ZnO film with C-axis orientation
A ZnO film with a C-axis preference is provided with a corresponding fabrication method. The method includes: forming a substrate; forming an amorphous Al 2 O 3 film overlying the substrate; and, forming a ZnO film overlying the Al 2 O 3 film at a substrate temperature of about 170° C., having a C-axis preference responsive to the adjacent Al 2 O 3 film. The substrate can be a material such as Silicon (Si) (100), Si (111), Si (110), quartz, glass, plastic, or zirconia. The Al 2 O 3 film can be deposited using a chemical vapor deposition (CVD), atomic layer deposition (ALD), or sputtering process. Typically, the Al 2 O 3 layer has a thickness in the range of about 3 to 15 nanometers (nm). The step of forming the ZnO film having a C-axis preference typically means that the ZnO film has a (002) peak at least 5 times greater than the (100) peak, as measured by X-ray diffraction (XRD).
1. A method for fabricating a ZnO film with a C-axis preference, the method comprising:
forming a substrate;
forming an amorphous Al 2 O 3 film overlying the substrate;
forming a ZnO film overlying the Al 2 O 3 film from an ALD process using diethylzinc (DEZ) and water, at a substrate temperature of about 170° C., having a C-axis preference responsive to the presence of the Al 2 O 3 film;
subsequent to forming the ZnO film, annealing the ZnO film at a temperature in the range of about 400 to 900° C.; and,
in response to the annealing, increasing the ZnO film C-axis preference.
2. The method of claim 1 wherein forming the substrate includes forming a substrate from a material selected from the group consisting of Silicon (Si) (100), Si (111), Si (110), quartz, glass, plastic, and zirconia.
3. The method of claim 1 wherein forming the amorphous Al 2 O 3 film overlying the substrate includes depositing the Al 2 O 3 film using a deposition process selected from the group consisting of chemical vapor deposition (CVD), atomic layer deposition (ALD), and sputtering.
4. The method of claim 1 wherein forming the amorphous Al 2 O 3 film overlying the substrate includes depositing Al 2 O 3 using an ALD process with a trimethylaluminum (TMA) and water precursor, at a substrate temperature of about 170° C.
5. The method of claim 1 wherein forming the amorphous Al 2 O 3 film overlying the substrate includes forming an Al 2 O 3 layer having a thickness in the range of about 3 to 15 nanometers (nm).
6. The method of claim 1 wherein forming the ZnO film having a C-axis preference includes forming a ZnO film with a (002) peak about 5 times as large as the (100) peak, or greater, as measured by X-ray diffraction (XRD).
7. The method of claim 1 wherein increasing the ZnO film C-axis preference includes forming a ZnO film with a (002):(100) peak ratio of greater than about 100:1.
8. The method of claim 1 wherein forming the ZnO film includes forming a ZnO film with a thickness; and,
the method further comprising:
in response to the annealing, forming crystal grains in the ZnO film having a maximum size about as large as the ZnO film thickness.
9. The method of claim 1 wherein forming the ZnO film includes forming the ZnO film with a thickness in the range of about 3 to 300 nanometers (nm).
10. The method of claim 1 wherein forming the ZnO film at a substrate temperature of about 170° C. includes forming the ZnO film at a substrate temperature in the range of about 160 to 180° C.