JP2007016294A - Ti-W target for sputtering - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sputtering target for forming a Ti-W film used as a diffusion preventing film of a semiconductor element.
SOLUTION: In mass%, Ti: 5 to 20%, oxygen: more than 0.1 to 1%, the balance is composed of W and inevitable impurities, and the oxygen is a base material as an oxide of titanium. Ti-W target for sputtering uniformly dispersed therein.
[Selection figure] None

Description

  The present invention provides an anti-diffusion film formed between an Au film and an Al electrode, which is formed under an Au bump electrode for mounting a semiconductor chip on a substrate, and prevents diffusion and reaction of Au and Al. The present invention relates to a sputtering Ti-W target.

In general, it is known that a film made of Ti—W (Ti: 10 mass%, composition of balance W) is used as a diffusion prevention film. For example, when a liquid crystal drive circuit is mounted on a substrate, a method is adopted in which an Au bump is produced by plating on the Al electrode on the circuit side, and this is thermocompression bonded to the substrate. In addition, a Ti-W film is used as a diffusion barrier film. If this Ti-W film does not function as a diffusion barrier film, Au and Al diffuse in the Ti-W film during heating for pressure bonding and react with each other to produce an intermetallic compound. If is generated, the electrical resistance of the portion increases or the adhesion decreases, which is not preferable.
This Ti-W film is generally formed by sputtering using a Ti-W target, and this Ti-W target is known to be produced by a method such as hot isostatic pressing (HIP) or vacuum hot pressing. ing.
The Ti-W target for forming this conventional Ti-W film contains a large amount of oxygen, and when a Ti-W film is formed by sputtering using a target containing a large amount of oxygen, The release of oxygen causes cracks in the target, resulting in oxidation of the produced film and variations in film quality, which is not preferable. Therefore, a method for producing a target using hydrogenated Ti as a raw material has also been proposed. However, when sputtering is performed using a target containing a large amount of hydrogen, the surface of the target becomes high during sputtering, and the hydrogen dissociates and particles are produced. Occurs, which causes a decrease in the yield of semiconductor devices. Therefore, a Ti—W target containing hydrogen: 5 ppm or less and oxygen: 1000 ppm or less with a low hydrogen and oxygen content is considered preferable (see Patent Document 1).
Furthermore, it is also known that a reaction sputtered film of TiW (N, O) in an Al (bond pad) / TiW / Au coating improves the properties of the diffusion barrier by a considerable size (see Patent Document 2). .
JP 7-70744 A JP-T 8-512435

  As shown in Patent Document 2, it is known that a Ti-W film containing oxygen is more preferable as a diffusion prevention film between Al (bond pad) and Au film. When a Ti-W film is formed by sputtering using a Ti-W target containing a large amount of oxygen, a Ti-W film containing a large amount of oxygen cannot be formed with good yield due to cracking during sputtering. . On the other hand, a Ti-W target with a low oxygen content does not generate cracks during sputtering, but a Ti-W film with a low oxygen content is formed. There is a problem that it does not function sufficiently as a diffusion barrier film between the two.

  Therefore, the present inventors produced a Ti—W target that does not generate cracks during sputtering even if it contains a large amount of oxygen, and this Ti—W target is effective as a diffusion prevention film between Al and Au. Research was conducted to obtain a Ti-W film containing a large amount of oxygen. As a result, even if the target contains more than 0.1% by mass of oxygen, the target containing oxygen dispersed in the substrate as titanium oxide is cracked even during sputtering. Thus, the inventors have obtained the knowledge that a Ti—W film containing a large amount of oxygen and having an excellent diffusion preventing function can be formed.

  The present invention has been made on the basis of such knowledge, and contains, in mass%, Ti: 5 to 20%, oxygen: more than 0.1 to 1%, and the balance consisting of W and inevitable impurities. The oxygen is characterized by a sputtering Ti-W target that is uniformly dispersed in the substrate as an oxide of titanium.

  In the Ti-W target for sputtering of the present invention, the reason for limiting Ti to 5 to 20% by mass is that if Ti is less than 5% by mass, the adhesion with the Al wiring and the surrounding protective film is not sufficient and not preferable. On the other hand, if the Ti content exceeds 20% by mass, the electrical resistance becomes too high and the barrier property is further lowered, which is not preferable. In the Ti—W target for sputtering according to the present invention, a more preferable range of the Ti content is 8 to 15% by mass.

  In the Ti—W target for sputtering of the present invention, oxygen is limited to more than 0.1 to 1.0 mass% because sufficient diffusion between Al and Au is achieved even if oxygen is contained by 0.1 mass% or less. Since a Ti-W film having a barrier property cannot be obtained, it is not preferable. On the other hand, if the content exceeds 1.0% by mass, the oxygen content is excessive and abnormal discharge and abnormal particles are generated excessively during sputtering. Or the electric resistance of the resulting Ti-W film is increased, which is not preferable.

In order to produce the Ti—W target for sputtering of this invention, the raw material powder is Ti powder having an average particle diameter of 1 to 40 μm, W powder having an average particle diameter of 0.5 to 20 μm, and an average particle diameter of 0.5. ˜20 μm TiO powder, average particle size: 0.5-20 μm Ti ₂ O ₃ powder, average particle size: 0.5-20 μm TiO ₂ powder are prepared. -20%, oxygen: 0.2 to 1%, the balance is weighed so as to have a composition consisting of W and inevitable impurities, mixed to produce a mixed powder, and the resulting mixed powder contains carbon Manufactured by filling a mold, producing a sintered body by vacuum hot pressing under conditions of pressure: 10-40 MPa, temperature: 1000-1500 ° C., and machining the obtained sintered body into a predetermined shape To do.

  According to the TiW target of the present invention, it is possible to form a Ti-W film having a large oxygen content having an excellent function as a diffusion prevention film between Al and Au without causing cracks during sputtering. Can greatly contribute to the development of

Best Mode for Carrying Out the Invention

As raw material powders, Ti powder having an average particle diameter of 15 μm, TiO ₂ powder having an average particle diameter of 5 μm, and W powder having an average particle diameter of 1 μm were prepared. These raw material powders are blended in the proportions shown in Table 1, filled in a ball mill and mixed, and the resulting mixed powder is filled into a graphite mold, under the conditions of pressure: 15 MPa, temperature: 1200 ° C., and holding for 3 hours. A hot press sintered body was produced by vacuum hot pressing.
The obtained hot-press sintered body was machined to have a diameter: 152.4 mm, a thickness: 6 mm of the present invention Ti-W target (hereinafter referred to as the present invention target) 1 to 9 and a comparative Ti-W target (hereinafter referred to as the target). 1 and 2 and a conventional Ti-W target (hereinafter referred to as a conventional target) 1 were prepared. In addition, the components of the present invention targets 1-9, comparative targets 1-2, and conventional target 1 were subjected to composition analysis using an electron beam probe microanalyzer (EPMA), and the results are shown in Table 1.
Furthermore, as a result of observing the cross-sectional structure of the target with a scanning electron microscope, it was confirmed that titanium oxide particles were uniformly dispersed in the substrates of the present invention targets 1-9 and comparative targets 1-2, In the conventional target 1 substrate, titanium oxide particles could not be observed.

Next, the present invention targets 1-9, comparative targets 1-2, and the conventional target 1 are soldered to a 10 mm-thick oxygen-free copper cooling plate using In solder, and then attached to a normal high-frequency magnetron sputtering apparatus. The following conditions,
Substrate: Si wafer with an oxide film (100 nm) having a diameter of 152 mm,
Distance between substrate and target: 60mm,
Power: DC 650W,
Atmosphere: Ar atmosphere (2.0 Pa),
Substrate temperature: room temperature,
A Ti—W thin film having a thickness of 300 nm is formed on the Si wafer as the substrate by sputtering, and particles having a diameter of 0.5 μm or more on the Si wafer are measured by a foreign substance inspection apparatus. It is shown in Table 1. Since the present invention targets 1 to 9 and the comparative targets 1 to 2 contain oxygen as an oxide of titanium during the sputtering, cracks do not occur during the sputtering, and the amount of oxygen contained in the conventional target 1 is Since it was extremely small, no cracks occurred during sputtering.
Furthermore, the specific resistance of the obtained Ti—W thin film was measured, and the result is shown in Table 1.

Furthermore, using the present invention targets 1-9, comparative targets 1-2 and conventional target 1, and commercially available Al and Au targets, Al was deposited on an Si wafer with an oxide film (100 nm) having a diameter of 152 mm under the following conditions. (500 nm) → Ti—W (150 nm) → Au (100 nm) The film was continuously formed without breaking the vacuum, and the produced wafer with the laminated film was left on a hot plate at 350 ° C. for 10 hours. The surface of the film was observed with an optical microscope with a magnification of 25 ×, and the number of intermetallic compounds produced by the reaction of Al and Au confirmed in the visual field of the 25 × metal microscope was measured. It was shown in 1.
Ti-W sputtering conditions:
Distance between substrate and target: 60mm,
Power: DC 650W,
Atmosphere: Ar atmosphere (2.0 Pa),
Substrate temperature: room temperature,
Al sputtering conditions:
Distance between substrate and target: 60mm,
Electric power: DC 4000W,
Atmosphere: Ar atmosphere (0.2 Pa),
Substrate temperature: room temperature,
Au sputtering conditions:
Distance between substrate and target: 60mm,
Power: DC 650W,
Atmosphere: Ar atmosphere (0.2 Pa),
Substrate temperature: room temperature,

  From the results shown in Table 1, the Ti—W thin films produced with the inventive targets 1 to 9 were substantially identical in comparison with the Ti—W thin film produced with the conventional target 1, although the specific resistance was the same. Since the Ti-W thin films produced with the targets 1 to 9 have a higher oxygen content than the Ti-W thin film produced with the conventional target 1, the number of intermetallic compounds produced by the reaction between Au and Al is small. It can be seen that the Ti—W thin films prepared with the inventive targets 1 to 9 have an excellent function as a diffusion preventing film as compared with the Ti—W thin film prepared with the conventional target 1. Furthermore, it can be seen that comparative targets 1 and 2 having compositions outside the scope of the present invention show undesirable results.

Claims (1)

In mass%, Ti: 5 to 20%, oxygen: more than 0.1 to 1%, the balance is composed of W and inevitable impurities, and the oxygen is uniformly dispersed in the substrate as an oxide of Ti A Ti—W target for sputtering, characterized in that