Substrate processing method and substrate processing apparatus

Abstract

This substrate processing method includes: preparing a substrate having a surface from which a titanium nitride film and a zirconium oxide film are exposed; and selectively etching the zirconium oxide film from among the titanium nitride film and the zirconium oxide film by supplying an etching solution containing hydrogen fluoride and an organic solvent, to the surface of the substrate.

Description

[Technical Field]

[0001] This disclosure relates to a substrate processing method and a substrate processing apparatus. [Background technology]

[0002] The substrate processing method described in Patent Document 1 involves etching zirconium oxide with a processing solution containing sulfuric acid. Zirconium oxide is a gate insulating film material and is a high dielectric constant material. The processing solution containing sulfuric acid is preheated to a range of 150°C to 180°C.

[0003] The substrate processing method described in Patent Document 2 involves selectively etching the lower layer of the substrate with a mixture of dilute hydrofluoric acid (DHF), obtained by diluting hydrofluoric acid with water, and isopropyl alcohol (IPA). The lower layer is glass containing boron or phosphorus. The upper layer is a silicon oxide film. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2003-273066 [Patent Document 2] Japanese Patent Application Publication No. 2020-140984 [Overview of the project] [Problems that the invention aims to solve]

[0005] One aspect of this disclosure provides a technique for selectively etching a zirconium oxide film among a titanium nitride film and a zirconium oxide film. [Means for solving the problem]

[0006] A substrate processing method according to one aspect of the present disclosure comprises preparing a substrate having a surface on which a titanium nitride film and a zirconium oxide film are exposed, and selectively etching the zirconium oxide film from the titanium nitride film by supplying an etching solution containing hydrogen fluoride and an organic solvent to the surface of the substrate. The substrate processing method comprises, in this order, supplying an organic solvent substantially free of water to the surface of the substrate after supplying the etching solution, supplying a mixture of the organic solvent and water to the surface of the substrate, and supplying pure water to the surface of the substrate. [Effects of the Invention]

[0007] According to one aspect of this disclosure, the zirconium oxide film can be selectively etched from the titanium nitride film and the zirconium oxide film. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a cross-sectional view showing a substrate processing apparatus according to one embodiment. [Figure 2] Figure 2 is a cross-sectional view showing an example of a substrate to be prepared. [Figure 3] Figure 3 is a flowchart showing a substrate processing method according to one embodiment. [Figure 4] Figure 4 shows an example of the relationship between the mixing ratio of the etching solution and the etching rate of the zirconium oxide film. [Figure 5] Figure 5 shows an example of the relationship between film type (TiN, TiSiN, SiN) and film etching rate. [Modes for carrying out the invention]

[0009] Embodiments of this disclosure will be described below with reference to the drawings. In each drawing, the same or corresponding components are denoted by the same reference numerals, and their descriptions may be omitted. In Figure 1, the X-axis, Y-axis, and Z-axis directions are perpendicular to each other. The X-axis and Y-axis directions are horizontal, and the Z-axis direction is vertical.

[0010] Referring to Figures 1 and 2, a substrate processing apparatus 1 according to one embodiment will be described. The substrate processing apparatus 1 processes the surface Wa of a substrate W by supplying a processing solution to the surface Wa of the substrate W. In this embodiment, the substrate processing apparatus 1 is a single-wafer type that processes substrates W one at a time, but it may also be a batch type that processes multiple substrates W at once.

[0011] The single-wafer substrate processing apparatus 1 rotates the substrate W while holding it horizontally with the surface Wa of the substrate W facing upwards, and supplies processing liquid to the surface Wa of the substrate W. The single-wafer substrate processing apparatus 1 includes, for example, a processing container 10, a substrate holding unit 20, a substrate rotating unit 25, a supply unit 31, a nozzle 41, a moving unit 51, a recovery unit 60, and a control unit 90.

[0012] The processing container 10 houses the substrate holder 20 and the like. The side wall of the processing container 10 is provided with a gate 12 and a gate valve 13 for opening and closing the gate 12. The substrate W is transported into the processing container 10 through the gate 12 by a transport device (not shown). Next, the substrate W is processed with a processing liquid inside the processing container 10. After that, the substrate W is transported out of the processing container 10 through the gate 12 by the transport device.

[0013] The substrate holding section 20 is provided inside the processing container 10 and holds the substrate W horizontally. The substrate holding section 20 has, for example, claws 21 that hold the outer periphery of the substrate W. Multiple claws 21 are provided at equal intervals in the circumferential direction of the substrate W. Although not shown in the figures, the substrate holding section 20 may also use vacuum suction to hold the lower surface of the substrate W.

[0014] The substrate rotation unit 25 rotates the substrate holding unit 20, thereby rotating the substrate W together with the substrate holding unit 20. The substrate holding unit 20 holds the substrate W so that the rotational center line of the substrate W coincides with the center of the surface Wa of the substrate W.

[0015] The supply unit 31 supplies a processing liquid to the surface Wa of the substrate W via the nozzle 41. The supply unit 31 has, for example, a common line 31a connected to the nozzle 41, a plurality of individual lines 31b branched from the common line 31a, and devices 31c provided for each individual line 31b. The devices 31c have, for example, an on-off valve, a flow meter, and a flow controller. The nozzle 41 discharges a plurality of processing liquids in sequence, but the nozzle 41 may be provided for each type of processing liquid, and the number of nozzles 41 may be plural.

[0016] The processing liquid is, for example, HF (hydrogen fluoride), IPA (isopropyl alcohol), and DIW (deionized water). HF is supplied in the form of an aqueous solution. The HF aqueous solution is generally called hydrofluoric acid. The HF concentration in the HF aqueous solution is, for example, 40% to 65% by mass. The nozzle 41 may discharge a mixture of a plurality of processing liquids, for example, a mixture of an HF aqueous solution and IPA. The supply unit 31 may have a mixing device (not shown) that mixes the HF aqueous solution and IPA.

[0017] The moving unit 51 moves the nozzle 41 in the horizontal and vertical directions. The moving unit 51 has, for example, an arm 51a and a turning mechanism (not shown). The turning mechanism moves the nozzle 41 in the horizontal direction by turning the arm 51a. Also, the turning mechanism moves the nozzle 41 in the vertical direction by raising and lowering the arm 51a. Note that the moving unit 51 may have a guide rail and a linear motion mechanism instead of the arm 51a and the turning mechanism. The linear motion mechanism moves the nozzle 41 in the horizontal and vertical directions along the guide rail.

[0018] The recovery unit 60 recovers the processing liquid supplied to the substrate W. The recovery unit 60 has, for example, a cup 61. The cup 61 surrounds the outer periphery of the substrate W held by the substrate holding unit 20 and receives the processing liquid splashed from the outer periphery of the substrate W. In this embodiment, the cup 61 does not rotate with the substrate holding unit 20, but it may rotate with the substrate holding unit 20. A drain pipe 62 and an exhaust pipe 63 are provided at the bottom of the cup 61. The drain pipe 62 discharges the liquid accumulated inside the cup 61. The exhaust pipe 63 discharges the gas accumulated inside the cup 61.

[0019] The control unit 90 is, for example, a computer and comprises an arithmetic unit 91 such as a CPU (Central Processing Unit) and a storage unit 92 such as memory. The storage unit 92 stores programs that control various processes performed in the substrate processing apparatus 1. The control unit 90 controls the operation of the substrate processing apparatus 1 by causing the arithmetic unit 91 to execute the programs stored in the storage unit 92.

[0020] As described above, the substrate processing apparatus 1 may be a batch type that processes multiple substrates W at once. A batch type substrate processing apparatus 1, although not shown in the figure, processes multiple substrates W at once by holding them vertically and immersing them in a processing liquid stored inside a processing tank. The batch type substrate processing apparatus 1 has a substrate holding unit that holds multiple substrates W and a supply unit that supplies the processing liquid to the substrates W by supplying the processing liquid into the processing tank.

[0021] Next, an example of a substrate W to be prepared will be described with reference to Figure 2. The substrate W has, for example, a base substrate W1 such as a silicon wafer, a titanium nitride film W2, a conductive film W3, a silicon nitride film W4, and a zirconium oxide film W5 in this order. Note that the laminated structure of the substrate W is not limited to the laminated structure shown in Figure 2. For example, the substrate W may have a functional layer (not shown) between the base substrate W1 and the titanium nitride film W2.

[0022] A titanium nitride film W2, a conductive film W3, a silicon nitride film W4, and a zirconium oxide film W5 are layered on a substrate W1 in this order. Openings OP are formed that penetrate the zirconium oxide film W5, the silicon nitride film W4, the conductive film W3, and the titanium nitride film W2. The openings OP are formed by dry etching, for example, using the zirconium oxide film W5 as a hard mask. The openings OP are, for example, trenches.

[0023] The application of the substrate W is not particularly limited, but for example, it is used for semiconductor memory such as DRAM. In this case, the titanium nitride film W2 is the bit line contact, and the conductive film W3 is the bit line. The titanium nitride film W2 may or may not contain silicon (Si). The conductive film W3 includes, for example, a Ru film, a W film, or a Mo film, and preferably a Ru film. The conductive film W3 may be composed of multiple films, for example, a TiSiN film and a Ru film may be present on the titanium nitride film W2 in this order. The silicon nitride film W4 is a protective film that protects the conductive film W3.

[0024] The substrate processing apparatus 1 removes the unwanted zirconium oxide film W5 after the formation of the opening OP. The substrate processing apparatus 1 selectively etches the zirconium oxide film W5 from among the multiple films W2 to W5 exposed on the surface Wa of the substrate W by supplying an etching solution to the surface Wa of the substrate W. This makes it possible to remove the zirconium oxide film W5 while suppressing pattern deformation.

[0025] Incidentally, sulfuric acid is generally used as an etching solution for the zirconium oxide film W5, as described in Patent Document 1. However, sulfuric acid also etches the titanium nitride film W2. Therefore, using sulfuric acid has the problem of destroying the uneven pattern of the substrate surface Wa. It is also conceivable to use dilute hydrofluoric acid (DHF), which is obtained by diluting hydrofluoric acid (HF aqueous solution, HF concentration 40% to 65% by mass) with water, but DHF has the problem of completely removing the silicon nitride film W4 before completely removing the zirconium oxide film W5.

[0026] Therefore, in this embodiment, hydrofluoric acid (HF aqueous solution, HF concentration 40% to 65% by mass) diluted with an organic solvent is used as the etching solution. The etching solution contains, for example, 0.7% to 6.5% by mass of hydrogen fluoride (HF), 87.0% to 98.6% by mass of an organic solvent, and 0.7% to 6.5% by mass of water. It is preferable that the water content in the etching solution be as low as possible. If it is possible to prepare pure HF instead of an HF aqueous solution, it is preferable that the water content in the etching solution be 0.0% by mass.

[0027] Unlike Patent Document 1, by using hydrofluoric acid instead of sulfuric acid, etching of the titanium nitride film W2 can be suppressed, and the collapse of the uneven pattern can be prevented. Also, unlike Patent Document 2, by diluting hydrofluoric acid with an organic solvent instead of water, etching of the silicon nitride film W4 can be suppressed.

[0028] The equilibrium state of HF in an aqueous solution of HF is as follows: HF⇔H + +F - HF + H2O ⇔ H3O + +F - HF+F - ⇔HF2 - .

[0029] HF2 - HF is an etching factor for both the silicon nitride film W4 and the zirconium oxide film W5. Undissociated HF is an etching factor for the zirconium oxide film W5. Therefore, by increasing the amount of undissociated HF in the treatment solution, the etching selectivity ratio of the zirconium oxide film W5 to the silicon nitride film W4 (etching rate of W5 / etching rate of W4) can be increased. Increasing the amount of undissociated HF can be achieved by increasing the HF concentration in the etching solution, but this method has limitations because the amount of SiN etching increases accordingly.

[0030] In solvents with high dielectric constants (high polarization), such as DIW, solvation occurs, and HF becomes F - Or HF2- It can take an ionic state such as this. On the other hand, in a solvent with a low dielectric constant (small polarization) like an organic solvent, solvation is less likely to occur, and HF takes a non-dissociated state. In this embodiment, by utilizing this phenomenon, hydrofluoric acid is diluted with an organic solvent to increase the amount of non-dissociated HF and enhance the etching selectivity ratio of the zirconium oxide film W5 to the silicon nitride film W4 (etching rate of W5 / etching rate of W4).

[0031] The organic solvent constituting the etching solution may be any one that is compatible with water and has a lower relative dielectric constant than water, and is not particularly limited. For example, it contains IPA, EG (ethylene glycol), acetic acid, ethanol, or methanol. The relative dielectric constant of the organic solvent is preferably 1 / 2 or less of the relative dielectric constant of DIW. The relative dielectric constant of IPA is about 1 / 4 of the relative dielectric constant of DIW.

[0032] Next, referring to FIG. 4, an example of the relationship between the mixing ratio of the etching solution and the etching rate of the zirconium oxide film W5 will be described. In FIG. 4, the mixing ratio indicates the volume ratio of the HF aqueous solution with a HF concentration of 50 wt% to the organic solvent (HF aqueous solution: organic solvent). In FIG. 4, the greater the slope of the straight line, the greater the etching rate of the zirconium oxide film W5. From R1 to R4 shown in FIG. 4 or from R5 to R6 shown in FIG. 4, it can be seen that the higher the HF content, the faster the etching rate of the zirconium oxide film W5. Also, from R3 and R6 shown in FIG. 4, when the volume ratio of the HF aqueous solution and the organic solvent is the same, it can be seen that IPA has a faster etching rate than EG as the organic solvent.

[0033] Next, with reference to Figure 5, an example of the relationship between film type (TiN, TiSiN, SiN) and the etching rate of the film will be explained. In Figure 5, R1 shown in Figure 4 was used as the etching solution. In Figure 5, "upper limit" is the upper limit of etching amount at which the uneven pattern does not collapse. In Figure 5, the white circles indicate the etching amount of SiN when DHF (dilute hydrofluoric acid) is used as the etching solution. From Figure 5, it can be seen that the collapse of the uneven pattern can be suppressed by using an aqueous solution of HF diluted with an organic solvent as the etching solution.

[0034] Incidentally, as mentioned above, the etching solution contains an organic solvent. Therefore, it is preferable that the zirconium oxide film W5 contains an organic substance in order to improve the etching rate. The organic substance is derived, for example, from an organozirconium compound. The zirconium oxide film W5 can be formed by applying a solution in which an organozirconium compound is dissolved in an organic solvent, drying it, and then firing it.

[0035] When supplying the etching solution, the temperature of the substrate W is, for example, 50°C or lower, preferably 30°C or lower. When using hydrofluoric acid diluted with an organic solvent as the etching solution, unlike when using sulfuric acid, heating of the substrate W is unnecessary. When supplying the etching solution, the temperature of the substrate W only needs to be above room temperature, for example 5°C or higher, preferably 20°C or higher.

[0036] Next, with reference to Figure 3, a substrate processing method according to one embodiment will be described. The substrate processing method includes steps S101 to S107, as shown in Figure 3, for example. Steps S101 to S107 are performed under the control of the control unit 90. Processing from step S101 onward begins when a transport device (not shown) brings the substrate W into the processing container 10.

[0037] Note that the substrate processing method does not have to include all of steps S101 to S107, and may include at least steps S101 and S103. Below, we will describe the case in step S103 in which IPA is used as the organic solvent constituting the etching solution. In steps S102, S103 and S104, the same organic solvent is preferably used, but different organic solvents may be used.

[0038] First, the substrate holder 20 holds the substrate W horizontally with its surface Wa facing upwards (step S101). The substrate holder 20 holds the substrate W so that the rotational centerline of the substrate W passes through the center of the surface Wa of the substrate W. Then, the substrate rotation unit 25 rotates the substrate W together with the substrate holder 20. Hereafter, the surface Wa of the substrate W may be referred to as substrate surface Wa.

[0039] While the substrate W is rotating, steps S102 to S107 are performed on the substrate surface Wa. First, the nozzle 41 supplies IPA to the substrate surface Wa (step S102). The nozzle 41 supplies IPA to the center of the substrate surface Wa. The IPA flows radially outward from the substrate surface Wa due to centrifugal force, forming a liquid film over the entire substrate surface Wa.

[0040] Next, the nozzle 41 supplies the etching solution to the substrate surface Wa (step S103). The etching solution contains HF and IPA, and is an aqueous solution of HF diluted with IPA. The nozzle 41 supplies the etching solution to the center of the substrate surface Wa. The etching solution flows radially outward from the substrate surface Wa by centrifugal force, replacing the IPA remaining on the substrate W, and forms a liquid film over the entire substrate surface Wa.

[0041] Next, nozzle 41 supplies IPA to the substrate surface Wa (step S104). Nozzle 41 supplies IPA to the center of the substrate surface Wa. The IPA flows radially outward from the substrate surface Wa by centrifugal force, replacing the etching solution remaining on the substrate W, and forms a liquid film over the entire substrate surface Wa.

[0042] Next, the nozzle 41 supplies a mixture of IPA and DIW to the substrate surface Wa (step S105). The nozzle 41 supplies the mixture of IPA and DIW to the center of the substrate surface Wa. The mixture of IPA and DIW flows radially outward from the substrate surface Wa by centrifugal force, replacing the IPA remaining on the substrate W, and forms a liquid film over the entire substrate surface Wa. In step S104, the IPA content may be gradually or continuously reduced and the DIW content may be gradually or continuously increased over time.

[0043] Next, nozzle 41 supplies DIW to the substrate surface Wa (step S106). Nozzle 41 supplies pure DIW to the center of the substrate surface Wa. The DIW flows radially outward from the substrate surface Wa by centrifugal force, replacing the IPA remaining on the substrate W, and forms a liquid film over the entire substrate surface Wa. By supplying pure DIW, fluoride ions originating from the etching solution can be removed.

[0044] After all the processing liquid has been supplied, the substrate rotating unit 25 rotates the substrate W together with the substrate holding unit 20 to spin-dry the substrate W (step S107). When spin-drying the substrate W, IPA may be supplied again after the DIW is supplied, and a liquid film of IPA may be formed on the substrate surface Wa. Since IPA has a lower surface tension than DIW, the collapse of the uneven pattern can be suppressed. The drying method for the substrate W is not limited to spin drying, and may also be hydrophobic drying using a silylating agent or supercritical drying, for example.

[0045] According to this embodiment, a substantially water-free organic solvent is supplied to the substrate surface Wa at least before and after (both in Figure 3) the supply of the etching solution (step S103). In this specification, "substantially water-free" of the organic solvent means that the water content is 0.0% by mass to 3.0% by mass.

[0046] If an organic solvent is supplied to the substrate surface Wa in step S102, prior to step S103, the etching solution will be more likely to wet the substrate surface Wa in step S103. The reason for using an organic solvent that is substantially free of water is to suppress the etching of the silicon nitride film W4 by the effect of water remaining on the substrate W in step S103.

[0047] In step S104, following step S103, an organic solvent is supplied to the substrate surface Wa to remove any etching solution remaining on the substrate W. The reason for using an organic solvent that is substantially free of water is to suppress the etching of the silicon nitride film W4 by the HF and water remaining on the substrate W in step S104.

[0048] Furthermore, according to this embodiment, after supplying the etching solution (step S103), the following steps are performed in this order: supplying an organic solvent that substantially does not contain water to the substrate surface Wa (step S104), supplying a mixture of the organic solvent and water to the substrate surface Wa (step S105), and supplying pure water to the substrate surface Wa (step S106). This allows the composition of the liquid film to be changed step by step from an organic solvent to pure water.

[0049] While embodiments of the substrate processing method and substrate processing apparatus relating to this disclosure have been described above, this disclosure is not limited to the above embodiments. Various changes, modifications, substitutions, additions, deletions, and combinations are possible within the scope of the claims. These, too, naturally fall within the technical scope of this disclosure.

[0050] This application claims priority based on Japanese Patent Application No. 2022-135695, filed with the Japan Patent Office on August 29, 2022, and the entire contents of Japanese Patent Application No. 2022-135695 are incorporated herein by reference. [Explanation of symbols]

[0051] 1. Substrate processing device 20 Board holding part 25. Circuit board rotating part 31 Supply section 90 Control Unit W board W2 Titanium Nitride Film W5 Zirconium oxide film Wa surface

Claims

1. Prepare a substrate having a surface in which a titanium nitride film and a zirconium oxide film are exposed, By supplying an etching solution containing hydrogen fluoride and an organic solvent to the surface of the substrate, the zirconium oxide film is selectively etched from the titanium nitride film and the zirconium oxide film. It has, The process involves, in this order, supplying an organic solvent substantially free of water to the surface of the substrate after supplying the etching solution, supplying a mixture of the organic solvent and water to the surface of the substrate, and supplying pure water to the surface of the substrate. Substrate processing method.

2. A silicon nitride film is further exposed on the surface of the substrate. The substrate processing method according to claim 1, comprising supplying the etching solution to the surface of the substrate to selectively etch the zirconium oxide film among the titanium nitride film, the silicon nitride film, and the zirconium oxide film.

3. A conductive film, a silicon nitride film, and a zirconium oxide film are laminated on the titanium nitride film in this order. The substrate processing method according to claim 2, wherein an opening is formed that penetrates the zirconium oxide film, the silicon nitride film, the conductive film, and the titanium nitride film.

4. The substrate processing method according to claim 3, wherein the conductive film includes a Ru film, a W film, or a Mo film.

5. The substrate processing method according to any one of claims 1 to 4, wherein the etching solution contains 0.7% to 6.5% by mass of hydrogen fluoride, 87.0% to 98.6% by mass of an organic solvent, and 0.7% to 6.5% by mass of water.

6. The substrate processing method according to any one of claims 1 to 4, wherein the zirconium oxide film contains an organic substance.

7. The substrate processing method according to any one of claims 1 to 4, wherein the etching solution contains isopropyl alcohol (IPA), ethylene glycol, acetic acid, ethanol, or methanol as an organic solvent.

8. The substrate processing method according to any one of claims 1 to 4, wherein the temperature of the substrate is 50°C or lower when the etching solution is supplied.

9. A substrate holding part that holds a substrate having a surface in which a titanium nitride film and a zirconium oxide film are exposed, A supply unit supplies an etching solution containing hydrogen fluoride and an organic solvent to the surface of the substrate held in the substrate holding unit, thereby selectively etching the zirconium oxide film from the titanium nitride film and the zirconium oxide film. Equipped with, The substrate processing apparatus comprises a supply unit that, after supplying the etching solution, supplies an organic solvent substantially free of water to the surface of the substrate, then supplies a mixture of the organic solvent and water to the surface of the substrate, and then supplies pure water to the surface of the substrate.

Images