Preparation method of GeOI substrate structure through ion implantation technology

Abstract

The invention discloses a preparation method of a GeOI substrate structure through an ion implantation technology, and belongs to the field of semiconductor design and manufacturing, and the method comprises the steps: preparing a first wafer and a second wafer; generating a germanium-silicon layer on the surface of the first wafer; performing a hydrogen ion implantation process on the first wafer to form a weakening layer in the germanium-silicon layer; combining the surface of the germanium-silicon layer of the first wafer with a second wafer through a bonding process; stripping along the weakening layer, and forming a top layer germanium-silicon film on the second wafer on the remaining part; recrystallizing the top germanium-silicon thin film through thermal annealing treatment, and simultaneously converting the top germanium-silicon thin film into a double-layer structure of a top germanium thin film and a silicon thin film; oxygen ions are injected into the silicon thin film through an oxygen ion injection process, so that the silicon thin film is converted to be embedded into the silicon dioxide layer; and recrystallizing the top germanium film through thermal annealing treatment. The thickness of the top germanium film is controllable, the uniformity of the film is good, the surface defects are few, and the contact interface between the top germanium film and the embedded silicon dioxide layer is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of semiconductor design and manufacturing, and particularly relates to a preparation method of a GeOI substrate structure by an ion implantation process. Background Art

[0002] As the Bulk CMOS technology node reaches below 28 nm, during the continuous miniaturization of the feature size of MOSFET transistors, although their operating speed is getting faster and faster, the short channel effects (SCE) are becoming more and more significant. Based on the silicon material itself, it has also approached the physical and technical limits. Therefore, innovative technologies are needed for the preparation process and device structure to achieve further development. The traditional planar MOSFET structure is no longer applicable. Among potential technologies, a channel structure composed of a heteromaterial structure, especially a high carrier mobility material such as a silicon-germanium material, is an effective technology and has become a solution for advanced chips. For example, directly bonding germanium to a silicon wafer with a silicon dioxide insulating layer to form a GeOI structure (Ge on Insulator) is a silicon-germanium material with a high hole mobility and has excellent application development prospects. For transistors prepared by GeOI technology, the germanium thin film defines the source-drain junction depth and depletion region, which can improve short channel effects such as DIBL (Drain Induced Barrier Lowering), further improve the subthreshold characteristics of the device, and reduce the static power consumption of the circuit. In addition, GeOI transistors do not require channel doping, which can avoid effects such as RDF (Random Dopants Fluctuation) and the reduction of carrier mobility, and maintain a stable threshold voltage (threshold voltage, Vth).

[0003] Different from the 3D transistor structure adopted by the FinFET process, GeOI is a planar process technology, which can effectively reduce the process difficulty; compared with the traditional Bulk Silicon technology, GeOI can provide better transistor electrostatic characteristics, and the buried oxide layer can reduce the parasitic capacitance between the source and the drain; in addition, this technology can effectively limit the electron flow between the source and the drain, significantly reducing the leakage current performance of the device. In addition to through the gate, GeOI can also control the transistor behavior through the bottom substrate of the device to achieve the back bias control function. However, the disadvantage of the existing technology is that in GeOI technology, if a germanium material layer is directly formed on the insulating oxide layer, due to the relatively poor contact interface between the germanium material and the insulating oxide, especially the high interface state density, it will cause serious scattering and leakage, thereby affecting the device performance. Summary of the Invention

[0004] Based on the technical problems existing in the prior art, the present invention provides a preparation method of a GeOI substrate structure by an ion implantation process, which solves the problems that the contact interface between the top germanium thin film and the insulating oxide in the GeOI substrate structure of the existing process is relatively poor, and the thickness of the top germanium thin film is difficult to prepare, difficult to achieve ultra-thin and not easy to control, the film thickness at the crystal edge is uneven and there are many surface defects, etc., realizes more controllable process precision, the prepared GeOI substrate structure has better effects, and significantly improves the device performance.

[0005] According to the technical solution of the present invention, the present invention provides a preparation method of a GeOI substrate structure by an ion implantation process, including the following steps carried out in sequence:

[0006] Step S1, prepare a first wafer and a second wafer, both the first wafer and the second wafer are bare wafers of the wafer substrate;

[0007] Step S2, form a germanium-silicon layer on the surface of the first wafer;

[0008] Step S3, perform a hydrogen ion implantation process on the first wafer to form a weakening layer in the germanium-silicon layer of the first wafer;

[0009] Step S4, after surface cleaning of the first wafer and the second wafer, combine the surface of the germanium-silicon layer of the first wafer with the second wafer through a bonding process;

[0010] Step S5, strip the first wafer and part of the germanium-silicon layer along the weakening layer, and the remaining part forms the top germanium-silicon thin film on the second wafer;

[0011] Step S6, perform recrystallization on the top germanium-silicon thin film through a thermal annealing treatment. At the same time, convert the top germanium-silicon thin film into a double-layer structure of a top germanium thin film and a silicon thin film, and the top germanium thin film is located above the silicon thin film;

[0012] Step S7, through an oxygen ion implantation process, implant oxygen ions into the silicon thin film to convert the silicon thin film into a buried silicon dioxide layer;

[0013] Step S8, perform recrystallization on the top germanium thin film through a thermal annealing treatment.

[0014] In some embodiments, in step S3, the process parameters of the hydrogen ion implantation include an implantation energy of 50 keV to 200 keV and an implantation dose of 1×1016 atoms / cm2 to 1×1018 atoms / cm2; and / or, the temperature condition of the hydrogen ion implantation is ≤60 °C.

[0015] In some embodiments, in step S4, the bonding process is a low-temperature bonding process, and the bonding process temperature is ≤200 °C.

[0016] In some embodiments, in step S6, the thermal annealing treatment is a high-temperature thermal annealing treatment, and the temperature of the thermal annealing treatment is ≥ 800 °C.

[0017] In some embodiments, in step S6, the temperature of the thermal annealing treatment is ≤ 900 °C.

[0018] In some embodiments, in step S6, the thermal annealing treatment adopts a furnace tube annealing or a laser annealing process.

[0019] In some embodiments, after step S6, the top germanium thin film reaches the required ultra-thin thickness, and the ultra-thin thickness is ≤ 20 nm.

[0020] In some embodiments, in step S7, the temperature condition for oxygen ion implantation is ≤ 0 °C.

[0021] In some embodiments, in step S8, the thermal annealing treatment is a high-temperature thermal annealing treatment, and the temperature of the thermal annealing treatment is ≥ 500 °C.

[0022] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0023] In the preparation method of the GeOI substrate structure of the present invention by an ion implantation process, a weakening layer is formed by hydrogen ion implantation, which facilitates subsequent peeling to form a flat surface; through a bonding process, preferably a low-temperature bonding process, the contact interface is improved; then through a thermal annealing treatment, on the one hand, germanium is recrystallized to eliminate the lattice structure damage caused by the previous process such as hydrogen ion implantation, and a better electrical result is obtained, and on the other hand, germanium and silicon are stratified, and germanium will be separated to the upper layer of silicon due to diffusion, so as to form the required top germanium thin film; then an embedded oxide layer is formed by oxygen ion implantation; in the GeOI substrate structure prepared by the method of the present invention, the thickness of the top germanium ultra-thin film is controllable, the film uniformity is good, the surface of the GeOI substrate structure is relatively flat, the surface defects are few, and good single-crystallinity is maintained. Description of the Drawings

[0024] Figure 1 is a flowchart of the method provided by the present invention.

[0025] Figures 2 to 8 is a schematic structural diagram of the process of gradually obtaining the FD-SOI substrate structure by using the method of the present invention.

[0026] Figure 9 is a relationship curve diagram of the thermal annealing temperature in step S6 of the present invention and the time required for the top germanium-silicon thin film to be converted into a bilayer structure.

[0027] Description of the reference numerals in the drawings:

[0028] A, the first wafer; B, the second wafer; 1, the germanium-silicon layer; 2, the weakening layer; 3, the top germanium-silicon thin film; 4, the top germanium thin film; 5, the silicon thin film; 6, the buried silicon dioxide layer. Detailed implementation manners

[0029] To make the objectives, technical solutions and advantages of the present invention clearer, the technical solutions in the present invention will be clearly and completely described below with reference to the accompanying drawings in the present invention. Apparently, the described embodiments are some but not all of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present invention without creative efforts shall fall within the protection scope of the present invention.

[0030] In addition, it should be noted that for the convenience of description, only parts related to the relevant invention are shown in the drawings. Without conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other.

[0031] It should be noted that the concepts such as "first" and "second" mentioned in the present invention are only used to distinguish different devices, modules or units, and are not used to limit the order or interdependence relationship of the functions performed by these devices, modules or units.

[0032] It should be noted that the modifications of "one" and "multiple" mentioned in the present invention are illustrative rather than restrictive. Those skilled in the art should understand that unless clearly specified otherwise in the context, it should be understood as "one or more".

[0033] The present invention provides a preparation method of a GeOI substrate structure by an ion implantation process, that is, a preparation method of a GeOI substrate structure including an ion implantation process, belonging to the field of semiconductor design and manufacturing. A typical preparation method includes: preparing two bare wafer substrates A and B; depositing a germanium-silicon thin film (SiGe Deposition) on the surface of wafer A; performing a hydrogen ion implantation process on wafer A; first cleaning the surfaces of wafers A and B, and then performing a low-temperature bonding (Bonding); peeling off wafer A to form a top germanium-silicon thin film, and then performing recrystallization (Re-crystallization) on the top germanium-silicon thin film by high-temperature thermal annealing; forming a germanium thin film and a silicon thin film by high-temperature thermal annealing treatment; using a low-temperature oxygen ion implantation process to form a buried oxide (Buried Oxide) thin film, and performing high-temperature thermal annealing treatment. Without changing the sandwich structure of the GeOI substrate structure, the present invention improves the preparation method of GeOI, solves the problems that the contact interface between the top germanium thin film and the insulating oxide in the GeOI substrate structure of the existing process is relatively poor, and the thickness of the top germanium thin film is difficult to prepare, difficult to achieve ultra-thin and not easy to control, the film thickness of the crystal edge is uneven and there are many surface defects, etc., realizes more controllable process precision, the prepared GeOI substrate structure has better effects, and significantly improves the device performance.

[0034] Please refer to Figures 1 to 8 , a preparation method of a GeOI substrate structure by an ion implantation process according to the present invention, includes the following steps carried out in sequence.

[0035] Step S1, prepare a first wafer A and a second wafer B, and both the first wafer A and the second wafer B are bare wafer substrates. This step S1 corresponds to Figure 2 the initial state shown.

[0036] Step S2, generate a germanium-silicon layer 1 on the surface of the first wafer A. In the embodiment, specifically, perform germanium-silicon thin film deposition (SiGe Deposition) on the surface of the first wafer A, and the process temperature is, for example, above 450 °C to form the germanium-silicon layer 1. The state after this step S2 is as Figure 3 shown.

[0037] Step S3, perform a hydrogen ion implantation process on the first wafer A to form a weakening layer 2 in the germanium-silicon layer 1 of the first wafer A. The weakening layer 2 is the hydrogen implantation layer, and a weakening structure is formed at a certain depth in the germanium-silicon layer 1 through hydrogen ion implantation to facilitate peeling in subsequent steps. The state of performing hydrogen ion implantation in this step S3 is as Figure 4 shown.

[0038] Step S4, after the surfaces of the first wafer A and the second wafer B are cleaned, the surface of the germanium-silicon layer 1 of the first wafer A is bonded to the second wafer B through a bonding process. In the embodiment, when performing the bonding process, the first wafer A is flipped and inverted on the upper surface of the second wafer B. Preferably, the bonding process is a low-temperature bonding process, and the bonding process temperature is, for example, ≤200°C. The state after this step S4 is as shown in Figure 5 shown.

[0039] Step S5, the first wafer A and a part of the germanium-silicon layer 1 are peeled off along the weakening layer 2, and the remaining part forms the top germanium-silicon thin film 3 on the second wafer B. The state of the peeling process in this step S5 is as shown in Figure 6 shown.

[0040] Step S6, the top germanium-silicon thin film 3 is recrystallized through a thermal annealing process. At the same time, the top germanium-silicon thin film 3 is transformed into a bilayer structure of a top germanium thin film 4 and a silicon thin film 5, and the top germanium thin film 4 is located above the silicon thin film 5. Preferably, after step S6, the top germanium thin film 3 reaches the required ultra-thin thickness, and the ultra-thin thickness is ≤20 nm. The state after this step S6 is as shown in Figure 7 shown.

[0041] It should be noted that in step S6, the thermal annealing process is a high-temperature thermal annealing process, and the temperature of the thermal annealing process is preferably ≥800°C. At this temperature, germanium in the top germanium-silicon thin film 3 can diffuse upward relatively quickly and finally be divided into two layers. Within a certain range, the higher the thermal annealing temperature, the shorter the time required for stratification, but the temperature should not be too high. Preferably, the temperature of the thermal annealing process is ≤900°C. The relationship between the thermal annealing temperature and the stratification time of the top germanium thin film is as shown in Figure 9 shown. The thermal annealing process adopts a furnace tube annealing or a laser annealing process; the laser annealing requires a shorter time, but the cost is relatively high. In addition, in this step S6, both recrystallization and stratification are achieved through a one-step thermal annealing process; for example, when the temperature reaches about 600°C, the recrystallization process starts to occur significantly, repairing the lattice structure damaged by hydrogen ion implantation. Continuing to heat, when the temperature reaches above 800°C, the stratification process starts to occur significantly, and the required bilayer structure can be formed after about dozens of minutes.

[0042] Step S7, through an oxygen ion implantation process, oxygen ions are implanted into the silicon thin film 5 to transform the silicon thin film 5 into a buried silicon dioxide layer 6. The state of this step S7 is as shown in Figure 8 shown.

[0043] Step S8, the top germanium thin film 4 is recrystallized through a thermal annealing process. Preferably, the thermal annealing process is a high-temperature thermal annealing process, and the temperature of the thermal annealing process is, for example, ≥500°C. Thus, a GeOI substrate structure is obtained, and the GeOI substrate structure is a substrate (i.e., the second wafer B), a buried silicon dioxide layer 6, and a top germanium thin film 4 stacked in sequence.

[0044] Preferably, in step S3, the process parameters of hydrogen ion implantation include an implantation energy of 50 keV to 200 keV and an implantation dose of 1×1016 atoms / cm2 to 1×1018 atoms / cm2; and / or, the temperature condition for hydrogen ion implantation is ≤60°C. Preferably, in step S7, oxygen ion implantation is low-temperature oxygen ion implantation. More specifically, the temperature condition for oxygen ion implantation is ≤0°C. By using the low-temperature ion implantation process, ion diffusion during ion implantation can be avoided, and ions can be controlled to be uniformly implanted into a certain position inside the wafer with precise position and narrow distribution range; similarly, the temperature of hydrogen ion implantation should not be too high; furthermore, in the case of low-temperature implantation, a lower dose of implantation can be selected to further avoid lattice damage and reduce defects.

[0045] In summary, in the preparation method of the GeOI substrate structure of the present invention through the ion implantation process, a weakening layer is formed by hydrogen ion implantation to facilitate subsequent peeling to form a flat surface; through the bonding process, preferably the low-temperature bonding process, the contact interface is improved; then through thermal annealing treatment, on the one hand, germanium-silicon recrystallization is carried out to eliminate the lattice structure damage caused by previous processes such as hydrogen ion implantation and obtain better electrical results, and on the other hand, germanium and silicon are stratified, and germanium will be separated to the upper layer of silicon due to diffusion, thus forming the required top germanium thin film; then an embedded oxide layer is formed by oxygen ion implantation; in the GeOI substrate structure prepared by the method of the present invention, the thickness of the top germanium ultra-thin film is controllable, the film uniformity is good, the surface of the GeOI substrate structure is relatively flat, the surface defects are few, and good single-crystallinity is maintained.

[0046] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a GeOI substrate structure by ion implantation, characterized in that: The method comprises the following steps in sequence: Step S1, preparing a first wafer (A) and a second wafer (B), wherein the first wafer (A) and the second wafer (B) are both wafer substrate bare chips; Step S2, forming a silicon germanium layer (1) on the surface of the first wafer (A); Step S3, performing a hydrogen ion implantation process on the first wafer (A) so as to form a weakened layer (2) in the germanium silicon layer (1) of the first wafer (A); Step S4, after cleaning the surfaces of the first wafer (A) and the second wafer (B), the surface of the germanium silicon layer (1) of the first wafer (A) is bonded to the second wafer (B) through a bonding process; Step S5, peeling off the first wafer (A) and part of the germanium silicon layer (1) along the weakened layer (2), and the remaining part forms a top germanium silicon film (3) on the second wafer (B); Step S6, recrystallizing the top germanium silicon film (3) by thermal annealing, and at the same time, converting the top germanium silicon film (3) into a double-layer structure of a top germanium film (4) and a silicon film (5), wherein the top germanium film (4) is located above the silicon film (5); Step S7, injecting oxygen ions into the silicon film (5) through an oxygen ion implantation process, so that the silicon film (5) is converted into a buried silicon dioxide layer (6); Step S8, recrystallizing the top germanium film (4) by thermal annealing.

2. The method for preparing the GeOI substrate structure by ion implantation process according to claim 1, characterized in that: In step S3, the process parameters of hydrogen ion implantation include implantation energy: 50keV~200keV, implantation dose: 1×1016atoms / cm2~1×1018atoms / cm2; and / or, the temperature condition of hydrogen ion implantation is ≤60°C.

3. The method for preparing the GeOI substrate structure by ion implantation process according to claim 1, characterized in that: In step S4, the bonding process is a low-temperature bonding process, and the bonding process temperature is ≤200°C.

4. The method for preparing the GeOI substrate structure by ion implantation process according to claim 1, characterized in that: In step S6, the thermal annealing treatment is a high temperature thermal annealing treatment, and the temperature of the thermal annealing treatment is ≥ 800°C.

5. The method for preparing a GeOI substrate structure by ion implantation according to claim 4, characterized in that: In step S6, the temperature of the thermal annealing treatment is ≤ 900°C.

6. The method for preparing a GeOI substrate structure by ion implantation according to claim 1, characterized in that: In step S6, the thermal annealing treatment adopts furnace annealing or laser annealing process.

7. The method for preparing a GeOI substrate structure by ion implantation according to claim 1, characterized in that: After step S6, the top germanium film (4) reaches the required ultra-thin thickness, which is ≤20 nm.

8. The method for preparing a GeOI substrate structure by ion implantation according to claim 1, characterized in that: In step S7, the temperature condition for oxygen ion implantation is ≤ 0°C.

9. The method for preparing a GeOI substrate structure by ion implantation according to claim 1, characterized in that: In step S8, the thermal annealing treatment is a high temperature thermal annealing treatment, and the temperature of the thermal annealing treatment is ≥500°C.

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