Source: http://www.google.de/patents/US20060081847
Timestamp: 2013-05-25 09:56:53
Document Index: 412715504

Matched Legal Cases: ['art 14', 'art 14', 'art 14', 'art 14', 'art 14', 'art 15', 'art 14', 'art 15', 'art 15', 'art 15']

Patent US20060081847 - Methods for fabricating a wafer structure having a strained silicon utility ... - Google PatenteSuche Bilder Maps Play YouTube News Gmail Drive Mehr » Erweiterte Patentsuche | Webprotokoll | Anmelden Erweiterte Patentsuche PatenteMethods for fabricating a wafer structure having a strained silicon utility layer are described. In an embodiment, the method includes providing a prototype wafer having at least a support substrate and a strained silicon model layer upon the support substrate, and then providing a relaxed silicon-germanium...http://www.google.de/patents/US20060081847?utm_source=gb-gplus-sharePatent US20060081847 - Methods for fabricating a wafer structure having a strained silicon utility layer Ver�ffentlichungsnummerUS20060081847 A1PublikationstypAnmeldung Anmeldenummer11/080,936 Ver�ffentlichungsdatum20. Apr. 2006Eingetragen14. M�rz 2005 Priorit�tsdatum19. Okt. 2004Auch ver�ffentlicht unterCN1767148ACN100369191CEP1650794A1EP1650794B1US7465646 Ver�ffentlichungsnummerUS 2006/0081847 A1US2006/0081847A1 ErfinderYves-Matthieu Le VaillantUrspr�nglich Bevollm�chtigterLe Vaillant Yves-Matthieu US-Klassifikation257/65257/74438/478257/617257/E21.129438/458Internationale KlassifikationH01L21/20H01L29/30 UnternehmensklassifikationH01L21/02658H01L21/02502H01L21/02381H01L21/02532H01L21/0245H01L21/02032H01L21/02664 Europ�ische KlassifikationH01L21/02D2RExterne LinksUSPTO USPTO-Zuordnung EspacenetMethods for fabricating a wafer structure having a strained silicon utility layerUS 20060081847 A1 Zusammenfassung Methods for fabricating a wafer structure having a strained silicon utility layer are described. In an embodiment, the method includes providing a prototype wafer having at least a support substrate and a strained silicon model layer upon the support substrate, and then providing a relaxed silicon-germanium layer on the strained silicon model layer. Next, a strained silicon utility layer is provided on the relaxed silicon-germanium layer to form an intermediate structure. The strained silicon utility layer has substantially the same characteristics as the strained silicon model layer. The method also includes detaching the strained silicon utility layer from the intermediate structure at a predetermined zone of weakness in the relaxed silicon-germanium layer to form a wafer structure having a strained silicon utility layer. Zeichnungen(4) Anspr�che
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a schematic view of a silicon-on-insulator (SOI) prototype wafer 4. The prototype wafer 4 includes a silicon substrate 1, an insulator layer 2 formed thereon, and a strained silicon model layer 3 on top. The silicon substrate 1 supports the insulator layer 2 and the strained silicon model layer 3. The insulator layer 2 may be, for example, made of silicon dioxide, and in other examples may be made of silicon nitride or another insulating material or insulating materials. The strained silicon model layer 3 has been formed on the prototype wafer, for example, by using a SMART-CUT� process. Alternatively, the layer 3 can be formed by another method known in the art. FIG. 2 illustrates another prototype wafer 6 that includes a silicon substrate 1, an insulator layer 2, a silicon-germanium (SiGe) layer 5, and a strained silicon model layer 3 on top. The germanium content of the relaxed SiGe layer 5 determines the strain of the strained silicon model layer 3 that is on top of the relaxed SiGe layer 5. The prototype wafer 6 can be formed by using the SMART-CUT� process, or by using any other process known in the art. FIG. 3 illustrates the prototype wafer 4 of FIG. 1 after epitaxially growing a further strained silicon model layer 7. The characteristics of the additional strained silicon model layer 7 are substantially similar to the characteristics of the strained silicon model layer 3. The additional strained silicon model layer 7 effectively increases the thickness of the strained silicon model layer 3, which serves to compensate for any loss of thickness during a subsequent recycling step involving the prototype wafer. FIG. 4 illustrates the structure of FIG. 3 after formation of a relaxed auxiliary SiGe layer 8 on the additional strained silicon model layer 7. The relaxed auxiliary SiGe layer 8 has, in this example, a constant germanium content. FIG. 5 shows the structure of FIG. 4 after formation of a strained silicon utility layer 11 on the relaxed auxiliary SiGe layer. The strained silicon utility layer 11 has strain characteristics which are substantially the same as the strain characteristics of the strained silicon model layer 7. The properties of the strained silicon layers 7 and 11 are duplicated or cloned by means of the relaxed auxiliary SiGe layer between the strained silicon layers 7 and 11. FIG. 5 shows an embodiment of an intermediate structure according to the present invention, which consists of the prototype wafer 4, the relaxed auxiliary SiGe layer 8 with a predetermined weakened zone 9 formed therein, and a top strained silicon utility layer 11. FIG. 6 schematically shows the structure of FIG. 5 during an implantation step. In FIG. 5, atomic species 10 are implanted into a certain depth of the relaxed auxiliary SiGe layer 8 to form predetermined weakened zone 9 therein. The structure of the SiGe layer is weakened at the predetermined weakened zone 9 so that a mechanical force, or a thermal influence, or shockwaves can be applied to delaminate or detach a structure at the predetermined weakened zone as shown in FIG. 6. FIG. 7 illustrates the structure of FIG. 6 after formation of an SiGe utility layer 12 on the strained silicon utility layer 11. The SiGe utility layer 12 together with the strained silicon utility layer 11 forms at least a part of a utility structure, which may be a silicon-geranium-on-insulator (SGOI) utility structure. FIG. 8 shows the surface of the SiGe utility layer of the structure of FIG. 7 bonded to a second wafer 13. The second wafer 13 forms a support for the SiGe utility layer 12 and the strained silicon utility layer 11 during detachment, and the second wafer is thereafter a good carrier for the SiGe utility layer 12 and the strained silicon utility layer 11. In particular, the structure of FIG. 8 is detached after the bonding step by using, for example, a mechanical force, a thermal influence, or shockwaves, or a combination of such forces or influences. The structure of FIG. 8 is separated along the predetermined zone of weakness 9 resulting in the two structures, the first shown in FIG. 9 and the second shown in FIG. 11. FIG. 9 shows one detached part of the structure of FIG. 8 after the detachment step. The first detached part includes the second wafer 13, the SiGe utility layer 12, the strained silicon utility layer 11, and a residual part 14 which is a part of the former relaxed auxiliary SiGe layer 8. Although the surface of the residual part 14 shown in FIG. 9 appears to be relatively flat, in reality the surface can be very rough. It is therefore advantageous to smooth at least the surface of the residual part 14. A chemical mechanical polishing step, or a selective chemical etching step, or a combination of these processes could be used to remove the rough surface structure. FIG. 10 illustrates a useful structure 16 that results after removal of the residual part 14 shown in FIG. 9. A chemical etching step could be used to remove the residual part 14. For example, a chemical etching step with high selectivity of about 1:30 between the material of the former relaxed auxiliary SiGe layer 8 and the strained silicon utility layer 11 could be used. For example, a CH3COOH/H2O2/H2O solution with respective concentration of 4/3/0.25, or a NH4OH/H2O2/H2O solution with a respective concentration of 1/1/5 could be utilized. FIG. 11 schematically shows a second structure that results after the detachment step occurs with regard to the structure shown in FIG. 8. The second structure shown in FIG. 11 consists of the silicon support substrate 1, the insulator layer 2, the strained silicon model layer 3, the epitaxially grown second strained silicon model layer 7, and a residual part 15 of the former relaxed auxiliary SiGe layer 8. As mentioned above with regard to the residual part 14, the surface of the residual part 15 can also be relatively rough, so that smoothing of at least the surface of this layer 15 is necessary before the second structure can be recycled. FIG. 12 schematically shows a recycle structure 17 after a recycling step in which the residual part 15 shown in FIG. 11 is removed. The residual part 15 is preferably removed by a selective chemical etching step using the high etch selectivity of the material of the former relaxed auxiliary SiGe layer 8, and the additional or second strained silicon model layer 7, of about 1:30. The structure of FIG. 12 can then be recycled and used again, wherein a new relaxed auxiliary SiGe layer is formed thereon as discussed earlier with regard to FIG. 4 to repeat the entire process wherein the characteristics of the strained silicon model layer 3 are duplicated. In summary, a method for fabricating a wafer structure with a strained silicon layer includes providing a prototype wafer having a support substrate and having a top strained silicon model layer. Next, a relaxed auxiliary SiGe layer is epitaxially grown on the strained silicon model layer, and a strained silicon utility layer is grown on the auxiliary SiGe layer. Then a portion of the structure is detached at a predetermined weakened zone created in the relaxed SiGe layer. Thus, according to the invention, the methods for fabricating the wafer structure having a strained silicon layer has two main steps. The first is to fabricate the prototype wafer which forms a model for a utility structure, and the second is the formation of the utility structure by duplicating or cloning the characteristics of the strained silicon model layer of the prototype wafer by forming the strained silicon utility layer. Using the inventive method, the properties of the strained silicon model layer can be directly transferred to the strained silicon utility layer by using the auxiliary SiGe layer as a transmission layer between the strained silicon layers. A simple succession beginning with the strained silicon model layer, and then the auxiliary SiGe layer results in a strained silicon utility layer that is formed with a high quality in a very short time. It is furthermore relatively easy to detach a utility structure from the prototype wafer part of the structure, and to proceed separately thereafter with both structures. According to a favorable embodiment, the method further includes removing a residual part of the auxiliary SiGe layer from the strained silicon utility layer after the detachment step. This allows for recycling of the detached utility structure. The utility structure can easily be recycled because the high etch selectivity between the relaxed auxiliary SiGe layer and the strained silicon utility layer provides for a beneficial utility structure. In an advantageous example, the strained silicon model layer is epitaxially grown before the auxiliary SiGe layer is grown thereon. The epitaxially grown strained silicon layer compensates for any loss of thickness of the strained silicon layer during a recycling step, which can result if a chemical solution having an imperfect etching selectivity is used. In yet another favorable embodiment, the method further includes implanting atomic species into the auxiliary SiGe layer to create the predetermined zone of weakness therein. The implantation step can create a well-defined predetermined zone of weakness which can be detached mechanically, thermally, or by using shockwaves or other forces very efficiently. In another example, the technique may include bonding a second wafer onto the strained silicon utility layer. The second wafer provides a good stable support for the strained silicon utility layer during the detachment step, and can form a good basis for further use of the strained silicon utility layer. It is also advantageous for the method to include growing an SiGe utility layer on the strained silicon utility layer before the detachment step. This way, an SGOI (silicon-germanium-on-insulator) utility structure can be formed after detachment. In another example, the method includes bonding a second wafer onto the SiGe utility layer. The second wafer can form a good basis for the resulting utility structure, and can provide a good, stable support during the detachment step. Preferably, the prototype wafer is an SOI structure consisting of a silicon support substrate, at least one insulator layer, and the strained silicon model layer directly on the insulator layer. Such a structure has to be produced only once in a conventional manner as described above, and can then serve as a model for duplicating the characteristics of the strained silicon model layer many times. In another variant, the prototype wafer is an SGOI structure consisting of a silicon support substrate, at least one insulator layer, an SiGe layer, and a strained silicon model layer. This structure can also be formed in a conventional manner, wherein the strain of the strained silicon model layer depends on the germanium concentration of the SiGe layer. The structure has to be produced only once and can serve several times for cloning or duplicating the characteristics of a strained silicon model layer. In another advantageous embodiment, the method includes removing a residual part of the auxiliary SiGe layer from the strained silicon model layer after detachment. This allows for recycling of the prototype wafer after detachment. It is very easy to remove the auxiliary SiGe layer from the strained silicon model layer because there is a good etch selectivity between these layers. In another aspect, an intermediate structure is provided that is suitable to fabricate a wafer structure having a strained silicon layer. The technique includes providing a prototype wafer having a support substrate and a strained silicon model layer, a relaxed auxiliary SiGe layer on the strained silicon model layer wherein a predetermined zone of weakness is formed in the relaxed auxiliary SiGe layer, and providing a strained silicon utility layer on the auxiliary SiGe layer. The thickness of the relaxed SiGe auxiliary layer should be sufficient to incorporate the defects that may be introduced by the implantation process and by the detachment step, typically >200 nm. The intermediate structure includes a strained silicon model layer having characteristics that are directly transferred or duplicated to the strained silicon utility layer. The intermediate product forms a structure which can be easily detached along the predetermined zone of weakness formed in the relaxed auxiliary SiGe layer, so that the strained silicon utility layer can be used separately from the prototype wafer after detachment. In yet another embodiment, the intermediate structure includes a second wafer bonded onto the strained silicon utility layer. The second wafer can form a good support for the strained silicon utility layer during the detaching step and/or after detachment. In another advantageous example, the intermediate structure includes an SiGe utility layer on the strained silicon utility layer. With this structure an SGOI (silicon-germanium-on-insulator) utility structure can be formed after the detachment step. Preferably, the intermediate structure also includes a second or further epitaxially grown strained silicon layer between the strained silicon model layer and the auxiliary SiGe layer. The second strained silicon layer can help to compensate for any changes in thickness of the strained silicon model layer during recycling of the prototype wafer. According to a favorable variant, the prototype wafer is an SOI wafer consisting of a silicon support substrate, at least one insulator layer, and the strained silicon model layer. This type of prototype wafer only needs to be formed once in a conventional manner, and then can be used thereafter several times to transfer the strained silicon model layer characteristics to the strained silicon utility layer of the inventive structure. In a yet further example, the prototype wafer is an SGOI wafer consisting of a silicon support substrate, at least one insulator layer, an SiGe layer, and the strained silicon model layer. The characteristics of the strained silicon model layer of such a prototype wafer can be controlled by the germanium content of the SiGe layer of the prototype wafer. As described above, this type of prototype wafer need only be produced once and then can be used often to clone or duplicate the characteristics of the strained silicon model layer when forming the strained silicon utility layer. It should be understood that, although the steps of the present process illustrated herein have been shown and described in FIGS. 3 to 12 in relation to the prototype wafer 4 of FIG. 1, these steps can also be applied to other prototype wafers. For example, the prototype wafer 6 of FIG. 2 could be used, or another type of prototype wafer having at least a support substrate and strained silicon layer which can be used as strained silicon model layer could be utilized. DrehenOriginalbildGoogle-Startseite - Sitemap - USPTO-Bulk-Downloads - Datenschutzerkl�rung - Nutzungsbedingungen - �ber Google Patente - Feedback gebenDaten bereitgestellt von IFI CLAIMS Patent Services.© 2012 Google