JP2002214760A - Method for correcting black defect of mask - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable the correction of black defect in which also the riverbed is not generated in the practical throughput by combining a defect correcting device using an ion beam and an atomic force microscope(AFM). SOLUTION: In order to realize the correction of black defect without the riverbed, the correction of black defect is performed by undergoing such two- step correcting procedure that, on the first step, only the inside of recognized defect region is irradiated in such a manner that a tail component of the ion beam and the ion beam subjected to small angle scattering do not strike the surrounding glass part, the etching is performed so as to leave a marginal part 18 of the defect and, on the second step, only the marginal part 18 of defect which is left is physically shaved by a hard probe 15 of AFM fixed on the height of glass surface 19.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for correcting a black defect on a photomask or a reticle.

[0002]

2. Description of the Related Art The miniaturization of Si semiconductor integrated circuits is remarkable, and the pattern size on a photomask or a reticle used for transfer is also becoming finer. In addition to the miniaturization of pattern dimensions, super-resolution techniques such as phase shift masks are being put into practical use to improve the resolution limit of optical lithography. Defects on the photomask or reticle are transferred to the wafer and cause a reduction in yield, so before transferring the mask pattern to the wafer, the presence or absence of defects on the photomask or reticle by the defect inspection device Location is checked,
If there is a defect, a defect correction process is performed by a defect correction device before transfer to the wafer. Due to the above technical trends, it is required to repair small defects in photomasks or reticles. Focused ion beam devices using liquid metal Ga ion sources have become the mainstream of mask repair devices instead of defect repair devices using lasers due to their fine processing dimensions. In the defect repair apparatus using the above-described ion beam, high processing accuracy is achieved by utilizing the sputtering effect of a focused ion beam or the effect of etching only where a narrowly focused ion beam hits in the presence of an assist gas when repairing a black defect. Has been realized.

Conventionally used photomasks include a binary mask material such as Cr or MoSi on a glass such as quartz glass.
A halftone phase shift mask material such as ON is deposited by sputtering to form a light shielding film, and the mask pattern is converted into a difference in light transmittance. Recently, Levenson-type phase shift masks in which glass is dug up to the opposite phase, which have stronger resolution and depth of focus effects, have begun to be put to practical use. In order to reduce the riverbed at the time of black defect correction, capture the image as shown in JP-B-62-60699 and decide the ion beam irradiation area,
At the time of repairing a black defect, even if a method of selectively scanning only the black defect area and repairing it by the sputtering effect is used, the tail component of the ion beam or the ion beam scattered at a small angle hits the glass portion around the defect. Therefore, digging of glass (river bed) was inevitably generated around the defect. Since the riverbed disturbs the phase of the transmitted light due to the difference in height, it adversely affects the transfer result, and is a factor that lowers the processing quality at the black defect correcting portion. In particular, due to the shortening of the wavelength of the light source of recent reduction projection exposure apparatuses, even a riverbed having a depth that is not a problem in the past has affected transfer results. As described above, since the influence of the riverbed is increasing, there is a strong demand for a defect repair technique that does not cause the riverbed.

Recently, as the size of a defect to be corrected has been reduced, a method of correcting a defect with a hard probe of an atomic force microscope (AFM) has started to be put to practical use. In this case, if the AFM probe is set at the same height as the glass surface to cut the defect site, no riverbed will occur, but in order to cut all the defects, the scanning probe microscope can not take a high scanning speed, Processing takes time and the throughput cannot be increased. Also, unless a specially shaped probe is prepared, the processed portion has a shape with a cross section that reflects the shape of the probe. When the edge is to be emphasized using the phase shift effect as in a halftone mask or a Levenson mask, the desired effect cannot be obtained at the corrected portion because the cross section affects the phase.

[0005]

SUMMARY OF THE INVENTION The present invention makes it possible to repair a black defect without a riverbed with a practical throughput by combining a defect repair device using an ion beam with an atomic force microscope (AFM). Is to try.

[0006]

In order to realize a black defect correction without a riverbed, the tail component of the ion beam and the ion beam scattered at a small angle in the first stage are recognized so as not to hit the surrounding glass part. Irradiation is performed only inside the defect area that has been etched, etching is performed to leave the edge of the defect, and only the edge of the defect left in the second stage is physically fixed with a hard probe of AFM fixed at the height of the glass surface. The black defect is corrected by performing a two-step correction procedure of sharpening.

[0007]

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 part, so that a riverbed does not occur. Also in the second stage, the edge of the defect left by the AFM hard probe is fixed at the height of the glass surface and physically shaved, so the glass part is not carved here, so there is no black bed at all Correction can be realized. In addition, since it is cut by AFM after being roughly cut by the ion beam, the throughput can be improved as compared with the processing of the AFM alone. As described above, since the boundary with the normal pattern is performed by the ion beam in the first stage, there is no danger of reflecting the shape of the AFM probe, and a steep side wall can be obtained.

[0008]

An embodiment of the present invention will be described below.

A photomask or reticle containing a black defect is introduced into a vacuum chamber of an ion beam defect correction apparatus as shown in FIG. 1, and a black defect on the photomask or reticle 5 mounted on the XY stage 10 is ionized. While the ion beam 2 emitted from 1 and focused by the condenser lens 3a and the objective lens 3b is scanned by the deflector 4, the secondary ion or secondary electron 6 is synchronized by the secondary ion detector or secondary electron detector 7. To display a captured secondary ion image or a secondary electron image, and recognize a defective area 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. In order to prevent the tail component of the ion beam irradiating the surrounding base glass part and the ion beam scattered at a small angle from hitting, only the area 17 recessed from the outer edge facing the defective glass as shown in Fig. 2 is the processing area 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). Removal is performed by physical sputtering or from the gas reservoir 12 to the processing area 17.
This is performed by using the speed-up effect of the halogen-based gas supplied from the tip of the gas gun 11 disposed in the vicinity. After the processing, the photomask or reticle containing the black defect is taken out of the ion beam defect correction device.

The photomask or reticle 5 containing the removed black defect is introduced into a workable AFM, and a region 17 including a portion processed by the ion beam 2 is first observed by the AFM. Only 18 (FIG. 4) is recognized as the processing area. In this case, there is no information on the material, only the height information.
Or, it is regarded as a defective portion 18. A defective portion (processed area) is extracted by comparing it with another normal pattern or design data. Only the part that is recognized as the processing area is controlled by height and scanned with an AFM probe 15 that is harder than the material to be processed (Cr or MoSiON, etc.), such as a diamond-coated probe, and physically cut off. Then, the remaining black defect is corrected (FIG. 5). If the lower limit of the height of the AFM probe 15 is set to the lower glass surface 19, the glass surface will not be carved,
Black defect correction without any riverbed can be realized.
6). FIG. 7 summarizes the above-described black defect repair procedure without a riverbed.

As a matter of course, the above method can be applied not only to the binary mask and the halftone mask but also to the black defect (residual defect) correction of the glass digging type Levenson mask. At this time, the edge of the black defect left by the repair of the mask defect repair device using an ion beam is physically ground to the same height as the glass surface dug so as to be in the opposite phase, and the river of the peripheral portion is removed. Modifications without any beds can be realized.

[0012]

As described above, according to the present invention, the tail component of the ion beam or the ion beam scattered at a small angle in the first stage is located inside the black defect region where the ion beam does not hit the glass part around the defect. Irradiate only the edge of the defect and perform etching to leave the edge of the defect, and only the edge of the black defect left in the second stage is physically shaved with a hard probe of AFM fixed at the height of the glass surface, Black defect correction without any riverbed can be realized. Defect device by ion beam and mix of AFM
By performing the & match, the throughput can be improved as compared with the processing using the AFM alone, and the boundary with the normal pattern can be made 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 illustrating a black defect area to be corrected by a correction device using an ion beam.

FIG. 3 is a schematic cross-sectional view of a region including a black defect after being repaired by a repair device using an ion beam.

FIG. 4 is a diagram showing a black defect area to be corrected by AFM.

FIG. 5 is a schematic cross-sectional view of a region including a black defect being repaired by 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 a black defect has been corrected by the AFM.

FIG. 7 is a diagram showing a black defect repairing procedure of 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 Electron beam for charge neutralization 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 to be corrected by ion beam 18 Black defect area to be corrected by AFM 19 Base glass substrate

Claims (2)

[Claims] 1. A mask defect repairing apparatus using an ion beam that irradiates only the inside of a defect region so that the ion beam does not hit a glass portion around the black defect region and performs etching to leave an edge of the black defect. The feature is that the edge of the remaining defect is physically shaved to the same height as the glass substrate with a hard probe of an atomic force microscope with a fixed height, so that there is no correction of the riverbed of the surrounding glass at all. A method for correcting black defects in masks. 2. The method of claim 1, wherein the edges of the defects of the glass digging type Levenson mask left by the repair of the mask defect repair apparatus using the ion beam are in opposite phases. A black defect repair method for a mask, characterized in that the glass bed in the peripheral portion is completely removed by physically shaving it to the same height as the dug glass surface. [0001]