JP2002110519A - Stress adjusting method for exposure mask, stress adjusting device, manufacturing method of exposure mask including this stress adjusting method in process, and semiconductor device pattern-transferred using this exposure mask - Google Patents

Abstract

(57) [PROBLEMS] To provide an exposure mask which adjusts the pattern film stress of a fine pattern exposure mask and has no pattern displacement. Further, the present invention provides a semiconductor device on which pattern transfer with high accuracy is performed. SOLUTION: An exposure mask 18 is immersed in a solution tank 1 filled with a solution 2, and further provided with a reference electrode 7 and a counter electrode 8, and the exposure mask and the counter electrode are connected via a power supply 9. I do. The state of the constituent material of the pattern film on the exposure mask in the aqueous solution is determined from the relationship between the potential and the pH, and the potential of the pattern film on the exposure mask relative to the reference electrode is controlled to a desired potential to reduce or oxidize A reaction is caused to adjust the pattern film stress. The pH may be adjusted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stress adjusting method and a stress adjusting apparatus for mitigating pattern distortion of an exposure mask for transferring a fine pattern. In addition, the present invention relates to a method for manufacturing an exposure mask including the stress adjustment method in a manufacturing process, and a semiconductor device manufactured using the exposure mask.

[0002]

2. Description of the Related Art In recent years, miniaturization and densification of semiconductor device patterns have been promoted, and a technique for transferring a finer circuit pattern onto a substrate for manufacturing a semiconductor device has been required. For this reason, the wavelength of light used for exposure has been actively reduced, and an exposure method using an X-ray or an electron beam capable of transferring an extremely fine pattern has been developed.

A method of manufacturing an exposure mask used for transferring such a circuit pattern is disclosed, for example, in Japanese Patent Application Laid-Open No. H11-27067 filed by the present applicant. Hereinafter, a method of manufacturing an X-ray mask disclosed in this publication will be described as a conventional example.

FIG. 5 is a schematic cross-sectional view showing an example of steps of a conventional method for manufacturing an X-ray mask disclosed in the above publication. First, a membrane (synonymous with an X-ray transparent substrate) is placed on the substrate 11.
12 is formed (FIG. 5A). Next, the membrane 12
A part of the substrate 11 is removed until a part of the back surface is exposed (FIG. 5B). Then, a base film 13 serving as an antireflection film and an etching stopper film is formed on the membrane 12 and baked (FIG. 5C). Further, an absorber 14 made of a material that blocks transmission of X-rays is formed on the base film 13, and the average film stress of the absorber 14 is measured. For example, 250 ° C
Annealing is performed to the extent shown in FIG. 5 (d). Then, after applying a resist 15 on the absorber 14 and baking, a support ring 16 is attached to the back surface of the substrate 11 with an adhesive 17.
(FIG. 5 (e)). Then, the absorber 14 is etched using the patterned resist 15 as a mask, and thereafter, the resist 15 is removed.
The exposure mask 18 shown in FIG.

The membrane 12 is made of, for example, silicon carbide (SiC) or a diamond thin film that transmits X-rays. The absorber 14 is made of tungsten (W), a W compound, tantalum (Ta), a Ta compound, or the like. A conductive metal film is generally used. As the base film 13, indium tin oxide (ITO), ruthenium (Ru), or the like is used. The base film 13 is not always necessary, and the absorber 14 may be formed directly on the membrane 12 in some cases.

According to such a manufacturing method, it has become possible to provide an exposure mask on which an extremely fine pattern is formed. Also, by performing annealing before patterning the absorber 14, the average film stress of the absorber 14 is adjusted so as to be zero, and measures have been taken to prevent pattern displacement due to residual stress.

Further, if the generated film stress is equal in the vertical direction and the horizontal direction of the pattern, that is, isotropic distortion, attempts have been made to transfer the film by mechanically correcting the distortion during exposure. .

[0008]

However, even if the average film stress of the absorber 14 is set to 0 before patterning, a compressive stress is generated due to the formation of a natural oxide film on the side wall of the absorber 14 after patterning. There has been a problem that pattern displacement occurs.

Further, especially when there are many pattern defects,
For example, when the correction is performed by a laser or the like, there is a problem that the stress is partially changed and the stress value is changed, thereby causing a pattern displacement.

[0010] In addition, in the step after the membrane is mounted on the substrate with an adhesive, there is a problem that the conventional distortion adjustment method by annealing cannot be used.

In addition, if the generated film stress is a so-called anisotropic distortion that is different in the vertical and horizontal directions of the pattern, there is no means for correcting it at the exposure stage (the normal pattern film has a vertical direction and a horizontal direction). The size in the lateral direction is different, and when oxidized, the film strain in the longitudinal direction increases, resulting in anisotropic strain).

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and it is an object of the present invention to provide a method for adjusting the stress of a finely formed pattern film and an apparatus for realizing the method. Further, the present invention provides a method for manufacturing an exposure mask having a fine absorber pattern without the above-described positional shift, and provides a semiconductor device in which a high-precision fine pattern is formed using the manufactured exposure mask. It is.

[0013]

According to a first aspect of the present invention, there is provided a method for adjusting a stress of an exposure mask including a substrate, a membrane, and a pattern film formed on the membrane. In the method, a predetermined potential is applied to a solution having a predetermined pH to reduce or oxidize the pattern film.

According to a first aspect of the present invention, there is provided a stress adjusting apparatus for an exposure mask, comprising a substrate, a membrane, and a pattern film formed on the membrane. One electrode, a second electrode opposed to the first electrode, and a power supply for supplying a current to the first electrode are provided.

An exposure mask stress adjusting apparatus according to a second aspect of the present invention includes means for measuring a stress distortion of a pattern film, and refers to a value measured by the measuring means. And a control circuit for controlling the potential of the first electrode of the stress adjusting device for an exposure mask.

A first method of manufacturing a mask for exposure according to the present invention comprises a step of forming a membrane on a substrate, a step of removing a part of the substrate, and a material for blocking exposure light on the membrane. A step of forming a film, a step of patterning a film made of a material that blocks the exposure light, and a step of applying a predetermined potential in a solution having a predetermined pH to reduce or oxidize the patterned film. Things.

According to the present invention, there is provided a semiconductor device to which a pattern is transferred by using the first exposure mask, wherein the stress is adjusted by the first exposure mask stress adjustment method, or the first exposure mask is subjected to the stress adjustment. The pattern is transferred using an exposure mask manufactured by using the method for manufacturing an exposure mask described above.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing a schematic configuration of a stress adjusting device for an exposure mask according to a first embodiment of the present invention. In the drawing, 1 is a solution tank, 2 is a solution, 3 is a chemical pump, 5 is a filter, 7 Is the reference electrode,
8 is a counter electrode, 9 is a power supply, 10 is a control circuit, 18 is an exposure mask, and 90 is a wiring. FIG. 2 is an explanatory diagram showing a state of Ta used as an absorber of the exposure mask 18 in an aqueous solution by a relationship between potential and pH.

In FIG. 1, a solution tank 1 is filled with a solution 2 and a chemical pump 3 for circulating a chemical for adjusting the pH of the solution 2 and foreign substances for keeping the solution 2 clean. The filter 5 to be removed is connected. The exposure mask 18, the power supply 9, the control circuit 10, the counter electrode 8, and the reference electrode 7 are connected by the wiring 90 so that the exposure mask 18 is immersed in the solution tank 1 of this apparatus and a voltage can be applied to the absorber 14. It is electrically connected. Here, the counter electrode 8 is, for example, platinum, and the reference electrode 7 is, for example, a standard hydrogen electrode, and silver / silver chloride can be used.

Next, a description will be given of a stress adjusting method in the case where Ta is used as the absorber 14 of the exposure mask 18 using the exposure mask stress adjusting apparatus of the present embodiment. When the position of the alignment pattern on the exposure mask, which has been manufactured for about half a year, is measured by a coordinate measuring device, the absorber pattern on the mask is 0.1 p.
pm, there was a 0.5 ppm error in the vertical direction. Therefore, with the use of the stress adjusting device for an exposure mask of the present embodiment, while applying a voltage of -3.0 V to the pattern film,
The exposure mask 18 was immersed in the solution 2 (for example, using a dilute sulfuric acid solution of about pH 4). The surface of the Ta pattern on the exposure mask 18 that has been used for a long time in the atmosphere is oxidized to Ta ₂ O _5. However, as shown in FIG. By applying a voltage for about 30 minutes, Ta ₂ O ₅ formed on the surface of the Ta pattern
Is reduced to Ta. Therefore, the generated compressive stress can be eliminated. For confirmation, the position accuracy was measured and found to be almost 0 ppm (measurement limit of the apparatus), which is almost immediately after the production.

In this embodiment, the pH is set to 4, and the voltage is set to -3.0.
Although the condition of V was used, the condition can be arbitrarily selected as long as it is a stable condition of Ta shown in FIG. It is preferable that conditions such as the immersion time are optimized according to the set pH and voltage.

Embodiment 2 FIG. After producing an exposure mask using Ta as the absorber 14 in the same manner as in the first embodiment, a diluted ammonia solution having a pH of about 11 was used as the solution 2 of the stress adjusting device for the exposure mask in the first embodiment. A voltage of +2.0 V was applied to the absorber 14 using the power supply 9. Then, the surface of the absorber 14 immediately has Ta ₂ O ₅
Was formed. By applying a voltage for about 30 seconds, Ta oxidation does not proceed any more and a stable state (passive state) is obtained. Although an oxide film is formed on the absorber 14 of the exposure mask 18 according to the present embodiment, stress distortion occurs because the oxide film is formed. Little change. Therefore, particularly when the distortion is close to isotropic distortion, the distortion can be corrected at the exposure stage or the like, so that pattern transfer with high positional accuracy can be achieved.

It should be noted that, in the present embodiment, pH 11, voltage +
Although the condition of 2.0 V was used, the condition can be arbitrarily selected as long as it is a stable condition of Ta ₂ O ₅ shown in FIG. It is preferable that conditions such as the immersion time are optimized according to the set pH and voltage.

Further, in the first embodiment and the present embodiment, an example in which the reference electrode 7 is used has been described. However, when the voltage applied to the absorber 14 can be set only by the counter electrode 8, it may be omitted.

Embodiment 3 FIG. 3 is a diagram showing a schematic configuration of an exposure mask stress adjusting device according to a third embodiment of the present invention. In FIG.
Is a chemical pump, 5 is a filter, 7 is a reference electrode, 8 is a counter electrode, 9 is a power supply, 10 is a control circuit, 18 is an exposure mask, 20 is a stress strain measuring means, and 90 is a wiring. FIG. 4 is an explanatory diagram showing a state of an aqueous solution of W used as an absorber of the exposure mask 18 in relation to a potential and a pH.

As in the exposure mask stress adjusting device described in the first embodiment, in FIG. 3, a solution tank 1 is filled with a solution 2 and a chemical solution for adjusting the pH of the solution 2. And a filter 5 for removing foreign matter in order to keep the solution 2 in a clean state. The exposure mask 18, the power supply 9, the control circuit 10, the counter electrode 8, and the reference electrode 7 are connected by the wiring 90 so that the exposure mask 18 is immersed in the solution tank 1 of this apparatus and a voltage can be applied to the absorber 14. It is electrically connected.

Further, the solution tank 1 is provided with a means 20 for measuring the stress distortion of the exposure mask 18. For example, the back surface of the exposure mask 18 is scanned by a laser installed outside the solution tank 1. The reflected light of the laser is detected, and the warpage of the exposure mask 18 is measured to measure the stress distortion. Based on the measurement result, the potential of the exposure mask 18 with respect to the reference electrode 7 is determined and adjusted by the control circuit 10. Thereby, reduction or oxidation of the absorber 14 is performed.

Next, a description will be given of a stress adjusting method in the case where W is used as the absorber 14 of the exposure mask 18 using the exposure mask stress adjusting apparatus of the present embodiment. In the same manner as in the first embodiment, the exposure mask, which has been manufactured for about half a year, is subjected to pH 11 with the applied voltage of -1.0 V applied.
In a diluted ammonia solution. Under these conditions, W
Is in a stable state, and the surface oxide layer WO ₃ of the absorber 14 is reduced, but the reaction rate is very slow. Here, the applied voltage is gradually increased to about -0.5V. Then, WO ₃ surfaces, negative ions WO ₄ ^{2-next-soluble,}
Etched slowly. The stress of the surface oxide layer is larger than the internal stress, and the average stress of the absorber 14 changes with a very slight etching. When the film stress in the state at the time of manufacture six months ago was used as a reference, the change in the film stress after half a year according to the present embodiment was about 10 MPa. Applied, the pressure almost reached 0 MPa. It was also confirmed that there was almost no dimensional change due to the above etching, and the function of the pattern film was not impaired.

In the present embodiment, pH 11, voltage -1.
Although a condition of about 0 to -0.5 V was used, the WO shown in FIG.
_The condition can be arbitrarily selected as long as the condition for ionizing ₃ is obtained.

In this embodiment, an example is shown in which a means for measuring the film stress uses a means for irradiating a laser beam and detecting the reflected light, but utilizing a change in capacitance or the like. The film stress may be measured.

Further, in the first and second embodiments and the present embodiment, the example in which the absorber 14 of the exposure mask 18 is connected to the wiring 90 has been described. May be connected directly to the absorber 14, for example, via a conductive base film 13 (for example, an ITO film) or a membrane 12 (for example, SiC).

Further, in the first and second embodiments and the present embodiment, an example in which W and Ta are used as the absorber 14 has been described. The stress adjustment method of the present invention can be used with other materials.

Further, in the first and second embodiments and the present embodiment, examples using the control circuit 10, the chemical pump 3, the filter 5, and the like are shown.
If it is not necessary to adjust H and it is not necessary to consider foreign matter, these or some of them may be omitted.

In the first and second embodiments and the present embodiment, an example in which the absorber 14 formed on the surface of the exposure mask 18 is reduced has been described. It may be.

In the first and second embodiments and the present embodiment, the example of the X-ray mask has been described. However, in the case of other exposure masks such as an electron beam and light exposure, the conductive mask provided on the mask may be used. Similar effects can be obtained as long as the film can be used as the first electrode.

In the first and second embodiments and the present embodiment, an example is described in which a silver / silver chloride electrode is used for the reference electrode 7 and platinum is used for the counter electrode. Is also good. For example, as the reference electrode 7, a hydrogen electrode, a calomel electrode, a mercury sulfate electrode, or the like can be used. As the counter electrode 8, a conductive material such as carbon or Si, or a semiconductive material may be used.

Further, in this embodiment and the first embodiment, the example in which the reference electrode 7 is installed in the solution tank 1 has been described. However, the reference electrode 7 is installed in another tank and connected by using a salt bridge or the like. Is also good.

In the first and second embodiments and the present embodiment, the power supply 9 and the control circuit 10 have different structures, but a potentiostat or the like in which these are integrated may be used.

In the first and second embodiments and the present embodiment, an example in which the solution 2 is fixed and the applied voltage is changed has been described.
2 and FIG. 4 to adjust the pH to bring the absorbent into a stable condition.

Embodiment 4 FIG. FIG. 5 is a process chart showing a manufacturing process of an exposure mask according to Embodiment 4 of the present invention. In the manufacturing process of the exposure mask of the present embodiment, first, a membrane is formed on a substrate. Next, a part of the substrate is removed until a part of the back surface of the membrane is exposed. And
A base film is formed on the membrane and fired. Further, an absorber made of a material that blocks exposure light is formed on the base film, a resist is applied and baked, and a support ring is mounted on the back surface of the substrate. Then, the absorber is etched using the patterned resist as a mask,
After that, the resist is removed to form a pattern. Next, a predetermined potential is applied to a solution having a predetermined pH to reduce or oxidize the pattern film. In the exposure mask manufactured in such a process, the film stress is adjusted after the patterning, so that high positional accuracy is secured at the time of exposure, and highly accurate pattern transfer can be performed.

In the present embodiment, a step for measuring the film stress is not particularly shown, but this step may be provided if necessary.

Although the present embodiment does not show a step of correcting a pattern defect, this step may be provided if necessary.

In this embodiment, the step of forming the base film has been described, but may be omitted if unnecessary.

The absorber may be any material that blocks exposure light, such as a scatterer or a reflector. The patterning method may be a lift-off method in which a resist is first patterned and then a film is formed.

Embodiment 5 FIG. A fine circuit pattern of a semiconductor device was transferred using an exposure mask stress-adjusted using the stress adjustment methods of Embodiments 1 to 3 and an exposure mask manufactured by the manufacturing method of Embodiment 4. In order to compare the transfer accuracy, using an exposure mask in which the natural oxidation of the pattern film has progressed after the last half year of manufacture,
Similarly, a fine circuit pattern of a semiconductor device was transferred. The pattern width used was 100 nm in design dimension. Using the above five types of exposure masks, a pattern is transferred onto a wafer for manufacturing a semiconductor device to form wirings, and the positional accuracy of these wirings is compared. The displacement amount becomes 70 nm,
Both the first and third embodiments of the present invention have a thickness of 25 nm, and the fourth embodiment has a thickness of 20 nm.
nm. In the second embodiment, the distortion is corrected at the time of exposure, but the amount of displacement is suppressed to 22 nm. Therefore, by using the stress adjustment method and the manufacturing method of the present invention, it is confirmed that the film stress distortion of the exposure mask is reduced or the change with time is suppressed, so that the wiring pattern accuracy of the semiconductor device is significantly improved. did.

[0046]

As described above, according to the present invention, there is provided a method for adjusting the stress of an exposure mask including a substrate, a membrane, and a pattern film formed on the membrane. Since a predetermined potential is applied to the solution to reduce or oxidize the pattern film to adjust the film stress of the pattern film, it is possible to eliminate the stress generated in the pattern film.

Further, a first electrode composed of the pattern film of the exposure mask having a substrate, a membrane, and a pattern film formed on the membrane, and a second electrode facing the first electrode. Since the electrode and the power supply for supplying current to the first electrode are provided, the pattern film can be set to a desired potential.

Further, the apparatus has a means for measuring the stress strain relating to the pattern film, and a control circuit for controlling the potential of the first electrode with reference to the measured value by the measuring means. , The stress of the pattern film can be quickly and accurately adjusted.

Also, a step of forming a membrane on the substrate, a step of removing a part of the substrate, a step of forming a film made of a material that blocks exposure light on the membrane, and a step of blocking the exposure light Since an exposure mask was manufactured, comprising a step of patterning a film made of a material and a step of applying a predetermined potential in a solution having a predetermined pH and reducing or oxidizing the pattern film, the film stress was adjusted after patterning. And high positional accuracy can be secured during exposure.

Since the pattern is transferred using an exposure mask that has been subjected to stress adjustment using the above-described exposure mask stress adjustment method or an exposure mask manufactured using the above-described exposure mask manufacturing method, wiring And the wiring pattern accuracy of the semiconductor device can be remarkably improved.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an exposure mask stress adjusting device according to a first embodiment of the present invention.

FIG. 2 shows a tantalum (T) according to a first embodiment of the present invention.
It is explanatory drawing which shows the state in aqueous solution of a) by the relationship of an electric potential and pH.

FIG. 3 is a schematic configuration diagram of an exposure mask stress adjusting device according to a third embodiment of the present invention.

FIG. 4 is an explanatory diagram showing a state of tungsten (W) in an aqueous solution according to a third embodiment of the present invention in relation to potential and pH.

FIG. 5 is a manufacturing process diagram of an exposure mask according to a fourth embodiment of the present invention.

FIG. 6 is a manufacturing process diagram of a conventional exposure mask.

[Explanation of symbols]

1 solution tank, 2 solution, 3 chemical pump, 5 filter, 7 reference electrode, 8 counter electrode, 9 power supply, 10 control circuit, 11 substrate, 12 membrane, 13 base film, 14 absorber, 15 resist, 16 support ring, 17 adhesive, 18 exposure mask, 20 stress / strain measuring means, 90 wiring.

Claims (5)

[Claims] 1. A method for adjusting the stress of an exposure mask comprising a substrate, a membrane, and a pattern film formed on the membrane, the method comprising: applying a predetermined potential to a solution having a predetermined pH; Adjusting or reducing the stress of an exposure mask. 2. An exposure mask comprising a substrate, a membrane, and a pattern film formed on the membrane, a first electrode made of the pattern film, and a second electrode facing the first electrode. A stress adjusting device for an exposure mask, comprising: an electrode; and a power supply for supplying a current to the first electrode. 3. The apparatus according to claim 1, further comprising: means for measuring a stress strain related to the pattern film, and a control circuit for controlling a potential of the first electrode by referring to a measured value by the measuring means. Item 3. A stress adjusting device for an exposure mask according to Item 2. 4. A step of forming a membrane on a substrate, a step of removing a part of the substrate, a step of forming a film made of a material that blocks exposure light on the membrane, and a step of blocking the exposure light. A method for manufacturing an exposure mask, comprising: a step of patterning a film made of a material; and a step of applying a predetermined potential in a solution having a predetermined pH to reduce or oxidize the patterned film. 5. An exposure mask that has been subjected to stress adjustment using the exposure mask stress adjustment method according to claim 1, or an exposure mask manufactured using the exposure mask manufacturing method according to claim 4. A semiconductor device with a pattern transferred using a mask.