What's your location? What do you want to do with your backyard? Any pets or kids? If you want to grow grass bring in some enriched top soil. Break up what you have an add a layer of good enriched top soil 4-6" deep will give your grass a fighting chance. Now would NOT be the best time to plant grass, you'll be fighting heat, weeds, and lack of rain all summer long. If you're in an arid climate, I'd forgo grass and go with native plants. If you want a patch of green you can always use some of the new artificial turf.