So yes, the Emperor influenced the midichlorians in Shimi Skywalkers womb to create Anakin. It's something that was actually explained back in Revenge Of The Sith when Palpatine explains the "tragedy of Darth Plagueis":
It's a Sith legend. Darth Plagueis was a Dark Lord of the Sith, so powerful and so wise he could use the Force to influence the midichlorians to create life…
Screenrant explains how Vader found this out in the comic, revealing some more about his motivations in the process:
Explaining that Darth Vader built his castle to save Padmé Amidala, the latest issue shows Vader succeeded in his mission to tear a whole between the realm of life, and that of the living Force. Upon entering, Vader (shown in his Force form, as a roiling figure of dark energy) re-lived all the most pivotal moments of his life. None more startling than seeing his mother during her pregnancy… with Darth Sidious’ arms encircling her, hands curled in Sith sorcery, forming the swirl of energy inside of her that would one day emerge as Anakin.