JPS605519A - Mask for x-ray exposure and manufacture thereof - Google Patents

Abstract

PURPOSE:To highten the accuracy in contrast and measurements of the titled mask as well as to enable to obtain the device at low cost by a method wherein a single layer of high melting point metal is formed on a mask substrate, the mask substrate side of said single layer is formed by granular crystal grains of high melting point metal, and an X-ray absorbing material is obtained. CONSTITUTION:An SiN mask substrate 22 having the property of X-ray transmission is formed on the wafer 21 consisting of Si, and an X-ray absorbing layer 23 of low internal stress consisting of a high melting point metal is formed by performing a high frequency sputtering method and the like on said mask substrate 22. Then, the resist 24 consisting of a high molecular material is applied by performing a spin-coating method, and a resist pattern 24 having the desired microscopic pattern is formed from the resist 24 by performing an exposure process having the desired microscopic pattern for the resist 24 and a developing process. Said resist pattern 24' performs the function as an electron absorbing body in the final stage of manufacture. Then, an X-ray absorbing pattern 23, consisting of Ta and having the desired microscopic pattern, and an Si frame 21' consisting of the circumferential part of the wafer 21 are formed.

Description

Detailed Description of the Invention (Technical Field) The present invention relates to X-ray haze technology, which is a fine pattern transfer technology for manufacturing semiconductor integrated circuits, and particularly relates to an X-ray exposure mask having high contrast and submicron patterns, and It is related to its manufacturing method.

(Prior art (-i)) As is well known, X-ray frost light is a technology that uses soft X-rays with a wavelength of 4 to 50 as a radiation source to transfer submicron fine patterns. It consists of an absorber pattern that absorbs soft X-rays well and an X-ray mask substrate that supports it and also allows soft X-rays to pass through well.

It is necessary to use a material for the absorber pattern that absorbs soft X-rays well. Here, if the soft X-ray wavelength is determined, the amount of soft X-ray absorbed by the absorber can be easily calculated from the linear absorption coefficient. Figure 1A, Figure 1B and Figure 1
Cl'4 is Mo-L line (5,41 people), 5i-
K line (7, 13 people) and humanities - line (A, 34 people)
The X-ray attenuation rates are shown for each layer thickness of various materials.

As is clear from Figures 1A to tC, the X-ray attenuation rate was set to 10 dB in order to obtain a sufficient mask con I last.
In order to achieve a certain level, gold (Au) and tantalum (Ta) are used.

It is easily determined that an element with a large atomic number, such as tungsten (S) or rhenium (Re), should be used.

For example, Japanese Patent Application Laid-Open No. 54-141571 (Japanese Patent Application No. 53-4
No. 8717) "Mask for Soft X-ray Lithography" contains gold (Au), platinum (Pt), palladium (Pd), and tungsten (W).

, a soft X-ray mask in which a minute pattern opening is sunk into a thin layer of soft X-ray absorbing material such as tantalum Ta, holmium Ho, erbium Er, uranium U, etc., and this pattern opening becomes a soft X-ray transmitting part. is disclosed.

Japanese Patent Application No. 54-11677 (Japanese Patent Application No. 53-71437), which is a Japanese application corresponding to U.S. Application No. 810469.
``A mask used in thin line lithography and its manufacturing method'' includes a mask substrate consisting of a thin layer containing a polymer such as parylene that is transparent to actinic radiation, a rare earth oxide that absorbs actinic radiation, gold Au, White firefly Pt, uranium υ,
Masks with absorbers composed of indium In and other dense high atomic number elements are disclosed, and ion etching is disclosed as a method for forming absorber layers of gold Ar, platinum Pt, uranium υ and other dense metals. method, plating method and lift-off method are described. However, it is difficult to process dense metal patterns using these methods.

Additionally, John N., Randall and J.C.W.
High-resolution pattern definition in tungsten (High-resolution pattern definition in tungsten) by
tern definition intungust
en)J (APPlied Physics Let
ters 39(9).

l November 1881. P.? 42),
A thin aluminum layer is interposed on a glass substrate, a tungsten W layer is deposited as an absorber, and a fine pattern is formed by reactive sputter etching. This is only an experiment regarding layers, and there is no mention of reducing internal stress when a tungsten layer, which is a high melting point metal, is deposited on an X-ray mask substrate, and the mask is not a practical mask.

In fact, the only material used as the absorber is Au. The reason for this is that conventional high melting point metals such as Ta, W, and Re have high stress during layer formation.
This is because the thin mask substrate may be damaged or distorted.

Therefore, the current situation is that Au, which is relatively easy to process, is used as the absorber pattern material. When using Au as the absorber, Maxcont 5 last is 10
To obtain dB, a thickness of 0.52 gm for the wire (8,34) on the AM-, and a thickness of 0.52 gm on the wire L near the Si-, 1
For 3 people), the thickness of about Q, 88gm will cost 8.

Therefore, when the pattern width is 0.5 p, m,
The aspect ratio is 1 or more.

Conventional methods for forming an Au absorber can be roughly divided into two methods: a method in which an insulating layer is processed and gold plated onto a mask, and an ion etching method.

In the method of forming fine Au patterns by electroplating using an insulator as a plating mask, it is possible to form a Saramicron pattern with steep sidewalls, but when there are four patterns with different dimensions, the current density is 11i. becomes uneven,
The layer thickness of small-sized patterns becomes thinner, the quality control of the plating solution is difficult, the Au pattern quality varies, and the number of steps is large.

When forming an Au absorber pattern by ion etching, for example, as shown in FIG. A mask substrate 2 is arranged, and a thin layer 3 of titanium T1 or tantalum Ta is provided on the mask substrate 2 to ensure the zf force between the Au absorber and the mask substrate 2. 2B
As shown in the figure, an X-ray absorber layer 4 is formed by depositing Au to serve as an absorber. Next, as shown in FIG. 2C, T
A metal layer 5 of I, Ta, etc. is formed, and a photoresist layer 6 is further formed on this metal layer 5 as shown in FIG. 2D.

Next, the photoresist layer 6 is subjected to an exposure process having a desired pattern, followed by a development process to form a first pattern.
As shown in Figure E, a photoresist layer 6' having a desired pattern is formed from the photoresist layer 6.

Next, using the photoresist layer 6' as a mask, an etching mask 5' having a desired pattern is formed from the gold LT layer 5 by etching treatment using, for example, CF4 plasma, as shown in FIG. 2E. do. Next, the photoresist layer 6' is removed from above the etching mask 5', and the X-ray absorber layer 4 is subjected to ion etching using ions of an inert gas such as At scum using the etching mask layer 5'. Then, as shown in FIG. 2G, an X-ray absorber pattern 4' having a desired pattern is formed from the X-ray absorber layer 4, and then an ion etching process is performed on the base layer 3.

After that, by etching the wafer 1 using a mask, etching is performed on the wafer 1 and the surrounding area 31.
A frame 1' is formed, and a desired X-ray exposure mask is removed as described above.

In this method, the etched Au particles are
As shown in Fig. 2G, the sidewalls of the Au absorber pattern 4' are re-attached to the sidewalls of the Au absorber pattern 4', and the etching mask 5' of Ti, Ta, etc. is largely retreated due to ion etching. The inclination angle of the cross section is about 75''. Therefore, conventionally, it has been difficult to form a fine Au absorber pattern on the submicron order with sufficient contrast using the ion etching method.

In order to solve the above-mentioned drawbacks of the Au ion etching method, reactive spanter etching of the W layer using SF6+02 mixed gas has been investigated (AppliedPhys.
sics 1etters, 39(9), P, 74
2) (supra) and 41(+) p. 247).

In forming the W layer, stress reduction was not sufficient, so an An underlayer was deposited on the glass substrate, and the W layer was formed on the -L layer. Furthermore, even when a polyimide layer is used as a practical mask substrate, an AU base layer with a thickness of 100 layers is deposited, and a W layer with a thickness of 800 layers is formed thereon. As described above, a thin tungsten layer whose internal stress cannot be reduced does not have sufficient contrast to normally used soft X-rays, and cannot be used as a practical mask.

Furthermore, in order to use it as an X-ray mask, it is necessary to remove the An underlayer for alignment. However, A9 without damaging the W absorber pattern. It is difficult to remove the underlayer, and this has the disadvantage that it cannot be used as a practical absorber for X-ray masks.

Ta is very promising as an absorber material for X-ray masks. However, it is difficult to reduce the internal stress of the Ta layer, which is a high melting point material. A Ta layer having a large internal stress may peel off from the mask substrate or cause large strain on the mask substrate. In severe cases, the Ta layer may damage the mask substrate. As described above, with a Ta layer having a large internal stress, it has been impossible to realize an X-ray exposure mask consisting of a Ta single layer absorber that can shorten the manufacturing process.

(11th point) Therefore, the object of the present invention is to eliminate the above-mentioned drawbacks and to use high-melting point materials such as Ta and W, which have an X-ray absorption coefficient comparable to that of Au in a soft X-ray wavelength range suitable for X-ray exposure. X! uses metal as an absorber, has high contrast, has high j-method accuracy, and can be configured in a simple manner. ! The purpose of the present invention is to provide an exposure mask.

Another object of the present invention is to use fewer manufacturing steps! One object of the present invention is to provide a method for manufacturing an X-ray exposure mask that can form fine patterns using high-definition melons.

(Structure of the Invention) In the present invention, a high melting point metal such as Ta or W is selected as the absorber material, paying attention to its high X-ray absorption ability and the ability to use reactive substrate etching. Examining low internal stress of layers and fine pattern etching
A mask for line exposure was realized.

In order to achieve the above object, the X-ray radiation mask of the present invention includes a mask substrate and a single layer of high melting point metal on the mask substrate, of which at least the mask substrate side has a high melting point. The X-ray absorber layer is formed of granular metal crystal grains and has a desired pattern.

In a preferred embodiment of the invention, the single layer described above is formed entirely of granular grains of refractory metal.

In a preferred embodiment of the present invention, an electron absorber layer is formed on the above-mentioned X-ray absorber layer -H.

In the present invention, the refractory metal can be tantalum or tungsten.

The electron absorber layer mentioned above can be a silicon oxide layer, a silicon nitride layer or a polymer layer.

” The double mask substrate is 5INIS13N 4 +
Sac.

It can be made of BN, polyimide resin, or a combination thereof.

In the method for manufacturing an X-ray exposure mask of the present invention, an X-ray mask substrate is placed on a sample stage in a state electrically insulated from ground potential in a sputtering apparatus having a mechanism for adjusting the gas flow rate and gas pressure of a rare gas. A first step fj1 in which several samples are placed, and a second step in which the above-mentioned gas flow rate and gas pressure are set to predetermined values and a high melting point metal layer is formed on the X-ray mask substrate under these conditions. and a third step for performing reactive sputter etching on the melting point metal layer to form an X-ray absorber layer in a desired pattern.

Here, a resist pattern is formed on the high melting point metal layer of tantalum or tungsten, and using the resist pattern as a mask, CBrF3
5' after applying reactive spatter etching using dregs!
Preferably, the method includes step 4v of forming a patterned X-ray absorber layer.

Furthermore, the third step is to form a silicon oxide layer or a silicon nitride layer on the high melting point metal layer made of tantalum or tungsten, form a resist pattern on the silicon oxide layer or silicon nitride layer, and The silicon oxide layer or silicon nitride layer is processed by reactive sputter etching using the resist pattern as a mask to form a pattern of the silicon oxide layer or silicon nitride layer, and using the pattern as a mask, CBrF is etched.
Preferably, the method includes a step of performing reactive sputter etching with three gases to form the X-ray absorber layer in the desired pattern.

Alternatively, in the third step, a high-melting point metal layer made of tantalum or tungsten is coated with a polymer layer having excellent dry etching resistance, a resist pattern is formed on the polymer layer, and a resist pattern is formed on the resist pattern. Add titanium or chrome to M! Then, a titanium or chromium pattern is formed by further lift-on, and a polymer pattern is formed by reactive sputter etching using oxygen gas using the titanium or chromium pattern as a mask.
Using the polymer pattern as a mask, it is preferable to form an X-ray absorber with a desired pattern by reactive sputter etching using CBrF:+ gas.

Note that the rare gas can be xenon, argon, or krypton.

In the present invention, it is preferable to adjust the gas flow rate and gas pressure of the sputtering apparatus so that the high melting point metal layer obtained in the second step described above becomes a layer containing granular crystal grains.

In the present invention, among the high melting point metal layers, at least
The side of the X-ray mask substrate can have granular crystal grains.

In a preferred embodiment of the present invention, in the first step described above, the sample such as the Si wafer on the sample stage can be placed in a floating state with respect to the ground potential.

Here, the gas pressure of the sputtering device and the high frequency power supplied to the sputtering device can be adjusted so that the surface of the sample has a floating potential of 110V to -20V.

Alternatively, in the first step, a DC bias potential of -10V to -20V may be applied to the sample on the sample.

(Example) Hereinafter, the present invention will be described in detail with reference to the drawings.

Cross sections of two examples of the X-ray exposure mask of the present invention are shown in FIGS. 3 and 4. In FIG. 3, 11 is a mask substrate that transmits X-rays well, 12 is an X-ray absorber button made of a high melting point metal such as Ta or W, and 13 is a frame 81 that supports the X-ray absorber pattern 12.

In the example shown in FIG. 4, in addition to the example shown in FIG. The material of the mask substrate 11 is SiN, 5i3No.

BN, SiC, polyimide resin, Mylar, or a combination thereof can be used. To obtain high-precision patterns, S! N, 5j31%, BN, S
It is preferred to use iC.

In the present invention, a base layer such as 11 is not provided on the mask substrate 11, but the mask substrate 11 itself has an X-ray transparent layer 15 made of the above-mentioned material and is placed 17 on this X-ray transparent layer 15 to increase the reflectance. It can also be constructed from an aluminum layer. In the present invention, a mask substrate is defined including the case of such a multilayer structure.

A first embodiment of an X-ray exposure mask according to the present invention and an embodiment of its manufacturing method will be described with reference to FIGS. 5A to 5F.

First, as shown in FIG. 5A, a mask substrate 22 made of, for example, SiN and having a thickness of 2 m, which has a property of transmitting X-rays, is formed on a wafer 21 made of, for example, Si. Here, as will be described later, it is preferable to reduce the internal stress of this Ta layer 23 and control it within ±1 x 109 dyne/cm2. It is preferable to form the Ta layer 23 in a high frequency sputtering apparatus equipped with a conductive pulse.

Next, as shown in FIG. 5B, a high melting point metal 1 made of Ta, for example, is applied to the soil of the mask substrate 22! Mr. internal stress X
The line absorber layer 23 is formed to a thickness of about 8,000 by high frequency sputtering or the like.

Next, as shown in FIG. 5C, this X-ray absorber layer 23''
Second, a resist 24 made of a polymeric material, for example a PMMA resist, is applied to a thickness of about 0.5 μm by a spin code method.

Next, the resist 24 is exposed to a desired fine pattern (e.g., ultraviolet light exposure, electron beam exposure, ion beam mist light), followed by development treatment, as shown in FIG. 5D. , a resist pattern 24' having a desired fine pattern is formed. Note that this resist pattern 24' ultimately plays the role of an electron absorber.

Next, as shown in FIG. 5E, the resist pattern 24'
As a mask, the X-ray absorber layer 23 is subjected to a reactive substrate etching process using CBrF3 gas to form an X-ray absorber pattern 2 made of Ta having a desired fine pattern.
3' is formed.

Finally, as shown in FIG. 5F, the S1 wafer 21 is etched to form a Si frame 21' around the wafer 21. Through the above steps, an X-ray exposure mask having a desired fine pattern is obtained.

In the top stripping, a resist pattern was used as the etching mask in JS4, but Figures 6A to 6H
As shown in the figure, for example, a silicon oxide layer or a silicon nitride layer is first formed using a resist pattern.
Reactive sputter etching is performed using a gas such as 6CF4+)l:L, and using the fine pattern of this silicon oxide layer or silicon nitride layer as a mask, Ta is etched in the same manner as in Example 10.
An absorber layer can also be formed.

More specifically, in FIG. 6A, the Si wafer 21"
- Then, as shown in FIG. 6B, an X-ray absorber layer 23 made of Ta is formed on the mask substrate 22 in the same manner as shown in FIG. 5B. Form.

Next, as shown in FIG. 6C, on the X-ray absorber layer 23,
An etching mask layer 25 consisting of a 5i02 layer, which will later be used as an electron absorber layer, is formed to a thickness of, for example, 2000 mm by various methods known per se.

Next, a resist layer 26 is formed on the etching mask layer 25 as shown in FIG. 160, and then the resist layer 26 is subjected to an exposure process having a desired pattern, followed by a development process as shown in FIG. 6E. As shown in FIG. 2, a resist pattern 26' having a desired pattern is formed from the resist layer 26.

Next, using the resist pattern 26' as a mask, C2
A reactive sputter etching process is performed using a gas such as F6 or CF4 to remove 5i02 having a desired fine pattern from the etching mask layer 25, as shown in FIG. 6F.
An etching mask pattern 25' is formed.

Incidentally, this etching mask pattern 25' ultimately plays the role of a ``jE child absorption IIy'' body.

Next, as shown in FIG. 6G, resist pattern 2B'
i etching mask pattern 25' is removed from J-, and then the X-ray absorber layer 23 is subjected to a reactive sputter etching process using CBrF3 gas using the etching mask pattern 25' as a mask to form the X-ray absorber layer 23. X made of Ta having a desired fine pattern from 23
A line absorber pattern 23' is formed.

Finally, as shown in FIG. 6H, 81
form a frame. That is, by etching the Si wafer 21, a Si frame 21' is formed around the wafer 21, thereby obtaining an X-ray exposure mask having a desired fine pattern.

Furthermore, in order to perform positive/negative inversion of the mask,
The steps shown in FIGS. 7A to 7J are taken. First, in the same way as described with reference to FIG. 5A, in the step of FIG. 78, a mask substrate 22 is formed on the Si wafer 21, and then, as shown in FIG. 7B, the mask Jk h 22 is formed on the Si wafer 21.
An X-ray absorber layer 23 made of Ta is formed thereon in the same manner as described above with reference to FIG. 5B.

Next, as shown in FIG. 7C, on the X-ray absorber layer 23, a polymeric material such as polyimide, which has high resistance to the reactive sputter etching process described later, is etched as an etching mask layer 27. is formed to a thickness of about 0.8 to 1.0 pm using various known methods. Note that this etching mask layer 27 will later be patterned to become an electron absorber pattern.

Next, as shown in FIG. 7D, an etching mask layer 27 is formed.
A resist layer 28 is formed thereon, and then the resist layer 28 is exposed to light to form a desired fine pattern.
After the subsequent development process, as shown in FIG. 7E,
A resist pattern 28' having a desired fine pattern is formed from the resist layer 28.

Next, as shown in FIG. 7F, a resist pattern 28
' and on the exposed etching mask layer 27,
For example, a metal layer 29a is formed on the region where the resist pattern 28' is not formed, and a metal layer 29b is formed on the resist pattern 28' by performing a base treatment of a metal such as titanium Ti or chromium Or. For example, the thickness is 500.

Next, the resist pattern 28' and the metal storage layer 28b formed thereon are removed by dissolving the resist pattern 28' from the etching mask layer 27'', that is, by lift-off. hand,
As shown in FIG. 7G, a fine pattern 29a of Ti or Or is obtained.

Next, as shown in FIG. 7H, using the metal pattern 29a as a mask, a reactive sputter etching process using 02 is performed to form a desired fine pattern from the etching mask layer 27, with a thickness of 0.8 to 1. An etching mask pattern 27' made of a polymeric material of about Qp,m is formed. This etching mask pattern 27' has dry etching resistance (in other words, it is used as a heavy particle absorber pattern).

Next, as shown in FIG. 7I, a reactive spanner etching process is performed on the X-ray absorber layer 23 using CBrF3 gas using the metal pattern 29a and the etching mask pattern 27' as a mask to form the X-ray absorber layer 23. From 23, an X-ray absorber pattern 23' made of Ta and having a desired fine pattern is considered. This pattern 23'
is a positive/negative inversion of the pattern obtained in the step shown in FIG. 5F. Note that in this step, the reactive sputter encroaching process may be performed after removing the metal pattern 29a.

Finally, as shown in FIG. 7J, the Si wafer 21 is etched to form a Si frame 21' around the wafer 21, and thus has a desired fine pattern for X-ray exposure. Get the mask.

In the present invention, in order to form the middle layer of the X-ray absorber layer 23 made of a high melting point metal such as Ta or W, it is necessary to reduce the internal stress of the absorber layer 23. for example,
A method of forming a low internal stress Ta layer 23 on one of the X-ray mask substrates 22 made of SiN will be described.

FIG. 8A shows a substrate for forming a Ta layer according to the present invention.
An example of the configuration of a printer device is shown, where 101 is a vacuum container;
102 is a main valve that controls the exhaust of the vacuum container 101;
O3 is the normal gas f! of the rare gas in the vacuum container 101. i'i
This is a variable contactance Ij valve. Vacuum container 10
1, a Ta target 104 and a sample stage 105 are arranged. High frequency power supply +0 for Ta target l-104
6 supplies a predetermined high frequency power. Sample stand 105J-
The S1 wafer/\21 as a sample on which the mask substrate 22 is placed is placed through the insulating plate 107. Here, the vacuum container +01 and the sample stage 105 are grounded and mounted.

The mask substrate 22 may be kept electrically floating from the ground potential as in this example, or the mask substrate 22 may be maintained at a predetermined bias (e.g., -1θ as a DC bias level), as will be described later. ~-, ov) It is preferable to apply 3.

Furthermore, in Fig. 88, 108 is the exhaust system 1 for combining and discharging the exhaust gas from the valves 02 and 103, and +09 is J:! , Empty container 101 He Xe, Ar, Kr
This is a rare gas introduction system for introducing rare gases such as. A waste flow rate control system is arranged in the rare waste introduction system 109. ll
1 is a vacuum gauge for measuring the degree of vacuum inside the container 101 at 3'j'''/%.

To form the Ta layer, first, the wafer 21 with the mask substrate 22 attached is placed on the sample stage 105 in the vacuum container 101 via the insulating plate 107, and the inside of the vacuum container 101 is pumped through the main valve 102 by the exhaust system 108. The degree of vacuum is 5
Evacuate to 10 Torr or higher.

Next, the rare gas is introduced into the introduction system 108, and the gas flow rate control system!
10 to a specified flow rate (for example, 7 to lθcc/m1
Introduce only n). Monitor the pressure at that time using the vacuum gauge 111 and make sure that it is at the predetermined pressure; 1! ! f
Then, the main valve 102 is closed and the variable pulse 103 is closed.
Set the pressure with an accuracy of 1/1000 Torr.

In this state, the Ta target 104 is sputtered by operating the high frequency city #1106. Mask substrate 2 at this time
The high frequency power of the high frequency power supply 106 is adjusted so that the potential generated on the surface of the high frequency power source 106 is between -10V and -20V.

FIG. 9 shows Xe as a rare gas in the apparatus shown in FIG. 8A.
With the flow rate of rare gas constant at 7cc/m1n,
, set the gas pressure on the 1/1000 Torr level with an accuracy of 1/1000 Torr, input 700 W of high frequency power, and
The Ta layer 23 is formed on the iN mask substrate 22-1- to a thickness of 0.5~
Xe when formed over 0.65 p, rn
The relationship between gas pressure and internal stress is shown.

As is clear from No. 91y3, due to the change in the Xe gas pressure, #? 8 stress has changed significantly.

When the Xe gas pressure is 0.02 Torr, the internal stress of the Ta layer is 2 kI'ti stress, which is 4 x 10"
dyne/cm2.

On the other hand, when the Xe gas pressure is 0.04 Torr, the internal stress of the Ta layer is the Leri stress of 3.8 Torr.
There is X109dyne/cm2.

In this way, the internal stress of the Ta layer changes rapidly from compression to tension due to a slight change in the Xe gas pressure. Therefore, in the present invention, the Xe gas pressure is set to a certain value by the waste flow rate control system 110 to A Ta layer with low stress within l x 109 dyne/cm' can be obtained.

Note that the dependence of the internal stress on the diluted gas pressure is
It varies depending on the φ class. For example, if argon is used as the rare gas, the result will be as shown in Figure 10.Furthermore, the dependence of the internal stress on the rare gas pressure can be improved by changing the design of the sputtering equipment or by changing the high melting point metal from Ta to W. are also different.

Further, in the sputtering apparatus shown in FIG. 8A, the mask substrate 2
When the surface potential of the substrate 2 is smaller than -IQV, the internal stress becomes compressive stress regardless of the gas pressure, and its value increases. The internal stress became tensile stress, and its value became large, regardless of the

Taking these into consideration, when using Xe gas in the sputtering apparatus shown in Figure 8A, the gas pressure is reduced to 1/10.
By controlling with an accuracy of 0.00 Torr, setting the temperature at a level of 10-'' Torr, and adjusting the high frequency power and gas pressure, the substrate surface potential is set in the range of -10 V to -2 QV.
Ta1g23 with low internal stress could be deposited on the mask substrate 22.

Alternatively, as shown in FIG. 8B, the sample stage 105'
s1 wafer in two? sample) 21 and mask substrate 2
-IOV~-2 to the substrate boulder 112 for holding 2.
By connecting the direct Mt of 0V and the bias voltage source 113, the voltage of -10V is applied to the mask substrate 22 from the substrate boulder 112.
Even when a DC bias voltage of ~-20V was applied, a Ta film 23 with low internal stress could be formed.

In the present invention, in this way, the internal stress of the Ta layer can be controlled to any desired value ((f); Therefore, controlling the substrate surface unit to -10V to -20V means that ions with an energy of about -10V to -20V collide with the Ta layer surface during layer formation, and ions with this energy The impact imparts energy H4 to the Ta atoms, allowing them to move freely on the surface being deposited, resulting in surface movement (surfac
e migration), thereby promoting the growth of JFt-shaped crystal grains, and as a result, Ta with low internal stress
Allows the formation of layers.

11A and 1ie, 12A and 12B, and 113AlΔ and i+3812 are SEM (scanning electron microscopy) of the surface and cross-sectional morphology when the internal stress of the Ta layer is approximately normal, compressive, and tensile, respectively. ) is a photograph.

Here, in order to clarify the internal structure, the surface and cross section are
Etching solution for tissue observation of a (HCI:)INO3+
) (to SO4, = l: 1: 2.5).

Figures 11A and 11B show T when the internal stress is almost zero.
A layer, Figures 12A and 12B are Ta layer and N when the internal stress is 4 x 109 dyne/cm' in pressure stress
The %laA diagram and Figure 138 show that the internal stress is tensile stress and is 3.
When X 10'dyne/cm2, it is 018 layer.

As shown in Figures 11A and 11B, when the internal stress of the Ta layer is almost zero, irregularities are observed on the surface with a period of about 0.5) Lm, and the cross-sectional structure is also compared accordingly. It has large crystal grains and is granular.

On the other hand, if there is a large compressive or tensile internal stress in the Ta layer, FIGS. 12A and 12B and $13
As is clear from Figure A and Figure 13B, there is 0 on the surface.
．． Crystal grains of about 1 grn are observed, and a columnar structure characteristic of high melting point metals is observed in the cross section. These photos show that the columnar crystals in the cross section are reflected on the surface.

Furthermore, @14A figure, 14B figure, and 14C figure,
The X-ray diffraction results of the Ta layer are shown when the Xe gas pressure is changed and the RF power is kept constant at 700 W. Here, the horizontal axis indicates the interplanar spacing of the grating, and the vertical axis indicates the normalized X-ray diffraction intensity. Xe gas pressure to 1.35X10 Tor
r, 3.05X 10 Torr and 4.40X l
When set to 0 Torr, the internal stress of the Ta layer is +1.4 X 10' dyne/cm 2 (compression), 0.31 X 109 dyne/cm 21: compression) and Ef, I Xl 09 dyne/cm 2 (',
tension).

As is clear from Fig. 14A, large compressive stress L: 8
．． In the case of 4XIO dyne/cm 2 ), a Ta (110) plane parallel to the mask substrate surface exists. On the other hand, when a large tensile stress exists in the Ta layer, as is clear from FIG. 14C, the T
The (211) plane of a exists. In this way, compression,
If the internal stress is large for either tensile stress, Ta
Columnar crystals with strong preferred orientation grow in the layer.

On the other hand, the internal stress is very small (0.31X
In the case of 109 dyne/cm 2), as shown in FIG. 14B, Ta (21·l) plane parallel to the mask substrate surface and (110) plane coexist. In other words, suppressing the growth of columnar crystals in the Ta layer and growing the crystal grains in a granular manner means that the Ta layer in which the (21+) plane and (+ io) plane of Ta coexisting parallel to the mask substrate surface is grown. It means to form.

As described above, the inventors have found that suppressing the growth of columnar crystals during layer formation is very important for reducing internal stress. In particular, suppressing the growth of columnar crystals at the initial stage of growth from the substrate is effective in reducing internal stress. Note that, on the contrary, there is no problem even if some columnar crystals grow on granular crystal grains. As described above, in the present invention, in order to form a medium-layer Ta absorber, a Ta layer with low internal stress is realized by controlling the crystal grains to be granular.

Figure 15 shows the oxygen content in the Ta layer and the Ta layer when the Ta layer is reactively sputter etched using CBrF3 gas.
The relationship between the layer etching rate and the layer etching rate is shown.

Here, the high frequency power was set to 100 W, and the CBrF3 cannulation pressure was set to 0.03 Torr. Ta tends to form oxides, nitrides, and carbides, but as shown in Figure 14, Ta
It was found that up to 10 atm.% of the oxygen-containing acid in the layer did not significantly affect the etching properties of Ta. Moreover, almost the same thing applies when nitrogen and carbon are contained as impurities other than oxygen. Therefore, in order to increase the etching rate, it is preferable to set the concentration of impurities such as 02 to about 10 atm.% or less.

As described above, according to one aspect of the present invention, the crystal grains of the Ta layer are controlled to have a granular shape by controlling the layer formation conditions of the Ta layer.
By reducing the internal stress and, if necessary, controlling the amount of impurities such as oxygen, nitrogen, carbon, etc. in the Ta layer, it is possible to use the Ta layer as an X-ray absorber. As for tungsten W, a W layer formed by reactive sulfur etching using CBrF3 gas can be suitably used as an X-ray absorber in the same manner as the Ta layer.

As can be seen from FIGS. 1A, 1B, and 1C, in order to obtain a mask contrast of 1 odB or more, the thickness of the X-ray absorber layer should be about 0.8 jLrtr or more.

As mentioned above, in the mask forming process of the present invention, reactive sputter etching is used in all the main steps after layer formation, so the etching selectivity is lower than that of the conventional Au ion etching method. Get big,
Unlike conventional ion etching methods, this method is different from conventional ion etching methods in that there is little deviation in pattern dimensions due to mask retreat, and since the material to be etched is removed by exhausting it in the form of volatile gas, there is less chance of re-deposition. It's easy to do.

As a result, for example, Ta
A submicron absorber pattern with a high spectral ratio of 7, such as a layer/thickness of 0.8 pm, can be formed with high dimensional accuracy and in a shape with vertical pattern side walls.

For comparison, a resist pattern was formed using the same deep ultraviolet exposure mask, and then SEW photographs were taken of the Au absorber pattern formed by the ion etching method and the Ta absorber pattern formed by the method of the present invention. is shown in comparison with FIGS. 18A and 188.

The layer thickness of both the Au and Ta absorbers was the same, 0.8 gm. This pattern has a pitch of 1. gm line and space pattern, but in the case of an Au absorber, the inclination angle of the side wall of the Au absorber is about 75 degrees, so the pattern is hardly resolved. That is, the conventional Au ion etching method shown in FIG. 16A cannot be applied to fine patterns of 0.5 pLm or less.

On the other hand, in the Ta absorber according to the present invention shown in FIG. 16B,
With vertical sidewalls, submicron patterns can be formed with high dimensional accuracy.

Furthermore, in the case of a conventional Au absorber produced by ion etching, a base layer 3 is required to ensure adhesion, as shown in FIG. 2A. Conventionally, align i marks were formed on this do layer, but since the under layer is very thin, the quality of the layer tends to vary, and the reflectance decreases due to the reaction between Ti and Au as the under layer. changes, which tends to lead to deterioration in the quality of marks, which causes misalignment when automatic alignment is performed. In contrast, according to the method of the present invention,
Since there is no need for an underlayer to ensure authenticity and only a single Ta layer is required, the quality of the alignment mark is stable and automatic alignment can be easily performed.

The mask forming process of the present invention is dry, and can be easily applied even when using a molecular mask substrate made of polyimide or the like, which has poor chemical resistance.

Furthermore, as shown in FIGS. 6A to 6H and FIGS. 7A to 7J, a combination of silicon nitride or silicon oxide/T'a absorber or polymer/Ta absorber may be used.
In the layer structure absorber, Auger electrons, photoelectrons, etc. generated from Ta are absorbed by the silicon nitride layer, silicon oxide layer, or polymer layer, so there is an advantage that the mask contrast can be further effectively improved.

(Effects) As is clear from the above description, the present invention exhibits the following various effects.

(2) Since a Ta layer with low internal stress is used, the Ta layer can be attached to the mask substrate without peeling off, and warpage and distortion of the mask substrate can be ignored.

(2) By using Ta for the absorber, reactive sputter etching can be used to process a 4fil1m pattern.

In the case of reactive sputter etching, there is no adverse effect such as uncutting or redeposition, so it has the advantage of being able to form fine patterns with high dimensional accuracy and having vertical sidewalls.

■) In the conventional Au absorber, the pattern size is lALm
On the other hand, in the Ta+'9 compound according to the present invention, it is more than 0.2j1. It is also possible to form a pattern of Ill.

(2) Unlike conventional Au absorbers, there is no need for a thin do layer to ensure adhesion, so the quality of alignment marks is improved.

V) Since the I rod is tri-shaped, a polymer layer such as polyimide, which has weak chemical resistance, can be used for the mask substrate.

Vl) Ta absorbers have lower material costs and are more economical than Au absorbers.

[Brief explanation of drawings]

Figures 1A, 18 and 1C are Mo-
Graph showing the relationship between absorber layer thickness and X-ray attenuation rate when lines are used for Lli, Si- and A1-, Figure 2A~
FIG. 2H is a cross-sectional view showing the sequential steps of manufacturing an X-ray mask having an Au absorber by a conventional ion etching method, and FIGS. 3 and 4 are cross-sectional views showing two examples of the X-ray exposure mask of the present invention. 5A to 5F are cross-sectional views showing the sequential manufacturing steps in one example of the method for manufacturing an X-ray exposure mask according to the present invention, and FIGS. 8A to 6H are sectional views showing a silicon oxide layer in an intermediate step. Cross-sectional views showing sequential manufacturing steps in another embodiment of the manufacturing method according to the present invention using a silicon nitride layer;
7A to 7J are cross-sectional views showing the sequential manufacturing steps in still another embodiment of the manufacturing method of the present invention, in which positive/negative reversal of patterns and patterns is performed using the Ti lift-off method.
Figure A is a schematic diagram showing an example of a sputtering apparatus used to form a Ta layer that becomes an absorber by implementing the manufacturing method of the present invention;
FIG. 8B is a diagram showing an example of a sputtering apparatus used in another embodiment of the manufacturing method of the present invention, FIGS. 9 and 1O are graphs showing the relationship between rare gas pressure and internal stress during sputtering of a Ta layer, Figures 11A and 11B are photographs showing examples of grain structures on the surface and cross section of the Ta layer when the internal stress is almost zero, and Figures 12A1Δ and 12B are photographs of 4 x 10 dyne/ 13. Photographs showing an example of the morphology of the grain structure on the surface and cross section of the Ta layer in cm'. Figures A and 13B show Ta when the internal stress is 3 x 109 dyne/cm2 of tensile stress.
Photographs showing the morphology of the particle structure on the surface and cross section of the layer, Figures 14A to 14C are graphs showing the relationship between the lattice spacing d and normalized X-ray diffraction intensity, and Figure 15 is CB.
Graphs showing the relationship between the amount of oxygen in the Ta layer and the etching rate using rF3 gas, Figures 18A and 18B are
1 is a photograph showing a particle structure of an example of an absorber bag for a line exposure mask, comparing a conventional example and an example of the present invention. ■...Wafer, 2...Mask substrate, 3...Underlayer, 4...X-ray absorber layer, 4'...Au absorber pattern, 5...Metal layer, 6...・Photoresist layer, 11...Mask substrate, 12...X-ray absorber pattern, 13...Si frame, 14...Electron absorber layer, 14'...X-ray arithmetic field pattern, 15... X-ray transparent layer, 16... Aluminum layer, 21... S1 wafer, 21'... Si frame, 22... Mask substrate, 23... X-ray absorber layer, 23' ...X-ray absorber pattern, 24...Resist, 24'...Resist pattern, 25...Etching mask layer, 25'...Etching mask pattern, 26...
Resist layer, 26'...Resist pattern, 27...Etching mask layer, 27'...Etching mask pattern, 28...
Photoresist layer, 28'...Resist pattern, 29a, 29b = Metal layer, IQ'l...Vacuum container, +1)2. . . . Main valve, 103 . . . Conductance rIf variable valve for adjusting the gas pressure of rare scum, 104 .= Ta Couget, +05 . . . Sample stand. 106... Front frequency power supply, 107... Insulating plate, +08... Exhaust system, 108... Right waste introduction system, 111... Vacuum gauge, 112... Substrate holder, 113... lI 'l current bias voltage source. Fig. 3 Fig. 4 Fig. 8A Fig. 8B Fig. 105 ↑~//J Fig. 9 f(%p

Claims (1)

[Scope of Claims] l) A mask substrate, and a single layer of a high-melting point metal formed on the mask substrate, and of the single layer, at least the mask substrate side is formed of granular crystal grains of the high-melting point metal. ,
Moreover, an X-ray exposure mask characterized by comprising an X-ray absorber layer having a desired pattern. 2. The X-ray exposure mask according to claim 1, wherein the entire single layer is formed of granular crystal grains of the high melting point metal. 3) An X-ray exposure mask according to claim 1 or 2, characterized in that an electron absorber layer is formed on the X-ray absorber layer. . 4) In the X-ray exposure mask according to any one of claims 1 to 3, the high melting point metal is tantalum or tungsten.
Mask for line exposure. 5) % Allowance The mask for X-ray exposure according to claim 3, wherein the electron absorber layer is a silicon oxide layer, a silicon nitride layer, or a polymer layer. 6) In the X-ray exposure mask according to claim 1, the mask substrate is S iN or S i3N*. An X-ray exposure mask characterized by being made of SiC, BN, polyimide resin, or a combination thereof. 7) In a sputtering apparatus having a mechanism for adjusting the gas flow rate and gas pressure of a rare gas, a first step of placing a sample equipped with an X-ray mask substrate on a sample stage in a state electrically insulated from the ground potential; , a second process 451 for setting the gas flow rate and the gas pressure to predetermined values and forming a layer of high melting point metal on the X-ray mask substrate under the set conditions; and reacting to the high melting point metal layer. 1. A method for manufacturing an X-ray exposure mask, the method comprising: a third step of forming an X-ray absorber layer with a desired pattern by subjecting the layer to an X-ray absorber layer. 8) A method for manufacturing an X-ray exposure mask according to claim 7, wherein the high melting point metal is tantalum or tungsten. 8) In the method for manufacturing an X-ray exposure mask according to claim 8, in the third step, a resist pattern is formed on the high melting point metal layer M made of tankle or tungsten, and the resist pattern is masked. As, CBr
A method for manufacturing an X-ray exposure mask, comprising the step of forming an X-ray absorber layer having the desired pattern by performing reactive spuck etching using F3 gas. 10) In the method for manufacturing an X-ray exposure mask according to claim 9, the third step includes forming a silicon oxide layer or a silicon nitride layer on the high melting point metal layer of tantalum or tungsten; A resist pattern is formed on the silicon oxide layer or silicon nitride layer, and the silicon oxide layer or silicon nitride layer is processed by reactive sputter etching using the resist pattern as a mask to form a pattern of the silicon oxide layer or silicon nitride layer. , using the pattern as a mask, the CBrF3
A method for manufacturing an X-ray exposure mask, comprising the step of performing reactive sputter etching with a gas to form the X-ray absorber layer in the desired pattern. 11) In the method for manufacturing an X-ray exposure mask according to claim 9, the third step includes coating a polymer layer with excellent dry etching resistance on the high melting point metal layer made of tantalum or tungsten. Then, a resist pattern is formed on the polymer layer, titanium or chromium is vapor-deposited on the resist pattern E, and a titanium or chromium pattern is formed by lift-off, and oxygen gas is applied using the titanium or chromium pattern as a mask. A polymer pattern is formed by reactive nupatta etching using CBrF.
A method for manufacturing an X-ray exposure mask, characterized in that the X-ray absorber having the desired pattern is formed by reactive sputter etching using three gases. 12. The method for manufacturing an X-ray exposure mask according to any one of claims 7 to 11, characterized in that the rare gas is one of xenon, argon, or krypton. A method for manufacturing an X-ray exposure mask. 13) x! according to any one of claims 7 to 12! i. A method for manufacturing an X-ray exposure mask characterized by each of the high melting points obtained in the second step. 14) In the method for manufacturing an X-ray exposure mask according to claim 13, at least a side of the high melting point metal layer on the side of the X II f substrate has granular crystal grains. Manufacturing method for line exposure masks. 15) In the method for manufacturing an X-ray exposure mask according to any one of claims 7 to 14, in the first step, the sample is kept in a floating state with respect to ground potential. A method for manufacturing an X-ray exposure mask characterized by: 113) In the method for manufacturing an X-ray exposure mask according to claim 15, in the second step, the gas pressure is adjusted such that the surface of the sample has a floating potential of -tOV to -20V. A method for manufacturing an X-ray exposure mask, the method comprising adjusting the high-frequency power supplied to the sputtering device. 17) In the method for manufacturing an X-ray exposure mask according to any one of claims 7 to 14, in the first step, a DC bias potential of -10V to -20V is applied to the sample. A method for manufacturing an X-ray exposure mask characterized by: