you need a drawing program that works with vector images such as illustrator or coreldraw. photoshop is an image editing program that works with bitmap (not scaleable) images.
if your not familiar with these terms i suggest you wiki "vector" "raster" and "bitmap" to get an idea.
basically bitmaps or raster images are made up of pixels so when you scale them they get distorted and pixelated. vectors are saved as shapes rather than rows of dots. the save file is a piece of code containing the proportions, arrangement, colour etc of said shapes and as a result they can be scaled inifnetely without loss of quality.
hope this helps,
bugy.