There is no "first" quantization
  The introduction of spinor and other massive fields by ``quantizing'' particles (corpuscles) is conceptually misleading. Only spatial fields must be postulated to form the fundamental objects to be quantized (that is, to define a formal basis for all quantum states), while apparent ``particles'' are a mere consequence of decoherence. This conclusion is also supported by the nature of gauge fields. 
H. D. Zeh