Chemical mechanical polishing solution

Abstract

This invention aims to provide a chemical mechanical polishing (CMP) slurry for polyimide (PI) materials. The CMP slurry uses alumina abrasive, and by adjusting the pH, it can achieve a high PI removal rate while simultaneously reducing the surface roughness of the PI after polishing.

Description

Technical Field

[0001] This invention relates to a chemical mechanical polishing fluid, and more particularly to a chemical mechanical polishing fluid for polyimide materials. Background Technology

[0002] With the continuous development of semiconductor technology and the increasing number of interconnect layers in large-scale integrated circuits, the planarization technology of conductive and insulating dielectric layers has become particularly critical.

[0003] With the continuous development of semiconductor technology, traditional monolithic integrated circuit manufacturing processes are gradually approaching their physical limits. To further improve chip performance and integration density, heterogeneous integration technology has become an important research direction. By flexibly modularizing and integrating chips of different sizes, functions, and types in three dimensions, the limitations of monolithic integrated circuits can be overcome, extending Moore's Law. Furthermore, high-performance computing, artificial intelligence, and smart terminals are placing increasingly higher demands on chip performance and integration density. Through high-density interconnect heterogeneous chip stacking manufacturing processes, chips with different functions can be heterogeneously integrated into a single package, thereby improving bandwidth, power efficiency, and reducing latency, meeting the needs of these fields for high-performance, small-size chips.

[0004] Polyimide (PI) is widely used in high-density interconnect heterogeneous chip stacks due to its excellent heat resistance, chemical resistance, insulation properties, and mechanical properties. 1) In high-density interconnect heterogeneous chip stacks, polyimide can be used as a dielectric layer, providing excellent electrical isolation and mechanical support. Its high dielectric constant and impedance characteristics help reduce signal loss and interference, improving chip performance and stability. 2) Polyimide can be used to manufacture chip packaging layers, protecting the internal structure of the chip from damage by the external environment. Its heat resistance and chemical stability allow the chip to maintain stable performance in harsh operating environments. 3) During chip stacking, polyimide can act as a buffer layer to reduce thermal and mechanical stress between different materials. This helps prevent chip damage or performance degradation due to stress concentration. 4) Polyimide can also be used to manufacture interconnects, lead frames, and other components of the chip, providing reliable electrical connections and mechanical support. 5) In some cases, polyimide can also be used as a photoresist for fabricating microstructures and patterns. Therefore, due to its wide range of applications and mature preparation process, polyimide has become one of the important materials in this field.

[0005] In practical applications, a high degree of surface flatness is required for PI (polyimide) materials, necessitating planarization through chemical mechanical polishing (CMP). CMP is considered the most effective method for global planarization. CMP involves chemical, mechanical, and combined actions. It typically consists of a polishing table with a polishing pad and a polishing head to hold the chip. The polishing head holds the chip in place, pressing the front side of the chip onto the polishing pad. During CMP, the polishing head moves linearly across the polishing pad or rotates in the same direction as the polishing table. Simultaneously, a slurry containing an abrasive is dripped onto the polishing pad and spreads out due to centrifugal force. The chip surface achieves global planarization through the combined mechanical and chemical action.

[0006] To meet the requirements of high-density interconnect heterogeneous chip stacking manufacturing processes, it is necessary to develop chemical mechanical polishing (CMP) slurries for PI (polyimide). However, because PI material is very stable at room temperature, does not readily undergo chemical reactions, and has high mechanical strength, commonly used CMP slurries struggle to achieve high polishing speeds when polishing PI. Using silicon oxide as the abrasive results in a very low PI removal rate. While using alpha-alumina, with its higher mechanical strength, can improve the PI removal rate, it often leads to noticeable scratches on the polished PI surface. Therefore, it is necessary to develop novel PI CMP slurries that maintain high-speed PI removal while ensuring no significant scratches on the polished PI surface. Summary of the Invention

[0007] To overcome the above-mentioned technical defects, the present invention provides a chemical mechanical polishing fluid, comprising: alumina abrasive, wherein the alumina abrasive is mixed in the chemical mechanical polishing fluid to form a composition, wherein the alumina is one or more of δ-phase alumina, γ-phase alumina, and θ-phase alumina.

[0008] Furthermore, the mass percentage concentration of the abrasive is 0.5% to 10%.

[0009] Furthermore, the particle size range of the abrasive is 50–300 nm.

[0010] Furthermore, the pH value of the chemical mechanical polishing solution is 4 to 8.

[0011] The polishing liquid of the present invention may also include other commonly used additives such as pH adjusters, viscosity adjusters, and defoamers to achieve the polishing effect.

[0012] The polishing solution of the present invention can be concentrated and diluted with deionized water to the concentration range of the present invention before use.

[0013] Compared with existing technologies, the above technical solution has the following advantages:

[0014] 1. This invention achieves a higher polyimide removal rate and a better polished surface by selecting appropriate abrasives.

[0015] 2. By selecting a suitable pH, this invention achieves a higher polyimide removal rate and a better polished surface. Attached Figure Description

[0016] Figure 1 The surface roughness of the polished PI surface, 0.3 nm, is shown in a specific embodiment of the present invention. Detailed Implementation

[0017] The advantages of the present invention will be described in detail below with reference to specific embodiments.

[0018] Prepare the polishing solutions of Comparative Examples 1-4 and Examples 1-9 of this application according to the formulas given in Table 1, and then adjust the polishing solution to the required pH value using KOH or HNO3.

[0019] Table 1. Composition, content, and pH of polishing solutions for Comparative Examples 1-4 and Examples 1-9

[0020]

[0021] The polishing slurries used in Comparative Examples 1-4 and Examples 1-9 were used to polish empty PI wafers under the following conditions: Specific polishing conditions: Mirra Mesa polishing machine, IC1010 polishing pad, 200mm wafer, polishing pressure 3.0 psi, polishing disk speed 93 rpm, polishing head speed 87 rpm, polishing slurry flow rate 150 ml / min, and polishing time 1 min. The surface roughness of the polished PI wafers was measured using an XE-300P atomic force microscope. The PI polishing rate and surface roughness results are listed in Table 2.

[0022] Table 2 shows the polishing effect data for Comparative Examples 1-4 and Examples 1-9.

[0023]

[0024] As shown in Table 2, Comparative Example 1 used silica as the abrasive, which resulted in a low PI removal rate; Comparative Example 2 used α-phase alumina as the abrasive, which resulted in a high PI removal rate, but the surface roughness of the PI after polishing was very high. Neither of these can meet the requirements of practical applications.

[0025] Comparative Example 3 used γ-phase alumina as the abrasive, but did not select a suitable pH, resulting in a low PI removal rate. Compared with Comparative Example 3, Example 1 not only used γ-phase alumina as the abrasive, but also selected a suitable pH, thus achieving a higher PI removal rate while ensuring low PI surface roughness after polishing.

[0026] Comparative Example 4 used a mixture of δ, γ, and θ phases of alumina as the abrasive, but the particle size was too large, resulting in poor PI surface roughness after polishing. Compared with Comparative Example 4, Example 4 used a suitable particle size, which not only achieved a higher PI removal rate but also ensured low PI surface roughness after polishing.

[0027] The polishing fluids of Examples 1-9 of the present invention use one or more of δ-phase alumina, γ-phase alumina, and θ-phase alumina as abrasives, and adjust the pH appropriately to achieve a high PI removal rate while ensuring low PI surface roughness after polishing.

[0028] It should be noted that the embodiments of the present invention have better implementability and are not intended to limit the present invention in any way. Any person skilled in the art may use the above-disclosed technical content to change or modify it into equivalent effective embodiments. However, any modifications or equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention shall still fall within the scope of the technical solution of the present invention.

Claims

1. A chemical mechanical polishing slurry, characterized in that, include: Alumina abrasive, wherein the alumina abrasive is mixed in a chemical mechanical polishing fluid to form a composition, wherein the alumina is one or more of δ-phase alumina, γ-phase alumina, and θ-phase alumina.

2. The polishing slurry as described in claim 1, characterized in that, The mass percentage concentration of the abrasive is 0.5% to 10%.

3. The polishing slurry as described in claim 1, characterized in that, The particle size range of the abrasive is 50–300 nm.

4. The polishing slurry as described in claim 1, characterized in that, The pH value of the chemical mechanical polishing fluid is 4 to 8.

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