Chemical mechanical polishing apparatus and method for polishing high hardness semiconductor materials

Abstract

The present application relates to the field of chemical mechanical polishing, in particular to a chemical mechanical polishing device and a polishing method for high-hardness semiconductor materials, the device comprising a polishing platform, the upper surface of which is provided with a polishing disc, and a surrounding device is arranged on the outer side of the polishing platform around the peripheral part of the polishing disc, so that the space inside the surrounding device forms a liquid storage space for storing polishing liquid, and an ultrasonic generator is arranged on the polishing platform for generating ultrasonic waves inside the liquid storage space. By introducing the ultrasonic generator into the chemical mechanical polishing device, the activity of the abrasive in the polishing liquid is improved during the chemical mechanical polishing process, and the mechanical energy is also improved, so that the grinding capacity of the abrasive on the parts to be polished is further improved. The polishing efficiency for high-hardness semiconductor materials is greatly improved, and the processing time is greatly shortened.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of chemical mechanical polishing, in particular to a chemical mechanical polishing device and a polishing method for high-hardness semiconductor materials. BACKGROUND

[0002] Chemical mechanical polishing (CMP) is a means of global planarization in integrated circuit manufacturing. In the chemical mechanical polishing process, the surface material of the workpiece first undergoes a chemical reaction with oxidizing agents, catalysts, and the like in the polishing liquid to form a soft layer that is relatively easy to remove. Then, the soft layer is removed by the mechanical action of the abrasive in the polishing liquid and the polishing pad, so that the surface of the workpiece is exposed again, and then the chemical reaction is carried out again. In this way, the polishing of the surface of the workpiece is completed in the alternating process of chemical action and mechanical action.

[0003] Compared with the previously widely used mechanical polishing, chemical mechanical polishing can make the surface of the silicon wafer more planar, and also has the advantages of low processing cost and simple processing method, so it has become the most common surface planarization technology for semiconductor materials. However, the current chemical mechanical polishing technology still has a low defect removal efficiency for hard materials such as silicon carbide and gallium nitride substrates, resulting in a low polishing efficiency for high-hardness semiconductor materials.

[0004] For example, the application number CN202210930114.0 discloses a silicon wafer polishing device, which comprises a polishing disc and an auxiliary disc for carrying the silicon wafer. A wax layer is provided on the non-polishing surface of the silicon wafer, and the silicon wafer is connected to the auxiliary disc through the wax layer. The polishing surface of the silicon wafer attached to the auxiliary disc is polished on the polishing disc. The application also discloses a polishing method using the polishing device. The silicon wafer polishing device has a reasonable overall structure, can polish multiple groups of silicon wafers, especially can completely polish the edges of the silicon wafers, and can replace the polishing pad and the polishing liquid according to different process requirements without changing other structures, and can obtain silicon wafer surfaces with different standard requirements of flatness and roughness. SUMMARY

[0005] The present application is to overcome the defect that the surface defect removal efficiency of high-hardness semiconductor materials is low when using the chemical mechanical polishing technology, and therefore provides a chemical mechanical polishing device and a polishing method for high-hardness semiconductor materials.

[0006] To achieve the above-mentioned application purposes, the present application realizes the following technical solutions:

[0007] In a first aspect, the present application first provides a chemical mechanical polishing device,

[0008] The polishing platform comprises a polishing disc arranged on the upper surface of the polishing platform, a surrounding device is arranged on the outer side of the polishing platform around the peripheral part of the polishing disc, so that the internal space of the surrounding device forms a liquid storage space for storing the polishing liquid, and an ultrasonic wave generator is arranged on the polishing platform for generating ultrasonic waves inside the liquid storage space.

[0009] The polishing head assembly comprises a fixing device for fixing the workpiece to be polished and a pressing device for applying pressure to the polishing substrate and generating rotation.

[0010] The polishing liquid conveying device is used for conveying the polishing liquid into the liquid storage space.

[0011] In the prior art chemical mechanical polishing device, the abrasive in the polishing liquid is only passively contacted with the workpiece to be polished by applying a pressing force and a rotating force to the workpiece to be polished to rub and polish with the abrasive in the polishing liquid. For high-hardness semiconductor materials, when the conventional chemical mechanical polishing method is used, a longer grinding time is often required to remove the defect part on the surface of the workpiece to be polished due to the small mechanical energy between the abrasive and the workpiece to be polished.

[0012] Compared with the conventional chemical mechanical polishing device, the present application provides a surrounding device on the conventional polishing platform, so that the polishing liquid can be stored in the liquid storage space surrounded by the surrounding device during the chemical mechanical polishing process. Moreover, the polishing platform is also provided with an ultrasonic wave generator, so that the ultrasonic wave generator can emit ultrasonic waves to the polishing liquid stored in the liquid storage space. Since the ultrasonic waves can excite the abrasive in the polishing liquid to vibrate, the energy in the ultrasonic waves is converted into the mechanical energy of the abrasive, thereby effectively improving the grinding ability of the abrasive on the workpiece to be polished, greatly improving the polishing efficiency of the high-hardness semiconductor material and greatly shortening the processing time of the high-hardness semiconductor material. Moreover, since the workpiece to be polished is immersed in the polishing liquid during the whole polishing process, the penetration ability of the ultrasonic waves is improved, and the polishing effect of the ultrasonic waves on the workpiece to be polished is more excellent.

[0013] In addition, the addition of ultrasonic waves can make the oxide layer on the surface of the workpiece to be polished more easily broken and fallen during the grinding process, which also accelerates the polishing process of the high-hardness semiconductor material.

[0014] As a preferred embodiment, the upper surface of the polishing disc is detachably provided with a polishing pad for polishing the silicon carbide substrate.

[0015] In the polishing process of the present application, different polishing pads can be selected for use according to different polishing conditions, so that the surface finish of the silicon carbide substrate can be effectively controlled.

[0016] Preferably, the side wall of the enclosure device is provided with an outlet for the polishing liquid to flow out.

[0017] The purpose of setting the liquid outlet on the side wall of the enclosure device is to control the depth of the polishing liquid inside the liquid storage space, thereby preventing the polishing liquid from corroding and oxidizing the parts of the workpiece that do not need to be polished.

[0018] Preferably, the number of liquid outlets is at least 2, and they are evenly distributed on the side wall of the enclosure device.

[0019] Preferably, the ultrasonic generator is fixed at the center of the liquid storage space and is in close contact with the polishing disc.

[0020] Preferably, the ultrasonic generator produces ultrasonic waves with a frequency ≥20kHz.

[0021] Preferably, the number of polishing head assemblies is at least one.

[0022] Secondly, the present invention provides a polishing method for high-hardness semiconductor materials, which is based on the chemical mechanical polishing apparatus described above, and includes the following steps:

[0023] (S.1) Fix the workpiece to be polished at the bottom of the fixing device of the polishing head assembly;

[0024] (S.2) Polishing fluid is delivered to the storage space via a polishing fluid delivery device;

[0025] (S.3) Start the pressing device and ultrasonic generator so that the lower surface of the workpiece to be polished rubs against the polishing disc under ultrasonic and rotational conditions, thereby achieving grinding and polishing.

[0026] Preferably, the workpiece material to be polished is silicon carbide or gallium nitride.

[0027] Preferably, the polishing temperature in step (3) is 30-40℃.

[0028] Therefore, the present invention has the following beneficial effects:

[0029] This invention introduces an ultrasonic generator into a chemical mechanical polishing (CMP) apparatus, thereby enhancing the activity and mechanical energy of the abrasive in the polishing slurry during the CMP process. This further improves the abrasive's grinding ability on the workpiece being polished, resulting in a significant increase in polishing efficiency for high-hardness semiconductor materials and a substantial reduction in processing time. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of one structure of the present invention.

[0031] Figure 2This is a cross-sectional structural diagram of the present invention.

[0032] Figure 3 For the present invention Figure 2 Enlarged view of the structure at point a.

[0033] Figure 4 This is a schematic diagram of the polishing head assembly of the present invention.

[0034] Figure 5 This is a top view of the present invention.

[0035] Among them: polishing platform 100, polishing disc 110, polishing pad 111, enclosure device 120, liquid outlet 121, liquid storage space 130, ultrasonic generator 140, polishing head assembly 200, fixing device 210, pressing device 220, and polishing liquid delivery device 300. Detailed Implementation

[0036] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. Those skilled in the art will be able to implement the present invention based on these descriptions. Furthermore, the embodiments of the present invention described below are generally only some, not all, of the embodiments of the present invention. Therefore, all other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort should fall within the scope of protection of the present invention.

[0037] Example 1

[0038] like Figures 1-4 As shown, this embodiment provides a chemical mechanical polishing apparatus, which includes a polishing platform 100, on the upper surface of which a polishing disc 110 is disposed. The upper surface of the polishing disc 110 is provided with a polishing pad 111 for polishing the workpiece to be polished. The polishing pad 111 is detachably connected to the polishing disc 110, therefore, polishing pads 111 of different materials and hardness can be selected and used at different stages of the polishing process, thereby meeting the polishing requirements of workpieces with different needs. During the polishing process, the polishing pad 111 can absorb the polishing liquid delivered from the external polishing liquid delivery device 300. The abrasive in the polishing liquid can adhere to the surface pores of the polishing pad 111. The polishing liquid usually also contains oxidants and catalysts, which can catalyze the oxidation of the surface of the workpiece to be polished, thereby forming a soft oxide layer on the surface of the workpiece. When the workpiece to be polished rotates relative to the polishing pad 111, the oxide layer on the surface of the workpiece to be polished will be ground away by the polishing pad 111 and the abrasive adsorbed in the polishing pad 111, exposing the surface of the workpiece again. Then, a chemical reaction is carried out. In this way, the workpiece surface polishing is completed through the alternation of chemical and mechanical processes.

[0039] In this embodiment, the outer side of the polishing platform 100 is provided with a surrounding device 120 around the outer periphery of the polishing disc 110, so that the interior of the surrounding device 120 forms a liquid storage space 130 capable of storing polishing liquid. Therefore, when the workpiece to be polished is in contact with the polishing pad 111, the contact surface can always be below the liquid level of the polishing liquid, ensuring the redox effect of the polishing liquid on the workpiece to be polished.

[0040] In addition, since the polishing liquid is continuously introduced into the interior of the liquid storage space 130 during polishing, in order to maintain the liquid level of the polishing liquid in the interior of the liquid storage space 130 at a suitable value, the embodiment is further provided with liquid outlets 121 for flowing out the polishing liquid at the side wall of the surrounding device 120, the number of which is at least 2. Optionally, the number of liquid outlets 121 can be 2 / 3 / 4 / 5 / 6 / 7 / 8, as long as the liquid outlets 121 are uniformly distributed at the side wall of the surrounding device 120. During the continuous introduction and outflow of the polishing liquid, the products formed by polishing the workpiece to be polished will flow out with the polishing liquid, thereby preventing these products from affecting the polishing effect.

[0041] In addition, in order to further enhance the grinding effect of the abrasive in the polishing liquid on the workpiece to be polished, the present application further provides an ultrasonic generator 140 on the polishing platform 100 for generating ultrasonic waves in the interior of the liquid storage space 130. The ultrasonic generator 140 can be installed at the center of the liquid storage space 130. When polishing is performed, the ultrasonic generator 140 is turned on to emit ultrasonic waves in the polishing liquid in the liquid storage space 130. Since the ultrasonic waves can excite the abrasive in the polishing liquid to vibrate, the energy in the ultrasonic waves is converted into mechanical energy of the abrasive, thereby effectively enhancing the grinding ability of the abrasive on the workpiece to be polished. For high-hardness semiconductor materials such as silicon carbide and gallium nitride, which are originally difficult to polish, the polishing efficiency is greatly improved, and the processing time for high-hardness semiconductor materials is greatly shortened.

[0042] In this embodiment, the polishing head assembly 200 further includes a fixing device 210 for fixing the workpiece to be polished. The connection between the fixing device 210 and the workpiece to be polished can be any one of vacuum adsorption, bonding or mechanical clamping, so that the workpiece to be polished does not fall off during polishing. The polishing head assembly 200 further includes a pressing device 220, which can apply a certain pressing force and rotational force to the workpiece to be polished during the polishing process, so that relative rotation is formed between the workpiece to be polished and the polishing pad 111, thereby realizing the grinding and polishing process of the workpiece to be polished. In order to improve the grinding efficiency of the workpiece to be polished, the pressing device 220 can be a motor-driven device, which can be controlled by a computer to rotate at a certain speed and apply a certain pressing force to the workpiece to be polished. Figure 5As shown, in this embodiment, a plurality of polishing head assemblies 200 can be arranged above the polishing platform 100, so that a plurality of components to be polished can be polished simultaneously.

[0043] Embodiment 2

[0044] A high-hardness semiconductor material polishing method based on the chemical mechanical polishing device of embodiment 1, comprising the following steps:

[0045] S.1 Fixing a high-hardness semiconductor substrate such as a silicon carbide substrate or a gallium nitride substrate at the bottom of the fixing device 210 of the polishing head assembly 200.

[0046] S.2 Delivering polishing liquid with a temperature of 30-40℃ to the liquid storage space 130 through the polishing liquid delivery device 300, the inflow of the polishing liquid is 8-10L, and the outflow of the polishing liquid is also 8-10L, so that the inflow and outflow are kept consistent, and about 10-30L of polishing liquid is stored in the liquid storage space 130, while ensuring that the liquid level of the polishing liquid does not submerge the fixing device 210.

[0047] S.3 Starting the pressing device 220 to make the substrate and the polishing pad 111 rotate relatively, so that the abrasive in the polishing liquid can grind the substrate, and starting the ultrasonic generator 140 to generate ultrasonic waves with a frequency of ≥20KHz, and different ultrasonic generator frequencies can be selected according to different polishing progress, for example, a lower frequency ultrasonic wave (20-40Hz) can be selected in the early stage of polishing, and the ultrasonic frequency can be appropriately increased to medium frequency (40-150Hz) or high frequency (≥150Hz) as the polishing proceeds. The ultrasonic wave can excite the abrasive in the polishing liquid to vibrate, so that the energy in the ultrasonic wave is converted into mechanical energy of the abrasive, thereby effectively improving the grinding ability of the abrasive on the workpiece to be polished, and achieving polishing.

Claims

1. A chemical mechanical polishing apparatus, characterized in that, The system includes a polishing platform (100) with a polishing disc (110) on its upper surface. A baffle device (120) is provided around the outer periphery of the polishing disc (110) of the polishing platform (100), forming a storage space (130) inside the baffle device (120) for accumulating polishing fluid. An outlet (121) for discharging polishing fluid is provided on the side wall of the baffle device (120), and the number of the outlets (121) is at least two, which are evenly distributed on the side wall of the baffle device (120). At the polishing platform (100), an ultrasonic generator (140) for generating ultrasonic waves inside the liquid storage space (130) is provided. The ultrasonic generator (140) is fixed at the center of the liquid storage space (130) and is in close contact with the upper surface of the polishing disk (110). The ultrasonic generator (140) emits ultrasonic waves with an ultrasonic emission frequency ≥20KHz to the polishing liquid stored in the liquid storage space (130), thereby converting the energy in the ultrasonic waves into the mechanical energy of the abrasive in the polishing liquid. The polishing head assembly (200) includes a fixing device (210) for fixing the workpiece to be polished and a pressing device (220) for applying pressure to the polishing substrate and generating rotation. Polishing fluid delivery device (300) for delivering polishing fluid into the storage space (130).

2. The chemical mechanical polishing apparatus according to claim 1, characterized in that, The upper surface of the polishing disk (110) is detachably provided with a polishing pad (111) for polishing the silicon carbide substrate.

3. The chemical mechanical polishing apparatus according to claim 1, characterized in that, The number of polishing head assemblies (200) is at least one.

4. A polishing method for high-hardness semiconductor materials, characterized in that, Based on the chemical mechanical polishing apparatus according to any one of claims 1 to 3, it includes the following steps: (S.1) Fix the workpiece to be polished to the bottom of the fixing device (210) of the polishing head assembly (200); (S.2) Polishing fluid is supplied to the storage space (130) via the polishing fluid delivery device (300); (S.3) Start the pressing device (220) and the ultrasonic generator (140) so that the lower surface of the workpiece to be polished rubs against the polishing disc (110) under ultrasonic and rotational conditions, thereby achieving grinding and polishing.

5. The polishing method for high-hardness semiconductor materials according to claim 4, characterized in that, The workpiece material to be polished is silicon carbide or gallium nitride.

6. The polishing method for high-hardness semiconductor materials according to claim 4, characterized in that, The polishing temperature in step (3) is 30-40℃.

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