I don't watch that much TV, but Abby (sp?) from NCIS springs to mind, slightly quirky, but v. intelligent, commanding.
The equivalent character in Alias, f.e., was (in early series at least) a one-dimensional dork.
Basically anyone in Big Bang Theory, Bones (herself). They're certainly STEM, but maybe not "tech" depending on what people mean by that.
I don't necessarily think the equivalent male characters are treated comparably well, for what it's worth. But if you want to encourage teenage girls to look at tech, showing them that it's also for normal people would help a lot.
I will say that Silicon Valley does a decent job subverting the trend with a handful of minor female characters.
I've only worked one job in science, I wouldn't describe the 400 or so people as "normal" as a population: geeky and nerdy, weird a wide variance, but not what I'd expect 999/1000 to be enamoured with.
Perhaps the lack of social skills, and friends, of a good portion of that population (myself included) was an aberration and didn't represent people who prosper in STEM roles in general.
Playing off this, I think pop culture deserves more blame than it gets for the lack of women in tech. A software engineer is more likely to enjoy ComicCon than than the average person, but actually working in software is pretty normal.
In the previous decade or two, some TV shows have been casting women as the "tech genius" quite a bit. That's good. But they are often weird, rude, or creepy (still 40 and shopping at Hot Topic?). They're usually taking orders rather than giving them. And they're often squirreled away in some lab instead of being part of the story itself. I'm concerned the message for women (and men for that matter) is "Tech is great... if you're into dressing up like a wizard and sitting in a cubical. You do you (over there)!"