Polishing composition

Abstract

This polishing composition contains abrasive grains, an amine compound, and water. The amine compound is at least one of 1,3-diaminopropane and 1,4-diaminobutane.

Description

polishing composition CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority from Japanese Patent Application No. 2023-213513, the disclosure of which is incorporated herein by reference.

[0002] The present invention relates to a polishing composition.

[0003] Chemical mechanical polishing (hereinafter referred to as CMP) has been conventionally used in the manufacture of semiconductor devices. In the manufacture of semiconductor devices with increasingly high performance in recent years, various objects are expected to be polished. Therefore, polishing compositions are also required to have polishing performance suited to the situation.

[0004] For example, the polishing composition of Patent Document 1 is intended for polishing to expose copper electrodes embedded in a silicon layer, and contains, in addition to abrasive grains, an alkaline compound such as a diamine and an oxidizing agent such as sodium chlorite. Patent Document 1 shows that by using this polishing composition, silicon layers and copper layers can be polished at approximately the same polishing rate.

[0005] The polishing composition of Patent Document 2 is applicable to shallow trench isolation (STI) in the front end of line (FEOL) process, and is intended to selectively polish a silicon oxide layer over a silicon nitride layer. Patent Document 2 shows that the above object can be achieved by using a polishing composition in which a core-shell structure is formed in colloidal silica using a substance obtained by hydrolyzing aminosilane.

[0006] Japanese Patent Publication No. 2011-66383 Japanese Special Publication No. 2017-525793

[0007] In recent highly functional semiconductor devices, CMP may be required to polish not only a silicon oxide layer or a silicon nitride layer but also a silicon layer such as a polysilicon layer.

[0008] For example, in forming a gate structure of a field-effect transistor such as a GAA, an insulating layer that serves as an insulating partition for the gate electrode is formed, followed by forming a recess in the insulating layer for forming the gate electrode. The recess is filled with polysilicon, and a polysilicon deposition layer is then formed on the insulating layer. CMP is then performed to planarize the exposed surface of the gate electrode and the insulating layer while removing the silicon deposition layer. Furthermore, in forming such a gate structure, a protective layer called a cap layer may be formed between the insulating layer and the deposition layer. The cap layer is made of either silicon oxide or silicon nitride, but is a different material from the insulating layer. CMP is then performed to planarize or remove the cap layer while removing the silicon deposition layer.

[0009] As shown in the above example, it is expected that the polishing amount will be relatively large when polishing a deposition layer. Therefore, in this situation, it is efficient to use a polishing composition with an increased polishing rate for silicon. On the other hand, it is expected that the polishing amount will be relatively small when polishing an insulating layer or a cap layer. Therefore, in this situation, from the viewpoint of polishing control, a polishing composition that can exhibit an appropriate polishing rate corresponding to a small polishing amount is desired rather than a polishing composition with an excessively increased polishing rate for silicon oxide or silicon nitride. Note that this situation can be expected not only in the formation of a gate structure of a field effect transistor, but also in other CMP in the manufacture of semiconductor devices.

[0010] In view of the above circumstances, an object of the present invention is to provide a polishing composition that has polishing performance for a silicon layer and polishing performance for at least one of a silicon oxide layer and a silicon nitride layer, and that can highly selectively polish a silicon layer relative to at least one of a silicon oxide layer and a silicon nitride layer.

[0011] The polishing composition according to the present invention comprises abrasive grains, an amine compound, and water, and the amine compound is at least one of 1,3-diaminopropane and 1,4-diaminobutane.

[0012] In addition, in the polishing composition according to one aspect of the present invention, the content of the amine compound is preferably 0.01% by mass or more and 1% by mass or less.

[0013] Furthermore, the polishing composition according to one embodiment of the present invention does not contain any chelating agent or oxidizing agent other than the amine compound.

[0014] As described above, the present invention can provide a polishing composition that has polishing performance for a silicon layer and polishing performance for at least one of a silicon oxide layer and a silicon nitride layer, and that can highly selectively polish a silicon layer relative to at least one of a silicon oxide layer and a silicon nitride layer.

[0015] 1 is a schematic cross-sectional view showing an example of an object to be polished to which the polishing composition of the present invention can be applied, and FIG. 2 is a schematic cross-sectional view showing another example of an object to be polished to which the polishing composition of the present invention can be applied.

[0016] The polishing composition according to an embodiment of the present invention will be described below.

[0017] The polishing composition of this embodiment contains abrasive grains, an amine compound, water, and any additives. The polishing composition of this embodiment is a polishing slurry in which abrasive grains are dispersed in water.

[0018] Examples of particles constituting the abrasive grains include inorganic particles, organic particles, and organic-inorganic composite particles. Examples of inorganic particles include silica particles, alumina particles, titania particles, zirconia particles, ceria particles, and calcium carbonate particles. Examples of silica particles include fumed silica particles, colloidal silica particles, and silica particles obtained by the sol-gel method. Examples of organic particles include organic polymer particles such as polyethylene, polypropylene, poly-1-butene, poly-4-methyl-1-pentene, olefin copolymers, polystyrene, styrene copolymers, polyvinyl chloride, polyacetal, saturated polyesters, polyamides, polycarbonates, phenoxy resins, polymethyl methacrylate, (meth)acrylic resins, and acrylic copolymers. Examples of organic-inorganic composite particles include particles obtained by polycondensation of metal or silicon alkoxide compounds (e.g., alkoxysilanes, aluminum alkoxides, titanium alkoxides, etc.) in the presence of organic particles. The abrasive grains may be composed of only one of these materials, or two or more of these materials.

[0019] The secondary particle diameter of the abrasive grains measured by dynamic light scattering is preferably 500 nm or less, and is, for example, 10 nm or more.

[0020] The content of the abrasive grains is more preferably 0.1 mass % or more and 5.0 mass % or less, and even more preferably 0.3 mass % or more and 2.5 mass % or less, based on the mass of the polishing composition.

[0021] The amine compound is at least one of 1,3-diaminopropane and 1,4-diaminobutane, that is, the polishing composition may contain only one of these amine compounds or may contain both of them.

[0022] The content of the amine compound is preferably 0.01 mass % or more, more preferably 0.02 mass % to 1 mass % or less, and even more preferably 0.05 mass % or more, based on the mass of the polishing composition. The content of the amine compound is preferably 1 mass % or less.

[0023] More specifically, when the amine compound is 1,3-diaminopropane, the content is preferably 0.01% by mass or more. This allows the polysilicon layer to be polished at a high polishing rate, and the silicon oxide layer and silicon nitride layer to be polished at an appropriate polishing rate that is lower than the polishing rate for the polysilicon layer. Furthermore, the silicon oxide layer and the silicon nitride layer can be polished at approximately the same polishing rate.

[0024] When the amine compound is 1,4-diaminobutane, the content is preferably 0.01% by mass or more and 1% by mass or less.

[0025] The mass ratio of the amine compound to the abrasive grains (content of the abrasive grains:content of the amine compound) is preferably 1:0.01 to 1:20, more preferably 1:0.01 to 1:15, and even more preferably 1:0.01 to 1:5.

[0026] The water is preferably purified water such as distilled water or ion-exchanged water. The content of the water is preferably 90% by mass or more, more preferably 95% by mass or more, and even more preferably 98% by mass or more, based on the mass of the polishing composition.

[0027] The additives include water-soluble polymers. Examples of the water-soluble polymers include celluloses such as hydroxyethyl cellulose, hydroxyethyl methyl cellulose, hydroxypropyl cellulose, carboxymethyl cellulose, cellulose acetate, and methyl cellulose, vinyl polymers such as polyvinyl alcohol, modified PVA (polyvinyl alcohol derivative), and polyvinylpyrrolidone, glycosides, and polyhydric alcohols. Examples of the glycosides include alkylene oxide derivatives of methyl glucoside such as polyoxyethylene methyl glucoside and polyoxypropylene methyl glucoside.

[0028] The polishing composition preferably does not contain any additives other than the additives described above. Examples of such additives include chelating agents other than the amine compounds, such as glycine, oxidizing agents, such as hydrogen peroxide, and antifoaming agents, such as silicone emulsion. The total content of these additives is preferably 1% by mass or less, more preferably 0.5% by mass or less, and even more preferably 0.1% by mass or less, based on the mass of the polishing composition. In particular, the content of each of the chelating agent and the oxidizing agent is preferably 1% by mass or less, more preferably 0.5% by mass or less, and more preferably 0.1% by mass or less.

[0029] The pH of the polishing composition is preferably 8 to 12, and may be 8 to 11.

[0030] When the polishing composition contains 1,3-diaminopropane, it can polish a silicon layer at 3500 Å / min or more, and polish a silicon oxide layer and a silicon nitride layer at 40 Å / min or more and 100 Å / min or less. When the polishing composition contains 1,4-diaminobutane, it can polish a silicon layer at 3500 Å / min or more, and polish a silicon nitride layer at 40 Å / min or more and 100 Å / min or less, and it exhibits a lower polishing rate for a silicon oxide layer than for a silicon nitride layer (for example, less than 50%, or even less than 40%).

[0031] Next, an example of the use of the polishing composition will be described, taking as an example CMP in the process of forming a gate structure of a field effect transistor of a semiconductor device.

[0032] As shown in FIG. 1 , the polished object 1x to which the polishing composition is applied has a plurality of protrusions 10 each having a first layer 11 and a second layer 12 laminated on the first layer 11. The first layer 11 and the second layer 12 are formed of silicon oxide or silicon nitride. The first layer 11 and the second layer 12 are made of different materials. Recesses for forming gate electrodes are formed between each protrusion 10, and the recesses are filled with silicon. That is, the polished object 1x has two or more silicon-filled portions 20 between the protrusions 10. The polished object 1x also has a silicon layer 30 laminated on the second layer 12 during silicon filling.

[0033] The silicon oxide layer may be a layer formed of tetraethoxysilane (TEOS). The silicon nitride layer may be a layer formed by a CVD method. The silicon of the silicon filling portion 20 and the silicon layer 30 may be single crystal silicon, polysilicon having a polycrystalline structure, or amorphous silicon.

[0034] In the CMP of the object 1x to be polished, as shown in FIG. 1A, polishing of the silicon layer 30 may be followed by polishing to remove the upper ends of the first layer 11 and the silicon filling portion 20 (portions between the first layers 11). Alternatively, in the CMP of the object 1x to be polished, as shown in FIG. 1B, polishing of the silicon layer 30 may be followed by polishing to planarize the exposed surfaces of the second layer 12 and the silicon filling portion 20. In these CMP methods, the amount of silicon polished is greater than the amount of silicon oxide or silicon nitride polished. Therefore, the polishing composition is suitable because it can polish silicon at a relatively high polishing rate. On the other hand, in these CMP methods, the amount of silicon oxide or silicon nitride polished is less than the amount of silicon polished. Therefore, the polishing composition is suitable because its polishing rate for silicon oxide or silicon nitride is significantly lower than that for silicon, making polishing easy to control. Thus, the polishing composition allows continuous CMP of the polished object 1x without the need for composition changes. It is believed that this effect is achieved by the softening of the first layer 11, the second layer 12, or the silicon layer 30 by the amine compound. Therefore, it is believed that it is not necessary to use specific abrasive particles. On the other hand, from the viewpoint of compatibility with the amine compound, it is preferable that the abrasive particles be composed of colloidal silica particles.

[0035] 2, the polished object 1y to which the polishing composition is applied has a layer 13 made of silicon oxide or silicon nitride, and a plurality of recesses for forming gate electrodes are formed in the layer 13, and the recesses are filled with silicon. During the silicon filling, the upper ends of a pair of sidewalls defining the recesses are scraped off, and the recesses expand in diameter toward the upper end of the layer 13. That is, in the polished object 1y, an upper end 21 of a silicon-filled portion 20 expands in diameter.

[0036] The CMP of the object 1y may be performed so as to remove the expanded upper end 21 of the silicon filling portion 20 and the silicon oxide layer or silicon nitride layer laterally adjacent to the upper end 21. This CMP requires polishing silicon at a high polishing rate, as in the object 1x, but in addition, controlling the size of the silicon oxide layer or silicon nitride layer is important. In contrast, the polishing composition has a polishing rate for silicon oxide or silicon nitride that is significantly lower than the polishing rate for silicon, making it easier to control the size.

[0037] The polishing composition of the present embodiment contains any one of the above-described amine compounds, and thereby has the ability to polish silicon layers and at least one of silicon oxide layers and silicon nitride layers, and is particularly capable of polishing silicon layers with high selectivity.

[0038] The polishing composition of this embodiment has an amine compound content of 0.01% by mass or more and 1% by mass or less, thereby achieving superior polishing performance.

[0039] The polishing composition of this embodiment does not contain any chelating agent or oxidizing agent other than the amine compound, thereby suppressing aggregation of abrasive grains and providing excellent storage stability.

[0040] Although the embodiments have been shown as examples, the polishing composition of the present invention is not limited to the configurations of the above-mentioned embodiments. Furthermore, the polishing composition of the present invention is not limited by the above-mentioned effects. The polishing composition of the present invention can be modified in various ways without departing from the spirit of the present invention.

[0041] For example, the polishing composition of the present invention may consist of the abrasive grains, the amine compound, water, and the water-soluble polymer, or may consist of the abrasive grains, the amine compound, and water.

[0042] The polishing composition of the present invention may also contain the abrasive grains, the amine compound, and the water, wherein the content of the abrasive grains is 0.1% by mass or more and 5% by mass or less, the content of the amine compound is 0.02% by mass or more and 1% by mass or less, and the content of the water is 90% by mass or more, 95% by mass or more, or 98% by mass or more.

[0043] The polishing composition of the present invention may also be prepared by diluting a concentrate containing components such as the abrasive grains and the amine compound at higher concentrations than those described above with water. For example, the concentrate used to prepare the polishing composition may contain 10% by mass or more and 20% by mass or less of the abrasive grains relative to the total mass of the concentrate. While the concentrate is highly practical in terms of transportation, there is a risk of the abrasive grains agglomerating. To prevent such agglomeration, the mass ratio of the amine compound to the abrasive grains in the concentrate (content of the abrasive grains:content of the amine compound) is preferably 1:0.006 or more, more preferably 1:0.01 or more, and even more preferably 1:0.02 or more.

[0044] The present invention will be further explained below with reference to examples, but the present invention is not limited to these examples.

[0045] Polishing compositions were prepared by mixing the amine compounds shown in Table 1, abrasive grains (secondary particle diameter 70 nm) composed of colloidal silica particles, and water. The abrasive grain content was 1.0 mass %. The amine compound content was 0.1 mass %. Each polishing composition was used to polish a silicon layer, a silicon oxide layer, or a silicon nitride layer as a polishing target under the polishing conditions below, and the polishing rate was determined. The polishing performance was then evaluated based on the following evaluation criteria. The results are shown in Table 1.

[0046] (Polishing conditions) Polishing apparatus: Single-sided polishing machine manufactured by SpeedFam, model "SH-24CMP" (surface plate outer diameter: 609.6 mm) Polishing pad: IC1000 (registered trademark) manufactured by Nitta DuPont Polishing substrate: Silicon, TEOS (film thickness 7000 Å), p-SiN (film thickness 2000 Å) Polishing pressure: 3 PSI Rotation speed: 90 rpm Polishing time: 1 minute

[0047] (Evaluation Criteria) ∘: The polishing rate for silicon oxide or silicon nitride is 40 Å / min or more and 200 Å / min or less, and the ratio of the polishing rate for silicon to the polishing rate for silicon oxide or silicon nitride is 50 or more. ×: The polishing rate for silicon oxide or silicon nitride is less than 40 Å / min, or the ratio of the polishing rate for silicon to the polishing rate for silicon oxide or silicon nitride is less than 50.

[0048]

[0049] From the results in Table 1, it can be seen that Example 1 containing 1,3-diaminopropane has polishing performance for all polishing targets and can polish silicon with high selectivity. Also, Example 2 containing 1,4-diaminobutane has polishing performance for silicon and silicon nitride and can polish silicon with high selectivity.

[0050] Next, as shown in Table 2, another amine compound having a structure similar to that of the amine compound of Example 1 or Example 2 was evaluated. In this evaluation, the content of the amine compound was set to 0.05% by mass (the content of the abrasive grains remained unchanged at 1.0% by mass). The results are shown in Table 2.

[0051]

[0052] The evaluation results in Tables 1 and 2 show that, among amine compounds having a common structure, those containing 1,3-diaminopropane and 1,4-diaminobutane exhibit the desired polishing performance.

[0053] Next, polishing compositions were prepared in the same manner as in Example 1 (abrasive grains 1.0 mass %) except that the content of 1,3-diaminopropane was changed as shown in Table 3, and their polishing performance was evaluated.

[0054]

[0055] Next, polishing compositions were prepared in the same manner as in Example 1, except that 1,3-diaminopropane was replaced with an inorganic base, as shown in Table 4, and their polishing performance was evaluated. However, these polishing compositions did not have the desired polishing performance.

[0056]

[0057] Next, polishing compositions were prepared by varying the content of abrasive grains stepwise while setting the content of 1,3-diaminopropane at 0.02 mass % as shown in Table 5, and the polishing performance of each composition was evaluated.

[0058]

[0059] From the results in Table 5, it can be seen that as the amount of abrasive increases, the polishing rate for silicon tends to decrease, and the selectivity for silicon also tends to decrease. Therefore, it is considered that the content of abrasive grains is preferably 2 mass% or less.

[0060] Next, polishing compositions were prepared in the same manner as in Example 5, except that a chelating agent or an oxidizing agent was added, as shown in Table 6. However, these polishing compositions were found to exhibit aggregation of abrasive grains when measured using a dynamic light scattering method, and were not stable enough for practical use.

[0061]

[0062] As shown in Table 7, concentrates for preparing polishing compositions were prepared with abrasive grain content of 15 mass % and the 1,3-diaminopropane content varied in stages, and the stability of each concentrate was evaluated.

[0063]

[0064] 1x, 1y: object to be polished, 10: protrusion portion, 11: first layer, 12: second layer, 13: layer, 20: silicon filling portion, 21: upper end portion, 30: silicon layer

Claims

1. A polishing composition comprising an abrasive, an amine compound, and water, the amine compound being at least one of 1,3-diaminopropane and 1,4-diaminobutane.

2. The polishing composition according to claim 1, wherein the content of the amine compound is 0.01% by mass or more and 1% by mass or less.

3. The polishing composition according to claim 1 or 2, which does not contain any chelating agent or oxidizing agent other than the amine compound.

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