Method for manufacturing a CBRAM semiconductor memory
View Patent ↗A method for manufacturing CBRAM switching elements and CBRAM semiconductor memories with improved switching characteristics so as to remove superfluous, weak, cluster-like, or unbound selenium at the surface of a GeSe layer is solved by the present invention in that, after the generation of an active matrix material or GeSe layer, respectively, a reactive sputter etching process is performed in which the surface layer of the active matrix material or GeSe layer, respectively, is removed at least partially so as to modify the surface structure thereof.
1. A method for manufacturing a resistively switching CBRAM semiconductor memory, the method comprising:
generating an active matrix material layer or a GeSe layer that is adapted to be placed in a substantially electroconductive state by an electrochemical switching processes;
after the generation of the active matrix material layer or GeSe layer, performing a reactive sputter etching process in which the surface layer of the active matrix material layer or GeSe layer is removed at least partially so as to modify the surface structure thereof; and
after performing the reactive sputter etching process, forming an Ag doping layer on a cleaned surface layer of the GeSe layer.
2. The method according to claim 1 , wherein, by means of the reactive sputter etching process, the surface structure of the GeSe layer and chemical bonds therein are re-organized and superfluous, weakly bound or clustered selenium is removed.
3. The method according to claim 1 , wherein the Ag doping layer is generated without the formation of AgSe conglomerates.
4. The method according to claim 1 , wherein chemical bonds in the surface structure of the GeSe layer are re-organized and superfluous, weakly bound or clustered selenium is removed.
5. The method according to claim 1 , wherein at least partial steps for cleaning or modification of the surface of the GeSe layer are performed directly after generation of the GeSe layer and without an interruption of a vacuum or without intermediate ventilation in a processing chamber of a sputter coating facility.
6. The method according to claim 1 , wherein, after performing reactive sputter etching, an Ag doping layer is deposited on the GeSe layer in a subsequent process step without an interruption of a vacuum or without intermediate ventilation in a processing chamber of a sputter coating facility.
7. The method according to claim 1 , wherein a surface activation or an activation of surface atoms of the GeSe layer is performed by an energy-rich plasma radiation.
8. The method according to claim 1 , wherein germanium atoms, selenium atoms and impurity atoms, are solved out of the surface of the GeSe layer by pulse transmission of a penetrating sputter ion.
9. The method according to claim 1 , wherein sputter ions that are directed to the GeSe layer are accumulated at least partially in layers close to the surface of the GeSe layer so as to react with weakly bound selenium atoms to form volatile selenium oxide or hydrogen selenide.
10. The method according to claim 1 , wherein a reactive gas/sputter gas is used which forms a volatile selenium compound with the selenium at the surface of the GeSe layer.
11. The method according to claim 1 , wherein a reactive gas/sputter gas with oxygen or hydrogen ions is used.
12. The method according to claim 1 , wherein, during the reactive sputter etching process, the GeSe layer is removed by a layer thickness of approximately 2 nm to 5 nm.
13. The method according to claim 1 , wherein, for generating an Ag doping layer, a dc-magnetron sputter process with an Ag element target with argon as a sputter gas at a pressure of approximately 4 to 5.times.10.sup.−3 mbar and a dc-sputter power in the range of approximately 1 to 3 kW is used.
14. The method according to claim 1 , wherein the GeSe layer is deposited in prefabricated vias on a substrate.
15. The method according to claim 1 , wherein the GeSe layer is at least temporarily impacted with a bias voltage, the bias voltage being adjustable in a controlled manner and being in an eV range.
16. The method according to claim 15 , wherein sputter particles used during the reactive sputter process accept kinetic energy that is determined by the bias voltage present at the GeSe layer.
17. The method according to claim 1 , wherein the GeSe layer is generated by rf-magnetron sputtering of a GeSe compound target with a layer thickness of approximately 50 nm.
18. The method according to claim 17 , wherein, for rf-magnetron sputtering, argon is used as a sputter gas at a pressure of approximately 4 to 7.times.10.sup.−3 mbar and a HF sputter power in a range of approximately 1 to 3 kW.
19. The method according to claim 1 , wherein the reactive sputter etching process is performed at a gas pressure in the range of 10.sup.−2 to 3.times.10.sup.−3 mbar.
20. The method according to claim 19 , wherein an active sputter time is few minutes and in a range of 1 to 3 minutes.
21. A method for manufacturing a resistively switching CBRAM semiconductor memory, the method comprising:
forming a bottom electrode;
forming an active matrix material layer comprising undoped SeGe;
cleaning a top surface of the active matrix material layer using a sputter etching process; and
after performing the sputter etching process, depositing a doping layer on the cleaned top surface of the active matrix material layer.
22. The method of claim 21 , wherein the cleaning comprises:
cleaning and reorganizing the top surface by transmitting inert gas ions or reactive gas ions onto the top surface;
activating the surface of the active matrix material by an energy rich plasma radiation; and
reacting loosely bound atoms of the active matrix material with a reactive gas to form a volatile compound.
23. The method of claim 21 , wherein the doping comprises silver.