Impurity reduction in silicon-containing films
Various embodiments herein relate to methods and apparatus for depositing doped and undoped silicon-containing films having a high degree of purity. In one example, the method includes exposing the substrate to a first reactant and a second reactant; reacting the first and second reactants with one another to form a silicon-containing material and depositing a portion of the silicon-containing film on the substrate; before the silicon-containing film is complete, performing an impurity reduction operation including: (i) generating a plasma from a plasma generation gas comprising inert gas and hydrogen, where the plasma generation gas is substantially free of oxygen, and (ii) exposing the substrate to the plasma to thereby reduce a concentration of fluorine, carbon, hydrogen, and/or nitrogen in the silicon-containing film; and repeating these operations (or a subset thereof) until the silicon-containing film is deposited to a final thickness.
1. A method for depositing a doped or undoped silicon-containing film on a substrate, the method comprising:
(a) exposing the substrate to a first reactant, wherein the first reactant is a silicon-containing reactant;
(b) reacting at least the first reactant in a first plasma to form a doped or undoped silicon-containing material, and depositing a portion of the doped or undoped silicon-containing film on the substrate, the doped or undoped silicon-containing film having a first impurity concentration;
(c) before the depositing of the portion of the doped or undoped silicon-containing film is complete, performing an impurity reduction operation comprising:
(i) generating a second plasma from a plasma generation gas,
wherein the plasma generation gas comprises inert gas and hydrogen (H 2 ), and
wherein the plasma generation gas is substantially free of oxygen (O 2 ), and
(ii) exposing the substrate to the second plasma to thereby reduce the first impurity concentration to a second impurity concentration in the doped or undoped silicon-containing material; and
(d) repeating (a) with at least one of (b) or (c) until the doped or undoped silicon-containing film is deposited to a final thickness.
2. The method of claim 1 , wherein the impurity is selected from the group consisting of fluorine, carbon, hydrogen, nitrogen, and combinations thereof.
3. The method of claim 1 , further comprising (e) exposing the substrate to a second reactant, wherein reacting at least the first reactant comprises reacting the first reactant with the second reactant to form the doped or undoped silicon-containing material, wherein repeating (a) with at least one of (b) or (c) further comprises repeating (e).
4. The method of claim 3 , wherein the first reactant and second reactant are introduced to a chamber comprising the substrate simultaneously.
5. The method of claim 3 , wherein the second reactant is an oxygen-containing reactant.
6. The method of claim 3 , wherein the first reactant and second reactant are introduced to a chamber comprising the substrate in temporally separated pulses.
7. The method of claim 1 , wherein the doped or undoped silicon-containing film is deposited in recessed features formed in a surface of the substrate, the method further comprising exposing the substrate to etching chemistry to etch a top portion of the doped or undoped silicon-containing film in the recessed features before the doped or undoped silicon-containing film fully fills the recessed features.
8. The method of claim 1 , wherein the doped or undoped silicon-containing film is deposited in recessed features formed in a surface of the substrate, the method further comprising exposing the substrate to inhibition chemistry to selectively inhibit deposition near a top of the recessed features as compared to a bottom and middle of the recessed features.
9. The method of claim 1 , wherein the second impurity concentration is less than 10 times the first impurity concentration.
10. The method of claim 1 , wherein concentration of fluorine in the doped or undoped silicon-containing film is on the order of about 1E16 atoms/cc once the doped or undoped silicon-containing film reaches the final thickness.
11. The method of claim 1 , wherein concentration of carbon in the doped or undoped silicon-containing film is about 1E20 atoms/cc or less once the doped or undoped silicon-containing film reaches the final thickness.
12. The method of claim 1 , wherein concentration of carbon in the doped or undoped silicon-containing film is about 2% or less (atomic percent) once the doped or undoped silicon-containing film reaches the final thickness.
13. The method of claim 1 , wherein concentration of hydrogen in the doped or undoped silicon-containing film is about 5E20 atoms/cc or less once the doped or undoped silicon-containing film reaches the final thickness.
14. The method of claim 1 , wherein concentration of hydrogen in the doped or undoped silicon-containing film is about 5% or less (atomic percent) once the doped or undoped silicon-containing film reaches the final thickness.
15. The method of claim 1 , wherein concentration of nitrogen in the doped or undoped silicon-containing film is about 3E20 atoms/cc or less once the doped or undoped silicon-containing film reaches the final thickness.
16. The method of claim 1 , wherein concentration of nitrogen in the doped or undoped silicon-containing film is about 1.5% or less (atomic percent) once the doped or undoped silicon-containing film reaches the final thickness.
17. The method of claim 1 , wherein generating the plasma in (d)(i) comprises flowing the inert gas at a rate of about 2 slm to about 60 slm, flowing the hydrogen at a rate of about 0.5 slm to about 5 slm, and generating the plasma at an RF power level that includes about 1000 W to about 6000 W HF RF, and about 0 W to about 5000 W LF RF.
18. The method of claim 1 , wherein the plasma generation gas comprises nitrogen (N 2 ).
19. The method of claim 1 , wherein the first reactant comprises a silane.
20. An apparatus for depositing a doped or undoped silicon-containing film on a substrate, the apparatus comprising:
a processing chamber;
an inlet to the processing chamber for introducing reactants to the processing chamber;
a plasma generator for generating a plasma in the processing chamber; and
a controller configured to:
cause the substrate to be exposed to a first reactant, wherein the first reactant is a silicon-containing reactant;
cause reacting of at least the first reactant in a first plasma to form a doped or undoped silicon-containing material, and depositing a portion of the doped or undoped silicon-containing film on the substrate, the doped or undoped silicon-containing film having a first impurity concentration;
before the depositing of the portion of the doped or undoped silicon-containing film is complete, cause an impurity reduction operation comprising:
(i) causing generation of a second plasma from a plasma generation gas,
wherein the plasma generation gas comprises inert gas and hydrogen (H 2 ), and
wherein the plasma generation gas is substantially free of oxygen (O 2 ), and
(ii) causing exposure of the substrate to the second plasma to thereby reduce the first impurity concentration to a second impurity concentration in the doped or undoped silicon-containing material; and
(d) causing repeating of (a) with at least one of (b) or (c) until the doped or undoped silicon-containing film is deposited to a final thickness.