Polishing composition

Abstract

To provide a polishing composition having polishing performance for a silicon layer and for at least one of a silicon oxide layer or a silicon nitride layer, and capable of highly selectively polishing a silicon layer against at least one of the silicon oxide layer or the silicon nitride layer.SOLUTION: A polishing composition contains abrasive grains, an amine compound, and water, wherein the amine compound is 1,3-diaminopropane or 1,4-diaminobutane.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a polishing composition.

Background Art

[0002] Conventionally, in the manufacture of semiconductor devices, chemical mechanical polishing (hereinafter referred to as CMP) has been performed. In the manufacture of recent high-performance semiconductor devices, various objects to be polished are assumed. Therefore, polishing compositions are also required to have polishing performance according to the application.

[0003] For example, the polishing composition of Patent Document 1 is for the purpose of polishing to expose a copper electrode embedded in a silicon layer, and in addition to abrasive grains, it contains an alkali compound such as diamines and an oxidizing agent such as sodium chlorite. Patent Document 1 shows that by using this polishing composition, the silicon layer and the copper layer can be polished at the same polishing rate.

[0004] The polishing composition of Patent Document 2 can be applied to shallow trench isolation (STI) in the front-end-of-line (FEOL) process, and is intended to selectively polish the silicon oxide layer rather than the 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 on colloidal silica with a substance obtained by hydrolyzing aminosilane.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] By the way, in CMP for highly functional semiconductor devices in recent years, it may be required to polish a silicon layer such as a polysilicon layer together with a silicon oxide layer or a silicon nitride layer.

[0007] For example, in the formation of a gate structure of a field effect transistor such as GAA, after forming an insulating layer that becomes an insulating partition wall of the gate electrode, a recess for forming a gate electrode is formed in this insulating layer, and while filling this recess with polysilicon, a polysilicon deposition layer is formed on the insulating layer. Then, while removing the silicon deposition layer, CMP for planarizing the exposed surface of the gate electrode and the insulating layer is performed. Further, in the formation of 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 one of silicon oxide or silicon nitride and is composed of a material different from that of the insulating layer. Then, while removing the silicon deposition layer, CMP for planarizing or removing the cap layer is performed.

[0008] As exemplified above, it is assumed that the polishing amount is relatively large in the polishing of the deposition layer. Therefore, in this case, it is efficient to use a polishing composition with an increased polishing rate for silicon. On the other hand, it is assumed that the polishing amount is relatively small in the polishing of the insulating layer and the cap layer. Therefore, in this case, from the viewpoint of polishing control, it is desirable to use a composition that can exhibit an appropriate polishing rate corresponding to a small polishing amount rather than a polishing composition with an excessively increased polishing rate for silicon oxide or silicon nitride. Such circumstances can be assumed not only in the formation of the gate structure of a field effect transistor but also in other CMPs in the manufacture of semiconductor devices.

[0009] In view of the above circumstances, an object of the present invention is to provide a polishing composition having polishing performance for a silicon layer and at least one of a silicon oxide layer or a silicon nitride layer, and capable of highly selectively polishing the silicon layer with respect to at least one of the silicon oxide layer or the silicon nitride layer.

Means for Solving the Problems

[0010] The polishing composition according to the present invention is composed of abrasive grains, an amine compound, and water, wherein the amine compound is 1,3-diaminopropane or 1,4-diaminobutane.

[0011] By containing any of the above amine compounds, the polishing composition having such a configuration has polishing performance for a silicon layer and polishing performance for at least one of a silicon oxide layer or a silicon nitride layer, and among these, the silicon layer can be polished with high selectivity.

[0012] Also, 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] According to such a configuration, the above polishing performance becomes more excellent.

[0014] Also, the polishing composition according to one aspect of the present invention does not contain a chelating agent and an oxidizing agent other than the amine compound.

[0015] According to such a configuration, aggregation of the abrasive grains is suppressed, and the storage stability is excellent.

Advantages of the Invention

[0016] As described above, according to the present invention, it is possible to provide a polishing composition having polishing performance for a silicon layer and polishing performance for at least one of a silicon oxide layer or a silicon nitride layer, and capable of highly selectively polishing the silicon layer with respect to at least one of the silicon oxide layer or the silicon nitride layer.

Brief Description of the Drawings

[0017]

Figure 1

Figure 2

Embodiments for Carrying Out the Invention

[0018] Hereinafter, the polishing composition according to the embodiment of the present invention will be described.

[0019] The polishing composition of the present embodiment contains abrasive grains, an amine compound, water, and an optional additive. The polishing composition of the present embodiment is a polishing slurry in which the abrasive grains are dispersed in water.

[0020] Examples of the particles constituting the abrasive grains include inorganic particles, organic particles, or organic-inorganic composite particles. Examples of the inorganic particles include silica particles, alumina particles, titania particles, zirconia particles, ceria particles, and calcium carbonate particles. Examples of the silica particles include fumed silica particles, colloidal silica particles, and silica particles obtained by the sol-gel method. Examples of the 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 the organic-inorganic composite particles include particles obtained by polycondensing a metal or silicon alkoxide compound (for example, alkoxysilane, aluminum alkoxide, titanium alkoxide, etc.) in the presence of organic particles. The abrasive grains may be composed of only one of these, or may be composed of two or more.

[0021] The secondary particle diameter of the abrasive grains measured by the dynamic light scattering method is preferably 500 nm or less. The secondary particle diameter of the abrasive grains is, for example, 10 nm or more.

[0022] The content of the abrasive grains is more preferably 0.1% by mass or more and 5.0% by mass or less, and even more preferably 0.3% by mass or more and 2.5% by mass or less with respect to the mass of the polishing composition.

[0023] 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 both of them.

[0024] The content of the amine compound is preferably 0.01% by mass or more, more preferably 0.02% by mass or more and 1% by mass or less, and even more preferably 0.05% by mass or more, based on the mass of the polishing composition. Also, the content of the amine compound is preferably 1% by mass or less.

[0025] More specifically, when the amine compound is 1,3-diaminopropane, the content is preferably 0.01% by mass or more. Thereby, the polysilicon layer can be polished at a high polishing rate, and the silicon oxide layer and the silicon nitride layer can be polished at an appropriate polishing rate lower than the polishing rate of the polysilicon layer. Also, the silicon oxide layer and the silicon nitride layer can be polished at approximately the same polishing rate.

[0026] Also, when the amine compound is 1,4-diaminobutane, the content is preferably 0.01% by mass or more and 1% by mass or less.

[0027] 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.

[0028] As the water, purified water such as distilled water and ion-exchanged water is preferred. 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.

[0029] Examples of the additive 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 derivatives), and polyvinyl pyrrolidone; glycosides; and polyhydric alcohols. Examples of the glycosides include alkylene oxide derivatives of methyl glucoside such as polyoxyethylene methyl glucoside and polyoxypropylene methyl glucoside.

[0030] Preferably, the polishing composition does not contain additives other than the above additives. Examples of such additives include chelating agents such as glycine other than the above amine compounds, oxidizing agents such as hydrogen peroxide water, and antifoaming agents such as silicone emulsions. 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, preferably 0.5% by mass or less, and more preferably 0.1% by mass or less.

[0031] The pH of the polishing composition is preferably 8 to 12, and may be 8 to 11.

[0032] When the polishing composition contains 1,3-diaminopropane, the silicon layer can be polished at 3500 Å / min or more, and the silicon oxide layer and the silicon nitride layer can be polished at 40 Å / min or more and 100 Å / min or less. When the polishing composition contains 1,4-diaminobutane, the silicon layer can be polished at 3500 Å / min or more, and the silicon nitride layer can be polished at 40 Å / min or more and 100 Å / min or less, and the polishing rate for the silicon oxide layer is lower than that for the silicon nitride layer (for example, less than 50%, and may be less than 40%).

[0033] Next, regarding the usage example of the polishing composition, an explanation will be given while exemplifying CMP in the formation process of a gate structure included in a field effect transistor of a semiconductor device.

[0034] As shown in FIG. 1, the object to be polished 1x to which the polishing composition is applied includes a plurality of ridge portions 10 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. Also, the formation materials of the first layer 11 and the second layer 12 are different. Between each ridge portion 10, a recess for forming a gate electrode is formed, and the recess is filled with silicon. That is, the object to be polished 1x includes two or more silicon filling portions 20 between the ridge portions 10. Further, the object to be polished 1x includes a silicon layer 30 laminated on the second layer 12 during silicon filling.

[0035] The layer formed of silicon oxide may be a layer formed of tetraethoxysilane (TEOS). The layer formed of silicon nitride may be a layer formed by the CVD method. The silicon in the silicon filling portion 20 and the silicon layer 30 may be single crystal silicon, polysilicon having a polycrystalline structure, or amorphous silicon.

[0036] In the CMP of the workpiece 1x, as shown in Fig. 1(a), following the polishing of the silicon layer 30, polishing may be performed to remove the upper ends (the portions between the first layers 11) of the first layer 11 and the silicon filling portion 20. Further, in the CMP of the workpiece 1x, as shown in Fig. 1(b), following the polishing of the silicon layer 30, polishing may be performed to planarize the exposed surface of the second layer 12 and the exposed surface of the silicon filling portion 20. In these CMPs, the polishing amount of the portion composed of silicon is larger than the polishing amount of the portion composed of silicon oxide or silicon nitride. Therefore, the polishing composition is suitable because it can polish silicon at a relatively high polishing rate. On the other hand, in these CMPs, the polishing amount of the portion composed of silicon oxide or silicon nitride is smaller than the polishing amount of the portion composed of silicon. Therefore, the polishing composition is suitable because the polishing rate for silicon oxide or silicon nitride is suppressed to be much lower than the polishing rate of silicon, and it is easy to control the polishing. Thus, according to the polishing composition, CMP of the workpiece 1x can be continuously performed without requiring a change in the composition. It is considered that such an effect is obtained by softening the first layer 11, the second layer 12, or the silicon layer 30 by the amine compound. Therefore, it is considered that there is no need to use specific abrasive grains. On the other hand, from the viewpoint of compatibility with the amine compound, the abrasive grains are preferably composed of colloidal silica particles.

[0037] Next, as shown in Fig. 2, the workpiece 1y to which the polishing composition is applied includes a layer 13 formed 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. Further, when the silicon is filled, the upper ends of a pair of side wall portions defining the recesses are worn away, and the recesses are enlarged toward the upper end of the layer 13. That is, in the workpiece 1y, the upper end portion 21 of the silicon filling portion 20 is enlarged in diameter.

[0038] In the CMP of the workpiece 1y, polishing may be performed to remove the enlarged upper end portion 21 of the silicon filling portion 20 and the silicon oxide layer or silicon nitride layer adjacent to the upper end portion 21 in the lateral direction. In this CMP, the requirement to polish silicon at a high polishing rate is the same as that for the workpiece 1x. In addition to this, control of the dimensions of the silicon oxide layer or silicon nitride layer becomes important. In contrast, since the polishing rate of the polishing composition with respect to silicon oxide or silicon nitride is suppressed to be much lower than the polishing rate of silicon, control of the dimensions can be made easier.

[0039] As described above, although the exemplary embodiments have been shown, the polishing composition according to the present invention is not limited to the configurations of the above embodiments. Also, the polishing composition according to the present invention is not limited by the above-described functions and effects. The polishing composition according to the present invention can be variously modified without departing from the gist of the present invention.

[0040] For example, the polishing composition of the present invention may be composed of the abrasive grains, the amine compound, the water, and the water-soluble polymer, or may be composed of the abrasive grains, the amine compound, and the water.

[0041] Also, the polishing composition of the present invention contains the abrasive grains, the amine compound, and the water, 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 may be 90% by mass or more, or 95% by mass or more, or 98% by mass or more.

[0042] Further, the polishing composition of the present invention may be prepared by diluting a concentrate in which the concentrations of each component such as the abrasive grains and the amine compound are higher than the above with the water. For example, in the concentrate for preparing the polishing composition, the content of the abrasive grains may be 10% by mass or more and 20% by mass or less with respect to the total mass of the concentrate. Although the concentrate is excellent in practicality in terms of transportation, the abrasive grains may aggregate. From the viewpoint of suppressing such aggregation, 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.

Examples

[0043] Hereinafter, the present invention will be further described by way of examples, but the present invention is not limited thereto.

[0044] An amine compound shown in Table 1, abrasive grains composed of colloidal silica particles (secondary particle diameter 70 nm), and water were mixed to prepare a polishing composition. The content of the abrasive grains was 1.0% by mass. The content of the amine compound was 0.1% by mass. Using each polishing composition, a silicon layer, a silicon oxide layer, or a silicon nitride layer as a body to be polished was polished under the following polishing conditions, and the polishing rate was determined. Then, the polishing performance was evaluated based on the following evaluation criteria. The results are as shown in Table 1.

[0045] (Polishing conditions) Polishing apparatus: Single-sided polishing machine manufactured by SpeedFam, model "SH-24CMP" (platen outer diameter: 609.6 mm in diameter) Polishing pad: Manufactured by Nitto DuPont, IC1000 (registered trademark) 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

[0046] (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

[0047]

Table 1

[0048] From the results in Table 1, Example 1 containing 1,3-diaminopropane is recognized to have polishing performance for any polishing target and to be able to polish silicon highly selectively. Also, Example 2 containing 1,4-diaminobutane is recognized to have polishing performance for silicon and silicon nitride and to be able to polish silicon highly selectively.

[0049] 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 to be evaluated. In this evaluation, the content of the amine compound was set to 0.05% by mass (the content of the abrasive grains was not changed and was 1.0% by mass). The results are as shown in Table 2.

[0050]

Table 2

[0051] From the evaluation results in Table 1 and Table 2, it can be seen that among the amine compounds having a common structure, those containing 1,3-diaminopropane and 1,4-diaminobutane exhibit the desired polishing performance.

[0052] Next, as shown in Table 3, a polishing composition was prepared in the same manner as in Example 1 except that the content of 1,3-diaminopropane was changed (abrasive grains 1.0% by mass), and its polishing performance was evaluated.

[0053]

Table 3

[0054] Next, as shown in Table 4, a polishing composition was prepared in the same manner as in Example 1 except that 1,3-diaminopropane was changed to an inorganic base, and its polishing performance was evaluated. However, these polishing compositions did not have the desired polishing performance.

[0055]

Table 4

[0056] Next, as shown in Table 5, the content of 1,3-diaminopropane was set to 0.02% by mass, and the content of abrasive grains was changed stepwise to prepare polishing compositions, and the polishing performance of each was evaluated.

[0057]

Table 5

[0058] From the results in Table 5, as the amount of abrasive grains increases, the polishing rate for silicon shows a decreasing trend, and accordingly, the selectivity for silicon also shows a decreasing trend. From this, it is considered that the content of abrasive grains is preferably 2% by mass or less.

[0059] Next, as shown in Table 6, polishing compositions were prepared in the same manner as in Example 5 except that a chelating agent or an oxidizing agent was added. However, in the measurement using the dynamic light scattering method, aggregation of abrasive grains was observed in these polishing compositions, and they did not have practical stability.

[0060]

Table 6

[0061] As shown in Table 7, concentrates for preparing polishing compositions were prepared by setting the abrasive content to 15% by mass and gradually changing the content of 1,3-diaminopropane, and the stability of each was evaluated.

[0062] [Table 7] [Explanation of Symbols]

[0063] 1x, 1y: Workpiece to be polished, 10: Ridge portion, 11: First layer, 12: Second layer, 13: Layer, 20: Silicon filling portion, 21: Upper end portion, 30: Silicon layer

Claims

Claim 1 A polishing composition comprising abrasive grains, an amine compound, and water, wherein the amine compound is 1,3-diaminopropane or 1,4-diaminobutane. Claim 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. Claim 3 The polishing composition according to claim 1 or 2, which does not contain a chelating agent and an oxidizing agent other than the amine compound.

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