What technology of memory is Cache RAM usually?

Static random-access memory (static RAM or SRAM) is a type of semiconductor random-access memory (RAM) that uses bistable latching circuitry (flip-flop) to store each bit. SRAM exhibits data remanence,[1] but it is still volatile in the conventional sense that data is eventually lost when the memory is not powered.

The term static differentiates SRAM from DRAM (dynamic random-access memory) which must be periodically refreshed. SRAM is faster and more expensive than DRAM; it is typically used for CPU cache while DRAM is used for a computer's main memory.

sram is faster than flash memory hence used in cache memory

Cache memory, also called CPU memory, is high-speed static random access memory (SRAM) that a computer microprocessor can access more quickly than it can access regular random access memory (RAM). ... Cache memory is responsible for speeding up computer operations and processing.