Marissa Evans' 21-year-old son was badly injured during an attack late last month and died from his wounds on Sunday.
According to the "Austin American-Statesman" newspaper, Evans requested an emergency hearing so she could fight for the sperm and have a chance to create grandchildren through a surrogate mother.
She told the judge her son had always dreamed of having three sons and had already decided on the names Hunter, Tod and Van for his future offspring.
Evans also admitted she wanted her son to live on, telling the judge she wanted to "keep a piece of him."
The judge ordered medical examiner's to maintain the body and allow an expert to come in and collect the sperm.
Evans and her attorneys are trying to find a urologist or other expert willing to retrieve the specimen. Medical experts say whether the sperm is useful often depends on how soon after death it is collected.
Texas law allows parents to decide whether their child's organs will be donated, but a University of Texas law professor says the issue of post-mortem sperm retrieval is very unclear and without precedent.