JP2004199089A - Halftone phase shift mask blank and halftone phase shift mask - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a halftone phase shift mask blank and a halftone phase shift mask which do not cause changes in the optical constants such as transmittance, a refractive index and an extinction coefficient even when the blank and mask are subjected to a heat treatment and a specified chemical treatment. <P>SOLUTION: The halftone phase shift mask blank 10 is manufactured by sputtering a zirconium or zirconium silicide target in an atmosphere of nitrogen, oxygen, gaseous halogen or the like to form a translucent film 12 consisting of a zirconium or zirconium compound film with an adjusted refractive index, extinction coefficient and film thickness on a transparent substrate 11 consisting of quartz glass, and then heat treating the obtained substrate at ≥200°C in air or an oxidative atmosphere to form an oxide film layer 13 on the translucent film 12. The halftone phase shift mask 20 is obtained by patterning the halftone phase shift mask blank 10. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

  The present invention relates to a photomask for exposure transfer when forming a pattern in a photolithography step in a semiconductor manufacturing process, and more particularly to a phase shift photomask and a phase shift photomask blank for manufacturing the phase shift photomask. is there.

  With the recent miniaturization of semiconductor wiring patterns, the use of photomasks provided with a technology for improving resolution when transferring a pattern onto a Si wafer is becoming active. The phase shift method is one of the resolution improving techniques, and the transmitted light is diffracted by providing a phase shift portion on one side of the adjacent opening and making the phase difference between the projection lights transmitted through the adjacent pattern 180 degrees. When the light beams interfere with each other, the light intensity at the boundary is reduced, and as a result, the resolution of the transfer pattern is improved.

The phase shift method as described above is proposed by IBM's Levenson et al., And the Levenson type, the halftone type, and the like are known. In the Levenson type, a pattern is formed of a light-shielding layer, and a phase shift portion is provided on one side of an opening portion adjacent to the light-shielding pattern to invert the phase, so that the resolution performance and the depth of focus are greatly improved. (For example, see Patent Document 1 or Patent Document 2.)
In addition, a light-shielding layer that does not have complete light-shielding properties, and that allows the exposure light to pass through the translucent light-shielding layer at a resist sensitivity or lower and that inverts the phase is called a halftone type. It is possible to obtain. This case is particularly effective for improving the resolution of an isolated pattern.
JP-A-58-173744 JP-B-62-50811

  However, the halftone phase shift mask has a translucent film pattern provided on a transparent substrate, and a sufficient transfer effect cannot be obtained unless the phase difference and transmittance in the translucent film pattern region are appropriate values.

  Usually, a semi-transparent film is formed by sputtering, and a desired refractive index or extinction coefficient is obtained by adjusting the amount of an additional gas such as oxygen or nitrogen gas. In many cases, it has an intermediate composition, that is, a semi-bonded state. Therefore, optical constants such as transmittance, refractive index, and extinction coefficient are changed due to the change over time such as natural oxidation after film formation, heat treatment in the mask manufacturing process, or heat generated by absorption of exposure light at the time of exposure. It is often pointed out that the change occurs, and as a result, it is pointed out that the pattern transfer accuracy at the time of exposure is adversely affected.

  SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems, and has no change in optical constants such as transmittance, refractive index, and extinction coefficient even after a heat treatment process and a specific chemical treatment process. And a halftone type phase shift mask.

  In order to solve the above-mentioned problems in the present invention, first, in a blank for a halftone type phase shift mask in which a translucent film is formed on a transparent substrate, the outermost surface of the translucent film has an angle of 80 °. A blank for a halftone phase shift mask, characterized in that an oxide film layer having the above thickness is provided.

  According to a second aspect of the present invention, the translucent film is made of zirconium or a compound containing zirconium and silicon.

  Furthermore, in the third aspect, the oxide film layer is thermally oxidized by a heat treatment at 200 ° C. or more after the step of forming the translucent film. This is a blank for a halftone phase shift mask.

  Furthermore, according to claim 4, the oxide film layer has an element ratio of metal to oxygen of 2 or more relative to metal 1 according to any one of claims 1 to 3. Of the half-tone type phase shift mask.

  Furthermore, in claim 5, the oxide film layer is a film having a high degree of oxidation of the translucent film formed thereunder, wherein the oxide film layer is a film having a high degree of oxidation. Of the half-tone type phase shift mask.

  Furthermore, in claim 6, a halftone type phase shift mask is formed by using the blank for a halftone type phase shift mask according to any one of claims 1 to 5. This is a shift mask.

  The present invention provides a heat treatment step in a mask manufacturing process and a chemical solution by forming an oxide film layer with a thickness of 80 ° or more by heating the outermost surface of a translucent film formed on a transparent substrate. This is to suppress changes in optical constants such as transmittance of the translucent film caused by the washing step.

  Changes in optical constants such as transmittance, refractive index and extinction coefficient with respect to heat treatment and chemical treatment during the manufacturing process when manufacturing a halftone type phase shift mask using the blank for a halftone type phase shift mask of the present invention. A stable halftone type phase shift mask which does not cause a problem can be obtained.

  Furthermore, when the halftone type phase shift mask of the present invention is applied to a photolithography step in a semiconductor manufacturing process, the optical characteristics of the phase shift mask are maintained, and the pattern resolution during exposure transfer is improved. Can be planned.

  The halftone type phase shift mask blank and the halftone type phase shift mask of the present invention have a configuration as shown in FIGS. 1B and 1D, and a semitransparent film formed on a transparent substrate 11. 12 is provided with an oxide film layer 13 by heat treatment on the outermost surface thereof, whereby the transmittance and the refractive index of the translucent film pattern 12a are affected by the heat generated by the heat treatment during the mask making process or the exposure light absorption at the time of exposure. In addition, changes in optical constants such as extinction coefficient and the like can be suppressed, the optical characteristics of the phase shift mask are maintained, and the pattern resolution during exposure transfer is improved.

  First, a zirconium or zirconium compound whose refractive index, extinction coefficient and film thickness are adjusted on a transparent substrate 11 made of quartz glass by sputtering using a zirconium or zirconium silicide target in an atmosphere of nitrogen, oxygen, a halogen gas or the like. A translucent film 12 made of a film is formed (see FIG. 1A). Here, the translucent film 12 may be either a single-layer film of zirconium or a zirconium compound film or a multilayer film of two or more layers.

  Next, the transparent substrate 11 on which the translucent film 12 is formed is heated at a temperature of 200 ° C. or more in an oven or a hot plate in the air or an oxidizing atmosphere, so that the oxide film layer 13 is formed on the translucent film 12. To form a halftone type phase shift mask blank 10 of the present invention (see FIG. 1B).

  The translucent film 12 made of zirconium or a zirconium compound forms a surface oxide film layer of 50 to 80 ° by natural oxidation after film formation. However, in this state, the film is not yet stable to heat, and is not heated. By processing and thermally oxidizing, an oxide film layer of 80 ° or more is formed on the translucent film 12, and the translucent film 12 becomes a stable film. The heating temperature for thermal oxidation needs to be 200 ° C. or higher, and preferably around 250 ° C. As a result of analyzing the surface oxide film layer by ESCA, the composition ratio of metal (in this case, Zr and Si) to oxygen was 1 or more for metal and oxygen for 2 or more.

  Here, since the optical constant (particularly, transmittance) of the translucent film changes due to the heat treatment, it is necessary to design the initial optical constant of the translucent film in advance in consideration of the change due to the heat treatment.

  A resist is applied to the halftone phase shift mask blanks 10 and subjected to a series of patterning processes such as electron beam drawing, development, and baking to form a resist pattern 14 having an opening 15 (see FIG. 1C). . Further, the translucent film 12 and the oxide film layer 13 are removed by dry etching using the resist pattern 14 as a mask to form a translucent film pattern 12a and an oxide film layer pattern 13a. A halftone type phase shift mask 20 of the present invention having the pattern 16 is obtained (see FIG. 1D).

  Examples The blanks for a halftone type phase shift mask and the halftone type phase shift mask of the present invention will be described in more detail with reference to examples.

First, using a DC sputtering apparatus, an argon (Ar) gas and an oxygen (O ₂ ) gas are introduced into a chamber, and a transparent substrate made of synthetic quartz glass is subjected to reactive sputtering using a zirconium silicide (ZrSi ₂ ) target. A semi-transparent film 12 having a two-layer structure serving as a shifter was formed on 11. Film forming conditions were a gas condition when the first layer deposited _{Ar / O 2 = 28 / 2SCCM} , 2 -layer gas conditions as _Ar / O 2 = 25 / 5SCCM with power 400W. The n (refractive index) and k (extinction coefficient) of the film obtained at this time were n = 1.92 and k = 1.06 for the first layer, and n = 1 for the second layer. .95, k = 0.204.

  Next, heat treatment was performed at 250 ° C. for 1 hour in an oven to form an oxide film layer 13, thereby obtaining a halftone type phase shift mask blank 10 of the present invention.

  Next, an electron beam resist was applied on the halftone phase shift mask blanks 10 by a spinner to form a resist layer, and electron beam drawing and development were performed to form a resist pattern 14 having openings 15.

  Next, after patterning the translucent film 12 and the oxide film layer 13 by dry etching using the resist pattern 14 as a mask, the resist pattern 14 is subjected to a film removing process to form a halftone type phase shift mask 20 including the mask pattern 16. Obtained.

  The halftone phase shift mask blanks 10 and the halftone phase shift mask 20 were subjected to heat resistance and chemical resistance tests.

  Regarding heat resistance, there was no change in optical constants such as transmittance, refractive index, and extinction coefficient after heat treatment at 250 ° C. for 1 hour.

The chemical resistance test was performed according to the following procedure.
(1) Immerse in concentrated sulfuric acid at 70 ° C. for 1 hour as an acid treatment.
(2) Immerse in a 30 wt% KOH solution heated to 50 ° C. for 1 hour as an alkali treatment.
(3) As a cleaning liquid treatment, the substrate is immersed in an APM cleaning liquid (NH ₄ OH: H ₂ O ₂ : H ₂₀ = 1: 3: 5) heated to 35 ° C. for 1 hour.

  As a result of measuring the change in the spectral transmittance before and after performing the above-described processes (1) to (3), the change was less than 0.2% within the measurement wavelength range of 193 nm to 365 nm, and was a value at which there was no practical problem. there were.

  Further, for reference, heat resistance and chemical resistance tests were performed on conventional blanks and masks that were not subjected to heat treatment.

  As for the heat resistance, the transmittance of the translucent film changed by 0.4% at the wavelength of 193 nm and 1.7% at the wavelength of 248 nm by the heat treatment at 250 ° C. for 1 hour.

  In the chemical resistance test, Table 1 shows the results of measuring the rates of change in the spectral transmittance at wavelengths of 193, 248 and 365 nm before and after the treatment under the conditions (1) to (3).

表１の結果から明らかなように、アルカリ、洗浄液処理で２．４〜４．６％とかなり大きな分光透過率変化を示した。このように、本発明の実施例の方法によれば、熱処理及び薬品処理しても透過率、屈折率及び消衰係数等の光学定数が変化しない安定したハーフトーン型位相シフトマスク及びマスク用ブランクスを得ることができる。

As is clear from the results in Table 1, the treatment with alkali and the cleaning solution showed a considerably large change in spectral transmittance of 2.4 to 4.6%. As described above, according to the method of the embodiment of the present invention, a stable halftone type phase shift mask and a blank for a mask in which optical constants such as transmittance, refractive index, and extinction coefficient do not change even after heat treatment and chemical treatment. Can be obtained.

  The translucent films of the halftone type phase shift mask blanks 10 and the halftone type phase shift mask 20 of the present invention can be applied to a thin film such as chromium, a compound thereof, and molybdenum silicide in addition to a zirconium compound such as zirconium silicide.

  The present invention relates to a photomask for exposing and transferring when forming a pattern in a photolithography step in a semiconductor manufacturing process, and more particularly to a phase shift photomask and a phase shift photomask blank for manufacturing the phase shift photomask. .

(A)-(b) is typical sectional drawing which shows an example of the manufacturing method of the blank for halftone type phase shift masks of this invention in process order.

  (B) is a schematic sectional view showing a configuration of a blank for a halftone phase shift mask of the present invention.

  4C to 4D are schematic cross-sectional views illustrating an example of a method for manufacturing a halftone phase shift mask of the present invention in the order of steps.

  (D) is a schematic sectional view showing the configuration of the halftone type phase shift mask of the present invention.

Explanation of reference numerals

10 blanks for halftone phase shift mask 11 transparent substrate 12 translucent film 13 oxide film layer 14 resist pattern 15 opening 16 mask pattern 20 halftone phase Shift mask

Claims (6)

  A halftone phase shift mask blank having a translucent film formed on a transparent substrate, wherein an oxide film layer having a thickness of 80 ° or more is provided on the outermost surface of the translucent film. Blanks for shift mask.   The blank according to claim 1, wherein the translucent film is made of zirconium or a compound containing zirconium and silicon.   3. The blank for a halftone phase shift mask according to claim 1, wherein the oxide film layer is thermally oxidized by a heat treatment at 200 ° C. or higher after the step of forming the translucent film. 4.   4. The blank for a halftone phase shift mask according to claim 1, wherein the oxide film layer has an element ratio of metal to oxygen of 2 or more with respect to metal 1. 5. .   5. The blank for a halftone phase shift mask according to claim 1, wherein the oxide film layer is a film having a high degree of oxidation of the translucent film formed thereunder. .   A halftone phase shift mask, wherein a phase shift mask is formed using the blank for a halftone phase shift mask according to claim 1.

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