The 7za.exe file is part of java_jre package. So when java_jre package is being deployed on to the robot all files under this package first copied in "Program Files (x86)\Nimsoft\robot\pkg\temp\" directory from archive with files are put as .tmp extension. Then all files are copied to respective path and all .tmp files under "Program Files (x86)\Nimsoft\robot\pkg\temp\" are removed.
But due to some reason these .tmp extension files are not being removed from "Program Files (x86)\Nimsoft\robot\pkg\temp\" directory but 7za.exe.tmp files are not malicious.
Please check if any anti-virus application is running on this particular server which doesn't allow removing files, do you see this behavior on any other server too. As dev team confirmed these files are not malicious.