JP2658231B2 - Photomask defect repair method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for correcting a defect of a photomask used when manufacturing an integrated circuit device or the like.

[Conventional technology]

Photomask defects include residual defects (black defects) and missing defects (white defects), and the occurrence of these defects causes a decrease in the yield of semiconductor devices such as LSIs. Since the repair of these defects greatly affects the productivity of the apparatus, it is necessary to reduce the number of steps required for the repair as much as possible to shorten the repair time.

For the correction of the black defect, a method of correcting the defect by laser irradiation (for example, Japanese Patent Publication No. 52-9505) has been used, and the process has been greatly shortened.

On the other hand, for correction of white defects, there is a method using a lift-off method, and this correction method includes a step of applying a positive photoresist on the entire surface of a photomask having a white defect, and a method of applying only a white defect portion using a spot exposure method. A step of performing exposure, a step of opening a window in the resist of a white defect portion by a development process, a step of forming a metal film on the white defect portion and the resist by vacuum deposition, and a step of removing the resist together with the metal film. Have. As described above, the correction method using the lift-off method requires a large number of steps, so that the steps cannot be shortened, and there is a problem in productivity.

Apart from such a repair method, there is a method of repairing a defect using a focused ion beam. FIG. 3 is a schematic view showing a conventional focused ion beam apparatus disclosed in, for example, JP-A-61-248346.

In FIG. 3, reference numeral 4 denotes a substrate made of quartz.
Above the ion source 11, an ion source 11 is provided.
Of the substrate 4 is focused by the lens 12, deflected by the deflecting plate 13, and collides with the surface 4a of the substrate 4. A low-energy electron gun is provided obliquely above the substrate 4.
An electron beam EB from the electron gun 14 is provided as a lens.
It is focused by 15 and deflected by the control electrode 16 and is poured onto a portion of the surface 4a surrounding the point focused on the ion beam IB surface 4a.

An ion detector 19 for detecting ions hit from the surface 4a is provided diagonally above the substrate 4, and the ion detector 19 outputs a detected signal to the system computer 26. Similarly, a grid is obliquely above the substrate 4.
An electron and ion detector 17 is provided which detects electrons and ions knocked out of surface 4a through grid 18 when 18 is properly biased to provide a signal through operational amplifier 20. The signal passing through the operational amplifier 20 is also applied to the system computer 26. The system computer 26 controls the bias control 21 and the relay 22 connected to the switch 23 to selectively apply the grid 18 to the ion-selection potential or the electron-selection potential provided on the corresponding designated terminal of the bias control 21. Connecting. The multiplexer control 24 provides a deflection signal for deflecting the control electrode 15 of the electron gun 14. The system computer 26 also provides a deflection signal that controls the amplifier 25 to operate the deflection plate 13.

Further, a gas nozzle 8 is provided above the substrate 4 with its nozzle direction facing the substrate 4.
Is connected to a gas cylinder 27 containing a hydrocarbon gas.

Next, the operation will be described with reference to FIG. 4, which shows the relationship between ion beams, electrons, and the like. The ion beam IB generated from the ion source 11 is accelerated and focused by the lens 12. Then, the deflection plate 13 accurately positions the ion beam IB within a region of 1 mm ² on the surface 4a, and the ion beam IB collides with this region. When the ion beam IB collides with the surface 4a of the substrate 4, a number of phenomena occur as shown in FIG.
In other words, generation of low energy secondary electrons (Fig. 4a)
Positive and negative low energy secondary ion generation (Fig. 4b
And c) Atomic ejection from surface 4a (FIG. 4d)
Phenomena such as implantation of primary ions from the ion beam IB into the surface 4a (FIG. 4e) occur. And the ion beam
Accurate positioning in the area where the IB collides with the surface 4a is important.

Next, a conventional photomask defect repairing method using the focused ion beam apparatus having the above-described configuration will be described with reference to FIG. 2 showing the repairing process. FIG. 2A is a plan view of a photomask having a defect, and FIG. 2B and FIG. 2B are cross-sectional views taken along the line AB in FIG. c). In FIG. 2A, reference numeral 1 denotes a mask pattern of a photomask made of a light-shielding material 5 formed on the surface of a substrate 4, and includes a black spot 2a and a projection 2b.
, And a white defect 3 composed of pinholes 3a and 3b.

First, the substrate 4 on which such a photomask is formed is put into the above-mentioned focused ion beam apparatus, and the area where the black defect 2 (the black spot 2a and the projection 2b) is present is irradiated with the ion beam IB while being scanned. The black defect 2 is corrected by scratching by sputtering (FIG. 2 (b)).
Next, after confirming the region where the white defect 3 exists, the ion beam IB is scanned while flowing the hydrocarbon gas stored in the gas cylinder 27 from the gas nozzle 8 into this region, and a carbonized film is laminated on this region to form a white film. The defect 3 is corrected (FIG. 2 (c)).

[Problems to be solved by the invention]

If the substrate 4 is not a conductor, the incident ionic charges accumulate under the beam to form an unfocused electric field. This unfocused electric field not only interferes with the formation of the ion beam at the surface 4a, but also as the ions and electrons leave the surface.
Disrupt their orbit. Therefore, there is a problem that charge-up due to ionic charges is inevitable.

Therefore, the surface including the collision point of the ion beam IB is
To neutralize the positive charge of the irradiated ions by the replenishment of electrons from to reduce the unfocused electric field,
There was a problem that it was not perfect.

The present invention has been made in view of such circumstances, and can prevent charge-up due to ionic charges to be irradiated, and can easily correct even a defect requiring strict positional accuracy, and furthermore, can improve the defect. It is an object of the present invention to provide a method for repairing a defect of a photomask which does not damage a substrate at the time of repair.

[Means for solving the problem]

According to the defect repair method for a photomask according to the present invention, first, a conductive metal thin film having a material different from that of the photomask to be repaired is laminated on the photomask, and a residual defect (black defect) is irradiated by a charged beam. And removing the defects by irradiating a charged beam while feeding a reaction gas to form a carbon film on the missing defects (white defects).

[Action]

In the method for correcting a defect of a photomask according to the present invention, a conductive metal thin film made of a material different from that of the photomask is formed on the photomask to be corrected. Therefore, the photomask is not damaged at all when the charged beam is irradiated. In addition, the substrate surface can be easily grounded to the ground so that charge-up due to ionic charges can be prevented.

〔Example〕

Hereinafter, the present invention will be described in detail with reference to the drawings showing the embodiments.

FIG. 1 is a schematic view showing the steps of a method for correcting a defect of a photomask according to the present invention. In FIG. 1 (a), reference numeral 1 denotes molybdenum silicide (MoSi ₂ ) formed on the surface of a substrate 4.
2a and 2b are black spots and projections of a black defect (residual defect) 2, and 3a and 3b are pinholes and white holes of a white defect (missing defect) 3, respectively. I am. FIGS. 1 (b) to 1 (e)
Is a plan view in the repairing process or A- in FIG.
FIG. 3 shows a cross-sectional view taken along line B.

First, a chromium (Cr) film 9 as a conductive metal thin film is formed on a photomask to a thickness of about 100 ° by vapor deposition or sputter deposition (FIG. 1B). Next, the substrate 4 on which the photomask is formed is put into a focused ion beam device. In this case, it is not necessary to provide an electron gun for supplying electrons for neutralizing the ion beam in the focused ion beam device. In the example of the present invention, the chromium film 9 is grounded to the ground via the ground line 6, and electrons for neutralizing the ion beam are supplied from the ground line 6. While scanning the focused ion beam IB, the region where the black defect 2 exists is irradiated, and the defect portion is scratched by sputtering to correct the black defect 2 (first example).
Figure (c). In this step, the positive charges in the ion beam IB are easily neutralized by electrons supplied from the surrounding chrome film 9 via the ground line 6, so that charge-up can be prevented.

Next, while flowing a small amount of hydrocarbon gas from the gas nozzle 8, the ion beam IB is scanned to irradiate the ion beam IB to a region where the white defect 3 exists, and the carbonized film 7 is laminated. Correct (FIG. 1 (d)). At this time, since the chromium film 9 has a thickness of about 100 °, a chromium carbide layer is formed by mixing accompanying irradiation of the ion beam IB, and the carbon film 7 is laminated on the surface of the white defect region. Also in this process,
Since the positive charge of the ion beam IB is neutralized by the electrons from the ground line 6, charge-up due to the ionic charge can be prevented.

The substrate 4 on which the defect correction has been completed is taken out of the focused ion beam apparatus, and the chromium film 9 is removed by etching over the entire surface (FIG. 1E). As an etching method at this time, plasma etching is performed using ceric ammonium nitrate and perchloric acid in the wet method, and plasma etching using a mixed gas of carbon tetrachloride (CCl ₄ ) and oxygen (O ₂ ) in the dry method. Do.
Under such conditions, only the chromium film 9 is selectively etched and the molybdenum silicide film 5 is hardly etched, so that the photomask is hardly damaged.

In this embodiment, when the black defect is corrected, the focused ion beam is irradiated. However, the present invention is not limited to this, and a laser beam may be irradiated to a region where the black defect exists to correct the black defect. . In such a case, after the black defect is removed by irradiating a laser beam, a conductive metal thin film is laminated and formed on a photomask, and the conductive metal thin film is connected to the ground line as in the above-described embodiment. Then, the white defect may be corrected by irradiating an ion beam while supplying a hydrocarbon gas to the ground via the ground.

〔The invention's effect〕

As described above in detail, in the present invention, it is possible to prevent the generation of an unfocused electric field generated when irradiating a focused ion beam, and to prevent charge-up due to the focused ion beam. As a result, it is possible to specify the correction position with high accuracy. Further, in the ion beam apparatus for carrying out the present invention, the present invention has excellent effects such that an electron gun for supplying an electron beam is not required as compared with the prior art.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing the steps of a photomask defect repair method according to the present invention, FIG. 2 is a schematic diagram showing the steps of a conventional photomask defect repair method, and FIG. 3 shows the configuration of a focused ion beam apparatus. FIG. 4 is a schematic view showing an etching process. 1 mask pattern 2 black defect 2a black spot 2b protrusion 3 white defect 3a pinhole 3b crack 4 substrate 6 ground Line, 7 ... carbonized film, 9 ... chromium film, IB ... ion beam In the drawings, the same reference numerals indicate the same or corresponding parts.

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-55-84938 (JP, A) JP-A-60-98625 (JP, A) JP-A-63-141060 (JP, A) JP-A 54-84 32978 (JP, A) JP-A-57-18325 (JP, A)

Claims (2)

(57) [Claims] 1. A method for correcting a residual defect or a missing defect generated in a photomask, comprising: forming a conductive metal thin film made of a material different from that of the photomask on the photomask; Irradiating a charged beam on a portion to be removed to remove the residual defect; irradiating the charged beam while supplying a reactive gas to a portion where the missing defect exists to form a carbonized film; Removing the metal thin film by etching. 2. A method for correcting a residual defect or a missing defect generated in a photomask, the method comprising: irradiating a laser beam to a portion where the residual defect exists to remove the residual defect; Forming a conductive metal thin film made of a material on the photomask; forming a carbonized film by irradiating a charged beam while supplying a reactive gas to a portion where the missing defect exists; Removing the metal thin film by etching.