Hello Liu Hui,
Part number MSCMMX6QZDK08AB is in End Of Life status as you can see on the Part Details page (link below).
https://www.nxp.com/part/MSCMMX6QZDK08AB
There is not a replacement for this part but if you are interested in a PoP version of the i.MX6 there is one with a different package (thus is not pin-to-pin compatible with the i.MX6 SCM). You can see its Datasheet on the link below.
https://www.nxp.com/docs/en/data-sheet/IMX6DQCPOPEC.pdf
My apologies for the inconvenience.
Regards,
