Plasma device and plasma density regulation method

Abstract

The present invention provides a plasma device and a plasma density regulation method. The device comprises: a device body, wherein a step is formed between an upper section and a lower section of a cavity of the device body, and a resonant coil (3) is provided on the cavity; and a regulating unit configured for regulating a density of plasma in the cavity and provided outside the cavity, the regulating unit comprising: an upper permanent magnet (5) arranged on an upper track (6) and located on one side of the cavity, a wafer film thickness corresponding to that side being lower than a wafer film thickness corresponding to other positions of the cavity; a lower permanent magnet, configured for forming a magnetic force line with the upper permanent magnet (5), the magnetic force line being located in the cavity, and the lower permanent magnet and the upper permanent magnet (5) being arranged correspondingly; the lower permanent magnet is positioned on a lower track, the lower track being sleeved over an outside of the resonant coil (3) and positioned on the step, and the upper track (6) and the lower track being connected by means of a support rod. The present invention utilizes magnetic force lines to adjust plasma distribution within a cavity to be uniform, and improves wafer film uniformity.

Description

Plasma equipment and methods for adjusting plasma density Technical Field

[0001] This invention belongs to the field of semiconductor manufacturing equipment technology, specifically relating to a plasma device and a method for adjusting plasma density. Background Technology

[0002] As integrated circuits develop towards larger scale and higher integration, the need to reduce semiconductor deposition process temperatures is becoming increasingly urgent in order to achieve high-quality thin film deposition. This necessitates the development of technologies that can form thin films with higher flatness at even lower temperatures. Compared to traditional heating processes, plasma-enhanced processes use an external electric field and rely on radio frequency induction to ionize the target material source gas, generating plasma. This increases the activity of the reactants and lowers the required reaction temperature to below 450 degrees Celsius. For example, the nitride oxidation process used in DRAM manufacturing achieves selective nitride oxidation through ion enhancement processes such as ICP / CCP.

[0003] However, since the plasma is not uniformly distributed within the cavity, it is affected by factors such as the position of the molecular pumping port and the spiral shape of the resonant coil. Therefore, the room for improvement in the uniformity of the nitrided and oxidized films is limited by methods such as adjusting the position of the resonant coil. Summary of the Invention

[0004] The purpose of this invention is to provide a plasma device and a method for adjusting plasma density. A permanent magnet is installed on the side of the resonant coil where the plasma concentration is low to form a magnetic field. The magnetic field lines are used to adjust the plasma distribution within the cavity to a more uniform manner, thereby improving the uniformity of the wafer film (nitride film or oxide film). The technical solution adopted is as follows:

[0005] A plasma device, comprising:

[0006] The device body has a step between its upper and lower sections, and a resonant coil is provided on the upper section of the cavity;

[0007] A regulating unit, used to regulate the density of plasma within the cavity, is disposed outside the cavity and includes:

[0008] The upper permanent magnet is set on the upper track and is located on one side of the cavity. The wafer film thickness on this side is lower than the wafer film thickness on other sides of the cavity.

[0009] The lower permanent magnet is used to form magnetic lines of force with the upper permanent magnet. The magnetic lines of force are located inside the cavity. The lower permanent magnet is arranged correspondingly to the upper permanent magnet. The lower permanent magnet is arranged on the lower track.

[0010] The upper and lower rails are connected by a support rod.

[0011] Preferably, the upper track includes:

[0012] The outer track is connected to the outer track of the lower track via the support rod;

[0013] The inner ring track is fixed to the outer ring track and forms an installation gap with it;

[0014] The upper permanent magnet is located within the installation gap and is engaged between the outer and inner ring tracks;

[0015] The S pole of the upper permanent magnet is positioned facing the cavity; the N pole of the upper permanent magnet is positioned away from the cavity.

[0016] Preferably, a connecting strip is welded between the inner and outer ring tracks, and the connecting strip extends radially.

[0017] Preferably, the upper fixing block is sleeved on the upper rail or threadedly connected to the upper rail.

[0018] Preferably, the number of the upper permanent magnets is ≥1; the S poles of adjacent upper permanent magnets are in contact;

[0019] One of the upper fixing blocks is located on one side of the first upper permanent magnet, and the other upper fixing block is located on one side of the last upper permanent magnet.

[0020] Preferably, both the upper and lower permanent magnets are bar-shaped or horseshoe-shaped permanent magnets.

[0021] Preferably, the support rod is welded between the upper and lower rails.

[0022] Preferably, the upper track and the upper fixing block are both made of stainless steel.

[0023] A method for adjusting plasma density, based on the aforementioned plasma device, includes the following steps:

[0024] Step 1: Assemble the adjustment unit on the outside of the cavity;

[0025] Step 2: The equipment body undergoes a plasma nitriding or plasma oxidation process to achieve uniform plasma distribution under the action of the magnetic field formed by the magnetic field lines.

[0026] Compared with the prior art, the advantages of the present invention are:

[0027] By adding a permanent magnet to the side of the resonant coil where the plasma concentration is low, a magnetic field is formed. The plasma distribution in the cavity is adjusted to be more uniform by using magnetic field lines, which can improve the uniformity of the wafer film (nitride film or oxide film). Attached Figure Description

[0028] Figure 1 is a structural diagram of the device body in the prior art;

[0029] Figure 2 is a structural diagram of the adjustment unit assembled on the main body of the device in Figure 1;

[0030] Figure 3 is a top view of the upper track in the adjustment unit.

[0031] Among them, 1-wafer, 2-stage, 3-resonant coil, 4-molecular pump port, 5-upper permanent magnet, 6-upper track, 7-upper fixing block. Detailed Implementation

[0032] The plasma device and plasma density adjustment method of the present invention will be described in more detail below with reference to the schematic diagrams, which illustrate preferred embodiments of the invention. It should be understood that those skilled in the art can modify the invention described herein while still achieving its advantageous effects. Therefore, the following description should be understood as being of general knowledge to those skilled in the art and is not intended to limit the invention.

[0033] As shown in Figure 1, in existing plasma devices, the plasma distribution within the cavity is not uniform. It is affected by factors such as the position of the molecular pump port and the spiral shape of the resonant coil, resulting in inconsistent film thickness and poor uniformity on the wafer. Figure 1 shows a transfer gate installed on the cavity.

[0034] The process chamber is a quartz chamber, which includes a plasma generation space and a wafer processing space.

[0035] A stage 2 is provided at the lower part of the cavity. The stage is located in the wafer processing space inside the process chamber. A heater is embedded in the stage to heat the wafer 1 by electricity.

[0036] A resonant radio frequency coil 3 is located at the upper part of the cavity, arranged around the outer circumference of the plasma generation chamber. A radio frequency (RF) sensor, a high-frequency power supply, and a matching device capable of performing impedance matching or output frequency matching operations on the high-frequency power supply are connected to the resonant coil. (Not shown in the figure.) The matching device is configured to adjust the impedance of the high-frequency power supply or the frequency of the RF power output from the high-frequency power supply based on the reflected wave information input from the RF sensor, thereby minimizing the reflected wave.

[0037] A process gas vent is provided at the top of the cavity, through which the process gas enters the cavity and is excited by the radio frequency coil to form plasma. A vacuum vent 4 is provided at the bottom of the cavity, which is connected to a vacuum pump to control the pressure inside the cavity.

[0038] The resonant coil 3 is connected to an RF sensor, a high-frequency power supply, and a matching circuit (not shown in Figure 1) for impedance or output frequency matching of the high-frequency power supply. The high-frequency power supply provides high-frequency power to the resonant coil 3, generating a ring-shaped plasma ring near the resonant coil 3 and along the plasma generation region of the cavity. The spiral shape of the resonant coil 3 causes the plasma ring to have different heights from the wafer at different positions, and the plasma diffusion rate in different directions toward the wafer is affected by the position of the molecular pumping port 4.

[0039] The improvement in uniformity of nitrided and oxide films is limited by methods such as adjusting the position of the resonant coil 3Coil.

[0040] The wafer film thickness will be thinner in areas with lower plasma concentration.

[0041] Therefore, in this embodiment, a permanent magnet is installed on the side of the resonant coil 3 (Coil) with a low plasma concentration to form a magnetic field, forming magnetic lines of force inside the cavity to confine the plasma. The plasma distribution inside the cavity is adjusted to be more uniform by using magnetic lines of force. The unilateral magnetic control technology can significantly improve the uniformity of the oxide nitride film.

[0042] As shown in Figures 2 and 3, a plasma device includes:

[0043] The device body has a step between the upper and lower sections of its cavity, and a resonant coil 3 is installed on the cavity.

[0044] An adjustment unit, used to adjust the density of the plasma within the cavity, is disposed outside the cavity and includes:

[0045] The upper permanent magnet 5 is set on the upper track 6 and located on one side of the cavity. The wafer film thickness corresponding to this side is lower than the wafer film thickness corresponding to other positions in the cavity.

[0046] Among them, the film thickness measuring machine can measure film thickness, which is a common method in the industry.

[0047] The lower permanent magnet is used to form magnetic lines of force with the upper permanent magnet 5. The magnetic lines of force are located inside the cavity, and the lower permanent magnet and the upper permanent magnet 5 are arranged correspondingly above and below each other.

[0048] "Corresponding setting" means that the number of magnets is the same and the lower permanent magnet is located directly below the upper permanent magnet 5.

[0049] Therefore, an upper permanent magnet 5 and the lower permanent magnet directly below it form a magnetic field. As shown in Figure 3, the combination of several small magnets (upper permanent magnet 5), i.e., the adjustment unit, can be regarded as a large magnet. Therefore, the upper permanent magnet 5 only forms magnetic field lines with the lower permanent magnet directly below it.

[0050] The lower permanent magnet is placed on the lower track; the outer ring of the lower track is fitted around the outside of the resonant coil 3 and placed on the step.

[0051] The upper track 6 and the lower track are connected by a support rod. Specifically, the support rod is welded between the upper track 6 and the lower track.

[0052] As shown in Figure 2, since the support rod is connected to the outer ring track of the upper track 6, the support bar in Figure 3 is connected to the right section of the outer ring track as a whole.

[0053] The installation methods for the upper permanent magnet 5 and the lower permanent magnet are the same.

[0054] The specific installation method of the upper permanent magnet 5 is as follows:

[0055] The upper track includes:

[0056] The outer track is connected to the outer track of the lower track via a support rod;

[0057] The inner track is fixed to the outer track, forming an installation gap. Specifically, a connecting strip is welded between the inner and outer tracks, extending radially. This connecting strip is located outside the adjustment unit.

[0058] As shown in Figure 3, the connecting strip is not displayed.

[0059] Preferably, the inner track is positioned in the upper section of the cavity where there is no resonant coil 3.

[0060] The upper permanent magnet 5 is located within the installation gap and is locked between the outer track and the inner track.

[0061] The S pole of the upper permanent magnet 5 is positioned facing the cavity; the N pole of the upper permanent magnet is positioned away from the cavity.

[0062] The upper fixing block 7 is used to limit the upper permanent magnet 5.

[0063] The upper fixing block 7 is fitted onto the upper rail 6, or is threadedly connected to the upper rail 6.

[0064] That is, hole one, which is adapted to the outer ring track, and hole two, which is adapted to the inner ring track, are made on the upper fixing block 7.

[0065] The number of upper permanent magnets 5 is ≥1; the S poles of adjacent upper permanent magnets 5 are in contact. That is, the number of permanent magnets can be increased or decreased according to the wafer uniformity to compensate for the plasma concentration.

[0066] One of the upper fixing blocks 7 is located on one side of the first upper permanent magnet 5, and the other upper fixing block 7 is located on one side of the last upper permanent magnet 5.

[0067] Both the upper permanent magnet 5 and the lower permanent magnet are made of bar permanent magnets or horseshoe permanent magnets.

[0068] When the upper permanent magnet 5 is a horseshoe-shaped permanent magnet, the opening of the upper permanent magnet 5 is set to face upward.

[0069] When the upper permanent magnet 5 is a bar permanent magnet, the upper permanent magnet 5 is set horizontally.

[0070] The specific installation method for the lower permanent magnet is as follows:

[0071] The lower track includes:

[0072] The outer track is connected to the outer track of the upper track via a support rod;

[0073] The inner track is fixed to the outer track and forms an installation gap with it. Specifically, a connecting strip is welded between the inner and outer tracks, the connecting strip extending radially.

[0074] Preferably, the inner track is positioned in the lower section of the cavity where there is no resonant coil 3.

[0075] The lower permanent magnet is located within the installation gap and is secured between the outer track and the inner track.

[0076] The N pole of the lower permanent magnet is positioned facing the cavity; the S pole of the lower permanent magnet is positioned away from the cavity.

[0077] The lower fixing block is used to limit the lower permanent magnet, and it is located on both sides of the non-magnetic pole of the lower permanent magnet.

[0078] In this embodiment, the position of the permanent magnet can be moved according to the wafer uniformity to ensure uniform plasma distribution. This allows the plasma to diffuse uniformly into the wafer, forming a thin film of equal thickness and improving the uniformity of the oxide nitride film.

[0079] Therefore, in this embodiment, the upper permanent magnet 5 and the lower permanent magnet need to be configured to move along their respective tracks, and the principles are the same. The upper permanent magnet 5 will be described below:

[0080] When the upper permanent magnet 5 is mounted on the upper track 6:

[0081] The diameter of the first hole on the fixing block 7 is slightly larger than the outer diameter of the outer ring of the upper track 6; the diameter of the second hole on the upper permanent magnet 5 is slightly larger than the outer diameter of the inner ring of the upper track 6, so that the fixing block 7 can be installed at any position on the circumference.

[0082] When the upper permanent magnet 5 is threadedly connected to the upper track 6:

[0083] The inner and outer rings of the upper track 6 each have a full circle of external threads, allowing the fixing block 7 to be installed at any position on the circumference.

[0084] Furthermore, the upper track 6, upper fixing block 7, lower track, and lower fixing block are all made of stainless steel or other materials.

[0085] The method for adjusting plasma density includes the following steps:

[0086] Step 1: Assemble the adjustment unit on the outside of the cavity;

[0087] Step 2: The equipment body undergoes a plasma nitriding or plasma oxidation process to achieve uniform plasma distribution under the action of the magnetic field formed by the magnetic field lines.

[0088] The uniformity of plasma distribution is characterized by the uniformity of film thickness: the wafers in Figure 1 have different thicknesses, while the wafers in Figure 2 have uniform thicknesses.

[0089] The above are merely preferred embodiments of the present invention and do not constitute any limitation on the present invention. Any equivalent substitutions or modifications made by those skilled in the art to the technical solutions and content disclosed in the present invention without departing from the scope of the present invention shall be deemed to have remained within the scope of protection of the present invention.

Claims

1. A plasma device, characterized in that, include: The device body has a step between its upper and lower sections, and a resonant coil is provided on the upper section of the cavity; A regulating unit, used to regulate the density of plasma within the cavity, is disposed outside the cavity and includes: The upper permanent magnet is set on the upper track and is located on one side of the cavity. The wafer film thickness on this side is lower than the wafer film thickness on other sides of the cavity. The lower permanent magnet is used to form magnetic lines of force with the upper permanent magnet. The magnetic lines of force are located inside the cavity. The lower permanent magnet is arranged correspondingly to the upper permanent magnet. The lower permanent magnet is arranged on the lower track. The upper and lower rails are connected by a support rod.

2. The plasma device according to claim 1, characterized in that, The upper track includes: The outer track is connected to the outer track of the lower track via the support rod; The inner ring track is fixed to the outer ring track and forms an installation gap with it; The upper permanent magnet is located within the installation gap and is engaged between the outer and inner ring tracks; The S pole of the upper permanent magnet is positioned facing the cavity; the N pole of the upper permanent magnet is positioned away from the cavity.

3. The plasma device according to claim 2, characterized in that, A connecting strip is welded between the inner and outer rails, and the connecting strip extends radially.

4. The plasma device according to claim 2, characterized in that, The upper fixing block is sleeved on the upper rail or threadedly connected to the upper rail.

5. The plasma device according to claim 2, characterized in that, The number of the upper permanent magnets is ≥1; the S poles of adjacent upper permanent magnets are in contact; One of the upper fixing blocks is located on one side of the first upper permanent magnet, and the other upper fixing block is located on one side of the last upper permanent magnet.

6. The plasma device according to claim 1, characterized in that, Both the upper and lower permanent magnets are made of bar-shaped or horseshoe-shaped permanent magnets.

7. The plasma device according to claim 1, characterized in that, The support rod is welded between the upper and lower rails.

8. The plasma device according to claim 1, characterized in that, The upper track and the upper fixing block are both made of stainless steel.

9. A method for adjusting plasma density, based on the plasma device according to any one of claims 1 to 8, characterized in that, Includes the following steps: Step 1: Assemble the adjustment unit on the outside of the cavity; Step 2: The equipment body undergoes a plasma nitriding or plasma oxidation process to achieve uniform plasma distribution under the action of the magnetic field formed by the magnetic field lines.

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