A polishing composition and its use for removing titanium nitride layers on semiconductor chips

Abstract

This invention discloses a polishing composition and its application in removing titanium nitride layers from semiconductor chips. The polishing composition comprises the following components in parts by weight: 100 parts water, 3-10 parts titanium nitride, and 3-10 parts metal oxide. This invention provides a polishing composition mainly composed of water, titanium nitride, and metal oxide. By using a polishing slurry made of particles of the same material as the sample being polished, the affinity between the slurry and the sample can be ensured, thereby improving polishing efficiency and uniformity, and achieving uniform removal of nanoscale-thick titanium nitride layers. Compared to current acid-based methods of corroding titanium nitride layers, the water-based polishing slurry of this invention does not cause uneven corrosion, thus achieving uniform removal of nanoscale-thick titanium nitride layers from a single chip.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor materials technology, specifically relating to a polishing composition and its application in removing titanium nitride layers from semiconductor chips. Background Technology

[0002] In the manufacturing and processing of integrated circuit chips, aluminum-processed chips are widely used in various electronic devices due to their excellent conductivity and high-temperature resistance. Titanium nitride and silicon dioxide are often used as barrier layers and oxide layers, respectively, in aluminum-processed chips. However, when performing reverse engineering and failure analysis on these individual aluminum-processed chips, it is necessary to manually dissect and expose each chip layer by layer according to different materials to facilitate in-depth research and analysis of the chip's internal structure and material properties.

[0003] In existing technologies, the removal of the titanium nitride layer beneath the metal layer typically employs chemical etching. Specifically, phosphoric acid of appropriate concentration is used for chemical etching under specific conditions. However, existing techniques often encounter several problems when removing the titanium nitride layer. First, the thickness of the titanium nitride layer is usually on the nanometer scale, making the removal process extremely difficult and complex. Existing chemical etching methods cannot guarantee uniformity when removing nanometer-thick titanium nitride layers, often resulting in over-etching. This leads to inconsistent thickness of the underlying silica layer, affecting subsequent analytical results. Second, the etching solution often seeps into the next layer through interlayer silicon vias, causing premature etching of the underlying metal, affecting reverse engineering and failure analysis results. Therefore, achieving uniform removal of nanometer-thick titanium nitride layers on a single chip while ensuring consistent thickness of the underlying silica layer is a significant challenge currently facing the technology. Summary of the Invention

[0004] To overcome the problems existing in the prior art, one objective of the present invention is to provide a polishing composition. A second objective of the present invention is to provide a method for preparing the aforementioned polishing composition. A third objective of the present invention is to provide a method for removing the titanium nitride layer from a semiconductor chip. To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0005] The first aspect of the present invention provides a grinding composition comprising the following components in parts by weight: 100 parts water, 3-10 parts titanium nitride, and 3-10 parts metal oxide.

[0006] Preferably, the metal oxide is selected from at least one of cerium oxide, silicon dioxide, aluminum oxide, germanium oxide, and zirconium oxide.

[0007] More preferably, it comprises the following components in parts by weight: 100 parts water, 3-7 parts titanium nitride, and 3-7 parts silicon dioxide.

[0008] More preferably, it comprises the following components in parts by weight: 100 parts water, 4-6 parts titanium nitride, and 4-6 parts silicon dioxide.

[0009] Preferably, the titanium nitride is in powder form with a particle size of 0.1-1 μm.

[0010] More preferably, the powder particle size is 0.3-0.7 μm.

[0011] Preferably, the grinding composition is prepared by a method comprising the following steps: adding titanium nitride and metal oxide to water and mixing to obtain the grinding composition.

[0012] A second aspect of the invention provides the application of the polishing composition described in the first aspect in removing titanium nitride layers from semiconductor chips.

[0013] A third aspect of the present invention provides a method for removing a titanium nitride layer from a semiconductor chip, comprising the steps of: adding the polishing composition described in the first aspect to an polishing cloth, and polishing the titanium nitride layer on the semiconductor chip using the polishing cloth.

[0014] Preferably, the grinding time is 1-10 minutes.

[0015] Preferably, the abrasive cloth is an abrasive felt cloth, and the pile length of the abrasive felt cloth is 0.2-2μm.

[0016] More preferably, the pile length is 0.5-1.5μm.

[0017] This invention utilizes micron-length abrasive cloths for nano-thickness titanium nitride layers: by using micron-length abrasive cloths, nano-thickness titanium nitride layers can be effectively removed while avoiding damage to the underlying silicon dioxide layer, ensuring the thickness consistency of the underlying silicon dioxide layer.

[0018] Preferably, the thickness of the titanium nitride layer is 100 nm.

[0019] Preferably, the semiconductor chip includes a metal top layer, a titanium nitride barrier layer, an oxide layer, and a semiconductor layer disposed sequentially.

[0020] More preferably, the semiconductor chip includes a top layer of aluminum metal, a titanium nitride barrier layer, a silicon dioxide oxide layer, and a semiconductor layer disposed sequentially.

[0021] Preferably, the grinding step specifically includes: pressing the abrasive cloth onto the surface of the titanium nitride layer and grinding in a double twisted path.

[0022] More preferably, the semiconductor chip is rotated at regular intervals during the grinding process.

[0023] This invention employs a double-twisted path (∞ shape) and a timed rotation of the sample at a fixed angle to ensure the uniformity of the titanium nitride layer in all directions when grinding force is applied. This grinding movement path and timed rotation angle make the removal process of the titanium nitride layer more uniform and consistent, avoiding excessive local friction and thus reducing damage to the chip structure caused by excessive grinding in individual locations. This achieves uniform removal of the nanoscale thickness of the titanium nitride layer and consistency in the thickness of the underlying silicon dioxide layer.

[0024] The beneficial effects of this invention are:

[0025] (1) The present invention provides a grinding composition, mainly composed of water, titanium nitride and metal oxide. By using a grinding fluid made of particles of the same material as the sample being ground, the affinity between the grinding fluid and the sample being ground can be ensured, thereby improving the grinding efficiency and uniformity, and achieving uniform removal of a nano-thickness titanium nitride layer. Compared with the current acid reaction to eliminate the corrosion of titanium nitride layer, the grinding fluid of the present invention uses water and will not cause uneven corrosion, thereby achieving uniform removal of a nano-thickness titanium nitride layer on a single chip.

[0026] (2) This invention provides a method for removing titanium nitride layers from semiconductor chips. The method involves applying the aforementioned polishing composition to an polishing cloth and then manually polishing the material. Compared to chemical removal, this method is more precise and controllable, eliminating the need for high-precision equipment and expensive polishing materials. This significantly reduces the complexity and cost of the entire process. Furthermore, this invention offers high efficiency and precision for removing nanoscale thickness titanium nitride layers, and is expected to play a significant role in the fields of semiconductor material surface treatment technology and nanotechnology. Attached Figure Description

[0027] Figure 1 An overview photograph of the top layer of metal beneath the passivation layer;

[0028] Figure 2 An overview photograph of the TiN layer beneath the top metal layer;

[0029] Figure 3 This is a microscope image of the chip structure after processing in Example 1;

[0030] Figure 4 This is a microscope image of the chip structure after processing, as shown in Comparative Example 1. Detailed Implementation

[0031] The present invention will be further described in detail below through specific embodiments. Unless otherwise specified, the raw materials used in the following embodiments can be obtained from conventional commercial sources or prepared and isolated through simple synthesis; unless otherwise specified, the processes employed are conventional processes in the art.

[0032] Example 1

[0033] This embodiment provides a polishing composition and its application method in removing titanium nitride layers from semiconductor chips. The specific steps are as follows:

[0034] Step 1: Prepare a single sample to be ground. This sample is an aluminum-processed chip (such as a common LED driver chip or a microcontroller MCU chip), and its titanium nitride layer is about 100nm thick.

[0035] Step 2: Prepare the grinding slurry, which consists of 100 parts water, 5 parts titanium nitride, and 5 parts silicon dioxide by mass ratio, wherein both titanium nitride and silicon dioxide are particles with a diameter of 0.5 μm.

[0036] Step 3: Select a micron-length abrasive cloth with a pile length of 1μm, and pour the abrasive liquid onto the abrasive cloth.

[0037] Step 4: Set the grinding movement path, using a double zigzag path to ensure uniformity of grinding at each position on the chip.

[0038] Step 5: Begin grinding. Press the grinding cloth with the side containing the grinding fluid onto the surface of the titanium nitride layer. The grinding fluid should be between the titanium nitride layer and the cloth. Ensure that the cloth is rotated at a fixed angle (e.g., 45°) for a period of time during grinding.

[0039] Step Six: Repeat steps four and five above for 5 minutes, then inspect under a microscope to ensure the titanium nitride layer is completely removed. These steps achieve uniform removal of the nano-thickness titanium nitride layer while ensuring the consistent thickness of the underlying silicon dioxide layer.

[0040] Comparative Example 1

[0041] This comparative example provides a polishing composition and its application in removing titanium nitride layers from semiconductor chips. The specific steps are as follows:

[0042] Step 1: Prepare a single sample to be ground. The sample is an aluminum process chip (using the same batch of aluminum process chips as in Example 1), and the thickness of its titanium nitride layer is about 100nm.

[0043] Step 2: Prepare the grinding slurry, which consists of 100 parts water, 5 parts alumina, and 5 parts silica by mass ratio, wherein both alumina and silica are particles with a particle size of 0.5 μm.

[0044] Step 3: Select a micron-length abrasive cloth with a pile length of 1μm, and pour the abrasive liquid onto the abrasive cloth.

[0045] Step 4: Set the grinding movement path, using a double zigzag path to ensure uniformity of grinding at each position on the chip.

[0046] Step 5: Begin grinding. Press the grinding cloth with the side containing the grinding fluid onto the surface of the titanium nitride layer. The grinding fluid should be between the titanium nitride layer and the cloth. Ensure that the cloth is rotated at a fixed angle (e.g., 45°) for a period of time during grinding.

[0047] Step Six: Repeat steps four and five above to continue grinding, keeping the grinding process (time, intensity, etc.) consistent with Example 1.

[0048] Semiconductor chip characterization

[0049] Microscopic analysis was used to examine the exposure of each layer, including the exposure of the top metal layer beneath the passivation layer. Figure 1 As shown, the exposed TiN layer beneath the top metal layer is as follows: Figure 2 As shown, the exposure after grinding to remove the TiN layer in Example 1 is as follows. Figure 3 As shown, the exposure after grinding to remove the TiN layer in Comparative Example 1 is as follows: Figure 4 As shown, from Figure 2 and Figure 3 Comparative analysis shows that the polishing slurry of Example 1 can achieve uniform removal of nano-thickness titanium nitride layers, and the removal process using manual polishing is more precise and controllable compared to chemical removal; from Figure 3 and Figure 4 Comparative analysis shows that using alumina as the main material of the polishing slurry cannot effectively remove the titanium nitride layer.

[0050] In summary, this invention provides a grinding composition mainly composed of water, titanium nitride, and metal oxides. By using a grinding fluid made of particles of the same material as the sample being ground, the affinity between the grinding fluid and the sample can be ensured, thereby improving grinding efficiency and uniformity. This achieves uniform removal of nanoscale-thick titanium nitride layers. Compared to current acid-based methods that corrode titanium nitride layers, the water-based grinding fluid of this invention does not cause uneven corrosion, thus achieving uniform removal of nanoscale-thick titanium nitride layers on a single chip.

[0051] This invention provides a method for removing titanium nitride layers from semiconductor chips. The method involves applying the aforementioned polishing composition to an polishing cloth and then manually polishing the material. Compared to chemical removal, this method offers greater precision and control, eliminating the need for high-precision equipment and expensive polishing materials. This significantly reduces the complexity and cost of the entire process. Furthermore, this invention offers high efficiency and precision for removing nanoscale thickness titanium nitride layers, and is expected to play a significant role in the fields of semiconductor material surface treatment and nanotechnology.

[0052] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A method for removing titanium nitride layer from a semiconductor chip, characterized in that, The process includes the following steps: adding an abrasive composition to an abrasive cloth, and using the abrasive cloth to abrade and remove the titanium nitride layer on a semiconductor chip; The grinding composition comprises the following components in parts by weight: 100 parts water, 3-7 parts titanium nitride, and 3-7 parts silicon dioxide; The titanium nitride is in powder form with a particle size of 0.1-1 μm; The abrasive cloth is an abrasive velvet cloth with a pile length of 0.2-2 μm; The grinding steps specifically include: pressing the grinding cloth onto the surface of the titanium nitride layer and grinding it in a double twisted wire path, while rotating the semiconductor chip at regular intervals during the grinding process.

2. The method for removing titanium nitride layer from a semiconductor chip according to claim 1, characterized in that, The grinding time is 1-10 minutes.

3. The method for removing the titanium nitride layer from a semiconductor chip according to claim 1, characterized in that, The thickness of the titanium nitride layer is 100 nm.

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