Bad Block on Nand flahs cell

Question

I was researching about Reliability issues on flash memory (Nand). we know that if block is damaged it calls "bad block". But I have some questions that confusing me. looking forward to your help.
Here is my questions:

1.Can we also call that cell as a " bad cell" which include inside that bad blocks?

2.what is the difference between a bad block and bad cell (or damaged cell)?

3.Can bad block occur while program/read or program/write? (cause it is occur on often erasing block as long as i know)

Thank you in advance.

Answer 1

In a flash memory a cell is the minimal storage unit, which usually correspond to a single floating gate transistor.

It follows naturally that a bad cell is a not working storage unit.
The term is apparently valid and used, at least in this paper: Flash Memory Technology

Sometimes audio flash devices may contain some bad cells.

In a NAND flash cells are organized into pages not bytes, in order to achieve better space density.
A block is a group of pages that can be erased together; as such, blocks are just an array of cells and a bad block is a block containing at least one bad cell.

Regarding point three, I honestly can't tell for sure.
Reading, being just a sense, should not really be able to broke a cell.
Erasing, surely can.
According to Wikipedia, programming can be done with Hot Carrier Injection that may cause physical damage.