Substrate processing method

1. A substrate processing method comprising:

forming a first thin film having a certain thickness adsorbed on a patterned spin-on-hardmask (SOH) structure by performing a first cycle a plurality of times, the first cycle comprising supplying a silicon-containing source gas as a first reactant on the patterned SOH structure, purging a residue, and forming an inert gas plasma by supplying an inert gas as a second reactant to dissociate the silicon-containing source gas, such that a derivative of the first reactant adsorbs on the substrate, to thereby form the first thin film; and

after the step of forming the first thin film, forming a second thin film by converting a chemical composition of the first thin film by performing a second cycle a plurality of times, the second cycle comprising supplying a reaction gas that is reactive with the patterned SOH structure and reactive with the silicon-containing source gas, and purging the residue.

2. The substrate processing method of claim 1 , wherein

the first thin film is densified by the second reactant.

3. The substrate processing method of claim 1 , wherein the first thin film comprises a mixture of elements constituting the first reactant, and the first thin film is formed by adsorbing the mixture on the patterned SOH structure.

4. The substrate processing method of claim 3 , wherein the first thin film comprises a chemical bond formed by one element of the mixture reacting with at least one of elements constituting the patterned SOH structure.

5. The substrate processing method of claim 1 , further comprising:

removing at least a portion of the second thin film to form a spacer pattern for the patterned SOH structure;

removing the patterned SOH structure; and

patterning a lower structure using the spacer pattern as a mask.

6. The substrate processing method of claim 5 , wherein

the spacer pattern comprises a first protrusion, a second protrusion, and a third protrusion protruding from the lower structure, and

a difference between a first distance between the first protrusion and the second protrusion and a second distance between the second protrusion and the third protrusion is less than 5 Angstroms.

7. The substrate processing method of claim 1 , further comprising forming a third thin film having the same component as that of the second thin film on the second thin film.

8. The substrate processing method of claim 7 , further comprising:

exposing the patterned SOH structure by performing etch-back on the second thin film and the third thin film;

removing the patterned SOH structure; and

patterning a lower structure using remaining portions of the second thin film and the third thin film as a mask.

9. The substrate processing method of claim 7 , wherein a third cycle is performed a plurality of times during the forming of the third thin film,

wherein the third cycle comprises:

supplying the first reactant on the second thin film;

purging a residue of the first reactant;

supplying the third reactant under a plasma atmosphere; and

purging a residue of the third reactant.

10. The substrate processing method of claim 1 , further comprising forming a third thin film having the same component as that of the second thin film on the second thin film by performing a third cycle a plurality of times, the third cycle comprising supplying the silicon-containing source gas.

11. The substrate processing method of claim 10 , wherein forming the third film comprises applying an oxygen plasma to induce a reaction between

the first thin film and the reaction gas.

12. The substrate processing method of claim 10 , wherein the residue purged during the second cycle comprises at least one of CH 4 , C 2 H 5 , N(C 2 H 5 ) 2 , CO 2 , NO, H 2 O, and H 2 .

13. The substrate processing method of claim 10 , wherein the reaction gas comprises oxygen.

14. The substrate processing method of claim 13 , wherein the first thin film has a thickness greater than or equal to a certain thickness which allows a loss of the patterned SOH structure that occurs while the third reactant reacts with the first thin film to be less than a certain value.

15. The substrate processing method of claim 13 , wherein the certain thickness is at least 15 Angstroms.

16. A substrate processing method comprising:

forming a first thin film of a certain thickness adsorbed on a patterned spin-on-hardmask (SOH) structure by performing a first cycle a plurality of times, the first cycle comprising supplying a silicon-containing source gas on the patterned SOH structure, purging residue, and forming an inert gas plasma to dissociate the silicon-containing source gas, such that a derivative of the first reactant adsorbs on the substrate, to thereby form the first thin film;

after forming the first thin film, forming a second thin film by converting a chemical composition of the first thin film by performing a second cycle a plurality of times, the second cycle comprising supplying a reaction gas that is reactive with the patterned SOH structure and reactive with the silicon-containing source gas and purging the residue; and

forming a third thin film having the same component as that of the second thin film on the second thin film by performing a third cycle a plurality of times, the third cycle comprising supplying the silicon-containing source gas and supplying the reaction gas.