Apparently there is a way to actually write sheet music in Word. Here's a howto I found about it; unfortunately, I'm not equipped to check how it works. Seems rather... complicated.
Another route would be to write the sheet in a music-engraving program (if you don't have one, Musescore is free, and quite likely some others I don't know of). If you do this, use the program's Export function to export your work into an image file (you should find this in the menu somewhere under File). Choose a vector graphic format (not .png, that's a bitmap - something like .svg or .eps is better for this). You'll end up with a very neat picture you're free to rescale without losing on quality.
Scanning is not a neat option. If you go this way, then don't use your phone camera to snap a picture unless you really must; use an actual scanner, to ensure the angle is right. Make sure you set sufficient resolution when scanning.
After you've scanned it, use a graphic program (again, if you don't have one, Gimp is free) to adjust the brightness/contrast/levels/curves and generally polish the image to be easy on eyes. In my experience it's best to save scans of black and white documents as grayscale, rather than giving them a hard threshold; adjusting Levels automatically usually works fine to set black to black and white to white (if it doesn't, do it manually), and the edges don't come out so "hard" that way.
Here you're going to end up with a raster image, and it's a better idea to export as .png than .jpg, due to the way .jpg deals with edges.