Underdisplay finger print scanners had buzz in  the recent past.This type of scanners are expected in devices of Apple and Samsung. Apple was likely to show case this technology first that can scan your fingerprint through the screen, due to various patent leaks, but Vivo a chinese manufacturer becomes first to do so with partnering with Qualcomm.
vivo underscreen fingerprint scanners

  Qualcomm a well know  mobile chipset maker has  partnered with Vivo to unveil  it’s latest technology that can  scan fingerprint through  screens and metal in China at  MWC Shanghai. Soon  vivo  showcased concept teaser video on social media platforms.Earlier Qualcomm had tied with Xiaomi  for it’s Sense id fingerprint scanners with Mi5s.
Qualcomm's underdisplay fingerprint scanners
    Qualcomm calls this technology as next generation of ultrasonic fingerprint scanners that are capable of scanning your fingerprint under screen and metal. The scanner is integrated under the OLED display(upto 1.2mm thick) and can even work underwater. It works under glass and metal as well with penetration upto 800um for glass,600um for aluminium and 400um for other material 
fingerprint scanner under display
   Vivo showcased working prototype which was Vivo Xplay6. vivo had only few percentage of screen covered with this. Qualcomm said that it would increase the cost of the phone if entire screen is covered with this, during showcase the phone did unlocked with placing finger on screen and behind the phone(metal), it did not unlock when unknown finger is scanned.As Qualcomm said the scanner also worked well under water and was able to unlock the phone. Qualcomm said that it will start shipping this Q4 this year and is compatible with Qualcomm Snapdragon 660&630 mobile platforms.
  As Apple and Samsung are expected to use underdisplay scanners in their next devices it will be intresting to see the battle between them to be the perfectionist
    Here is the concept video made by vivo