CN102915913B - Graphene CVD (chemical vapor deposition) direct epitaxial growth method based on sapphire substrate and device fabricated with method - Google Patents

Abstract

The invention discloses a graphene CVD (chemical vapor deposition) direct epitaxial growth method based on a sapphire substrate. Sapphire is used as the substrate, the sapphire substrate is reasonably pre-processed, and the growth pressure, the flow rate and the temperature are regulated, so that the graphene can directly grow on the sapphire without metals as the catalyst, and the grown graphene can be directly used to fabricate various devices without being transferred, so that the electrical characteristics and reliability of the device can be enhanced, and the complexity of fabrication of the device can be reduced. The large-area graphene material with semiconductor cleanliness is grown, the controllability of a single layer is more than 80%, and the area of a wafer is up to 8 inches.

Description

Graphene CVD direct epitaxial growth method and manufactured device based on sapphire substrate

technical field

The invention belongs to the field of semiconductor material manufacturing, and relates to key technologies for the preparation of semiconductor materials, in particular to a large-area graphene controllable epitaxial growth method based on a sapphire substrate, which can be used for the preparation of large-area wafer-level graphene materials without transfer .

Background technique

With the development of integrated circuits, the critical dimensions of silicon (Si)-based devices have reached theoretical and technical limits, and quantum effects have become the main limiting mechanism. Graphene material is a carbon-based two-dimensional crystal. It is the lightest and thinnest material known so far. Its single layer is only atomically thick. It has extremely excellent physical and chemical properties, such as extremely high carrier mobility (theoretical estimation More than 200,000cm ² V ^-1 s ^-1 , hundreds of times that of Si), super mechanical properties (Young's modulus about 1000GPa), extremely high specific surface area and excellent gas-sensing properties, extremely high transparency And flexibility, and there is no mismatch problem between it and the substrate, it can be fully compatible with Si-based device technology, and has outstanding industrial advantages. Therefore, the emergence of graphene has brought dawn to the industry and science and technology circles, and it is the most promising new material to replace Si as the next-generation basic semiconductor material.

Although graphene has such excellent properties, there are still many key problems to be solved urgently in the preparation of graphene. At present, the mainstream wafer-level graphene growth method in the world is based on the CVD method catalyzed by transition metals, which can be used for the preparation of large-area graphene, and is not limited by the size of the substrate, and the equipment is simple. One of the most significant disadvantages is that a metal catalytic substrate must be used, so it is difficult to cleanly transfer graphene to other dielectric substrates suitable for devices, and residues or contaminants left on graphene after the transfer process will degrade the graphene. The mobility of graphene can affect the electrical properties of graphene devices. Therefore, it is necessary to break through the limitations of existing technologies, make bold breakthroughs in technology, explore new substrates, and realize a large-area clean graphene growth method without transfer.

Sapphire is generally used as a substrate for growth of various materials, and sapphire is an insulating material with high stability at high temperatures and has a hexagonal structure. The sapphire material is used as the substrate mainly because of its low cost and large area. In addition, the sapphire substrate has a variety of surfaces, such as c-plane, a-plane, r-plane, etc., so a variety of materials with different structures can be grown, and the influence of different substrates on material properties can be studied. In summary, sapphire has far-reaching potential in semiconductor material fabrication and device fabrication.

Graphene has a hexagonal honeycomb structure with a lattice constant of 0.246nm, and wurtzite sapphire also has a hexagonal structure with a lattice constant of 0.4758nm. The lattice mismatch between the two is relatively large, about 50%. Experiments by H.J.Song et al. showed that larger lattice mismatch is beneficial to the growth of graphene, see Large scale metal-freesynthesis of graphene on sapphire and transfer-free device fabrication. Nanoscale, V4, p3050 (2012). In order to combine sapphire with graphene without graphene transfer process to obtain high-quality large-area graphene materials, it is necessary to study the direct CVD epitaxial growth of graphene on sapphire substrates.

Contents of the invention

The purpose of the present invention is to overcome the deficiencies in the existing large-area graphene growth technology, and propose a large-area high-quality graphene growth method based on a sapphire substrate without transfer, so as to improve the electrical properties of graphene and devices.

The technical key to realize the present invention is: use sapphire as the substrate, through reasonable pretreatment to the sapphire substrate, adjust the growth pressure, flow rate and temperature, directly grow graphene on the sapphire, without metal as the catalyst, the grown graphene It can be directly used to manufacture various devices without transfer process, which improves the electrical characteristics and reliability of the device and reduces the complexity of device manufacture. Its growth method realization steps include as follows:

(1) Put the sapphire substrate into acetone, ethanol and deionized water successively for cleaning, each time for 5-10 minutes, take out the substrate from the deionized water, and dry it with high-purity nitrogen (99.9999%);

(2) Put the sapphire substrate into the chemical vapor deposition CVD reaction chamber, and pump the vacuum to 10 ^-5 ~ 10 ^-6 Torr to remove the residual gas in the reaction chamber;

(3) Introduce _H2 into the reaction chamber to pretreat the substrate surface, the gas flow rate is 1-20sccm, the vacuum degree of the reaction chamber is 0.1-1Torr, the substrate temperature is 900-1000°C, and the treatment time is 5-10min;

( ₄ ) Feed Ar and CH in the reaction chamber, keep the flow ratio of Ar and CH ₁₀ :1～2:1, Ar flow 20～200sccm, CH Flow ₁ ～20sccm, air pressure maintain on 0.1～1atm , temperature 1000～1200℃, heating time 20～60min, holding time 30～60min;

(5) Naturally lower the temperature to below 100° C., keep the flows of Ar and CH ₄ in the step (5) constant, and keep the gas pressure at 0.1-1 atm to complete the growth of graphene.

After the above process, a large-area graphene material with semiconductor cleanliness can be grown, the controllability of a single layer exceeds 80%, and the maximum wafer area can reach 8 inches.

The present invention has the following advantages:

1. Due to the use of sapphire as the substrate, the grown graphene can be used in the manufacture of devices without transfer, which improves the reliability and electrical characteristics of the device.

2. Due to the use of sapphire as the substrate, the graphene growth steps and device manufacturing process steps are simplified, and the graphene manufacturing cost is reduced.

Description of drawings

Fig. 1 is the graphene growth flowchart based on sapphire substrate of the present invention;

Fig. 2 is a schematic diagram of the structure of the graphene growth process based on the sapphire substrate of the present invention.

detailed description

In order to make the purpose, technical solution and advantages of the present invention more clear, the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the present invention, not to limit the invention.

detailed description

With reference to Fig. 1, the present invention provides following embodiment:

Example 1:

The realization steps of the present invention are as follows:

Step 1, sapphire substrate preparation.

Put the sapphire substrate into acetone, ethanol and deionized water successively for cleaning, each time for 10 minutes, take out the substrate from the deionized water, and dry it with high-purity nitrogen (99.9999%).

Step 2, vacuumize the reaction chamber.

Put the sapphire substrate of semiconductor device level in the chemical vapor deposition CVD reaction chamber, and pump the vacuum to 10 ^-6 Torr to remove the residual gas in the reaction chamber.

Step 3, pretreatment of the surface of the sapphire substrate.

Introduce H ₂ into the reaction chamber to pretreat the substrate surface, the gas flow rate is 2 sccm, the vacuum degree of the reaction chamber is 0.1 Torr, the substrate temperature is 950° C., and the processing time is 5 minutes.

Step 4, graphene CVD epitaxial growth.

Introduce Ar and CH ₄ into the reaction chamber, keep the flow ratio of Ar and CH ₄ at 10:1, Ar flow rate 20 sccm, CH ₄ flow rate 2 sccm, air pressure maintained at 0.5 atm, temperature 1200°C, heating time 20 min, holding time 50 min .

Step 5, cooling process.

Naturally lower the temperature to below 100°C, keep the flow of Ar and CH in step ( ₄ ) constant, and the air pressure at 0.5 atm, to complete the growth of graphene.

Example 2:

The realization steps of the present invention are as follows:

Step A, sapphire substrate preparation.

Put the sapphire substrate into acetone, ethanol and deionized water successively for cleaning, each time for 10 minutes, take out the substrate from the deionized water, and dry it with high-purity nitrogen (99.9999%).

In step B, the reaction chamber is evacuated.

Put the sapphire substrate of semiconductor device level in the chemical vapor deposition CVD reaction chamber, and pump the vacuum to 10 ^-6 Torr to remove the residual gas in the reaction chamber.

Step C, pretreatment of the surface of the sapphire substrate.

Introduce _H2 into the reaction chamber to pretreat the substrate surface, the gas flow rate is 5 sccm, the vacuum degree of the reaction chamber is 0.2 Torr, the substrate temperature is 950 °C, and the treatment time is 10 min.

Step D, graphene CVD epitaxial growth.

Feed Ar and CH ₄ into the reaction chamber, keep the flow ratio of Ar and CH ₄ at 8:1, the flow rate of Ar is 40 sccm, the flow rate of CH ₄ is 5 sccm, the air pressure is maintained at 0.2 atm, the temperature is 1100 ° C, the heating time is 20 minutes, and the holding time is 30 minutes .

Step E, cooling process.

Naturally lower the temperature to below 100°C, keep the flows of Ar and CH ₄ in the process (D) constant, and the air pressure 0.2 Torr, to complete the growth of graphene.

Example 3:

The realization steps of the present invention are as follows:

Step 1, sapphire substrate preparation.

Put the sapphire substrate into acetone, ethanol and deionized water successively for 8 minutes each time, take out the substrate from the deionized water, and dry it with high-purity nitrogen (99.9999%).

Step 2, the reaction chamber is evacuated.

Put the sapphire substrate of semiconductor device level in the chemical vapor deposition CVD reaction chamber, and pump the vacuum to 10 ^-6 Torr to remove the residual gas in the reaction chamber.

Step 3, surface pretreatment of the sapphire substrate.

Introduce _H2 into the reaction chamber to pretreat the substrate surface, the gas flow rate is 5 sccm, the vacuum degree of the reaction chamber is 0.2 Torr, the substrate temperature is 1000 ° C, and the processing time is 8 minutes.

Step 4, graphene CVD epitaxial growth.

Feed Ar and CH ₄ into the reaction chamber, keep the flow ratio of Ar and CH ₄ at 6:1, the flow rate of Ar is 60 sccm, the flow rate of CH ₄ is 10 sccm, the air pressure is maintained at 0.2 atm, the temperature is 1000 ° C, the heating time is 20 minutes, and the holding time is 40 minutes .

Step five, cooling process.

Naturally lower the temperature to below 100°C, keep the flows of Ar and CH ₄ in step (3) constant, and the air pressure at 0.2 atm to complete the growth of graphene.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention should be included in the protection of the present invention. within range.

Claims (1)

1., based on the direct epitaxial growth method of Graphene CVD of Sapphire Substrate, it is characterized in that,

Adopt sapphire as substrate, by carrying out rational preliminary treatment to Sapphire Substrate, growth regulation pressure, flow and temperature, on sapphire face direct growth Graphene, without the need to metal as catalyst, the Graphene of growth, without the need to transfer process, just can be directly used in and manufacture various device;

Its growing method performing step comprises as follows:

(1) Sapphire Substrate is successively put into acetone, clean in ethanol and deionized water, each time 5 ~ 10min, takes out substrate, dries up with high pure nitrogen from deionized water;

(2) Sapphire Substrate is put into chemical vapor deposition reaction chamber, extracting vacuum to 10 ^-5~ 10 ^-6torr, to remove the residual gas in reative cell;

(3) in reative cell, H is passed into ₂carry out substrate surface preliminary treatment;

(4) in reative cell, Ar and CH is passed into ₄;

(5) Temperature fall is to less than 100 DEG C, keeps Ar and the CH4 flow in operation (5) constant, completes the growth of Graphene;

In described step (3), in reative cell, pass into H ₂carry out substrate surface preliminary treatment, gas flow 1 ~ 20sccm, reative cell vacuum degree 0.1 ~ 1Torr, underlayer temperature 900 ~ 1000 DEG C, processing time 5 ~ 10min;

In described step (3), in reative cell, pass into Ar and CH ₄, keep Ar and CH ₄flow-rate ratio be 10: 1 ~ 2: 1, Ar flow, 20 ~ 200sccm, CH ₄flow 1 ~ 20sccm, air pressure maintains 0.1 ~ 1atm, temperature 1000 ~ 1200 DEG C, heating-up time 20 ~ 60min, retention time 30 ~ 60min;

In described step (5), Temperature fall, to less than 100 DEG C, keeps Ar and CH in operation (5) ₄flow is constant, air pressure 0.1 ~ 1atm, completes the growth of Graphene.