You can use dynamic SQL - for example like shown below if you want to append date/time to the filename. Backing up into a new table each time you want to take a backup is generally not a good idea for various reasons. There are other alternatives - everything from taking the backup of the whole database, backing up into a single table with an additional column to indicate the backup set, or saving a delta of the changes etc.
DECLARE @sql NVARCHAR(4000);
SET @sql = 'select * into Backup'
+ REPLACE(REPLACE(REPLACE(CONVERT(VARCHAR(32),GETDATE(),120),'-',''),' ',''),':','')
+ ' from MainTable'