CN112501590B

CN112501590B - MOCVD (metal organic chemical vapor deposition) equipment

Info

Publication number: CN112501590B
Application number: CN202011236149.1A
Authority: CN
Inventors: 钟蓉; 王杨波; 甄龙云; 熊诵明; 黄文献
Original assignee: Wenzhou University
Current assignee: Wenzhou University
Priority date: 2020-11-09
Filing date: 2020-11-09
Publication date: 2022-03-18
Anticipated expiration: 2040-11-09
Also published as: WO2022095123A1; CN112501590A

Abstract

The invention relates to MOCVD equipment which has a better airflow transverse track and can ensure the process temperature consistency of each position of a deposition area. The technical scheme adopted comprises the following steps: radial cross-section all is circular shape top cap, top cap panel, base and susceptor, its characterized in that: the upper surface embedding of top cap panel top cap bottom, lower surface are middle thin both sides thick curved surface, the vertical direction at top cap center sets up gas pipeline, just gas pipeline's lower extreme extends to the base center, the gas pipeline lateral wall is equipped with the venthole of a plurality of layers of circumference range. The advantages are that: through the design of a novel top cover panel, the stress at the edge and the center is more uniform, and the growth speed of the film is closer, so that the uniformity problem of the film is improved.

Description

MOCVD (metal organic chemical vapor deposition) equipment

Technical Field

The invention belongs to the technical field of semiconductor thin film materials, and particularly relates to MOCVD equipment.

Background

Metal Organic Chemical Vapor deposition (mocvd), also known as movpe (metal Organic Vapor Phase epitaxy), is an important technique for semiconductor epitaxial growth.

The working process of the MOCVD equipment is roughly as follows: the saturated vapor pressure is related to the temperature, and the organic source has a fixed saturated vapor pressure due to the constant temperature of the organic source, so that the flow of the carrier gas can be controlled through a flowmeter, and the quantity of the organic source carried by the carrier gas when the carrier gas flows through the organic source is controlled; the multi-channel carrier gas carries different organic sources to be transported to the air inlet of the reaction chamber to be mixed, then the mixture is transported to the vicinity of the Wafer (substrate) surface to carry out chemical reaction under the action of high temperature and is deposited on the Wafer, thereby finishing the epitaxial growth of the film.

In most MOCVD equipment, the Ceiling is a quartz piece whose main component is SiO₂. This feature mainly serves to protect the top cap from erosion and to ensure a lateral trajectory of the gas flow, thereby ensuring that the process temperature in the deposition area is consistent. In the structure of the traditional MOCVD equipment, as described in the Chinese patent of patent publication No. CN 102766851B, Ceiling is a single-layer or multi-layer planar structure,a channel for the reaction gas to pass through is arranged between the top cover (furnace cover) and the Ceiling. However, in the using process, the microstructure of the edge part and the microstructure of the central part of the epitaxial film prepared by the traditional MOCVD equipment are not consistent: the central portion of the epitaxial thin film was crack-free, while the edge portion was very cracked. The reason for this phenomenon is that on one hand, the flow speeds of the gases at various positions are different, which causes different heat carried away by the gases, so that the reaction temperatures of the gases at different positions are different, and the growth speeds of the films at different positions are also different; on the other hand, the gas molecules on the Wafer surface are scoured and impacted, which are changed along with different positions, so that the gas pressure on the microscopic surface is inconsistent, and the crack distribution is not uniform.

This patent relies on 2016 national key research and development project-international scientific and technological innovation cooperation key special item between government of the department of science and technology (middle and American): the project of 'control strategy and method research for improving the uniformity of nano-component film' is supported, and the project number is as follows: 2016YFE 0105900.

Disclosure of Invention

The invention aims to provide MOCVD equipment which has a better airflow transverse track and can ensure the process temperature consistency at each position of a deposition area.

In order to solve the above problems, the technical scheme adopted by the invention comprises: radial cross-section all is circular shape top cap, top cap panel, base and susceptor, its characterized in that: the upper surface embedding of top cap panel top cap bottom, lower surface are middle thin both sides thick curved surface, the vertical direction at top cap center sets up gas pipeline, just gas pipeline's lower extreme extends to the base center, the gas pipeline lateral wall is equipped with the venthole of a plurality of layers of circumference range.

The MOCVD equipment is characterized in that: the height H of the curved surface is 1-10 mm.

The MOCVD equipment is characterized in that: the height H of the curved surface is 2 mm.

The MOCVD equipment is characterized in that: the susceptor is arranged at the bottom of the reaction cavity of the base in a circumferential arrangement mode, and the tangent circle of the susceptor is concentric with the curved surface.

The MOCVD equipment is characterized in that: the radius R1 of the maximum opening part circle of the curved surface is slightly larger than the diameter R2 of the circumcircle of the susceptor.

The MOCVD equipment is characterized in that: the R1 is 1-10mm larger than the R2.

The MOCVD equipment is characterized in that: the R1 is 2mm larger than R2.

The MOCVD equipment is characterized in that: at least one layer of circumferentially arranged gas outlet holes are arranged on the gas pipeline and positioned in the curved surface.

The MOCVD equipment is characterized in that: and three layers of air outlet holes which are arranged circumferentially are arranged on the gas pipeline.

The MOCVD equipment is characterized in that: the air outlet holes of each layer are distributed on the side wall of the gas pipeline at equal intervals.

The MOCVD equipment has the advantages that: 1. through the novel design of the top cover panel, the stress on the edge and the center is more uniform, and the growth speed of the film is closer, so that the uniformity problem of the film is improved; 2. through the design of a novel top cover panel, the variation range of the flow of reaction gas in a deposition area can be reduced in MOCVD equipment, and the variation range of the deposition which tends to be scoured and impacted by the gas is reduced.

The invention is further described below with reference to the accompanying drawings.

Drawings

FIG. 1 is a cross-sectional view of an MOCVD apparatus of the present invention;

FIG. 2 is an exploded view of the MOCVD apparatus of the present invention;

FIG. 3 is a schematic structural view of the roof panel of the present invention;

FIG. 4 is a schematic diagram of a base reaction chamber according to the present invention;

FIG. 5 is an intensity contrast diagram of an XRD rocking curve for the GaN (002) plane;

FIG. 6 is a comparative optical micrograph of a GaN thin film.

Detailed Description

Referring to fig. 1 to 6, the MOCVD equipment of the present invention includes a top cover 1, a top cover panel 2, a base 3, and a susceptor 4, each of which has a circular radial cross section. The top cover panel 2 is embedded into the bottom of the top cover 1, and the lower surface of the top cover panel 2 is a curved surface 5 with a thin middle and two thick sides. The height H of the curved surface 5 is 1-10mm, ideally 2 mm. By the design of the curved surface 5, the purpose is to make the frequency of the reaction gas striking the Wafer surface at each position uniform, so that the gas pressure and the reaction speed at the edge position of the deposition area are made uniform with the center position. Specifically, as shown in fig. 1, the reaction gas enters the reaction chamber from the gas inlet, and flows transversely toward the Wafer position under the control of Ceiling as indicated by the arrow, and the gas continuously reacts and is deposited during the flowing process. Therefore, the farther from the gas inlet, the lower the density of the reaction gas, and the slower the deposition rate of the thin film. The vertical direction at top cap 1 center sets up gas pipeline 6, just the lower extreme of gas pipeline 6 extends to the base 3 center, and reaction gas sweeps away through gas pipeline from the leading-in of top cap.

Preferably, the susceptors 4 are arranged at the bottom of the reaction chamber 9 of the base 3 in a circumferential arrangement manner, a gap is reserved between adjacent susceptors 4, and the circumscribed circle 10 of each susceptor is arranged concentrically with the curved surface 5. The radius R1 of the maximum opening part circle 8 of the curved surface 5 is slightly larger (in the range of 1-10mm, most preferably 2 mm) than the diameter R2 of the circumscribed circle 10 of the susceptor 4. So that the gas pressure and reaction speed at the edge position of the deposition area are more consistent with those at the center position.

Preferably, the gas pipeline 6 is provided with three layers of circumferentially arranged gas outlet holes 7, and the gas outlet holes 7 of each layer are equidistantly distributed on the side wall of the gas pipeline 6. The gas pipeline 6 is provided with a layer of circumferentially arranged gas outlet holes 7 which are positioned in the curved surface 5. The reaction gas can be more uniformly blown out, so that the gas pressure and the reaction speed at the edge position of the deposition area are more consistent with those at the center position.

Preferably, the upper end of the gas pipeline 6 is provided with a mounting flange 11, and the center of the top cover panel 2 is provided with a center mounting hole 12 matched with the mounting flange 11. To facilitate the installation of the gas duct 6 and the roof panel 2.

The beneficial effects of the present invention are further demonstrated by the following experimental examples:

taking a Si substrate epitaxial growth GaN film as an example, after the epitaxial growth film is carried out by using the top cover panel (cetiling), the observation of an optical microscope shows that no obvious crack exists at the center position and the edge position of the film; the specific lattice orientations at the center position and the edge position of the thin film were measured by XRD (X-ray diffractometer), and the half-peak widths thereof were also found to be substantially constant, indicating that the film qualities at the center position and the edge position of the thin film were relatively close.

The following explanation will be made in detail by using different shapes of Ceiling to perform epitaxial growth comparison experiments.

In the epitaxial growth using the conventional Ceiling, the deposition rate of the film is determined by the movement distance of the reaction gas in the apparatus, i.e., the distance from the gas inlet to the deposition point, thereby resulting in that the deposition rate of the epitaxial film at the Wafer edge position is smaller than that at the Wafer center position, and also resulting in that the temperature at the Wafer edge position is lower than that at the Wafer center position. As shown in the XRD results of the epitaxial film in fig. 5 (a), the grain quality at the center of the film was higher than that at the edge thereof (XRD peak at the center of GaN film was about 48% higher than XRD peak at the edge, and FWHM (full width at half maximum) value (754 arcsec) at the center was much lower than FWHM value (1133 arcsec) at the edge, indicating that the grain quality at the center was higher, i.e., the uniformity of the film was lower). As shown in the results of optical microscopy in fig. 6(a) and (b), cracks were not found at the center of the GaN film but a large number of minute holes were present, while cracks were present at the edge positions.

In the epitaxial growth using the Ceiling of the present invention, the deposition rate of the thin film is determined by both the moving distance of the reaction gas in the apparatus and the deposition distance of the reaction gas (decreasing the height of the reaction chamber can decrease the deposition distance of the gas). When the moving distance of the reaction gas is increased, the deposition rate of the thin film is reduced. However, as the moving distance of the reaction gas increases, the height of the reaction chamber is reduced by the surface shape of the novel Ceiling, so that the deposition distance of the reaction gas is reduced, that is, the deposition distance of the gas is the largest at the position closest to the gas inlet, the deposition rate of the thin film is the smallest at the moment, and the deposition rate of the thin film is the largest at the position farthest from the gas inlet at the moment, the deposition distance of the gas is the smallest at the moment. Therefore, when these two factors are combined together, the deposition rates of the respective positions of the thin film tend to be uniform in the end. When the deposition rates at the respective locations are uniform, the heat removed by the reaction gas impinging on the Wafer surface may be uniform, and as a result, the surface temperature and the surface pressure at the respective locations also tend to be uniform.

When we further used the preferred embodiment (i.e., the embodiment defined in paragraphs 2 to 3) we obtained that the grain quality at the center of the film did not differ much from the grain quality at the edge as shown in the XRD results of the epitaxial film in fig. 5(b) (XRD peak at the center of the GaN film was about 22% higher than XRD peak at the edge, and FWHM value 731 at the center (fwarcsec) was very close to FWHM value 798 arcsec at the edge, i.e., the grain quality was relatively consistent, indicating that the uniformity of the film was high at this time). As shown in fig. 6(c) and (d) which are the results of optical microscopy, no cracks were observed at the center of the GaN film and fewer holes were observed, while no cracks were observed at the edge of the GaN film and a large number of minute holes were observed, indicating that the film had high uniformity and good film quality.

In conclusion, the use of the Ceiling of the present invention in MOCVD equipment can improve the uniformity and film quality of GaN epitaxial films.

Although the present invention has been described with reference to the above embodiments, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention.

Claims

1. The utility model provides a MOCVD equipment, includes that radial cross section all is circular shape top cap (1), top cap panel (2), base (3) and susceptor (4), its characterized in that: the upper surface embedding of top cap panel (2) top cap (1) bottom, lower surface are middle thin both sides thick curved surface (5), the vertical direction at top cap (1) center sets up a gas pipeline (6), just the lower extreme of gas pipeline (6) extends to base (3) center, gas pipeline (6) lateral wall is equipped with venthole (7) that a plurality of layers of circumference were arranged, the height H of curved surface (5) is 1-10mm, set up with the mode that the circumference was arranged in susceptor (4) reaction chamber (9) bottom of base (3) and its circumcision (10) with curved surface (5) set up with one heart, it is located to have venthole (7) that the one deck circumference was arranged on gas pipeline (6) at least in curved surface (5).

2. The MOCVD equipment according to claim 1, characterized in that: the height H of the curved surface (5) is 2 mm.

3. The MOCVD equipment according to claim 2, characterized in that: the radius R1 of the maximum opening part circle (8) of the curved surface (5) is larger than the diameter R2 of the circumscribed circle (10) of the susceptor (4).

4. The MOCVD equipment according to claim 3, wherein: the R1 is 1-10mm larger than the R2.

5. The MOCVD equipment according to claim 4, wherein: the R1 is 2mm larger than R2.

6. The MOCVD equipment according to claim 1, characterized in that: and three layers of air outlet holes (7) which are arranged circumferentially are arranged on the gas pipeline (6).

7. The MOCVD equipment according to claim 1, characterized in that: the air outlet holes (7) of each layer are distributed on the side wall of the gas pipeline (6) at equal intervals.