Method for sputtering compounds on a substrate

• US 5,942,089 A
• Filed: 04/22/1996
• Issued: 08/24/1999
• Est. Priority Date: 04/22/1996
• Status: Expired due to Fees

• Current Assignee: Northwestern University
• Original Assignee: Northwestern University
• Inventors: Graham, Michael E., Sproul, William D.
• Primary Examiner(s): Nguyen, Nam
• Assistant Examiner(s): MCDONALD, RODNEY GLENN
• Application Number:
  US08/635,472
• Time in Patent Office: 1,219 Days
• Field of Search: 204/192.13, 204/192.15, 204/192.22, 204/192.23, 204/192.25, 204/298.03, 204/298.07, 204/298.08, 204/298.14, 204/298.26 , 204/298.06, 204/192.16
• US Class Current: 204/192.13
• CPC Class Codes: C23C 14/0021 Reactive sputtering or evaporation
• CPC Class Codes: C23C 14/081 of aluminium, magnesium or beryllium
• CPC Class Codes: C23C 14/083 of refractory metals or yttrium
• CPC Class Codes: C23C 14/505 for rotation of the substrates

Abstract

A method and apparatus for monitoring and controlling deposition of metal, insulating compounds or other compounds on a substrate by sputtering techniques includes maintaining pulsed, constant, direct current power to the target, sensing the voltage of the target material used in the process, simultaneously rapidly sensing the partial pressure of the reactive gas, and simultaneously biasing the substrate to activate the reactive gas or otherwise energizing the reactive gas in the vicinity of the substrate. An apparatus for practicing the invention is also disclosed.

Claims

1. A method for deposition of a film comprising a compound by sputtering means onto a substrate, which film is conducting or non-conducting and which film includes a metallic or semi-conducting element derived from a metallic or semi-conducting sputtering target, said metallic or semi-conducting element being combined with at least one additional element in the form of a reactive gas to form the compound, said method comprising the steps of:

(a) providing a target as a cathode in a vacuum chamber of the metal or semi-conductor to be combined with the reactive gas to form the compound;

(b) providing an inert gas in the chamber that becomes ionized and bombards the target to release metal or semi-conductor atoms and ions therefrom into the chamber;

(c) providing the substrate in the chamber to be coated with the compound comprised of the reactive gas and the metal or semi-conductor;

(d) providing an anode in the chamber;

(e) admitting the reactive gas into the chamber, said reactive gas capable of forming the compound in combination with atoms and ions from the target;

(f) supplying pulsed, direct current, electrical power to the target to effect ionization of the inert gas and thereby effect bombardment of the target to release atoms and ions from the target into the chamber for combination with the reactive gas; and

(g) controlling the admission and reaction of the reactive gas by;

(i) maintaining constant power to the target;

(ii) measuring substantially instantaneously a target voltage and providing a first voltage measurement signal for controlling the rate of admission of the reactive gas to the chamber to achieve partial pressure reflective of a compound composition having defined physical characteristics, said first voltage measurement signal comprising an independent measurement indicative of the partial pressure in the system which is not reactive gas species specific, which provides a signal characteristic of the optimal range of partial pressure for reaction of the reactive gas;

(iii) simultaneously measuring the species specific partial pressure of the reactive gas and providing a second signal for controlling the rate of admission of the reactive gas to the chamber and to control the partial pressure range for measurement and control by the first voltage measurement signal to achieve partial pressure control reflective of the said compound composition, both said first voltage measurement signal and said second signal being used to control admission of reactive gas to the chamber simultaneously, said first voltage measurement signal being measured at a faster rate than the second signal; and

(iv) simultaneously activating the reactive gas at or near the substrate by introducing a localized energy input thereto.

2. The method of claim 1 wherein the target is a metal and said film is non-conducting.

3. The method of claim 1 including deposition of the film on the substrate at a rate at least about 50% of the rate of deposition of metal or semi-conductor element at substantially the same power conditions.

4. The method of claim 1 wherein controlling admission of the reactive gas in response to the target voltage is more rapid than in response to measuring the partial pressure of the reactive gas.

5. The method of claim 1 wherein the compound is taken from the group consisting of oxides, nitrides, carbides, sulfides, fluorides, chlorides, borides and mixtures thereof.

6. The method of claim 1 wherein the metal is taken from the group consisting of aluminum, titanium, hafnium, zirconium, tantalum, silicon, chromium and mixtures thereof.

7. The method of claim 1 wherein the power is a symmetric, bipolar pulsed direct current power pulsed in the range of about 2 to 250 kHz.

8. The method of claim 1 wherein the power is an asymmetric bipolar pulsed direct current power pulsed in the range of about 2 to 250 kHz.

9. The method of claim 1 wherein the localized energy input is taken from the group consisting of pulsed direct current power supply applied to the substrate;

a radio frequency voltage source applied to the substrate, a laser activation source, an electron beam source, a microwave source, and an inductively coupled plasma source.

10. The method of claim 1 wherein the localized input energy is a radio frequency source of 13.56 MHz or a harmonic thereof.

11. The process of claim 1 wherein the step of measuring the partial pressure of the reactive gas comprises measuring with an optical gas analyzer or mass spectrometer.

12. The process of claim 1 wherein said physical characteristics are selected from the group comprising:

constituent composition, reflectivity, transmission, index of refraction, extraction coefficient, hardness, modulus, conductivity, and combinations thereof.

13. Apparatus for deposition of a film comprising a compound by sputtering means onto a substrate, which film is conducting or non-conducting and which film includes a metallic or semi-conducting element derived from a metallic or semi-conducting sputtering target, said metallic or semi-conducting element being combined with at least one additional element in the form of a reactive gas to form the compound, said apparatus comprising, in combination:

(a) a vacuum chamber

(b) a target as a cathode in the vacuum chamber of the metal or semi-conductor to be combined with the reactive gas to form the compound;

(c) an inert gas source to the chamber to supply inert gas that becomes ionized and bombards the target to release metal or semi-conductor atoms and ions therefrom into the chamber;

(d) a substrate support in the chamber for a substrate to be coated with the compound;

(e) an anode in the chamber;

(f) a reactive gas source to the chamber, said reactive gas capable of forming the compound with atoms and ions from the target for coating the substrate;

(g) means to supply pulsed, direct current, electrical power to the target to effect ionization of the inert gas and to effect bombardment of the target to release atoms and ions from the target into the chamber; and

(h) means for controlling the admission and reaction of the reactive gas including;

(i) means for maintaining constant power to the target;

(ii) means for measuring the target voltage to provide a first signal for controlling the rate of admission of the reactive gas to the chamber to achieve partial pressure reflective of a compound composition having defined physical characteristics, said first signal measuring means comprising an independent measurement indicative of the partial pressure in the system which is not reactive gas species specific and which provides a signal characteristic of the optimal range of partial pressure for reaction of the reactive gas;

(iii) means for simultaneously measuring the species specific partial pressure of the reactive gas to provide a second signal for controlling the rate of admission of the reactive gas to the chamber within the optimal range defined by the means for providing the first signal to control partial pressure to be optimally reflective of the said compound composition, both said first and second signals being used simultaneously to control admission of reactive gas to the chamber, said means for controlling providing the first signal at a faster rate than the second signal; and

(iv) means for simultaneously activating the reactive gas at or near the substrate by introducing a localized energy input thereto.