Device for producing an amorphous carbon layer by electron cyclotron resonance plasma, the device comprising: - a plasma chamber ; - means for conveying a gas into the plasma chamber , - a magnetic confinement mirror , - a waveguide inserted into the plasma chamber , the waveguide extending along a reference axis ; - means for injecting a microwave electromagnetic wave arranged to inject a microwave electromagnetic wave into the plasma chamber by means of the waveguide ; - means for generating a magnetic field in the plasma chamber , the injection means and the generating means being configured to form an electron cyclotron resonance zone in the plasma chamber , the means for generating the magnetic field being further configured to create a beam of magnetic field lines along which plasma is diffused, the plasma extending along the reference axis , the plasma having an edge; - a target made from carbon to be sputtered; - a substrate holder arranged to hold a substrate; Characterised in that : - the target is arranged parallel to the reference axis and at a distance from the reference axis of between R target /2 and R target , where R target is the distance, at the level of the target, between the edge of the plasma and the reference axis, and in that - the device further comprises a screen arranged between the waveguide and the substrate holder , the screen extending perpendicularly to the reference axis and locally stopping plasma particles capable of impacting the substrate; - the substrate holder is arranged parallel to the reference axis and at a distance from the reference axis greater than R target such that the substrate is arranged outside of the plasma; - the target and the substrate holder are arranged facing each other. - a plasma chamber ; - means for conveying a gas into the plasma chamber , - a magnetic confinement mirror , - a waveguide inserted into the plasma chamber , the waveguide extending along a reference axis ; - means for injecting a microwave electromagnetic wave arranged to inject a microwave electromagnetic wave into the plasma chamber by means of the waveguide ; - means for generating a magnetic field in the plasma chamber , the injection means and the generating means being configured to form an electron cyclotron resonance zone in the plasma chamber , the means for generating the magnetic field being further configured to create a beam of magnetic field lines along which plasma is diffused, the plasma extending along the reference axis , the plasma having an edge; - a target made from carbon to be sputtered; - a substrate holder arranged to hold a substrate; - the target is arranged parallel to the reference axis and at a distance from the reference axis of between R target /2 and R target , where R target is the distance, at the level of the target, between the edge of the plasma and the reference axis, and in that - the device further comprises a screen arranged between the waveguide and the substrate holder , the screen extending perpendicularly to the reference axis and locally stopping plasma particles capable of impacting the substrate; - the substrate holder is arranged parallel to the reference axis and at a distance from the reference axis greater than R target such that the substrate is arranged outside of the plasma; - the target and the substrate holder are arranged facing each other. <EOS>