Nippondenso Co., Ltd.

Takao Yoneyama

Ichiharu Kondo

Masami Yamaoka

Osamu Takenaka

Yasunori Taga

Hisayoshi Fujikawa

Kenji Kondo

Takeshi Ohwaki

Katsuhiro Izuchi

Hiroyuki Okada

Disclosed is a nickel layer formed on a substrate by sputtering, in which nickel layer a percent ratio of an X-ray diffraction peak intensity of the (200) plane of the nickel layer to that of the (111) plane of the nickel layer is not less than 10%. This nickel layer has a reduced stress, and therefore, lessens a bending of a substrate. The nickel layer is formed by a process for sputtering nickel on a substrate, comprising supplying an argon gas into a vacuum chamber, adjusting a pressure of the argon gas in the vacuum chamber to a predetermined value, ionizing the argon gas, bombarding a target containing nickel with the ionized argon gas, to sputter nickel atoms, and depositing the sputtered nickel atoms onto the substrate, wherein the predetermined pressure of the argon gas is not lower than 12 mTorr.

Sputter-deposited nickel layer

Fluxless soldering process

Surface treated structure for solder joint

A method for forming electrodes with strong adhesion strength for a semiconductor device is provided. The adhesion strength between a Si substrate and a Ti film is made higher than the pulling stress of a Ni film. Before an electrode is formed using sputtering process, the natural oxide film grown on a semiconductor substrate is removed using an Ar reverse sputtering while the top surface of the silicon substrate is converted to an amorphous through a bombardment and introduction of Ar. While Ti is deposited, a Si-Ti amorphous layer is formed in the Si/Ti interface. In this case, the amount of Ar atoms is controlled less than 4.0.times.10.sup.14 atoms/cm.sup.2. The Ar amount also can be controlled by adjusting the conditions such as the output or cathodic voltage of Ar reverse sputtering and decreasing the absolute value of Ar in the amorphous Si layer. Also the Ar amount can be controlled by diffusing Ar atoms into the substrate at more than about 300.degree. C. during Ti film deposition to diverse the Ar distribution. As a result argon atoms which concentrates at the interface do not affect with respect to the Si-Ti amorphous layer, whereby the bonding strength of the amorphous layer is maintained. Therefore, the strong adhesion strength between Si and Ti can provide a sufficient durability against the film stress of the Ni film.

Method of forming electrodes of semiconductor device

A fluxless soldering process comprising the steps of: preparing first and second members to be bonded by soldering, the first member having a bonding surface with a higher solder-wettability and the second member having a bonding surface with a lower solder-wettability; placing the second member with the bonding surface thereof facing upward, a solder foil on the bonding surface of the second member, and the first member on the solder foil and with the bonding surface thereof facing downward, to form an assembly; heating the assembly in a reducing atmosphere to fuse the solder foil, thereby forming a molten solder between the first and second members; and cooling the assembly to solidify the molten solder, thereby bonding the first and second members.

Growing community of inventors

Anpachi-gun, Japan

Takao Yoneyama