METHOD FOR MANUFACTURING SIMOX WAFER

Abstract

There is obtained an MLD-SIMOX wafer having a BOX layer with a thin film thickness that allows a reduction in SOI layer surface roughness and interface roughness of the BOX layer and the SOI layer and an improvement in breakdown voltage. In a method for manufacturing a SIMOX wafer comprising a step of forming a first ion-implanted layer in a silicon wafer; a step of forming a second ion-implanted layer that is in an amorphous state; and a high-temperature heat treatment state of maintaining the wafer in an atmosphere containing oxygen at a temperature that is not lower than 1300° C. but lower than a silicon melting point to change the first and the second ion-implanted layers into a BOX layer, the method is characterized in that a dose amount for the first ion-implanted layer is 1.25 to 1.5×1017 atoms/cm2, a dose amount for the second ion-implanted layer is 1.0×1014 to 1×1016 atoms/cm2, a step of preheating the wafer to a temperature that is not lower than 50° C. but lower than 200° C. is further included before the step of forming the second ion-implanted layer, and the second ion-implanted layer is formed in a state where it is continuously heated to a preheating temperature.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view showing a method for manufacturing a SIMOX wafer according to the present invention;

FIG. 2 is an enlarged view of a part A in FIG. 1(c) showing peaks and distributions of a first ion-implanted layer and a second ion-implanted layer in the SIMOX wafer according to the present invention;

FIG. 3 is a view showing a profile of a temperature and a time corresponding to FIGS. 1(a) to 1(d) according to an embodiment of the present invention;

FIG. 4( a) is a view showing a relationship between an ion dose amount and SOI layer surface roughness at a preheating temperature in a second ion-implanted layer forming step, and FIG. 4(b) is a view showing a relationship between an ion dose amount and interface roughness of the SOX layer and a BOX layer at the preheating temperature;

FIG. 5( a) is a view showing a relationship between an ion dose amount and a breakdown voltage of the BOX layer at the preheating temperature in the second ion-implanted layer forming step, and FIG. 5(b) is a view showing a relationship between an ion dose amount and a breakdown electric field of the BOX layer at the preheating temperature; and

FIG. 6( a) is a view showing a relationship between an ion dose amount and a thickness of the SOI layer at the preheating temperature in the second ion-implanted layer forming step, and FIG. 6(b) is a view showing a relationship between an ion dose amount and a thickness of the BOX layer at the preheating temperature.

Claims

1. A method for manufacturing a SIMOX wafer sequentially comprising: heating a wafer to a temperature in the range of 200 to 600° C. and implanting oxygen ions from a surface of a silicon wafer in an ion implanting device and to form a first ion-implanted layer having a peak oxygen concentration at a depth d1 from the surface of the wafer;implanting the oxygen ions from the surface of the wafer having the first ion-implanted layer formed therein in the ion implanting device to form a second ion-implanted layer that is in an amorphous state such that the second ion-implanted layer has a damage peak at a depth d2 wherein depth d2 is shallower than depth d1 and becomes continuous with a surface of the first ion-implanted layer on a front surface side of the wafer; andsubjecting the wafer to a high temperature heat treatment in a furnace in an atmosphere containing oxygen wherein the temperature is elevated to not lower than 1300° C. but lower than the melting point of silicon to change the first and the second ion-implanted layers into a BOX layer, wherein an oxygen ion dose amount for formation of the first ion-implanted layer is 1.25 to 1.5×1017 atoms/cm2, an oxygen ion dose amount for formation of the second ion-implanted layer is 1.0×1014 to 1.0×1016 atoms/cm2, the wafer is preheated to a temperature to at least 50° C. but lower than 200° C. before forming the second ion-implanted layer, and the second ion-implanted layer is formed while continuously heating the wafer to the preheating temperature.

2. The method of claim 1 wherein depth d1 is from 0.2 to 0.5 μm.

3. The method of claim 2 wherein depth d1 is from 0.3 to 0.45 μm.

4. The method of claim 1 wherein the implantation of the oxygen ions is carried out at an implantation energy of 100 to 200 keV.

5. The method of claim 4 wherein the implantation of the oxygen ions is carried out at an implantation energy of 120 to 180 keV.

6. The method of claim 1 wherein after forming the first implantation layer, the wafer is cooled, and thereafter cleaned and dried prior to being subjected to the implantation of the second implantation layer.

7. The method of claim 1 wherein the wafer is preheated to a temperature from 100° C. to 150° C.

8. The method of claim 1 wherein the oxygen implantation of the preheated wafer is carried out by beam implantation in a manner such that the damage d2 peak s maintained.

9. The method of claim 8 wherein the implantation is carried out in a vacuum.

10. The method of claim 1 wherein the dose amount for the formation of the second ion implanted layer is from 1.0×1015 to 1.0×1016 atoms/cm2

11. The method of claim 1 wherein the oxygen ions for the second ion implanted layer are implanted by beam irradiation.

12. The method of claim 11 wherein the oxygen ions are implated in a manner such that depth d2 is from 0.2 to 0.4 μm.

13. The method of claim 12 wherein the oxygen ions are implated in a manner such that depth d2 is from 0.3 to 0.35 μm.

14. The method of claim 1 wherein an ion implantation energy of 100 to 200 keV is used.

15. The method of claim 14 wherein the ion implantation energy is from 120 to 180 keV.

16. The method of claim 14 wherein the difference between the ion implantation energy for forming the second ion implantation layer and the first ion implantation layer is from 0 to 50 kev.

17. The method of claim 16 wherein the difference between the ion implantation energy for forming the second ion implantation layer and the first ion implantation layer is from 0 to 20 keV.

18. The method of claim 1 wherein a plurality of wafers having the first and second ion implantation layers formed therein are sequentially, one by one, removed from the ion implanting device and cleaned, dried and subjected to the high temperature heat treatment in a heat treatment furnace.

19. The method of claim 18 wherein the temperature in the furnace is from 1320 to 1350° C.

20. The method of claim 19 wherein the wafer is held at this temperature for 6 to 36 hours.

21. The method of claim 19 wherein the wafer is held at this temperature for 12 to 24 hours.

22. The method of claim 1 wherein after the heat treatment, the wafer is cooled to room temperature.

23. The method of claim 1 wherein during the temperature elevation the atmosphere in the furnace during the heat treatment is a mixture of an inert gas and oxygen.

24. The method of claim 23 wherein the inert gas is selected from the group consisting of argon, nitrogen and mixtures thereof.

25. The method of claim 23 wherein the amount of oxygen is from 0 to 5.0 volume %.

26. The method of claim 25 wherein the amount of oxygen is from 0.5 to 1.0 volume %.

27. The method of claim 1 wherein after the temperature elevation, the atmosphere in the furnace contains from 5.0 to 100.0 volume % of oxygen.

28. The method of claim 27 wherein after the temperature elevation, the atmosphere in the furnace contains from 10.0 to 50.0 volume % of oxygen.

29. The method of claim 27 wherein the atmosphere of the furnace also contains an inert gas selected from the group consisting of argon, nitrogen and mixtures thereof.

30. A SIMOX wafer prepared by the method of claim 1.