Thin films

Abstract

Thin films are formed by formed by atomic layer deposition, whereby the composition of the film can be varied from monolayer to monolayer during cycles including alternating pulses of self-limiting chemistries. In the illustrated embodiments, varying amounts of impurity sources are introduced during the cyclical process. A graded gate dielectric is thereby provided, even for extremely thin layers. The gate dielectric as thin as 2 nm can be varied from pure silicon oxide to oxynitride to silicon nitride. Similarly, the gate dielectric can be varied from aluminum oxide to mixtures of aluminum oxide and a higher dielectric material (e.g., ZrO 2 ) to pure high k material and back to aluminum oxide. In another embodiment, metal nitride (e.g., WN) is first formed as a barrier for lining dual damascene trenches and vias. During the alternating deposition process, copper can be introduced, e.g., in separate pulses, and the copper source pulses can gradually increase in frequency, forming a transition region, until pure copper is formed at the upper surface. Advantageously, graded compositions in these and a variety of other contexts help to avoid such problems as etch rate control, electromigration and non-ohmic electrical contact that can occur at sharp material interfaces. In some embodiments additional seed layers or additional transition layers are provided.

1 . A method of forming a liner layer with a varying composition in a damascene trench, comprising:
 placing a substrate in a reaction chamber;   introducing first metal and a non-metal vapor phase reactants in alternate and temporally separated pulses to the substrate in a plurality of atomic layer deposition (ALD) cycles; and   introducing varying amounts of a second metal vapor phase reactant to the substrate during said plurality of deposition cycles.   
     
     
         2 .- 30 . (canceled) 
     
     
         31 . A method of producing a liner layer, said method comprising:
 depositing a first layer via an atomic layer deposition (ALD) process onto a substrate, wherein the first layer comprises tungsten, nitrogen, and carbon;   depositing a second layer via an ALD process over the first layer, wherein the second layer comprises tungsten; and   depositing a third layer via an ALD process over the second layer, wherein the third layer comprises copper.   
     
     
         32 . The method of  claim 31 , wherein the ALD process for the first non-graded layer comprises:
 introducinging TEB;   purging;   introducing WF 6 ;   purging;   introducing NH 3 ; and   purging over the substrate.   
     
     
         33 . The method of  claim 32 , wherein the first layer deposited is a non-graded layer of tungsten, nitride, and carbide. 
     
     
         34 . The method of  claim 33 , wherein the process for depositing the second layer comprises:
 introducing WF 6 ;   purging;   introducing disilane or diborane; and   purging over the substrate.   
     
     
         35 . The method of  claim 34 , wherein the second layer is a non-graded layer of tungsten. 
     
     
         36 . The method of  claim 34 , wherein the process for depositing the third layer comprises:
 introducing copper precursor;   purging,   introducing reducing precursor; and   purging over the substrate.   
     
     
         37 . The method of  claim 36 , wherein the third layer is a non-graded layer of copper. 
     
     
         38 . The method of  claim 36 , further comprising, between the deposition of the first layer and the deposition of the second layer, depositing a first transition layer, wherein depositing the first transition layer comprises depositing tungsten, nitride, and carbide, with additional amounts of tungsten added progressively during the deposition of the first transition layer. 
     
     
         39 . The method of  claim 38 , further comprising, between the deposition of the second layer and the deposition of the third layer, depositing a second transition layer, wherein depositing the second transition layer comprises depositing tungsten and copper, with additional amounts of copper added progressively during the deposition of the second transition layer. 
     
     
         40 . The method of  claim 36 , further comprising, between the deposition of the second layer and the deposition of the third layer, depositing a first transition layer, wherein depositing the first transition layer comprises depositing tungsten and copper, with additional amounts of copper added progressively during the deposition of the first transition layer. 
     
     
         41 . The method of  claim 31 , further comprising the step of depositing an electroplated layer onto the third layer. 
     
     
         42 . The method of  claim 33 , wherein depositing the second layer comprises supplying TEB, WF 6 , and NH 3  in a plurality of first cycles and supplying Cu-precursor and reducing precursor in a plurality of second cycles. 
     
     
         43 . The method of  claim 42 , wherein a frequency of supplying of TEB, WF 6 , and NH 3  is initially high compared to a frequency of supplying Cu-precursor and reducing precursor, and wherein the frequency of supplying TEB, WF 6 , and NH 3  is subsequently low compared to the frequency of supplying Cu-precursor and reducing precursor. 
     
     
         44 . The method of  claim 43 , wherein depositing the third layer comprises supplying a Cu-precursor and a reducing precursor in a plurality of third cycles.  45 - 65 . (canceled)