Preparation method of germanium-based source-drain material and application thereof

Abstract

The application relates to a preparation method of a germanium-based source-drain material and application thereof, and relates to the field of germanium-based source-drain materials. A germanium-aluminum thin film is grown on a germanium-based substrate through co-deposition of germanium and aluminum. When the substrate temperature is 215-383 DEG C, X-ray diffraction (XRD) tests show that the germanium-aluminum thin film is a single crystal structure, the crystal quality is good, and there is no segregation of aluminum on the surface. Hall test shows that the germanium-aluminum thin film is self-doped with p type, and the activated hole concentration is as high as 8*10 20 According to the characterization results of a time-of-flight secondary ion mass spectrometer (TOF-SIMS), the diffusion length of aluminum atoms on an undoped germanium-based substrate is less than 4 nm / decade, and the germanium-based source-drain material can be applied to the preparation of p-type in-situ doping and p+ / n shallow junction of an advanced node process of a germanium-based logic circuit.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of germanium-based source-drain materials, in particular to a preparation method of a germanium-based source-drain material and application thereof. BACKGROUND

[0002] With the feature size of transistors approaching the physical limit, it is increasingly difficult for the performance of logic chips to meet the growing demand for information processing capacity and speed, and the improvement of the performance of logic chips faces severe challenges. It is expected to further improve the performance of logic chips by replacing the silicon channel with germanium material with higher mobility. However, under the advanced logic circuit process node, the contact parasitic resistance of the source-drain doped region has become the main factor limiting the improvement of the performance of transistors. In addition, while achieving high active doping concentration, the traditional doping method is often accompanied by long-distance diffusion of impurity atoms in the substrate, which makes it difficult to accurately control the doped region, especially at the nanoscale. For example, in some existing doping technologies, the diffusion length of the doping atoms in the undoped germanium-based substrate can reach tens of nanometers or even further, which not only increases the transition region between the doped region and the undoped region, but also can adversely affect the performance of adjacent electronic devices.

[0003] To be compatible with the silicon process, it is required to obtain high active doping concentration of germanium at ≤400℃. The traditional ion implantation, in-situ doping method usually needs to combine high temperature treatment process to repair the lattice and / or activate and diffuse the dopant, which is incompatible with SiCMOS process, and it is difficult to accurately control the doping depth at the nanoscale. Phosphorus and boron are the most commonly used dopants in germanium, but the impurity activation energy is relatively high. Therefore, it is of great significance to develop a method for achieving high active concentration doping while effectively controlling the diffusion length of the doping atoms for improving the performance of logic circuits. SUMMARY

[0004] The present application aims to solve the above-mentioned problems in the prior art, and provides a preparation method of a germanium-based source-drain material and application thereof, which realizes high-quality, high-p-type in-situ aluminum-doped germanium material at a condition of 215-338℃, wherein the aluminum component can be greater than 3%, the activated hole concentration is up to 8×10 20 , and the diffusion length is less than 4nm / decade, which can be applied to the preparation of p-type in-situ doping and p+ / n shallow junction of advanced node process of logic circuits.

[0005] To achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0006] The application of a germanium-based source-drain material is used for the preparation of p-type in-situ doping and p+ / n shallow junction of advanced node process of logic circuits, the germanium-based source-drain material is a germanium aluminum thin film grown on a germanium-based substrate by co-deposition of germanium and aluminum, the germanium aluminum thin film has p-type doping, and the activated hole concentration is up to 8×1020 The diffusion length of aluminum atoms in the germanium-based substrate is less than 4 nm / decade.

[0007] The preparation method of the germanium-based source-drain material comprises the following steps: first, pretreating the germanium-based substrate; then, placing the germanium-based substrate into a magnetron sputtering system, vacuumizing and heating to deposit a germanium-based buffer layer; and finally, performing epitaxy of a germanium-aluminum single crystal thin film through co-deposition of germanium and aluminum.

[0008] The pretreatment of the germanium-based substrate comprises ultrasonic cleaning of the germanium-based substrate in acetone, ethanol and deionized water respectively.

[0009] The pretreatment of the germanium-based substrate comprises soaking the germanium-based substrate in a dilute hydrochloric acid solution and then rinsing with deionized water.

[0010] The pretreatment of the germanium-based substrate comprises soaking the germanium-based substrate in a dilute hydrofluoric acid solution and then rinsing with deionized water.

[0011] The co-deposition of germanium and aluminum is performed at a deposition temperature of 215-338 DEG C.

[0012] Compared with the prior art, the technical scheme of the present application has the following beneficial effects:

[0013] The present application epitaxially grows a germanium-aluminum thin film with high crystal quality on a germanium-based substrate (including germanium, silicon-germanium, germanium-tin, germanium-lead, etc.) by optimizing growth parameters. Germanium and aluminum atoms are co-deposited at a substrate temperature of 215-338 DEG C, and a germanium-doped layer with a high p-type activation concentration (the highest doped concentration measured by Hall test is 8*10 20 ) is obtained, and aluminum atoms do not diffuse obviously, with a diffusion length of less than 4 nm / decade, so that the doped region can be accurately controlled in nanoscale, and the adverse effects caused by long-distance diffusion are avoided. This makes the present application particularly suitable for p-type in-situ doping and preparation of p+ / n shallow junctions in advanced node processes of logic circuits. Moreover, the feasibility of epitaxy of a GeAl thin film at a temperature range of 250-338 DEG C makes it have potential as a buffer layer when epitaxially growing some materials (such as germanium, germanium-tin and germanium-lead) that require high-temperature growth conditions. BRIEF DESCRIPTION OF DRAWINGS

[0014] Figure 1 Figure 1 is an atomic force microscope (AFM) scanning diagram of a germanium-aluminum thin film sample obtained at a growth temperature of 215 DEG C in Example 1;

[0015] Figure 2 Figure 2 is an (004) crystal face X-ray diffraction (XRD) diagram of a germanium-aluminum thin film obtained at a growth temperature of 215-338 DEG C in Example 1;

[0016] Figure 3Time-of-flight secondary ion mass spectrometry (TOF-SIMS) element distribution diagram of the germanium-aluminum thin film obtained in Example 1 at a growth temperature of 250 ℃;

[0017] Figure 4 Transmission electron microscope (TEM) cross-sectional morphology diagram and selected area electron diffraction (SAED) diagram of the germanium-aluminum thin film obtained in Example 1 at a growth temperature of 250 ℃.

[0018] Figure 5 Time-of-flight secondary ion mass spectrometry (TOF-SIMS) element distribution diagram of the germanium-indium thin film obtained in Comparative Example 1 at a growth temperature of 250 ℃. DETAILED DESCRIPTION

[0019] In order to make the technical problems to be solved by the present application, technical solutions and beneficial effects more clear, specific embodiments are described in detail below.

[0020] Example 1

[0021] The equipment used is a magnetron sputtering thin film deposition system. The germanium substrate material used has a crystal orientation of (100) and an impurity type of n-type (arsenic doped) with a resistivity of 0.01-0.05 Ω·cm.

[0022] The preparation of the germanium-based source-drain material described in this embodiment includes the following steps:

[0023] 1) The single crystal germanium substrate was sequentially ultrasonically cleaned in acetone, ethanol and deionized water for 10 min each time to remove surface organic contaminants and adsorbed particulate matter;

[0024] 2) Step 1) was repeated, and the cleaned germanium substrate was immersed in an HCl and H2O solution to remove surface metal contaminants, and then rinsed with deionized water; the repeated step 1) was repeated 3 times; the volume ratio of HCl to H2O in the HCl and H2O solution was 1:4; the immersion time was 30 s, and the rinsing was with deionized water for 15 times;

[0025] 3) Step 2) was repeated, and the treated germanium substrate was immersed in an HF and H2O solution to remove +4 valence Ge oxide, and then rinsed with deionized water; the repeated step 2) was repeated 4 times; the volume ratio of HF to H2O in the hydrofluoric acid solution was 1:20, and the immersion time was 15 s;

[0026] 4) Step 3) was repeated, and the treated germanium substrate was rinsed and dried; the repeated step 3) was repeated 4 times; the rinsing was with deionized water for 15 times; and the drying was with a drying machine;

[0027] 5) The germanium substrate treated in step 4) was placed in a magnetron sputtering system, and vacuumed to less than 5×10-4 Pa; After the pressure is reduced to 0.50 Pa, the substrate temperature is increased to 470 ℃, and then the vacuum is continuously reduced to the deposition vacuum condition. Pa;

[0028] 6) Sputtering a germanium target under the conditions of step 5) to deposit a germanium buffer layer, the sputtering pressure is 0.50 Pa, and the growth rate is 20 nm / min; the purity of the germanium target is 99.999%.

[0029] 7) The substrate temperature of the magnetron sputtering system is reduced to 215-338 ℃, and a germanium-aluminum single crystal thin film is grown by co-sputtering of germanium and aluminum at 0.50 Pa, the growth thickness is 85 nm, and the deposition vacuum condition Pa;

[0030] 8) After the deposition is completed, the vacuum is continuously reduced, the substrate temperature is reduced to room temperature, and the germanium-aluminum thin film is taken out.

[0031] Figure 1 The surface atomic force microscope (AFM) scanning diagram of the germanium-aluminum thin film sample obtained at a growth temperature of 215 ℃ in the embodiment of the present application shows that the material has no surface aluminum segregation and the surface roughness is good.

[0032] Figure 2 The (004) crystal face X-ray diffraction (XRD) of the germanium-aluminum thin film obtained at a growth temperature of 215-338 ℃ in the embodiment of the present application shows that the crystal quality of the GeAl single crystal is good.

[0033] The germanium-aluminum thin film obtained at a growth temperature of 250 ℃ in the embodiment of the present application is subjected to Hall test, the germanium-aluminum thin film has p-type doping, and the activated hole concentration is as high as 8×10 20 .

[0034] Figure 3 The time-of-flight secondary ion mass spectrometry (TOF-SIMS) element distribution diagram of the germanium-aluminum thin film obtained at a growth temperature of 250 ℃ in the embodiment of the present application shows that the diffusion length of aluminum atoms in the undoped germanium-based substrate is less than 4 nm / decade, and the aluminum atoms do not have obvious diffusion.

[0035] Figure 4 The transmission electron microscope (TEM) cross-sectional morphology diagram and selected area electron diffraction (SAED) diagram of the germanium-aluminum thin film obtained at a growth temperature of 250 ℃ in the embodiment of the present application show that the interface is flat and the crystal quality is good.

[0036] Through the above, the germanium and aluminum atoms are co-deposited under the condition that the bottom temperature is 215-338 DEG C, a germanium doped layer with high p-type activation concentration is obtained, and the aluminum atoms do not appear obvious diffusion. This makes the germanium-based source-drain material prepared by the application especially suitable for the preparation of p-type in-situ doping and p+ / n shallow junction of advanced node process of logic circuit.

[0037] Comparative Example 1

[0038] The preparation method of the present comparative example 1 is the same as that of Example 1, and a GeIn single crystal is epitaxially grown at 250 DEG C, see Figure 5 The diffusion length of indium atoms in the undoped germanium-based substrate is about 15 nm / decade, while the diffusion length of aluminum atoms in the GeAl single crystal prepared by the application in the undoped germanium-based substrate is less than 4 nm / decade, so the application can be applied to the preparation of p+ / n shallow junction in the germanium-based logic circuit.

[0039] In addition, the feasibility of epitaxial growth of the GeAl thin film of the application in the temperature range of 250-338 DEG C makes it have the potential to be used as a buffer layer when some materials (such as germanium, germanium tin, germanium lead) that need high temperature growth conditions are epitaxially grown.

Claims

1. A method of fabricating a germanium-based source-drain material, comprising: The method comprises the following steps: The germanium substrate is pretreated, then is placed into a magnetron sputtering system to be vacuumized and heated to deposit a germanium buffer layer, and finally is subjected to co-deposition of germanium and aluminum to epitaxially grow a germanium-aluminum single crystal thin film; the co-deposition of germanium and aluminum is performed at a deposition temperature of 215-338 DEG C.

2. The method of claim 1, wherein: The pretreatment of the germanium substrate comprises ultrasonic cleaning of the germanium substrate in acetone, ethanol and deionized water respectively.

3. The method of claim 1, wherein: The pretreatment of the germanium substrate comprises soaking the germanium substrate in a dilute hydrochloric acid solution and then rinsing with deionized water.

4. The method of claim 1, wherein: The pretreatment of the germanium substrate comprises soaking the germanium substrate in a dilute hydrofluoric acid solution and then rinsing with deionized water.

5. Use of a germanium-based source-drain material produced by the production method according to any one of claims 1 to 4, characterized in that: Preparation of p-type in-situ doping and p+ / n shallow junction for advanced node logic circuit, the germanium-based source-drain material is a germanium-aluminum thin film grown on a germanium-based substrate by co-deposition of germanium and aluminum, the germanium-aluminum thin film has p-type doping, the activated hole concentration is as high as 8*10 20 cm -3 -3, and the diffusion length of aluminum atoms in the germanium-based substrate is less than 4 nm / decade.

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