JP2880341B2 - X-ray mask manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing an X-ray mask structure having an X-ray absorber pattern to be transferred, which is used in an X-ray exposure apparatus for manufacturing semiconductors.

[0002]

2. Description of the Related Art In recent years, as the density and speed of semiconductor integrated circuits have increased, the pattern line width of the integrated circuits has increased by about 7 years.
It tends to be reduced by 0%. Due to the further integration of large-capacity memory elements, the printing apparatus is required to have higher performance, and a high performance in which the minimum transferable line width is 0.3 μm or less is beginning to be required. Therefore, the exposure wavelength X
Steppers utilizing light in the line region (2-20 °) are being developed. An X-ray mask structure used in such an X-ray exposure apparatus has conventionally been manufactured by a manufacturing method as shown in FIG. In the figure, reference numeral 51 denotes a substrate serving as a holding frame;
i-wafers are often used. The material of the X-ray transmission film 52 may be a material such as silicon nitride or silicon carbide having a high X-ray transmission property.
A thin film of about μmt is used, and gold, tungsten, tantalum, or the like having a large absorption coefficient is widely used as a material of the X-ray absorber 56. Referring to FIG. 5, a method of manufacturing a conventional X-ray mask structure will be described. First, an X-ray transmitting film 52 is formed on a substrate 51, and chromium is deposited on the substrate 51 as a metal thin film 53 for gold deposition. And gold 500 ° to be the plating electrode 54 for X-ray absorber film formation are continuously deposited by the EB deposition method (FIG. 5A). In addition, FIG.
As shown in (b), a desired fine resist pattern 55 is formed by an electron beam lithography apparatus. The resist used at this time may be a single layer or a multilayer. Next, after gold to be the X-ray absorber 56 is formed by gold plating, the resist pattern 5 is formed.
5 is peeled off (FIG. 5C). The plating electrode 54 at the portion where the X-ray absorber 56 is not provided is removed by etching using argon gas. At this time, since both the plating electrode 54 and the X-ray absorber 56 are made of gold, they are uniformly etched,
The X-ray absorber 56 'is as shown in FIG. Next, the chromium, which is the metal thin film 53 in the portion without the X-ray absorber 56 ', is peeled off by sputter etching using argon gas or using a reactive gas (chlorine gas) (FIG. 5).
(E) illustrated). Lastly, the holding frame 51 is formed by back-etching the Si wafer substrate, and an X-ray mask structure as shown in FIG.

[0003]

However, there are the following problems in the manufacturing process of the above-mentioned conventional X-ray mask structure. The difficulty in manufacturing the X-ray mask structure is that a fine pattern (0.25 μm level) is reduced to 0.75 μm.
That is, a pattern having a high aspect ratio of about μmt must be formed to obtain a high contrast. However, in the conventional manufacturing method, the chromium which is the metal thin film 53 in the portion without the X-ray absorber 56 'shown in FIG. Therefore, since the sputtering rate of chromium is low, there is a problem that the film thickness of gold is greatly reduced, and the contrast as an X-ray mask is reduced. On the other hand, forming gold in advance in consideration of the film thickness of gold which decreases during etching increases the difficulty in manufacturing. Further, in the method of stripping chromium, which is the metal thin film 53, using a reactive gas, a chlorine-based gas is used. Therefore, unlike the above case, a decrease in contrast can be prevented, but etching unevenness is slightly reduced. However, if it occurs, there is a problem that silicon nitride or silicon carbide as the X-ray transmission film is etched, causing a film thickness distribution or damaging the film surface. Note that the above-described method using the sputter etching using an argon gas also causes a film thickness distribution or damages the film surface.

Further, the presence of the metal thin film 53 remaining in the non-pattern forming portion as shown in FIG. 5D hardly affects the X-ray transmittance, but greatly reduces the alignment light transmittance. There is a problem. For example, if Cr is 50
ÅWhen the residual, the X-ray transmittance is reduced by only 0.6%, but the alignment light transmittance (He-Ne laser)
Is reduced by 46%. Further, as a method of manufacturing the X-ray absorber, there is a method of forming W or Ta by etching. However, a reactive gas (mainly a fluorine-based gas) must be used. Since W and Ta have lower etching rates than silicon nitride and silicon carbide, which are permeable films, there is a problem that the film thickness distribution is caused or the film surface is damaged. For this reason, a metal thin film for an etching stopper is provided. According to this method, a thin film thickness distribution and a small amount of damage can be small, but the same problem is caused although the degree is different. Occur.

Accordingly, an object of the present invention is to solve the above-mentioned problems of the prior art, and to provide a metal thin film between an X-ray transmitting film and a metal which plays a major role as an X-ray absorber. To provide an X-ray mask that does not reduce the thickness, does not cause the thickness distribution and damage of the X-ray transmission film, and does not hinder the alignment light transmittance in the non-pattern forming portion of the metal thin film. is there.

[0006]

The above object is achieved by the present invention described below. That is, the present invention provides a method for manufacturing an X-ray mask having a metal thin film between an X-ray transmitting film provided on a holding frame and a metal serving as an X-ray absorber provided on the X-ray transmitting film. In the method, after forming a metal which plays a main role as an X-ray absorber in a desired pattern, only a non-pattern forming portion of the metal thin film is oxidized to make the portion a metal oxide. This is a line mask manufacturing method.

[0007]

The present inventors have conducted intensive studies to solve the above-mentioned object. As a result, in a method of manufacturing an X-ray mask structure, after forming a metal which plays a main role as an X-ray absorber in a desired pattern, the X-ray mask is formed. If the metal thin film between the permeable film and the metal is oxidized, and only the non-pattern forming portion of the metal thin film is made of metal oxide, without reducing the X-ray absorber,
In addition, the present inventors have found that an X-ray mask structure that does not cause the film thickness distribution or damage of the X-ray transmission film is formed, and have reached the present invention. Furthermore, according to the method of the present invention, it has been found that the non-patterned portion of the oxidized metal thin film does not hinder the alignment light transmittance. For example, if a 50 ° Cr film is oxidized with oxygen plasma to make only the non-pattern formed portion a chromium oxide, depending on the alignment light used, when a He-Ne laser (6328 °) is used, the alignment light is transmitted. It is possible to manufacture an X-ray mask structure in which the rate is reduced by only 0.5%.

[0008]

Next, the present invention will be described in detail with reference to preferred embodiments. The method of manufacturing the X-ray mask structure of the present invention is performed substantially in accordance with a conventional method. However, after forming a metal which plays a major role as an X-ray absorber in a desired pattern, the X-ray transmitting film and the X-ray The present invention is characterized in that only a non-pattern forming portion of a metal thin film is made of a metal oxide by oxidizing a metal thin film provided between the transmission film and a metal which plays a main role as an X-ray absorber. As a method of oxidizing the metal thin film used in the method of the present invention, any method such as an oxygen plasma treatment, an oxygen ion implantation treatment, and a heat treatment in an oxygen atmosphere is preferably used. or,
As the metal thin film provided between the X-ray transmission film and the metal which plays a main role as an X-ray absorber on the X-ray transmission film used in the method of the present invention, the metal oxide in the state of a thin film is Any metal may be used depending on the application as long as it has high visible or infrared transmittance used for alignment. Generally, chromium, titanium, tantalum, aluminum, tungsten, molybdenum, tin,
Metals such as zinc, copper, lead and nickel are preferably used. The thickness of the metal thin film depends on its use, but is preferably 1000 ° or less, preferably 100 ° or less so as not to significantly reduce the X-ray transmittance. Since such a metal thin film hardly affects the X-ray transmittance,
Even if it remains, there is no problem in this regard. In addition, if the metal thin film is oxidized, the alignment light transmittance will not be reduced. There is no problem of hindering light transmittance.

[0009]

Embodiments of the present invention will be described below with reference to the drawings, and the present invention will be further described in detail. Embodiment 1 FIG. 1 is a cross-sectional view showing a manufacturing process of a method for manufacturing an X-ray mask structure according to a first embodiment of the present invention. In the figure, reference numeral 11 denotes a substrate 11 serving as a holding frame.
i-wafer was used. Such a substrate 11 is subjected to plasma CV
Set it on the D device. First, the back pressure was set to 2 × 10 ^-6 Torr
Silane gas diluted to 10% with hydrogen
A mixed gas of sccm and 20 sccm of ammonia gas was supplied from a hole formed in the lower electrode. Next, the substrate 11
Was heated to 250 ° C., a high frequency power of 20 W was applied at a pressure of 5 × 10 ⁻³ Torr, and silicon nitride was formed on a 2 μmt substrate to form an X-ray transmission film 12. Further on this,
500 金 of gold to be the plating electrode 14 for X-ray absorber film formation
And chromium 50 °, which is the metal thin film 13 for deposition, were continuously EB-deposited (FIG. 1A). The metal thin film 13 may be made of any metal other than chromium, such as Ti, Ta, A1, Sn, and Zn, as long as the metal can improve the adhesive force. Next, as shown in FIG. 1B, an electron beam resist PMMA (OEBR-1000, manufactured by Tokyo Ohka) is applied on the metal thin film 13 and a desired fine resist pattern is formed by an electron beam drawing apparatus. 15 are formed. Next, FIG.
As shown in (c), plating is performed under the conditions of 50 ° C. and current density of 1 mA / cm ² using a gold sulfite plating solution (Neutronex 309 trade name: manufactured by EEJA), and the X-ray absorber 16 is obtained. After gold is formed, the resist pattern 15 is peeled off using a dedicated peeling liquid. Next, the above X-ray absorber 16
Peeling of the plating electrode 14 in the portion without the pit is performed using an RIE apparatus. The condition at this time is that the back pressure is 1 × 10 ⁻⁵ T
After pulling down to orr, etching is performed by flowing 20 sccm of argon gas and applying 200 W at 5 × 10 ⁻² Torr. As a result, as shown in FIG. 1D, since both the plating electrode 14 and the X-ray absorber 16 are made of gold, both are uniformly etched, and the X-ray absorber 16 'is shown in FIG. It becomes like. Next, oxygen gas 20 s was set in the same RIE device.
ccm, 130 W is applied at 5 × 10 ⁻² Torr,
The non-pattern forming portion of the metal thin film 13 is oxidized by oxygen plasma, and only this portion is changed to the chromium oxide 17 as shown in FIG. Finally, the Si wafer serving as the substrate 11 is subjected to a 110 wt.
Back etching is performed under the condition of ° C. to form the holding frame 11 (FIG. 1F).

[0010] In the manufacturing process of the method of the present invention as described above,
The film 17 obtained by oxidizing the metal thin film 13 in FIG.
Was analyzed by ESCA to confirm that it was chromium oxide. That is, the following four types of films including the comparative sample were measured, and the resulting Cr
FIG. 2 is a chart showing the positions where the peaks appear. A film 17 obtained by oxidizing the metal thin film 13 in FIG. The metal thin film 13 (the plating electrode 14) in FIG.
(Non-processed silicon nitride 12). The metal thin film 53 in the conventional manufacturing method of FIG.
Silicon nitride film 52 after stripping. As a result, as shown in FIG. 2, no Cr peak is observed in the untreated silicon nitride film 12. Metal thin film 5
A small peak appears at the same position as in the silicon nitride film 52 after stripping No. 3, indicating that Cr remains. Actually, since the measurement is performed after the sample is once put into the air, the Cr on the surface is slightly oxidized. Compared to these two films, the film 17 obtained by oxidizing the metal thin film 13 has a peak shifted to a higher energy side, indicating that chromium is further oxidized. or,
Although the light transmittances of the film 17 and the film 52 are almost the same, the same peaks of Si as the film 12 of the film 52 alone are observed in the ESCA measurement result (not shown). From the above, it is confirmed that the film 17 is not peeled off like the film but the chromium oxide remains. As described above, according to the method of the present invention, chromium as an adhering metal is oxidized without being stripped, so that X
It is also possible to prevent a decrease in the film thickness of gold as the line absorber 16 'and the occurrence of a film thickness distribution of silicon nitride as the X-ray transparent film.
In addition, the presence of the chromium oxide 17 in the non-pattern portion only reduced the X-ray transmittance by 0.6% and the transmittance of the He-Ne laser (6328 °) used for alignment by 1.5%. There is no problem in point.

Embodiment 2 FIG. 3 is a sectional view showing a manufacturing process of an X-ray mask structure manufacturing method according to a second embodiment of the present invention. The substrate 31 has 3
A 1 mmt Si wafer with an inch φ was used. After setting such a substrate 31 in a plasma CVD apparatus, first, a back pressure was reduced to 1 × 10 ⁻⁶ Torr, and then 10 sccm of silane gas and 10 sccm of methane gas diluted to 10% with hydrogen.
cm of gas was supplied from a hole formed in the lower electrode. Next, the temperature of the substrate 21 is heated to 650 ° C., a high frequency power of 50 W is applied at a pressure of 5 × 10 ⁻³ Torr, silicon carbide is formed on the 2 μmt substrate 31, and the X-ray transmission film 32 is formed.
And This was set in a binary sputtering device, and the back pressure was set to 2
After pulling down to × 10 ^-6 Torr, argon gas was supplied for 10 seconds.
ccm, pressure 10 × 10 ^-2 Torr, substrate temperature 15
By applying a high-frequency power of 100 W at 0 ° C., the chromium to be the metal thin film 33 for the absorber etching stopper is removed by 200 μm.
The film was formed to a thickness of Å. Further, by continuously applying 500 W, 800 W of tungsten (W) serving as the X-ray absorber 36 is applied.
A film was formed to a thickness of 0 ° (FIG. 3A). Next, FIG.
As shown in (b), the Si wafer as the substrate 31 is
Back etching is performed at 110 ° C. using a 30 wt% potassium hydroxide solution to form a holding frame 31. On top of that, as shown in FIG.
IQ (trade name: manufactured by Hitachi Chemical) and an upper layer Si-containing resist SNR (trade name: manufactured by Toyo Soda) are applied, respectively.
A desired fine resist pattern 35 is formed by an electron beam drawing apparatus and an RIE apparatus. Next, W which becomes the X-ray absorber 36
Is performed by an RIE apparatus. The conditions at this time are as follows: after the back pressure is reduced to 1 × 10 ⁻⁵ Torr, CF ₄
Flow 50 sccm of gas and 200 at 5 × 10 ^-2 Torr.
W is applied and W is etched. At this time, chrome is C
F without damage because it is not substantially etched in ₄ gas, X-rays absorber 36 'is as shown in FIG. 3 (d). The resist pattern 35 is simultaneously etched during the etching of W, but the remaining one is peeled off with a dedicated peeling liquid. Further, as shown in FIG. 3E, the oxygen ion concentration is 10 ¹⁶ to 10 ¹⁷ io in the ion implantation apparatus.
ns / cm ² , and an acceleration voltage of 10 to 20 KV.
7 is assumed. If an ion implantation apparatus is used, even a relatively thick film can be oxidized by selecting an appropriate ion concentration and an acceleration voltage. Therefore, a metal thin film may be formed so that chromium oxide has a thickness (for example, 630 ° for a He—Ne laser) serving as an antireflection film. As described above, according to the method of the present invention, the chromium metal thin film 33, which is an etching stopper, is oxidized without being stripped to form the oxide film 37.
2, which prevented the occurrence of the silicon carbide film thickness distribution. Further, due to the presence of the chromium oxide film 37 in the non-pattern portion, the X-ray transmittance is 2.3%, and He used for alignment is used.
The transmittance of the -Ne laser (6328 [deg.]) Was only reduced by 5.0%, and there was no problem with this.

Embodiment 3 FIG. 4 is a sectional view showing a manufacturing process of an X-ray mask structure manufacturing method according to a third embodiment of the present invention. The substrate 41 has 3
A 2 mmt Si wafer with an inch φ was used. Such a substrate 41 is set in a plasma CVD apparatus. First, a back pressure is reduced to 2 × 10 ⁻⁶ Torr, and then 5 sccm of silane gas diluted to 10% with hydrogen and 20% of ammonia gas
A mixed gas with sccm was supplied from a hole formed in the lower electrode. Next, the temperature of the substrate 41 was heated to 250 ° C., and a high frequency power of 20 W was applied at a pressure of 5 × 10 ⁻³ Torr,
An X-ray transmitting film 42 was formed on the substrate 41 by forming silicon nitride to a thickness of 2 μm. Next, as shown in FIG.
Is etched back at 110 ° C. using a 30 wt% potassium hydroxide solution to form a holding frame 41.
To form Next, as shown in FIG. 4 (b), gold to be the plating electrode 44 for forming the X-ray absorber was formed to a thickness of 500.degree. Continuous evaporation by evaporation. In addition, FIG.
As shown in the figure, the electron beam resist PMMA (OEBR-1)
000 (trade name: manufactured by Tokyo Ohka), and a desired fine resist pattern 45 is formed by an electron beam drawing apparatus. Next, as shown in FIG. 4 (d), using a gold sulfite plating solution (Neutronex 309 trade name: manufactured by EEJA), 50
Plating was performed at a sub-flow density of 0.5 mA / cm ² at a temperature of 0 ° C. to form gold to be the X-ray absorber 46, and the resist pattern 45 was peeled off with a dedicated peeling liquid. Next, the X-ray absorber 4
The plating electrode 44 in the portion without 6 is peeled off by the RIE apparatus. The conditions at this time were as follows: after reducing the back pressure to 1 × 10 ⁻⁵ Torr, flowing argon gas at 20 sccm,
Etching is performed by applying 200 W at 0 ^-2 Torr. Since both the plating electrode 44 and the X-ray absorber are made of gold, both are etched uniformly, and the X-ray absorber becomes as shown at 46 'in FIG. Next, as shown in FIG. 4F, a heat treatment is performed at 100 ° C. in an oxygen atmosphere, and the non-pattern forming portion of the metal thin film 43 is made to be a titanium oxide film 47. As described above, according to the method of the present invention, by oxidizing titanium, which is the deposited metal thin film 43, without stripping, the thickness of the gold, which is the X-ray absorber 46 ', is reduced, and the nitriding, which is the X-ray transmitting film, is reduced. The generation of the silicon film thickness distribution was prevented. Further, due to the presence of the titanium oxide 47 in the non-pattern portion, the X-ray transmittance was 0.3%,
He-Ne laser (6328) used for alignment
The transmittance of Å) was only reduced by 1.0%, respectively, and there was no problem at all.

[0013]

As described above, according to the method of manufacturing an X-ray mask structure of the present invention, after forming a metal which plays a major role as an X-ray absorber in a desired pattern, the X-ray transmitting film and the X-ray mask are formed.
By oxidizing the metal thin film provided between the metal that plays the main role as an X-ray absorber on the X-ray transparent film and forming only the non-pattern forming portion of the metal thin film with the metal oxide,
An X-ray mask structure having excellent characteristics without reducing the X-ray absorber, causing no damage to the film thickness distribution and surface of the X-ray transmission film, and without causing a decrease in contrast and the like is provided. Further, according to the method of the present invention, since the non-pattern forming portion of the metal thin film is oxidized as described above, an X-ray mask structure which does not hinder the alignment light transmittance is provided.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a manufacturing process of the method of the present invention.

FIG. 2 is a graph showing measured values of ESCA.

FIG. 3 is a cross-sectional view showing a manufacturing process of another embodiment of the method of the present invention.

FIG. 4 is a cross-sectional view showing a manufacturing process of another embodiment of the method of the present invention.

FIG. 5 is a cross-sectional view showing a manufacturing step of a conventional method for manufacturing an X-ray mask structure.

[Explanation of symbols]

 11, 31, 41, 51: Substrate (holding frame) 12, 32, 42, 52: X-ray permeable film 13, 33, 43, 53: Metal thin film 14, 44, 54: Plating electrode 15, 35, 45, 55 : Resist 16, 36, 46, 56: X-ray absorber 16 ', 36', 46 ', 56': X-ray absorber after processing 17, 37, 47: Metal oxide

Claims (4)

(57) [Claims] 1. A method of manufacturing an X-ray mask having a metal thin film between an X-ray transmitting film provided on a holding frame and a metal serving as an X-ray absorber provided on the X-ray transmitting film. In the above, after forming a metal which plays a main role as an X-ray absorber in a desired pattern, only a non-pattern forming portion of the metal thin film is oxidized to make the portion a metal oxide. Mask manufacturing method. 2. The X-ray mask manufacturing method according to claim 1, wherein the oxidation treatment of the non-pattern forming portion of the metal thin film is an oxygen plasma treatment. 3. The method of manufacturing an X-ray mask according to claim 1, wherein the oxidation treatment of the non-pattern forming portion of the metal thin film is an oxygen ion implantation treatment. 4. The method of manufacturing an X-ray mask according to claim 1, wherein the oxidation treatment of the non-pattern forming portion of the metal thin film is a heat treatment in an oxygen atmosphere.