Preparation method and application of germanium-based source drain material

Abstract

The invention discloses a preparation method and application of a germanium-based source-drain material, and relates to the field of germanium-based source-drain materials, a germanium-aluminum film grows on a germanium-based substrate through co-deposition of germanium and aluminum, and when the temperature of the substrate is 215-383 DEG C, X-ray diffraction (XRD) tests show that the germanium-aluminum film is of a single-crystal structure, the crystal quality is good, and the surface is free of aluminum segregation. A Hall test shows that the germanium-aluminum film has p-type doping, and the activated hole concentration is as high as 8 * 10 < 20 > # imgabs0 #. According to the characterization result of a time-of-flight-secondary ion mass spectrometer (TOF-SIMS), the diffusion length of aluminum atoms in the undoped germanium-based substrate is smaller than 4 nm / decade, and the method can be applied to p-type in-situ doping and p + / n shallow junction preparation of a germanium-based logic circuit advanced node technology.

Description

Technical Field

[0001] The present invention relates to the field of germanium-based source-drain materials, and in particular to a method for preparing a germanium-based source-drain material and an application thereof. Background Art

[0002] As the characteristic size of transistors approaches the physical limit, the performance of logic chips is increasingly unable to meet the growing demand for information processing capacity and speed, and the improvement of logic chip performance faces severe challenges. Replacing the silicon channel with germanium materials with higher mobility is expected to further improve the performance of logic chips. However, at advanced logic circuit process nodes, the contact parasitic resistance of the source and drain doping regions has become the main factor limiting the performance improvement of transistors. In addition, while traditional doping methods achieve high activation doping concentrations, they are often accompanied by long-distance diffusion of impurity atoms in the substrate, which makes it difficult to accurately control the doped area, especially at the nanoscale. For example, in some existing doping technologies, the diffusion length of doped atoms in undoped germanium-based substrates may reach tens of nanometers or even longer, which not only increases the transition area between the doped and undoped regions, but may also have an adverse effect on the performance of adjacent electronic devices.

[0003] In order to be compatible with silicon processes, it is required to obtain a high activation doping concentration of germanium at ≤400°C. Traditional ion implantation and in-situ doping methods usually require a high-temperature treatment process to repair the lattice and / or activate and diffuse the dopant, which is incompatible with SiCMOS processes 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 high. Therefore, developing a method to achieve high activation concentration doping while effectively controlling the diffusion length of doped atoms is of great significance for improving the performance of logic circuits. Summary of the invention

[0004] The purpose of the present invention is to solve the above problems in the prior art and provide a method for preparing a germanium-based source and drain material and its application, so as to realize high-quality, high-p-type in-situ aluminum-doped germanium material under the condition of 215-338°C, wherein the aluminum component can be greater than 3%, and the hole concentration activated by the Hall test can reach up to 8×10 20 The diffusion length is less than 4nm / decade, which can be applied to p-type in-situ doping and the preparation of p+ / n shallow junctions in advanced node processes of logic circuits.

[0005] In order to achieve the above object, the present invention adopts the following technical scheme:

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

[0007] The method for preparing the germanium-based source and drain material comprises the following steps: firstly, pretreating the germanium-based substrate, then placing the germanium-based substrate in a magnetron sputtering system to evacuate the system, and heating the system to deposit a germanium-based buffer layer, and finally epitaxy the germanium-aluminum single crystal film by co-deposition of germanium and aluminum.

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

[0009] The germanium-based substrate pretreatment includes soaking the germanium-based substrate in a diluted hydrochloric acid solution and then rinsing it with deionized water.

[0010] The germanium-based substrate pretreatment includes soaking the germanium-based substrate in a diluted hydrofluoric acid solution and then rinsing it with deionized water.

[0011] The co-deposition of germanium and aluminum has a deposition temperature of 215-338°C.

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

[0013] The present invention epitaxies high-crystal-quality germanium-aluminum thin films on germanium-based substrates (including germanium, silicon-based germanium, germanium-tin, germanium-lead, etc.) by optimizing growth parameters. Under the condition of substrate temperature of 215-338°C, germanium and aluminum atoms are co-deposited to obtain a germanium doped layer with high p-type activation concentration (the Hall test doping concentration is up to 8×10 20 ), and the aluminum atoms do not diffuse significantly, and the diffusion length is less than 4nm / decade, so that the doping area can be precisely controlled within the nanometer scale, avoiding the adverse effects of long-distance diffusion, which makes the present invention particularly suitable for the preparation of p-type in-situ doping and p+ / n shallow junctions in advanced node processes of logic circuits. Moreover, the feasibility of epitaxy of GeAl thin films in the temperature range of 250-338℃ makes it potentially useful as a buffer layer for epitaxy of some materials that require high-temperature growth conditions (such as germanium, germanium-tin, and germanium-lead). BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is a surface atomic force microscope (AFM) scan of the germanium aluminum thin film sample obtained at a growth temperature of 215° C. in Example 1;

[0015] Figure 2 is the (004) crystal plane X-ray diffraction (XRD) pattern of the germanium aluminum thin film obtained at a growth temperature of 215-338° C. in Example 1;

[0016] Figure 3This is the time-resolved secondary ion mass spectrometry (TOF-SIMS) element distribution diagram of the germanium aluminum film obtained at a growth temperature of 250° C. in Example 1;

[0017] Figure 4 The transmission electron microscope (TEM) cross-sectional morphology image and the selected area electron diffraction (SAED) image of the germanium aluminum thin film obtained at a growth temperature of 250° C. in Example 1;

[0018] Figure 5 This is the time-resolved 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°C. DETAILED DESCRIPTION

[0019] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention clearer and more understandable, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments.

[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), an impurity type of n-type (arsenic doped), and a resistivity of 0.01~0.05Ω·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 ultrasonically cleaned in acetone, ethanol and deionized water for 10 minutes respectively to remove surface organic pollutants and adsorbed particles;

[0024] 2) Repeat step 1), soak the cleaned germanium substrate in HCl and H2O solution to remove surface metal contaminants, and then rinse with deionized water; the step 1) is repeated 3 times; the volume ratio of HCl to H2O in the HCl and H2O solution is 1:4; the soaking time is 30s, and the rinsing is rinsed with deionized water 15 times;

[0025] 3) Repeat step 2), immerse the treated germanium substrate in a HF and H2O solution to remove +4-valent Ge oxide, and then rinse with deionized water; the step 2) is repeated 4 times; the volume ratio of HF to H2O in the hydrofluoric acid solution is 1:20, and the immersion time is 15s;

[0026] 4) Repeat step 3) to rinse the treated germanium substrate and spin dry; the step 3) is repeated 4 times; the rinsing is rinsed with deionized water 15 times; the spin drying is spin drying with a spin dryer;

[0027] 5) Place the germanium substrate processed in step 4) into the magnetron sputtering system and evacuate the system to a vacuum of less than Pa, and then continue to evacuate to the deposition vacuum condition; the substrate temperature is 470°C; the deposition vacuum condition is Pa;

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

[0029] 7) The substrate temperature of the magnetron sputtering system was lowered to 215~338℃, and the co-sputtering of germanium and aluminum was performed at 0.50Pa to grow germanium-aluminum single crystal thin films with a growth thickness of 85nm. The deposition vacuum conditions were Pa;

[0030] 8) After the deposition is completed, continue to evacuate the substrate; lower the substrate temperature to room temperature and remove the germanium aluminum film.

[0031] Figure 1 This is a surface atomic force microscope (AFM) scan of a germanium aluminum thin film sample obtained at a growth temperature of 215° C. in an embodiment of the present invention, indicating that the material has no surface aluminum segregation and has good surface roughness.

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

[0033] The Al-Ge thin film obtained at a growth temperature of 250°C in the embodiment of the present invention has a p-type doping structure and an activated hole concentration of up to 8×10 20 .

[0034] Figure 3 This is a time-resolved secondary ion mass spectrometry (TOF-SIMS) element distribution diagram of the germanium-aluminum thin film obtained at a growth temperature of 250° C. in an embodiment of the present invention. It can be seen that the diffusion length of aluminum atoms in the undoped germanium-based substrate is less than 4 nm / decade, and there is no obvious diffusion of aluminum atoms.

[0035] Figure 4 The transmission electron microscope (TEM) cross-sectional morphology and selected area electron diffraction (SAED) diagram of the germanium aluminum thin film obtained at a growth temperature of 250° C. according to an embodiment of the present invention show that a flat interface and good crystal quality are observed.

[0036] Through the above, the present invention co-deposit germanium and aluminum atoms at a bottom temperature of 215-338°C to obtain a germanium doped layer with a high p-type activation concentration, and the aluminum atoms do not diffuse significantly. This makes the germanium-based source and drain material prepared by the present invention particularly suitable for p-type in-situ doping and preparation of p+ / n shallow junctions in advanced node processes of logic circuits.

[0037] Comparative Example 1

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

[0039] In addition, the feasibility of epitaxy of the GeAl film in the temperature range of 250-338°C makes it potentially useful as a buffer layer for epitaxy of some materials that require high temperature growth conditions (such as germanium, germanium-tin, and germanium-lead).

Claims

1. An application of a germanium-based source-drain material, characterized in that: It is used for the preparation of p-type in-situ doping and p+ / n shallow junction of advanced node technology of logic circuit. The germanium-based source and drain material is a germanium-aluminum film grown by co-deposition of germanium and aluminum on a germanium-based substrate. The germanium-aluminum film has its own p-type doping, and the activated hole concentration is as high as 8×10 20 , the diffusion length of aluminum atoms in germanium-based substrates is less than 4nm / decade.

2. The method for preparing the germanium-based source-drain material according to claim 1, characterized in that: The method comprises the following steps: firstly, pre-treating the germanium-based substrate, then placing the germanium-based substrate in a magnetron sputtering system to evacuate the substrate, and heating the substrate to deposit a germanium-based buffer layer, and finally epitaxying a germanium-aluminum single crystal film by co-deposition of germanium and aluminum.

3. The method for preparing a germanium-based source-drain material according to claim 2, characterized in that: The co-deposition of germanium and aluminum has a deposition temperature of 215-338°C.

4. The method for preparing a germanium-based source-drain material according to claim 2, characterized in that: The germanium-based substrate pretreatment comprises ultrasonically cleaning the germanium-based substrate in acetone, ethanol and deionized water respectively.

5. The method for preparing a germanium-based source-drain material according to claim 2, characterized in that: The germanium-based substrate pretreatment includes soaking the germanium-based substrate in a diluted hydrochloric acid solution and then rinsing it with deionized water.

6. The method for preparing a germanium-based source-drain material according to claim 2, characterized in that: The germanium-based substrate pretreatment includes soaking the germanium-based substrate in a diluted hydrofluoric acid solution and then rinsing it with deionized water.

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