High density refractory metals and alloys sputtering targets
View Patent ↗The present invention is directed to a process for producing high density, refractory metal products via a press/sintering process. The invention is also directed to a process for producing a sputtering target and to the sputtering target so produced.
1. A method of forming a sputtering-target plate that is sputterable to form highly uniform, low-resistivity films of a refractory metal selected from the group consisting of molybdenum, tungsten, an alloy of molybdenum and tungsten, molybdenum alloyed with a metal other than tungsten, and tungsten alloyed with a metal other than molybdenum, the method comprising:
cold isostatically pressing a powder of the refractory metal at a pressure selected from the range of 15,000 psi to 36,000 psi to form a pressed product;
heating the pressed product under vacuum at a rate of about 20° F. to about 120° F. to a first temperature selected from the range of about 300° F. to about 1000° F. and holding the pressed product at the first temperature for a period selected from the range of about 1 hour to about 38 hours;
heating the pressed product under vacuum at a rate of about 20° F. to about 120° F. from the first temperature to a second temperature selected from the range of about 1500° F. to about 2800° F. and holding the pressed product at the second temperature for a period selected from the range of about 1 hour to about 38 hours;
heating the pressed product under vacuum at a rate of about 20° F. to about 120° F. from the second temperature to a third temperature selected from the range of about 3000° F. to about 4000° F. and holding the pressed product at the third temperature for a period selected from the range of about 1 hour to about 38 hours;
allowing the pressed product to cool to room temperature; and
machining the pressed product to a desired size, thereby forming the sputtering-target plate that is sputterable to form highly uniform, low-resistivity films of the refractory metal, the sputtering-target plate having a density greater than 97% of a theoretical density of the refractory metal.
2. The method of claim 1 , further comprising bonding the sputtering-target plate to a backing plate.
3. The method of claim 1 , wherein the powder has a Fischer sub-sieve size of from about 2 to about 5 microns as measured according to ASTM B-30-65.
4. The method of claim 1 , wherein cold isostatically pressing the powder comprises holding the powder at pressure for a period of about 5 minutes to about 30 minutes.
5. The method of claim 1 , wherein cold isostatically pressing the powder comprises holding the powder at pressure for a period of about 7 minutes to about 20 minutes.
6. The method of claim 1 , wherein (i) the first temperature is selected from the range of about 400° F. to about 700° F., (ii) heating to the first temperature comprises heating at a rate of about 70° F. to about 100° F., and (iii) the pressed product is held at the first temperature for a period selected from the range of about 4 hours to about 12 hours.
7. The method of claim 1 , wherein (i) the second temperature is selected from the range of about 1700° F. to about 2200° F., (ii) heating to the second temperature comprises heating at a rate of about 40° F. to about 60° F., and (iii) the pressed product is held at the second temperature for a period selected from the range of about 10 hours to about 22 hours.
8. The method of claim 1 , wherein (i) the third temperature is selected from the range of about 3200° F. to about 3600° F., (ii) heating to the third temperature comprises heating at a rate of about 25° F. to about 40° F., and (iii) the pressed product is held at the third temperature for a period selected from the range of about 10 hours to about 24 hours.
9. The method of claim 1 , further comprising, after machining the pressed product, cleaning the machined pressed product and, thereafter, rinsing the machined pressed product.