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.