Etchant, method for processing substrate by using the same, method for manufacturing semiconductor device, and etching rate adjusting agent

Abstract

To provide an etching solution with a high etching selectivity of silicon carbonitride to silicon and silicon oxide, a method for processing a substrate including the step of bringing the etchant in contact with the substrate, and a method for manufacturing a semiconductor device including the step of processing the substrate.SOLUTION: There is provided an etchant for etching silicon carbonitride containing phosphoric acid, water, cerium ions, and an Si source. Further, there is provided a method for processing a substrate, including the step of bringing the etchant into contact with a substrate which has a silicon carbonitride film and contains silicon. Furthermore, there is provided a method for manufacturing a semiconductor device including the method for processing.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to an etching solution for etching silicon carbonitride. The present invention also relates to a method for treating a substrate using the etching solution. The present invention also relates to a method for manufacturing a semiconductor device using the etching solution. The substrate includes a semiconductor wafer, a silicon substrate, or the like. The present invention also relates to an etching rate adjuster. [Background technology]

[0002] Various materials are used in the manufacturing process of semiconductor devices, among which silicon nitride and silicon carbonitride are known to be useful in various fields such as copper diffusion barrier films, passivation films, etch stop films, surface protection films, and gas barrier films. For example, silicon nitride films (SiN films, silicon nitride films) and silicon carbonitride films (SiCN films, silicon carbonitride films) are formed and used on substrates such as silicon wafers and processed bodies thereof. Here, silicon carbonitride also includes compounds that further contain hydrogen and oxygen in addition to compounds consisting of a skeleton of silicon, carbon, and nitrogen, as shown in Non-Patent Document 1, for example.

[0003] In forming semiconductor patterns, it is sometimes necessary to etch a silicon nitride film or a silicon carbonitride film formed on a substrate while avoiding etching a silicon oxide film or a silicon wafer.

[0004] A phosphoric acid solution is generally used to etch silicon nitride, but unlike silicon nitride, silicon carbonitride is hardly etched with a phosphoric acid solution.

[0005] Regarding the method of etching silicon carbonitride films, a method using a composition containing an oxidizing agent, a fluorine compound, and water has been proposed (Patent Document 1), but the etching rate of silicon carbonitride described in the examples is less than 250 Å / 30 min, which is not a sufficient rate. Moreover, such a composition also etches silicon oxide films (SiO2 films, silicon oxide films). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2007-049145 A [Non-patent literature]

[0007] [Non-Patent Document 1] ECS Journal of Solid State Science and Technology, 8 (6) P346-P350 (2019) Summary of the Invention [Problem to be solved by the invention]

[0008] In the manufacture of semiconductor devices, the use of silicon carbonitride films provides superior performance, but as described above, there is no etching solution that can sufficiently etch silicon carbonitride selectively to silicon and silicon oxide, and the situations in which it is used are extremely limited. Therefore, an object of the present invention is to provide an etching solution having a high etching selectivity ratio of silicon carbonitride to silicon and silicon oxide, a method for treating a substrate including a step of contacting the substrate with the etching solution, and a method for manufacturing a semiconductor device including the method for treating the substrate. [Means for solving the problem]

[0009] In view of the above problems, the present inventors have conducted extensive research into a composition capable of selectively etching silicon carbonitride. As a result, they have found that by further adding cerium ions to an aqueous phosphoric acid solution that has been conventionally used for selective etching of silicon nitride, the etching rate of silicon carbonitride can be significantly improved without substantially changing the etching rate of silicon oxide. However, when this etching solution is used, silicon is etched to the same extent as silicon carbonitride. Therefore, they have found that the etching rate of silicon can be suppressed by further adding a Si source to the etching solution, and have completed the present invention.

[0010] That is, the present invention relates to the following. [1] An etching solution for etching silicon carbonitride, comprising phosphoric acid, water, cerium ions and a Si source. [2] The etching solution according to [1], wherein the content of cerium ions contained in the etching solution is 0.001 mol / L or more and 0.2 mol / L or less. [3] The etching solution according to [1] or [2], further comprising sulfuric acid. [4] The etching solution according to any one of [1] to [3], which is an etching solution used in the manufacture of a semiconductor device. [5] The etching solution according to any one of [1] to [4], which does not contain cerium dioxide. [6] A method for treating a substrate, comprising the step of contacting a substrate having a silicon carbonitride film and containing silicon with the etching solution according to any one of [1] to [5]. [7] A method for manufacturing a semiconductor device, comprising the method for treating a substrate according to [6]. [8] An etch rate modifier comprising water, cerium ions, and a Si source for addition to an etching solution containing phosphoric acid. [9] The adjuster according to [8], further comprising sulfuric acid.

[10] An etch rate modifier comprising water and cerium ions for addition to an etching solution comprising a Si source and phosphoric acid.

[11] The adjuster according to

[10] , further comprising sulfuric acid.

[12] The adjuster according to any one of [8] to

[11] , which does not contain cerium dioxide. Effect of the Invention

[0011] According to the present invention, silicon carbonitride can be selectively etched compared to silicon and silicon oxide by using an etching solution containing phosphoric acid, water, cerium ions, and a Si source.

[0012] Furthermore, the etching solution according to one embodiment of the present invention can also etch silicon nitride in a manner similar to that of a conventional aqueous phosphoric acid solution, and therefore the same etching solution can be used for both the process of selectively etching silicon carbonitride and the process of selectively etching silicon nitride, thereby reducing the effort required to manage a plurality of types of etching solutions, as necessary. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] First Embodiment (etchant) The etching solution according to the first embodiment of the present invention contains phosphoric acid, water, cerium ions, and a Si source, and is used for etching silicon carbonitride.

[0014] The content of phosphoric acid in the etching solution of this embodiment may be in the same range as that of the conventionally known etching solutions for silicon nitride. Specifically, it is preferably 50% by mass or more and 98% by mass or less, more preferably 55% by mass or more and 96% by mass or less, and particularly preferably 60% by mass or more and 94% by mass or less. Etching of silicon carbonitride is advantageously performed at a high temperature because the etching rate is faster. The higher the proportion of phosphoric acid, the more stable the use at high temperatures. On the other hand, water, cerium ions, and a Si source are essential for the etching solution of this embodiment, and it is not realistic to set the phosphoric acid content to more than 98 mass%. In this specification, when the blending amount of each component is described in mass%, the value is the proportion when the entire etching solution is taken as 100 mass%.

[0015] In a concentrated solution of phosphoric acid such as the etching solution of this embodiment, phosphoric acid is in equilibrium between orthophosphoric acid (H3PO4) and polyphosphoric acid in the solution, but the above content is the amount when the entire amount exists as orthophosphoric acid. The same applies when it exists as pyrophosphoric acid, etc.

[0016] The etching solution of this embodiment contains water as an essential component. If the amount of water is small, the etching rate of silicon tends to increase, and if the amount of water is too large, it tends to be difficult to use at high temperatures. Although it depends on the types and amounts of other components, the water content is preferably 0.5% by mass or more and 49% by mass or less, and more preferably 1% by mass or more and 29% by mass or less. Note that the amount of water in this case is the amount when all of the phosphoric acid is present as orthophosphoric acid.

[0017] The etching solution of the present embodiment contains cerium ions as an essential component. The presence of cerium ions in the etching solution significantly increases the etching rate of silicon carbonitride. Silicon carbonitride is hardly etched in phosphoric acid aqueous solution that does not contain cerium ions, which is thought to be due to the difference in polarity between Si-C bonds and Si-N bonds. The difference in electronegativity between Si atoms and C atoms is smaller than that of N atoms. Therefore, since the Si-C bond has a smaller polarization than the Si-N bond, it is difficult for an electrophilic addition reaction to occur with acid, and it is thought that etching of silicon carbonitride hardly progresses. On the other hand, when the etching solution contains cerium ions in addition to phosphoric acid aqueous solution, it is thought that the cerium ions act on the Si-C bond, causing etching of silicon carbonitride to progress.

[0018] The cerium ion may be present in the etching solution as a monoatomic ion or as a constituent atom of a complex ion (polyatomic ion). The valence of the cerium ion does not matter, but it is preferably trivalent or tetravalent. Cerium ions of different valences may be present in the etching solution.

[0019] In the etching solution of this embodiment, the content of cerium ions is preferably 0.001 mol / L or more and 0.25 mol / L or less, more preferably 0.002 mol / L or more and 0.2 mol / L or less, even more preferably 0.01 mol / L or more and 0.2 mol / L or less, and particularly preferably 0.02 mol / L or more and 0.2 mol / L or less. The higher the content of cerium ions, the higher the effect of promoting etching of silicon carbonitride. On the other hand, if the content of cerium ions becomes too high, a large amount of residues tend to accumulate on the substrate surface after etching, and the residues may not be removed even if a rinsing process described later is performed after etching. The mass ratio of cerium ions to phosphoric acid (cerium ions / phosphoric acid) contained in the etching solution of this embodiment is not particularly limited, but is preferably 0.0001 to 0.5, more preferably 0.001 to 0.3, and particularly preferably 0.005 to 0.2.

[0020] The etching solution of the present embodiment may contain counter ions derived from the compound (described later) used as the cerium ion source. Examples of the counter ions include inorganic ions such as fluorine ions, chlorine ions, bromine ions, sulfate ions, nitrate ions, carbonate ions, and hydroxide ions, and organic ions such as acetate ions and oxalate ions. In addition, when the cerium compound used is a double salt, ammonium ions derived therefrom may be contained.

[0021] The etching solution of the present embodiment preferably does not contain cerium dioxide. Cerium has extremely low solubility in an aqueous solution containing phosphoric acid, and does not dissolve, resulting in the formation of solid matter. The insoluble components in the solution may become a source of particles, which may cause uneven etching or lead to defects in the next process. Cerium compounds such as cerium acetate, cerium phosphate, and cerium carbonate also have low solubility in an aqueous solution containing phosphoric acid. For this reason, it is more preferable that the etching solution of this embodiment does not contain cerium acetate, cerium phosphate, cerium carbonate, or cerium dioxide.

[0022] The etching solution of this embodiment has a Si source as an essential component. The Si source is a silicic acid generating source, and specific examples of the Si source include silicon compounds, Si powder, SiN powder, Si wafers, and SiN wafers. Examples of silicon compounds include silicic acid, silicates, silica, alkoxysilanes such as tetraethoxysilane and tetramethoxysilane, and alkylsilanes such as methyltrimethoxysilane. Among these, silicic acid, silicates, silica, Si powder, SiN powder, Si wafers, and SiN wafers are preferred. As for the silicate, since it is preferable that the etching solution of the present invention does not contain metal as described later, it is preferable to avoid metal salts such as sodium silicate, and organic silicates such as tetramethylammonium silicate are preferred. As for the silica, any silicate that dissolves or disperses in the etching solution may be used, and colloidal silica is particularly preferred. It is considered that these Si sources generate silicic acid such as orthosilicic acid, metasilicic acid, and metadisilicic acid in the etching solution.

[0023] Silicic acid easily polymerizes when a proton is added to a silanol group to form a cation, and this cation electrophilically attacks another silicic acid. This is also thought to be the case for hydroxyl group terminals that are thought to be present on silicon substrates, and it is thought that silicic acid dissolved in the etching solution condenses with hydroxyl groups on the silicon substrate in an equilibrium reaction. Since the Si on the silicon substrate with silicic acid condensation is difficult to etch, it is thought that the etching of silicon can be suppressed by adding a silicon source to the etching solution in advance to make silicic acid present. In addition, since silicon carbonitride has a lower surface Si atom density than silicon, it is thought that the effect of physically inhibiting the approach of reactive species due to the condensation of silicic acid as described above is low.

[0024] In the etching solution of the present embodiment, the content of the Si source is not particularly limited, but is preferably 0.001 mass % or more and 1 mass % or less, more preferably 0.004 mass % or more and 0.5 mass % or less, and further preferably 0.007 mass % or more and 0.3 mass % or less, in terms of Si concentration. The mass ratio of the Si source to phosphoric acid (Si source / phosphoric acid) contained in the etching solution of this embodiment is not particularly limited, but is preferably 0.00001 or more and 0.02 or less, more preferably 0.00003 or more and 0.01 or less, and particularly preferably 0.00005 or more and 0.005 or less.

[0025] The etching solution of this embodiment preferably further contains sulfuric acid. The presence of sulfuric acid, which is an acid with a pKa lower than that of phosphoric acid, can suppress the etching rate of silicon and silicon oxide without impairing the etching rate of silicon carbonitride, and high selectivity can be obtained. The concentration of sulfuric acid is preferably 0.1 mass% or more and 45 mass% or less, more preferably 0.2 mass% or more and 40 mass% or less, and particularly preferably 0.5 mass% or more and 35 mass% or less. In addition, methanesulfonic acid, trifluoromethanesulfonic acid, nitric acid, hydrochloric acid, oxalic acid, etc. may be contained instead of sulfuric acid as an acid with a pKa lower than that of phosphoric acid.

[0026] The etching solution of this embodiment may further contain a dispersion stabilizer as a stabilizer for the Si source. Examples of the dispersion stabilizer include organic quaternary ammonium salts, organic quaternary phosphonium salts, surfactants, and the like. Specific examples include tetramethylammonium chloride, tetraethylammonium chloride, tetrabutylammonium chloride, tetrabutylphosphonium chloride, and decyltrimethylammonium chloride. By adding a dispersion stabilizer to increase the cation concentration in the etching solution, the silanol groups of silicic acid are converted to Si-O - It is believed that this stabilizes the silicate and inhibits the dehydration and condensation of silicic acid.

[0027] That is, the etching solution of this embodiment may contain ions and the like that are generated in the solution by adding these compounds.

[0028] (Impurities in the etching solution) The etching solution of the present embodiment may contain particles and trace amounts of metals as impurities. In terms of preventing contamination during etching, the particles are preferably 100 particles / mL or less, more preferably 50 particles / mL or less, and even more preferably 10 particles / mL or less, with a size of 200 nm or more. It is particularly preferable that when the solution is passed through a filter with a mesh size of 50 nm, all of the solution passes through the filter without any particles failing to pass through, and it is most preferable that all of the solution passes through a filter with a mesh size of 10 nm. From the viewpoint of preventing contamination of the etching target, it is preferable that the amount of metal impurities is as small as possible. The metal impurities referred to here refer to metals other than cerium, and specifically, it is preferable that the amount of each of Ag, Al, Ba, Ca, Cd, Cr, Cu, Fe, K, Li, Mg, Mn, Na, Ni, Pb, Zn, and Pr is each 1 ppm or less.

[0029] (Manufacturing method) The method for producing the etching solution of this embodiment is not particularly limited, and for example, the above-mentioned phosphoric acid, water, cerium compound, and Si source may be mixed to a predetermined concentration. Also, the etching solution may be produced by mixing an etching rate adjuster according to a second embodiment described later with an etching solution containing phosphoric acid. Also, the etching solution may be produced by mixing an etching rate adjuster according to a third embodiment described later with an etching solution containing phosphoric acid and a Si source. When a wafer is used as the Si source, phosphoric acid, water, and a cerium compound are mixed to a predetermined concentration, and then brought into contact with the wafer, thereby obtaining an etching solution containing the Si source.

[0030] It is preferable to use phosphoric acid having as little metallic impurities and insoluble impurities as possible, and if necessary, commercially available products can be used after purification by recrystallization, column purification, ion exchange purification, distillation, sublimation, filtration, etc. It is also preferable to use high-purity phosphoric acid manufactured and sold for semiconductor manufacturing.

[0031] It is also preferable to use water with high purity and few impurities. The amount of impurities can be evaluated by electrical resistivity, and specifically, electrical resistivity of 0.1 MΩ·cm or more is preferable, 15 MΩ·cm or more is more preferable, and 18 MΩ·cm or more is particularly preferable. Water with such few impurities can be easily manufactured and obtained as ultrapure water for semiconductor manufacturing. Furthermore, ultrapure water has extremely few impurities that do not affect (have little contribution to) electrical resistivity, making it highly suitable.

[0032] As the cerium ion source, a cerium compound having good solubility in an aqueous solution containing phosphoric acid can be used, for example, one or more of cerium hydroxide, cerium salt, and double salt containing cerium and a cation other than cerium (e.g., ammonium ion) can be used.

[0033] Furthermore, from the viewpoints of good solubility and ease of achieving high purification, it is preferable to use, as the cerium compound, cerium nitrate, cerium sulfate, ammonium cerium nitrate, ammonium cerium sulfate, etc. These may be hydrates.

[0034] On the other hand, when a cerium compound such as cerium dioxide, which has extremely low solubility in an aqueous solution containing phosphoric acid, is used, it does not dissolve in a solution containing phosphoric acid and water, and solid matter is generated instead of forming a homogeneous solution. The insoluble components in the solution may become a particle source, which may cause non-uniform etching or cause defects in the next process. That is, cerium compounds other than cerium dioxide are preferable as a cerium ion source used in producing the etching solution of this embodiment. In addition, cerium compounds such as cerium acetate, cerium phosphate, and cerium carbonate also have low solubility in an aqueous solution containing phosphoric acid. For this reason, cerium compounds other than cerium acetate, cerium phosphate, cerium carbonate, and cerium dioxide are more preferable as a cerium ion source.

[0035] It is preferable to use a cerium compound having as high a purity as possible, and if necessary, a commercially available product can be used after purification by recrystallization, column purification, ion exchange purification, filtration or the like.

[0036] The Si source may be one that generates silicic acid when added to the etching solution of the present embodiment. Examples of the silicon source include silicon compounds, Si powder, SiN powder, Si wafers, and SiN wafers. Examples of the silicon compounds include silicic acid, silicates, silica, alkoxysilanes such as tetraethoxysilane and tetramethoxysilane, and alkylsilanes such as methyltrimethoxysilane. Examples of the silicates include tetramethylammonium silicate. Examples of the silica include colloidal silica.

[0037] It is also preferable to use a Si source with as high purity as possible. For example, when tetramethylammonium silicate is used as the Si source, a high-purity product with few impurities can be obtained by dissolving high-purity Si powder in an aqueous solution of tetramethylammonium hydroxide (TMAH) manufactured and sold for semiconductor manufacturing, or by mixing the aqueous solution of TMAH with high-purity tetraethoxysilane (TEOS) to hydrolyze TEOS, and it is preferable to use such a high-purity product. In addition, it is preferable to remove ethanol generated in the latter manufacturing method using TEOS, but it may be added to the etching solution of this embodiment as a Si source in a state containing ethanol. When colloidal silica is used as the Si source, it is preferable to use a high-purity product manufactured and sold for semiconductor manufacturing, with a metal impurity concentration of 0.5 ppm or less.

[0038] As a method for adding the Si source to the etching solution of this embodiment, for example, the components other than the Si source may be mixed and dissolved, and then the Si source may be added with stirring at room temperature or under heating.

[0039] In the production of the etching solution of this embodiment, it is also preferable to remove particles by passing the mixture through a filter of several nm to several tens of nm after mixing and dissolving each component. If necessary, the filter passing process may be performed multiple times. In addition, various other processes known as a method for producing a chemical solution for semiconductor manufacturing can be performed.

[0040] (Application and method of use) The etching solution of this embodiment can be used for etching a substrate containing silicon carbonitride in the manufacture of a semiconductor device. The method of forming a silicon carbonitride film on a substrate is not limited, and a silicon carbonitride film formed by a known method such as a CVD method or a PVD method can be etched. In addition, a silicon carbonitride film used in the manufacture of a semiconductor device may contain hydrogen in an amount of up to 133 atomic % relative to silicon depending on the manufacturing method, and such a film containing hydrogen also falls under the silicon carbonitride to be etched using the etching solution of this embodiment. Furthermore, the silicon carbonitride to be etched may contain various impurity elements (e.g., oxygen) within the range normally contained.

[0041] Furthermore, the etching solution of the present embodiment can be used to treat a substrate having a silicon carbonitride film and containing silicon. The substrate may further have a silicon oxide film. By using the etching solution of the present embodiment, it is possible to selectively etch silicon carbonitride while suppressing etching of silicon and silicon oxide. Such selective etching was practically impossible with conventional etching solutions.

[0042] The substrate processing method will now be described in more detail.

[0043] A method for treating a substrate using the etching solution of the present embodiment includes a step of contacting a substrate having a silicon carbonitride film and containing silicon with the etching solution of the present embodiment, and preferably includes a treatment solution supply step of supplying the etching solution of the present embodiment to a main surface of the substrate while holding the substrate in a horizontal position and rotating the substrate around a vertical rotation axis passing through a center of the substrate.

[0044] In another preferred embodiment, a method for treating a substrate using the etching solution of the present embodiment includes a step of holding a plurality of substrates in an upright position and immersing the substrates in an upright position in the etching solution of the present embodiment stored in a treatment tank. In a preferred embodiment of the present invention, the etching solution is used in the manufacture of a semiconductor device, which includes the treatment method described above.

[0045] The temperature of the etching solution during etching using the etching solution of this embodiment may be appropriately determined from the range of 100 to 200° C. in consideration of the desired etching rate, surface state after etching, productivity, etc., and is preferably in the range of 130 to 180° C. At temperatures exceeding 200° C., damage may occur to semiconductor materials other than silicon carbonitride, and at temperatures below 100° C., it is difficult to etch silicon carbonitride at an industrially satisfactory rate.

[0046] When etching is performed using the etching solution of this embodiment, ultrasonic waves or the like may be used to accelerate the etching.

[0047] After the substrate treatment using the etching solution of this embodiment, if there are impurities remaining on the surface of the substrate, various known treatments may be performed to remove the impurities. For example, there is a method of performing a rinsing treatment on the substrate using a rinsing solution. Known rinsing solutions can be used, including acidic aqueous solutions such as hydrochloric acid, hydrofluoric acid, and sulfuric acid, alkaline aqueous solutions such as ammonia water, a mixture of hydrofluoric acid and hydrogen peroxide (FPM), a mixture of sulfuric acid and hydrogen peroxide (SPM), a mixture of ammonia water and hydrogen peroxide (APM), a mixture of hydrochloric acid and hydrogen peroxide (HPM), and the like. These may be used alone, or multiple rinsing solutions may be used in combination.

[0048] In the substrate processing method using the etching solution of this embodiment, the etching solution after processing the wafer may be collected and used for processing another wafer after performing a regeneration process such as filtering or adjusting the concentration of the etching solution components. A mechanism for adding fresh phosphoric acid or water while monitoring the concentration of phosphoric acid or water may be provided to adjust the concentration of the components. Water, hydrogen peroxide, or low-concentration phosphoric acid diluted with water may be used to adjust the moisture content.

[0049] Second Embodiment A second embodiment of the present invention is an etch rate modifier comprising water, cerium ions, and a Si source for addition to an etching solution comprising phosphoric acid. The adjuster of the present embodiment can be added to an etching solution containing phosphoric acid, and can improve the etching rate of silicon carbonitride while suppressing the etching rate of silicon when the etching solution is used. This makes it possible to suppress the etching rate of silicon compared to silicon carbonitride, and improve the selectivity of the etching solution.

[0050] Examples of the phosphoric acid-containing etching solution to which the adjuster of the present embodiment can be added include aqueous phosphoric acid solutions known as etching solutions for silicon nitride and / or silicon carbonitride, but are not particularly limited as long as they contain phosphoric acid. The etching solution containing phosphoric acid in this embodiment may contain sulfuric acid that may be contained in the etching solution according to one embodiment of the present invention, known components contained in etching solutions containing phosphoric acid as a main component, and impurities.

[0051] The types of cerium ions and Si source contained in the regulator of this embodiment may be the same as those in the etching solution of one embodiment of the present invention. The contents of water, cerium ions, and Si source in this embodiment may be changed as desired, as long as the contents of phosphoric acid, water, cerium ions, and Si source in the etching solution to which the regulator of this embodiment has been added are the same as those in the etching solution of one embodiment of the present invention.

[0052] The adjuster of the present embodiment may further contain impurities and known components contained in etching solutions containing sulfuric acid and phosphoric acid as main components. Known components and impurities contained in the etching solution containing phosphoric acid as a main component may be similar to those in the etching solution according to one embodiment of the present invention.

[0053] The method for producing the regulator of the present embodiment is not particularly limited, and the regulator can be produced in the same manner as the etching solution according to one embodiment of the present invention, except that no phosphoric acid is added.

[0054] By using the adjuster of this embodiment, the etching rate of silicon carbonitride can be improved while suppressing the etching rate of silicon. That is, another embodiment of the present invention is a method for treating a substrate having a silicon carbonitride film and containing silicon, comprising the steps of adding an etching rate adjuster containing water, cerium ions, and a Si source to an etching solution containing phosphoric acid, and contacting a substrate having a silicon carbonitride film and containing silicon with the etching solution to which the adjuster has been added.

[0055] <Third embodiment> A third embodiment of the present invention is an etch rate modifier comprising water and cerium ions for addition to an etching solution comprising phosphoric acid and a Si source. The adjuster of the present embodiment can be added to an etching solution containing phosphoric acid and a Si source, and can improve the etching rate of silicon carbonitride while suppressing an increase in the etching rate of silicon when the etching solution is used. This makes it possible to suppress the etching rate of silicon compared to that of silicon carbonitride, and improve the selectivity of the etching solution.

[0056] The etching solution containing phosphoric acid and a Si source to which the regulator of this embodiment can be added is, for example, an aqueous phosphoric acid solution known as an etching solution for silicon nitride and / or silicon carbonitride to which a Si source has been added, but is not particularly limited as long as it contains phosphoric acid and a Si source. Here, the Si source is the same as that described in one embodiment of the present invention. The etching solution containing phosphoric acid and a Si source in this embodiment may contain sulfuric acid that may be contained in the etching solution according to one embodiment of the present invention, known components contained in etching solutions containing phosphoric acid as a main component, and impurities.

[0057] The cerium ions contained in the regulator of this embodiment may be the same as those in the etching solution of one embodiment of the present invention. The contents of water and cerium ions in this embodiment may be changed as desired as long as the contents of phosphoric acid, water, cerium ions, and Si source in the etching solution to which the regulator of this embodiment has been added are the same as those in the etching solution of one embodiment of the present invention. .

[0058] The adjuster of the present embodiment may further contain phosphoric acid, sulfuric acid, known components contained in an etching solution mainly containing phosphoric acid, and impurities. Known components and impurities contained in the etching solution containing phosphoric acid as a main component may be similar to those in the etching solution according to one embodiment of the present invention.

[0059] The method for producing the regulator of the present embodiment is not particularly limited, and for example, the above-mentioned water and cerium compound may be mixed to a predetermined concentration.

[0060] By using the adjuster of this embodiment, the etching rate of silicon carbonitride can be improved while suppressing the increase in the etching rate of silicon. That is, another embodiment of the present invention is a method for treating a substrate having a silicon carbonitride film and containing silicon, comprising the steps of adding an etching rate adjuster containing water and cerium ions to an etching solution containing phosphoric acid and a Si source, and contacting a substrate having a silicon carbonitride film and containing silicon with the etching solution to which the adjuster has been added. EXAMPLES

[0061] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0062] [Comparative Example 1] (Method of preparing etching solution) Phosphoric acid, water, and cerium ammonium nitrate as a cerium compound were placed in a flask in the proportions shown in Table 1, and the flask was immersed in an oil bath whose temperature was set to the prescribed liquid temperature, and heated for 30 minutes while stirring the liquid at 600 rpm. The content of cerium ions in the etching solution was calculated from the amount of cerium ammonium nitrate added in Table 1, and is shown in Table 1.

[0063] (Method of Etching Rate Evaluation) A 2 x 1 cm silicon wafer (silicon carbonitride film) with a silicon carbonitride film was prepared, and the initial film thickness was measured using a spectroscopic ellipsometer. The silicon carbonitride film was immersed in 200 g of etching solution heated to a liquid temperature of 165°C for 4 minutes. The wafer was rinsed and dried, after which the film thickness was measured using a spectroscopic ellipsometer. The etching rate was calculated by calculating the amount of silicon carbonitride etched from the difference between the initial and post-treatment film thicknesses, and dividing this by the etching time. The results are shown in Table 2.

[0064] The etching rates of a 2 x 1 cm silicon wafer (silicon film) with a silicon film of (100) crystal plane and a 2 x 1 cm silicon wafer (silicon oxide film) with a silicon oxide film were calculated in the same manner as for the silicon carbonitride film, by immersing the silicon wafer for 10 minutes and the silicon oxide film for 10 minutes. The results are shown in Table 1.

[0065] From these measurement results, the etching selectivity (SiCN / Si) between the silicon carbonitride film and the silicon wafer was calculated, and the results are shown in Table 2.

[0066] [Comparative Examples 2 to 7, Examples 1 to 16] The etching solution used had the composition shown in Table 1, and the etching was performed in the same manner as in Comparative Example 1, except that the immersion time was changed so that the absolute amount of etching was similar to that in Comparative Example 1. The results are shown in Table 2. As the Si source, tetramethylammonium silicate solution manufactured by Aldrich was used in Examples 1 to 15, and colloidal silica PL-1 manufactured by Fuso Chemical Co., Ltd. was used in Example 16.

[0067] [Table 1] [Table 2]

[0068] In Examples 1 and 2 containing tetramethylammonium silicate as a Si source, the etching rate of silicon was greatly decreased in a dose-dependent manner with respect to the Si source, compared to Comparative Example 1, which had the same composition except that it did not contain a Si source. On the other hand, the etching rate of silicon carbonitride was almost unchanged, and the etching selectivity (SiCN / Si) between the silicon carbonitride film and the silicon wafer was greatly improved. Similarly, in Example 3 containing tetramethylammonium silicate, the etching rate of silicon was greatly decreased, compared to Comparative Example 4, which had the same composition except that it did not contain a Si source. Similarly, in Examples 4 to 6 containing tetramethylammonium silicate, the etching rate of silicon was greatly decreased in a dose-dependent manner with respect to the Si source, compared to Comparative Example 5, which had the same composition except that it did not contain a Si source. Moreover, as in Comparative Examples 1 to 3 and 5 to 7, when the content of the cerium compound is increased, the etching rate of silicon carbonitride increases, but the etching rate of silicon also increases, and SiCN / Si does not become sufficiently large. In contrast, in Examples 7 to 15 containing a Si source, the etching rate of the silicon carbonitride film increases while the etching rate of the silicon wafer remains suppressed. As a result, the etching selectivity (SiCN / Si) between the silicon carbonitride film and the silicon wafer is further improved. Moreover, Example 16 containing colloidal silica as the Si source also had a large SiCN / Si ratio, similar to Examples 1 to 15 containing tetramethylammonium silicate as the Si source. From the above results, it can be said that the etching solution according to one embodiment of the present invention has an excellent etching rate for silicon carbonitride, and has high selectivity for silicon carbonitride compared to silicon and silicon oxide.

Claims

1. An etching solution for etching silicon carbonitride, comprising phosphoric acid, water, cerium ions, and a Si source.

2. 2. The etching solution according to claim 1, wherein the content of cerium ions contained in the etching solution is 0.001 mol / L or more and 0.25 mol / L or less.

3. The etching solution according to claim 1 or 2, further comprising sulfuric acid.

4. The etching solution according to claim 1 or 2, which is an etching solution used in the manufacture of semiconductor devices.

5. 3. The etching solution according to claim 1, which does not contain cerium dioxide.

6. A method for treating a substrate, comprising the step of contacting a silicon-containing substrate having a silicon carbonitride film with the etching solution according to claim 1 or 2.

7. A method for manufacturing a semiconductor device, comprising the method for processing a substrate according to claim 6.

8. An etching rate modifier comprising water, cerium ions, and a Si source for addition to an etching solution containing phosphoric acid.

9. The conditioner of claim 8 further comprising sulfuric acid.

10. An etching rate modifier comprising water and cerium ions for addition to an etching solution comprising a Si source and phosphoric acid.

11. The conditioner of claim 10 further comprising sulfuric acid.

12. The conditioner according to any one of claims 8 to 11, which does not contain cerium dioxide.

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