In-situ germanium concentration method based on high-density strong-bond-energy oxide / GeOx / SiGe stacking and application of in-situ germanium concentration method

Abstract

The invention discloses an in-situ germanium concentration method based on high-density strong-bond-energy oxide / GeOx / SiGe stacking and application of the in-situ germanium concentration method, and belongs to the field of semiconductors and integrated circuits. According to the method, on the basis of an in-situ germanium concentration method based on GeOx / SiGe stacking, a high-density strong-bond-energy oxide layer represented by AlOx is additionally arranged above a GeOx layer, and a high-density strong-bond-energy oxide / GeOx / SiGe three-layer stacking structure is formed. The high-density strong-bond-energy oxide layer inhibits GeO analysis and blocks external oxygen invasion, so that the annealing atmosphere does not need to be strictly oxygen-free, and the germanium atom percentage increment is more than two times of that of the layer. According to the method, the process compatibility is expanded, the germanium concentration efficiency is improved, and the method is suitable for mass production scenes of high-node devices such as 3D FinFET fins and nanosheets.

Description

Technical Field

[0001] This invention belongs to the field of semiconductors and integrated circuits, specifically relating to a high-density strong bond energy oxide / GeO... x In-situ germanium enrichment method for SiGe stacks and its application. Background Technology

[0002] Silicon-germanium (SiGe) materials have become core materials for channel engineering in 3D integrated circuits (such as FinFETs and nanosheet devices) due to their high carrier mobility and stress tunability. Existing GeO-based materials... x In-situ germanium enrichment method using SiGe stacks via GeO x The solid-state reaction with the SiGe layer enables in-situ redistribution of germanium atoms, breaking through the critical thickness limit of traditional epitaxy. The percentage of germanium atoms can be increased to 35%-45%, and it is compatible with CMOS production lines.

[0003] However, this method has the following limitations: First, annealing requires strict control of an oxygen-free environment (oxygen concentration <10). -3 The first is that the gas atmosphere control in mass production processes is more difficult and the equipment cost is higher (apm); the second is GeO x Germanium atoms in the layer can easily escape as GeO gas through the reaction "Si + 2GeO2 = SiO2 + 2GeO", resulting in the loss of germanium atoms and limiting the increase in germanium concentration (the maximum increase is about 15%). In the mass production of 3D devices, the above-mentioned limitations restrict the further improvement of process stability and device performance. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of existing GeO... x To address the shortcomings of the SiGe stacked in-situ germanium enrichment method, an improved method based on a composite stacking structure is proposed. By adding a high-density, strongly bonded oxide layer, the annealing atmosphere requirements are relaxed and the germanium enrichment efficiency is improved.

[0005] The objective of this invention is achieved through the following technical solution: a high-density strong bond energy oxide / GeO x An in-situ germanium enrichment method for SiGe stacks, comprising:

[0006] SiGe layers and GeO layers are epitaxially grown sequentially on a silicon substrate. x Layers and high-density strong bond energy oxide layers, forming a high-density strong bond energy oxide layer / GeO x / SiGe three-layer stacking structure;

[0007] During the annealing process, the high-density, strongly bonded oxide layer acts as a barrier, inhibiting GeO desorption and preventing external oxygen intrusion, thus enabling GeO to... xGe atoms in the layer migrate to the SiGe layer and form a high-concentration in-situ germanium-concentrated SiGe layer.

[0008] Further, the working principle of the high-density strong-bond-energy oxide layer is:

[0009] Physical barrier effect: inhibiting the escape of GeO gas in the reaction, forcing GeO to re-decompose into germanium atoms within the layer and participate in the concentration of the SiGe layer;

[0010] Oxygen barrier effect: reducing the oxygen diffusion coefficient (≤1×10 -20 cm 2 / s) through a high-density lattice structure to avoid the loss of germanium caused by the reaction of external oxygen with the SiGe layer.

[0011] Further, the high-density strong-bond-energy oxide layer is represented by AlO x , and can also be selected from MgO, ZrO2, etc., which have a high-density lattice (density ≥ 3.0 g / cm 3 ) and strong chemical bonds (such as Al-O bond energy of about 670 kJ / mol).

[0012] Further, by adjusting the thickness of the high-density strong-bond-energy oxide layer to adapt to different annealing atmospheres, specifically: when the thickness of the high-density strong-bond-energy oxide layer is ≥ 2 nm and ≤ 5 nm, the annealing atmosphere is inert and the oxygen impurity concentration needs to be ≤ 10 -2 apm; when the thickness of the high-density strong-bond-energy oxide layer is > 5 nm and < 20 nm, the annealing atmosphere is inert and the oxygen impurity concentration needs to be ≤ 10 -1 apm; when the thickness of the high-density strong-bond-energy oxide layer is ≥ 20 nm, direct annealing in an air atmosphere can meet the process requirements.

[0013] Further, the temperature of the annealing process is 350-1000℃, which promotes the reaction of GeO x with the SiGe layer through thermodynamic driving; due to the inhibition of GeO decomposition loss by the high-density strong-bond-energy oxide layer, the percentage increase of germanium atoms is more than 2 times that without the high-density strong-bond-energy oxide layer, and the final percentage of germanium atoms in the SiGe layer can reach 50%-65%.

[0014] Further, the initial percentage of germanium atoms in the SiGe layer is 10%-30%, and the thickness is 5-50 nm; the thickness of the GeO x layer is 1-20 nm.

[0015] Further, a composite oxide layer is covered on the in-situ germanium-concentrated SiGe layer, and the composite oxide layer is generated by the reaction of SiO xand a high-density strong-bonding oxide layer, and a part of unreacted GeO x The composite oxide layer can be reserved in whole or in part according to subsequent process requirements, and used as a mask layer of the subsequent process to reduce the photolithography step.

[0016] The application also provides a semiconductor structure formed by the in-situ germanium concentration method, which comprises a silicon substrate and an in-situ germanium concentration SiGe layer on the silicon substrate, the in-situ germanium concentration SiGe layer has a germanium atom percentage of 10% to 65% from inside to surface along the thickness direction, and the thickness can reach ≥ 15 nm, thereby breaking through the traditional critical thickness limit; a composite oxide layer is covered on the in-situ germanium concentration SiGe layer, the composite oxide layer is composed of a SiO x layer with a thickness of ≥ 1 nm and a high-density strong-bonding oxide layer with a thickness of ≥ 2 nm, and a part of unreacted GeO x The surface roughness after removing the composite oxide layer is ≤ 0.4 nm.

[0017] Further, the in-situ germanium concentration SiGe layer has a germanium atom percentage of ≥ 50% in the surface 10 nm depth range, and is suitable for a channel region of a 3D FinFET fin or nanosheet.

[0018] The application also provides application of the in-situ germanium concentration method in a 3D integrated circuit device, for preparing a channel region of a vertical fin or horizontal nanosheet structure, which comprises: forming a germanium atom percentage gradient (≤ 15% at the bottom and ≥ 50% at the top) in the longitudinal section of the fin / nanosheet to inhibit stress-induced dislocation; using a composite oxide layer composed of a SiO x layer with a thickness of ≥ 1 nm and a high-density strong-bonding oxide layer with a thickness of ≥ 2 nm generated by the reaction as a self-aligned etching mask to realize smoothing of the fin / nanosheet sidewall, and the sidewall roughness Rz is ≤ 0.5 nm.

[0019] The in-situ germanium concentration method provided by the application is compatible with the CMOS process, the annealing process does not need to introduce halogen gas or high-temperature water vapor, and the method is integrated into the existing epitaxy-annealing-etching process to reduce 2-3 photolithography processes (using the oxide layer as a mask); the loss rate of the traditional oxidation method is ≥ 25%, and the germanium atom loss of the method is almost zero, and the material utilization rate is increased by more than 5 times.

[0020] The application has the following beneficial effects:

[0021] 1. The annealing atmosphere requirement is relaxed: no strict oxygen-free environment is needed, and when the thickness of the high-density strong-bonding oxide layer is more than 20 nm, the annealing can be performed in an air atmosphere, thereby reducing the process control difficulty and equipment cost;

[0022] 2. Improve germanium concentration efficiency: The percentage of germanium atoms is increased by more than 2 times of the existing method, and can be as high as 65%, significantly enhancing the channel conductivity;

[0023] 3. Reduce annealing temperature: To achieve the same percentage of germanium atom increment effect, the required temperature is lower;

[0024] 4. Enhance process compatibility: Compatible with existing CMOS production line, integrated in epitaxial-annealing-etching process, using composite oxide layer as a mask can reduce 2-3 photoetching processes;

[0025] 5. Optimize structure stability: The surface roughness of the composite oxide layer is lower, which can improve the etching precision when used as a mask, and is suitable for 3D device mass production scenarios. BRIEF DESCRIPTION OF DRAWINGS

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor on the basis of these drawings.

[0027] Figure 1 SiGe epitaxial substrate prepared according to device requirements in the present application;

[0028] Figure 2 SiGe fin diagram prepared according to device requirements in the present application;

[0029] Figure 3 Composite stack initial structure, i.e. in-situ germanium concentration initial structure diagram of the present application;

[0030] Figure 4 Structure diagram after in-situ germanium concentration of the present application;

[0031] Figure 5 X-ray photoelectron spectroscopy of the in-situ germanium concentration before and after the embodiment 1 of the present application and the existing method, and the germanium atom percentage change diagram calculated therefrom;

[0032] Figure 6 X-ray photoelectron spectroscopy of the in-situ germanium concentration before and after the embodiment 2 of the present application and the existing method, and the germanium atom percentage change diagram calculated therefrom. DETAILED DESCRIPTION

[0033] The following describes some of the possible embodiments of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. It is not intended to identify the key or decisive elements of the present invention or to limit the scope of protection. It is readily understood that, based on the technical solutions of the present invention, those skilled in the art can propose other interchangeable implementations without changing the essential spirit of the present invention. Therefore, the following detailed descriptions and accompanying drawings are merely exemplary illustrations of the technical solutions of the present invention and should not be considered as the entirety of the present invention or as limitations or restrictions on the technical solutions of the present invention.

[0034] Example 1:

[0035] Figures 1-4 The AlO-based embodiments of the present invention provide x The process flow diagram for in-situ germanium enrichment using / GeO2 / SiGe stacking includes the following steps:

[0036] First, the preparation of a low-germanium-content SiGe epitaxial layer includes the following steps:

[0037] (a) such as Figure 1 As shown, a SiGe layer is epitaxially grown on a silicon substrate, wherein the thickness of the SiGe layer is 5-50 nm. In this embodiment, the thickness of the SiGe layer is selected as 20 nm, but it is not limited to this. In other embodiments, the thickness of the SiGe layer can be adjusted as needed. In addition, the percentage of germanium atoms in the SiGe layer is 10%-30%, and in this embodiment, it is selected as 25%, but it is not limited to this. In other embodiments, the percentage of germanium atoms can be adjusted as needed. This is hereby stated.

[0038] (b) such as Figure 2 As shown, the desired SiGe structure is obtained by etching. Typically, this region can be a planar device structure channel shape or a 3D device structure such as a fin shape. In this embodiment, a 3D device structure is used, with a length of 2-3 μm, a width of 20-100 nm, and a height of 50-100 nm. In other embodiments, the etching shape and size can be adjusted according to the device requirements.

[0039] Secondly, the preparation of the in-situ germanium enrichment stacking structure includes the following steps:

[0040] (a) Clean with a standard RCA solution to remove surface contaminants and activate the surface;

[0041] (b) Sequentially depositing 1-20 nm thick GeO2 and 2-20 nm thick AlO2 layers on the SiGe surface using atomic layer deposition (ALD) or magnetron sputtering (PVD). x In this embodiment, the thickness of the GeO2 layer is selected as 4nm, and the AlO layer thickness is...x The layer thickness was chosen to be 5 nm to form AlO x / GeO2 / SiGe stacking structure, such as Figure 3 As shown. In other embodiments, the GeO2 layer and AlO2 layer can be adjusted according to actual needs. x The thickness.

[0042] Finally, the in-situ germanium concentration was achieved through the following process:

[0043] AlO x The / GeO2 / SiGe stacked structure is placed in a rapid thermal treatment system, such as a rapid thermal reactor, and 5000ccm of nitrogen (N2) is introduced as a protective gas, with an oxygen impurity concentration ≤10%. -2 APM heats the reactor at a rate of 50°C per second until it reaches 550-900°C, then stops heating and begins holding the temperature. In this embodiment, the stop temperature is set to 700°C. In other embodiments, the stop temperature can be adjusted as needed. After holding the temperature under N2 atmosphere for 10-120 seconds, the holding temperature is stopped. Then, under N2 atmosphere, the reactor temperature is cooled down to 200°C at a rate of 10-30°C per second. Figure 4 This is a schematic diagram of the structure after the in-situ germanium concentration reaction has stopped. It includes the unconcentrated SiGe region, the concentrated SiGe region with high germanium concentration, and the remaining oxides after the reaction. Figure 5 Before and after in-situ germanium enrichment and without AlO x The percentage change of germanium atoms in the SiGe substrate after in-situ germanium concentration of the layer was measured by X-ray photoelectron spectroscopy (XPS).

[0044] Example 2:

[0045] This embodiment is based on AlO x The process flow for in-situ germanium enrichment using / GeO2 / SiGe stacks is basically the same as in Example 1, except that the process parameters in the steps of "preparation of in-situ germanium enrichment stack structure" and "realization of in-situ germanium enrichment" are somewhat different, as are the final results. Details are as follows:

[0046] The preparation of in-situ germanium enrichment stacking structures includes the following steps:

[0047] (a) Clean with a standard RCA solution to remove surface contaminants and activate the surface;

[0048] (b) A 10 nm thick GeO2 layer and a 20 nm thick AlO2 layer are sequentially deposited on the SiGe surface using atomic layer deposition (ALD) or magnetron sputtering (PVD). x Layers, forming AlO x In other embodiments, the GeO2 layer and AlO2 layer can be adjusted according to actual needs in the / GeO2 / SiGe stacking structure.x of the thickness.

[0049] The in-situ germanium concentration is achieved by the following process:

[0050] A 20 nm AlO x / 10 nm GeO2 / SiGe stack structure is placed in a rapid thermal processing system reaction furnace, without vacuum or high-purity inert gas protection, and is directly annealed in an atmospheric environment. The reaction furnace is heated at a speed of 50 °C per second until it reaches 550-900 °C, and then the temperature is stopped to start the holding. In this embodiment, the stop temperature is set to 750 °C, and in other embodiments, the stop temperature can be adjusted according to requirements. The holding is stopped after 30 seconds of continuous atmospheric environment. Then, the temperature is lowered at a speed of 10-30 °C per second until it reaches 200 °C, and then the temperature is stopped. The N2 gas used for equipment cooling does not need to be strictly filtered to improve purity.

[0051] The structure diagram after the in-situ germanium concentration reaction is stopped in this embodiment is the same as that in Embodiment 1, which includes an un-concentrated SiGe region, a high-germanium-concentration SiGe region after concentration, and residual oxide after reaction. Figure 6 The in-situ germanium concentration before and after concentration and the in-situ germanium concentration without using an AlO x layer are shown in FIG. 6. The in-situ germanium concentration structure sample without using an AlO x layer is annealed in the same way as the in-situ germanium concentration annealing process with an AlO x layer. According to the concentration calculation results of the XPS spectrum, the Ge concentration of the SiGe substrate after the in-situ germanium concentration with an AlO x layer is increased from 25% to 64.7%, which is much higher than 32% without using an AlO x layer. The latter causes the germanium concentration efficiency to be completely unexpected due to the desorption of GeO and the erosion of oxygen in the air.

[0052] It should be noted that in the above in-situ germanium concentration process, the purity requirement for the inert gas such as N2 is not as high as that of the unimproved in-situ germanium concentration process, and even a reasonable thickness of AlO x can be directly annealed in air, such as in Embodiment 2, because the high-density lattice structure and the extremely high Al-O bond can effectively prevent the diffusion of oxygen to the GeO2 / SiGe interface, and can avoid the influence of oxygen impurities on the quality of the SiGe fin after concentration due to poor equipment sealing or low purity of inert gas.

[0053] In this embodiment, the oxide after in-situ germanium concentration can be used as a hard mask in subsequent processes by etching or other methods, and in other embodiments, it can also be selected to be removed or retained as needed.

[0054] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions, alterations, deletions of some features, additions of features, or recombinations of features to the above embodiments within the scope of the present invention without departing from the principles and spirit of the present invention. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the innovative principles of the present invention shall still fall within the scope of the technical solutions of the present invention.

Claims

1. A method based on high-density strong bond energy oxides / GeO x The in-situ germanium enrichment method of SiGe stacking is characterized by... include: SiGe layers and GeO layers are epitaxially grown sequentially on a silicon substrate. x Layers and high-density strong bond energy oxide layers, forming a high-density strong bond energy oxide layer / GeO x / SiGe three-layer stacking structure; During the annealing process, the high-density, strongly bonded oxide layer acts as a barrier, inhibiting GeO desorption and preventing external oxygen intrusion, thus enabling GeO to... x Germanium atoms in the layer migrate directionally to the SiGe layer, forming a high-concentration in-situ germanium-rich SiGe layer.

2. The in-situ germanium concentration method according to claim 1, characterized in that, The high-density strong bond energy oxide layer is AlO. x It must contain at least one of MgO and ZrO2, with a lattice density ≥ 3.0 g / cm³. 3 .

3. The in-situ germanium concentration method according to claim 1, characterized in that, The thickness of the high-density, strongly bonded oxide layer is adjusted to suit different annealing atmospheres, specifically: When the thickness of the high-density strong bond energy oxide layer is ≥2nm and ≤5nm, the annealing atmosphere is inert and the oxygen impurity concentration must be ≤10. -2 apm; When the thickness of the high-density strong bond energy oxide layer is >5nm and <20nm, the annealing atmosphere is inert and the oxygen impurity concentration must be ≤10. -1 apm; When the thickness of the high-density strong bond oxide layer is ≥20nm, annealing in an air atmosphere can meet the process requirements.

4. The in-situ germanium concentration method according to claim 1, characterized in that, The annealing process is carried out at temperatures of 350-1000℃, which promotes the annealing of GeO through thermodynamic driving. x The reaction with the SiGe layer; due to the suppression of GeO desorption loss by the high-density strong bond energy oxide layer, the increase in the percentage of germanium atoms is more than twice that without the high-density strong bond energy oxide layer, and the final percentage of germanium atoms in the SiGe layer can reach 50%-65%.

5. The in-situ germanium concentration method according to claim 1, characterized in that, The initial germanium atom percentage of the SiGe layer is 10%-30%, and the thickness is 5-50 nm; the GeO layer... x The thickness of the layer is 1-20nm.

6. The in-situ germanium concentration method according to claim 1, characterized in that, The in-situ germanium-concentrated SiGe layer is covered by a composite oxide layer, which is composed of SiO2 generated by the reaction. x It consists of a layer and a high-density, strongly bonded oxide layer, and may also contain some unreacted GeO. x .

7. The in-situ germanium concentration method according to claim 6, characterized in that, Depending on the needs of subsequent processes, all or part of the composite oxide layer can be retained as a mask layer for subsequent processes, thereby reducing the number of photolithography steps.

8. A semiconductor structure formed using the in-situ germanium enrichment method according to any one of claims 1-7, characterized in that, The system includes a silicon-based substrate and an in-situ germanium-enriched SiGe layer on the silicon-based substrate, wherein the percentage of germanium atoms in the in-situ germanium-enriched SiGe layer increases from 10% to 65% along the thickness direction from the interior to the surface; a composite oxide layer is covered above the in-situ germanium-enriched SiGe layer, wherein the composite oxide layer is composed of SiO2 with a thickness ≥1 nm generated by reaction. x It consists of a layer and a high-density, strongly bonded oxide layer with a thickness of ≥2nm, and may also contain some unreacted GeO. x The surface roughness Ra after removing the composite oxide layer is ≤0.4nm.

9. The application of the in-situ germanium concentration method according to any one of claims 1-7 in 3D integrated circuit devices, characterized in that, The method is used to prepare channel regions of vertical fin or horizontal nanosheet structures, including: forming a germanium atom percentage gradient in the longitudinal cross-section of the fin / nanosheet, with a bottom ≤15% and a top ≥50%; utilizing SiO₂ with a thickness ≥1 nm generated by the reaction. x A composite oxide layer consisting of a layer and a high-density strong bond energy oxide layer with a thickness ≥2nm is used as a self-aligned etching mask to achieve smoothing of the sidewalls of fins / nanofalves, with a sidewall roughness Rz≤0.5nm.

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