Method for removal of impurities in cyclic siloxanes useful as precursors for low dielectric constant thin films

Abstract

A process for reducing the level(s) of water and/or other impurities from cyclosiloxanes by either azeotropic distillation, or by contacting the cyclosiloxane compositions with an adsorbent bed material. The purified cyclosiloxane material is useful for forming low-dielectric constant thin films having dielectric constants of less than 3.0, more preferably 2.8 to 2.0.

1 . 1,3,5,7-tetramethylcyclotetrasiloxane purified by a process selected from the group consisting of: 
 (1) contacting the cyclosiloxane precursor with an adsorbent bed material, so as to remove therefrom at least a portion of the water, and optionally at least one impurity, selected from the group consisting of acidic and basic impurities, to produce a cyclosiloxane precursor having a reduced level of water and optionally at least one impurity; and removing the purified cyclosiloxane precursor from the adsorbent bed material; and    (2) distilling a starting mixture comprising at least water and at least one [SiO] n  cyclosiloxane CVD precursor, in the presence of an azeotropic component, so as to form an azeotropic mixture with the water contained in said starting mixture; in order to produce (A) a distillate fraction comprising water and the azeotropic component and (B) a balance fraction comprising a purified cyclosiloxane precursor, whereby said balance fraction (B) is substantially reduced in water relative to said starting mixture; and    (3) a combination of 1 and 2.    
   
   
       2 . 1,3,5,7-tetramethylcyclotetrasiloxane containing (i) water in a range of from about 1 to 20 ppm, and acidic impurities in a range of from 0.001 to 0.00001%.  
   
   
       3 . 1,3,5,7-tetramethylcyclotetrasiloxane containing impurities below 0.001%.  
   
   
       4 . 1,3,5,7-tetramethylcyclotetrasiloxane according to  claim 3 , containing impurities below 0.00001%.  
   
   
       5 . 1,3,5,7-tetramethylcyclotetrasiloxane according to  claim 3 , containing water below 10 parts per billion.  
   
   
       6 . A SiCOH low dielectric constant thin film deposited from 1,3,5,7-tetramethylcyclotetrasiloxane purified by a method selected from the group consisting of: 
 (1) contacting the cyclosiloxane precursor with an adsorbent bed material, so as to remove therefrom at least a portion of the water, and optionally at least impurity, selected from the group consisting of acidic and basic impurities, to produce a cyclosiloxane precursor having a reduced level of water and optionally acidic impurity; and removing the purified cyclosiloxane precursor from the adsorbent bed material; and    (2) distilling a starting mixture comprising at least water and at least one [SiO] n  cyclosiloxane CVD precursor, in the presence of an azeotropic component, so as to form an azeotropic mixture with the water contained in said starting mixture; in order to produce (A) a distillate fraction comprising water and the azeotropic component and (B) a balance fraction comprising a purified cyclosiloxane precursor, whereby said balance fraction (B) is substantially reduced in water relative to said starting mixture; and    (3) a combination of 1 and 2.    
   
   
       7 . The SiCOH low dielectric constant thin film of  claim 6 , wherein said 1,3,5,7-tetramethylcyclotetrasiloxane contains (i) water in a range of from about 1 to 20 ppm, and acidic impurities in a range of from 0.001 to 0.00001%.  
   
   
       8 . The SiCOH low dielectric constant thin film of  claim 6 , wherein said 1,3,5,7-tetramethylcyclotetrasiloxane contains impurities below 0.001%.  
   
   
       9 . The SiCOH low dielectric constant thin film of  claim 6 , wherein said 1,3,5,7-tetramethylcyclotetrasiloxane contains impurities below 0.00001%.  
   
   
       10 . The SiCOH low dielectric constant thin film of  claim 6 , wherein said 1,3,5,7-tetramethylcyclotetrasiloxane contains water below 10 parts per billion.