JPH10104815A - Photomask and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the yield which depends on the phase difference in a phase shift photomask by etching a quartz substrate of a phase shift photomask or a phase shifter part of SiO2 film by using the vapor of a soln. essentially comprising hydrogen fluoride. SOLUTION: A phase shift layer also as a halftone layer 8 on a quartz substrate 1 is an i-line halftone phase shift photomask having a two-layer structure of chromium oxide nitride/chromium nitride and is etched with a vapor of hydrofluoric acid to control the phase difference. A photomask blank is patterned by a laser drawing device and developed with an inorg. alkali developer. The chromium oxide nitride and chromium nitride in the openings are subjected to dry etching with a mixture gas of dichloromethane and oxygen. Then a resist is peeled and the substrate is washed to obtain a halftone phase shift photomask. The obtd. mask is treated with a mixture gas of hydrofluoric acid vapor and water vapor so that the quartz substrate 1 is etched to form an undercut part. Thus, the phase difference is recovered.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photomask and a method for manufacturing the same, and more particularly, to a photomask for adjusting a phase difference by etching a glass portion or a phase shifter portion with HF (hydrofluoric acid) vapor, and a method for manufacturing the same. About the method.

[0002]

2. Description of the Related Art In recent years, as a semiconductor integrated circuit has become more highly integrated, a reticle used for circuit plate making has been required to be further miniaturized. For example, DRAM which is a typical LSI
As an example, the line width of the pattern of the device transferred using these reticles is the current 16 Mb DRAM.
Is as fine as 0.5 μm. In addition, 64Mb
In the fine plate making of DRAM, the exposure method using a conventional stepper has reached its limit at the earliest, and various exposure methods and the like have been studied to meet such a demand. A phase shift photomask is one of them, and if it is used, the resolution can be increased even with a current stepper. Therefore, its development has been actively pursued, and recently it has been introduced into device fabrication.

As a phase shift photomask, FIG.
As shown in the cross-sectional view of FIG. 1A, a Levenson-type structure in which a light-shielding layer 2 having a repetitive pattern is provided on a quartz substrate 1, and the transparent substrate 1 in every other space portion 3 is engraved by a half wavelength with a phase difference. Quartz substrate engraving type phase shift photomask belonging to lower shifter type (Japanese Patent Laid-Open No. 62-189468).
3B, or as shown in the cross-sectional view of FIG. 3B, an etching stop layer 4, a phase shifter layer 5 of SiO ₂ or the like are provided on a quartz substrate 1, and a light-shielding layer 2 having a repetitive pattern is further provided thereon. A Levenson type lower shifter type phase shift photomask having a structure in which the phase shifter layer 5 of every other space portion 6 is engraved, or on a quartz substrate 1 as shown in a sectional view in FIG. An etching stop layer 4 (this etching stop layer 4 is not always necessary) is provided, a light-shielding layer 2 having a repetitive pattern is provided thereon, and a SiO ₂ phase shifter layer 7 is provided on every other space portion. An Levenson type upper shifter type phase shift photomask having a structure provided or a chromium compound or molybdenum silicide on a transparent substrate 1 as shown in a sectional view in FIG. A single-layer halftone phase shift photomask having a pattern of a compound phase shift layer / halftone layer 8 or a halftone light-shielding layer 9 on a transparent substrate 1 as shown in the sectional view of FIG. A multi-layer halftone phase shift photomask having a pattern composed of the shift layer 10 (Japanese Patent Application No. 3-287832) has been developed.

In the case of a phase shift photomask, the phase difference has a great effect on transfer characteristics. In the phase shift photomask, when the phase difference is shifted by more than 180 °, the optimum value of focus shifts. Moreover,
The depth of focus is also reduced. Therefore, the characteristics as a phase shift photomask cannot be fully utilized. As described above, the phase difference plays a large role in the process margin during device fabrication.

[0005]

However, it is very difficult to control the phase difference within an allowable value. Also,
On the other hand, specifications relating to the phase difference are becoming increasingly strict. Taking the production of an i-line halftone phase shift photomask as an example, the thickness of the phase shifter layer of a chrome-based halftone phase shift photomask is about 1400 °. For example, if the phase difference is to be controlled within 5 °, which is the specification value of the phase shift photomask for a 64 Mb DRAM, the film thickness must be controlled with an accuracy within about 40 °. Further, since dry etching has been used, a stricter selection ratio with respect to a quartz substrate as an underlayer has been required for controlling the phase difference.

The present invention has been made in view of the above problems, and an object of the present invention is to improve the yield resulting from the phase difference of a phase shift photomask.

[0007]

SUMMARY OF THE INVENTION Accordingly, the present invention provides a method of etching a quartz substrate of a phase shift photomask or an SiO ₂ -based phase shifter with vapor of a solution containing hydrogen fluoride as a main component. The phase difference is corrected.

As a means for correcting the phase difference, in addition to the present invention, a method of performing dry etching or wet etching of a quartz substrate or an SiO ₂ -based phase shifter is conceivable. The dry etching method will be described by taking a single-layer halftone phase shift photomask as an example in FIG. 4. The phase shift photomask as shown in FIG. A resist 11 is applied, and alignment drawing or back exposure from the back side is performed. As shown in FIG.
Then, the quartz substrate 1 is dry-etched through the resist 11 as shown in FIG. 4D, and a predetermined amount of the quartz substrate 1 in the space is etched as shown in FIG. And a method of directly performing dry etching via the phase shift layer and halftone layer 8 without applying a resist, as shown in FIG.

In the former, a resist coating step and an exposure step are added, so that the accompanying steps become complicated and
There is a possibility that a new defect is generated by the process. In the latter case, the transmittance increases in the case of a halftone phase shift photomask, and the low reflection layer is damaged in the case of a Levenson type phase shift photomask using low reflection chromium.

In the wet etching method,
Usually, hydrofluoric acid or a hydrofluoric acid interference solution is used for the etchant. This is because hydrofluoric acid etches only the quartz substrate without etching the phase shift layer / halftone layer and the light shielding layer. However, hydrofluoric acid-based solutions are very dangerous and require sufficient knowledge and care in handling. In addition, exclusion facilities are required. In the case of a photomask, since it is a multi-product, small-quantity production, it does not have a consistent full-auto line like a semiconductor factory, and there is a large barrier to handling hydrofluoric acid.

However, hydrofluoric acid vapor is introduced into the chamber,
In the method of processing under reduced pressure, processing of the solution is unnecessary,
The vapor and reaction products are exhausted by a vacuum pump through a simple exclusion facility. Therefore, there is no need to handle dangerous solutions by humans, and it is safe. In addition, etching with hydrofluoric acid vapor can eliminate complicated steps such as resist coating and exposure, and furthermore, since plasma is not used unlike dry etching, damage to the low reflection film due to ion bombardment or the like is caused. This is very effective because it can prevent an increase in transmittance.

These phase-shift photomasks include a single-layer or multilayer halftone phase-shift photomask containing molybdenum silicide as a main component, a single-layer or multilayer halftone phase-shift photomask containing a chromium compound as a main component, Alternatively, any known phase shift photomask such as a Levenson type phase shift photomask may be used.

When etching is performed using a system in which water vapor is added to hydrofluoric acid vapor, the etching rate is improved.
In addition, by performing the treatment under reduced pressure, the etching rate can be easily controlled.

It is desirable that the phase shift / halftone layer and the light shielding layer of the photomask have sufficient resistance to hydrofluoric acid.

It is desirable that the Levenson-type phase shift photomask has an etching stopper layer when the phase shifter layer is dry-etched.

When the Levenson type phase shift photomask is a lower shifter type phase shift photomask,
Since the phase shifter layer under the light-shielding layer is undercut by etching with hydrofluoric acid vapor, the space between the space where the phase shifter remains and the space where the phase shifter does not remain (the portion denoted by reference numeral 6 in FIG. 3B). The difference in transmitted light intensity between the two is reduced.

As is apparent from the above description, the photomask of the present invention is characterized in that the glass portion or the phase shifter portion of the photomask is etched by hydrofluoric acid vapor or the vapor of a solution containing hydrofluoric acid as a main component. It is assumed that.

In this case, it is desirable that the glass portion or the phase shifter portion of the photomask is etched by a system to which steam is added, and that the treatment is performed under reduced pressure.

Preferably, the photomask is a phase shift photomask, and the phase difference is adjusted by etching a glass portion or a phase shifter portion.

As the phase shift photomask, there are a halftone type phase shift photomask and a Levenson type phase shift photomask. In the case of the Levenson type lower shifter type phase shift photomask, the phase shifter below the light shielding layer is used. The layer will have undercuts.

Further, the method of manufacturing a photomask according to the present invention is characterized in that after patterning the photomask, the glass portion or the phase shifter portion of the photomask is etched with hydrofluoric acid vapor or a vapor of a solution containing hydrofluoric acid as a main component. Characteristic method.

In this case, it is desirable to etch the glass part or the phase shifter part of the photomask with a system to which water vapor is added, and it is desirable to perform the treatment under reduced pressure.

The photomask is a phase shift photomask, and it is desirable to adjust the phase difference by etching the glass portion or the phase shifter portion.

As the phase shift photomask, there are a halftone type phase shift photomask and a Levenson type phase shift photomask. In the case of the Levenson type lower shifter type phase shift photomask, the phase shifter below the light shielding layer is used. The layer will have undercuts.

By using the photomask of the present invention and the method of manufacturing the photomask of the present invention, the transparent substrate quartz can be used in any of a single-layer or multilayer halftone phase-shift photomask and a Levenson-type phase-shift photomask. The phase difference can be adjusted by etching the substrate or the phase shifter with hydrofluoric acid vapor or the vapor of a solution containing hydrofluoric acid as a main component, thereby improving the yield and shortening the manufacturing period. Can be.

[0026]

Embodiments of a photomask and a method of manufacturing a photomask according to the present invention will be described below. Embodiment 1 In this embodiment, as shown in FIG. 1, a phase shift layer / halftone layer 8 on a quartz substrate 1 is made of chromium oxynitride (130 nm thick) / chromium nitride (10 nm thick).
This is an example in which an i-line halftone phase shift photomask having a layer structure is etched with hydrofluoric acid vapor to adjust the phase difference.

The pattern on the reticle is 16Mb DRAM
And the applicable layer is a contact hole. A novolak-based positive resist NPR895I (Nagase Sangyo Co., Ltd.) was used as a resist for the photomask blanks. Photomask blanks are converted into laser drawing equipment CORE2564 (ETEC SYSTEM)
And developed with an inorganic alkali developer, and the chromium oxynitride and the chromium nitride in the opening are replaced with dichloromethane (C
Dry etching was performed by reactive ion etching using a mixed gas of H ₂ Cl ₂ ) and oxygen. Thereafter, the resist was removed, and after cleaning, a halftone phase shift photomask as shown in FIG. 1A was obtained. When the phase difference was measured with a phase difference measuring device MPM-100 (Lasertec Corporation), the i-line wavelength was 173 °.

Therefore, in order to improve the phase difference by about 7 °,
When the halftone phase shift photomask was treated with a mixed gas of hydrofluoric acid vapor and water vapor under a reduced pressure of about 600 Pa and a chamber temperature of about 25 ° C. for 20 seconds, FIG. As shown, the quartz substrate 1 exposed from the space portion of the phase shift layer / halftone layer 8 was etched with an undercut (side etching). The halftone phase shift photomask was taken out of the etching apparatus, and the phase difference was measured again. As a result, it was 179 °, and it was confirmed that the phase difference was recovered by the present invention.

Embodiment 2 In this embodiment, as shown in FIG. 2, chromium oxide and chromium 2 (11
0 nm thickness), SOG (spin-on-glass) phase shifter 5 (380 nm thickness), Hafnia etching stopper 4 (5 nm), i-line Levenson type lower shifter type phase shift photomask having a three-layer structure, etching with hydrofluoric acid vapor Is applied to adjust the phase difference.

The pattern on the reticle is 64Mb DRAM
, And the applicable layer is a bit line. Novolak-based positive resist EBR900 (Toray Industries, Inc.) was used as the resist for the photomask blanks. This Levenson-type lower shifter-type phase shift photomask uses a photomask blank as an EB drawing apparatus M
Draw with EBES-IV (ETEC SYSTEM), develop with an inorganic alkali developer, wet etch chromium oxide and chromium in the opening, and then
The resist is peeled off, and after cleaning, the same resist is applied again, and a laser drawing apparatus CORE2564 (ETEC SY)
After alignment drawing by STEM Co., developed with an inorganic alkali developing solution, the opened phase shifter portion was dry-etched using CF ₄ gas, and the resist was peeled off.
After washing, a Levenson-type lower shifter type phase shift photomask as shown in FIG. 2A was manufactured. Thereafter, when the phase difference was measured by a phase difference measuring device MPM-100 (Lasertec Corporation), it was 191 ° in i-line wavelength.

Therefore, in order to improve the phase difference by about 11 °, the phase shift photomask is formed using a mixed gas of hydrofluoric acid vapor and water vapor under a reduced pressure condition of about 600 Pa and a chamber temperature of about 25 ° C. After the processing for 25 seconds, as shown in FIG. 2B, the phase shifter 5 exposed from the space where the phase shifter 5 of the light shielding layer 2 is left remains.
Was etched with an undercut (side etching), and the phase shifters 5 on both sides were undercut (side etched) through the space where the phase shifter 5 did not remain. The Levenson-type lower shifter-type phase shift photomask was taken out of the etching apparatus, and the phase difference was measured again. As a result, it was 180 °, and it was confirmed that the phase difference was recovered by the present invention.

[0032]

As is clear from the above description, according to the photomask and the method of manufacturing the same of the present invention, etching is performed under reduced pressure using hydrofluoric acid vapor or a mixed gas of hydrofluoric acid vapor and water vapor. Correction of phase difference becomes possible,
The yield can be improved by the variation of the phase difference.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view for explaining a process of Example 1 for adjusting a phase difference of a halftone phase shift photomask according to the present invention.

FIG. 2 is a cross-sectional view for explaining a process of a second embodiment for adjusting a phase difference of a Levenson-type lower shifter type phase shift photomask according to the present invention.

FIG. 3 is a cross-sectional view of some phase shift photomasks to which the present invention can be applied.

FIG. 4 is a cross-sectional view for explaining a phase difference adjusting method that can be considered other than the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Transparent substrate 2 ... Light shielding layer 3 ... Space part 4 ... Etching stop layer 5 ... Phase shifter layer 6 ... Space part 7 ... Phase shifter layer 8 ... Phase shift layer and halftone layer 9 ... Halftone light shielding layer 10 ... Phase shift Layer 11: Resist

Claims (14)

[Claims] 1. A photomask, wherein a glass portion or a phase shifter portion of a photomask is etched by hydrofluoric acid vapor or vapor of a solution containing hydrofluoric acid as a main component. 2. The photomask according to claim 1, wherein a glass portion or a phase shifter portion of the photomask is etched by a system to which water vapor is added. 3. The photomask according to claim 1, wherein the photomask is processed under reduced pressure. 4. The photomask according to claim 1, wherein the phase difference is adjusted by etching a glass portion or a phase shifter portion. 5. The photomask according to claim 4, wherein the phase shift photomask is a halftone type phase shift photomask. 6. The photomask according to claim 4, wherein the phase shift photomask is a Levenson type phase shift photomask. 7. The photo-sensor according to claim 6, wherein the phase shift photomask is a Levenson type lower shifter type phase shift photomask, and the phase shifter layer below the light shielding layer has an undercut. mask. 8. A method for manufacturing a photomask, comprising etching a glass portion or a phase shifter portion of a photomask with hydrofluoric acid vapor or a vapor of a solution containing hydrofluoric acid as a main component after patterning the photomask. 9. The method for manufacturing a photomask according to claim 8, wherein a glass part or a phase shifter part of the photomask is etched by a system to which water vapor is added. 10. The method for manufacturing a photomask according to claim 8, wherein the treatment is performed under reduced pressure. 11. The photomask according to claim 8, wherein the photomask is a phase shift photomask, and after patterning, adjusting a phase difference by etching a glass part or a phase shifter part. Production method. 12. The method according to claim 11, wherein the phase shift photomask is a halftone type phase shift photomask. 13. The method according to claim 11, wherein the phase shift photomask is a Levenson type phase shift photomask. 14. The photomask according to claim 13, wherein the phase shift photomask is a Levenson type lower shifter type phase shift photomask, and an undercut is formed in the phase shifter layer below the light shielding layer. Production method.