JPH06112107A - X-ray mask material and manufacture thereof - Google Patents

Abstract

PURPOSE:To provide an X-ray mask material capable of precisely controlling projected surface structure while maintaining the flatness of the X-ray transmission region of an X-ray transmission film. CONSTITUTION:An X-ray mask material includes a glass housing 2 having relationship, in which the sign of difference (alpha1-alpha2) between an elongation percentage alpha1 by the thermal expansion of glass and an elongation percentage alpha2 by the thermal expansion of silicon is kept at a positive value in each temperature range from room temperature to 400 deg.C, and a silicon substrate 1a, a part or the whole of the silicon surface of the silicon section of the silicon sustrate 1a with at least an X-ray transmission film 1b and the glass housing 2 are anode-joined, and the X-ray transmission film 1b is formed in a projecting shape to the glass housing 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an X-ray mask material used in X-ray lithography and a method of manufacturing the same, and more specifically, strain in an X-ray mask membrane (hereinafter sometimes referred to as in-plane strain) that affects pattern shift. ) Controlled X
The present invention relates to a line mask material and a manufacturing method thereof.

[0002]

2. Description of the Related Art Conventionally, in the semiconductor industry, a technique for forming an integrated circuit having a fine pattern on a silicon substrate or the like is a photolithography method for transferring a fine pattern by using visible light or ultraviolet light as an electromagnetic wave for exposure. Has been used. However, in recent years, along with the progress of semiconductor technology, ultra LS
High integration of semiconductor devices such as I has progressed remarkably, and with such a background, a high-precision fine pattern transfer technique exceeding the transfer limit with visible light or ultraviolet light used in the conventional photolithography method has been developed. I came to be requested. In order to transfer such a fine pattern, an X-ray lithography method using X-rays having a shorter wavelength as an electromagnetic wave for exposure has been attempted.

An X-ray mask for X-ray lithography has an X-ray transmission film and an X-ray absorption pattern, which are supported by a silicon wafer. Further, in the X-ray lithography method, the X-ray mask is subjected to various treatments such as mounting on a stepper, like the photomask in the conventional photolithography method.

In consideration of reducing the risk of mask damage during such handling and providing safety in handling, the silicon substrate is usually a glass support frame (support).
It is fixed to. When such a support frame is bonded with an adhesive, the X-ray mask has a concave structure because the tensile stress of the X-ray transparent film is dominant.

Generally, the X-ray mask in the X-ray lithography method is used in the proximity exposure method in which the pattern exposure is carried out at a minute interval of 10 to 50 μm on the photosensitive surface, and therefore a high flatness is required on the X-ray transparent film. It is said that. In order to achieve such high flatness, a relatively thick silicon wafer or a thick glass support frame is used.

[0006]

FIG. 7 shows a relationship between the X-ray mask having the concave structure according to the conventional example and the object to be exposed. In FIG. 7, the X-ray mask 27 is the X-ray transparent film 21.
An X-ray absorption film 22 having an X-ray absorption pattern, a silicon substrate 24 having an X-ray transmission hole 23, and an X-ray transmission hole 2
And a glass support frame 26 having a number 5. The exposed body 30 has a structure in which an X-ray resist film 29 is applied onto the semiconductor wafer 28.

As shown in FIG. 7, the distance between the X-ray mask 27 and the exposure target 30 in the X-ray transmission region is 10 to 50 μm.
Since it is narrower than m, if a mask having a concave surface structure as shown in FIG. 7 is used, an accident such as contact of the peripheral portion of the mask with the surface of the exposed object 30 is likely to occur when the distance is adjusted.

There is also a method of fixing the silicon substrate and the glass support frame by the anodic bonding method. This method has an advantage of being able to solve the problems of variations in the thickness of the adhesive and deterioration of the adhesive such as heat resistance and durability over time. However, the magnitude of the thermal strain generated varies depending on the material of the glass support frame and the joining conditions, and it has been difficult to precisely control the magnitude of the strain with Pyrex glass or the like that has been often used conventionally.

A first object of the present invention is to obtain an X-ray mask which maintains the flatness of the X-ray transmission region of the X-ray transmission film and does not have a risk of the peripheral portion coming into contact with the object to be exposed. An object is to provide an X-ray mask material and a manufacturing method thereof. A second object of the present invention is to use the X-ray mask material for X-ray masking.
To provide a line mask.

[0010]

The X-ray mask material of the present invention which achieves the above object has an elongation α1 due to the thermal expansion of glass and an elongation α2 due to the thermal expansion of silicon in each temperature range from room temperature to 400 ° C. And a glass support frame having a positive sign of a difference (α1-α2) with a silicon substrate, and at least a part or all of the silicon surface of the silicon part of the silicon substrate having the X-ray transparent film and the glass. The support frame is anodically bonded, and the X-ray transparent film is convex with respect to the glass support frame.

Further, in the method for producing an X-ray mask material which achieves the above object, the difference (α1) between the elongation rate α1 due to the thermal expansion of glass and the elongation rate α2 due to the thermal expansion of silicon is obtained in each temperature range from room temperature to 400 ° C. Using a glass support frame and a silicon substrate having a positive sign of -α2), at least a part or all of the silicon surface of the silicon portion of the silicon substrate having the X-ray transparent film and the glass support frame are provided. While heating the silicon substrate and the glass support frame, a voltage is applied between them to perform anodic bonding, and then the anodic-bonded silicon substrate and the glass support frame are cooled to room temperature, whereby the X It is characterized in that the line-transmissive film is convex with respect to the glass support frame.

In the above X-ray mask material and method for manufacturing the same, the ratio of the expansion rate α1 due to the thermal expansion of the glass forming the glass support frame to the expansion rate α2 due to the thermal expansion of the silicon forming the silicon substrate (α1 / α2). Is preferably greater than 1.0 and 1.2 or less in the temperature range of room temperature to 400 ° C. Further, in the method of manufacturing the X-ray mask material, it is preferable that the bonding temperature between the silicon substrate and the glass supporting frame is 170 ° C. or higher. The present invention also provides an X-ray mask obtained by using the above X-ray mask material.

[0013]

In the present invention, the difference between the expansion rate α1 of glass forming the glass support frame due to thermal expansion and the expansion rate α2 of silicon forming the silicon substrate due to thermal expansion (α1-α
Setting the sign of 2) to be positive, a glass supporting frame having a larger expansion rate due to thermal expansion than the silicon substrate is bonded to the silicon substrate by the anodic bonding method at a predetermined high temperature (for example, 170 ° C. or higher), When cooled to room temperature, the compressive stress generated by the difference in elongation during cooling causes X
An X-ray mask material in which the radiation transparent film is convex with respect to the glass support frame can be obtained with good reproducibility.

The ratio (α1 / α2) of the elongation α1 due to the thermal expansion of glass and the elongation α2 due to the thermal expansion of silicon is more than 1.0 and 1.2 or less in the temperature range from room temperature to 400 ° C. The preferable reason is that when the ratio is 1.0 or less, the X-ray mask cannot be made to have a convex shape due to the compressive stress.
This is because if it exceeds the range, the convex shape of the X-ray mask is too large, which is not preferable.

The reason why the joining temperature is preferably 170 ° C. or higher is that the joining is less likely to occur below 170 ° C. To make the bonding temperature over 400 ° C.
Since it is not practical, the preferred bonding temperature is 170-40
It is 0 ° C.

[0016]

The present invention will be described in more detail based on the following examples. Example 1 (i) FIG. 1A shows an X-ray mask membrane 1 prepared by forming a film of silicon carbide or silicon nitride as an X-ray transparent film 1b on one surface of a silicon (Si) substrate 1a. It is shown. A silicon substrate having a crystal orientation (110) was used as the silicon substrate 1a. Also, the X-ray transparent film 1
The silicon carbide film as b is formed by a CVD method using dichlorosilane and acetylene, and the silicon nitride film is formed in the same manner as the silicon carbide film except that the gas used is changed. It was done.

(Ii) In the X-ray mask membrane 1 shown in FIG. 1 (A), the surface on which the X-ray transparent film 1b is not formed is the silicon surface of the silicon substrate 1a. Before bonding to the frame, the central portion of the silicon substrate 1a was removed and the X-ray transparent film 1b was made to stand by itself as shown in FIG. 1 (B). As a method of removing the central portion of the silicon substrate 1a, for example, the surface of the silicon substrate 1a is coated with an etching resistant substance in a ring shape,
A method of dipping in a 10 to 50 wt% NaOH aqueous solution heated to 00 ° C. was used.

(Iii) In this example, 58.8 wt% of SiO ₂ was used as the glass constituting the glass support frame,
22.0 wt% of Al ₂ O _{3 and} 2.8 wt% of Na ₂ O
%, MgO 4.9 wt%, ZnO 10.0 wt%, SiO ₂ , Al ₂ O ₃ , Na ₂ O, MgO and Zn
SD-3 glass having a total content of O of 98.5 wt% and containing B ₂ O ₃ of 1.5 wt% and AS ₂ O ₃ of 0.3% was used as another oxide. Then, as shown in FIG. 1 (C), the glass support frame 2 having a hollow portion in the central portion is superposed on the X-ray mask membrane 1 composed of the silicon substrate 1a and the X-ray transparent film 1b from which the central portion is removed. I matched it. FIG. 2 shows a straight line of change in elongation rate between room temperature and 500 ° C. of SD-3 glass forming the support frame and silicon (Si) forming the substrate. From FIG. 2, the difference (α1-α2) between the elongation rate (α1) of glass and the elongation rate (α2) of silicon is almost constant at each temperature and has a positive value.

(Iv) Next, the superposed X-ray mask membrane 1 and glass support frame 2 were sandwiched by electrode plates 3a and 3b as shown in FIG. 1 (D). The electrode plate 3a used was one having a recess at the center to protect the self-standing portion of the X-ray transparent film 1b.

(V) Next, as shown in FIG. 1 (E), first, the heater 5 was used for heating through the insulating quartz plate 4, and the load 6 was used for pressurization. The device is a heat insulation cover 7.
The temperature was precisely controlled in the room. And electrode plate 3
DC voltage was applied by wiring a so that a was the positive electrode (X-ray mask membrane side) and the electrode plate 3b was the negative electrode (glass support frame side). The applied voltage at this time is, for example, 5
It can be set to 00 to 1500V. The joining temperature may be 170 to 400 ° C., for example, and the joining time may be 1 minute to 2 hours. Further, as the load applied on the electrode 3b, for example, a load of 35 to 500 g / cm ² can be applied. However, these applied voltage, junction temperature, junction time,
The load and the like are not limited to these.

When the flatness of the X-ray mask material produced in this example is evaluated by the Fizeau interferometry, it has a uniform convex structure and the flatness is 5 μm or less (the height of the peripheral portion and the central portion). Difference). Furthermore, the in-plane strain of the X-ray transmission region of the X-ray transmission film was measured by a laser length measuring device (light wave 3I), and it was confirmed that sufficient surface accuracy was obtained.

Example 2 As an X-ray mask membrane, X on both sides of a silicon substrate.
Using one that has a line-transmissive film formed, one of the X-ray transmissive films is
The central portion was removed by reactive ion etching using a mixed gas of fluorine-based gas such as CF ₄ and oxygen gas. Next, using the obtained ring-shaped X-ray transparent film as a mask, the central portion of the silicon substrate was removed by an etching process using an aqueous NaOH solution as in Example 1, and a cross section as shown in FIG. An X-ray mask membrane 1 having a shape and composed of a silicon substrate 1a and an X-ray transparent film 1b was obtained.

Next, the portion of the X-ray permeable film 1b that is to be joined to the glass support frame 2 is removed by reactive ion etching similar to that described above, and an X-ray mask membrane having a cross-sectional shape as shown in FIG. Got 1. Next, the X-ray mask membrane 1 and the glass support frame 2 were superposed on each other as shown in FIG. The glass constituting the support frame had the same composition as in Example 1. Next, the superposed X-ray mask membrane 1 and the glass support frame 2 were bonded by the anodic bonding method under the same conditions as in Example 1.

When the flatness of the X-ray mask material produced in this example was evaluated by the Fizeau interferometry, it was confirmed that it had a uniform convex structure and the flatness was 5 μm or less. Furthermore, the in-plane strain of the X-ray transmission region of the X-ray transmission film was measured by a laser length measuring device (light wave 3I), and it was confirmed that sufficient surface accuracy was obtained.

Example 3 X was formed on the X-ray transparent film of the X-ray mask material obtained in Example 1.
A tantalum film, which is a line absorption film, was formed by the RF magnetron sputtering method. X-ray absorption film thickness is 0.8 μm
Met. In this sputtering method, a tantalum target was used as the sputtering target and an argon gas was used as the sputtering gas. The atmospheric conditions in this case are as follows: Argon gas flow rate is 25cc / min in standard state,
Gas pressure during film formation is 0.5Pa, RF power is 8.64w
/ Cm ² was selected. The X-ray absorbing film formed under these film forming conditions had a weak tensile stress with an internal stress of 0 to 1 × 10 ⁸ dyn / cm ² . Next, using the resist pattern as a mask on the X-ray absorbing film having good film characteristics, reactive ion beam etching using chlorine gas is performed to form a pattern by the X-ray absorbing film, and an X-ray mask is obtained. It was

FIG. 6 shows a schematic sectional shape of the X-ray mask thus obtained. In FIG. 6, the X-ray mask 2
7 is an X-ray transmission film 25 similar to the conventional X-ray mask of FIG.
An X-ray absorption film 22 having an X-ray absorption pattern, a silicon substrate 24 having an X-ray transmission hole 23, and an X-ray transmission hole 2
And a glass support frame 26 having a number 5. The X-ray mask of the present invention shown in FIG. 6 is different from the conventional X-ray mask shown in FIG.
6 is a convex shape. Due to such a convex structure, the peripheral portion of the mask is exposed to the exposed object 3 even if the mask 30 is aligned with the exposed object 30 in the central portion (X-ray transmission region).
The advantage is that there is no risk of colliding with zero.

Next, a modification of the present invention will be shown. The present invention is shown in FIG.
As shown in (A) and FIG. 5 (A), the X-ray transparent film 1b
An X-ray mask blank having the X-ray absorbing film 8a provided thereon and an X having the X-ray absorbing film pattern 8b provided on the X-ray transmitting film 1b as shown in FIGS. 4B and 5B. It is applicable to a line mask, and a support frame can be bonded to these X-ray mask blank and X-ray mask by an anodic bonding method.

Further, in this embodiment, etching of silicon by NaOH was performed as a method of making the X-ray transparent film self-supporting, but the etching is not limited to this method, and hydrofluoric nitric acid (mixed solution of HF and HNO ₃ ) or the like is used. Can also be used.

Although the aminosilicate glass is used in the above-mentioned embodiments, it is possible to use glass having various compositions as the material for the glass supporting frame. Generally suitable glasses include alumino-silicate glass, silicate glass, borosilicate glass, borate glass, phosphate glass.

[0030]

As described above, according to the present invention, the flatness of the X-ray transmissive region of the X-ray transmissive film is maintained by defining the elongation rate of the silicon substrate and the glass support frame due to the thermal expansion. At the same time, an X-ray mask material capable of precisely controlling the convex structure with respect to the glass support frame and a method for manufacturing the same have been provided. An X-ray mask was also provided using this X-ray mask material.

Further, according to the X-ray mask material and the X-ray mask of the present invention, it is not necessary to consider the contact between the peripheral portion of the X-ray mask and the object to be exposed. The interval can be easily controlled.

[Brief description of drawings]

FIG. 1 is a manufacturing process diagram of an X-ray mask material according to a first embodiment.

FIG. 2 is a temperature change diagram of the elongation rate due to thermal expansion between the glass in the support frame and the silicon for the substrate used in Example 1.

FIG. 3 is a manufacturing process diagram of an X-ray mask material in Example 2.

FIG. 4 is a schematic view of an X-ray mask blank and an X-ray mask to which the present invention is applied.

FIG. 5 is a schematic view of an X-ray mask blank and an X-ray mask to which the present invention is applied.

6 is a schematic diagram of an X-ray mask obtained in Example 3. FIG.

FIG. 7 is a schematic view of an X-ray mask of a conventional example.

[Explanation of symbols]

 1a Silicon substrate 1b X-ray transmission film 1 X-ray mask membrane 2 Glass support frame 8a X-ray absorption film 8b X-ray absorption film pattern 21 X-ray transmission film 22 X-ray absorption film pattern 24 Silicon substrate 26 Glass support frame 27 X-ray mask

Claims (6)

[Claims] 1. A glass having a positive sign in the difference (α1-α2) between the elongation rate α1 of glass due to thermal expansion and the elongation rate α2 of silicon due to thermal expansion in each temperature range from room temperature to 400 ° C. A glass support frame is anodically bonded to a part or all of the silicon surface of the silicon part of the silicon substrate having at least an X-ray transmissive film, including a support frame and a silicon substrate, and the X-ray transmissive film is a glass support frame. An X-ray mask material having a convex shape with respect to. 2. The ratio (α1 / α2) of the elongation rate α1 due to the thermal expansion of the glass forming the glass support frame and the elongation rate α2 due to the thermal expansion of the silicon forming the silicon substrate is 1.0 at room temperature to 400 ° C. The X-ray mask material according to claim 1, which is larger than 1.2 and larger. 3. A glass having a positive sign in the difference (α1-α2) between the elongation rate α1 of glass due to thermal expansion and the elongation rate α2 of silicon due to thermal expansion in each temperature range from room temperature to 400 ° C. Using a support frame and a silicon substrate, while heating at least part or all of the silicon surface of the silicon portion of the silicon substrate having the X-ray transparent film and the glass support frame, the silicon substrate and the glass support frame,
A voltage is applied between them to perform anodic bonding, and then the silicon substrate and the glass supporting frame that have been anodically bonded are cooled to room temperature, whereby the X-ray transparent film becomes convex with respect to the glass supporting frame. X characterized in that
Method for manufacturing line mask material. 4. The ratio (α1 / α2) between the elongation rate α1 of glass forming the glass support frame due to thermal expansion and the elongation rate α2 of silicon forming the silicon substrate due to thermal expansion is 1.0 at room temperature to 400 ° C. The method for producing an X-ray mask material according to claim 3, wherein the X-ray mask material is larger than 1.2. 5. The method for producing an X-ray mask material according to claim 3, wherein the bonding temperature between the silicon substrate and the glass support frame is 170 ° C. or higher. 6. An X-ray mask using the X-ray mask material according to claim 1.