Etching composition, method for etching insulating film using the same, and method for preparing semiconductor devices

Abstract

To provide an etching composition which can selectively remove a nitride film relatively to an oxide film, and can prevent particle generation having adverse effects on device characteristics.SOLUTION: An etching composition includes phosphoric acid, a silane compound comprising at least one Si atom, and an organic phosphate represented by chemical formula 1 in the figure, where R1 to R3 are independently hydrogen, or substituted or unsubstituted hydrocarbyl, provided that at least one of R1 to R3 is substituted or unsubstituted hydrocarbyl.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an etching composition, and more particularly to an etching composition with a high selectivity that can minimize the etching rate of an oxide film and selectively remove a nitride film. [Background technology]

[0002] Oxide films such as silicon oxide (SiO2) and nitride films such as silicon nitride (SiNx) are typical insulating films, and these silicon oxide and silicon nitride films are used alone or in the form of alternating layers of one or more films in the semiconductor manufacturing process. These oxide and nitride films are also used as hard masks for forming conductive patterns such as metal wiring.

[0003] In the wet etching process for removing nitride films, a mixture of phosphoric acid and deionized water is typically used. The deionized water is added to prevent a decrease in the etching rate and a change in the etching selectivity of nitride films relative to oxide films. However, even a slight change in the amount of deionized water supplied can cause defects in the nitride film etching removal process. In addition, phosphoric acid is a strong acid and is corrosive, making it difficult to handle.

[0004] To solve this problem, a conventional method for removing the nitride film using an etching composition containing phosphoric acid (H3PO4), hydrofluoric acid (HF) or nitric acid (HNO3) has been known, but this method has the effect of inhibiting the etching selectivity between the nitride film and the oxide film.

[0005] Furthermore, a technique using an etching composition containing phosphoric acid and silicate, or silicic acid, is also known. However, silicic acid and silicate induce particles that can affect the substrate, which makes them unsuitable for semiconductor manufacturing processes.

[0006] However, when phosphoric acid is used in the wet etching process for removing the nitride film, the etching selectivity between the nitride film and the oxide film decreases, resulting in etching of not only the nitride film but also the SOD oxide film, making it difficult to control the effective field oxide height (EFH). As a result, it may be difficult to ensure sufficient wet etching time for removing the nitride film, or an additional process may be required, which may cause changes in device characteristics and adversely affect device characteristics.

[0007] Therefore, in the semiconductor manufacturing process, there is a need for an etching composition with a high selectivity that can selectively etch nitride films relative to oxide films without causing problems such as particle generation.

[0008] Meanwhile, silane-based additives, which are additives added to conventional etching compositions, have low solubility and do not ensure proper solubility, resulting in problems such as particle deposition in the etching composition and abnormal growth on the substrate. These particles remain on the silicon substrate, causing defects in devices realized on the substrate, or remain in equipment used in the etching or cleaning process, causing equipment failure.

[0009] Furthermore, when the etching solution is stored for a long period of time, the etching rates of the nitride film and the silicon oxide film may change, which may change the selectivity. Summary of the Invention [Problem to be solved by the invention]

[0010] An object of the present invention is to provide an etching composition with high selectivity that can minimize the etching rate of an oxide film and selectively remove a nitride film without problems such as generation of particles that adversely affect device characteristics.

[0011] Another object of the present invention is to provide an etching composition having excellent storage stability.

[0012] A further object of the present invention is to provide a method for etching an insulating film using the etching composition and a method for manufacturing a semiconductor device. [Means for solving the problem]

[0013] The present invention provides an etching composition, and the etching composition according to one embodiment of the present invention includes phosphoric acid, a silane compound containing one or more Si atoms, and an organic phosphoric acid represented by the following Chemical Formula 1:

[0014] [ka]

[0015] where R 1 ~R 3 are independently hydrogen, substituted or unsubstituted hydrocarbyl, and R 1 ~R 3 At least one of is a substituted or unsubstituted hydrocarbyl.

[0016] The hydrocarbyl may be a substituted or unsubstituted C-C 20 Alkyl, substituted or unsubstituted C-C 20 Alkenyl, or substituted or unsubstituted C6-C 20 It can be aryl, for example, R 1 ~R 3 is a substituted or unsubstituted C1-C 10 Alkyl, substituted or unsubstituted C-C 10 Alkenyl, or substituted or unsubstituted C6-C 10 It can be aryl.

[0017] The above chemical formula 1 can be selected from the following structural formulas (1) to (27).

[0018] [ka] [ka]

[0019] The silane compound may be represented by the following chemical formula 2.

[0020] [ka]

[0021] In the above chemical formula 2, R 51 ~R 54 are each independently hydrogen, substituted or unsubstituted hydrocarbyl, or substituted or unsubstituted heterohydrocarbyl; R 51 ~R 54 are present individually or two or more are connected to each other via a heteroatom to form a ring.

[0022] The etching composition may contain 70 to 95 wt % of phosphoric acid, 0.001 to 5 wt % of a silane compound, and 0.001 to 10 wt % of the organic phosphoric acid represented by Chemical Formula 1.

[0023] The etching composition may further include an ammonium salt.

[0024] The present invention provides a method for etching an insulating film using any one of the etching compositions described above.

[0025] The present invention also provides a method for manufacturing a semiconductor device, the method including: sequentially forming a tunnel oxide film, a polysilicon film, a buffer oxide film, and a pad nitride film on a substrate; selectively etching the polysilicon film, the buffer oxide film, and the pad nitride film to form a trench; forming an SOD oxide film to gap-fill the trench; performing a chemical mechanical polishing (CMP) process on the SOD oxide film using the pad nitride film as a polishing stop film; removing the pad nitride film by wet etching using any one of the etching compositions described above; and removing the buffer oxide film. [Effects of the Invention]

[0026] The etching composition according to the present invention has a high etching selectivity for nitride films relative to oxide films.

[0027] Furthermore, use of the etching composition of the present invention can prevent damage to the oxide film during removal of the nitride film, and deterioration of electrical characteristics due to etching of the oxide film, and can prevent generation of particles, thereby improving device characteristics. [Brief explanation of the drawings]

[0028] [Figure 1] 1A to 1C are cross-sectional views illustrating process steps of an insulating film etching method according to an embodiment of the present invention. [Figure 2] 1A to 1C are cross-sectional views illustrating process steps of an insulating film etching method according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0029] The present invention provides an etching composition, particularly an etching composition having a high selectivity that can minimize the etching rate of an oxide film and selectively remove a nitride film, and also having excellent storage stability.

[0030] The etching composition of the present invention contains phosphoric acid, which reacts with silicon nitride to etch the nitride, and the phosphoric acid etches silicon nitride according to the following reaction formula (1):

[0031] 3Si3N4+27H2O+4H3PO4→4(NH4)3PO4+9SiO2H2O …(1)

[0032] The phosphoric acid may be contained in an amount of 70 to 95 wt % based on the total weight of the etching composition. If the phosphoric acid content is less than 70 wt %, the nitride film may not be easily removed, while if it exceeds 95 wt %, a high selectivity of the nitride film to the oxide film may not be obtained.

[0033] For example, the phosphoric acid may be an aqueous solution of phosphoric acid containing phosphoric acid at a concentration of 75 to 95%. The water used in the aqueous solution of phosphoric acid is not particularly limited, but deionized water may be used.

[0034] The etching composition of the present invention also contains an organic phosphoric acid represented by the following Chemical Formula 1:

[0035] [ka]

[0036] In the above chemical formula 1, R 1 ~R 3 can be independently hydrogen, substituted or unsubstituted hydrocarbyl, wherein the hydrocarbyl is a substituted or unsubstituted C-C 20 Alkyl, substituted or unsubstituted C-C 20 Alkenyl, or substituted or unsubstituted C6-C 20 The R 1 ~R 3 It goes without saying that R may be different from each other, and two or more may be the same. 1 ~R 3At least one of is a substituted or unsubstituted hydrocarbyl, except when all are hydrogen.

[0037] For example, the above R 1 ~R 3 is a substituted or unsubstituted C1-C aryl such as methyl, ethyl, or 2-ethylhexyl. 10 alkyl, substituted or unsubstituted C2-C such as -CH2CH(=CH2) 10 C6-C such as alkenyl or benzyl 10 It can be aryl, and the substitutions can be with halogens such as Cl, F, etc., alkoxy groups, -NO2, etc.

[0038] The organophosphate represented by Chemical Formula 1 provided by the present invention provides structural stability to the silane compound, suppressing phenomena such as decomposition or abnormal growth of the silane compound, thereby suppressing gelation of the etching composition and maintaining its role of inhibiting etching of silicon oxide.

[0039] The organic phosphoric acid contained in the etching composition of the present invention may be any one of those represented by the above chemical formula 1, or two or more of them may be mixed and used.

[0040] The organic phosphoric acid used in the present invention includes, for example, organic phosphoric acids represented by the following structural formulas (1) to (27).

[0041] [ka] [ka]

[0042] The organic phosphoric acid of Formula 1 can prevent gelation of the etching composition and can be added in an amount of 0.001 to 10 wt% based on the total weight of the etching composition. If the organic phosphoric acid is added in an amount of less than 0.001 wt%, the effect of improving physical properties by reducing gelation is minimal, but if it is added in an amount of more than 10 wt%, the organic phosphoric acid may cause gelation.

[0043] The organic phosphoric acid of Chemical Formula 1 may be present in an amount of, for example, 0.001 to 5 wt%, 0.001 to 3 wt%, 0.001 to 2 wt%, 0.001 to 1 wt%, 0.005 to 5 wt%, 0.005 to 3 wt%, 0.005 to 2 wt%, 0.005 to 1 wt%, 0.01 to 5 wt%, 0.01 to 3 wt%, 0.01 to 2 wt%, 0.01 to 1 wt%, 0.05 to 5 wt%, 0.05 to 3 wt%, 0.05 to 2 wt%, 0.05 to 1 wt%, 0.1 to 5 wt%, 0.1 to 3 wt%, 0.1 to 2 wt%, 0.1 to 1 wt%, 0.5 to 5 wt%, 0.5 to 3 wt%, 0.5 to 2 wt%, or 0.5 to 1 wt%.

[0044] The etching composition of the present invention contains a silane compound. In the present invention, the silane compound can be suitably any silane compound containing one or more Si atoms, and more preferably a silane compound represented by the following chemical formula 2:

[0045] [ka]

[0046] In the above chemical formula 2, R 51 ~R 54 are independently hydrogen, C1-C 20 Substituted or unsubstituted hydrocarbyl such as hydrocarbyl, or C-C 20 The R may be a substituted or unsubstituted heterohydrocarbyl, such as heterohydrocarbyl. 51 ~R 54 may be present individually or two or more may be connected to each other via a heteroatom to form a ring. For example, hydrogen, C-C20 Alkyl, or C1-C 20 In this case, the hetero element is not particularly limited, but may be, for example, N, S, O, P, or the like.

[0047] The silane compound represented by Chemical Formula 2 may be contained in an amount of 0.005 to 1 wt % based on the total weight of the etching composition.

[0048] Furthermore, the etching composition of the present invention may further contain an ammonium salt as an additive in addition to the organic phosphoric acid represented by Chemical Formula 1.

[0049] As the ammonium salt, compounds having ammonium ions that are commonly used in the field to which the present invention pertains can be suitably used in the present invention. Examples of such ammonium salts include, but are not limited to, aqueous ammonia, ammonium chloride, ammonium acetate, ammonium phosphate, ammonium peroxodisulfate, ammonium sulfate, and ammonium hydrofluoride. Needless to say, any one of these may be used alone, or two or more may be used in combination.

[0050] Furthermore, the etching composition of the present invention may further contain any additive commonly used in the art to further improve etching performance, such as a surfactant, a sequestering agent, or a corrosion inhibitor.

[0051] The remainder of the etching composition of the present invention is a solvent, which is not particularly limited, but may be water.

[0052] The etching composition of the present invention is used to selectively etch and remove a nitride film from a semiconductor device that includes an oxide film and a nitride film, and the nitride film includes a silicon nitride film, such as a SiN film or a SiON film.

[0053] The oxide film may be a silicon oxide film, for example, an SOD (Spin On Dielectric) film, an HDP (High Density Plasma) film, a thermal oxide film, a BPSG (Borophosphate Silicate Glass) film, a PSG (Phospho Silicate Glass) film, a BSG (Boro Silicate Glass) film, a PSZ (Polysilazane) film, an FSG (Fluorinated Silicate Glass) film, an LPTEOS (Low Pressure Tetra Ethyl Orthosilicate) film, a PETEOS (Plasma Enhanced Tetra Ethyl Orthosilicate) film, an HTO (High Temperature Oxide) film, an MTO (Medium Temperature Oxide) film, a USG (Undoped Silicate Glass) film, an SOG (Spin On Glass) film, an APL (Advanced Planarization Layer) film, an ALD (Atomic Layer Deposition) film, a PE-oxide film (Plasma Enhanced The film may be at least one film selected from the group consisting of an O3-TEOS (O3-Tetra Ethyl Orthosilicate) film, an O3-TEOS (O3-Tetra Ethyl Orthosilicate) film, and a combination thereof.

[0054] The etching process using the etching composition of the present invention may be carried out by a wet etching method, such as a dipping method or a spraying method.

[0055] An example of an etching process using the etching composition of the present invention is schematically shown in Figures 1 and 2. Figures 1 and 2 are cross-sectional views showing an example of an element isolation process for a flash memory device.

[0056] 1, a tunnel oxide film 11, a polysilicon film 12, a buffer oxide film 13, and a pad nitride film 14 are sequentially formed on a substrate 10, and then the polysilicon film 12, the buffer oxide film 13, and the pad nitride film 14 are selectively etched to form a trench. Next, an SOD oxide film 15 is formed until the trench is gap-filled, and then a CMP process is performed on the SOD oxide film 15 using the pad nitride film 14 as a polishing stop film.

[0057] 2, the pad nitride film 14 is removed by wet etching using the etching composition of the present invention, and then the buffer oxide film 13 is removed by a cleaning process, thereby forming an isolation film 15A in the field region.

[0058] The process temperature during the etching process can be in the range of 50 to 300°C, preferably in the range of 100 to 200°C, and more preferably in the range of 156 to 163°C, and the appropriate temperature can be changed as necessary, taking into consideration other processes and other factors.

[0059] As described above, the method for manufacturing a semiconductor device including an etching process using the etching composition of the present invention enables selective etching of nitride films when nitride films and oxide films are alternately stacked or mixed together, and also prevents particle generation, which is a problem in conventional etching processes, thereby ensuring process stability and reliability.

[0060] Therefore, this method can be efficiently applied to various processes in the manufacturing process of semiconductor devices where selective etching of nitride films relative to oxide films is required.

[0061] Example The present invention will be described in more detail below with reference to examples. The following examples are merely examples of the present invention, and the present invention is not limited thereto.

[0062] Example 1 A substrate was prepared in which a silicon oxide film (SiOx) with a thickness of 500 Å (angstroms) and a silicon nitride film (SiN) with a thickness of 5000 Å were deposited on a semiconductor wafer.

[0063] As shown in Table 1, an etching composition was prepared by adding 0.5 wt % of 3-aminopropylsilanetriol and 0.1 wt % of trimethyl phosphate (organic phosphoric acid additive 1) to 99.4 wt % of 85% phosphoric acid and mixing them to make a total of 100 wt %.

[0064] Example 2 An etching composition was prepared in the same manner as in Example 1, except that triethyl phosphate (organophosphate additive 2) was used instead of organophosphate additive 1 in Example 1.

[0065] Example 3 An etching composition was prepared in the same manner as in Example 1, except that triphenyl phosphate (organophosphate additive 3) was used instead of organophosphate additive 1 in Example 1.

[0066] Example 4 An etching composition was prepared in the same manner as in Example 1, except that tris(2-chloroethyl)phosphate (organophosphate additive 4) was used instead of organophosphate additive 1 in Example 1.

[0067] Example 5 An etching composition was prepared in the same manner as in Example 1, except that tris(2-ethylhexyl)phosphate (organophosphate additive 5) was used instead of organophosphate additive 1 in Example 1.

[0068] Comparative Example 1 An etching composition was prepared in the same manner as in Example 1, except that no organophosphate additive was used.

[0069] Comparative Example 2 An etching composition was prepared in the same manner as in Example 1, except that (NH4)OAc (ammonium acetate) was used instead of the organophosphate additive 1 in Example 1.

[0070] <Preparation of Etching Composition and Measurement of Selectivity> Each of the etching compositions obtained in Examples 1 to 5 and Comparative Examples 1 and 2 was placed in a round-bottom flask and heated for 60 minutes to 158°C. The silicon wafer was then immersed for 720 seconds and then for a further 6,000 seconds to carry out the etching process.

[0071] After selectively etching the surface of the patterned silicon wafer, the thicknesses of the silicon oxide and nitride films before and after etching were measured using ellipsometry, a thin film thickness measurement device (NANO VIEW, SEMG-1000). From these measurements, the etch rates of the silicon oxide film (SiO E / R, Å / min) and nitride film (SiN E / R, Å / min) and selectivity ratios were calculated. The results are shown in Table 1.

[0072] The selectivity ratio represents the ratio of the etching rate of a nitride film to the etching rate of an oxide film, and the etching rate is calculated by dividing the difference between the initial value and the film thickness after etching by the etching time (minutes).

[0073] [Table 1]

[0074] As can be seen from Table 1, when the etching compositions containing organic phosphoric acid additives 1 to 5 were used as additives to the etching composition, the etching selectivity was significantly higher than that of Comparative Example 1. Furthermore, in terms of the etching rate (SiN E / R) of the silicon nitride film, the etching compositions exhibited significantly superior effects compared to the etching composition of Comparative Example 1, confirming that an etching composition optimized for the etching process of a silicon nitride film can be provided. From these results, it can be confirmed that the use of the organic phosphoric acid proposed in the present invention as an additive improves the stability of the active silicon-based structure, and therefore it is possible to provide an etching composition that improves the etching rate, etching selectivity, and etching stability of the silicon nitride film, thereby improving the efficiency of the etching process.

[0075] Checking the change in etching composition over time The etching compositions of Comparative Example 1 and Example 1 were stored at about 70° C. for a certain period of time, and then the etching compositions were subjected to further etching tests under the same conditions every 7 days. The results are shown in Table 2.

[0076] [Table 2]

[0077] As can be seen from Table 2 above, after 21 days, the etching composition of Comparative Example 1 showed a significant decrease in etching rate (SiN E / R, SiO E / R) and selectivity. However, the etching composition of Example 1 to which organic phosphoric acid additive 1 was added showed almost no change in etching rate (SiN E / R, SiO E / R) and selectivity. From these results, it can be seen that the etching composition according to one embodiment of the present invention not only has excellent etching rate and selectivity, but also has excellent storage stability and can maintain excellent etching properties even when stored for a long period of time.

[0078] These results are due to the structural stability of organophosphate additive 1, and indicate that it can maintain its role in inhibiting SiO etching without causing phenomena such as decomposition or abnormal growth of 3-aminopropylsilanetriol.

Claims

1. An etching composition comprising phosphoric acid, 3-aminopropylsilanetriol, and an organic phosphoric acid represented by the following chemical formula 1: 【Chemical 1】 (where R １ ~R ３ is independently a C substituted or unsubstituted with chlorine (Cl); １ -C ８ alkyl, or phenyl.)

2. 2. The etching composition according to claim 1, wherein the organophosphoric acid of the chemical formula 1 is selected from the following structural formulas (1), (2), (5), (9), and (12): 【Chemistry 2】

3. 3. The etching composition according to claim 1, comprising 70 to 95% by weight of the phosphoric acid, 0.001 to 5% by weight of the silane compound, and 0.001 to 10% by weight of the organic phosphoric acid.

4. The etching composition according to claim 1 , further comprising an ammonium salt.

5. A method for etching an insulating film using the etching composition according to claim 1 .

6. forming a tunnel oxide film, a polysilicon film, a buffer oxide film, and a pad nitride film on a substrate in sequence; selectively etching the polysilicon layer, the buffer oxide layer, and the pad nitride layer to form a trench; forming an SOD oxide layer to gap-fill the trench; performing a chemical mechanical polishing (CMP) process on the SOD oxide film using the pad nitride film as a polishing stop; removing the pad nitride film by wet etching using the etching composition of claim 1; removing the buffer oxide film.

Images