How do I prevent artifacting of a sound clip when slightly adjust the pitch (while keeping time constant)?

For some applications, I adjust the pitch of a voice clip ever-so-slightly (keeping time constant) and I'll notice that, when doing so, I'll get unwanted side effects such as the sound going "out of phase" or a weird echo. I have tried adjusting some of the settings within the Time/Pitch effect, but I'm not 100% sure how they impact the overall quailty of the output.