CN108517497B

CN108517497B - Method for preparing NiPt alloy target material by centrifugal forming

Info

Publication number: CN108517497B
Application number: CN201810157024.6A
Authority: CN
Inventors: 毕珺; 闻明; 沈月; 宋修庆; 熊庆丰
Original assignee: Sino Platinum Metals Co Ltd
Current assignee: Yunnan Precious Metals Laboratory Co ltd
Priority date: 2018-02-24
Filing date: 2018-02-24
Publication date: 2020-10-30
Anticipated expiration: 2038-02-24
Also published as: CN108517497A

Abstract

The invention discloses a method for preparing a NiPt alloy target material by centrifugal forming, and relates to a method for preparing a thin plate NiPt alloy target material by using a centrifugal forming casting process, so that destructive influence caused by stress processing of cast ingots is avoided, the production process is simplified, the purity of product materials is ensured, and the yield of products is greatly improved. When the composition ratio of the NiPt alloy enters the range of 40-90 wt.% Pt, the system can generate ordered transformation, and the formed ordered structure can greatly weaken the stress processing performance of the alloy. The rotary heating platform and the specially designed mould are used for casting, so that the shape of the cast ingot is close to the shape of a product, the final size can be achieved through simple machining, a qualified product is manufactured, and the problem of extremely high rejection rate when the traditional stress processing method is used for processing the product in the composition interval is successfully solved.

Description

Method for preparing NiPt alloy target material by centrifugal forming

Technical Field

The invention provides a special preparation method for a NiPt alloy target material in a Pt component range of 40-90 wt.%, so that the extremely high rejection rate caused by stress processing is avoided, the production process is simplified, the purity is ensured, and the quality and the yield of the target material are improved.

Background

At present, after the semiconductor Integrated Circuit (IC) industry enters 65nm and 45nm technical nodes, titanium silicide and cobalt silicide (90nm and above) are replaced by NiPt-silicide contacts prepared from nickel and nickel alloy targets due to the limitation of line width effect, and become the most commonly used silicide; the nickel silicide prepared by the sputtering process using the NiPt alloy as the target has the advantages of wireless wide benefit and bridging phenomenon, small film resistance and leakage current, capability of enabling fewer silicon atoms to migrate due to low-temperature annealing, small residual stress in the film and the like, and is applied to the fields of Schottky diodes (SBDs), complementary metal oxide semiconductor devices (CMOS), Field Effect Transistors (FETs), integrated circuits and the like. The addition of Pt during NiSi formation can reduce or eliminate encroachment defects, Ni-5 at.% Pt has been successfully applied in 65nm technology, Ni-10 at.% Pt in 45nm technology, along with semiconductor device linesWith further reductions in width, higher Pt content NiPt is required to produce ni (Pt) Si contact films; meanwhile, Pt is used as a non-magnetic element, and the improvement of the content of Pt in the target material is beneficial to the improvement of the magnetic Permeability (PTF) of the target material and the increase of the sputtering efficiency. Documents [1 to 7]]The mass preparation method of the NiPt target material is disclosed, the Ni and Pt element proportion covers the whole range of 1-99 wt.%, and the processing method is the traditional cold-hot plastic deformation such as rolling and forging. However, the inventor finds that in the production and development work of actual NiPt alloy target materials, when the content of Pt is in a certain specific range (40-90 wt.%), the processability of the alloy is suddenly deteriorated or even completely disappeared, the whole ingot blank is full of cracks or even totally collapses by applying small strain, and the similar situation is not met outside the composition range; this phenomenon is distinguished from the fracture of hard brittle matrices, since the ingot, when subjected to microhardness tests, is found to have very good plasticity in a small local range and very low hardness (which is consistent with the basic properties of nickel platinum). In-depth research shows that the thermodynamic equilibrium phase diagram of binary alloy shows that when the content of Pt is in the range of 40-90 wt%, the system is subjected to component separation at medium and low temperature to generate Ni₃Two ordered structures of Pt and NiPt; in practical situations, we find that these ordered phases will be grown at the grain boundaries and distributed along the grain boundaries in the form of fine particles, which drastically weakens the bond between the grain boundaries and the grain boundaries; when the ingot is subjected to a small stress from a certain direction, the plastic deformation of the matrix is even delayed to start (or the yield stress is not reached), the grain boundary can quickly slide and generate cracks, and the cracks quickly propagate along the weakened grain boundary and quickly penetrate through the whole ingot. The nickel alloy is easily oxidized and when the system is oxidized, the grain boundary is also a preferential oxidation place, and then the oxide is distributed along the grain boundary to further weaken the combination between the grain boundaries, which explains the reason that the ingot is subjected to the atmospheric annealing in the actual work so that the processability is further deteriorated. The NiPt target products used at present are all thin plate-shaped pieces, the thickness is about 2-8mm according to different requirements, the width size is about 600mm at most, and the shape cannot be realized by the conventional casting method, but the shape is realized in practiceIn the actual production work, the rejection rate of the alloy product ingot blank in the composition range of (40-90 wt.% Pt) is up to more than 95% when the alloy product ingot blank is processed by the conventional processing means such as rolling or forging mentioned in the above documents; meanwhile, the crystal boundary is easy to generate cracks, and the fresh cracks are also positions which are firstly oxidized and polluted by gas impurities, so that the internal defects of the target product are increased rapidly, and the purity is greatly reduced.

Aiming at the problems of the NiPt target material products in the component range, the invention designs a special fusion casting method for the thin plate piece, strives to reduce the stress processing process as much as possible, reduce the rejection rate of the product, avoid the heat treatment process which is easy to cause oxidation, and improve the purity.

Disclosure of Invention

The invention aims at the characteristic of non-stress processability of NiPt alloy in the (40-90 wt.% Pt) component range (ordered structure transformation region), and aims to provide a special casting method, which mainly relates to the design of a casting mold and a casting method, so that an ingot is closer to the shape of a final product, the stress processing process is reduced, reoxidation caused by heat treatment is avoided, and the yield of nickel-platinum target products is improved.

The typical component of the nickel-platinum alloy target material related by the invention is 40-90 wt.% Pt, in the interval, the alloy system has ordered transformation, and the formed ordered structure can greatly weaken the stress processing performance of the alloy, so that the casting shape is close to the product shape by controlling the casting process and skillfully designing a casting mould and a centrifugal molding casting method, the stress processing procedure and the matched heat treatment annealing procedure are reduced as much as possible, the production process is simplified, the product yield and the purity are greatly improved, and the specific process is as follows:

using nickel and platinum raw materials, and blending according to the product requirement, wherein the component range is 40-90 wt.% Pt;

and (3) using a vacuum intermediate frequency induction furnace, firstly pumping the furnace chamber to high vacuum, then refilling argon, pumping to high vacuum, performing argon gas washing for multiple times, and then smelting under the protection of argon gas.

Based on the characteristics of the alloy in the composition range, the thermodynamic equilibrium state diagram of the binary alloy shows that the alloy has a very narrow crystallization temperature range although in an order transition region, namely the temperature difference between a liquidus line and a solidus line is very small, and particularly two lines coincide to form a lowest eutectic point at 55 wt% of Pt, so that the characteristic of endowing the alloy with excellent flowing property in a liquid phase state becomes a theoretical basis for realizing the casting process of the thin plate piece implemented by the invention.

The casting method designed by the invention is a centrifugal molding process, and comprises a heatable rotary platform and a special graphite casting die, and comprises the design of a pouring gate and a heat-insulating riser.

The heating rotary platform is circular, the diameter can be adjusted according to requirements, the material is metal (heat-resistant stainless steel but not limited) or graphite (not limited) which is not easy to generate thermal deformation, the use temperature can reach 800 ℃ in a vacuum and protective atmosphere environment, the surface is required to be smooth, and the thickness is determined by comprehensively considering the rigidity and the heat transfer efficiency; the lower part of the platform is provided with a heater, the forms of an electric furnace wire or a heating rod (without limitation) and the like can be used, the heating power can be adjusted according to the requirement, a single group or multiple groups of forms can be used so as not to hinder the rotation of the platform, a heating power supply is arranged outside the furnace body, and a temperature measuring device can be arranged or not arranged according to the requirement; the motor and the speed regulating mechanism are arranged outside the furnace body, the furnace shell and the power arm are sealed by a vacuum bearing, and the rotating speed of the platform is adjustable at 0-300 r/min.

The casting mould is made of three-high graphite (high purity, high strength and high density) and is an upper and lower parting mould. The lower die is in a circular disc shape, the thickness is set by considering heat transfer efficiency and heat preservation, the bottom is flatly and tightly attached to the rotary platform, the diameter is set according to requirements, the edge is provided with a disc wall, the wall height and the wall thickness are 10-15mm (unlimited), a chamfer angle of 1-2mm (unlimited) is reserved at the inner side, a circular arc-shaped holding pit is dug at the center of the circle, the diameter is 30-50mm, the depth is 5-10mm, and the heat preservation and mold filling capacity of the die is improved; the upper die and the lower die are consistent in shape, the upper die and the lower die are designed into two half dies to facilitate die opening, the upper die and the lower die can be assembled on the inner side of the lower die after being closed into a whole, the assembly gap is free of shaking and liquid leakage, the height is adjusted according to the requirement of the product thickness, the inner surface is smooth, an inverted cone-shaped (small upper part and large lower part) sprue is dug at the circle center, a pit is kept right opposite to the lower die, the diameter of a small opening is 35-45mm (unlimited), the diameter of the large opening is larger than that of a small opening, a boss is left at the upper opening (small opening) to be assembled with a pouring gate, the upper die comprises a side wall, vent holes (through holes) with the diameter of 0.3-; the pouring gate and the riser are integrally made of three-high graphite and are designed into two half dies so as to facilitate die opening, the pouring gate can be assembled with an upper die boss, the inner diameter of the pouring gate is the same as that of a small opening of an upper die, the length of the pouring gate is 30-40mm (unlimited), the upper end of the pouring gate is directly connected with the riser, the riser is conical, the small opening is the inner diameter of the pouring gate, the diameter of a large opening is twice (unlimited) the diameter of the small opening, the height of a cone is 30mm (unlimited), the upper end of the large opening is connected with a straight wall, the height of the large opening is 30-40mm (unlimited), the wall.

The inner surfaces of the mould including a pouring gate and a riser are polished or sprayed with a release agent according to the principle of convenient demoulding, the mould is fixed on a rotary platform by using a special clamp after being assembled according to design, and the riser and the pouring gate are required to be coated with a heat-insulating material (such as zirconium oxide cotton but not limited) when in use. Heating the mould to the required temperature in the alloy smelting process, rotating the mould during casting, setting the rotation speed to the required rotation speed, stably pouring the alloy liquid flow into a pouring gate at a certain speed, and finally ensuring that a dead head is fully poured to finish casting.

The invention has the beneficial effects that: aiming at the problem that the NiPt alloy target material in a specific component interval in actual production cannot be subjected to stress processing, a whole set of thin plate piece centrifugal molding casting process is designed according to the characteristics of the alloy, so that the shape of a casting is approximate to the shape of a product, the stress processing and the required heat treatment process are avoided ingeniously, the product purity is ensured, and the product yield is greatly improved.

Detailed Description

The present invention is further illustrated by, but is not limited to, the following examples.

Example 1

The NiPt target product with xxx trade mark has the thickness of 2.5-3mm, the circular arc with the diameter of 450mm and the component proportion of Ni-60 wt.% Pt. Preparing materials by using nickel and platinum with the purity of not less than 99.95 percent as raw materials, washing the materials for multiple times by using argon in a vacuum medium-frequency induction smelting furnace, and smelting under the protection of the argon; assembling the casting mold with the diameter of 450mm by 4mm according to requirements, heating to 500 ℃ before casting, setting the rotating speed of 120 ℃ at 150r/min, wrapping the pouring gate and the riser by using zirconia cotton, increasing the temperature of the melt by about 100 ℃, continuously casting the melt into the mold at a constant speed until the riser is full, continuously heating and rotating the melt, and stopping heating and rotating the melt after half an hour. And opening the furnace after full cooling and taking out the die, wherein the casting is good in mold filling and complete in shape, the required thickness of the product is achieved through plane milling after a dead head is cut, the cambered surface is formed through spinning forming, the surface quality of the final product is good, no crack exists, no inclusion hole exists in the product after flaw detection test, chemical composition and impurity content analysis is carried out, the result meets the requirement, the PTF detection is qualified, the delivery standard is reached, and the product is qualified for one time.

Example 2

The NiPt target product with xx mark is produced, the thickness is 6.0-6.5mm, the square shape is 400-420 mm-120-125 mm, and the component proportion is Ni-76 wt.% Pt. The same melting process as in example 1 was used, a mold with a diameter of 450mm by 7mm was used, and the casting process and mold assembly were the same as in example 1. The casting is complete in shape, the casting is taken out and then riser cutting is carried out, the casting is cut to be approximate in shape by using a plate shearing machine, the size of a final product is achieved by adopting end face milling and plane milling, the surface quality of the final product is good, no crack exists, no inclusion hole exists in the final product after flaw detection test, chemical components and impurity content analysis is carried out, the result meets the requirement, the PTF detection is qualified, the delivery standard is achieved, and the product is qualified at one time.

Reference documents:

[1] chinese patent CN101353732A

[2] Chinese patent CN104018120B

[3] Chinese patent CN104018128A

[4] Chinese patent CN104178739A

[5] Chinese patent CN104726829A

[6] Chinese patent CN105986138A

[7] European patent EP2025768A1

Claims

1. A method for preparing NiPt alloy target material, the related component interval is 40-90 wt.% Pt, characterized in that: the casting mold and the casting process are adopted to ensure that the shape of the casting is the shape of a product,

the casting process is a centrifugal molding process,

the centrifugal molding process adopts a heatable rotary platform as a base for placing the mold, the heating temperature is adjustable, the maximum temperature is not lower than 600 ℃, the rotating speed is adjustable, the maximum speed is not lower than 300r/min,

the centrifugal molding process adopts three-high graphite to manufacture a disc-shaped mold, a pouring gate and a riser, wherein the mold is in butt joint with an upper half and a lower half, the lower mold is large, and a retaining pit is arranged at the center of a circle; the thickness of the casting is controlled by an upper die, the upper die adopts a split die, the whole upper die comprises vent holes with the diameter of 0.3-0.5mm, and the hole distance is not more than 10 mm; the pouring gate and the riser adopt split molds,

the inner surface of the mould can be polished or sprayed with a release agent to facilitate ingot casting demoulding, the mould is heated before casting, a pouring gate and a riser are wrapped by heat-insulating cotton, the rotating speed is set according to the size of a casting, finally casting is carried out in a stable and continuous flow state, the riser is fully poured, the mould is heated and rotated for more than 10 minutes,

the thickness of the casting is set to be 0.5-1mm thicker than that of the final product, the inner surface of the mold can be polished or sprayed with a release agent without limitation so as to be beneficial to ingot casting demolding, the mold is heated before casting, a pouring gate and a dead head are wrapped by heat insulation cotton without limitation, the rotating speed is set according to the size of the casting, finally the casting is carried out in a stable and continuous flow state, the dead head is fully poured, and the mold is heated and rotated for more than 10 minutes.

2. A method for preparing NiPt alloy target material, the related component interval is 40-90 wt.% Pt, characterized by comprising the following process steps:

preparing materials by using nickel and platinum with the purity of not less than 99.95% as raw materials, wherein the component proportion is Ni-60 wt.% Pt, and smelting under the protection of argon after washing the furnace for multiple times by using a vacuum medium-frequency induction furnace; assembling a mold with the diameter of 450mm 4mm according to requirements, heating to 450-, the diameter is 450 mm.