System and method for forming a bipolar switching PCMO film

1. A method for forming a bipolar switching

Pr x Ca 1-x MnO 3 (PCMO) thin film, the method comprising:

forming a bottom electrode;

depositing a nanocrystalline PCMO layer;

depositing a polycrystalline PCMO layer; and,

forming a multi-layer PCMO film with bipolar switching properties.

2. The method of claim 1 wherein depositing a nanocrystalline PCMO layer includes depositing a PCMO layer with crystal grains having a size in the range of 3 to 40 nanometers (nm).

3. The method of claim 1 wherein depositing a polycrystalline PCMO layer includes depositing a PCMO layer with crystal grains having a size in the range of 40 nm to epitaxial.

4. The method of claim 1 wherein forming a bottom electrode includes forming a bottom electrode from a material selected from the group including Pt, Au, Er, and a stack of materials including PtIx/SiO2/Si and Ir/x/SiO2/Si, where x is a material selected from the group including Ti, TiN, and TaN.

5. The method of claim 1 further comprising:

preparing a precursor solution as follows:

introducing Pr(thd)3, Ca(thd)2, and Mn(thd)3 with a molar ratio of about (0.9:0.5:1), (0.9:0.6:1), and (1.04:0.62:1), respectively, dissolved in a solvent selected from the group including butylether and tetraglyme, in a volume ratio of about 3:1, and a concentration of 0.1 mole PCMO material per liter;

injecting the precursor into a vaporizer at a temperature in the range of 220 to 300 degrees C., using a water flow meter at a rate of 0.1 to 0.5 milliliter/minute (ml/mm);

introducing precursor vapor to a deposition chamber using a feedline at a temperature in the range of 230 to 300 degrees C.; and,

wherein depositing the nanocrystalline and polycrystalline PCMO layers includes:

maintaining a deposition chamber pressure in the range of 1 to 5 Torr;

creating an oxygen partial pressure in the range of 20 to 30%; and,

delivering the precursor vapor for a duration in the range of 1 to 30 min.

6. The method of claim 5 wherein introducing Pr(thd)3, Ca(thd)2, and Mn(thd)3 includes preparing precursor with Pr:Ca:Mn in a ratio of about 1.04:0.62:1;

wherein injecting the precursor into a vaporizer at a temperature in the range of 220 to 300 degrees C. includes injecting precursor at a temperature in the range between 250 and 300 degrees C.;

wherein depositing a nanocrystalline PCMO layer includes maintaining a deposition temperature in the range of 350 to 420 degrees C.; and,

wherein a nanocrystalline PCMO layer is deposited.

7. The method of claim 5 wherein introducing Pr(thd)3, Ca(thd)2, and Mn(thd)3 includes preparing precursor with Pr:Ca:Mn in a ratio of about 0.8:0.5:1;

wherein injecting the precursor into a vaporizer at a temperature in the range of 220 to 300 degrees C. includes injecting precursor at a temperature in the range between 220 and 260 degrees C.;

wherein depositing a polycrystalline PCMO layer includes maintaining a deposition temperature in the range of 420 to 550 degrees C.; and,

wherein a polycrystalline PCMO layer is deposited.

8. The method of claim 1 wherein forming a multi-layer PCMO film with bipolar switching properties includes:

writing a high resistance in the range of 10 to 1000 kilo ohms in response to a pulse having a voltage in the range of ±(2 to 10) volts (V), with a duration in the range of 5 nanosecond (na) to 50 microseconds; and,

resetting to a low resistance in the range of 500 ohms to 10 kilo ohms, in response to a pulse having a voltage in the range of ±(2 to 10) V, with a duration in the range of 5 na to 50 microseconds.

9. The method of claim 1 wherein depositing a nanocrystalline PCMO layer includes depositing a nanocrystalline layer having a thickness in the range of 5 to 100 nanometers (nm); and

wherein depositing a polycrystalline PCMO layer includes depositing a polycrystalline layer having a thickness in the range of 5 to 100 nm.

10. The method of claim 8 wherein depositing a nanocrystalline PCMO layer includes depositing a nanocrystalline PCMO layer with a first thickness;

wherein depositing a polycrystalline PCMO layer includes depositing a polycrystalline PCMO layer with a second thickness; and,

wherein forming a multi-layer PCMO film with bipolar switching properties includes forming a bi-layer PCMO film with an overall greater resistance, a resistance ratio between the high and low resistance states that increases, and a switching voltage pulse amplitude that increases, in response to increasing the first and second thicknesses.

11. The method of claim 8 wherein depositing a nanocrystalline PCMO layer includes depositing a first number of nanocrystalline PCMO layers, each having a first thickness;

wherein depositing a polycrystalline PCMO layer includes depositing the first number a polycrystalline PCMO layers, each having a second thickness; and,

wherein forming a multi-layer PCMO film with bipolar switching properties includes forming a multi-layer PCMO film with a first number of bi-layers.

12. The method of claim 11 wherein forming a multi-layer PCMO film with a first number of bi-layers includes forming a PCMO film where the first number of bi-layer varies in the range between 2 and 20.

13. The method of claim 11 wherein forming a multi-layer PCMO film with a first number of bi-layer includes forming a PCMO film with an overall lower resistance, a resistance ratio between the high and low resistance states that decreases, and a switching voltage pulse amplitude that increases, in response to increasing the first and second thicknesses, while decreasing the first number of layers, and maintaining a constant overall thickness that is a thickness combination of each of the nanocrystalline and polycrystalline layers.

14. The method of claim 8 wherein depositing a nanocrystalline PCMO layer includes depositing a nanocrystalline PCMO layer overlying the bottom electrode;

wherein depositing a polycrystalline PCMO layer includes depositing a polycrystalline PCMO layer overlying the nanocrystalline layer; and,

wherein forming a multi-layer PCMO film with bipolar switching properties includes:

writing a high resistance in the range of 10 to 1000 kilo ohms in response to a pulse having a voltage in the range of −(2 to 10) V, with a duration in the range of 5 ns to 50 microseconds; and,

resetting to a low resistance in the range of 500 ohms to 10 kilo ohms, in response to a pulse having a voltage in the range of +(2 to 16) V, with a duration in the range of 5 ns to 50 microseconds.

15. The method of claim 8 wherein depositing a polycrystalline PCMO layer includes depositing a polycrystalline PCMO) layer overlying the bottom electrode;

wherein depositing a nanocrystalline PCMO Layer includes depositing a nanocrystalline PCMO layer overlying the polycrystalline layer; and,

wherein forming a multi-layer PCMO film with bipolar switching properties includes:

writing a high resistance in the range of 10 to 1000 kilo ohms in response to a pulse having a voltage in the range of +(2 to 10) V, with a duration in the range of 5 ns to 50 microseconds; and,

resetting to a low resistance in the range of 500 ohms to 10 kilo ohms, in response to a pulse having a voltage in the range of −(2 to 10) V, with a duration in the range of 5 ns to 50 microseconds.

16. The method of claim 1 further comprising:

forming a top electrode overlying the multi-layer PCMO film.

17. The method of claim 1 wherein forming a multi-layer PCMO film with bipolar switching properties includes forming a multilayer PCMO film where the polycrystalline content is at least 20% of the total PCMO material.

18. A method for forming a Pr x Ca 1-x MnO 3 (PCMO) thin film with selectable bipolar switching characteristics, the method comprising:

forming a bottom electrode;

forming a multi-layer PCMO film, with a bi-layer including a nanocrystalline PCMO layer and a polycrystalline PCMO layer;

ordering the PCMO bi-layer; and,

in response to the PCMO bi-layer ordering, selecting the resistance switching polarities.

19. The method of claim 18 wherein ordering the PCMO bi-layer includes forming the polycrystalline PCMO layer overlying the nanocrystalline PCMO layer; and,

wherein selecting the resistance switching polarities includes:

writing a high resistance in response to a negative polarity voltage pulse; and,

resetting a low resistance in response to a positive polarity voltage pulse.

20. The method of claim 18 wherein ordering the PCMO bi-layer includes forming the nanocrystalline PCMO layer overlying the polycrystalline PCMO layer; and,

wherein selecting the resistance switching polarities includes:

writing a high resistance in response to a positive polarity voltage pulse; and,

resetting a low resistance in response to a negative polarity voltage pulse.

21. A method for forming a bipolar switching Pr x Ca 1-x MnO 3 (PCMO) thin film, the method comprising:

forming a bottom electrode;

preparing a precursor solution as follows:

introducing Pr(thd)3, Ca(thd)2, and Mn(thd)3 with a molar ratio of about (0.9:0.6:1), (0.9:0.6:1), and (1.04:0.62:1), respectively, dissolved in a solvent selected from the group including butylether and tetraglyme, in a volume ratio of about 3:1, and a concentration of 0.1 mole PCMO material per liter;

injecting the precursor into a vaporizer at a temperature in the range of 220 to 300 degrees C., using a water flow meter at a rate of 0.1 to 0.5 milliliter/minute (ml/min);

introducing precursor vapor to a deposition chamber using a feedline at a temperature in the range of 230 to 300 degrees C.;

depositing nanocrystalline and polycrystalline PCMO layers as follows:

maintaining a deposition chamber pressure in the range of 1 to 5 Torr;

creating an oxygen partial pressure in the range of 20 to 30%; and,

delivering the precursor vapor for a duration in the range of 1 to 30 mm; and,

forming a multi-layer PCMO film with bipolar switching properties.