JPS58200535A - Mask for x-ray lithography - Google Patents

Abstract

PURPOSE:To obtain the easy mask for X-ray lithography in a manufacturing process by forming a carbon film onto an X-ray mask substrate. CONSTITUTION:A SiN film 2 is formed onto a Si wafer 1. The carbon film 9 as a plating base is E gun-evaporated onto the SiN film. A polyimide film 4 is applied, and cured. An electron-beam drawing resist is applied, and resist patterns 5 are formed through exposure by electron beams. Ti 6 Is evaporated onto the whole surface in order to form an intermediate mask for etching polyimide. The resist is removed through a lift-off process, and a Ti mask is formed. Polyimide is etched while using Ti as a mask through an oxygen ion-beam etching. An X- ray absorber pattern made of Au is formed. A polyimide pattern is removed, the back of the Si wafer is etched lastly, and the X-ray mask is completed. The carbon film remains on the substrate, but the remaining can be ignored on practical use because the transmittance of the carbon film is higher than that of an Au film.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a mask structure in XIs phosphorography, which is effective in transferring fine patterns of 1 μm or less.

In the development of X-ray phosphorography technology, it goes without saying that establishing a technique for producing an X-ray mask that is practical and has sufficient mask competition is an important issue. Soft X* with a wavelength of 4 to 13 nm is usually used, but in order to obtain sufficient contrast in this wavelength range, an X1s absorber pattern of An having a film thickness of 1 to 8000 nm or more is formed. It is necessary. Moreover, in order to take advantage of the features of X-ray phosphorography, it is required that the inside lines of this absorber pattern be on the submicron order. This figure shows the formation process. For example, in 1980, nine publications were published in Japan, including the Japanese Journal of Japan.
Applied Fixtures (Jpn・J@APpH1Ph
yse), Volume 19, No. 11, 2311-2312
There is a similar diagram on the page. (1) A SiN film 2 is deposited on the (100)-oriented St wafer 1 by low-pressure CVD.
form. Ti/Au film as plating paste < 5o
A thick polyimide film (1.2 mm thick) 3 (the 'ri film is necessary as an adhesion reinforcing layer for forming the Au film), a thick polyimide film (1.2 mm thick) 4, and an electron beam resist are sequentially formed. A necessary resist pattern 5 is obtained by electron beam exposure. (2) Deposit Ti6 to form an intermediate mask for etching the polyimide film. A lift-off process removes the resist and forms a Ti mask. (3) Polyimide pattern 7 is formed by RF reactive sputter etching using Tl as a mask. (The X-ray absorber pattern 8 of 4- is formed by electroplating. (5) The polyimide pattern is removed, and the plating base Ata where there is no absorber pattern is removed by RF sputter etching. Finally, The back side of the St wafer is etched with a KOH solution to complete the X-ray mask.

However, it has become clear that such conventional mask manufacturing processes have the following 0° problem.

Usually, in the polyimide etching step of step (3) above, U-reactive sputter etching using oxygen as an etching gas is used. However, in this process, boliimi;
It is necessary not to etch the mucus of the subsnoring layer. If the Au film is etched in this step, the Ti film, which serves as an adhesive layer to the substrate, will be exposed and its surface will be oxidized. In this rounding step (4), it is not possible to electroplate the shape/turn due to the X-ray absorption of Au. Since the tAu film remains after etching the Au, plating is no longer possible, but as the amount of tAu film etched increases, the etched tAu film is deposited onto the sidewalls of the polyimide pattern. becomes remarkable.For this reason, An of (4) above
In the plating process, abnormal plating of the Au X* absorber pattern occurs, making it impossible to obtain a good Au absorber pattern.

Another solution is to increase the etching rate ratio of polyimide and Au. If the concentration of oxygen radicals is increased during etching, the speed ratio can be increased, but the rate of etching progressing isotropically increases, resulting in the formation of polyimide/cutters with vertical walls. It becomes difficult to increase the velocity ratio by reducing the ion acceleration energy instead of increasing the oxygen radical concentration.However, at present, the acceleration energy of 100 eV or less is sufficient to increase the ion intensity. electric tM,v
Since it is difficult to obtain an oxygen ion beam having a magnitude of M (for example, 1 mA/ctA) and having a uniform incident direction, this still poses a problem in a practical sense.

Another drawback of the prior art is the step (5) above.
The plating base of the i/A u must be removed.Usually, the T
I am etching i/Au, but this and my u (D
The X-ray absorber pattern is also etched at the same time.

The thickness of the X*a body of Au decreases, and the
The plated Au xm absorber has a problem in that the turn shape is damaged because the end of the ta-acceptance body is shaved diagonally.

An object of the present invention is to overcome these conventional drawbacks and provide an X-ray phosphorography mask that is easy to manufacture.

According to the present invention, the Xi! A mask for phosphorography, characterized in that a vertical elemental film is provided on the X-ray mask substrate.Xii! A mask for printing is obtained.

The present invention will be described below with reference to drawings showing embodiments.

Embodiment 1 FIG. 1112 shows an embodiment of the xsta collection pattern forming process of an X-ray mask. (1) On the SS wafer 1, approximately 1 μm thick Si is deposited by plasma CVD method.
A N film 2 is formed. Carbon film (100
0λ thickness) 9 is deposited with an E gun on the SIN film.

A polyimide film 4 having a film thickness of 1.2 μxttA degrees is spin-coated.

Cure treatment at a temperature of 250°C or higher. Electronic &! PMMA is applied to a thickness of 4500^ as a drawing resist, and a resist pattern 5 is formed by electron beam exposure. (2)
To form an intermediate mask for etching the polyimide, Ti (5ooA thick) 6 is evaporated over the entire surface. A lift-off process removes the resist and forms a Ti mask. (3) Etch the polyimide by oxygen ion beam etching using Tl as a mask. Accelerating voltage of 500v~1IILA/C-io7'
Under the etching conditions of ft flow density and sample chamber pressure of 2.times.10-'Torr, the etching rate is as shown in FIG. The carbon film is etched at a rate approximately twice that of the polyimide film, but CO1DLS is etched into volatile reaction products such as CO2, so even if the carbon film is etched, it will not touch the sidewalls of the polyimide. A conductive film will not be formed (・The etched carbon film surface will not lose its conductivity, so even if etching is continued after polyimide etching is completed, as long as the carbon film does not disappear) When etching the 1.2 μm polyimide of this example, 5 minutes of etching time is required, but if a 1000^ carbon film is provided, 30% oat (-etching time) is required. (4) Au(D X-ray absorber/(ri1,:.

One layer is formed by electroplating. (5) Remove the polyimide pattern and finally K the back side of S1 sea urchin/1-
The X-ray mask is completed by etching with an OH solution.

In the X-ray mask according to the present invention, a carbon film remains on the substrate, and since the carbon film has a transmittance of 140 to 20 times higher than Au1L for X-rays with a wavelength of 4 to 10λ, a carbon film with a thickness of about 1000^ is used. The thickness of the film is negligible for practical purposes. Said (5
), after removing the polyimide pattern, the entire surface may be irradiated with an oxygen ion beam to remove the carbon film where there is no Au absorber pattern, but in this case, the Au X-ray absorber pattern is also removed at the same time. You will be pushed to the side a little.

Embodiment 2 FIG. 4 shows another embodiment of the process for forming the An absorber pattern of the FiX-ray mask. (1) O8i with a thickness of about 111 m was formed on the Si wafer 1 by plasma CVD method.
A N film 2 is formed. 5t) I4/NHs flow rate ratio 0.8,
This SiN film Fi6 x 10”d was grown under the conditions of substrate temperature 250°C, high frequency power 150W, and sample chamber pressure ITorrO.
It has a tensile stress of yn /dl. A carbon film (1000^) 9 serving as a plating paste is deposited on the SiN using an E-gun. Since the carbon film has a compressive stress of ~4X10'dyn/cd, the stress of the X-ray mask substrate made of 8iN/C is reduced to the optimal tensile stress (~2X108dyn/cd).
/ai). A SIN film IO having a thickness of about 1.2 μm is formed by plasma CVD. When etched under the conditions of 81H47Nus flow rate ratio of 3, substrate temperature of 160°C, high frequency power of 150 W, and sample chamber pressure of ITorr, an SiN film with an etching rate ratio of about 7 compared to the SiN9M kite in reactive sputter etching using CF4 gas is produced. Obtainable. (2) PMA is applied to a thickness of 4500^ as an IK consonant beam drawing resist, and a resist pattern 5 is formed by electron beam exposure. (3) Etch SiN'Mli using PMMA as a mask by reactive sputter etching using the aforementioned CF4 gas. At this time, the carbon film is hardly etched. After etching, remove PMMA. (4) Au's X#! The absorbent body turf 8 is formed by electroplating.

(5) Remove the SiN pattern and finally St sea urchin...
The back side of the mask is etched with a KOH solution to complete the X-ray mask. When removing the SiN pattern, HF
/H20=1/30 bath solution is used, but since the etching rate of the SiN substrate is slow and the SiN film of the substrate is covered with a carbon film, there is no fear that the SiN substrate will be damaged.

As described above, according to the present invention, it is possible to obtain an X-ray phosphorography mask in which an Au absorber pattern having vertical walls and a practical and sufficient contrast F ratio is formed. By using a carbon film with high X-ray transmittance as a plating paste, the present invention has the following advantages compared to the conventional method: X-ray absorber (2) Polyimide or SiN that does not cause abnormal plating or smoothness during the turn plating process.
When forming spacer patterns for plating, etching can be performed under highly ionic conditions, making it easier to form patterns with vertical walls. 3) Step of removing metal paste 4) Does not damage the Au0 X-ray absorber pattern shape after plating.Also, by strictly optimizing the carbon film thickness, Excellent X that can reduce the actual stress on the edge mask substrate to zero
#! A mask for phosphorography can be realized.

[Brief explanation of drawings]

ts1 shows the manufacturing process of a conventional mask for X-ray phosphorography, and FIGS. 2 and 4 show the manufacturing process of a mask for X-ray phosphorography according to the present invention. FIG. 3 shows the etching rate of various materials with an oxygen ion beam. DESCRIPTION OF SYMBOLS 1... Support made of silicon, 2... X# mask substrate, 3... Plating base (for example, Ti/Atdl
), 4...Polyimide, 5...V') strike pattern, 6...Tt. 7... Polyimide spacer pattern, 8... X-ray absorber Au pattern, 9... Return element film, lO... Si
N/〆Sai 1 Figure 2 Figure River/3 Eye Σya IJ-Figure-165-

Claims (1)

[Claims] In an X# lithography mask consisting of a support made of Silylon, an X-ray mask substrate supported by the support, and an xm absorber pattern formed on the substrate, a carbon film is formed on the X-ray mask substrate. An X-ray shielding mask characterized by being equipped with