Patent Number: 
Section: claims

1. An apparatus forming an electrical conduction path through an insulating layer on a surface of a substrate, the apparatus comprising:a first radiation source configured to emit radiation to a first region of the insulating layer;a first electrical contact configured to apply a first bias voltage to the first region;a second radiation source configured to emit radiation to a second region of the insulating layer; anda second electrical contact configured to apply a second bias voltage to the second region,wherein a positive bias voltage is applied by the first electrical contact, and a negative bias voltage is applied by the second electrical contact. 2. The apparatus of claim 1, wherein the radiation from the first radiation source passes through openings in the first electrical contact so as to impinge upon portions of the first region, and the radiation from the second radiation source passes through openings in the second electrical contact so as to impinge upon portions of the second region. 3. The apparatus of claim 2, wherein the first and second electrical contacts comprise conductive meshes which apply the bias voltages to the regions, and wherein the radiation from the radiation sources passes through openings in the conductive meshes. 4. The apparatus of claim 1, wherein the bias voltages are determined by using current-voltage characteristic data for the insulating layer. 5. The apparatus of claim 1 further comprising:an electron beam column for focusing an electron beam with a beam current onto the surface of the substrate. 6. The apparatus of claim 5, wherein a charging current is absorbed by the substrate from the beam current, and the apparatus conducts the charging current out of the substrate through the insulating layer. 7. The apparatus of claim 1, wherein the radiation sources generate ultraviolet light. 8. The apparatus of claim 1, wherein the radiation sources generate charged particles. 9. The apparatus of claim 8, wherein the charged particles comprise alpha particles. 10. The apparatus of claim 9, wherein the radiation source comprises americium. 11. A method of forming an electrical conduction path through an insulating layer, the method comprising:emitting radiation to a first region of the insulating layer;applying a first bias voltage to the first region;emitting radiation to a second region of the insulating layer; andapplying a second bias voltage to the second region,wherein a positive bias voltage is applied by the first electrical contact, and a negative bias voltage is applied by the second electrical contact. 12. The method of claim 11, wherein the radiation from the first radiation source passes through openings in the first electrical contact so as to impinge upon portions of the first region, and the radiation from the second radiation source passes through openings in the second electrical contact so as to impinge upon portions of the second region. 13. The method of claim 12, wherein the first and second electrical contacts comprise conductive meshes which apply the bias voltages to the regions, and wherein the radiation from the radiation sources passes through openings in the conductive meshes. 14. The method of claim 11 further comprising:determining the bias voltages using current-voltage characteristic data for the insulating layer. 15. The method of claim 11 further comprising:focusing an electron beam with a beam current onto the surface of the substrate;absorbing into the substrate a charging current from the beam current; andconducting the charging current out of the substrate through the insulating layer. 16. The method of claim 11, wherein the radiation sources generate ultraviolet light. 17. The method of claim 11, wherein the radiation sources generate charged particles. 18. The method of claim 17, wherein the charged particles comprise alpha particles. 19. The method of claim 18, wherein the radiation source comprises americium.