Do a search of this site. The topic of creating new hatch patterns has been discussed previously.
There are a number of websites where free hatch patterns can be downloaded.
The patterns can either be added to acad.pat (usually not a good idea) or be contained in a new .pat file. Make sure that if you create a new .pat file that you tell AutoCAD the "path" to the file under Tools > Options > Files.
What type of problems are you having adjusting the scale of a pattern?