Multi-level autolimitating etching method
A method for producing patterns includes inclined flanks from a face of a substrate. A protective mask is formed covering at least two masked areas of the face of the substrate and defining at least one intermediate space. An inclined flank is plasma etched from each masked area, wherein the etching forms continuous passivation layer on the inclined flanks producing autolimitation of the etching when the inclined flanks join each other. The etching is carried out in a chamber and includes the introduction into the chamber of a gas additional to the plasma. The additional gas includes molecules of a chemical species participating in the formation of the passivation layer, the quantity of gas in the chamber being controlled so that the chamber contains a quantity of molecules of the species sufficient to form the passivation layer continuously.
1. A method for producing patterns comprising inclined flanks from a face of a substrate, comprising
formation of a protective mask covering at least two masked areas of the face of the substrate and defining at least one intermediate space;
etching with a plasma forming, on at least one intermediate space, at least one inclined flank from each masked area, wherein the etching comprising the formation of a continuous passivation layer on the inclined flanks producing autolimitation of the etching when the inclined flanks join each other, and wherein the etching is carried out in a chamber and comprises the introduction into the chamber of a gas additional to the plasma, said additional gas comprising molecules of a chemical species participating in the formation of the passivation layer, the quantity of gas in the chamber being controlled so that the chamber contains, throughout the etching, a quantity of molecules of the species sufficient to form the passivation layer continuously, wherein
the passivation layer comprises a chemical species of the substrate, and
the etching is configured so as to generate molecules of the chemical species of the additional gas during the etching of the substrate.
2. The method according to claim 1 , wherein the quantity of additional gas is controlled so as to keep the growth of the passivation layer constant during the etching.
3. The method according to claim 1 , wherein the formation of the passivation layer comprises a reaction of the chemical species of the additional gas with another chemical species of the plasma.
4. The method according to claim 3 , wherein the other chemical species comprises oxygen.
5. The method according to claim 1 , wherein the protective mask is chosen so as not to react to the etching.
6. The method according to claim 1 , comprising a removal of the passivation layer and of the protective mask after etching.
7. The method according to claim 6 , wherein the removal comprises an attack of the passivation layer and of the protective mask with an acid solution.
8. The method according to claim 1 , wherein the masked areas are configured so as to produce a first series of inclined flanks having a first depth level in the substrate and at least a second series of inclined flanks having a depth level different from the first level.
9. The method according to claim 8 , comprising sets of four masked areas with a square cross section and arranged at the corners of a square, the sets being spaced apart in first direction (x) of the face of the substrate with a first repetition step.
10. The method according to claim 9 , wherein the sets are spaced apart in a second direction (y) of the face of the substrate, perpendicular to the first direction (x), with a second repetition step.
11. The method according to claim 10 , wherein the first and second repetition steps are equal.
12. The method according to claim 1 , wherein the etched material of the substrate is silicon (Si).
13. The method according to claim 1 , wherein the protective mask is made from silicon dioxide (SiO 2 ).
14. The method according to claim 1 , wherein the plasma is based on dichlorine and dioxygen (Cl 2 :O 2 ).
15. The method according to claim 1 , wherein the passivation layer is based on silicon.
16. The method according to claim 1 , wherein the additional gas contains the chemical species silicon.
17. The method according to claim 16 , wherein the additional gas is silicon tetrachloride (SiCl 4 ).