Method for forming a (111) oriented BSTO thin film layer for high dielectric constant capacitors
A method for forming high capacitance crystalline dielectric layers with (111) texture is disclosed. In an exemplary embodiment, deposition of a plurality of nuclei is performed at a temperature in the range of about 430 to 460 degrees Celsius, followed by growth of a continuous BSTO dielectric layer at a temperature greater than 600 degrees Celsius. In an exemplary embodiment, a process is disclosed for growing a barium strontium titanium oxide film with high capacitance and thickness of about 30 nm or less.
1 . A method for forming a (111) oriented crystalline dielectric layer comprising:
forming a first capacitor electrode layer on a substrate;
exposing the substrate to a first gas that includes material to form the dielectric layer at a first temperature; and
exposing the substrate to a second gas that includes material to form the dielectric layer at a second temperature, wherein the second temperature is higher than the first temperature,
wherein a (111) oriented crystalline dielectric layer is formed.
2 . The method of claim 1 , wherein the first gas includes material that forms an oxide or titanate.
3 . The method of claim 1 , wherein the first and second gas are the same.
4 . The method of claim 1 , wherein the first and second gas comprise barium, strontium, titanium, and oxygen.
5 . The method of claim 4 , wherein the first electrode comprises a (111) oriented conductor.
6 . The method of claim 5 , wherein the first temperature is less than about 500 degrees Celsius and greater than or equal to about 430 degrees Celsius.
7 . The method of claim 5 , wherein the duration of the exposure of the first gas at a first temperature is about 2 to 30 seconds.
8 . The method of claim 5 , wherein the second temperature is greater than about 600 degrees Celsius.
9 . A method for forming a (111) oriented crystalline barium strontium titanium oxide layer with high capacitance comprising:
depositing a capacitor electrode layer on a substrate, wherein the electrode layer comprises a crystalline oriented film;
nucleating a seed layer for effecting a (111) orientation of the barium strontium titanium oxide (BSTO), wherein the substrate is exposed to a gas comprising a metal oxide at a first temperature; and
growing a continuous layer of (111) oriented barium strontium titanium oxide, wherein the substrate is exposed to a gas comprising barium, strontium, titanium, and oxygen at a second temperature.
10 . The method of claim 9 , further comprising preparing the metal surface before the step of nucleating a seed layer.
11 . The method of claim 9 , wherein the metal electrode comprises (111) oriented platinum.
12 . The method of claim 10 , wherein preparing the metal surface includes exposing the substrate to a third temperature for less than about 60 seconds.
13 . The method of claim 11 , wherein the gas used for nucleating a seed layer and the gas used for growing a continuous film are the same.
14 . The method of claim 13 , wherein the first temperature is less than about 500 degrees Celsius and greater than or equal to about 430 degrees Celsius.
15 . The method of claim 13 , wherein the duration of the exposure of the substrate to a gas comprising a metal oxide at a first temperature is about 2 to 30 seconds.
16 . The method of claim 14 , wherein the second temperature is greater than about 600 degrees Celsius.
17 . The method of claim 16 , wherein the first temperature is about 460 degrees Celsius.
18 . The method of claim 17 , wherein the continuous layer of (111) oriented barium strontium titanium oxide has a thickness of about 5 to 30 nanometers.
19 . A method for growing a (111) oriented BSTO crystalline layer for use as a capacitor comprising:
forming a (111) oriented crystalline first electrode on a substrate;
heating the substrate to a temperature sufficient to render the electrode surface substantially clean, but less than that necessary to cause a degradation in the (111) crystalline orientation of the surface;
heating the substrate to a second temperature and exposing the substrate to a gas including the elements comprising a first metal oxide, wherein the second temperature is sufficiently high to form a plurality of crystalline seeds required to subsequently form the (111) oriented crystalline BSTO layer, and further wherein the second temperature is less than that necessary to cause a degradation in the degree of (111) crystalline orientation of the BSTO crystalline layer; and
heating the substrate to a third temperature and exposing the substrate to a gas including the elements comprising a second metal oxide, wherein the third temperature is sufficiently high to grow a (111) oriented crystalline BSTO layer from the crystalline seeds.
20 . The method of claim 19 , wherein the first metal oxide and second metal oxide are the same.