JP2004335996A - Mask structure, its manufacturing method, and reinforcing mask frame - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide configurations of a mask substrate and a reinforcing mask frame with which a mask distortion is reduced, breakage in handling the mask substrate is prevented, and which is effective in shortening the time required for alignment. <P>SOLUTION: In a mask structure which is constituted by uniting the mask substrate and the mask frame with a bonding layer between, the mask substrate and the mask frame are bonded with a thin film bonding layer whose thickness is 0.5-10 μm. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a mask structure used in an exposure apparatus using a radiation beam such as an X-ray or an electron beam used in the manufacture of a semiconductor, a method of manufacturing the same, and a mask frame for reinforcement, and more particularly to an electron lithography processing method. And a reinforcing mask frame integrally joined thereto.

Conventionally, a mask substrate used for lithography processing using a radiation beam such as an X-ray, an electron beam, and UV, and a reinforcing mask frame thereof are made of Si, SiC, SiN or the like is used. In addition, the shape of the mask is generally polygonal, and the opening provided in the center is generally rectangular. The mask frame and the mask substrate are usually bonded by anodic bonding. The anodic bonding is a technique in which atoms are diffused and bonded by applying a voltage at the same time as the objects to be bonded are superimposed and heated, and is a bonding method in which an adhesive layer is not interposed.
As another bonding method, there is a method of realizing the bonding between the mask substrate and the mask frame by using a eutectic alloy layer as disclosed in Patent Documents 2 and 3.

  In general, such a mask structure includes, as described in Patent Document 4, a mask substrate provided with a rectangular window in which a mask pattern is formed, and a circular outer shape in which a thin portion having a step is formed around the mask substrate. The configuration having a mask frame is the most common.

: JP-A-7-307285 : JP-A-5-283323 : JP-A-2000-150337 : JP-A-10-24203

However, the mask structures disclosed in Patent Literatures 1 to 4 have a problem in that when anodic bonding or eutectic bonding is performed, the mask is distorted and lithography accuracy is reduced. In addition, the mask structure is made to approach the wafer at the time of exposure and is separated from the wafer again after the end of the exposure. At this time, since the vertical movement is repeated (handling), there is a problem that a crack is easily generated in the mask. . Further, in addition to these problems, the conventional mask frame 1 has a circular outer shape, as shown in FIG. However, there is also a problem that the concentration of stress (mask distortion) tends to occur at the corners due to the rectangular shape, and the mask substrate 3 is easily damaged.

  SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art, and particularly to a mask effective for reducing mask distortion, preventing damage during handling of a mask substrate, and shortening the time required for alignment. It is to propose a configuration of a substrate and a mask frame. That is, the present invention is characterized in that the two effects of increasing the alignment accuracy and preventing damage to the mask substrate are realized without sacrificing each other.

In order to achieve the above object, the present invention proposes a mask structure according to the following gist configuration. That is, the present invention
(1) In a mask structure in which a mask substrate and a mask frame are integrated via a bonding layer, it is required that the mask substrate and the mask frame are bonded by a thin film bonding layer having a thickness of 0.5 to 10 μm. A mask structure,
(2) A mask structure obtained by directly joining a mask substrate and a mask frame by an anodic bonding method or the like, wherein the mask substrate and the mask frame have a thickness ratio of 0.2 or less. ,
(3) In a mask structure obtained by integrally joining a mask substrate and a mask frame via a joining layer, the mask frame has a polygonal outer shape, and has a circular opening in the center. Mask structure,
(4) In a mask structure obtained by integrating a mask substrate and a mask frame via a bonding layer, the mask substrate and the mask frame are both made of silicon, and the bonding layer is made of an alloy of gold and silicon. A mask structure, wherein the mask substrate and the mask frame are bonded by a thin film bonding layer having a thickness of 0.5 to 10 μm,
Suggest.

  In the present invention according to the above summary, it is preferable that a thickness ratio (maximum thickness of the mask substrate / mask frame) between the mask substrate and the mask frame is 0.2 or less, and the mask frame has a polygonal outer shape. Preferably, the central portion has a circular opening, and the mask substrate and the mask frame are preferably made of any one of silicon, carbon, oxide ceramic, carbide ceramic or nitride ceramic. The layer is made of an Au brazing material, and is preferably a thin film bonding layer made of an active metal layer, a coating layer, and a brazing material layer.

Further, the present invention provides a mask substrate and a mask frame, which are directly formed by an anodic bonding method or a bonding layer formed of a brazing material made of gold and silicon and having a high relative content (weight ratio) of gold at the same time. A method for manufacturing a mask structure, comprising: applying a load of 4 MPa or more in an atmosphere having an oxygen concentration of 500 ppm or less and heating to a temperature of eutectic temperature (365 ° C.) to 500 ° C. suggest.
In this manufacturing method, it is preferable that both the mask substrate and the mask frame are made of silicon, and that a eutectic alloy of silicon and gold is used as the bonding layer.

  The present invention also proposes a reinforcing mask frame having a polygonal outer shape and a circular opening in the center. The mask frame is preferably made of any one of silicon, carbon, oxide ceramic, carbide ceramic and nitride ceramic.

  As described above, according to the mask frame and mask structure for electron beam lithography of the present invention, distortion of the mask can be reduced, alignment time can be reduced, and the life of the mask substrate can be extended. Further, the alignment accuracy and the prevention of damage to the mask substrate can be achieved at the same time.

  The present invention proposes a novel structure of a mask structure, a method of manufacturing the same, and a reinforcing mask frame constituting the mask structure. First, as described above, the mask frame has a polygonal outer shape, has a circular opening at the center thereof, and is integrally bonded to one surface of the mask substrate via a bonding layer, and is then subjected to electron beam lithography. It is used as a component for forming a mask structure for e-processing. Hereinafter, the detailed structure of the mask frame will be described.

  In the reinforcing mask frame according to the present invention, the outer shape (the shape of the outer peripheral portion) is a polygon. However, since each side constituting the polygon is a straight line, a linear portion constituting each side is used. This makes it easier to perform positioning with respect to the jig and the rail, thereby improving the positioning accuracy.

  When pressing each side of the mask frame against a jig or a rail in the above alignment, if the opening 5 is rectangular, stress is concentrated on the corner of the opening 5 and damages the mask. There is. Therefore, in the present invention, in order to overcome such a problem, the opening 5 is made circular. By making the shape circular, the above-mentioned concentration of stress can be avoided, and damage to the mask is greatly reduced.

  As described above, the mask frame according to the present invention is directly or integrally bonded to the mask substrate via the bonding layer. In the case of direct joining, joining is performed by an anodic joining method of joining while applying a DC voltage in an electric furnace. When a bonding layer is interposed, it is effective that the thickness of the bonding layer 2 is about 0.5 to 10 μm. By interposing the bonding layer having such a thickness, the mask is distorted by the mask frame. Can be reliably corrected, and the bonding between the mask substrate and the mask frame is strengthened, and the durability of the mask structure is improved.

  When the thickness of the bonding layer is 0.5 to 10 μm, it is not clear why the distortion of the mask substrate 300 can be reduced, but if the thickness is too small (less than 0.5 μm), the unevenness of the frame is reflected. It is thought that it is. On the other hand, if it exceeds 10 μm, it is presumed that the mask substrate 300 is distorted due to variations in the thickness of the bonding layer itself.

  FIG. 6 shows the relationship between the thickness of the bonding layer and the flatness (an index indicating the degree of distortion; the larger the numerical value, the larger the amount of distortion). When the thickness of the bonding layer is 0.5 to 10 μm, the flatness (distortion) is small, preferably 1 to 5 μm, more preferably 2 to 4 μm, and particularly when the thickness is 3 to 4 μm, the amount of distortion may be extremely small. Understand.

Further, the mask frame 1 according to the present invention preferably has a thickness ratio with respect to the mask substrate 300 (maximum thickness of the mask substrate / mask frame thickness) of 0.2 or less. The reason is that if the maximum thickness of the mask substrate / the mask frame> 0.2, the mask substrate 300 itself tends to be distorted, and the distortion of the mask substrate 300 cannot be corrected by the mask frame 1. .
The maximum thickness of the mask substrate refers to the maximum thickness in the configuration including the mask 3 and the membrane 4.

Next, the configuration of the mask structure according to the present invention will be described in detail with reference to the drawings. It should be noted that the present invention is not construed as being limited to only the embodiments exemplified below.
FIG. 1 shows the entire mask structure 100 of the present invention. The mask structure 100 is formed by joining a mask substrate 300 including a mask 3 and a membrane 4 and a reinforcing mask frame 1 directly or via a thin film joining layer.

  As shown in FIG. 2, the mask frame 1 used in the present invention preferably has a polygonal shape such as a quadrangle and a circular opening 5 formed in the center. The thickness of the mask frame 1 is desirably about 3.0 to 10.0 mm, preferably about 3 to 7 mm. The reason is that if the thickness is less than 3.0 mm, the reinforcing effect is small because the thickness is too small, and if the thickness is more than 10.0 mm, the mask substrate 300 is deformed by the weight of the mask frame.

  The mask frame 1 can be entirely circular. However, in the present invention, a linear portion is provided on the outer peripheral side surface, and the mask frame 1 is formed in a polygonal shape in order to facilitate alignment by the presence of the linear portion. It is desirable. For example, as shown in FIG. 3, a pentagon, a hexagon, an octagon and the like are preferable. On the other hand, the opening 5 provided at the center thereof may be not only a perfect circle but also an ellipse in order to suppress concentration of stress and effectively prevent damage to the mask substrate.

  The mask frame 1 has a uniform thickness as a whole as shown in FIG. 3 (b) and a thinner outer peripheral side as shown in FIG. 3 (a). In other words, a structure in which a step or a protrusion is provided on the outer peripheral portion may be used. In the present invention, by providing such protrusions and steps on the mask frame, that is, by applying the chuck hook of the transfer device to the protrusions and steps, the transfer of the mask structure can be facilitated.

  The longest diagonal line of the mask frame 1 is desirably about 150 mm to 350 mm. If it is too small (<150 mm), the size of the opening will be relatively too large, and the original function as the mask frame 1 will be reduced. Conversely, if it is too large (> 350 mm), it will bend and be reinforced. The effect as a mask frame is destroyed.

  As a material used for the mask frame 1, a ceramic having a coefficient of thermal expansion close to that of silicon can be used. For example, low thermal expansion ceramics such as silicon, carbon, and glass; carbide ceramics such as silicon carbide, tungsten carbide and molybdenum carbide; nitride ceramics such as silicon nitride and aluminum nitride; and oxide ceramics such as alumina can be given. . Among them, silicon and silicon carbide are preferable. This is because the coefficient of thermal expansion is relatively close to that of silicon.

  Next, it is desirable that the mask 3 has a thickness of about 0.6 to 0.8 mm. If the thickness of the mask 3 is too thin (<0.6 mm), the pattern is easily deformed, and the pattern is distorted. On the other hand, if the mask 3 is too thick (> 0.8 mm), the pattern is bent by its own weight, and the pattern is also distorted.

  A membrane 4 is formed on the surface of the mask 3 (the side opposite to the mask frame side), and the membrane 4 is provided with a pattern to be transferred to a silicon wafer by photolithography.

  In one embodiment of the mask substrate 300 including the mask 3 and the membrane 4, it is preferable that the whole of the mask substrate 300 is basically made of silicon. This is because it is effective for matching the thermal expansion coefficient with the silicon wafer. Before the mask substrate 300 is bonded to the mask frame 1, the stencil (perforated) pattern may be formed on the membrane, or the mask substrate 300 may be in a blank state.

  The membrane 4 is made of a silicon, silicon nitride, silicon carbide film or the like, and is formed by a thin film forming technique such as a CVD method. It is preferable that the thickness of the membrane 4 is about 0.2 to 4 μm, and the opening diameter (the long diameter in the case of an ellipse) is about 70 to 120 mm. The reason is that if the opening diameter is too large, it becomes easy to bend, the dimensional accuracy of the formed pattern is reduced, and even if the opening diameter is too small, it is still formed under the influence of the warping of the reinforcing frame and the bending. Pattern dimensional accuracy decreases.

  In the present invention, as the thin film bonding layer 2 used for connecting the mask substrate 300, particularly the mask 3 and the mask frame 1, it is preferable to use a brazing material, and particularly preferable to use Au brazing material. This is because eutectic alloys are easily formed with silicon (Si) and have excellent adhesive strength. In addition, since the Au solder has corrosion resistance, it is advantageous in preventing contamination of the cleaning liquid in the cleaning process of the mask structure. The Au braze has, for example, an alloy having a component composition selected from Au: 80 wt% -Sn: 20 wt%, Au: 88 wt% -Ge: 12 wt%, Au: 96.85 wt% -Si: 3.15 wt%. Is desirable. This is because these alloys melt at low temperatures and do not induce distortion of the mask substrate.

  Preferably, an active metal layer (Ti and / or Cr) serving as an adhesion underlayer and / or a coating layer of Pt are formed on the surface of the mask 3 on the side in contact with the thin film bonding layer (brazing material) 2. preferable. This is because it is effective to further improve the joining characteristics of the brazing material (eutectic metal joining material of Au).

  Further, as one of more preferred embodiments of the present invention, in a mask structure in which a mask substrate 300 and a mask frame 1 are integrated via the thin film bonding layer 2, the mask substrate 300 and the mask frame 1 are combined. Both are made of silicon, and the thin film bonding layer 2 is also made of an alloy of gold and silicon. Also in this case, the mask substrate and the mask frame are bonded by the thin film bonding layer 2 having a thickness of 0.5 to 10 μm.

Generally, the peeling phenomenon between the mask substrate 300 and the mask frame 1 is caused by the peeling of the interface between the mask substrate and the mask frame or the destruction of the thin film bonding layer (brazing material) itself.
In the present invention, silicon is used as a material for both the mask substrate and the mask frame, and when a gold-silicon alloy is used as a brazing material as a bonding layer, gold in the brazing material diffuses into the silicon of the base material and the frame. Then, a eutectic alloy is formed to form a strong bonding layer to prevent interface delamination, and that gold diffuses toward the silicon base material, thereby increasing the relative concentration of silicon in the bonding layer (brazing material). Thereby, the strength of the bonding layer is increased, and the destruction of the bonding layer itself can be prevented. As a result, the peeling of the interface between the mask substrate and the mask frame and the destruction of the thin film bonding layer (brazing material, alloy) can be prevented at the same time. .

  The thickness of the thin film bonding layer is set to about 0.5 μm to 10 μm. The reason is that if the thickness is less than 0.5 μm, a desired bonding strength cannot be secured. This is because stress is easily applied to the bonding layer and the bonding layer itself is easily broken. When the thickness is within this range, the distortion of the mask 3 is effectively corrected by the mask frame.

Next, in manufacturing the mask structure according to the present invention, for example, between the mask substrate made of silicon and the mask frame made of silicon, for example, the relative content of gold (weight ratio ≧ 96 wt%) is large. A brazing material made of a gold-silicon alloy is interposed as a thin film bonding layer, a load of 4 MPa or more is applied in an atmosphere having an oxygen concentration of 500 ppm or less, and the material is heated at a temperature of eutectic temperature (365 ° C.) to 500 ° C. It is preferable to join.
In addition, as a brazing material made of a eutectic alloy of gold and silicon having a relatively large gold content, for example, a brazing material containing more than 50 wt% to 93 wt% of gold is preferable, and in particular, 90 wt% Au-10 wt% Si Those having a composition of 98 wt% Au-2 wt% Si have a low liquidus temperature of the alloy, and gold is easily diffused into a base material or a mask frame, and is suitably used.

The reason why the oxygen concentration in the heat treatment atmosphere at the time of the bonding is 500 ppm or less is to prevent the surface of the silicon base material and the silicon mask frame from being oxidized to inhibit diffusion. The reason why a load of 4 MPa or more is applied during this treatment is that the diffusion of Au can be assisted. That is, by performing the pressure heating treatment as described above at a temperature higher than the eutectic temperature (6 wt% Si-Au: 365 ° C.), the liquid phase of the alloy is easily formed, while the temperature is limited to 500 ° C. or less. To prevent gold and silicon elements from scattering in the gas phase.
In the present invention, elements other than gold and silicon are not contained in the brazing material except for unavoidable impurities in principle, but this is because the strength of the bonding layer itself tends to decrease. .

In the present invention, in a mask structure in which a mask substrate and a mask frame are integrated via a bonding layer, the mask substrate and the mask frame are both made of silicon, and the thin film bonding layer 2 is also made of gold. And a eutectic alloy of silicon, wherein the mask substrate and the mask frame are bonded by a thin film bonding layer having a thickness of 0.5 to 10 μm. This reason is explained as follows.
Peeling and destruction of the mask substrate and the mask frame are caused by delamination of the interface between the mask substrate and the mask frame or destruction of the thin film bonding layer (brazing material, alloy) itself. In the present invention, silicon is used for both the mask substrate and the mask frame, and an alloy of gold and silicon is adopted as the bonding layer. Therefore, gold diffuses into the silicon of the substrate and the mask frame, and at the boundary thereof, In order to form the eutectic alloy, it is possible to control the separation of the interface between the substrate and the frame, and at the same time, the diffusion of gold from the brazing material (thin film bonding layer) into the silicon allows the silicon relative to the thin film bonding layer to be removed. Since the concentration is increased, the strength of the thin film bonding layer itself is significantly improved and increased, and as a result, not only the boundary between the substrate and the frame but also the portion of the thin film bonding layer can be prevented, and the mask substrate and the The bonding strength of the entire mask frame is improved.

Next, a method of manufacturing the mask structure 100 will be described with reference to FIG.
(1) First, a mask frame 1 is prepared. In the case of a carbide ceramic, a nitride ceramic, or an oxide ceramic, the mask frame 1 is manufactured together with the openings by firing these ceramic powders. On the other hand, when silicon is used as the mask frame, the opening is formed by etching with an alkaline aqueous solution or by a dry etching method such as ion beam etching.

(2) The mask frame 1 manufactured as described above is polished at the joint surface with the mask 3 and adjusted to have a flatness of 2 μm or less, preferably about 1 μm by polishing. Then, at least one metal selected from Ti, Cr, Pt, and Ni as an active metal is formed on the bonding surface side of the mask 3 by a sputtering method. Among these metals, Ti and Cr have the effect of improving the bondability between the mask 3 and the Au brazing material 2, while Pt and Ni have the effect of preventing the brazing material from diffusing into the active metal layer. Have. Desirably, an Au brazing material is further formed on these active metal layers by a PVD method such as sputtering. As a thin film forming apparatus used for such a PVD method, a DC and RF magnetron sputtering apparatus can be used.

(3) On the other hand, as shown in FIG. 4A, a thin film for a membrane made of silicon nitride, silicon carbide, carbon, silicon oxide, or the like is formed on the surface of the mask 3 as shown in FIG.

(4) An opening 5 is formed in the center of the mask 3 by a process such as wet etching with an alkaline aqueous solution (FIG. 4B).

(5) Then, a bonding layer 2 made of a gold-silicon brazing material is formed on the other surface of the mask 3 in which the membrane thin film 4 is formed on one surface, that is, on the surface on which the mask frame 1 is bonded (FIG. 4 (c)).

(6) Next, the mask substrate 300 having the thin film bonding layer 2 made of a brazing material made of gold-silicon and the mask frame 1 are overlapped with each other, and under a nitrogen pressurized atmosphere whose oxygen concentration is adjusted to 500 ppm or less. To join by melting at least a part of the Au-Si-based brazing material (FIG. 4D). The heating temperature is preferably 280 ° C. or higher (eutectic temperature) for Au-20 wt% Sn, and 370 ° C. or higher for Au-6 wt% Si. By the treatment at this temperature, the brazing material forms a silicon mask and an eutectic alloy, so that the mask frame 1 and the mask 3 are firmly bonded. During the heating for joining, pressure is applied, because the adhesion can be improved.

(7) Then, a resist R is applied on the mask 3 and X-ray and electron beam transmitting portions are removed by dry etching such as ion beam etching (FIG. 4 (e)), and a portion corresponding to the mask pattern is removed. Then, a mask structure 100 is formed (FIG. 4F).

(Example 1)
(1) The mask 3 was manufactured by dicing an 8-inch silicon wafer (thickness = 0.725 mm) into a rectangular (outer shape) of 152 mm square (a square of 152 mm on one side). An SiC thin film 4 having a thickness of about 0.3 to 0.5 μm was formed on the mask 3 by a CVD method (PD-220 manufactured by SAMCO). The thin film may be a Si film. However, in this case, it is preferable to form a thermal oxide film of 1 μm on the silicon wafer as an etching stopper layer before forming the film.
(2) Next, a positive resist is applied on the entire back surface of the mask 3 to form a membrane, and only a central portion (50 mm square shape or 80 mm φ round shape) for forming a mask pattern is exposed, Removed. That is, when the resist on the back surface of the mask 3 is used as a mask and wet-etched with a 30% KOH aqueous solution (liquid temperature of 100 ° C.) for 7 hours, the silicon wafer is back-etched, the SiC thin film remains as an etching stopper layer, and the opening 5 is formed. Next, the resist on the back surface was completely removed with acetone.
(3) Next, in order to prepare the mask frame 1, 100 parts by weight of silicon carbide and 5 parts by weight of B4C are mixed, sintered under a pressure of 200 kg / m2, and then processed to have an outer shape of 152 mm square. And a silicon carbide plate having a thickness of 0.8 to 7.25 mm was obtained. The thickness ratio between the mask 3 and the mask frame 1 is 0.1 to 0.9 as shown in FIG.
(4) Next, the center of the silicon carbide plate for a mask frame was machined by a drill, and an opening 5 having a diameter of 50 mm was provided to obtain a mask frame 1.
(5) Next, the four portions of the thin film (membrane) of the mask substrate 300 and the portions other than the adhesive surface of the mask frame 1 were protected by a metal mask. As shown in FIG. 4, an active metal layer made of Ti and / or Cr is formed on the surface of the mask 3 to a thickness of 0.06 μm in order to improve the adhesion between the mask 3 and the mask frame 1 and the thin film bonding layer. A coating layer made of Pt was formed thereon with a thickness of 0.2 μm or more using a sputtering apparatus (CFS-4ES-231 manufactured by Shibaura Seisakusho). This treatment is effective for preventing the brazing material from diffusing into the active metal and reducing the peeling due to stress such as a difference in thermal expansion.
(6) Next, the brazing material was formed on one surface of the mask 3 by sputtering to form a thin film bonding layer having a thickness of 2 μm or more. The thin film bonding layer 2 thus obtained is composed of an active metal layer (Ti, Cr) serving as an adhesion underlayer, Pt serving as a coating layer, and a metal material Au-Sn 80 wt% serving as a eutectic alloy bonding material layer after melting. It is made of brazing material. As a thin film forming apparatus, a sputtering apparatus (CFS-4ES-231, manufactured by Shibaura Seisakusho Co., Ltd.), in which segregation of the film was smaller than that of vapor deposition and adhesion strength was obtained, was used. After confirming a degree of vacuum of 10 5 Pa or less as a thin film forming condition, a Ti / Pt / flatness of 2 μm or less and a film thickness of 0.1 to 30 μm is controlled while controlling the output while flowing high-purity Ar gas at 80 cc / min. An Au / Sn thin film bonding layer was formed. In this case, an Au-based brazing filler metal was selected as the Au-based brazing filler metal. This is because the chemical resistance (elution with a cleaning agent such as an alkali or an acid) is superior to other brazing materials when cleaning the Si mask after bonding.
(7) Next, in a state where the mask 3 having the thin film bonding layer 2 and the mask frame 1 were tightly fixed and integrated, they were melt-bonded by heating in an N2 atmosphere having an oxygen concentration of 500 ppm or less. The temperature at this time was controlled at a temperature of 300 ° C. (not less than the eutectic point), and after holding for 5 minutes or more so that a load of 8.8 MPa was applied only to the joint surface, the temperature was gradually cooled to room temperature. As shown in FIG. 6, the thickness of the thin film bonding layer is controlled in the range of 0.1 to 30 μm, and the material of the eutectic alloy is stable and does not cause mask damage at an environmental temperature in a process such as exposure baking. Materials that can be joined in a low temperature range were selected. Therefore, the mask substrate and the mask frame are integrally and closely bonded at a low temperature by the thin film adhesive layer formed of a eutectic alloy or the like. Was able to reduce the effect.
(8) Next, a rectangular stencil pattern of a SiC thin film (membrane) was formed on the Si mask 3 of the joined body (mask structure). That is, the joined body was washed with hydrofluoric acid, a resist was applied, exposed and developed to form a rectangular pattern with the resist, and SiC was etched by dry etching to form a perforated stencil thin film. Then, the joined body was washed with a hydrochloric acid / hydrogen peroxide aqueous solution, an ammonia / hydrogen peroxide aqueous solution, and IPA to obtain a mask structure.

(Example 2)
Basically, the configuration was the same as that of Example 1, and silicon was used as the mask frame 1 instead of silicon carbide. The mask frame 1 was processed by slicing and dicing from a single crystal silicon ingot pulled up by the CZ method to form a rectangular plate having the dimensions and shape of Example 1.

  In the first embodiment, an adhesion underlayer of Ti or the like is formed on the mask frame 1 and the mask 3 by a sputtering apparatus (CFS-4ES-231 manufactured by Shibaura Seisakusho). Were bonded together, and a thin film of Au 96.85 wt% -Si 3.15 wt% was formed as a bonding layer only on the mask frame side. The conditions for forming this thin film are as follows: after confirming that the atmosphere is at a degree of vacuum of about 10 5 Pa or less, a flatness of 1 μm or less and a film thickness of 0.1 An Au-Si alloy thin film bonding layer of ３０30 μm was used (however, only when the thickness was 30 μm, Au 96.85 wt% -Si 3.15 wt% foil was used). Thus, eutectic bonding of Au-Si was performed under the same conditions as in Example 1, and the reinforcing mask frame 1 and the mask 3 were bonded.

(Example 3)
The mask frame 1 was formed by cutting out an opening (20 mm square) provided at a joint portion with the mask substrate from an 8-inch silicon wafer (thickness t = 0.725 mm) with a dicer. Next, a silicon wafer (mask substrate) of 152 mm square and 0.8 to 7.25 mm in thickness was obtained by performing sizing and dicing from the single crystal silicon ingot pulled up by the CZ method to obtain a silicon wafer (mask substrate). As in the case of the mask frame 1, an opening of 20 mm square was cut out from the joint portion with a dicer to obtain a mask substrate 300. A thin film bonding layer made of a brazing material of 96.85 wt% Au-3.15 wt% Si was interposed between the mask frame 1 and the mask substrate 300. That is, this thin film bonding layer had a thickness of 0.1 to 30 μm. That is, a thin film of 96.85 wt% Au-3.15 wt% Si was flowed on the mask frame 1 side with a sputtering apparatus (CFS-4ES-231 manufactured by Shibaura Seisakusho), and a high purity Ar gas of a vacuum degree of 105 Pa or less was flowed for 30 scom. In this state, it was formed while controlling the output.

  However, only when the thickness was 30 μm, a preform foil of 96.85 wt% Au-3.15 wt% Si was used. In this embodiment, the reason why the Au alloy of 96.85 wt% Au-3.15 wt% Si was used as the thin film bonding layer is that the alloy is an Au-rich brazing material, so that the chemical resistance during cleaning (alkali / acid) is high. This is because impurities do not need to be taken into account because they contain only the same material (Si) as the object to be joined.

  Next, the mask frame 1 and the mask substrate (silicon wafer) 300 were melt-bonded by heating in an N2 atmosphere having an oxygen concentration of 100 ppm in a state of being tightly fixed with the thin-film bonding material interposed therebetween. The temperature at this time was controlled at a heating temperature of 400 ° C., a load of 6 MPa was applied, the temperature was maintained for 10 minutes, and the temperature was cooled to room temperature.

(Example 4)
In this example, only the thin film bonding layer made of Au-Sn was used, and the thickness of the bonding layer was 5 μm, without providing the adhesion underlying layer of Ti or Pt in Example 1 as the bonding layer.

(Example 5)
In this example, an Al brazing material (alloy name: 3003) was used as the bonding layer in Example 1, and the thickness of the bonding layer was 5 μm.

(Example 6)
This example is an example in which the brazing material is formed on the mask 3 by a vacuum deposition method instead of sputtering in the first embodiment. The apparatus used for this vapor deposition treatment was a vacuum vapor deposition apparatus (trade name: FEE-420, manufactured by JEOL Ltd.) under the conditions of a vacuum degree of 3.0 × 10 −3 Pa and a film formation rate of 3.8 ° / sec. is there. In this example, the thickness of the bonding layer was 5 μm.

(Example 7)
This example is basically the same as Example 1, except that the mask substrate and the reinforcing frame are directly bonded by anodic bonding. The joining conditions were as follows: the mask substrate and the reinforcing frame were joined and stored in an electric furnace, and the electric furnace was heated to 300 ° C. while applying 1000 V DC voltage as + and − poles, and left for 10 minutes. .

(Example 8)
This example is basically the same as Example 1, except that a disk-shaped (outer) silicon carbide substrate having a thickness of 0.725 mm and a diameter of 150 mm was used as a mask frame. The opening was a rectangular opening of 20 mm □, and the thickness of the bonding layer was 5 μm.

(Example 9)
In the same manner as in the first embodiment, an active metal adhesion layer of 0.1 μm in thickness, such as Ti or Cr, is formed on the silicon mask frame 1 under the same conditions as in the first embodiment. A film of 96.85 wt% Au-3.15 wt% Si having a thickness of 0.0 μm was formed. The mask frame 1 and the mask 3 were heat-fused and joined in an N2 atmosphere having an oxygen concentration of 100 ppm in a state where they were tightly fixed and integrated. The conditions for forming the Au-Si alloy thin film, the thickness, and the bonding conditions were the same as those in Example 3.

(Example 10)
100 parts by weight of silicon carbide and 5 parts by weight of B4C were mixed, sintered at a pressure of 200 kg / m2, and processed to obtain silicon carbide ceramics 3 having a square of 20 mm and a thickness of 0.5 mm. Only 96.85 wt% Au-3.15 wt% Si was formed on the bonding surface of the silicon carbide ceramics 3, and the membrane 4 obtained in the same manner as in the third embodiment was joined in the same manner as the first embodiment. However, those having a thickness of 30 μm were joined with a preform foil of an Au—Si alloy interposed therebetween. The conditions for forming the Au-Si alloy thin film, the thickness, and the bonding conditions were the same as those in Example 3.

(Example 11)
On the silicon carbide ceramics 3 obtained in the same manner as in Example 4, an active metal adhesion underlayer having a thickness of 0.1 μm, such as Ti or Cr, was formed under the same conditions as in Example 1, and a further thickness was formed thereon. A 1.0 [mu] m 96.85 wt% Au-3.15 wt% Si film was formed. However, those having a thickness of 30 μm were joined by sandwiching a preform foil of an Au—Si alloy. The conditions for forming the Au-Si alloy thin film, the thickness, and the bonding conditions were the same as those in Example 3.

(Test results)
For Examples 1, 2, and 8, an X-ray exposure test was performed using a transporter of the mask structure to measure the amount of pattern shift from a position where it should be originally formed on the wafer. The measurement was performed with an electron microscope. The deviation amount was about 0.01% in Examples 1 and 2, but was 0.1% in Example 8. In addition, when the operation test was performed 5000 times with the transfer device, no damage was confirmed on the mask substrate in Examples 1 and 2, but a crack was generated on the mask substrate in Example 8.

  For Examples 1, 4, 5, and 6, a measurement test of the adhesion strength between the mask substrate and the mask frame was performed. The test conditions were as follows. Using an Autograph AG-IS manufactured by Shimadzu Corporation, the nut part was bonded to the mask 3 at three points at an equal position with an epoxy adhesive, and after curing, a bolt was attached and the bolt part was sandwiched between jigs. The test was performed at 1 mm / min. The joining strength was determined as a value obtained by dividing the maximum tensile load by the joining area. As a result, Example 1 was 127 MPa, Example 4 was 65 MPa, Example 5 was 80 MPa, Example 6 was 105 MPa, and Example 1 was the most excellent.

  Further, the mask structures of Example 1 and Example 5 were washed with a diluted hydrofluoric acid aqueous solution, and then a test for measuring the adhesion strength between the mask substrate and the mask frame was performed. The test conditions were as follows. Using an Autograph AG-IS manufactured by Shimadzu Corporation, the nut part was bonded to the mask 3 at three points at an equal position with an epoxy adhesive, and after curing, a bolt was attached and the bolt part was sandwiched between jigs. The test was performed at 1 mm / min. The joining strength was determined as a value obtained by dividing the maximum tensile load by the joining area. As a result, Example 1 had a pressure of 125 MPa, and Example 5 had a pressure of 15 MPa. It was confirmed that Example 1 had high adhesion strength and had hydrofluoric acid resistance.

Further, in Examples 1 and 4, the relationship between the pattern distortion and the ratio of the mask substrate / mask frame, and the relationship between the flatness and the thickness of the bonding layer are shown in FIGS. 5 and 6, respectively.
In addition, the flatness was measured using (Kuroda brand name Nano Metro 400FW). The definition is defined as the difference between the Min value and the Max value from the reference surface where the mask 3 is bonded and fixed to the mask frame 1 over the entire rectangular plane of the mask structure 100 to the mask surface. However, the reference plane was set so that the difference was minimized.
The pattern distortion means that a mask is formed into a distorted pattern with respect to a certain point (X0, Y0) in the pattern, assuming that a nearly perfect rectangular pattern that has been subjected to close proximity exposure at the same magnification with a resist applied to a Si wafer is completed. It is defined as √ (X1−X0) 2 + (Y1−Y0) 2 when the position shifts and the coordinates move to (X1, Y1).

  In this test, using an autograph AG-IS manufactured by Shimadzu Corporation, a nut portion was adhered with an epoxy-based adhesive, and after curing, a bolt was attached, and the bolt portion was sandwiched between jigs, and the test speed was 1 mm / min. The joining strength was determined as a value obtained by dividing the maximum tensile load by the joining area. As a result, at 1 μm, Example 3 was 161 MPa, Example 9 was 148 MPa, Example 10 was 15 MPa, and Example 11 was 115 MPa, and it was found that Example 3 had the highest adhesion strength and was excellent.

  Also, it can be seen that the brazing material made of an Au-Si alloy has higher adhesive strength when no impurities are present. FIG. 8A shows the result of the energy dispersive X-ray fluorescence analysis of the Au—Si brazing material used in Example 3, but no impurities were observed. On the other hand, FIG. 8B shows the results of energy dispersive X-ray fluorescence analysis of the Au—Si—Ti brazing materials in Examples 9 and 11. In the case of bonding of SiC and Si, the bonding strength is improved when Ti is present, and the bonding strength is reduced when no impurities are present.

The above results are summarized as follows.
By setting the thickness of the thin film bonding layer to about 0.5 to 10 μm, preferably 1 to 5 μm, and more preferably about 2 to 4 μm, the flatness is high, that is, the distortion amount of the mask can be reduced (FIG. 6). Than).
On the other hand, in the case of the mask structures shown in Examples 4 to 11, since it is not a suitable example, it was found that the flatness of the mask was as large as 14 μm.

  The present invention is used in the field of semiconductor manufacturing / inspection devices such as mask frames for electron beam lithography.

It is sectional drawing of the mask structure of this invention. It is a schematic diagram which shows the planar shape of a mask frame. It is sectional drawing of the mask structure of this invention. It is a mimetic diagram explaining a manufacturing process of a mask structure of the present invention. 9 is a graph showing a relationship between a pattern and a thickness ratio between a mask and a mask frame. It is a graph which shows the relationship between joining layer thickness and flatness. It is a schematic diagram explaining the shape of the conventional mask frame. It is an analysis chart of a gold-silicon brazing material.

Explanation of reference numerals

Reference Signs List 1 mask frame 2 bonding layer 3 mask 4 membrane 5 opening 300 mask substrate S alignment scope M alignment mask

Claims (14)

In a mask structure obtained by integrating a mask substrate and a mask frame via a bonding layer, the mask substrate and the mask frame are bonded to each other by a thin film bonding layer having a thickness of 0.5 to 10 μm. Mask structure. The mask structure according to claim 1, wherein a thickness ratio between the mask substrate and the mask frame is 0.2 or less. The mask structure according to claim 1, wherein the mask frame has a polygonal outer shape and a circular opening at a center. A mask structure directly joined to a mask substrate and a mask frame, wherein a thickness ratio between the mask substrate and the mask frame is 0.2 or less. The mask structure according to claim 4, wherein the mask frame has a polygonal outer shape and a circular opening at a central portion. A mask structure comprising a mask substrate and a mask frame joined via a joining layer, wherein the mask frame has a polygonal outer shape and a circular opening at a central portion. The mask substrate and the mask frame are made of any one of silicon, carbon, oxide ceramics, carbide ceramics, and nitride ceramics, according to claim 1. Mask structure. The mask structure according to claim 1, wherein the bonding layer is made of an Au brazing material. 7. The mask structure according to claim 1, wherein the bonding layer is a thin film bonding layer including an active metal layer, a coating layer, and a brazing material layer. In a mask structure obtained by integrating a mask substrate and a mask frame via a bonding layer, the mask substrate and the mask frame are both made of silicon, and the bonding layer is made of an alloy of gold and silicon. A mask structure, wherein a substrate and a mask frame are bonded by a thin film bonding layer having a thickness of 0.5 to 10 μm. The mask substrate and the mask frame are directly bonded by an anodic bonding method, or a bonding layer made of a brazing material made of gold and silicon and having a high relative content (weight ratio) of gold is interposed between the mask substrate and the mask frame. A method of manufacturing a mask structure, comprising applying a load of 4 MPa or more in an atmosphere of 500 ppm or less, and heating and joining to a temperature of eutectic temperature (365 ° C.) to 500 ° C. 12. The method according to claim 11, wherein both the mask substrate and the mask frame are formed of silicon, and a eutectic alloy of silicon and gold is used as a bonding layer. A reinforcing mask frame having a polygonal outer shape and a circular opening in the center. 14. The reinforcing mask frame according to claim 13, wherein the reinforcing mask frame is made of silicon, carbon, oxide ceramic, carbide ceramic or nitride ceramic.

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