Ultra-hard low friction coating based on A1MgB14 for reduced wear of MEMS and other tribological components and system

• US 7,238,429 B2
• Filed: 09/21/2004
• Issued: 07/03/2007
• Est. Priority Date: 09/23/2003
• Status: Expired due to Fees

• Current Assignee: Iowa State University Research Foundation Incorporated (Iowa State University)
• Original Assignee: Iowa State University Research Foundation Incorporated (Iowa State University)
• Inventors: Tian, Yun, Harringa, Joel Lee, Cook, Bruce Allan, Russell, Alan Mark, Molian, Palaniappa A., Constant, Alan Paul
• Primary Examiner(s): Zimmerman; John J.
• Application Number:
  US10/946,051
• Publication Number:
  US 20050100748A1
• Time in Patent Office: 1,015 Days
• Field of Search: 428/650, 427/597
• US Class Current: 428/650
• CPC Class Codes: B81B 3/0075 For improving wear resistance
• CPC Class Codes: B81C 2201/032 LIGA process
• CPC Class Codes: C23C 14/067 Borides
• CPC Class Codes: C23C 14/28 by wave energy or particle radiation C23C14/32 - C23C14/48 take precedence
• CPC Class Codes: Y10S 428/938 Vapor deposition or gas diffusion
• CPC Class Codes: Y10T 428/12736 Al-base component
• CPC Class Codes: Y10T 428/1275 Next to Group VIII or IB metal-base component
• CPC Class Codes: Y10T 428/31678 Of metal

Abstract

Performance and reliability of microelectromechanical system (MEMS) components enhanced dramatically through the incorporation of protective thin film coatings. Current-generation MEMS devices prepared by the LIGA technique employ transition metals such as Ni, Cu, Fe, or alloys thereof, and hence lack stability in oxidizing, corrosive, and/or high temperature environments. Fabrication of a superhard, self-lubricating coating based on a ternary boride compound AlMgB₁₄ is described in this letter as a potential breakthrough in protective coating technology for LIGA microdevices. Nanoindentation tests show that hardness of AlMgB₁₄ films prepared by pulsed laser deposition ranges from 45 GPa to 51 GPa, when deposited at room temperature and 573 K, respectively. Extremely low friction coefficients of 0.04-0.05, which are thought to result from a self-lubricating effect, have also been confirmed by nanoscratch tests on the AlMgB₁₄ films. Transmission electron microscopy studies show that the as-deposited films are amorphous, regardless of substrate temperature; however, analysis of FTIR spectra suggests that the higher substrate temperature facilitates formation of the B₁₂ icosahedral framework, therefore leading to the higher hardness.

Claims

1. A method of forming an ultra-hard, low friction coated device comprising the steps of:

providing a micromachined substrate;

depositing a layer of AlMgB₁₄-based alloy over the micromachined substrate;

wherein the deposited layer of AlMgB₁₄-based alloy contains less than 10 mol % O.

2. The method of claim 1 wherein the depositing is by pulsed laser deposition.

3. The method of claim 1 wherein the depositing is by sputtering.

4. The method of claim 1 wherein the substrate is selected from the group consisting of silicon, glass, quartz, aluminum oxide, iron, copper and nickel.

5. The method of claim 1 wherein the AlMgB₁₄-based alloy is selected from the group consisting of AlMgB₁₄, Al_zSi_1-zMgB₁₄, AlCrMg_1-zB₁₄, AlTi_zMg_1-zB₁₄ and AlMgB₁₄X where X is present in an amount from 5 wt. % to 30 wt. % and comprises a doping agent selected from the group consisting of Group III, IV and V elements and borides and nitrides thereof and where 1≧

z≧

0.

6. The method of claim 5 wherein the AlMgB₁₄-based alloy is AlMgB₁₄.

7. The method of claim 5 wherein AlMgB₁₄-based alloy is Al_zSi_1-zMgB₁₄.

8. The method of claim 5 wherein the AlMgB₁₄-based alloy is AlCrMg_1-zMg_1-zB₁₄.

9. An ultra hard, low friction coated device comprising a micromachined substrate with a surface coating of AlMgB₁₄-based alloy which contains less than 10 mol % O.

10. The device of claim 9 wherein the AlMgB₁₄-based alloy is selected form the group consisting of AlMgB₁₄, Al_zSi_1-zMgB₁₄, AlCr_zMg_1-zB₁₄, AlTi_zMg_1-zB₁₄ and AlMgB₁₄X where X is present in an amount from 5 wt. % to 30 wt. % and comprises a doping agent selected from the group consisting of Group m, IV and V elements and borides and nitrides thereof and where 1≧

z≧

0.

11. The device of claim 9 wherein the AlMgB₁₄-based alloy is AlMgB₁₄.

12. The device of claim 9 wherein the AlMgB₁₄-based alloy is Al_zSi_1-zMgB₁₄.

13. The device of claim 9 wherein the AlMgB₁₄-based alloy is AlCr_zMg_1-zB₁₄.

14. The device of claim 9 wherein the surface coating of AlMgB₁₄-based alloy contains less than 5 mol. % O.