JPH0323630B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to silicon, particularly nichrome-based sputtering targets containing a high concentration of silicon. In particular, the present invention relates to sputtering targets for producing resistive thin films used as electronic components.

Most of the current highly accurate standard resistors are manganin (86Cu-12Mn-2Ni), Karma (73Ni-20Cr-7Al+Fe), and nicrotal (75Ni).
This is a wire-wound resistor using precision resistance wire such as -17Cr-8Mn+Si). Metal film resistors are precision resistors second only to wire-wound resistors, and have the advantage of being small and easily achieving high resistance. Generally, the following conditions are required for thin film materials used in resistors.

It must have an appropriate specific resistance value, it must have a small temperature coefficient, it must be stable against atmospheric gases, it can be easily deposited, and its composition can be precisely controlled. Ni-Cr alloy has a high specific resistance, and its oxide film is dense and has excellent heat resistance, but its temperature coefficient is as large as 100 to 150 ppm/℃, so when used as a resistive thin film, Al, Si, etc. are usually used. It is used after adding it and adjusting the temperature coefficient.

Conventionally, vacuum evaporation has been commonly used as a method for producing metal films, but when using a vacuum evaporation method, a large compositional discrepancy occurs between the evaporation material and the formed film when an alloy of metals with different vapor pressures is used. In order to form a film with high precision, advanced film management is required, making it difficult to perform production efficiently. In recent years, advances in magnetron sputtering technology have made it easier to form highly accurate films, and sputtering has come to be used more frequently in place of vacuum evaporation. The target for the resistive thin film used for this purpose is approximately
Alloy targets with a Ni/Cr ratio of 50/50 and 1 to 7% Si added are used, and with these targets, high precision resistors with medium resistance up to an initial resistance of about 500 Ω can be manufactured. However, it is difficult to manufacture a high-resistance target with an initial resistance of 500 Ω or more with high precision, and to do so, it is necessary to use a target with a high specific resistance.

In general, the conditions required for a sputtering target are that it can be easily processed into a plate shape, that it is dense with close to theoretical density and does not absorb gas, that it has a uniform composition, and that it is easy to control the composition as an alloy. It is necessary to have something that will not cause warping, cracking, etc. when power is turned on.

Currently, materials such as CrSi and Cr-SiO are considered as materials for high resistance, but it is difficult to make highly accurate resistive thin films with these materials, and there are problems with stability. In addition, these materials are difficult to process as targets, and it is extremely difficult to process those with a high Si content by the melting method because problems such as cracks occur during production, and in such cases, the sintering method is usually used. Processed into a target by However, sintered products have problems such as gas generation during sputtering and cracking when power is turned on, so that they have not been put into practical use at present.
On the other hand, it is known that when Si is added to a Ni-Cr alloy, the specific resistance increases as the amount added increases, and a nichrome target with a high Si content has potential as a high-resistance target. However, as mentioned above, it is said to be extremely difficult to make these materials by melting, and in reality, as mentioned above, it is difficult to make them at most.
Only about 7% Si exists. As a result of various studies on nichrome targets, the present inventors found that
The present invention has been completed by finding a target suitable for use as a resistive thin film, which has a Si content, has no internal defects, has high density, and does not crack during handling.

That is, the present invention has Ni70-10%, Cr70-10%,
This invention relates to a high silicon nichrome sputtering target containing 15-30% Si. It has also been found that this target can be obtained by extremely gradual cooling in the temperature range from the solidification start temperature to room temperature during melting and casting. Next, the present invention will be explained in detail.

The alloy raw materials for target production are melted by conventional melting methods such as plasma arc, induction furnace, and electric arc furnace. Ni, Cr, as melting raw materials
Si may be obtained by electrolysis or other smelting methods, but Ni and Cr are preferably obtained by electrolysis in terms of purity. The melting atmosphere is carried out in a vacuum or an inert gas atmosphere to prevent oxidation of the metal. If Si is less than 15%, it is difficult to obtain a high resistance material, and if it is more than 30%, it is difficult to obtain a material with high density and no internal defects. Also, the composition of Ni and Cr is 70
In a composition range outside of ~10%, casting defects are unavoidable and it is difficult to obtain a product without cracking. It is preferable to heat the casting mold in advance.

The alloy is solidified from a molten state and slowly cooled to room temperature, but in order to obtain the target of the present invention, this slow cooling step is characteristically carried out very slowly.

That is, it is slowly cooled at a rate of 1° C./min or less. If the slow cooling rate is higher than this rate, cracking of the product may occur, which is undesirable.

Next, the present invention will be explained in detail with reference to Examples.

Example 1 A high-frequency melted alloy with a composition of 54% nickel, 26% chromium, and 20% silicon was cast in a ceramic mold heated to 900°C, and the temperature was 1°C/1°C after casting.
Cooling was performed at an average cooling rate of min. The molten ingot was ground into a target of 5 inches x 15 inches x 1/4 inch, but no cracks or cavities were observed. In addition, a 2m/m copper plate was brazed to this target and a high rate sputter was applied to the target with an argon gas pressure of 6×10 ^-3 torr and an output of 2.5KW.
Even after 10 minutes of film deposition, no cracking occurred and initial resistance was achieved.
We were able to obtain a highly accurate resistor thin film with a 600Ω resistance temperature coefficient within ±50ppm/°C.

Example 2 A target was prepared in the same manner as in Example 1 with a composition of 40% nickel, 40% chromium, and 20% silicon. No cracks or casting defects were observed during manufacturing for this target, and the initial resistance was 1KΩ with a temperature coefficient of resistance ±
It was possible to obtain a resistive thin film within 70 ppm/°C.

Example 3 A target was prepared in the same manner as in Example 1 with a composition of 40% nickel, 30% chromium, and 30% silicon. Regarding this target, cracks during production,
No casting defects were observed, and a resistive thin film with an initial resistance of 1 KΩ and a temperature coefficient of resistance of ±85 ppm/°C was obtained.

Claims (1)

[Claims] 1 After melting and casting an alloy consisting of 70-10% nickel, 70-10% chromium, and 15-30% silicon, 1
Nickel 70~10%, chromium 70~10%, silicon 15~10%, characterized by slow cooling at a rate of ℃/min or less
A method for producing a high silicon nichrome sputtering target comprising 30% silicon.