Method for processing baffle plate of PVD (physical vapor deposition) equipment

Abstract

According to the invention, there is provided a method for treating a baffle of a PVD device, comprising the following steps: providing a PVD device, the apparatus includes a chamber, a target, a substrate support positioned in the chamber, and a baffle within the chamber deployable to divide the chamber into a first compartment in which the substrate support is positioned and a second compartment in which the target is positioned; providing a substrate having an adhesive material deposited thereon, the substrate positioned on the substrate support; deploying the baffle within the chamber to divide the chamber into the first and second compartments, the baffle having a bottom side facing the substrate in its deployed position with at least one contaminant material present on the bottom side; and generating a plasma in the first compartment to sputter etch an adhesive material onto the bottom side of the baffle to adhere the contaminant material to the bottom side of the baffle.

Description

Technical Field

[0001] This invention relates to a method for treating a baffle in a PVD (Polydimer Deposition and Removal) apparatus, and more particularly to a method for adhering material to the baffle in order to adhere contaminant material to the baffle. The invention also relates to an associated PVD apparatus including a baffle. Background Technology

[0002] It is known to reduce the contact resistance of UBM / RDL (Under-Bump Metallization / Redistribution Layer) structures on wafer substrates by reducing the amount of oxide present at the interface between the Al contact pads and the PVD Ti seed layer. To achieve this reduction in oxide presence, the wafer is first degassed under vacuum conditions to remove H2O and other volatile contaminants that may oxidize the pad surface or interfere with the electrical properties of the subsequently deposited metal film. This is followed by sputter etching to remove the native oxide from the Al pads. Sputter etching processes present problems because the passivation materials typically used in UBM / RDL processes are organic polymers, such as PI (polyimide) or PBO (polybenzoxazole). When such materials undergo a sputter etching process, they decompose into smaller organic components, which can then be re-oxidized on the sputter-cleaned Al surface. This oxide layer regeneration leads to an increase in contact resistance. The amount of oxide regeneration depends on several factors, one of which is the time delay between the end of the etching process and the start of the PVD process. Typically, the wafer is etched in a dedicated sputter etching module and then transferred to a dedicated deposition module, such as a PVD apparatus, via a vacuum process. The time delay in transferring the wafer from the sputtering etching module to the PVD equipment can lead to undesirable levels of oxide regeneration on the wafer.

[0003] The applicant has previously described an invention addressing this problem in European patent application EP 4207 245A1. The applicant's inventive method utilizes baffles deployed within the chamber of a PVD apparatus. A second etching is performed within the chamber, wherein the baffles are deployed to remove regenerated oxide. Because this process operates in situ, the transition time between the end of etching and the start of deposition is significantly reduced, thus greatly reducing the amount of oxide regeneration and consequently reducing contact resistance.

[0004] However, the inventors have realized that as more wafers are etched, organic materials gradually accumulate on the chamber architecture (e.g., shielding). This presents a problem because such materials can delaminate, leading to particle performance degradation within the chamber and providing a source of contamination that affects the resistivity of the PVD-deposited film. The PVD deposition process itself can help control particles and contaminants that might otherwise delaminate by adhering them to the chamber walls and the architecture (e.g., shielding) beneath the layers of PVD-deposited material. However, the inventors have realized that portions of the chamber are within the line of sight of the etching process but not the deposition process, particularly the bottom side of the baffle. Particles and contaminants located here are not adhered in place by the PVD deposition process and thus become potential sources of contaminants within the chamber. Summary of the Invention

[0005] The present invention addresses the problems described above in at least some of its embodiments. Specifically, the present invention provides a practical solution in at least some of its embodiments to the problem of contaminant material accumulation on the underside of a baffle located in a PVD device.

[0006] According to a first aspect of the present invention, a method for processing a baffle of a PVD device is provided, comprising the following steps:

[0007] A PVD apparatus is provided, comprising a chamber, a target, a substrate support positioned in the chamber, and a baffle deployable within the chamber to divide the chamber into a first compartment in which the substrate support is positioned and a second compartment in which the target is positioned.

[0008] A substrate comprising an adhesive material is provided, the substrate being positioned on the substrate support;

[0009] The baffle is deployed within the cavity to divide the cavity into first and second compartments, the baffle having a bottom side facing the substrate at its deployment position, wherein at least one contaminant material is present on the bottom side; and

[0010] Plasma is generated in the first compartment to sputter and etch the adhesive material onto the bottom side of the baffle, thereby adhering the contaminant material to the bottom side of the baffle.

[0011] This invention provides a practical solution that can be easily integrated into various PVD deposition processes.

[0012] The substrate including the adhesive material can be a base substrate on which the adhesive material is deposited. The base substrate on which the adhesive material is deposited can be provided by positioning the base substrate on the substrate support and depositing the adhesive material on the base substrate using the PVD apparatus via PVD. Alternatively, the base substrate on which the adhesive material is formed can be provided by depositing the adhesive material on the base substrate outside the chamber, wherein the base substrate is subsequently positioned on the substrate support.

[0013] Alternatively, the substrate may consist of or be substantially composed of the adhesive material. For example, the substrate may be provided as a body formed of the adhesive material, such as a disk formed of the adhesive material.

[0014] The adhesive material may be titanium. In this example, the target material may be formed of titanium. This is convenient if the primary PVD deposition process is titanium deposition and the adhesive material is also titanium. This allows for providing a substrate with the adhesive material deposited thereon by positioning the substrate on the substrate support and using the PVD equipment to deposit titanium onto the substrate via PVD. This is also true for any other example where the primary PVD deposition process deposits the same material as the adhesive material.

[0015] Alternatively, the adhesive material may be barium, cerium, or aluminum.

[0016] The PVD apparatus can be configured to perform the PVD deposition step independently. During the step of sputtering and etching the adhesion material onto the bottom side of the baffle, the substrate support can be in a first position, and during the step of performing the PVD deposition step, the substrate support can be in a second position, wherein the second position is closer to the target than the first position. These configurations have been found to enhance the effectiveness of both steps.

[0017] The step of sputtering and etching an adhesive material onto the bottom side of the baffle can be performed, wherein the spacing between the substrate and the bottom side of the baffle is in the range of 25 to 75 mm.

[0018] The step of generating plasma in the first compartment may include generating the plasma by applying an RF electrical signal to the substrate support. While generating the plasma by applying the RF electrical signal to the substrate support, the baffle may be grounded. Typically, the baffle is permanently grounded.

[0019] The contaminant material may be an organic material. The organic material may be formed after PVD treatment of a substrate comprising an organic polymer. The organic polymer may be PI or PBO.

[0020] The organic material can be formed after PVD treatment of a substrate including an organic dielectric material.

[0021] The method may further include the following prior steps:

[0022] The workpiece semiconductor substrate, on which conductive features are formed, is positioned on the substrate support.

[0023] The baffle is deployed within the cavity to divide the cavity into the first and second compartments; and

[0024] Simultaneously, a first plasma is maintained in the first compartment to remove material from the conductive feature and a second plasma is maintained in the second compartment to clean the target material, wherein the removal of material from the conductive feature results in the contaminant material on the bottom side of the baffle.

[0025] The applicant’s European patent application EP 4207 245A1 (the contents of which are incorporated herein by reference) describes a method according to these prior steps. However, those skilled in the art will appreciate that the present invention can be used in conjunction with a wide range of PVD deposition applications, which may or may not involve PVD deposition on a substrate on which conductive features are formed.

[0026] The substrate on which the adhesive material is deposited can be a semiconductor substrate. The semiconductor substrate can be a semiconductor wafer.

[0027] According to a second aspect of the present invention, a PVD apparatus is provided, comprising:

[0028] The chamber includes a substrate support and a target material;

[0029] A baffle, which can be deployed in the cavity when a substrate including an adhesive material is positioned on the substrate support during use, wherein the baffle is deployed to divide the cavity into a first compartment in which the substrate support is positioned and a second compartment in which the target is positioned, and the baffle has a bottom side facing the substrate support in its deployment position.

[0030] A plasma generation apparatus for generating plasma in the first compartment to sputter and etch an adhesion material from the substrate onto the bottom side of the baffle, thereby adhering any contaminant material present on the bottom side of the baffle; and

[0031] A controller configured to control the device in use to (i) deploy the baffle and (ii) generate the plasma in the first compartment to sputter-etch the adhesive material.

[0032] The PVD apparatus can be configured to perform the PVD deposition step independently. The controller and the substrate support can be configured such that the substrate support is in a first position during the step of sputtering and etching the adhesion material onto the bottom side of the baffle, and in a second position during the step of performing the PVD deposition step, wherein the second position is closer to the target than the first position.

[0033] The controller can be configured to control the position of the substrate support such that the spacing between the substrate and the bottom side of the baffle is in the range of 25 to 75 mm, preferably in the range of 30 to 70 mm, while generating the plasma in the first compartment to sputter etch the adhesive material.

[0034] The PVD apparatus may further include an anode structure that generally or completely surrounds the target, wherein plasma can be generated between the target and the anode structure.

[0035] Generally, the magnetron assembly is positioned behind the target, as is well known to those skilled in the art.

[0036] For the avoidance of doubt, whenever the terms “comprising” or “including” and similar terms are used herein, the invention is also to be understood to include more restrictive terms, such as “consisting of” and “substantially composed of”.

[0037] While the invention has been described above, it extends to any inventive combination of the features set forth in the foregoing or hereinafter description, drawings, or claims. Any feature disclosed with respect to the first aspect of the invention may be suitably combined with any feature disclosed with respect to the second aspect of the invention, and vice versa. Attached Figure Description

[0038] Embodiments of the invention will now be described by way of example only with reference to the accompanying drawings, in which:

[0039] Figure 1 This is a half-sectional schematic diagram of the PVD apparatus of the present invention during PVD deposition, wherein the baffle is in the retracted position; and

[0040] Figure 2 This is a cross-sectional schematic diagram of the PVD equipment of the present invention during the baffle processing step, wherein the baffle is in the deployment position. Detailed Implementation

[0041] Figure 1 and 2 The PVD apparatus of the present invention is demonstrated. The apparatus is capable of deposition mode (in...) Figure 1 It can operate in (as shown in the image) and can also be used in cleaning mode (in the image). Figure 2The apparatus operates under the following conditions (shown in the diagram) to remove material from conductive features formed on a semiconductor substrate 28. The device includes a chamber 10 comprising a substrate support 12 (e.g., a pressure plate) and a target 14. A power supply 16 supplies power to the target 14 to generate and maintain plasma for PVD deposition, as understood by those skilled in the art. The power supply 16 can be of any suitable type, such as DC, pulsed DC, or RF power. The target 14 is electrically isolated from the grounded chamber 10 by a dielectric break 18. A rotating magnetron assembly 20 is swept around the target 14 by a motor 22 to capture electrons near the target to improve deposition performance. The substrate support 12 is RF-driven by an RF power supply 24 operating at a suitable frequency (typically 13.56 MHz) via a matching network 26 to provide a DC bias Vdc to the semiconductor substrate 28 positioned on the substrate support 12. The substrate support 12 includes a pressure plate 12a and a base 12b, the base 12b typically being made of aluminum or stainless steel and electrically isolated from the metal chamber 10 by a ceramic spacer 30. Temperature control of the substrate support is achieved by conventional methods, such as resistance heating and cooling channels with temperature sensors (not shown).

[0042] During PVD deposition cycles, the equipment such as Figure 1 The configuration is as shown in the diagram. A suitable process gas (e.g., Ar or Ar and N2) is introduced into chamber 10 through inlet 32. Electricity is applied to target 14, and plasma 34 is formed in chamber 10 adjacent to target 14. Positive ions (e.g., Ar+) are directed to target 14, sputtering target material into chamber 10 toward wafer 28. The walls of the chamber are protected by chamber shield 36, which is typically a metallic construction with a textured surface to aid in the adhesion of the sputtered film. Chamber 10 is pumped through opening 38 by a suitable pumping system (typically utilizing a cryogenic pump). Substrate support 12 is in an elevated position to maintain a desired gap between the target and the semiconductor substrate, typically about 50 to 70 mm.

[0043] The apparatus further includes a baffle 40. During PVD deposition, the baffle 40 is stored in a location within the housing 42 coupled to the chamber 10 (in... Figure 1 (As shown in the image). The baffle 40 can be deployed within the chamber 10 by direct horizontal drive from a suitable mechanism 44. The deployment position of the baffle is in... Figure 2As shown in the diagram. The baffle 40 is electrically grounded when deployed. The chamber shield 36 and the baffle 40 are specifically designed for long MTBC (Mean Time Between Cleanings) by using an arc-sprayed coating on all surfaces (top and bottom). This provides good adhesion for sputtered species. A suitable material for the baffle is Al, which also provides good CTE (Coefficient of Thermal Expansion) properties and low warpage potential, ensuring process repeatability. Alternatively, the baffle can be made of materials such as titanium. The thickness of the baffle can be in the range of 10 to 15 mm. The apparatus further includes a controller 50 for controlling the operation of the control device.

[0044] Figure 2 The illustration shows a configuration in which a baffle 40 is deployed to divide a chamber into a first lower compartment 46 for positioning the substrate support 12 and a second upper compartment 48 for positioning the target 14. For the sake of simplicity, Figure 2 It did not reappear in China Figure 1 All reference figures provided. However, it will be understood that... Figure 2 Displayed in different configurations Figure 1 The equipment. Figure 1 All components of the device shown in the document are in Figure 2 Presented in EP 4207 245A1, after a semiconductor substrate 28 on which conductive features are formed is positioned on a substrate support 12, a baffle 40 is deployed. Pre-cleaning is performed, wherein optionally, an RF power supply 24 supplies RF power to the substrate support 12 to generate and maintain a first plasma 54 in a first compartment 46 to remove material from the conductive features. Optionally, a power supply 16 is used to power a target 14 to generate and maintain a second plasma (not shown) in a second compartment 48 to clean the target 14, as taught in EP 4207 245A1. The power supply is also used to generate and maintain plasma during PVD deposition. A controller 50 is configured to control the equipment in use to (i) deploy the baffle and (ii) simultaneously maintain the first plasma in the first compartment and the second plasma in the second compartment. In a representative process, a process gas, such as Ar, is introduced into the chamber, and Ar+ ions generated by the first plasma are attracted to the semiconductor substrate 28 on the RF-driven substrate support 12 due to -ve Vdc. As a result, material is sputtered from the surface of the semiconductor substrate 28. Oxidized metals, such as Al₂O₃, from the Al bonding pads are removed to produce native Al, while organic dielectric material is also removed. The material removed from the surface of the semiconductor substrate 28 is trapped on the exposed surfaces in regions 52a, 52b, and 52c, including the underside of the baffle, as shown in 52c. It should be noted that by lowering the base 12b, the substrate support 12... Figure 1The position of the base 12b is lowered to allow for the deployment of the baffle 40. The lowering and raising of the base 12b can be achieved by pneumatic or electric actuation using a stainless steel bellows assembly.

[0045] At the appropriate time, contaminant material adheres to the chamber, chamber structure, and baffles. The method used to achieve this will now be described. If the PVD equipment is in... Figure 2 The configuration shown in the image indicates that controller 50 enables the PVD device to display... Figure 1 The configuration is shown in the diagram. Once the baffle 40 retracts into the housing 42, deposition from the target 14 can be used to adhere contaminant material to regions 52a and 52b. During this process, the surface of the substrate support 12 is covered by the wafer being processed or an element such as a cover, conditioning wafer, or plate. However, it will be understood that contaminant material 52c on the underside of the baffle 40 cannot be reached by this form of adhesion.

[0046] According to the present invention, an adhesion step is performed on the bottom side of the baffle. In a non-limiting method, firstly using... Figure 1 The arrangement shown depicts the PVD deposition of a Ti film onto the upper surface of the wafer. In many cases, a relatively thin Ti film, for example, approximately 1000 nm thick, is sufficient. If the primary process deposits the Ti film, this can be performed in the same PVD module where subsequent adhesion steps are executed. In this example, while depositing Ti from target 14, a Ti film can be deposited on the wafer to adhere contaminant material in regions 52a and 52b. Alternatively, the Ti deposition step onto the wafer can be performed in a different chamber. Typical operating parameters for the Ti deposition step are shown in Table 1.

[0047] parameter Typical range Pressure (mTorr) 2 to 4 Target power (kWatt) 2 to 8 Ar flow rate (sccm) 50 to 200 Target-wafer spacing (mm) 50 to 70

[0048] Table 1.

[0049] This is followed by another adhesion step, in which contaminant material is adhered to the bottom side of the baffle. The substrate support and the newly deposited Ti wafer are lowered away from the target, the baffle is deployed in the chamber, and then... Figure 2The configuration shown in the figure runs an etching process on a Ti-deposited wafer. This process sputters Ti from the wafer, adhering to the chamber walls and the bottom side of the baffle. Typical operating parameters for the adhesion step are shown in Table 2. In this way, an etching rate of approximately 6.7 nm / min can be easily achieved. By positioning the baffle slightly below the plane in which PVD deposition occurs on the wafer, the accumulation of contaminant material below this plane is minimized. In a non-limiting example, the deployed baffle is located approximately 90 mm from the surface of the target. If a 300 mm diameter wafer is used, a baffle diameter of approximately 420 mm is appropriate to allow for a gap of approximately 8 mm with the surrounding shield. The substrate support 12 is lowered such that there is a gap of approximately 30 to 70 mm between the baffle and the wafer.

[0050] parameter Typical range Pressure (mTorr) 2 to 5 Ar flow rate (sccm) 100 to 200 RF power (Watts) 400 to 600

[0051] Table 2.

[0052] The frequency and extent of in-situ etching depend on the type and amount of material being etched. This can be easily adjusted for precise applications. Periodic adhesion of the baffles allows for control of particle energy levels, maintenance of vacuum performance, and thus low contact resistance and repeatability throughout the chamber performance management cycle. It also extends the lifespan of the chamber and its architecture.

[0053] It will be apparent that the present invention can be implemented in various ways. For example, other adhesive materials besides titanium, such as barium, cerium, or aluminum, can be used. It is advantageous if the material used as the adhesive also possesses good getter properties. However, this is not a critical quality. The present invention is also not limited to the processing of UBM / RDL structures. Those skilled in the art will understand that the present invention is applicable to a wide range of substrates, deposited films, and end applications.

Claims

1. A method of treating a shutter of a PVD apparatus, comprising the steps of: providing a PVD apparatus comprising a chamber, a target, a substrate support positioned in the chamber, and a shutter deployable within the chamber to divide the chamber into a first compartment in which the substrate support is positioned and a second compartment in which the target is positioned; providing a substrate comprising an adhesive material, the substrate positioned on the substrate support; deploying the shutter within the chamber to divide the chamber into the first and second compartments, the shutter having a bottom side that, in its deployed position, faces the substrate, wherein at least one contaminant material is present on the bottom side; and generating a plasma in the first compartment to sputter etch adhesive material onto the bottom side of the shutter, thereby adhering the contaminant material to the bottom side of the shutter.

2. The method of claim 1, wherein the substrate comprising an adhesive material is a base substrate on which the adhesive material is deposited.

3. The method of claim 2, wherein the base substrate on which the adhesive material is deposited is provided by positioning the base substrate on the substrate support and using the PVD apparatus to deposit the adhesive material on the base substrate by PVD.

4. The method of claim 2, wherein the base substrate on which the adhesive material is formed is provided by depositing the adhesive material on the base substrate outside the chamber, wherein the base substrate is subsequently positioned on the substrate support.

5. The method of claim 1, wherein the substrate consists of or consists essentially of the adhesive material.

6. The method of any one of claims 1-5, wherein the adhesive material is titanium.

7. The method of claim 6, when dependent on claim 3, wherein the target is formed of titanium.

8. The method of any one of claims 1-5, wherein the adhesive material is barium, cerium, or aluminum.

9. The method of any one of claims 1-5, wherein the PVD apparatus is configured to perform a PVD deposition step separately; and during the step of sputter etching adhesive material onto the bottom side of the shutter, the substrate support is at a first position, and during the step of performing the PVD deposition step, the substrate support is at a second position, wherein the second position is closer to the target than the first position.

10. The method of any one of claims 1-5, wherein the step of sputter etching adhesive material onto the bottom side of the shutter is performed with a spacing between the substrate and the bottom side of the shutter in a range of 25 to 75 mm.

11. The method of any one of claims 1-5, wherein the step of generating a plasma in the first compartment comprises generating the plasma by applying an RF electrical signal to the substrate support.

12. The method of claim 11, wherein the baffle is grounded while the plasma is generated by applying the RF electrical signal to the substrate support.

13. The method of any one of claims 1-5, wherein the contaminant material is an organic material.

14. The method of any one of claims 1-5, further comprising the following preceding steps: positioning a workpiece semiconductor substrate having electrically conductive features formed thereon on the substrate support; deploying the baffle within the chamber to divide the chamber into the first and second compartments; and simultaneously maintaining a first plasma in the first compartment to remove material from the electrically conductive features and a second plasma in the second compartment to clean the target, wherein removing material from the electrically conductive features results in the contaminant material on the bottom side of the baffle.

15. A PVD apparatus comprising: a chamber including a substrate support and a target; a baffle deployable within the chamber when a substrate having an adherent material deposited thereon in use is positioned on the substrate support, wherein the baffle is deployed to divide the chamber into a first compartment in which the substrate support is positioned and a second compartment in which the target is positioned, and the baffle has a bottom side that faces the substrate support in its deployed position; a plasma generating device to generate a plasma in the first compartment to sputter etch adherent material from the substrate onto the bottom side of the baffle, thereby adhering any contaminant material present on the bottom side of the baffle; and a controller configured to control the apparatus in use to (i) deploy the baffle, and (ii) generate the plasma in the first compartment to sputter etch the adherent material.

16. The PVD apparatus of claim 15, wherein the PVD apparatus is configured to separately perform a PVD deposition step; and the controller and the substrate support are configured such that the substrate support is at a first position during the step of sputter etching adherent material onto the bottom side of the baffle, and is at a second position during the step of performing the PVD deposition step, wherein the second position is closer to the target than the first position.

17. The PVD apparatus of claim 15 or claim 16, wherein the controller is configured to control the position of the substrate support such that the spacing between the substrate and the bottom side of the baffle is in the range of 25 to 75 mm while the plasma in the first compartment is generated to sputter etch the adherent material.

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