JP2802438B2 - Back etching equipment for X-ray mask - Google Patents

Description

The present invention relates to an apparatus for manufacturing a mask for X-ray lithography that transfers an integrated circuit pattern onto a semiconductor substrate using X-rays.

(Prior Art) With the increase in the density of semiconductor integrated circuits, the elements constituting the circuit and the width of the wiring lines connecting the elements have been miniaturized. X-ray exposure technology capable of transfer is being studied. X
In the line exposure technique, an X-ray mask in which a pattern made of a material that absorbs X-rays is formed on a thin film having transparency to X-rays is inserted between an X-ray source and a semiconductor substrate to transfer a pattern.

FIG. 2 is a structural view of a basic X-ray exposure mask conventionally used. On one surface of a frame-shaped substrate 12 made of Si or the like, a thin film 13 (generally referred to as a membrane) having X-ray transparency, such as a SiN or BN thin film, is formed. This is a structure in which the X-ray absorber pattern 14 is formed. In X-ray exposure method, the number of wavelengths from 1Å
The pattern formed on the X-ray mask is transferred onto a semiconductor wafer by using an electromagnetic wave of more than 10 mm to manufacture a semiconductor integrated circuit. Since the X-rays in such a wavelength range do not have a very high transmittance to a substance, the thickness of the thin film 13 is several μm in a commonly used X-ray mask. Also, as for the substrate 12, a substrate having a thickness of usually several hundred μm to several mm is used,
X-rays of the wavelength used in X-ray exposure cannot pass through this substrate. Therefore, a window for removing a part of the substrate and transmitting X-rays for application to X-ray exposure
Form 15.

FIG. 3 shows an example of a conventional back etching apparatus for an X-ray mask. An etching solution 17 is filled in a solution holding tank 16, and an X-ray mask 19 is provided between the mask substrate holder 18 and the solution holding tank 16 via an O-ring or the like. The X-ray transmission window 15 is generally formed by a wet etching method using an alkali solution or an acid solution. When an X-ray transmissive window is formed on one X-ray mask, the amount of this solution is usually about several hundred cc. As shown in the figure, the pressure due to the weight of the solution is supported by the thin film 13 having a thickness of several μm.

(Problem to be Solved by the Invention) The pressure applied to the thin film 13 by the solution 17 varies from several g / cm ² to several tens g / cm ² , although it varies depending on the liquid amount. At this time, the amount of deflection generated in the thin film 13 due to the pressure due to the weight of the solution depends on the thickness of the thin film 13 and the area of the X-ray transmission window, but is 1 g / c.
It is several tens μm or more in m ² . For this reason, in some cases, irreversible deformation exceeding the plastic limit of the thin film 13 may occur,
Depending on the arrangement of the pattern formed on the thin film 13, there is a problem that a large stress acts locally in the plane of the thin film 13 and the thin film 13 is broken.

SUMMARY OF THE INVENTION The present invention has been proposed in order to improve the above disadvantages, and provides a buffer etching apparatus provided with means for preventing irreversible deformation and destruction of an X-ray mask occurring during formation of an X-ray transparent window. The purpose is to:

(Means for Solving the Problems) In order to achieve the above object, the present invention provides a sample having a structure in which one or more thin films are deposited on a substrate or a thin layer having a material change on a surface of the substrate. In a device for removing a portion of a substrate using a solution while leaving the thin film or the thin layer on a substrate from a sample having a solution, a pressure having a magnitude that offsets a pressure applied to a surface of the sample in contact with the solution, An object of the present invention is to provide a back etching apparatus for an X-ray mask, which has a means for adding the back surface of a sample.

(Operation) The present invention provides a back etching apparatus for an X-ray mask through a fluid on a surface opposite to a surface to be etched of an X-ray mask so as to offset a pressure applied to the surface to be etched of the X mask by an etching solution. By providing the means for applying pressure, it is possible to prevent irreversible plastic deformation or destruction of the X-ray permeable thin film generated during etching.

(Example) Next, an example of the present invention will be described.

The embodiment is merely an example, and it goes without saying that various changes or improvements can be made without departing from the spirit of the present invention.

FIG. 1 shows an embodiment of a back etching apparatus for an X-ray mask according to the present invention. In this embodiment, an apparatus having three tanks of an etching tank 1, a gas buffer tank 2, and a pressurizing tank 3 is shown.

Thus, a table 1a is provided at the lower part of the etching tank 1, and O is provided between the lower surface of the etching tank 1 and the upper surface of the table 1a.
An X-ray mask 19 is arranged via a ring. A pipe having a valve 10 is provided below the etching bath 1. A connecting pipe 9 is provided on the side of the table 1a. The other end of the connecting pipe 9 is connected to an upper part of a gas (for example, using air) buffer tank 2, and a connecting pipe 8 is provided on a lower surface of the gas buffer tank 2. The other end of the connecting pipe 8 is connected to the lower surface of the pressurizing tank 3. A pipe having a valve 10 is provided on the lower surface of the pressurizing tank 3.

Further, the lower surface of the pressurizing tank 3 is set at the same height as the back surface 7 of the X-ray mask substrate provided below the etching tank 1, and the pressurizing tank 3 is almost the same as the etching solution 4 filled in the etching tank 1. Liquid 5 having the same specific gravity is injected as the same volume as the etching liquid (so that the liquid levels in both tanks are the same).

The operation principle of the present device can be explained as follows. The pressure p _e exerted by the etching solution 4 to be etched surface 6 of the X-ray mask substrate, when the height of the density of the etching solution from [rho _e the surface to be etched to the upper liquid level and h _e, the gravitational acceleration is g , a p _e = ρ _e gh _e. Here, the atmospheric pressure is omitted because it is offset on both sides of the X-ray mask substrate. Next, the case where the pressurized liquid 5 is injected into the pressurized tank 3 will be considered. Assuming that the density of the liquid 5 is ρ _b and the height of the liquid 5 filled in the pressurizing tank 3 to the upper liquid surface is h _b , the pressurizing pressure by this liquid is applied to the gas buffer tank 2 via the connecting pipe 8. Transmitted, and further through the connecting pipe 9, X
It is applied to the surface 7 of the line mask opposite to the surface to be etched. This pressure is p _b = ρ _b gh _b . When the sign of the downward pressure is defined as positive, the thin film
Pressure delta _p to be applied to the 13 becomes _{Δ = g (ρ e h e} -ρ b h b). Accordingly, the etchant as to offset the pressure applied to the thin film 13 is set to _{ρ e h e -ρ b h b} ~0, the density of the pressurized liquid may be adjusted the water height.

In taking out the completed X-ray mask,
It is necessary to discharge the etching liquid in the etching tank and the pressurized liquid in the pressure tank at the same rate. In this embodiment, the variable opening valves 10 and 11 are attached to both layers, and the discharge speed is made the same.

Although the embodiment has been described above, it is not always necessary to perform pressurization with a combination of gas and liquid as shown in this embodiment. This can be performed with liquid as long as it does not affect the X-ray mask surface 7. It is possible. Further, the pressure may be controlled only by the gas. Rather than depositing a thin film on a substrate to make an X-ray mask, the material is changed by performing ion implantation on a substrate such as Si, etc. May be formed as a thin film, and this may be used as a mask membrane. It is apparent that the present invention can be applied to such a case. Note that the present invention is effective even if the mask membrane is a combination of a plurality of thin films, an X-ray absorber pattern is formed on the membrane, and another thin film is further thereon. Need not be explained.

(Effects of the Invention) As described above, according to the present invention, the back etching apparatus for an X-ray mask is configured to cancel the pressure applied to the surface to be etched of the X-ray mask by the etching solution so as to cancel the pressure applied to the surface to be etched. By providing a means for applying pressure through a fluid on the opposite side, it is possible to prevent irreversible plastic deformation or destruction of the X-ray permeable thin film generated during etching, and to manufacture an X-ray mask with high precision It can be performed. Further, there is an effect that an X-ray mask having a large-diameter membrane portion can be manufactured.

[Brief description of the drawings]

FIG. 1 shows an embodiment of the present invention, FIG. 2 shows the structure of a conventional basic X-ray mask, and FIG. 3 shows a conventional X-ray mask back etching apparatus. . DESCRIPTION OF SYMBOLS 1 ... Etching tank, 1a ... Stand, 2 ... Gas buffer tank, 3 ... Pressurizing tank, 4 ... Etching solution, 5 ... Pressurized liquid, 6 ... Etched surface, 7 ... X-ray Mask face, 8 ...
... connecting pipe, 9 ... connecting pipe, 10 ... variable opening valve, 11 ...
... Variable aperture valve, 12 ... X-ray mask support, 13 ... X
X-ray absorber pattern, 15 X-ray transmission window, 16 Etching tank, 17 Etching solution, 18
... X-ray mask substrate holder, 19 ... X-ray mask.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H01L 21/306 H01L 21/027

Claims (2)

(57) [Claims] 1. A method according to claim 1, wherein the thin film or the thin layer on the substrate is formed from a sample having a structure in which one or more thin films are deposited on a substrate or a sample having a thin layer having a material change on the surface of the substrate. An apparatus for removing a part of a substrate using a solution while leaving a portion of the substrate, the means for applying to the back surface of the sample a pressure having a magnitude that cancels the pressure applied to the surface of the sample in contact with the solution. Back etching equipment for masks. 2. The method according to claim 1, wherein the thin film or the thin layer on the substrate is left from a sample having a structure in which one or more thin films are deposited on the substrate or a sample having a thin layer obtained by changing the material on the surface of the substrate. 2. An apparatus for removing a part of a substrate using a solution by using a solution, comprising: means for simultaneously removing a pressure applied to a surface of the sample in contact with the solution and a pressure applied to a back surface of the sample after the removal is completed. Back etching apparatus for X-ray masks.