JPH07278805A - Production of low oxygen silicon nitride sputtering target - Google Patents

Abstract

PURPOSE:To obtain a low-oxygen silicon nitride sputtering target with which a silicon nitride thin film having a low oxygen content. is obtd. since the amt. of oxygen in the target is small. CONSTITUTION:In the production method of the low-oxygen silicon nitride sputtering target, a metal silicon powder is granulated with an org. binder, press formed, then dried, and heat treated at 1250-1350 deg.C for one or more hours under reduced pressure of <=1Torr. Then the target is nitrided in nitrogen gas or a mixture gas of nitrogen and hydrogen at 1350-1700 deg.C.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a low-oxygen silicon nitride sputtering target, and more particularly to a low-oxygen nitriding film which reduces the amount of oxygen in the film and provides a silicon nitride thin film excellent in high energy beam irradiation resistance. The present invention relates to a method for manufacturing a silicon sputtering target.

[0002]

2. Description of the Related Art Silicon nitride thin films obtained by sputtering silicon nitride have many industrial uses, and are expected to be promising for future lithography technology, especially with the miniaturization of pattern formation in semiconductor devices. Among these, the mask X-ray transparent film used for X-ray lithography has a) a smooth surface, no scratches or pinholes, and practical strength. B) High-precision alignment (positioning). ) Has the necessary visible light transmittance, c) has good chemical resistance and moisture resistance, and is not easily damaged by the etching and cleaning processes, d) like high-energy electron beams and synchrotron radiation. It is required to withstand the irradiation of a high energy beam.

However, as a conventionally known sputtering target member of silicon nitride, 1) silicon nitride powder, 2) a powder compacted by cold or hot pressing of silicon nitride powder, 3 It was only known that a metal oxide such as Y ₂ O ₃ , MgO, Al ₂ O ₃ or CoO was added and sintered as a sintering aid.

[0004]

However, among the known sputtering targets of silicon nitride, the powder compacts obtained by pressure molding 1) silicon nitride powder and 2) silicon nitride are silicon nitride. The bond between the elementary powders is very weak, and the particles may be charged during sputtering and electrostatically repelled, which may cause them to be ejected onto the counter substrate and cause defects in the thin film.
In the product obtained by adding and sintering the metal oxide of 3), since this oxide is mixed as an impurity, the sputtering efficiency is lowered, and the quality of the formed thin film is affected. Since oxygen is mixed in with, there is a drawback that the high energy beam irradiation resistance deteriorates. (Arakawa et al .: Proc. Of the 53rd JSAP, Academic Lecture, No.2
(1992), P.49, Arakawa et al .: Proceedings of the 40th Japan Society of Applied Physics, Academic Lecture, No.2 (1993), P.50)

[0005]

The present invention relates to a method for producing a low-oxygen silicon nitride sputtering target which solves the above disadvantages and drawbacks, and it is press molding after granulating metal silicon powder with an organic binder. It is then dried and then heat-treated at a reduced pressure of 1 torr or less at 1,250 to 1,350 ° C for 1 hour, and then nitrided at 1,350 to 1,700 ° C in nitrogen gas or a mixed gas of nitrogen and hydrogen. To do.

That is, the present inventors have conducted various studies to develop a method for producing a silicon nitride sputtering target which gives a silicon nitride thin film having a low oxygen content and thus having a high resistance to high energy beam irradiation. The silicon powder is granulated using an organic binder, press-molded, heated at high temperature under reduced pressure to deoxidize, and then heated in nitrogen gas or a mixed gas of nitrogen gas and hydrogen gas. When silicon nitride is used for nitriding, it has an oxygen content of 0.2 wt% or less, so it was found that the silicon nitride thin film formed from this has excellent irradiation resistance to high energy beams. The present invention has been completed by conducting research on the type of silicon metal, heating conditions, nitriding conditions, and the like. This will be described in more detail below.

[0007]

The present invention relates to a method for producing a low-oxygen silicon nitride sputtering target. As described above, the metal silicon powder is granulated with an organic binder, press-molded, and dried under reduced pressure of 1 torr or less. 1,250〜
Heat treatment at 1,350 ° C for 1 hour or more, and then heat this in nitrogen gas or a mixed gas of nitrogen and hydrogen from 1,350 to
It is characterized by nitriding at 1,700 ° C. According to this, the silicon nitride obtained here has few impurities and the oxygen content is small, for example 0.2 wt% or less. The silicon nitride thin film obtained by sputtering has practical strength, high visible light transmittance, good chemical resistance, and has the advantage that it can withstand irradiation of high energy beams. Given.

The method of manufacturing the low oxygen silicon nitride sputtering target of the present invention is performed by using metal silicon as a starting material. It is preferable that this silicon metal be as high in purity as possible because it will also affect the physical properties of the silicon nitride thin film obtained by the sputtering method from the silicon nitride target produced from this when it contains impurities. This may be 99.5% or more, for example. Further, the finer the particle size of this material is, the more advantageous it is to promote the nitriding described later.
It is preferable that the thickness is about μm.

This metal silicon is first kneaded with an organic binder and granulated, and then pressed into a plate-like body.
Polyvinyl alcohol, methyl cellulose, methyl acrylate, etc. may be used as the organic binder, and a granular material having a particle size of 0.3 to 1 mm is formed by press molding to obtain a 150 × 150 × 8 mm plate. Good. The press-molded body thus obtained is then heated under reduced pressure. According to this, the oil and fat adhering to the surface of Si is degreased, and the surface of Si is depressurized and heated. Perhaps because some oxygen is discharged outside the furnace as SiO, this silicon metal has a low oxygen content.

In this case, it is necessary to reduce the depressurization to 1 torr or less, and if the heating is performed at less than 1,250 ° C., oxygen cannot be completely exhausted. Since this causes an adverse effect, it is necessary to set the temperature to 1,250 to 1,350 ° C., and the heating time is also required to be 1 hour or more because the oxygen gas cannot be exhausted if the heating time is less than 1 hour.

The compact thus treated is nitrided to turn the silicon metal into silicon nitride, which is nitrided in nitrogen gas or in a mixed gas of nitrogen and hydrogen for 1,350. It suffices to sinter at ~ 1,700 ° C. This will nitridize silicon into silicon nitride with a low oxygen content, so after cutting this with a cutting machine such as a diamond cutter, finish it. Then, a silicon nitride sputtering target having a predetermined shape can be obtained.

Since the silicon nitride sputtering target produced in this manner has an oxygen content of 0.2% by weight or less, the silicon nitride thin film obtained by sputtering the same naturally has an oxygen content of less than 0.2% by weight. This is advantageous because it is less likely to be irradiated, and thus it has excellent resistance to irradiation of a high energy beam such as a high energy electron beam or synchrotron radiation.

[0013]

EXAMPLES Next, examples and comparative examples of the present invention will be described. Example Purity 99.5%, average particle size 5 μm, BET specific surface area 2 m ²
28 parts by weight of a 7% aqueous solution of polyvinyl alcohol is mixed with 100 parts by weight of a commercially available metal silicon powder (/ g), and this is granulated with a granulator into granules having a particle diameter of 0.5 mm and dried. Without using a mold of 150 × 150 mm, press molding was performed at a pressure of 1 t / cm ² to form a flat plate of 150 × 150 × 8 mm, and then dried.

Then, the molded body is put into a decompression furnace, the temperature inside the furnace is reduced to 1 torr or less, the temperature rise is started, and after reaching 1,300 ° C., the temperature is maintained for 1 hour. After natural cooling, this is a box furnace. It was charged into a furnace, gradually heated up in a nitrogen gas atmosphere, held at 1,700 ° C for 1 hour for nitriding and sintering.
0.16% by weight of silicon nitride was obtained.

Next, this silicon nitride was cut into a disk shape having a diameter of 100 mm and a thickness of 5 mm ⁺ with a diamond cutter, heat-treated in a vacuum atmosphere at 1,500 ° C. for 1 hour, and then bonded to a copper plate to bond silicon nitride. We made a sputtering target, heated it to 800 ° C with an incident power of 1kw at 3.0 × 10 ^-2 torr, and sputtered 3 ”φ × 600.
A silicon nitride thin film with a thickness of 1.0 μm was prepared on a Si substrate of μm, and the amount of oxygen in this film was measured.
It was × 10 ²⁰ atoms / cm ³ , and even when irradiated with a high-energy electron beam, there was no change in thermal stress or visible light transmittance, and there was no deterioration at all.

Comparative Example However, for comparison, this silicon nitride was used as a commercially available silicon nitride (Si ₃ N ₄ ) 1 having a purity of 99.5% and an average particle size of 0.60 μm.
When 10 parts by weight of Y ₂ O ₃ -Al ₂ O ₃ was added as a sintering binder to 00 parts by weight and sintered at 1,700 ° C., this had an oxygen content of 3.31% by weight. Using a silicon nitride sputtering target obtained by the same treatment, a silicon nitride thin film was formed by the same method as in the example, and the amount of oxygen in this film was measured. It was 3.0 × 10 ²⁰ atoms /
cm ^3, and this compound when irradiated with high energy electron beam thermal stress ² × 10 ⁹ dyn / cm 2 was changed to the compression side, also visible light transmittance was decreased by 5%.

[0017]

As described above, the present invention relates to a method for producing a low-oxygen silicon nitride sputtering target, in which a metal silicon press-formed product is heated under reduced pressure to be deoxygenated, and then this is deoxidized. This is a nitriding silicon nitride sputtering target. According to this, the silicon nitride sputtering target can be made to have a low oxygen content. Therefore, a silicon nitride thin film obtained by sputtering this Can also have a low oxygen content, thus providing the advantage that it can be resistant to high energy beam irradiation.

Claims (1)

[Claims] 1. A metal silicon powder is granulated with an organic binder, press-molded, dried and then under reduced pressure of 1 torr or less.
Heat treatment at 1,250-1,350 ℃ for 1 hour or more, and then heat this in nitrogen gas or mixed gas of nitrogen and hydrogen.
A method for manufacturing a sputtering target made of low-oxygen silicon nitride, which comprises nitriding at 1,350 to 1,700 ° C.