You can't scale a bitmap much over 100 percent without noticing degradation but Illustrator files are vector and can be scaled infinitely (or until the RAM runs out). When you scale a layer that originated in Illustrator more than 100 percent, use Continuous Rasterization.
To continuously rasterize an Illustrator file, do the following.
Select the layer containing the Illustrator file in the Timeline window.
Click the Collapse Transformations/Continuously Rasterize switch so that the On icon appears for that layer. (It looks like a Sun).
Notes about continuous rasterization
When you continuously rasterize a layer, the default rendering order for the layer changes. Applying an effect to a continuously rasterized layer may be different than when you apply the effect to a non-rasterized layer.
Continuous rasterization will not affect Illustrator layers with raster Illustrator effects applied. In Illustrator, notice the line that separates the effects and filters into top and bottom? The effects and filters above the line are Vector, and those below the line are Raster. None of the raster effects will be helped by continuous rasterization and will pixelate like any bitmap layer if you scale them more than 100 percent.
You can't paint interactively on a continuously rasterized layer. You can apply a paint effect by copying and pasting or using the Favorites menu but the results are not great. When you Continuously Rasterize a layer, its Layer window closes and won't open until you turn Continuously Rasterize off.
Whether or not you choose to Continuously Rasterize, After Effects anti-aliases the art if you view and render a composition using Best Quality.