JP2002116531A - Method for producing mask - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem that a method for efficiently producing a mask is not provided in the case of a mask adaptable to an ultrafine pattern because size control by dose control is not attained in a combination of a high definition charged beam and a high contrast resist. SOLUTION: Exposure with a shifted position of a pattern for exposure is introduced in multiple exposure to form a level of dose for the pattern without affecting the accuracy of the position and to enable to conduct pattern size control in accordance with dose and the extent of pattern shift. Since the pattern size control is effective to a fine pattern and both dose and the extent of shift are used as size control parameters, exposure with sufficient tolerance is enabled. Since exposure which does not affect the finally obtained accuracy of the pattern position is enabled by adjusting the center of gravity in multiple exposure to zero by positive and negative mixed shifts, a mask is efficiently and accurately produced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an exposure method and a mask manufacturing method for exposing a fine pattern, particularly a semiconductor device pattern, onto a mask or a wafer using a charged beam.

[0002]

2. Description of the Related Art In a charged beam exposure used for pattern formation in a conventional mask manufacturing method, an exposure pattern is divided into deflection field regions and exposure is performed while moving a stage because a beam deflection range is limited.

In performing pattern multiple exposure,
A method is used in which the deflection field division position at the time of exposure is changed without changing the arrangement position of the pattern data in the mask substrate, and the exposure is performed so as to overlap the previous exposure. On the other hand, the pattern dimension adjustment is performed by changing the exposure amount, adjusting the development time, and changing the pattern data dimension.

[0004]

In charged beam exposure in the mask manufacturing process, in order to control the pattern size with high precision, the exposure amount and the development time are changed or adjusted, or the pattern data size is changed.・ It is necessary to adjust.

[0005] The former method is easy because the exposure amount can be adjusted at the time of exposure, but a combination of a beam with less blur and a high-contrast resist process is indispensable for ultra-fine exposure. Even if the development time is changed, the dimensional change becomes small, so that the dimensional adjustment becomes difficult. In particular, in the variable shaping exposure method, since the current density in one shot is uniform, it is not possible to form an irradiation amount distribution in a fine pattern. Therefore, it is possible to perform dimensional control by changing and adjusting the exposure amount and the development time. It is not possible, and the dimension adjustment requires a method of adjusting the pattern data dimension.

Although this method is not affected by the amount of beam blur and the resist process, it is possible to cope with ultra-fine patterns, but it takes time to change large-capacity pattern data such as a semiconductor memory. In addition, there is a problem that it takes more time to repeat this adjustment until the optimum change amount is determined.

SUMMARY OF THE INVENTION An object of the present invention is to provide a simple mask manufacturing method which achieves both high positional accuracy and high dimensional accuracy in charged beam exposure in a mask manufacturing process corresponding to an ultrafine pattern.

[0008]

In order to solve the above-mentioned problems, the pattern size is adjusted using multiple exposure. In this multiple exposure, since a pattern in which the pattern position on the mask substrate is changed is mixed in multiple times, an exposure amount distribution is generated in the finally obtained resist pattern according to the number of times of multiple times overlapping. For this reason, by changing the development time, the pattern size at the time of development varies depending on the amount of exposure.

Therefore, the pattern size can be adjusted with high precision by controlling the amount of movement of the pattern position during multiple exposure, the amount of exposure and the development time, and a desired pattern size can be obtained. In charged beam exposure, multiple exposure is indispensable in order to alleviate a connection error generated at a divided connection position due to pattern division and a positional accuracy error due to fluctuation of a charged beam irradiation position.

In the multiple exposure according to the present invention, by introducing an exposure in which the position of an exposure pattern is shifted, a dose level of the pattern is generated without affecting the positional accuracy, and pattern dimension control is performed by controlling the dose and the pattern. Control becomes possible by the shift amount. Since it is effective for a fine pattern and can be performed with both the irradiation amount and the shift amount as a dimension control parameter, a marginal exposure can be performed. Furthermore, by setting the center of gravity during multiple exposure to 0 with the shift amount of the positive / negative mixture, exposure that does not affect the finally obtained pattern position accuracy is possible.

Therefore, by applying the multiple exposure method according to the present invention, it becomes possible to manufacture a mask which can easily achieve both high positional accuracy and high dimensional accuracy.

As described above, according to the present invention, there is provided a method of manufacturing a mask including a step of performing a plurality of multiple exposures of a desired pattern on a sample by using a charged beam.
In at least one or more of the multiple exposures, a step of exposing the pattern to a position moved by a predetermined amount in a predetermined direction on the sample is included.

Further, according to the present invention, in the above-mentioned configuration, a step of exposing a pattern to a position shifted by the same amount in opposite directions on the sample in at least two or more of the multiple exposures is included. It is characterized by.

Further, according to the present invention, in the above structure, in at least one of the multiple exposures, the pattern is moved to a position where the pattern is moved by a fixed amount in a fixed direction on the sample in a different direction from the other exposures. And a step of exposing in an amount.

Further, according to the present invention, in the above configuration, in at least two or more of the multiple exposures, the pattern is exposed at the same amount of exposure to a position moved on the sample by the same amount in the opposite direction to each other. And a step of performing

Further, according to the present invention, in the above configuration, the method includes a step of dividing the multiple exposures such that the sum of the product of the movement vector amount and the exposure amount between the multiple exposure patterns becomes zero.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention are shown in FIGS.
5 will be described. The conventional method will be described with reference to FIG. 2 for comparison with the present invention.

Masks used for optical lithography and X-ray lithography are manufactured in steps shown in FIGS. In the photolithography mask shown in FIG. 4, a resist film (in this example, a positive resist) 19 is applied to a quartz substrate 18 on which a chromium (Cr) film 17 serving as a light-shielding portion is formed at the time of pattern transfer. Exposure of the resist film 19 to a desired pattern is performed by an exposure device.
9, a desired pattern opening is formed. Next, when the Cr film is etched, the Cr in the resist opening is etched, and a desired pattern is transferred to the Cr film. Finally, when the resist film is removed, a desired pattern opening 24 is formed.
Is completed.

Similarly, in the mask for X-ray lithography shown in FIG. 5, an absorber (T) serving as a light shielding portion at the time of pattern transfer is used.
a) A positive resist 23 is formed on a membrane mask substrate (Si) 22 in which a film 20 is formed on a membrane (SiC) film 21.
After applying the resist, a desired pattern exposure is performed on the resist film 23 by an electron beam exposure apparatus. When the resist film 23 is developed, the electron beam irradiating portion is dissolved to form a desired pattern opening in the resist film 23. Next, when the absorber film 20 is etched, the absorber in the resist opening is etched and a desired pattern is transferred to the absorber film. Finally, when the resist film is removed, a mask having a desired pattern opening 25 is completed.

When this mask is used in each lithography, the chromium opening 24 or the absorber opening 25
A desired pattern is transferred to the wafer by transmitting light or X-rays through the substrate. Therefore, the size of the transferred pattern is determined by the chrome opening 24 or the absorber opening 25.
Therefore, dimensional control of the chrome opening 24 or the absorber opening 25 is important.

In this regard, conventionally, in order to form an ultrafine pattern, it is necessary to use a resist having a charged beam with a small beam blur and a high-resolution and high-contrast developing characteristic for the pattern formation in FIGS. is there. When exposing the exposure pattern 1 shown in FIG. 2A onto a sample using a charged beam, if a rectangular beam with a small beam blur and a high-contrast resist are used, as shown in FIG. The energy stored in the resist at the time of exposure at AA ′ in a) has a steep energy profile 2 as shown by the solid line. When this is developed, the dissolution proceeds from the higher stored energy in accordance with the development time, so that the pattern dimension has a value that crosses the energy profile 2 at the slice level in FIG. 2B.

Therefore, as the development time increases, the slice level decreases from 3 to 4, and the pattern size at the time of development is determined by the value crossing at slice level 3 or 4 in FIG. With a steep energy profile as in this example, the pattern dimension hardly changes due to the control of the irradiation level and the development time, ie, up and down of the slice level. For this reason, there is a method of changing the original pattern size for adjustment to obtain a desired pattern size, but it is not practical because it takes several tens of hours or more to create a pattern for one size correction. Absent. In addition, there is a method in which a beam is exposed by blurring or a resist having low contrast is used. The energy profile in this case is as shown by the dotted line 5 in FIG. 2, and since the pattern size changes by controlling the development time or the rise and fall of the slice level, the adjustment for obtaining the desired pattern size is easy. However, in the case of a fine pattern, the energy distribution of the adjacent patterns overlaps with each other, and the pattern resolution becomes difficult at the slice level 4, so that the process margin cannot be obtained.

On the other hand, in the present invention, when exposing the exposure pattern 1 shown in FIG. 2A, the exposure is divided into multiple times as shown in FIG. 1A. First, in the first exposure, the conventional pattern position is exposed with an irradiation amount of 1/3 of the conventional exposure. Next, as the second exposure, the pattern position is set to +
The entire pattern is shifted by 1/3 of the pattern dimension in the X direction, and the exposure is performed at a dose of 1/3 of the conventional exposure. Further, as the third exposure, the entire pattern is shifted by １ ／ of the pattern size in the −X direction in the −X direction, and the exposure is performed with the irradiation amount of の of the conventional exposure.

FIG. 1B shows a profile 6 of the stored energy in the resist obtained by the exposure as described above. FIG. 1B shows the energy stored in the resist at the time of exposure at BB ′ in FIG. 1A. Since the pattern center on the sample is irradiated all three times, the sum is equal to the conventional irradiation amount. In the peripheral portion of the pattern, two multiplex portions, one exposure portion, and 3
There is a step dose level.

For this reason, it is possible to adjust the pattern size by controlling the slice levels 7 and 8 above and below, that is, by controlling the total irradiation amount and the development time, and to maintain the sharpness of the profile at the pattern end. Therefore, even a fine pattern can be handled. Also, the pattern position on the sample includes the exposure in the + X direction and the -X direction at the time of the multiple exposure. However, since the center of gravity of the multiple is zero, the accuracy of the formed pattern position is affected. Absent.

In the exposure of the present invention, as one specific example, an exposure apparatus shown in FIG. 3 was used. The electron beam 10 emitted from the electron gun 9 is converged by the lens 11 and shaped into a desired beam size by the deflector 13.
A desired position of the sample 15 is irradiated with the electron beam 10 by 4. In the present invention, in addition to the pattern data that determines the pattern type and its coordinates, which are the parameters of the conventional multiple exposure, and the dose data that determines which pattern is to be irradiated with the beam for how long, the pattern position newly corresponding to the multiple times is newly added. Since the parameter of the shift amount is added, the memory for storing the pattern data, the irradiation amount data, and the position shift data as the device exposure data is independently mounted, and at the time of the multiple exposure, each parameter is read from each memory according to the multiplexing times. I was able to call and perform the exposure efficiently.

In the above-described embodiment, the exposure dose in the multiple exposures is made uniform. However, by changing the exposure dose in each exposure or adding multiple exposures with a finer position shift amount, the exposure dose can be increased. Precise dimensional control is possible.

In the embodiment, an example of exposure using an electron beam has been described. However, the effect is the same for other charged beams. In the present embodiment, the shift amount is set in the X direction. However, it is possible to limit the dimensional control in a specific direction in this way. Dimensional control is possible at the same time even for patterns in the directions.

Further, as shown in the embodiment, if the sum of the products of the movement vector amount and the exposure amount between the multiple exposure patterns is set to be zero, the pattern position on the sample will not change, and Even if the sum of the products of the movement vector amount and the exposure amount between the multiple exposure patterns is set to a value other than 0, the pattern position on the sample can be adjusted.

[0030]

As described in detail above, according to the present invention,
In a mask pattern exposure step for fabricating a mask used for transferring a superfine pattern including a semiconductor, highly accurate dimensional control can be performed even in a fine pattern exposure using a high-definition charged beam and a high-contrast resist.

In the embodiment described above, optical lithography and
Although the manufacture of a mask for X-ray lithography has been described as an example, the present invention is similarly effective for the manufacture of masks for other lithography such as electron beam projection exposure and EUV (Extreme Ultra Violet) lithography. In addition, this method can be similarly applied to electron beam direct exposure in which pattern exposure is performed directly on a wafer without using a mask.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating an embodiment of the present invention.

FIG. 2 is a schematic view showing a conventional exposure method.

FIG. 3 is a diagram showing a specific example of an exposure apparatus according to the present invention.

FIG. 4 is a diagram showing an example of a cross-section of a mask structure for photolithography to which the present invention is applied and a mask manufacturing process.

FIG. 5 is a diagram showing an example of a cross-section of a mask structure for X-ray lithography to which the present invention is applied and a mask manufacturing process.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Exposure pattern, 2, 5, 6 ... Energy profile, 3, 4, 7, 8 ... Slice level, 9 ... Electron gun, 1
0: electron beam, 11: lens, 12: aperture, 13, 1
4: Deflector, 15: Sample, 16: Stage, 17: Cr
Film, 18 ... quartz substrate, 19, 23 ... resist film, 20 ...
Absorber (Ta) film, 21 ... membrane (SiC), 22
... silicon substrate, 24, 25 ... pattern openings.

Claims (5)

[Claims] 2. A method of manufacturing a mask, comprising the steps of: exposing a desired pattern on a sample in a plurality of times by using a charged beam; and exposing said pattern in at least one or more of said multiple exposures. Exposing the substrate to a position shifted by a predetermined amount in a predetermined direction on the sample. 2. The method according to claim 1, further comprising the step of exposing the pattern to a position shifted by the same amount in opposite directions on the sample in at least two or more of the multiple exposures. The method for manufacturing the mask according to the above. 3. A step of exposing the pattern to a position shifted by a predetermined amount in a predetermined direction on the sample in at least one or more of the multiple exposures with a different exposure amount from the other exposures. The method for manufacturing a mask according to claim 1, wherein: 4. The method according to claim 1, further comprising a step of exposing the pattern at the same amount of exposure to a position shifted by the same amount in the opposite direction on the sample in at least two or more of the multiple exposures. The method for manufacturing a mask according to claim 1, wherein 5. The method according to claim 1, further comprising the step of dividing the multiple exposure so that the sum of the product of the amount of movement vector and the amount of exposure between the multiple exposure patterns becomes zero.