JP3243822B2 - Mask inspection method and reticle mask - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mask inspection method and a reticle mask. In recent years, DRAMs and the like, which are at the forefront of high density, require high density reticle mask patterns. Therefore, it is necessary to improve the surface quality of the reticle mask.

Since the most advanced DRAM and the like use a design rule near the resolution of a stepper as a minimum pattern size, a pattern which cannot be resolved due to a defect which has not been a problem in the past may be impossible.
Automatic mask surface inspection systems have been moving toward improving the defect detection sensitivity.

However, pattern inspection using light (for example, using a mercury lamp) is reaching its resolution limit. Inspection devices with high resolution, such as electron beam inspection devices that use electrons instead of light, have become necessary, but inspection devices that use light are still the mainstream.

[0004]

2. Description of the Related Art Conventionally, an automatic surface inspection method using light has been widely adopted. FIG. 3 is a schematic view showing a conventional example, wherein 1 is a transparent substrate, 2 is a mask pattern, 11 is a substrate holder, 12
Represents a lamp, 13 and 14 are lenses, 15 is a light receiving section, 16 is an image processing section, 17 is an inspection data storage section, 18 is a combining section, and 19 is a detecting section.

[0005] The transparent substrate 1 is, for example, a glass substrate, the mask pattern 2 is, for example, a Cr pattern, and the glass substrate 1 and the Cr pattern 2 constitute a reticle mask.
Mount a reticle mask on the substrate holder 11
Perform optical scanning on the reticle mask while moving on the Y stage. The optical signal received by the light receiving unit 15 is converted into an electric signal and sent to the image processing unit 16. The inspection data storage unit 17 stores design pattern data of the reticle mask in advance. The data from the image processing unit 16 and the data from the inspection data storage unit 17 are combined by the combining unit 18, and the image processing unit 16
The difference between the data from the data and the data from the test data storage unit 17 is sent to the detection unit 19. The data difference corresponds to the missing or remaining mask pattern.

[0006] As an automatic surface inspection method using light, Die to Die comparison inspection is also widely used. In this method, the same pattern is formed on the left and right or before and after the block, and the white pattern (light transmitting area) and the black pattern (light shielding area) of the patterns of the left and right blocks or the patterns of the preceding and following blocks are compared. Then, the difference is determined in an analog manner or the areas are compared. Also, vectors perpendicular to the edges of the pattern are set at predetermined intervals, and the number of vectors projected in the X direction and the number of vectors projected in the Y direction perpendicular thereto are determined by the pattern of the left and right blocks or the pattern of the preceding and following blocks. The comparison is also performed.

However, these methods have a limitation in the resolving power depending on the wavelength of light used. For example, when a mercury lamp is used, it is difficult to resolve a pattern of 0.2 μm or less.
Further, this method recognizes a pattern as a white pattern (light transmitting area) and a black pattern (light shielding area), and cannot distinguish the type of the substance.

FIGS. 2A to 2D are schematic views showing defects of the reticle mask, FIG. 2A is a plan view, and FIGS. 2B to 2D are AA sectional views. In the figure, 1 is a transparent substrate, 2 is a Cr pattern,
2a is a light shield, 21 is an attached matter, and 22 is a pattern remaining.
The attachment 21 is, for example, organic dirt or dust.

In the conventional method, the deposit 21 also has a pattern remaining 22
Both are recognized as light-shielded areas, and cannot be distinguished from substances. Furthermore, it cannot be determined whether there is a pattern remaining under the deposit 21. Therefore, it is necessary to confirm what such a defect becomes a light shielding area after the inspection.

For example, the brightness of the area is observed by an optical microscope, and it is determined whether the pattern is remaining or a foreign substance other than the pattern. In addition, foreign substances such as organic dirt and dust are removed by washing.

However, even with this method, it cannot be determined whether or not there is a pattern remaining under the foreign matter, so that sufficient correction may not be performed.

[0012]

Therefore, in the conventional method, the detection accuracy of a fine pattern is limited due to the limitation of resolution due to the wavelength of light, and it is not possible to completely confirm a substance which is a defect in a light transmission region. There was such a problem.

The present invention has been made in view of the above problems, and provides a mask inspection method capable of improving the detection accuracy of a fine pattern and further directly determining whether a defect in a light transmitting region is a remaining pattern or other defects. The purpose is to do.

[0014]

FIG. 1 is a schematic diagram showing an embodiment. The above object is a method of inspecting a mask in which a mask pattern 2 is formed on a transparent substrate 1 with a mask material, and the mask is scanned while irradiating the primary surface with primary ions 4.
The secondary ions 6 emitted from the mask surface are analyzed by a mass spectrometer.
When the secondary ions 6 from the region to be transparent include neither the main component of the transparent substrate 1 nor the main component of the mask material, foreign matter other than the mask material is included in the region to be transparent. Is determined to be attached, and a predetermined step of removing the foreign matter is performed based on the determination, and the problem is solved by a mask inspection method.

The present invention also relates to a method of inspecting a mask in which a mask pattern 2 is formed on a transparent substrate 1 using a mask material. The ions 6 are analyzed by a mass spectrometer, and the secondary ions 6 from the region to be transparent are
When neither the main component of the transparent substrate 1 nor the main component of the mask material is included, it is determined that foreign matter other than the mask material is attached to the area to be transparent, and based on this, the primary ions 4 are sequentially determined.
The removal of the foreign matter by the irradiation of light and the analysis of the secondary ions emitted from the base of the foreign matter are performed. When the secondary ions include the main component of the mask material, the mask material remains under the foreign matter. Is determined, and a predetermined step of removing the remaining mask material is performed based on the determination.

The present invention also relates to a method for inspecting a mask in which a mask pattern 2 is formed on a transparent substrate 1 with a mask material, wherein the mask surface is optically inspected, and a light shield 2a is provided in an area to be transparent. At this time, it is determined whether the light shield 2a is a mask material residue or other foreign matter. When it is determined that the foreign matter is a foreign matter, the foreign matter is removed by irradiation with the primary ions 4 and the removed foreign matter is removed. Secondary ions emitted from the base of the foreign matter are analyzed by the mass spectrometer , and when the secondary ions include the main component of the mask material, it is determined that there is a mask material residue under the foreign matter, and based on this, The above problem is solved by a mask inspection method in which a predetermined step of removing the remaining mask material is performed.

Further, the problem is solved by the reticle mask inspected by the above-described mask inspection method.

[0018]

According to the present invention, the mask surface is scanned while being irradiated with the primary ions 4. Since the ion beam can be narrowed down to, for example, about 0.1 μm, a fine pattern can be detected more accurately than when light is used.

Since the secondary ions 6 emitted from the mask surface are analyzed, if the secondary ions 6 from the region to be transparent include neither the main component of the transparent substrate 1 nor the main component of the mask material, It can be determined that foreign matter other than the mask material is attached to the area to be transparent.

The analysis of the secondary ions 6 can be easily performed by using the mass analyzer 5. Further, after it is determined that foreign matter other than the mask material is attached to the area to be transparent, the foreign matter is removed by irradiating the primary ions 4 and secondary ions emitted from the base of the foreign matter are analyzed. Therefore, it can be determined whether or not the mask material remains on the base.

Further, by optically inspecting the mask surface, when the light shield 2a is located in an area to be transparent, it is determined whether the light shield 2a is a mask material residue or other foreign matter. If it is a foreign matter, the foreign matter is irradiated with the primary ions 4 to remove the foreign matter, and the secondary ions emitted from the base of the foreign matter are analyzed. Therefore, it is determined whether or not the mask material remains on the base. can do.

If a reticle mask inspected by the above-described mask inspection method is used, all the remaining portions of the mask material are known, so that they are completely removed.
A reticle mask having no remaining mask material can be formed.

[0023]

FIG. 1 is a schematic view showing an embodiment, in which 1 is a transparent substrate, 2 is a mask pattern, 3 is an ion gun, 4 is a primary ion, 5 is a mass analyzer, 5a is a magnet, and 5b is Cr detection. Department,
Reference numeral 5c denotes a Si detector, 6 denotes a secondary ion, 7 denotes an XY stage, 8 denotes a vacuum chamber, and 8a denotes an exhaust port.

The transparent substrate 1 is, for example, a 5-inch square glass substrate, on which a mask pattern 2 of a pattern to be projected and exposed at a reduction ratio of, for example, 5: 1 is formed.
The mask pattern 2 is formed by patterning a deposited Cr film, for example. Glass substrate 1 and mask pattern 2
Becomes a reticle mask.

This reticle mask is mounted on an XY stage 7 in a vacuum chamber 8. Ga ion beam 4 whose beam diameter is reduced to, for example, 0.1 μm from the ion gun 3
Is irradiated on the reticle mask surface as primary ions.
The Ga ion beam 4 is scanned to cover, for example, a 5 mm square area. The surface of the reticle mask is slightly shaved by irradiation with primary ions, and secondary ions are emitted.

If the surface irradiated with the primary ions is a Cr pattern, Cr is released, and if the surface is a glass substrate, Si is released, and the Si enters the mass analyzer 5. Secondary ions are magnets
5a, the track is bent according to the mass, Cr
If it is, it is detected separately by the Cr detection unit 5b, and if it is Si, it is detected by the Si detection unit 5c.

FIGS. 2A to 2D are schematic diagrams showing defects of the reticle mask, and will be described below with reference to these drawings. The Cr pattern 2 is a designed pattern, and there is no defect if the secondary ions Cr incident on the mass analyzer 5 completely correspond to the pattern. However, as shown in FIG. 2 (a), when the light shield 2a is located in a region where the glass substrate 1 is to be exposed, Si as the main component of the glass substrate 1 is not detected in the secondary ions from that region. It is clear that there is some defect.

If there is a deposit 21 as shown in FIG. 2 (b) and it is, for example, a contaminant of an organic solvent, neither Cr nor Si is detected in the secondary ions from that region, It is presumed that something other than the remaining pattern is attached. Therefore, the deposits 21 are removed by irradiating them with primary ions, exposing the base, and releasing secondary ions from the base.

If the secondary ions from the base include Si, the foreign matter directly adheres to the glass substrate 1 (FIG. 2B).
See). If the secondary ions include Cr, it can be seen that there is a Cr pattern residue 22 under the deposit 21 (FIG. 2 (d)).
See).

If the secondary ions from the light shield 2a are Cr
As a result, it is immediately understood that there is a Cr pattern residue 22 on the glass substrate 1 (see FIG. 2C). Since the scanning of the Ga ion beam 4 cannot be performed over a large area at one time, for example, after covering an area of 5 mm square, the reticle mask is moved 5 mm back and forth or left and right by the XY stage. Inspection, and continues the inspection over the entire reticle mask.

In this manner, all foreign substances such as the organic solvent in the region to be transparent are removed, and only the remaining Cr pattern is exposed. Thereafter, the Cr pattern residue is scattered and removed by, for example, laser irradiation, and is corrected. In this way, all the light shields in the areas that should be transparent are removed and the rest of the pattern is obtained with a modified reticle mask.

Further, a light shield 2a is provided in an area to be transparent.
When there is, first determine whether it is a pattern remaining or other foreign matter using an optical microscope as in the past, and then irradiate the foreign matter with primary ions as shown in Fig. 1 to remove it. Then, the base is exposed to release secondary ions from the base. If the secondary ions from the base include Cr, it is understood that there is a Cr pattern residue 22 in the base, and if the secondary ions include Si, it is understood that there is no Cr pattern residue in the base.

[0033]

As described above, according to the present invention,
0.1 μm by using ion beam instead of light
It is possible to detect a fine pattern or a defect of about m.

Further, since it is possible to make a distinction between the remaining pattern and the attached matter, it is possible to reduce the time required to confirm the type of defect. In addition, it can be determined whether there is a pattern remaining under the attached matter.

Further, in the resist mask inspected in this way, since the remaining pattern in the region to be transparent can be known without fail, it can be completely corrected.

Such a mask inspection method and reticle mask can be effectively applied not only to the manufacture of semiconductor devices but also to the manufacture of electronic devices such as liquid crystal panels. Alternatively, a defect is detected, the reticle mask inspection time is shortened, and the pattern remaining is completely corrected.

[Brief description of the drawings]

FIG. 1 is a schematic view showing an embodiment.

FIGS. 2A to 2D are schematic diagrams showing defects of a reticle mask.

FIG. 3 is a schematic diagram showing a conventional example.

[Explanation of symbols]

 1 is a transparent substrate, a glass substrate 2 is a mask pattern, a Cr pattern 2a is a light shield 3 is an ion gun 4 is a primary ion and Ga ions 5 is a mass analyzer 5a is a magnet 5b is a Cr detector 5c Is a Si detector 6 is a secondary ion 7 is an XY stage 8 is a vacuum chamber 8a is an exhaust port 11 is a substrate holder 12 is a lamp 13, 14 is a lens 15 is a light receiving section 16 is an image processing section 17 is an inspection data storage. Section 18 is the synthesis section 19 is the detection section 21 is the deposit 22 is the pattern remaining

Claims (3)

(57) [Claims] 1. A method for inspecting a mask in which a mask pattern is formed on a transparent substrate by a mask material, wherein the mask surface is scanned while being irradiated with primary ions, and the secondary ions emitted from the mask surface are mass- scanned. Analyzed by the analyzer, when the secondary ions from the region to be transparent do not include the main component of the transparent substrate or the main component of the mask material, the secondary ion is A method for inspecting a mask, comprising determining that foreign matter other than a mask material is attached, and performing a predetermined step of removing the foreign matter based on the determination. 2. A mask putter on a transparent substrate using a mask material.
This is a method of inspecting a mask having a mask formed thereon, wherein the mask surface is scanned while being irradiated with primary ions , and the mask is scanned.
Secondary ions released from the surface of the
And secondary ions from the area that should be transparent
When neither the main component of the bright substrate nor the main component of the mask material is contained,
Foreign matter other than the mask material adheres to the area that should be transparent
And irradiates the primary ion sequentially based on this.
Removal of the foreign matter and release from the base of the foreign matter 2
The secondary ions are analyzed and the secondary ions are
When the main component is included, it is determined that there is a mask material residue under the foreign matter.
Cut off, and based on this, further remove the remaining mask material
A method for inspecting a mask, wherein a step is performed. 3. A method for inspecting a mask in which a mask pattern is formed on a transparent substrate by a mask material, wherein the mask surface is optically inspected to determine a region to be transparent.
When there is a light shield, the light shield is the mask material residue
Judgment as to whether the object is a foreign object
The foreign matter is removed by irradiation with primary ions.
Secondary ions released from the substrate of the removed foreign matter are mass
The secondary ions are analyzed by an analyzer, and the
Judge that mask material remains under the foreign material
On the basis of this, a predetermined removal process of the mask material residue is performed.
A mask inspection method characterized by being performed.