How can I achieve this type of very clean halftone effect ?
Click Image > Mode > Grayscale (if the image is not already grayscale).
Click Filter > Pixelate > Color Halftone
Set the dot size you want, and set the Channel 1 value to 0. Ignore the others as they won't be used anyway.
After you have finished, you can convert the document back to RGB mode if you need to add colour elements.
Only problem with this is that it seems to create a white square grid pattern over the face. I've no idea what's causing that, so this PS filter might not be the best.
The Grayscale image has at first got levels or curves adjustment which makes the background full white and the darkest point black. Then a gaussian blur is applied to fade all sharp edges which would make the halftoning to look out crispy.
The halftoning of the grayscale image is made with Image > Mode > Bitmap > Halftone Screen > Round. Have a high output resolution to get solid looking dots.
The image is converted back to RGB (at first to grayscale from bitmap) and colorized slightly. Several coloring methods are available:
1) with Image > Adjustments > Hue&Saturation > colorize
2) by adding a colored layer with blending mode multiply.
3) with layer style "Color overlay"
Method 2 is used here
Your image is colorized with nearly or even exactly grey. It can be done also with adjusting levels.