KR0175351B1 - X-ray blank mask and preparation method thereof - Google Patents

Abstract

The present invention relates to an X-ray blank mask having a high light transmissive alignment window and a method of manufacturing the same, in order to solve the problem that the transmission membrane for the X-ray mask of the prior art has low light transmittance and poor interlayer alignment. region arranged light is transmitted from the X- ray mask is a structure in which the membrane material has excellent light transmittance, the membrane material undamaged by a X- ray exposure on a wafer, a Si ₃ N ₄ as the sort window membrane For the membrane on the chip, Si ₃ N ₄ / poly-Si / Si ₃ N ₄ is used, and the membrane on the alignment window is Si ₃ N ₄ / SiO _2. The membrane on the needle is Si ₃ N ₄ / poly. -Si / Si ₃ N ₄ is used.

Description

X-ray blank mask and preparation method thereof

1 is a cross-sectional view of a typical X-ray mask.

2 is a plan view of a typical X-ray mask.

(A)-(d) of FIG. 3 is an X-ray mask manufacturing process drawing which uses SiN as a membrane in the conventional X-ray mask structure.

4A to 4D are X-ray blank mask manufacturing process diagrams using SiC as a transmission film in a conventional X-ray mask structure.

(A)-(e) of FIG. 5 is an X-ray blank mask manufacturing process drawing which uses poly-Si as a permeable film in the conventional X-ray mask structure.

Figure 6 (a) to (f) is a structure and manufacturing process diagram of an X-ray blank mask having an Si ₃ N ₄ alignment window of an embodiment of the present invention.

Figure 7 (a) to (f) is a structure and manufacturing process diagram of the X-ray blank mask having a Si ₃ N ₄ / SiO ₂ alignment window of another embodiment of the present invention.

* Explanation of symbols for main parts of the drawings

41,51: First and second silicon wafers 42,44,52,55: First to third Si ₃ N ₄ thin films

43,53: first and second poly-Si thin films 45,56: first and second resists

46,57: first and second pyrex ring

54: SiO ₂ thin film

The present invention relates to a novel X-ray blank mask structure having a high light transmissive alignment window and a method of manufacturing the same. Particularly, in the region where the alignment light transmits on the wafer, a transparent membrane having excellent light transmittance is used as the alignment window, and the chip portion TECHNICAL FIELD The present invention relates to an X-ray blank mask structure and a manufacturing method having a high light transmission alignment window formed using a poly-Si centered film.

In general, the structure of the X-ray (Ray) mask is formed of Si (1), SiN (2), Pyrex ring (3), Au (4), as shown in FIG.

It consists of a mechanically strong support, a membrane with a thickness of 2 µm that transmits X-rays well, and a material that absorbs X-rays well.

As shown in FIG. 2, the structure of the permeable membrane includes three alignment windows 5 for aligning a wafer and a mask, and a chip window 6 and one chip region. It is formed of the line absorber (Au) (7).

This principle of the X-ray mask basically uses the difference in the X-ray absorption coefficient.

In other words, X-rays are well absorbed by elements with large atomic numbers, and as absorbers, such as Au (gold), W (tungsten), and Ta (tantalum), the atomic number is relatively large, and deposition, pattern formation, and stress (Stress) ) Use a material that can be easily adjusted. Use a material with low atomic number and good strength as the permeable membrane.

At this time, the X-ray transmission ratio of the permeable membrane and the absorber should be about 10: 1 or more, and the X-ray transmittance of the permeable membrane should be 50% or more.

Since the optical properties of the transmission film have a great influence on the interlayer alignment of the wafer, the transmittance in the visible light region, which is the alignment light, should be maintained at 70% or more, and there should be no deformation of the material due to X-ray exposure.

However, the transmissive films for X-ray masks developed so far include SiN, SiC, and Poly-Si.

The structure and manufacturing process of the X-ray blank mask using SiN as a transmission film among the X-ray mask structures are as shown in FIG.

First, steps (a) and (b) of depositing 2 µm SiN (12) on the front and back surfaces of the silicon wafer 11, and (c) etching the back surface of the silicon wafer 11 into a SiN transmission film having a predetermined shape; The step (d) of joining the Pyrex ring 13 is performed to form an X-ray blank mask.

The SiN thin film used here has good transmittance to light and X-rays, good mechanical stability, and a simple thin film manufacturing process.

However, in the case of SiN, the hydrogen concentration inside is affected by X-ray exposure, which causes deformation of the SiN thin film, resulting in distortion of the pattern.

On the contrary, the structure and manufacturing process of the X-ray blank mask using SiC as a transmission film in the conventional X-ray mask structure are as shown in FIG. 4, and as shown, the silicon wafer 21 Step (a, b) of depositing a 2㎛ SiC (22) on the front and back, and etching the back side of the silicon wafer 21 to form a transmissive film to increase the light transmittance (SiO ₂ ) (23) The process (c) of vapor deposition and the process (d) of joining the pyrex ring 24 are carried out to form an X-ray blank mask.

Such SiC thin films are known to be much superior to Si-based transmembrane having different mechanical strengths, and are currently being spotlighted as X-ray mask transmissive membrane materials.

However, even when the ARC (Anti-Reflective Coating) material is deposited with a low light transmittance of about 40%, there are many problems that are insufficient for excellent interlayer alignment because light transmittance is increased by only about 10-20%.

In addition, the structure and manufacturing process of the X-ray blank mask using poly-Si as a transmission film in the conventional X-ray mask structure are as shown in FIG.

(A, b) depositing 0.3 μm SiN 32 on the front and back of the silicon wafer 31 and depositing 2 μm poly-Si 33 on the front and back of the 0.3 μm SiN 32 ( c) and depositing 0.3 μm SiN 34 on the front and back sides of the 2 μm poly-Si 33 and etching the back side of the silicon wafer 31 into a predetermined shape to form a permeable membrane. The step (e) of joining the Pyrex ring 35 is performed to form an X-ray blank mask.

As described above, the poly-Si thin film used as a permeable membrane can use a conventional silicon process as it is, and also has an advantage in that stress can be adjusted by deposition temperature and there is almost no loss due to X-ray exposure.

However, poly-Si also has a light transmittance of no more than 50% due to light absorption, which is known to occur at grain boundaries.

Such thin films do not fully meet the requirements of the mask mentioned earlier.

In other words, the thin film having excellent light transmittance is deformed by X-ray exposure, and when there is no deformation due to X-ray exposure, the light transmittance is 50% or less, making it very difficult to align the wafer layers, and reducing the interlayer alignment. There is a problem that results.

Therefore, in order to solve the above problems, the present invention uses a transparent membrane having a high light transmittance as an alignment window, and at the same time, an area exposed by X-rays is free from damage by X-ray exposure. It is an object of the present invention to provide an X-ray blank mask structure having a light transmitting alignment window using a material and a method of manufacturing the same.

The technical feature of the present invention for achieving the above object is that the alignment window is used as Si ₃ N ₄ or Si ₃ N ₄ / SiO ₂ , the chip portion is characterized by consisting of a permeable membrane of the poly-Si center.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

First, a manufacturing process will be described with reference to FIG. 6, which is an embodiment of the present invention.

The manufacturing process is first performed on the front and rear surfaces of the first silicon wafer 41, the first Si ₃ N ₄ thin film 42 having a thickness of 0.3 ㎛, the first poly-Si thin film 43 of 2 ㎛ thickness, the second Si ₃ of 0.3 ㎛ thickness The second Si ₃ N ₄ thin film 44 after a step (a) of sequentially depositing the N ₄ thin film 44, and patterning a desired portion by a lithography process on the back surface of the first silicon wafer 41. ), The first poly-Si thin film 43 and the first Si ₃ N ₄ thin film 42 are sequentially etched by dry etching, and the first silicon wafer 41 is etched by KOH to form a transmissive film. (b), and after the step (b), the first resist 45 is coated on the back surface of the first silicon wafer 41, and the first portion of the alignment window portion (see reference numerals A and B) is subjected to a lithography process. Developing the resist 45 and then cutting the second Si ₃ N ₄ thin film 44 on the back side of the wafer; and the first poly-Si thin film formed on the front and back sides of the first silicon wafer 41. 43) for KOH Wherein the back of the first silicon wafer 41 the first resist step (e) to remove 45 of the back side, a first silicon wafer (41) of claim 1Si ₃ N ₄ etching, and step (d) by using And (f) joining the first pyrex ring 46 to the upper surface of the thin film 42.

The structure of the X-ray blank mask is formed by the above processes.

Here, the Si ₃ N ₄ thin film used as the alignment window has a light transmittance of 80% or more at 633 nm.

In addition, the alignment window is formed as small as possible so that the supporting force of the permeable membrane is large even at a thin thickness (0.6 μm).

Meanwhile, the chip portion (see reference numeral C) is formed of the first Si ₃ N ₄ thin film 42 / the first poly-Si thin film 43 / the second Si ₃ N ₄ thin film 44.

In addition, to remove the 1Si ₃ N ₄ thin film 42 / the 1poly-Si thin film 43 / second 2Si ₃ N ₄ thin film (44) of claim 1poly-Si thin film 43 in the membrane of the above-described step (d) The process is applied on the back of the silicon wafer using a AZ 4562 resist 8㎛ or more, and then softened and dried at 130 degrees for 2 minutes.

After exposure for 90 sec using contact printing, development was carried out in AZ developer 0.6N, and then Si ₃ N ₄ (42,44) was etched in CF ₄ / O ₂ gas.

Then, the first poly-Si thin film 43 is removed by wet etching at 80 degrees Celsius.

As another embodiment of the present invention will be described with reference to Figure 7 having an alignment window of Si ₃ N ₄ / SiO ₂ as follows.

The fabrication process includes a 0.3 μm-thick ₃ Si ₃ N ₄ thin film 52, a 2 μm-thick second poly-Si thin film 53, and a 0.3 μm-thick SiO ₂ on the front and back surfaces of the second silicon wafer 51. After the step (A) of sequentially depositing the thin film 54 and the fourth Si ₃ N ₄ thin film 55 having a thickness of 0.3 μm, and patterning a desired portion on the back surface of the second silicon wafer 51 by a lithography process, The fourth Si ₃ N ₄ thin film 55, the SiO ₂ thin film 54, the second poly-Si thin film 53 and the third Si ₃ N ₄ thin film 52 are etched by dry etching, and the KOH solution (2) etching the silicon wafer 51 to form a permeable film, and applying a second resist 56 to the back surface of the second silicon wafer 51, and by means of a lithography process an alignment window (reference numeral, (C) developing the second resist 56 of A 'and B', and the fourth Si ₃ N ₄ thin film 55 and the alignment window portion exposed on the back surface of the second silicon wafer 51. 2nd in (A ', B') After etching the _third Si ₃ N ₄ thin film 52 on the front surface of the silicon wafer 51, and etching the second poly-Si thin film 53 on the front surface of the second silicon wafer 51, The step (E) of removing the resist and the step (F) of joining the Pyrex ring 57 to the upper surface of the SiO ₂ thin film 54 on the back surface of the second silicon wafer 51.

The structure of the X-ray blank mask is formed by the above processes.

Here, the Si ₃ N ₄ thin film used as the alignment window has a light transmittance of 80% or more at 633 nm.

In addition, the alignment window is formed as small as possible so that the supporting force of the permeable membrane is large even at a thin thickness (0.6 μm).

In addition, the chip portion (reference numeral C ') is formed of the third Si ₃ N ₄ thin film 52 / the SiO ₂ thin film 54 / the second poly-Si thin film 53 / the fourth Si ₃ N ₄ thin film 55. .

The _second poly-Si thin film 53 in the third Si ₃ N ₄ thin film 52 / SiO ₂ thin film 54 / second poly-Si thin film 53 / fourth Si ₃ N ₄ thin film 55 of the above-described process (E). ), The second silicon wafer 51 is coated on the back surface of the second silicon wafer 51 using AZ 4562 resist or more, and then softened and dried at 130 degrees for 2 minutes.

Then, after exposure for 90 sec using contact printing, development was carried out in AZ developer 0.6N, the oxide film was etched in C ₂ F ₆ / CHF ₃ gas, and then the _second poly-Si thin film in Cl ₂ / He gas ( 53) is removed by etching by reactive dry etching.

On the other hand, when the second poly-Si thin film 53 is deposited to a thickness of about 1.5㎛ thick, the surface roughness is very severe, causing a pin hole when depositing a Si ₃ N ₄ thin film, it is prevented In order to grow the thermal oxide film on the second poly-Si thin film 53 to smooth the surface of the poly-Si thin film.

When the process (E) is performed by dry etching, the poly-Si thin film and the Si ₃ N ₄ thin film do not have good selectivity, and thus the Si ₃ N ₄ thin film may be damaged. It can be grown using an excellent thermal oxide film.

Thus, since the permeable membrane of the alignment window used in the present invention is much thinner than the chip portion, the permeability of the permeation membrane should be increased by making the size of the alignment window as small as possible.

Further, considering that the alignment mark has a size of 50 μm × 50 μm, and considering the pattern exposure position accuracy in the electron beam lithography apparatus, the alignment mark can be sufficiently formed on the alignment window if the alignment window size is about 1 mm × 1 mm.

As described above, the present invention can fabricate a membrane for each use by membrane location using a conventional silicon process, and also align the low pressure vapor deposition (LPCVD) Si ₃ N ₄ film, which is a high quality film that is difficult to deposit more than 0.5 μm due to stress. It has the advantage of being used as a window.

Claims (7)

In the X-ray mask, the membrane of the alignment window portion where the alignment light is transmitted is Si ₃ N ₄ , and the membrane of the chip portion through which the X-ray transmits is Si ₃ N to prevent the loss caused by exposure during X-ray lithography. ₄ / poly-Si / Si ₃ N ₄ An X-ray blank mask, characterized in that formed on the front side of one silicon wafer, the Pyrex ring is bonded to the back side of the wafer. The X-ray blank mask of claim 1, wherein the alignment window membrane further comprises SiO ₂ in the Si ₃ N ₄ . The X-ray blank mask of claim 1, wherein the chip membrane is formed by further comprising SiO ₂ between the Si ₃ N ₄ and poly-Si / Si ₃ N ₄ . Claim to the back of the 1Si ₃ N ₄ thin film, the 1poly-Si thin film, the 2Si ₃ N step (a) and said first silicon wafer, depositing a _fourth thin film in this order on the side of the first silicon front and back the desired portion by a lithographic process After patterning, the second Si ₃ N ₄ thin film, the first poly-Si thin film, and the first Si ₃ N ₄ thin film were sequentially etched by dry etching, and the first silicon wafer was etched by KOH solution. A step (b) of forming a permeable film, and after the step (b), a first resist is applied to the back side of the first silicon wafer, and the first resist of the alignment window is developed by a lithography process, followed by a second Si on the back side of the wafer. ₃ N ₄ Sir Isaac the membrane is step (c) and the first to the second 1poly-Si thin film formed on the front and back sides of a silicon wafer and a step (d) of etching using a KOH solution, the first silicon wafer back (E) removing the first resist of the silicon wafer and the back surface of the first silicon wafer The 1Si ₃ N ₄ first Pyrex X- ray probe method rank mask having a light transmitting window made of a sort process (f) of joining the ring to the upper surface of the thin film. The method of claim 4, wherein the step of removing the first 1poly-Si thin film in the 1Si ₃ N ₄ thin film / the 1poly-Si thin film / the 2Si ₃ N ₄ thin film of the step (d) is given on the back of the first silicon wafer, A process of applying a resist to a predetermined thickness or more, a process of softening and drying for a predetermined time at a predetermined angle, exposing for a predetermined time using contact printing, and developing using a predetermined developer; CF ₄ / O After etching the Si ₃ N ₄ in ₂ gas, the first poly-Si thin film is etched and removed by wet etching at a predetermined temperature of the KOH solution X-ray blank having a light transmitting alignment window, characterized in that Mask manufacturing method. Sequentially depositing a _third Si ₃ N ₄ thin film, a second poly-Si thin film SiO ₂ thin film and a fourth Si ₃ N ₄ thin film on the front and back of the second silicon wafer, and on the back surface of the second silicon wafer. After patterning a desired part by a lithography process, the fourth Si ₃ N ₄ thin film, SiO ₂ thin film, second poly-Si thin film and third Si ₃ N ₄ thin film are etched by dry etching, and the second silicon is etched by KOH solution. A process (B) of etching the wafer to form a permeable film, a process of applying a second resist to the back surface of the second silicon wafer, and developing the second resist in the alignment window region by a lithography process; claim to a claim 4Si ₃ N ₄ thin film and the sort window, the step (D) etching a first 3Si ₃ N ₄ thin film on the front of the second silicon wafer in the region in and, the front of the second silicon wafer exposed to the back side of the second silicon wafer, After etching the second poly-Si thin film to remove the second resist Information (E) and, the first 2 X- ray method mask blanks having a silicon wafer, the back of the light transmitting window made of a sort process (F) for bonding the pyrex ring on the upper surface of the SiO ₂ thin film. The method of claim 6, wherein the removing of the _second poly-Si thin film from the _third Si ₃ N ₄ thin film / SiO ₂ thin film / second poly-Si thin film / 4Si ₃ N ₄ thin film of the step (E) is performed by using a second silicon wafer. Applying a predetermined resist on the back surface to a predetermined thickness or more, softening and drying for a predetermined time at a predetermined angle, exposing for a predetermined time using contact printing, and developing in a predetermined developer, and C ₂ F _And etching the oxide film in ₆ / CHF ₃ gas and then etching and removing the second poly-Si thin film by reactive dry etching in Cl ₂ / He gas. Rank mask manufacturing method.