You could use hideBackdrop={true} , position: 'fixed' .

Also, Is there any reason to use open={true} ?

<Dialog
      open={true} 
      onClose={handleClose}
      hideBackdrop={true} //Proper way to hide backdrop
      PaperProps={{
        style: {
          position: 'fixed',
          top: 0,
          right: 0,
          margin: '20px',
        },
      }}
    >