Method for selectively and remotely removing germanium oxide in hafnium oxide-silicon germanium gate stack interface layer
By depositing a germanium oxide scavenging layer on the hafnium oxide-silicon germanium gate stack and absorbing the oxygen atoms of germanium oxide by an annealing process, the problem of difficulty in removing germanium oxide in the prior art is solved, and a high-quality interface layer is achieved, which enhances the potential of high-performance CMOS applications.
Patent Information
- Application Number
- CN202510073762.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-01-17
- Publication Date
- 2025-05-13
AI Technical Summary
The prior art is difficult to effectively remove germanium oxide in SiGe pFETs with high germanium concentration, resulting in poor interface quality and limiting the potential of high-performance CMOS applications.
By depositing a germanium oxide scavenging layer on the hafnium oxide-silicon germanium gate stack, a metal element with a Gibbs free energy less than a germanium element absorbs oxygen atoms of germanium oxide to form a more chemically stable metal oxide, and selective remote scavenging of germanium oxide is achieved through an annealing process.
Effectively remove germanium oxide in the interface layer without affecting silicon oxide, realize a single silicon oxide interface layer, improve interface quality, and the process steps are simple and compatible with the standard Si CMOS process.
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Figure CN119993824A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the field of semiconductors and integrated circuits, and in particular relates to a method for selectively and remotely removing germanium oxide in an interface layer of a hafnium oxide-silicon germanium gate stack. Background Art
[0002] As the scaling of traditional silicon complementary metal oxide semiconductor (CMOS) devices approaches its physical limit, new process methods are needed to improve device performance. One promising solution is to use high-mobility materials as the channel material of transistors, and silicon germanium (SiGe) has significant advantages as the channel material of p-type field effect transistors (pFET). Silicon germanium has multiple advantages over silicon channel materials, including higher hole mobility, improved negative bias temperature instability characteristics, and better threshold voltage tunability.
[0003] In order to fully utilize the advantages of SiGe channel materials, it is necessary to achieve low interface trap density (Interface Trap Density, D it ) high-k / SiGe gate stack. However, the typical high-k / SiGe gate stack faces the problem of it The significant challenges caused by the increase of GeO2, especially in high-Ge concentration SiGe pFETs, severely limit their potential for high-performance CMOS applications. x ) is the main reason for poor interface quality. To solve this problem, researchers have explored a variety of methods, including nitridation, sulfurization passivation, trimethylaluminum pretreatment, and preferential silicon oxidation. However, these methods are ineffective in completely eliminating GeO x Or it is not effective in suppressing its regrowth during subsequent thermal treatment processes (such as high-k deposition and post-deposition annealing). Therefore, the development of effective GeO x Cleaning technology is critical to improving the high-k / SiGe interface. Summary of the invention
[0004] The present invention aims to improve the performance of GeO x In order to solve the shortcomings of the cleaning technology, a method for selectively and remotely cleaning germanium oxide in the interface layer of hafnium oxide-silicon germanium gate stack is proposed.
[0005] The object of the present invention is achieved through the following technical solution: a method for selectively and remotely removing germanium oxide in the interface layer of hafnium oxide-silicon germanium gate stack, the method comprising:
[0006] Depositing a germanium oxide scavenging layer on the hafnium oxide-silicon germanium gate stack, wherein the germanium oxide scavenging layer contains a metal element having a Gibbs free energy smaller than that of germanium;
[0007] An annealing process is performed to break the germanium-oxygen bond of germanium oxide in the silicon-germanium oxide mixed interface layer, and oxygen atoms are absorbed by the metal elements in the germanium oxide scavenging layer to form a metal oxide with higher chemical stability;
[0008] The germanium oxide removal layer is removed, completing the selective remote germanium oxide removal process step.
[0009] Furthermore, the gate stack is formed by stacking a silicon germanium substrate, a silicon germanium oxide mixed interface layer, and hafnium oxide in sequence from bottom to top.
[0010] Furthermore, the germanium oxide scavenging layer is a metal layer or is doped with a metal element with high chemical activity; the Gibbs free energy corresponding to the metal element in the germanium oxide scavenging layer is smaller than the Gibbs free energy corresponding to the germanium element, so that it can form metal oxide by remotely absorbing oxygen atoms of germanium oxide in the hafnium oxide / silicon germanium oxide mixed interface layer during the annealing process.
[0011] Furthermore, according to different metal elements in the germanium oxide removal layer, a corresponding annealing temperature is selected. The temperature should be selected so that germanium oxide in the silicon germanium oxide mixed interface layer is removed while maintaining the stability of silicon-oxygen bonds in silicon oxide and preventing hafnium oxide from crystallizing.
[0012] Furthermore, the annealing process needs to be performed in a vacuum or nitrogen environment to prevent oxygen in the annealing environment from oxidizing the metal elements in the scavenger layer.
[0013] Furthermore, the germanium oxide cleaning layer needs to be removed after the annealing process is performed, and the removal process cannot affect the quality of the underlying hafnium oxide layer.
[0014] The beneficial effects of the present invention are as follows: first, the present invention can effectively remove germanium oxide in the interface layer without affecting silicon oxide, thereby realizing hafnium oxide-silicon germanium gate stacking of a single silicon oxide interface layer and improving interface quality. Second, the process steps adopted by the present invention are simple and highly compatible with standard Si CMOS processes. BRIEF DESCRIPTION OF THE DRAWINGS
[0015] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.
[0016] Figure 1 is a schematic diagram of the cross-sectional structure of the hafnium oxide-silicon germanium gate stack in the present invention;
[0017] Figure 2 is the functional relationship between the Gibbs free energy of formation of the corresponding oxides of germanium, silicon, hafnium and aluminum elements and the temperature in the present invention;
[0018] Figure 3 This is a process flow chart of the selective remote germanium oxide removal process of the present invention;
[0019] Figure 4 Figure 1 is an actual data diagram of a hafnium oxide-silicon germanium gate stack after a germanium oxide removal process according to an embodiment of the present invention, wherein (a) is a function relationship between the Ge 2p XPS spectrum and the PDA annealing temperature, and (b) is a function relationship between the percentage of silicon and germanium atoms in the interface layer and the PDA annealing temperature. DETAILED DESCRIPTION
[0020] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific implementation methods.
[0021] It should be clear that the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present application.
[0022] The terms used in the embodiments of the present application are only for the purpose of describing specific embodiments, and are not intended to limit the application. The singular forms "a", "said" and "the" used in the embodiments of the present application and the appended claims are also intended to include plural forms, unless the context clearly indicates other meanings.
[0023] The present invention provides a method for selectively and remotely removing germanium oxide from the interface layer of hafnium oxide-silicon germanium gate stack, wherein the following is ... x O y ) is used as an example of a germanium oxide removal layer to describe the implementation process of the present invention in detail.
[0024] Figure 1The cross-sectional structure diagram of the hafnium oxide-silicon germanium gate stack of the present invention is shown in FIG. The gate stack is formed by stacking a silicon germanium substrate, a silicon germanium oxide mixed interface layer, and hafnium oxide in sequence from bottom to top.
[0025] Figure 2 is the functional relationship between the Gibbs free energy of the oxides corresponding to the germanium, silicon, hafnium and aluminum elements and the temperature, and the calculation formula of the Gibbs free energy ΔG is:
[0026] ΔG=ΔH-TΔS
[0027] Among them, ΔH is the reaction enthalpy change, ΔS is the reaction entropy change, and T is the reaction temperature. When ΔG<0, the energy of the system decreases after the reaction, indicating that the reaction can proceed spontaneously. The larger the absolute value of ΔG, the faster the reaction rate. On the contrary, when ΔG>0, the reaction is non-spontaneous and tends to proceed in the reverse direction. Figure 2 As shown in the figure, the oxide formation energy of the metal Al element is much smaller than that of the Ge element, so the Al-doped germanium oxide removal layer can be used to achieve germanium oxide removal at a suitable annealing temperature. At the same time, since there is also a significant difference in the oxide formation energy of silicon and germanium elements, by optimizing the annealing process, the stability of the silicon-oxygen bond can be maintained while removing germanium oxide, thereby achieving a selective germanium oxide removal process.
[0028] Figure 3 This is a process flow chart of the selective remote germanium oxide removal process in the present invention, which mainly includes:
[0029] (1) Substrate preparation
[0030] The silicon germanium substrate is epitaxially prepared on a lightly doped silicon wafer by reduced pressure chemical vapor deposition. The thickness of the silicon germanium epitaxial layer is 20 nm and the germanium concentration is 27%.
[0031] (2) Formation of silicon germanium oxide mixed interface layer
[0032] The silicon germanium oxide mixed interface layer is formed by chemical oxidation of a diluted Ammonium Peroxide Mixture (APM) solution, and its thickness is less than 1 nm.
[0033] (3) ALD hafnium oxide layer deposition
[0034] Atomic layer deposition (ALD) is used to grow a 1.5nm hafnium oxide layer as the gate stack high dielectric material. TDMAHf and H2O are used as ALD reaction precursors.
[0035] (4) Germanium oxide scavenging layer deposition
[0036] 10nm Al-rich Al was deposited by atomic layer deposition (ALD) technologyx O y As a germanium oxide removal layer. By utilizing the formation energy gain of aluminum and germanium when forming metal oxides, under appropriate annealing conditions, germanium oxide can be effectively removed. At the same time, thanks to the strong barrier properties of aluminum oxide to oxygen diffusion, Al-rich Al x O y It can not only provide a chemical driving force for the removal of germanium oxide during the annealing process, but also act as a barrier layer to prevent external oxygen atoms from diffusing into the hafnium oxide film, thereby inhibiting the regrowth of germanium oxide and ensuring the smooth progress of the germanium oxide removal reaction.
[0037] (5) Post-deposition annealing (PDA)
[0038] Al-rich Al x O y / HfO2 / SiGeO x The SiGe / SiGe samples were placed in a tubular furnace annealing chamber and annealed at 500°C, 600°C, 700°C, and 750°C for 1 minute respectively in a N2 atmosphere.
[0039] (6) Germanium oxide removal layer removal
[0040] Removal of Al-rich Al by chemical wet etching with developer x O y After removing the layer, rinse with deionized water and blow dry with a nitrogen gun to complete the selective remote germanium oxide removal process.
[0041] Figure 4 Graph showing actual data of a hafnium oxide-silicon germanium gate stack after a germanium oxide removal process according to an embodiment of the present invention. Figure 4 (a) is HfO2 / SiGeO x Ge 2p XPS photoelectron spectra of the GeO / SiGe gate stack after the germanium oxide removal process at different temperatures. As shown in the figure, with the increase of annealing temperature, GeO x The peak intensity gradually weakened and finally reached GeO at 750℃. x The peak disappeared completely. Figure 4 (b) is HfO2 / SiGeO x The percentage of silicon and germanium atoms in the interface layer of the SiGe / SiGe gate stack changes with the germanium oxide removal process at different temperatures. Consistent with the trend of the Ge 2pXPS photoelectron spectrum, the proportion of germanium oxide in the interface layer gradually decreases with the increase of the removal process temperature, reaching GeO at 750°C. x These results demonstrate the feasibility and correctness of the selective remote removal method of germanium oxide proposed in the present invention.
[0042] The above embodiments are merely examples of the present invention. Although the best embodiments and drawings of the present invention are disclosed for illustrative purposes, those skilled in the art will appreciate that various substitutions, changes and modifications are possible without departing from the spirit and scope of the present invention and the appended claims. Therefore, the present invention should not be limited to the contents disclosed in the best embodiments and drawings.
Claims
1. A method for selectively and remotely removing germanium oxide from an interface layer of a hafnium oxide-silicon germanium gate stack, characterized in that: include: Depositing a germanium oxide scavenging layer on the hafnium oxide-silicon germanium gate stack, wherein the germanium oxide scavenging layer contains a metal element having a Gibbs free energy smaller than that of germanium; An annealing process is performed to break the germanium-oxygen bond of germanium oxide in the silicon-germanium oxide mixed interface layer, and oxygen atoms are absorbed by the metal elements in the germanium oxide scavenging layer to form a metal oxide with higher chemical stability; The germanium oxide removal layer is removed, completing the selective remote germanium oxide removal process step.
2. The method for selectively and remotely removing germanium oxide from the interface layer of the hafnium oxide-silicon germanium gate stack according to claim 1, characterized in that: The gate stack is formed by stacking a silicon germanium substrate, a silicon germanium oxide mixed interface layer, and hafnium oxide in sequence from bottom to top.
3. The method for selectively and remotely removing germanium oxide from the interface layer of hafnium oxide-silicon germanium gate stack according to claim 1, characterized in that: The germanium oxide scavenging layer is a metal layer or is doped with a metal element with high chemical activity; the Gibbs free energy corresponding to the metal element in the germanium oxide scavenging layer is smaller than the Gibbs free energy corresponding to the germanium element, so that it can form metal oxide by remotely absorbing oxygen atoms of germanium oxide in the hafnium oxide / silicon germanium oxide mixed interface layer during the annealing process.
4. The method for selectively and remotely removing germanium oxide from the interface layer of hafnium oxide-silicon germanium gate stack according to claim 1, characterized in that: According to different metal elements in the germanium oxide removal layer, the corresponding annealing temperature is selected. The temperature should be selected so that the germanium oxide in the silicon germanium oxide mixed interface layer is removed while the silicon oxygen bond in the silicon oxide is kept stable and the hafnium oxide does not crystallize.
5. The method for selectively and remotely removing germanium oxide from the interface layer of hafnium oxide-silicon germanium gate stack according to claim 1, characterized in that: The annealing process needs to be performed in a vacuum or nitrogen environment to prevent oxygen in the annealing environment from oxidizing the metal elements in the scavenging layer.
6. The method for selectively and remotely removing germanium oxide from the interface layer of hafnium oxide-silicon germanium gate stack according to claim 1, characterized in that: The germanium oxide removal layer needs to be removed after the annealing process is performed, and the removal process must not affect the quality of the underlying hafnium oxide layer.