KR100277006B1 - Method for tuning an attenuating phase shift mask - Google Patents

Abstract

The present invention provides a method and apparatus for tuning phase shifting of a phase shift mask having an attenuation phase shifting material that provides a phase shift of at least 160 degrees. The method using phase measurement and selective etching operation reduces the problem of having to produce an accurate 180 ° phase shifting mask. An attenuation phase shift mask structure is also disclosed herein.

Description

TECHNICAL FOR TUNING AN ATTENUATING PHASE SHIFT MASK

This application is the CIP application of US patent application Ser. No. 08 / 949,916, filed October 14,1997.

TECHNICAL FIELD The present invention relates to optical lithography, and more particularly, to a method and apparatus for tuning phase shifting of a phase shift mask with attenuating phase shifting material that provides at least 160 ° phase shifting. Specifically, the method of the present invention includes (1) a part of the transparent or semitransparent substrate to which the phase shifting material is attached, (2) a part of the phase shifting material, or (3) a transparent or semitransparent substrate and the phase shifting material. By controlling the removal of a portion of the direct phase shifting material can be tuned. By controlling this removal, the phase shift mask can be tuned directly to about 180 ° during mask fabrication. The invention also relates to an attenuation phase shift mask structure that measures a phase between about 170 ° and about 190 °.

Phase shifting techniques are one of the useful methods that can be used to improve the performance of optical lithography. The attenuation phase shifting mask typically consists of an absorbing phase shifting material having a transmission of about 5-20% and a transparent or translucent substrate. The absorption shift pattern has been formed in a two-layer structure consisting of a SiO ₂ film for controlling phase and a Cr thin film for controlling transmittance.

Also known are single layer shifters consisting of oxynitride films of oxides or MoSis, such as "Practical attenuated phase-shifting mask with a single-layer absorptive shifter of MoSiO and MoSiON for ULSI fabrication" by Yoshioka et al. , IEEE, IEDM 93 pp. 653-656. Such attenuation phase shift masks may include sequentially attaching a MoSiO shifter, a Mo film, and a resist to a glass substrate, developing the resist, and exposing the exposed areas of the glass substrate to CF ₄ and O ₂ . Reactive ion etching in a gas mixture, removing the resist using an oxygen plasma, and wet etching the Mo film layer. The monolayer attenuated phase shift mask produced by the method described by Yoshioka et al. Has a 180 ° phase shift and transmittance of about 5-20%. In the disclosure of Yoshioka et al., The desired phase shifting is obtained by selecting a substrate material having a phase shift of about 180 °. During the manufacturing process disclosed in Yoshioka et al., These 180 ° phase shifts can be deviated.

As is well known to those skilled in the art, attenuation phase shift masks can produce high resolution images on a wafer when manufactured according to tight 180 ° tolerances (for mask application wavelengths). Due to changes in the leading phase shift film and the means in manufacturing the same mask, errors may occur in the mask from the desired 180 ° phase shift.

As disclosed in Yoshioka et al., The prior art requires a number of processing steps to form the attenuation phase shift mask. Many of these processing steps can involve a significant phase shift from the desired 180 °. In other words, prior art processes do not account for the mean phase error that occurs during the fabrication of the attenuation phase shift mask. Accordingly, there is a need to develop new and improved methods for fabricating attenuated phase shift masks that compensate for average phase errors in phase shifting materials. Specifically, it is necessary to develop a method of tuning the mask to 180 ° during its manufacturing process, while eliminating all of the above-mentioned drawbacks of prior art processes.

One object of the present invention is to provide a method for tuning an attenuation phase shift mask to the correct phase.

It is another object of the present invention to provide a method for compensating for the phase error of attenuation phase shifting material that may occur during the manufacture of attenuation phase masks.

It is another object of the present invention to provide a method of making attenuated phase masks tuned to about 180 ° with high accuracy.

Another object of the present invention is to provide an apparatus for manufacturing a phase shift mask that can be tuned to about 180 °.

In one embodiment of the invention, to provide a phase shift of 20 ° or less in a substrate, another method may be used, which comprises removing, under predetermined control, a portion of a transparent or translucent substrate having a phase shifting material attached thereto. Not only the object but also the above object is achieved. Specifically, in this aspect, the present invention relates to a method for tuning phase shifting of a phase shift mask having an attenuating phase shifting material that provides at least 160 ° phase shifting.

(a) forming a line segment phase in the phase shifting material, wherein the phase shifting material is located on a transparent or translucent substrate;

(b) measuring the actual phase shift provided by the imaged phase shifting material,

(c) etching the substrate in an amount sufficient to provide a phase shift of about 180 [deg.] in an area not covered with the imaged phase shifting material.

According to this embodiment of the invention, step (a) spins a photoresist on a layer of phase shifting material that has previously been attached to a transparent or translucent substrate, and lines on a predetermined area of the photoresist. And patterning, developing the photoresist, and etching an area of the phase shifting material that does not contain the developed photoresist and the desired pattern. In step (b) of the present invention, a laser beam and a phase interferometer are used to determine the actual phase shift caused by the phase shifting material. Step (c) of the present invention includes wet etching, dry etching, or a combination of the two, and optionally a phase of no more than 20 ° from the transparent or translucent substrate to tune the phase shifting material formed at about 180 °. Remove the shift.

In yet another embodiment of the present invention, the phase shift of a phase shift mask with attenuating phase shifting material providing a phase shift of about 160 ° is performed by performing steps (a) and (b) above. (c ') etching a portion of the imaged phase shifting material by an amount sufficient to provide about 180 [deg.] phase shift to the phase shifting material. This embodiment of the invention is employed when the attenuation phase shifting material has a measured phase that is greater than the desired predetermined value.

In another embodiment of the present invention, the controlled etching of the substrate and phase shifting material may be used together to tune the phase shifting material. According to this aspect of the invention, the method

(a) forming a line segment image in the phase shifting material, wherein the phase shifting material is located on a predetermined area of the transparent or translucent substrate;

(b) measuring the actual phase shift provided by the imaged phase shifting material,

(c) etching the substrate in an area not covered by the imaged phase shifting material in an amount sufficient to provide a phase shift of about 180 degrees, or

(c ') etching a portion of the imaged phase shifting material in an amount sufficient to provide a phase shift of about 180 degrees;

(d) repeating steps (b) and (c) or (c ') several times until a phase shift of 180 degrees is obtained.

Another aspect of the invention is directed to an apparatus for tuning phase shifting of a phase shift mask having an attenuation phase shifting material that provides at least 160 ° phase shifting. Specifically, the apparatus of the present invention,

(a) means for measuring the actual phase shift provided by the line imaged mask, wherein the line imaged mask is made of a phase shifting material positioned on a transparent or translucent substrate and providing at least 160 ° phase shifting;

(b) means for etching the transparent or translucent substrate to a depth that provides a phase shift of about 20 degrees or less within the substrate;

(c) means for providing feedback when said etching is complete.

In another embodiment, means (b) comprises means (b ') comprising means for etching the phase shifting material to a depth that provides a phase shift of between about 0.01 and 20 degrees in the phase shifting material. Alternatively, or alternatively, means (b) and (b ') may be used together.

Another aspect of the invention is an attenuation phase mask structure comprising a transparent or translucent substrate having attenuation phase shift material over a portion of a substrate, wherein the substrate, the phase shift material, or both are in the substrate or the phase shift material. And an area etched to provide a phase shift of about 0.01 degrees to about 20 degrees.

1 (a) to (d) are side cross-sectional views of an attenuation phase shift mask prepared according to an embodiment of the present invention, (a) relates to a mask structure before performing step (a) of the present invention, ( b) relates to the mask structure after performing step (a), (c) relates to the mask structure after wet etching, and (d) to sectional view of the mask structure after dry etching.

FIG. 2 shows a means for determining the difference in transmittance between an imaged mask and a transparent or translucent substrate. FIG.

3 shows one embodiment of the device of the present invention.

4 (a) to (c) are side cross-sectional views of attenuation phase shift masks prepared in accordance with an alternative embodiment of the present invention, wherein (a) relates to the mask structure prior to performing step (a) of the present invention, (b) relates to the mask structure after performing step (a), and (c) is a side cross-sectional view of the mask structure after dry etching.

Explanation of symbols for the main parts of the drawings

10 substrate 12 phase shifting material

14: photoresist 18: undercut

20: laser source 22: beam splitter

24: phase interferometer 26,26 ', 26' ': beam

32: feedback device 34: robot arm

DETAILED DESCRIPTION The present invention provides a method and apparatus for tuning phase shifting of a phase shift mask as well as a phase mask structure, which will now be described in more detail with the accompanying drawings, wherein like reference numerals are used to represent like corresponding components of the drawings. .

As mentioned above, one aspect of the present invention relates to a method for tuning phase shifting of a phase shift mask having an attenuating phase shifting material therein providing at least 160 ° phase shifting therein. According to step (a) of the present invention, a line segment image is formed in a phase shifting material located on a transparent or translucent substrate. Specifically, as shown in Fig. 1 (a), the line segment image is formed as follows. First, the phase shifting material 12 is attached to one surface of the transparent or translucent substrate 10 using conventional techniques well known to those skilled in the art. For example, the phase shifting material may be deposited on a substrate using conventional chemical vapor deposition (CVD) or direct current (DC) sputtering.

Suitable materials from which the transparent or translucent substrate 10 may be made include, but are not limited to, quartz, glass, calcium fluoride, diamond, diamond like carbon, and the like. As the substrate 10, the most preferred material used in the present invention is quartz.

The transparent or translucent substrate 10 used in the present invention may be used as is, or cleaned prior to use, using techniques well known to those skilled in the art, effective for removing any contaminants from the substrate.

Note that in the prior art, it is important for the substrate material of the phase shift mask to have a phase shift as close to 180 ° as possible. This is because only a significant deviation from 180 [deg.] Will result in significant phase error that cannot be compensated during attenuation phase mask fabrication. In the present invention, it is not important to initially use a substrate material having a phase shift of 180 degrees. Typically, the substrate material used in the present invention initially has a phase shift of about 170 degrees to about 178 degrees.

Any attenuating phase shifting material that is translucent and has a phase shift of at least 160 °, well known to those skilled in the art, can be used as layer 12. Examples of phase shifting materials that can be used in the present invention by meeting the above criteria include, but are not limited to, MoSi, carbon, chromium oxide, chromium nitride, silicon nitride, chromium fluoride, chromium oxide fluoride, and the like. The most preferred phase shifting material used in the present invention is MoSi.

After attaching phase shifting material 12 to substrate 10, photoresist 14 is spun onto layer 12 using conventional techniques well known to those skilled in the art. Any photoresist that can be recorded, i.e. patterned, and sensitive to e-beam or laser light exposure can be used in the present invention. This includes not only negative photoresists but also positive photoresists. Examples of suitable photoresists used in the present invention include, but are not limited to, poly (butene 1-sulphone) (PBS) and 895i, which are positive novolak resists.

The desired pattern is then provided into the photoresist using conventional electron beam or laser recording techniques well known to those skilled in the art. For example, one method of recording a desired pattern in photoresist 14 is to write a reference data design by an electron beam using a raster-scan. This technique transfers the designed pattern from the reference data to the photoresist 14.

After providing the desired pattern to the photoresist 14, a conventional method—this is MIAK (methyllisobutyketone: methyl isobutyl ketone with sodium hydroxide, tetramethylammonium hydroxide (TMAH), isopropyl alcohol) ), Or a mixture thereof, but not limited thereto. This forms a resist structure comprising a pattern thereon. Next, this mask is etched using standard etching techniques well known to those skilled in the art and includes a structure having a phase shift material formed thereon, i.e., a substrate having a mask 12 ', shown in FIG. To provide. Note that this etching step of the present invention is performed using dry plasma etching, which is highly selective for phase shift materials. In this step of the present invention, almost no etching to the substrate 10 occurs. Suitable dry plasma etchant, which is highly selective for phase shifting materials, includes, but is not limited to, CF ₄ , CHF ₃ , O ₂ , SF _6, and combinations thereof.

According to step (b) of the present invention, the actual phase shift provided by the formed phase shifting material 12 'is then measured using the means shown in FIG. Specifically, FIG. 2 shows the laser source 20, the beam splitter 22, the structure of FIG. 1B and the phase interferometer 24. First, a measurement is made by passing beam 26 through beam splitter 22 to split the laser beam from laser source 20 into two beams 26 'and 26' 'respectively. One of the divided beams, for example 26 '', is focused on a portion of the substrate 10, and the other, for example 26 ', is focused on the formed phase shifting material 12'. The two beams leaving this structure then pass through a phase interferometer, where the phase difference between the two beams representing the phase shift of the imaged phase shifting material is determined.

Using the means shown in Fig. 2, the actual phase shift of the imaged phase shifting material is determined, and in this embodiment, the imaged phase shifting material 12 'is removed using a controlled etching regime. By removing a portion of the substrate 10 that is not included, this actual phase shift can be used to tune the imaged mask fairly accurately to about 180 degrees. Control etching is performed by dry etching, wet etching or using them together. Note that the controlled etching step (c) of the present invention is quite selective for etching the transparent or translucent substrate 10. According to the present invention, the conditions used in this step of the present invention are sufficient to remove sufficient substrate to provide a phase shift of about 0.01 ° to about 20 ° in the substrate. The amount of material to be removed is determined by the degree to which the imaged phase shifting material 12 'deviates from 180 degrees. For example, if the imaged mask has a phase shift of 175 degrees, the mask can be tuned by selectively removing a portion of the substrate 10 to provide a phase shift of 5 degrees in the substrate. In this way, a mask tuned to 180 degrees is formed.

Suitable dry etching techniques that may be used in the present invention to selectively remove portions of the substrate 10 include reactive ion etching (RIE), chemical dry etching, ion beam etching, plasma etching, and the like. Gases that can be used in these dry etching techniques are those that are very familiar with transparent or translucent substrates. Examples of suitable gases that can be used in the present invention include CF ₄ , SF ₆ , NF ₃ , CHF ₃ and combinations thereof. These gases may also be used with oxygen or other chemicals such as argon, nitrogen and helium (He).

When wet etching is used to selectively etch a transparent or translucent substrate 10 comprising an imaged phase shifting material 12 ′, the chemical etchant used includes HF, NaOH, buffered HF, and the like. Mixtures consisting solely of these chemical etchantes or mixtures in which water is added to these etchantes are also contemplated herein. Chemical etchant can also be buffered to the desired pH using well known buffering agents. The most preferred chemical etchant used in the present invention is buffered HF.

Note that the above-described selective etching step of the present invention is performed to provide a mask having a phase shift of about 180 degrees. Typically, this controlled etching step removes the substrate material from about 10 kPa to about 300 kPa. The final structure formed from the present invention is shown in Figures 1 (c) and (d). Specifically, FIG. 1C shows the attenuation phase mask of the present invention, wherein the substrate is etched using a chemical etchant. Note that undercut 18 is present in this structure because a chemical etchant is used in step (c). In Fig. 1 (d), the attenuation mask is tuned by etching the substrate in a dry etching process. In this case, the undercut 18 does not exist at all.

Reference is now made to FIGS. 4 (a) to (c), which show alternative embodiments of the method of the invention. In this alternative embodiment, the phase shift of the imaged phase shifting material 12 'is tuned by selectively removing, ie etching, the phase shifting material itself. This embodiment of the invention is used when the measured phase shift of the imaged phase shift mask 12 'is greater than the selected target value. Note that in this embodiment of the present invention, steps (a) and (b) described above with respect to FIG. 1 are first performed, and then the phase shifting material is selectively etched instead of the substrate.

The imaged phase shifting material is selectively etched in the present invention by using an etching process that is highly selective for the phase shifting material. Dry etching, chemical etching, or a combination thereof may be used to selectively etch the phase shifting material. In FIG. 4C, dry etching is used to remove part of the phase shifting material 12 ′ formed. In a typical process, the phase shifting material that is imaged from about 5 Hz to about 500 Hz is removed.

Suitable dry etching that may be used to etch the imaged phase shifting material includes those described above. Selective etching is accomplished by changing the pressure of the etching technique. Low pressures from about 5 to about 15 (mTorr) are used to selectively dry etch the substrate, while higher pressures from about 100 to about 300 mTorr are used to selectively dry etch the phase shifted material that is formed.

When wet etching is used to etch the imaged phase shifting material 12 ', the chemical etchant used includes sulfuric acid and the like. Mixtures consisting solely of these chemical etchantes or mixtures in which water is added to these etchantes are also contemplated herein. In addition, well known buffers can be used to buffer the chemical etchant to the desired pH.

In addition to using each of the above selective etching processes separately, the use of them together may also be considered in the present invention. According to this embodiment of the invention, steps (a) and (b) are performed first, and then either the substrate or the phase shifting material is selectively etched. Next, the phase shift of the mask is again measured using step (b), and then etching of the substrate or phase shifting material may be performed if necessary. Note that the substrate is etched if the measured phase shift is less than the predetermined value, while the phase shifting material is etched if the phase shift is greater than the predetermined value.

According to a second aspect of the invention, an apparatus for tuning phase shifting of a phase mask is provided. Specifically, the apparatus of the present invention

(a) means for measuring the actual phase shift provided by the line imaged mask, wherein the line imaged mask is made of a phase shifting material positioned on a transparent or translucent substrate to provide a phase shift of at least 160 °;

(b) means for etching any of the transparent or translucent substrates, the phase shifting material, or both, to a predetermined depth to provide a phase shift of about 20 degrees or less;

(c) means for providing feedback when the etching is complete;

(d) optionally, means for stopping said etching.

Reference is made to FIGS. 2 and 3 illustrating the apparatus of the present invention. Specifically, Figure 2, which has been discussed in more detail above, shows the measuring means of the device of the invention. The measuring means shown in FIG. 2 is used in FIG. 3 which shows all the means of the apparatus of the present invention. In addition to the laser source 20, the beam splitter 22, the phase interferometer 24, the phased phase shift material 12 ′ and the substrate 10, the apparatus of the present invention also includes a housing means 30-here a substrate. Either dry or wet etching to (10) occurs—feedback device 32 and a tuned mask, such as a computer or alarm device, to indicate when the phase of this structure is within 180 ° from the etching medium. Robot arm 34 for removal. When using a wet etchant, the housing means comprise a suitable chemical etchant which is very selective for transparent or translucent substrates. On the other hand, when dry etching is performed, the housing means comprises a source region for bombarding to impact the mask formed with a suitable etchant gas.

The foregoing illustrates a number of phase shift mask structures that can be formed from the present invention, as well as apparatus and methods thereof. Note that the method of the present invention provides a means for directly tuning the attenuation phase shift mask to about 180 degrees with significant accuracy.

While the present invention has been particularly shown and described with respect to its preferred embodiments, those skilled in the art will understand that the foregoing and other modifications may be made in form and detail without departing from the scope and spirit of the invention. Accordingly, the invention is not to be limited to the precise forms described and illustrated, but should be considered to include all modifications that may fall within the scope of the appended claims. For example, this principle also applies to masks using techniques having a wavelength smaller than light, such as X-rays.

Thus, according to the present invention, there is provided a method of tuning the attenuation phase shift mask to the correct phase, a method of compensating for the phase error of the attenuation phase shifting material that may occur during manufacture of the attenuation phase mask, and tuning to about 180 ° with high accuracy. A method of manufacturing a reduced attenuation phase mask and an apparatus for manufacturing a phase shift mask that can be tuned to about 180 degrees are provided.

Claims (32)

A method of tuning phase shifting of a phase shift mask with attenuating phase shifting material that provides at least 160 ° phase shifting, (a) forming a line segment image in the phase shifting material, wherein the phase shifting material is located on a predetermined area of transparent or translucent material; and (b) measuring the actual phase shift provided by the imaged phase shifting material, (c) etching the transparent or translucent substrate not covered by the imaged phase shifting material by a predetermined amount to provide a phase shift of about 180 degrees, or (c ') etching the formed phase shifting material by a predetermined amount to provide a phase shift of 180 degrees. The method of claim 1, Step (a) is performed by attaching a photoresist to a substrate comprising the transparent or translucent substrate having a predetermined layer of phase shifting material thereon, and patterning, developing, and etching the photoresist. The method of claim 1, Step (b) is performed by determining the phase difference between the laser beam passing through the substrate and the beam passing through the formed phase shifting material. The method of claim 1, Step (c) is a controlled etching step that is quite selective for the substrate. The method of claim 4, wherein And said controlled etching of said substrate comprises wet etching or dry etching. The method of claim 5, And said dry etching of said substrate comprises reactive ion etching, ion beam etching, dry chemical etching or plasma etching. The method of claim 6, And said dry etching of said substrate is performed using a gas selected from the group consisting of CF ₄ , SF ₆ , NF ₃ , CHF ₃ , a mixture consisting of only these, or a mixture in which oxygen is added thereto. The method of claim 5, And wherein said wet etching of said substrate comprises a chemical etchant selected from the group consisting of HF, NaOH, BHF, mixtures consisting solely, or mixtures added thereto with water. The method of claim 1, Step (c) removes the transparent or translucent substrate from about 10 microseconds to about 300 microseconds. The method of claim 1, Step (c ') is a controlled etching step that is highly selective for the imaged phase shifting material. The method of claim 10, And wherein said controlled etching of said phased phase shifting material comprises a wet etch or a dry etch. The method of claim 11, And said dry etching of said imaged phase shifting material comprises reactive ion etching, ion beam etching, dry chemical etching, or plasma etching at pressures from about 100 mTorr to about 300 mTorr. The method of claim 12, Said dry etching of said phase shifted material is carried out using a gas selected from the group consisting of CF ₄ , SF ₆ , NF ₃ , CHF ₃ , mixtures thereof, or mixtures with oxygen added thereto. . The method of claim 11, And said wet etching of said phased phase shifting material comprises a chemical etchant selected from the group consisting of sulfuric acid, a mixture consisting only of them, or a mixture of water applied thereto. The method of claim 1, Step (c ') removes the imaged phase shifting material from about 5 Hz to about 500 Hz. The method of claim 1, After performing step (c) or (c '), steps (b) and (c) or (c') are repeated several times to provide a phase shift of about 180 degrees. The method of claim 1, Wherein said transparent or translucent substrate comprises quartz, glass, diamond, diamond-like carbon or calcium fluoride. The method of claim 1, The phase shifting material comprises MoSi, carbon, chromium oxide, chromium nitride, silicon nitride or chromium oxide fluoride. An apparatus for tuning phase shifting of a phase shift mask having a phase shifting material that provides at least 160 ° phase shifting, (a) means for measuring the actual phase shift provided by the line imaged mask, wherein the line imaged mask is made of a phase shifting material positioned on a transparent or translucent substrate to provide a phase shift of at least 160 °; (b) means for etching any of the transparent or translucent substrates, the phase shifting material, or both, to a predetermined depth to provide a phase shift of about 20 degrees or less; (c) means for providing feedback when the etch is complete. The method of claim 19, Means (b) is replaced by means (b ') for selectively etching the imaged phase shifting material to a predetermined depth to provide a phase shift of less than about 20 degrees in the imaged phase shifting material. . The method of claim 19, Means (b ') for selectively etching said imaged phase shifting material to a predetermined depth to provide a phase shifting of about 20 degrees or less within said imaged phase shifting material. The method of claim 19, Said measuring means comprising a laser beam energy source, a beam splitter and a phase interferometer. The method of claim 19, And said selective etching means comprises dry etching or wet etching housing means. The method of claim 23, wherein Said dry etching housing means comprising a source for impacting said imaged mask with a gas etchant. The method of claim 23, wherein Said wet etching housing means comprising a chemical etchant. The method of claim 19, And said feedback means is a computer or alarm device. The method of claim 19, and (d) means for stopping said etching. The method of claim 27, And said stopping means comprises a robotic arm. A phase shift of 180 °, comprising a transparent or translucent substrate having an imaged phase shifting material over a portion of the substrate, wherein the substrate has a phase shift of from about 0.01 ° to about 20 ° in the transparent or translucent substrate. Comprising a region etched to a depth sufficient to provide an attenuation phase mask structure. The method of claim 29, The transparent or translucent substrate is attenuated phase mask structure consisting of quartz, glass, diamond, diamond-like carbon or calcium fluoride. The method of claim 29, The phase shifting material comprises MoSi, carbon, chromium oxide, chromium nitride, or silicon nitride. A phase shift of 180 ° comprising a transparent or translucent substrate having an imaged phase shifting material on a portion of the substrate, wherein the imaged phase shifting material is from about 0.01 ° to about within the imaged phase shifting material. Including areas etched to a depth sufficient to provide a phase shift of 20 ° —attenuation phase mask structure.