JP4426730B2 - Mask black defect correction method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for correcting a black defect in a photomask or reticle.
[0002]
[Prior art]
The miniaturization of Si semiconductor integrated circuits is remarkable, and accordingly, the pattern dimensions on a photomask or reticle used for transfer are also becoming finer. In addition to miniaturization of pattern dimensions, super-resolution techniques such as phase shift masks are beginning to be put into practical use in order to improve the resolution limit of photolithography. If there is a defect on the photomask or reticle, the defect will be transferred to the wafer and cause a reduction in yield. Therefore, the defect inspection system will check if there is a defect on the photomask or reticle before transferring the mask pattern to the wafer. The location is examined, and if a defect exists, a defect correction process is performed by a defect correction device before transferring the defect onto the wafer. Due to the technical trend as described above, it is required to cope with small defects in the defect correction of the photomask or reticle. Focused ion beam devices using a liquid metal Ga ion source have become the mainstream of mask correction devices instead of defect correction devices using lasers due to their fine processing dimensions. The defect repair system using the above ion beam uses a sputtering effect by a focused ion beam or an effect of etching only where a narrow ion beam hits in the presence of an assist gas when correcting a black defect. Is realized.
[0003]
Conventionally used photomasks are made by depositing a binary mask material such as Cr or a halftone phase shift mask material such as MoSiON on a glass such as quartz glass by sputtering to form a light-shielding film. It is converted into the difference. Recently, Levenson-type phase shift masks that have been digged until glass is in antiphase, which has a stronger resolution and depth of focus improvement effect, have begun to be put into practical use. In order to reduce the riverbed when correcting black defects, an image as shown in JP-B-62-60699 is taken in to determine the irradiation area of the ion beam, and only black defect areas are selectively scanned when correcting black defects. Even if the method of correcting by the sputtering effect is used, the tail part of the ion beam or the ion beam scattered at a small angle hits the glass part around the defect. ) Always occurred. Since the river bed disturbs the phase of transmitted light due to the difference in height, it has an adverse effect on the transfer result and is a factor that degrades the processing quality of the black defect correction location. In particular, due to the recent shortening of the wavelength of the light source of a reduction projection exposure apparatus, even a river bed having a depth that does not cause a problem in the past has affected the transfer result. As described above, since the influence of the river bed is increasing, there is a strong demand for a defect correction technique that does not cause the river bed.
[0004]
Recently, as the defect size to be corrected decreases, a method of correcting defects with a hard probe of an atomic force microscope (AFM) has begun to be put into practical use. In this case, if the AFM probe is made to be the same height as the glass surface and the defect part is cut away, a river bed will not be produced, but in order to cut out all the defects, the scanning probe microscope cannot take a large scanning speed. Processing takes time and throughput cannot be increased. Further, unless a specially shaped probe is prepared for the processing site, the shape of the cross section is reflected to reflect the shape of the probe. When the edge is emphasized by using the phase shift effect as in the halftone mask or the Levenson mask, since any of the cross sections affects the phase, the desired effect cannot be obtained at the correction portion.
[0005]
[Problems to be solved by the invention]
The present invention intends to enable black defect correction without a river bed with practical throughput by combining a defect correction apparatus using an ion beam and an atomic force microscope (AFM).
[0006]
[Means for Solving the Problems]
In order to achieve black defect correction without a river bed, the ion beam tail component and the ion beam scattered at a small angle in the first stage are irradiated only to the inside of the defect area that is recognized not to hit the surrounding glass part. This is a two-step correction procedure in which etching is performed to leave the edge of the defect, and only the edge of the defect left in the second stage is physically cut with an AFM hard probe fixed at the height of the glass surface. Step on it to correct black defects.
[0007]
[Action]
In the first stage, the tail component of the ion beam and the ion beam scattered at a small angle are prevented from hitting the surrounding glass portion, so that a river bed due to these does not occur. Even in the second stage, the edge of the defect left with the AFM hard probe is fixed to the height of the glass surface and physically cut, so here again the glass part is not carved and there is no black defect in the river bed Correction can be realized. In addition, after roughly cutting with an ion beam, it is cut with AFM, so throughput can be improved compared to AFM alone. As described above, since the boundary with the normal pattern is formed by the first stage ion beam, no drooping reflecting the AFM probe shape occurs, and a steep sidewall can be obtained.
[0008]
【Example】
An embodiment of the present invention will be described below.
[0009]
A photomask or reticle containing a black defect is introduced into the vacuum chamber of an ion beam defect correction apparatus as shown in FIG. 1, and the black defect on the photomask or reticle 5 mounted on the XY stage 10 is emitted from the ion source 1. While the ion beam 2 focused by the condenser lens 3a and the objective lens 3b is scanned by the deflector 4, the secondary ion detector or the secondary electron detector 7 synchronously takes in the secondary ions or the secondary electrons 6. A secondary ion image or a secondary electron image is displayed, and a defective area is recognized from this image. At this time, in order to prevent charge-up, the photomask or reticle 5 is irradiated with the electron beam 8 of the electron gun 9 for charge neutralization. Only the region 17 retracted from the outer edge facing the defective glass as shown in Fig. 2 is processed so that the tail component of the ion beam irradiated to the surrounding underlying glass part and the ion beam scattered at a small angle do not hit. Then, only the black defect portion 17 is removed by irradiating the ion beam 2 so as not to damage the underlying glass portion 19 (FIG. 3). The removal is performed by physical sputtering or by using a speed-up effect of a halogen-based gas supplied from the tip of the gas gun 11 arranged in the vicinity of the processing region 17 from the gas reservoir 12. After the completion of processing, the photomask or reticle containing the black defect is taken out from the ion beam defect correcting apparatus.
[0010]
The extracted photomask or reticle 5 including the black defect is introduced into a processable AFM, and first, the region 17 including the part processed by the ion beam 2 is observed by the AFM, and only the outer edge 18 of the remaining black defect ( Fig. 4) is recognized as the machining area. In this case, since there is no information on the material only with the height information, the height of the glass surface 19 that is not exposed to the ion beam is set as a standard, and a portion higher than this is regarded as the normal pattern 16 or the defect portion 18. The defective part (processed area) is extracted by comparing with other normal patterns or design data. Only the part that is recognized as the processing area is controlled by height, and for example, it is physically scraped by scanning with the AFM probe 15 that is harder than the workpiece material (Cr, MoSiON, etc.) coated with diamond. Then, the remaining black defect portion is corrected (FIG. 5). If the lower limit of the height of the AFM probe 15 is set to the base glass surface 19, since the glass surface is not carved, it is possible to correct black defects without any river bed (FIG. 6). The black defect correction procedure without the river bed is summarized in Fig. 7.
[0011]
As a matter of course, the above method can be applied not only to binary masks and halftone masks but also to correction of black defects (residual defects) of a glass digging type Levenson mask. At this time, the edge of the black defect left by the correction of the mask defect correction apparatus using the ion beam is physically scraped to the same height as the glass surface dug so as to be in reverse phase, so that the peripheral glass river A modification without any bed can be realized.
[0012]
【The invention's effect】
As described above, according to the present invention, the tail component of the ion beam and the ion beam scattered at a small angle in the first stage are irradiated only to the inside of the black defect area where the glass part around the defect does not hit, Etching is performed to leave the edge of the defect, and only the edge of the black defect left in the second stage is physically scraped with the AFM hard probe fixed at the height of the glass surface, so there is no river bed Black defect correction can be realized. By performing a mix and match between the defect device and AFM using an ion beam, the throughput can be improved compared to the processing of AFM alone, and the boundary with the normal pattern can also be a steep side wall.
[Brief description of the drawings]
FIG. 1 is a conceptual diagram of a correction device using an ion beam.
FIG. 2 is a diagram showing a black defect region to be corrected by an ion beam correcting device.
FIG. 3 is a schematic cross-sectional view of a region including a black defect after correction by an ion beam correction apparatus.
FIG. 4 is a diagram showing a black defect region to be corrected by AFM.
FIG. 5 is a schematic cross-sectional view of a region including a black defect that is being corrected by an AFM that best illustrates the features of the present invention.
FIG. 6 is a schematic cross-sectional view of a region including a place where there is a black defect corrected by AFM.
FIG. 7 is a diagram showing a black defect correction procedure according to the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Ion source 2 Ion beam 3a Condenser lens 3b Objective lens 4 Deflection electrode 5 Photomask or reticle 6 Secondary ion or secondary electron 7 Secondary ion detector or secondary electron detector 8 Charge neutralizing electron beam 9 In charge Japanese electron gun 10 XY stage 11 Gas gun 12 Gas reservoir 15 AFM probe 16 Normal pattern 17 Black defect area 18 corrected by ion beam Black defect area 19 corrected by AFM Underlying glass substrate

Claims (2)

Etching to leave the edge of the black defect by irradiating only the inside of the defect area so that the ion beam does not hit the glass part around the black defect area with the mask defect repair device using ion beam, and leaving the defect Repair of black defects in the mask characterized by the fact that there is no correction of the glass bed in the peripheral part by physically cutting to the same height as the glass substrate with the hard tip of the atomic force microscope with the fixed edge Method. 2. A method for correcting a black defect in a mask according to claim 1, wherein an edge of the defect of the glass digging type Levenson mask left by the correction of the mask defect correction apparatus using an ion beam is dug so as to be in reverse phase. A method for correcting a black defect in a mask, characterized in that the correction is made without any glass bed in the periphery by physically cutting to the same height.

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