CN110797245B

CN110797245B - Semiconductor processing equipment

Info

Publication number: CN110797245B
Application number: CN201911032893.7A
Authority: CN
Inventors: 李兴存; 张受业
Original assignee: Beijing Naura Microelectronics Equipment Co Ltd
Current assignee: Beijing Naura Microelectronics Equipment Co Ltd
Priority date: 2019-10-28
Filing date: 2019-10-28
Publication date: 2022-11-25
Anticipated expiration: 2039-10-28
Also published as: TW202123782A; CN110797245A; TWI763084B

Abstract

The present invention relates to a semiconductor processing apparatus. In one embodiment of the present invention, the semiconductor processing apparatus includes a reaction chamber having a susceptor disposed therein for supporting a workpiece to be processed; the first plasma generating cavity is communicated with the reaction cavity and used for providing ion beams to the workpiece to be processed along a first direction; the second plasma generating cavity is communicated with the reaction cavity, and the distance from the outlet of the second plasma generating cavity to the base is greater than the preset distance so as to provide free radicals to the workpiece to be processed along the second direction; wherein, the first direction and the second direction form a certain angle.

Description

Semiconductor processing equipment

Technical Field

The present invention relates generally to the field of semiconductors, and more particularly to semiconductor processing equipment.

Background

Third-generation semiconductor materials typified by silicon carbide (SiC) are rapidly rising. By virtue of the excellent characteristics of the SiC material, the SiC material can be applied to occasions in which traditional materials such as Si, gaAs and InP are insufficient, and breakthrough is brought to the performance of devices. In a widely used SiC etching process, it is necessary to increase the plasma density to obtain a high etching rate.

However, the high-density plasma has heating effect on the SiC material, and the heat source of the high-density plasma comes from three aspects: the ion bombardment heating, the chemical reaction heat and the radiant heat. The above-mentioned heating action of the high-density plasma disadvantageously causes a rapid increase in the temperature of the wafer surface, destruction of the bonded structure, and finally termination of the production process. Thus, the prior art has a pair of contradictory relationships between plasma density and temperature, making it difficult to balance high etch rates with low wafer temperatures.

Disclosure of Invention

The invention discloses a semiconductor processing device to solve the problems in the background art, to simultaneously realize high etching rate and low wafer temperature, and to realize flexible control of the etching process.

According to an embodiment of the present invention, a semiconductor processing apparatus is disclosed, the semiconductor processing apparatus comprising a reaction chamber having a susceptor disposed therein for carrying a workpiece to be processed; the first medium cylinder is communicated with the reaction chamber and used for providing ion beams to the workpiece to be processed along a first direction; the second medium cylinder is communicated with the reaction chamber, and the distance from the outlet of the second plasma generation cavity to the base is greater than a preset distance so as to provide free radicals to the workpiece to be processed along a second direction; wherein the first direction is at an angle to the second direction.

The invention adopts two independent plasma sources to respectively generate ions and free radicals required by the etching of the workpiece to be processed, can enable the ion density and the free radical density to be independently controllable, and breaks through the limitation caused by the etching rate of the workpiece to be processed, particularly the SiC semiconductor wafer, due to the proportional solidification of the ion density and the free radical density in a single plasma generating source. In addition, because the plasma source for generating ions is not in direct contact with the wafer and the plasma source for generating free radicals is a remote plasma source, the plasma radiation heating effect of the two independent plasma sources is obviously reduced, and the surface temperature of the wafer is effectively reduced.

Drawings

FIG. 1 is a schematic diagram of a semiconductor processing apparatus according to an embodiment of the present invention.

Fig. 2 is a top view of a first media cartridge and a filter grid according to an embodiment of the invention.

Fig. 3 is a side view of a filter grid according to an embodiment of the present invention.

FIG. 4 is a cross-sectional view of an outlet of a second media cartridge according to one embodiment of the invention.

Detailed Description

The following disclosure provides various embodiments or illustrations that can be used to implement various features of the disclosure. The specific embodiments of components and arrangements described below are provided to simplify the present disclosure. It is to be understood that such descriptions are merely illustrative and are not intended to limit the present disclosure. For example, in the description that follows, forming a first feature on or over a second feature may include certain embodiments in which the first and second features are in direct contact with each other; and may also include embodiments in which additional elements are formed between the first and second features described above, such that the first and second features may not be in direct contact. In addition, the present disclosure may repeat reference numerals and/or characters in various embodiments. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed.

Moreover, spatially relative terms, such as "under," "below," "over," "above," and the like, may be used herein to facilitate describing a relationship between one element or feature relative to another element or feature as illustrated in the figures. These spatially relative terms are intended to encompass a variety of different orientations of the device in use or operation in addition to the orientation depicted in the figures. The device may be otherwise oriented (e.g., rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.

Although numerical ranges and parameters setting forth the broad scope of the application are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. Any numerical value, however, inherently contains certain standard deviations found in their respective testing measurements. As used herein, "about" generally refers to actual values within plus or minus 10%, 5%, 1%, or 0.5% of a particular value or range. Alternatively, the term "about" means that the actual value falls within the acceptable standard error of the mean, subject to consideration by those of ordinary skill in the art to which this application pertains. It is understood that all ranges, amounts, values and percentages used herein (e.g., to describe amounts of materials, length of time, temperature, operating conditions, quantitative ratios, and the like) are modified by the term "about" in addition to the experimental examples or unless otherwise expressly stated. Accordingly, unless indicated to the contrary, the numerical parameters set forth in the specification and attached claims are approximations that may vary depending upon the desired properties sought to be obtained. At the very least, these numerical parameters are to be understood as meaning the number of significant digits recited and the number resulting from applying ordinary carry notation. Herein, numerical ranges are expressed from one end to the other or between the two ends; unless otherwise indicated, all numerical ranges set forth herein are inclusive of the endpoints.

Fig. 1 shows an apparatus (10) according to an embodiment of the invention. The apparatus (10) may include a reaction chamber (100), a first plasma generation chamber (601), and a second plasma generation chamber (602). The first plasma generation chamber (601) is arranged in communication with the reaction chamber (100) for providing an ion beam to a workpiece to be processed in a first direction. The second plasma generation cavity (602) is communicated with the reaction chamber (100). In one embodiment, the reaction chamber (100) may be further configured as a vacuum reaction chamber. The lower portion of the reaction chamber 100 may include a pedestal 503 to carry and/or hold a workpiece to be processed, which may be, but is not limited to, a semiconductor wafer. An outlet is arranged on one side of the second plasma generation cavity (602) adjacent to the reaction chamber (100). The second plasma generation chamber (602) is communicated with the reaction chamber (100) through the outlet so as to provide free radicals to the workpiece to be processed along a second direction. The outlet may be spaced from the base by a distance greater than a predetermined distance such that the lifetime-limited ions and electrons decay to a concentration much lower than the free radical concentration over a long path of the predetermined distance, such that predominantly neutral gases and reactive free radicals reach the surface of the workpiece to be processed. Preferably, the preset distance may be greater than 200mm. The invention adopts two independent plasma sources of the first plasma generating cavity (601) and the second plasma generating cavity (602) to respectively generate ions and free radicals required by the etching of a workpiece to be processed, can enable the ion density and the free radical density to be independently controllable, and breaks through the limitation caused by the etching rate of the workpiece to be processed, particularly a SiC semiconductor wafer, due to the proportional solidification of the ion density and the free radical density in a single plasma generating source. In addition, because the plasma source for generating ions in the first plasma generating cavity (601) is not in direct contact with the wafer, and the plasma source for generating free radicals in the second plasma generating cavity (602) is a remote plasma source, the plasma radiation heating effect of the two independent plasma sources is obviously reduced, and the surface temperature of the workpiece to be processed is effectively reduced.

In one embodiment, the base (503) may be a mechanical chuck and mechanically carries and/or holds the workpiece to be machined. In another embodiment, the base (503) may be an ElectroStatic Chuck (ESC) for carrying and/or holding the workpiece to be processed by ElectroStatic attraction. The pedestal (503) may be coupled to a bias power supply (505) via a matcher (504) to attract the ion beam to accelerate in a first direction toward the workpiece to be processed. Preferably, the bias power supply (505) is an RF bias power supply (505) that generates RF power at a frequency that may range from 0.4MHz to 13.56MHz.

Above the reaction chamber (100), the first plasma generation chamber (601) may include a first media cartridge (104) and a first induction coil (103) disposed around the first media cartridge (104). A first media cartridge (104) contains a first reactant gas. The first inductive coil (103) is coupled to a first radio frequency power supply (101). Preferably, the first induction coil (103) is coupleable to a first radio frequency power supply (101) via a first matching circuit (102). The power source frequency of the first radio frequency power source (101) can be configured to be 0.4MHz-60MHz. In one embodiment, the first dielectric cylinder (104) may be made of quartz or ceramic. The first reactive gas may be an inert gas such as, but not limited to, argon (Ar). Preferably, a first gas delivery module (401) may be further provided to provide a first reactant gas into the first media cartridge (104).

When the first rf power supply (101) is turned on, the first induction coil (103) is energized to generate an electromagnetic field that may be coupled to the first reactant gas through the first dielectric cartridge (104) to generate a first plasma comprising ions and electrons. The ionized first reaction gas can enter the reaction chamber (100) through the outlet of the first medium cylinder (104) and the opening at the upper part of the reaction chamber (100) under the action of external force such as gravity and move towards the workpiece to be processed along a first direction parallel to the axial direction of the first medium cylinder (104). However, the axial direction of the first media cartridge (104) may not be parallel to the first direction. The first direction may or may not be perpendicular to the surface of the workpiece to be machined. Preferably, when the first direction is perpendicular to the surface of the workpiece to be processed, the distribution of the first reaction gas on the surface of the workpiece to be processed may be improved in alignment and uniformity.

The first plasma generation chamber (601) may include a filter grid (302). In one embodiment, the filter grid (302) is disposed below the first media cartridge (104). The direct current bias power supply (301) provides a positive bias to the filter grid (302), so that the ion beam in the ionized first reaction gas is stripped from the plasma sheath and passes through the filter grid (302) to be accelerated towards the workpiece to be processed along a first direction, and the electrons in the ionized first reaction gas are restrained by the filter grid (302) from passing through the filter grid (302).

Preferably, the filter grid (302) can comprise a grid electrode with grid holes and can be made of molybdenum metal and other materials, the pore diameter of the grid holes can be configured to be 0.5-2mm, and the direct current positive bias voltage can be configured to be 25-100V. When the plasma sheath thickness is typically 1mm, it is beneficial to configure the aperture of the gate holes of the filter grid (302) to be less than 2mm, since when the aperture of the gate holes is less than this value, it is further ensured that only ions can pass through the filter grid (302).

Fig. 2 shows a top view of the first media cartridge (104) and the filter grid (302), wherein the first media cartridge (104) is cylindrical in cross-section and its inner diameter can be configured to be no smaller than the diameter of the base (503). In one embodiment, the distance between the base (503) and the filter grid (302) may be 10-100mm.

Fig. 3 shows a structural side view of the filter grid (302), wherein the thickness H1 of the filter grid (302) may be 0.5-5mm, the radius R of the grid holes may be 0.25-1mm, and the material may be a metal material with high melting point and corrosion resistance such as molybdenum.

Referring to fig. 1, at one side of the reaction chamber (100), a second plasma generation chamber (602) is provided. The second plasma generation chamber (602) may include a second dielectric cartridge (204) and a second induction coil (203) disposed around the second dielectric cartridge (204). A second media cartridge (204) contains a second reactant gas. The second inductive coil (203) is coupled to a second radio frequency power supply (201). Preferably, the second inductive coil (203) is coupleable to a second radio frequency power supply (201) via a second matching circuit (202). The power source frequency of the second radio frequency power supply (201) can be configured to be 0.4MHz-60MHz. When the second RF power supply (201) is turned on, the second induction coil (203) is excited to generate an electromagnetic field, which can be coupled to a second reactant gas through a second dielectric cylinder (204) to generate a gas mixture containing ions, electrons, neutral gases, and oxygenA second plasma of radicals, which may include, for example, reactive fluorine (F) radicals. In one embodiment, the second dielectric cylinder (204) may be made of quartz or ceramic. The second reactant gas may be an inert gas containing free radicals, such as, but not limited to, sulfur hexafluoride (SF) ₆ ). Preferably, a second gas transport module (402) may be further provided to provide a second reactant gas into the second media cartridge (204). A second induction coil (203) is provided outside the second medium cylinder (204).

Still referring to fig. 1, at the other side of the reaction chamber (100), a vacuum system (701) is provided, which vacuum system (701) draws vacuum or exhaust gas from the reaction chamber (100) from the other side, so that the ionized second reaction gas enters the reaction chamber (100) via the outlet of the second medium cylinder (204) and the opening at one side of the reaction chamber (100) and moves toward the workpiece to be processed along a second direction parallel to the axial direction of the second medium cylinder (204). However, the axial direction of the second media cartridge (204) may not be parallel to the second direction. The second direction may or may not be parallel to the surface of the workpiece to be machined. Preferably, when the second direction is parallel to the surface of the workpiece to be processed, the radial velocity of the movement of the radicals on the surface of the workpiece to be processed can be increased.

In a preferred embodiment, the first plasma generation cavity is disposed above the reaction chamber, and the second plasma generation cavity is disposed at a side of the reaction chamber. At the moment, the first direction is perpendicular to the surface of the workpiece to be processed, the second direction is parallel to the surface of the workpiece to be processed, and an included angle of 90 degrees is formed between the first direction and the second direction.

In another embodiment, the first plasma generation chamber may not be located above the reaction chamber, and the first direction is not perpendicular to the surface of the workpiece to be processed; similarly, the second plasma generation cavity may not be located at the side of the reaction chamber, and the second direction is not parallel to the surface of the workpiece to be processed. Therefore, the first direction and the second direction may not form an angle of 90 °, but form an angle.

In one embodiment, a vacuum system (701) is in communication with the reaction chamber and is disposed opposite the second media cartridge (204) to accelerate the radicals toward the workpiece to be processed. In another embodiment, the vacuum system (701) is not disposed opposite the second media cartridge (204), but is disposed at an angle.

In one embodiment, the distance between the outlet of the second dielectric cylinder (204) and the workpiece to be processed may be configured such that the ionized second reactive gas reaches the surface of the workpiece to be processed with only neutral gas and radicals therein, and ions and electrons therein have a relatively short lifetime, and after passing through the long distance path between the outlet of the second dielectric cylinder (204) and the workpiece to be processed, the density has decayed to a much lower concentration than the neutral gas and radicals, and thus may be negligible. Preferably, the preset distance between the outlet of the second medium cylinder (204) and the workpiece to be processed can be in the range of 60mm-300mm. In particular, the preset distance may be configured to be 200mm. The shape of the cross-section (508) at the exit of the second media cartridge (204) may be configured to control the area of the workpiece to be processed covered by radicals.

Fig. 4 shows a cross-sectional view from the outlet of the second media cartridge (204) in a second direction. In this embodiment, the cross-section (508) has a rectangular cross-sectional shape. However, the cross-sectional shape of the cross-section (508) may be configured in any shape. The rectangular cross-section has a length (509) inside, which length (509) can be denoted as L. Also, the rectangular cross-section has a width (510) inside, which width (510) can be denoted as W. The internal length L of the rectangular cross section determines the coverage area of the plasma in the reaction chamber (100), which provides an effective adjustment means for obtaining large area surface plasma density uniformity in the reaction chamber (100). Preferably, the inner length L of the rectangular cross section may be configured to be larger than the diameter of the base (503).

As an example, the workpiece to be processed may be a SiC semiconductor wafer. An ion beam from the ionized first reactive gas enters the reaction chamber (100) simultaneously with the ionized second reactive gas. The ion beam bombards the SiC wafer under the action of gravity or a voltage biased pedestal (503), breaking the Si-C bond in the SiC wafer, and the fluorine (F) radical reacts with Si to generate SiF ₄ Volatile gas, siF ₄ The volatile gas is discharged out of the reaction chamber (100) under the action of a vacuum system (701)。

Preferably, the residence time of the gas on the surface of the workpiece to be processed can be further shortened so as to reduce the adverse effect of the excessive residence time of the by-products on the etching uniformity. As an example, for a workpiece to be processed having a diameter of 200mm, the residence time is preferably less than 20ms, that is, the difference in radial velocity of the reaction gas at the surface of the workpiece to be processed is preferably more than 10m/s.

The ion source and the free radical generating source respectively form ions and free radicals required by the etching of the workpiece to be processed, so that the ion concentration and the free radical concentration can be independently controlled, and the etching process can be more flexibly controlled.

Meanwhile, ions and free radicals are generated by the discrete ion source and the free radical generating source respectively and then are contacted with the workpiece to be processed through the reaction chamber (100), so that the workpiece to be processed can be effectively prevented from being directly exposed to a plasma generating area, high-density ion beams and high-density free radicals can be obtained, the etching rate is remarkably improved, meanwhile, the plasma radiation heating is greatly reduced, the bonding and bonding release caused by high temperature of bonds and sheets in the etching process is avoided, and the lower surface temperature of the workpiece to be processed is obtained while the etching rate is improved.

Claims

1. A semiconductor processing apparatus, comprising:

a reaction chamber, wherein a base (503) for bearing a workpiece to be processed is arranged in the reaction chamber;

a first plasma generation cavity (601), the first plasma generation cavity (601) being communicated with the reaction chamber through a filter grid, and being used for receiving a first reaction gas and providing an ion beam derived from the first reaction gas to the workpiece to be processed along a first direction, wherein the filter grid is used for suppressing electrons in the ionized reaction gas in the first plasma generation cavity (601);

the second plasma generation cavity (602), the second plasma generation cavity (602) is communicated with the reaction chamber, and the outlet of the second plasma generation cavity is away from the base by a distance greater than a preset distance, and is used for receiving a second reaction gas and providing free radicals derived from the second reaction gas to the workpiece to be processed along a second direction; and

the vacuum system is communicated with the reaction chamber, is arranged opposite to the second plasma generating cavity and is used for accelerating the free radicals to move towards the workpiece to be processed;

wherein the first direction is at an angle to the second direction;

wherein the second direction is parallel to the surface of the workpiece to be processed, and the predetermined distance is configured such that the density of ions and electrons originating from the second reactive gas after passing through the predetermined distance is attenuated to be much lower than the concentration of the radicals.

2. The semiconductor processing apparatus of claim 1, wherein the base (503) is coupled to a bias power supply to attract the ion beam to accelerate in the first direction toward the workpiece to be processed.

3. The semiconductor processing apparatus of claim 2, wherein the bias power supply has a frequency of 0.4MHz to 13.56MHz.

4. The semiconductor processing apparatus of claim 1, wherein the filter grid (302) is coupled to a dc bias power supply to accelerate the ion beam in the first direction toward the workpiece to be processed.

5. The semiconductor processing apparatus of claim 4, wherein the filter grid is located a minimum distance of 10mm to 100mm from the susceptor.

6. The semiconductor processing apparatus of claim 1, wherein the predetermined distance is in a range of 60mm to 300mm.

7. The semiconductor processing apparatus of claim 6, wherein the predetermined distance is 200mm.

8. The semiconductor processing apparatus of claim 1, wherein the first direction is at a 90 ° angle to the second direction.

9. The semiconductor processing apparatus of claim 1, wherein the second direction is parallel to a surface of the workpiece to be processed.

10. The semiconductor processing apparatus of claim 1, wherein the first plasma generation chamber (601) comprises:

a first media cartridge (104) and a first induction coil (103) disposed around the first media cartridge, the first media cartridge being axially parallel to the first direction.

11. The semiconductor processing apparatus of claim 10, wherein:

the first media cartridge (104) is coupled to a first gas transport module (401), the first gas transport module (401) configured to provide a first reactant gas to the first media cartridge (104); and is

The first induction coil (103) is coupled to a first radio frequency power supply (101) via a first matching circuit (102).

12. The semiconductor processing apparatus of claim 1, wherein the second plasma generation chamber (602) comprises:

a second media cartridge (204) and a second induction coil (203) disposed around the second media cartridge, and the second media cartridge axial direction is parallel to the second direction.

13. The semiconductor processing apparatus of claim 12, wherein:

the second media cartridge (204) is coupled to a second gas transport module (402), the second gas transport module (402) configured to provide a second reactant gas to the second media cartridge (204); and

the second inductive coil (203) is coupled to a second radio frequency power supply (201) via a second matching circuit (202).

14. The semiconductor processing apparatus of claim 13, wherein a shape of a cross-section (508) of the second media cartridge (204) along the second direction is configured to control an area of the workpiece to be processed covered by the radicals.

15. The semiconductor processing apparatus according to claim 14, wherein the cross-section (508) is rectangular in shape, a length (509) of a long side of the rectangle being configured to control an area of the workpiece to be processed covered by the radicals.

16. The semiconductor processing apparatus of claim 1, wherein the workpiece to be processed comprises a SiC semiconductor wafer.