the revision of a photomask pattern. Since, however, that surface of a sample which is to be observed or to be subjected to the length measurement is wholly or partly made of a nonconductive material, the surface is charged by irradiation with charged particles, and the charging sometimes hampers the observation or length measurement, or working.
It is therefore practiced that the sample is placed in the atmospheric air or an atmosphere in which the pressure of the atmospheric air is reduced, or in any other gaseous atmosphere, and that the sample is irradiated with ultraviolet radiation, thereby to generate positive ions or negative ions and to neutralize (remove) the charges on the sample.
However, there have been problems as stated below, with the above technique wherein the sample in the reduced pressure atmosphere is irradiated with the ultraviolet radiation emitted from a deuterium lamp, thereby to generate the positive ions or negative ions and to neutralize the charges on the sample and remove the charging.
With the UV radiation, however, the neutral gas atom or molecule cannot be ionized by only the energy of one photon, and the positive ion and negative ion are formed by the energy of, for example, two photons. Therefore, there have been such problems that an efficiency for generating the ions is low, and that an intense UV radiation is required.
In order to solve these problems, in a charged particle beam apparatus wherein a secondary electron beam or the like which is emitted from a sample by irradiating the sample with a charged particle beam is detected so as to generate an image, the present invention has for its object to efficiently remove the charges of the surface of the sample by heightening the generation efficiencies of positive ions and negative ions, in such a way that the sample is irradiated with soft X-ray being higher in energy than UV radiation, in a state where the surface or vicinity of the sample charged by an electron beam or the like is held in the atmosphere or a reduced pressure atmosphere or in a predetermined gaseous atmosphere within a preliminary evacuation chamber, a sample chamber or the like.
In a charged particle beam apparatus wherein a secondary electron beam or the like which is emitted from a sample by irradiating the sample with a charged particle beam is detected so as to generate an image, the present invention makes it possible to efficiently remove the charges of the surface of the sample by heightening the generation efficiencies of positive ions and negative ions, in such a way that the sample is irradiated with soft X-ray being higher in energy than UV radiation, in a state where the surface or vicinity of the sample charged by an electron beam or the like is held in the atmosphere or a reduced pressure atmosphere or in a predetermined gaseous atmosphere within a preliminary evacuation chamber, a sample chamber or the like.
These and other aspects and advantages will become more apparent and more readily appreciated from the following description of the exemplary embodiments, taken in conjunction with the accompanying drawings of which:
Reference will now be made in detail to the preferred embodiments, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout.
In a charged particle beam apparatus wherein a secondary electron beam or the like which is emitted from a sample by irradiating the sample with a charged particle beam is detected so as to generate an image, the present invention has realized to efficiently remove the charges of the surface of the sample by heightening the generation efficiencies of positive ions and negative ions, in such a way that the sample is irradiated with soft X-ray being higher in energy than UV radiation, in a state where the surface or vicinity of the sample charged by an electron beam or the like is held in the atmosphere or a reduced pressure atmosphere or in a predetermined gaseous atmosphere within a preliminary evacuation chamber, a sample chamber or the like.
Referring to
A preliminary chamber 3 is a room which serves to mount the mask magazine 1 and to accept the mask 2 within the mask magazine 1 in a cleaned state and then temporarily keep this mask in custody, and which serves to convey the processed mask 2 into the mask magazine 1 in a cleaned state. The preliminary chamber 3 is usually held at the atmospheric pressure, but if necessary, it may well be evacuated into a low vacuum (low vacuum of from the atmospheric pressure to about 0.1 Torr) after accepting the mask 2 and closing a gate, not shown, disposed at its boundary with the mask magazine 1. Incidentally, a “room” in which the mask 2 is irradiated with soft X-ray as stated in the claims is a room in which an X-ray generator 4 is mounted, such as a subchamber 5 or the preliminary chamber 3, except a main chamber 6 in
The X-ray generator 4 is for generating the soft X-ray and irradiating the mask 2 with the soft X-ray so as to remove the charges of the mask 2 (refer to
The subchamber 5 is the room in which the surroundings of the mask 2 are evacuated into a low vacuum, and which is interposed between the preliminary chamber 3 and the min chamber 6 here.
The main chamber 6 is a room of vacuum (usually, of about 10-6 Torr), which serves to place the mask 2 on a stage 9, to scan the surface of the mask 2 being the sample (as the plane scanning in the X- and Y-directions), by a charged particle optical system 8, here, with the finely focused electron beam, and to detect and amplify the emitted secondary electrons by a secondary electron detector 7 and then generate the image (secondary electron image).
The secondary electron detector 7 is one which detects and amplifies the secondary electrons emitted from the mask 2, and which collects and then detects and amplifies the secondary electrons emitted from the mask 2 by applying a positive voltage thereto. By the way, in case of detecting the reflected electrons, light or X-rays emitted from the mask 2, a corresponding detector (a reflected electron detector, a light detector or an X-ray detector) is disposed instead of the secondary electron detector 7.
The charged particle optical system 8 is for generating charged particles and irradiating the mask 2 with the charged particles, and in the case of the SEM, it is for generating and finely focusing the electron beam and for subjecting the surface of the mask 2 to the plane scanning (scanning in the X- and Y-directions). In the case of the STEM, it is for generating the electron beam and irradiating the whole surface of the mask 2 with the electron beam.
The stage 9 is a rest on which the mask 2 is placed, and which is moved in the X- and Y-directions. Regarding the X-directional and Y-directional movement magnitudes of the mask 2 placed on the stage 9, the position of the mask 2 is measured at a high precision in real time by a laser interferometer or the like, not shown, and a personal computer (control portion) 11 controls the mask 2 to a predetermined position on the basis of measured positional information.
An image 10 is the image (so-called “secondary electron image”) or the like which has been obtained by subjecting the mask 2 to the plane scanning with the electron beam, detecting and amplifying the secondary electrons, and performing a brilliance modulation, and which is indicated on a display.
The personal computer (control portion) 11 is a control portion which controls the entirety of the apparatus shown in
Next, the operation of the configuration in
Referring to
“S2” conveys the mask 2 into the preliminary chamber 3. This takes out the mask 2 set in the mask magazine 1 at the S1, by a mechanism (robot) not shown and conveys the mask 2 to the illustrated position thereof in the preliminary chamber 3. In addition, if necessary, the interior of the preliminary chamber 3 is adjusted to a predetermined pressure within a range of from the atmospheric pressure to 0.1 Torr (or the interior of the preliminary chamber 3 is adjusted to a predetermined pressure with a predetermined gas (oxygen, nitrogen, an inert gas or the mixed gas thereof)).
“S3” performs X-ray irradiation. This irradiates the mask 2 conveyed into the preliminary chamber 3 at the S2, with the soft X-ray from the X-ray generator 4 (refer to
“S4” shifts the mask 2 into the subchamber 5. This shifts the mask 2 into the subchamber 5 in
“S5” performs a job in the main chamber 6. By way of example, the mask 2 is placed on the stage 9 of the main chamber 6, and in the state where the mask 2 is irradiated with the finely focused electron beam from the charged particle optical system 8, the mask 2 is subjected to the plane scanning with the electron beam. The secondary electrons thus emitted are detected and amplified by the secondary electron detector 7, and the image (secondary electron image) 10 is displayed. In addition, the measurement of the size of the predetermined pattern of the mask 2, or the like is performed on the image 10.
“S6” discriminates if irradiation with the X-ray is necessary. This judges charging in such a case where, during the job (during the measurement) at the S5, in a place which is currently under the measurement or a specified place which is periodically displayed, the color tone (the tone of white and black) of the image has changed more than a predetermined value, or the position of the image has changed more than a predetermined value, thereby to discriminate if the irradiation with the X-ray is necessary (if the removal (neutralization) of stored charges is necessary). In case of “YES”, the flow returns to the S3, at which the removal of the charges of the mask 2, etc. are performed by the X-ray irradiation, and the job is started at the S4 and S5 again (the job is restarted from the place of temporary stop, or it is started from a predetermined preceding place or from the beginning). On the other hand, in case of “NO” at the S6, the irradiation with the X-ray has been discriminated unnecessary, and hence, the mask 2 is taken out of the apparatus at “S7” (the mask 2 within the main chamber 6 in
In the above way, it is permitted to remove the charges by irradiating the mask 2 with the soft X-ray, before this mask 2 is placed on the stage 9 of the main chamber 6; to temporarily stop the job in the course of this job in which the mask 2 is placed on the stage 9, to remove the charges by irradiating the mask 2 with the soft X-ray, and to thereafter restart the job; or to remove the charges by irradiating the mask 2 with the soft X-ray after the end of the job.
Incidentally, although the irradiation of the mask 2 with the soft X-ray has been performed in the preliminary chamber 3, the charges may well be removed in such a way that the subchamber 5, and further the main chamber 6 are brought into an atmosphere of from the atmospheric pressure to about 0.1 Torr (an atmosphere of any of air, oxygen, nitrogen and an inert gas, or a combined gas consisting of at least two of them), and that the mask 2 is irradiated with the soft X-ray.
The above structure is bestowed on the illustrated reflection type X-ray generator 4 in the lamp form, whereby the soft X-ray can be easily generated and taken out so as to irradiate the whole surface of the mask 2 under the structure of
As described above, when the surface of the sample (mask) 2 or the vicinity thereof is irradiated with the soft X-ray emitted from the X-ray generator 4, both the positive ions and the negative ions are generated in the vicinity of the surface of the sample 2, and it is permitted to remove (neutralize) both the charges (positive charges and negative charges) of the sample 2.
On this occasion, as an atmosphere in the vicinity of the surface of the sample (mask) 2, in a state where any of the air, oxygen, nitrogen, an inert gas, etc., or a mixed gas consisting of at least two of them, has its pressure held within a range of from the atmospheric pressure to about 0.1 Torr, the sample 2 is irradiated with the soft X-ray, whereby the positive ions and the negative ions can be efficiently generated to remove (neutralize) the charges of the sample 2.
In a charged particle beam apparatus wherein a secondary electron beam or the like which is emitted from a sample by irradiating the sample with a charged particle beam is detected so as to generate an image, the present invention relates to a charged particle beam apparatus and a method for generating a charged particle beam image, in which the sample is irradiated with soft X-ray in a state where the surface or vicinity of the sample charged by an electron beam or the like is held in the atmosphere or a reduced pressure atmosphere or in a predetermined gaseous atmosphere within a preliminary evacuation chamber, a sample chamber or the like, whereby the charges of the surface of the sample are efficiently removed by heightening the generation efficiencies of positive ions and negative ions.
A description has been provided with particular reference to preferred embodiments thereof and examples, but it will be understood that variations and modifications can be effected within the spirit and scope of the claims which may include the phrase “at least one of A, B and C” as an alternative expression that means one or more of A, B and C may be used, contrary to the holding in Superguide v. DIRECTV, 358 F3d 870, 69 USPQ2d 1865 (Fed. Cir. 2004).
Filing Document | Filing Date | Country | Kind | 371c Date |
---|---|---|---|---|
PCT/JP2006/312061 | 6/15/2006 | WO | 00 | 7/23/2009 |