Semiconductor device manufacturing: process – Introduction of conductivity modifying dopant into... – Plasma
Reexamination Certificate
1999-11-01
2002-02-05
Mulpuri, Savitri (Department: 2812)
Semiconductor device manufacturing: process
Introduction of conductivity modifying dopant into...
Plasma
Reexamination Certificate
active
06344404
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to the manufacture of substrates. More particularly, the invention provides a technique including a method and device for introducing ions into a substrate for fabricating silicon-on-insulator wafers using a separating process in a cost effective and efficient manner.
Techniques have been proposed or used for the manufacture of silicon-on-insulator (“SOI”) wafers. One of these techniques is called “separation by implantation of oxygen,” commonly termed SIMOX. A detailed description of this process is described in Stanley Wolf Ph.D., SILICON PROCESSING FOR THE VLSI ERA (Volume 2), pages 66-79, which are hereby incorporated by reference. This technique generally uses conventional beam-line ion implanters for introducing the oxygen into the silicon wafer.
A limitation with the conventional SIMOX process is generally the cost of the resulting wafer. This cost often stems from the long time needed to implant a sufficient dose of oxygen into the silicon wafer. Since ion implanters is often difficult to allocate the implanter for use in the conventional SIMOX process, which is often used for a variety of other integrated circuit processing operations. Additionally, many fabrication facilities (e.g., integrated circuit and wafer) simply cannot afford purchasing additional ion implantation equipment due to its excessive cost. Accordingly, silicon-on-insulator wafers made using the conventional SIMOX process are often costly and generally take a long time to fabricate.
Another technique for fabricating silicon-on-insulator wafer is commonly termed Smart Cut™. This technique uses conventional beam-line ion implantation equipment to introduce hydrogen to a selected depth into a substrate. The substrate is bonded to an insulating layer overlying a bulk substrate to form a multi-layered substrate structure. The multi-layered substrate is introduced into a furnace to increase the global temperature of the entire substrate, which blisters off a portion of substrate material from the substrate at the selected depth, thereby leaving a thin film of substrate material on the insulating material to form the silicon-on-insulator wafer. U.S. Pat. No. 5,374,564, which is in the name of Michel Bruel (“Bruel”), and assigned to Commissariat a l'Energie Atomique in France, describes this technique.
Unfortunately, the use of conventional beam line ion implantation equipment is quite expensive. In fact, the Smart Cut™ process generally requires large doses of hydrogen, which often takes a long time to implant. Additionally, the long time necessary to implant hydrogen by the implanter generally increases processing costs, which produces a higher cost wafer. Furthermore, the conventional beam line implanter often represents one of the highest equipment costs in a fabrication facility, which adds to the cost of producing the wafer. Numerous other limitations also exist with the use of the conventional beam line ion implantation equipment.
From the above, it is seen that a technique for fabricating a silicon-on-insulator wafer which is cost effective and efficient is often desirable.
SUMMARY OF THE INVENTION
According to the present invention, an improved technique for implanting substrates in the manufacture of wafers such as silicon-on-insulator wafers is provided. In particular, the present invention uses a plasma immersion ion implantation (“PIII”) process for introducing ions into a silicon wafer for fabricating a silicon-on-insulator substrate. The invention also can be applied to almost any application for removing a film(s) of material from a substrate.
In a specific embodiment, the present invention provides a method for fabricating substrates using a plasma immersion ion implantation (“PIII”) system. For example, see paper by N. W. Cheung, “Plasma Immersion Ion Implantation For Semiconductor Processing,” Material Chemistry and Physics, Vol. 46/2-3, pp. 132-139 (1996), which is hereby incorporated by reference for all purposes. See also X. Lu, S. S. K. Iyer, J. Min, Z. Fan, J. B. Liu, P. K. Chu, C. Hu, and N. W. Cheung, entitled “SOI Material Technology Using Plasma Immersion Ion Implantation,” Proceedings 1996 IEEE International SOI Conference (October 1996), which is also hereby incorporated by reference for all purposes. The method includes steps of providing a substrate and implanting particles such as ions from a plasma source with specific ion composition into a surface of the substrate to a first desired depth to provide a first distribution of the ions using the PIII system. The implanted ions define a first thickness of material above the implant. To remove the first thickness of material from the substrate, a step of increasing energy of the substrate to initiate a cleaving action is included. The cleaving action is sufficient to completely free the thickness of material from a remaining portion of the substrate. By way of the PIII system, the ions are introduced into the substrate in an efficient and cost effective manner. In some embodiments, the implanting step is a multiple implant step using different conditions to facilitate cleaving the thickness of material. These conditions include, for example, doses, energies, temperatures, species, among others.
In an alternative embodiment, the present invention provides another method for fabricating substrates using a plasma immersion ion implantation system. The method includes steps of providing a substrate and implanting particles (e.g., ions) into a surface of the substrate to a first desired depth to provide a first distribution of the ions using the plasma immersion ion implantation system. The implanted ions defines a first thickness of material above the implant. The first thickness of material is removed from the substrate at the first desired depth. By way of the PIII system, the ions are introduced into the substrate at an efficient and cost effective manner. In some embodiments, the implanting step is a multiple implant step(s) using different conditions to facilitate removing the thickness of material from the substrate. These conditions include, for example, doses, energies, temperatures, species, among others.
Numerous benefits are achieved by way of the present invention over pre-existing techniques. In particular, the present invention relies upon a PIII system which can easy introduce ions into a substrate in a relatively timely process. The PIII process is often significantly faster than conventional implanters, e.g., beam line. Additionally, the PIII process can be readily incorporated into conventional fabrication facilities in an efficient and cost effective manner. Accordingly, the present invention achieves these and others benefits described herein.
The present invention achieves these benefits and others in the context of known process technology. However, a further understanding of the nature and advantages of the present invention may be realized by reference to the latter portions of the specification and attached drawings.
REFERENCES:
patent: 5920764 (1999-05-01), Hanson et al.
patent: 5882987 (1999-06-01), Krikrishnan
patent: 6013563 (2000-01-01), Henley et al.
patent: 6027988 (2000-02-01), Cheung et al.
patent: 6048411 (2000-04-01), Henley et al.
patent: 6083324 (2000-07-01), Henley et al.
Cheung Nathan W.
Hu Chenming
Lu Xiang
Mulpuri Savitri
The Regents of the University of California
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