JP2009177007A - Insulating film etching method - Google Patents

Abstract

An etching selectivity of an insulating film made of a metal oxide film or a metal silicon oxide film to a silicon oxide film or the like is improved.
An etching method includes a step (a) of processing an insulating film 3 formed on a substrate 5 made of metal oxide or metal silicon oxide into a predetermined shape by etching with a chemical solution, After (a), a step (b) of rinsing the exposed surface of the insulating film using a first cleaning liquid and a step (c) of drying the insulating film after the step (b) are provided. Furthermore, the etching rate of the insulating film can be improved by terminating the exposed surface of the insulating film with an OH group before or during the step (a).
[Selection] Figure 4

Description

  The present invention relates to an insulating film etching method used for, for example, a gate insulating film of a semiconductor device, and more particularly to lanthanoids and actinoids (La, Ce, Pr, Nd, Th) and other group 3 elements (Sc, Y). The present invention relates to a method for etching an insulating film made of a metal oxide film containing a group 4 element (Zr, Hf), a group 5 element (Ta), or the like.

  In the development of MOSFETs, investigations for thinning the gate insulating film have been actively conducted so far because of the demand for miniaturization and high integration of elements. However, the current technical level has reached an extremely thin gate insulating film thickness of several nanometers. To make an insulating film thinner than this, the reliability of the element is impaired due to an increase in leakage current, etc. There are concerns.

Under such circumstances, the application of a high dielectric constant film (High-k film) in addition to the conventional SiO ₂ film and SiON film is being studied in recent years. For example, materials such as Zr _x O _y , Hf _x O _y , Hf _x Si _y O _z , and Hf _x La _y O _z have been studied as materials for the high-k film, and these high dielectric constant films are used as transistors. When used as a gate insulating film, leakage current can be reduced while increasing gate capacitance.

On the other hand, in a memory element such as a DRAM and MEMS (Micro Electro Mechanical Systems), a technique for forming a capacitive film with a material having a higher dielectric constant is desired. Currently, materials such as Ta _x O _y are being studied.

  However, generally, metal oxidation of lanthanoid or actinoid La, Ce, Pr, Nd, Th and other group 3 elements Sc and Y, group 4 elements Zr and Hf, group 5 elements Ta Materials and metal silicon oxides are difficult to dissolve and remove chemically. Therefore, conventionally, a hydrofluoric acid-based chemical solution having a particularly high etching ability has been used as the etching solution (first conventional technology). In addition, the element group description in this specification shall be based on the periodic table of the present IUPAC system.

FIG. 10 is a diagram showing a conventional general chemical processing method. In the figure, after the chemical treatment step (1) for removing the metal oxide film, the metal silicon oxide film 107 and the like formed on the substrate 109 using the chemical solution 101 containing hydrofluoric acid or a salt thereof, the rinsing solution 103 is used. Etching is performed in the order of a rinsing step (2) using nitrogen and a drying step (3) performed by supplying nitrogen (N ₂ ) 105.

  However, when hydrofluoric acid or the like is used, the silicon oxide film used for the interlayer insulating film and STI (Shallow Trench Isolation) is also etched at the same time, which causes processing defects and characteristic defects. . Furthermore, the same applies when a metal oxide and a metal silicon oxide film are also formed on the back side or bevel portion of a semiconductor substrate. When removing these, a silicon oxide film used as a pollution prevention film or the like Will also be etched.

For example, in an aqueous solution of hydrofluoric acid 0.1% (weight%), if E _OX is the etching rate of the silicon oxide film and E _Me is the etching rate of the metal oxide film or the metal silicon oxide film,
Silicon oxide film SiO ₂ film (deposited at 1000 ° C.): E _OX = 8.0 nm / min
Metal oxide film LaO ₂ , HfO ₂ film: E _Me = 1.0 nm / min or less Selectivity (metal oxide film / silicon oxide film): E _Me / E _OX = 0.12
And E _Me / E _OX > 1 cannot be achieved.

Therefore, it is necessary to etch the metal oxide film or the metal silicon oxide film while suppressing the etching of the silicon oxide film. That is, it is required that at least E _Me / E _OX > 1.

  In order to solve this problem, in the second prior art, etching of the silicon oxide film is suppressed by preparing IPA (isopropyl alcohol) which is an organic chemical solution in a hydrofluoric acid chemical solution (for example, Patent Document 1).

Tables 1 to 6 in Patent Document 1 show experimental results on the etching rates of various insulating films when various etching solutions are used. As can be seen from these tables, when a mixed solution (unit:% by weight) of hydrofluoric acid 0.75% / IPA 97-98.5% / H ₂ O 0.75% is used, the metal silicon oxide film HfSiO _x For (Hf: Si = 4: 6) film,
Silicon oxide film SiO ₂ film: E _OX = 0.1 nm / min
Metal silicon oxide film HfO ₂ film: E _Me = 0.88 to 3.4 nm / min
Selectivity (metal oxide film / silicon oxide film): E _Me / E _OX = 8.8 to 34
And E _Me / E _OX > 1.
JP 2003-332297 A Integration Friendly Dual Metal Gate Technology Using Dual Thickness Metal Inserted Poly-Si Stacks (DT-MIPS), Hyung-Suk Jung, et al., Symp.VLSI Tech.p.196, 2007

However, in the second prior art, even if the etching solution disclosed in Patent Document 1 is used, for the HfO ₂ film that is a metal oxide film,
Silicon oxide film SiO ₂ film: SiO ₂ film: E _OX = 0.1 nm / min
Metal oxide film HfO ₂ film: E _Me = 0.04 nm / min
Selectivity (metal oxide film / silicon oxide film): E _Me / E _OX = 0.4
E _Me / E _OX > 1 is not achieved, and lanthanoid or actinoid La, Ce, Pr, Nd, Th and other Group 3 elements Sc and Y, Group 4 element Zr Hf and Hf are not effective for all metal oxides and metal silicon oxides of Ta group 5 elements.

Specifically, lanthanoid or actinoid La, Ce, Pr, Nd, Th and other group 3 elements Sc and Y, group 4 elements Zr and Hf, group 5 elements Ta A manufacturing process of a semiconductor manufacturing apparatus having a metal oxide film containing metal oxide and metal silicon oxide as a gate oxide film includes a gate forming process as shown in FIG. 11A (see Non-Patent Document 1). . FIG. 11B is a view showing an SEM photograph of the gate electrode patterned in the conventional semiconductor device. During the “Gate patterning” step in forming the gate, the gate oxide film (metal oxide film or metal silicon oxide film) will be etched. If there is no etching process that achieves E _Me / E _OX > 1, During the etching of the gate oxide film, the STI film composed of the silicon oxide film is etched more than the gate oxide film. As a result, processing defects and reliability defects occur in the semiconductor manufacturing apparatus.

In particular, a film having a high relative dielectric constant, such as a LaO ₂ film or a HfO ₂ film, has a very low etching rate, and further etches the metal oxide film or the metal silicon oxide film while suppressing the etching of the silicon oxide film. The solution of (realization of E _Me / E _OX > 1) is extremely difficult.

  In addition, when an organic solvent such as IPA is used, there is a concern about organic contamination in the semiconductor device manufacturing process. In addition, organic solvent chemicals are generally more expensive than water-soluble chemicals, and the equipment and facilities for manufacturing semiconductor devices must be exposed to radiation, making maintenance expensive and producing There are many problems in terms of cost.

  The present invention improves the etching selectivity of a metal oxide film or a metal silicon oxide film to a silicon oxide film and the like, and can be used for forming a gate insulating film of a semiconductor device, thereby reducing production costs. An object of the present invention is to provide an insulating film etching method.

  In order to solve the above-described problem, a first etching method for an insulating film of the present invention includes La, Ce, Pr, Nd, Th, Sc, Y, Zr, Hf, and Ta formed on a substrate. A step (a) of etching an insulating film made of a metal oxide or metal silicon oxide containing at least one element into a predetermined shape by using a chemical solution, and a first cleaning solution after the step (a) A step (b) of rinsing the exposed surface of the insulating film using a step, and a step (c) of drying the insulating film after the step (b), before the step (a) or the step In step (a), a step of terminating the exposed surface of the insulating film with an OH group is performed.

  According to this method, since the exposed surface of the insulating film is terminated with an OH group, the chemical solution spreads more quickly on the surface of the insulating film when etching is performed, so that the etching rate of the insulating film can be improved. On the other hand, since the silicon oxide film or the like has an OH group termination irrespective of the above-described processing, there is no change in the etching rate. Therefore, when a silicon oxide film or the like is provided on the substrate, the etching selectivity of the insulating film to the silicon oxide film or the like can be sufficiently increased. Therefore, by applying the etching method of the present invention to the formation of the gate electrode and gate insulating film of a MOS transistor, for example, the gate insulating film made of a metal oxide film or a metal silicon oxide film is not affected by the element isolation insulating film. Can be formed.

  In particular, the step of terminating the exposed surface of the insulating film with an OH group is preferably performed during the step (a). Etching with a chemical solution replaces the OH group end of the insulating film with a hydrophobic end, so that the etching rate of the insulating film decreases with time. Therefore, the etching rate of the insulating film can be improved again by performing the OH group termination treatment of the insulating film after the etching with the chemical solution.

  As a chemical solution for etching, a solution containing hydrofluoric acid or a salt thereof is preferably used.

  In addition, since the chemical solution is water-soluble, the cost required for production facilities can be reduced as compared with the case where an organic chemical solution is used, and the insulating film is not contaminated by organic substances.

  The second etching method for an insulating film of the present invention is a process (a) of etching an insulating film made of a metal oxide or a metal silicon oxide formed on a substrate into a predetermined shape by using a chemical solution. And a step (b) of rinsing the exposed surface of the insulating film using a cleaning liquid after the step (a), and a step (c) of drying the insulating film after the step (b). The chemical solution is a water-soluble chemical solution containing hydrofluoric acid or a salt thereof and mixed with an acidic drug that lowers the pH.

  According to this method, the pH (or pKa) can be reduced by mixing the acidic chemical compared with the conventional chemical solution for etching, so that the metal oxide film and the metal silicon oxide film are etched with respect to the silicon oxide film or the like. The selection ratio can be improved. In addition, since the chemical solution is water-soluble, the cost required for production facilities can be reduced as compared with the case where an organic chemical solution is used, and the insulating film is not contaminated by organic substances.

According to the insulating film etching method of the present invention, the etching rate (E _Me ) of the metal oxide film or the metal silicon oxide film is greatly improved as compared with the prior art, and the silicon oxide film of the metal oxide film or the metal silicon oxide film The etching selectivity with respect to the above can be sufficiently increased.

  Features of the present invention include lanthanoids and actinides (La, Ce, Pr, Nd, Th) and other Group 3 elements (Sc, Y), Group 4 elements (Zr, Hf), and Group 5 elements (Ta) A step of forming an OH group termination on the surface of the metal oxide film or the metal silicon oxide film before or during the chemical etching when the metal oxide and the metal silicon oxide film are etched (hereinafter referred to as an OH group termination forming step). And a water-soluble chemical solution obtained by mixing a chemical solution containing hydrofluoric acid or a salt thereof with an acidic chemical solution that induces pH in the acidic region.

  Here, as a chemical solution used for etching, the technical significance of mixing an acidic chemical solution that induces a pH in an acidic region with a chemical solution containing hydrofluoric acid or a salt thereof will be described.

  FIG. 1A is a diagram showing the pH dependency of the etching rate of the metal oxide film, and FIG. 1B is a diagram showing the pH dependency of the etchant presence rate in the hydrofluoric acid aqueous solution. In FIG. 1A, an amorphous metal oxide film is a film that has not been heat-treated after being formed by the MOCVD method, and a metal oxide film having improved crystallinity is a film that has been crystallized by being heat-treated after formation. . In addition to these MOCVD methods, these experimental results include ALD-CVD methods, PVD methods, thermal CVD methods, LP-CVD methods, photo-CVD methods, plasma CVD methods, Cat-CVD methods, vapor deposition methods, and film formation methods. The method can be applied to a metal oxide film formed by an epitaxial method or the like as a method for imparting crystallinity immediately thereafter.

  As can be seen from FIG. 1A, the etching rate of the amorphous metal oxide film (metal silicon oxide film) increases as the pH of the chemical solution decreases from pH 5 to pH 2, and is almost saturated around pH 2-3. .

On the other hand, in FIG. 1 (b), when the abundance ratio of the etchant in the hydrofluoric acid aqueous solution is seen, the abundance ratio of HF and H ₂ F ₂ increases as the pH of the chemical solution decreases from pH 5 to pH 2, Almost saturated. From this, it is considered that HF and H ₂ F ₂ contribute to the etching of the metal oxide film (metal silicon oxide film). It is estimated that HF ₂ ⁻ contributes to the etching of the silicon oxide film.

Therefore, from FIGS. 1A and 1B, the abundance of HF and H ₂ F ₂ increases as the acidity of the chemical increases, and the etching rate of the metal oxide film (metal silicon oxide film) improves. I understand.

FIG. 2 is a diagram showing the pH dependence of the selectivity of the metal oxide film to the thermal oxide film (th-SiO ₂ ) and the selectivity of the metal oxide film to the TEOS (Tetraethyl orthosilicate) film. A 0.1% HF solution was used as a chemical solution for etching, and hydrochloric acid (HCl) and ammonium hydroxide (ammonia water; NH ₄ OH) were used for pH adjustment. The selection ratio to the silicon oxide film of the metal oxide _film, the _{E Me} etching rate of the metal oxide _film, an _{E OX} in etching rate to the _E Me _{/ E OX} of silicon oxide film (thermal oxide film or a TEOS film) Desired.

As can be seen from FIG. 2, the selectivity E _Me / E _OX is maximized around pH 0.8 when the silicon oxide film is a thermal oxide film or a TEOS film. From these results, the pH of the chemical solution for etching may be 4.0 or less, preferably −1.0 or more and 4.0 or less, and more preferably 0 or more and 2 or less. I understand. Even when the concentration of hydrogen fluoride in the chemical solution was changed, the preferred pH range was the same.

Therefore, in the following embodiment, hydrogen chloride for lowering the pH is added to the hydrofluoric acid solution to obtain a pH value of 0.1% -HF / 3.7% -HCL / 96.2% -H ₂ O chemical is used. Of course, besides hydrogen chloride shown in the embodiment, phosphoric acid, hydrohalic acid such as hydrobromic acid and hydroiodic acid, or sulfuric acid, nitric acid, perchloric acid, fluorosulfonic acid, trifluoromethanesulfonic acid, etc. An acidic chemical solution such as a strong acid may be used as a drug for lowering the pH.

  Next, the reason (mechanism) that the effect is exhibited by adding the OH group termination forming step before or during the chemical etching in the process will be described.

  In general, the surface of a metal oxide film or metal silicon oxide film treated with a chemical solution with an acidic solution tends to be terminated with an H group. In particular, the surface treated with a chemical solution containing hydrofluoric acid is easily not only terminated with an H group but also terminated with an F group. Therefore, it is considered that the surface of the treated metal oxide film or metal silicon oxide film is in a state where there are few OH groups. In this way, on the surface with few OH group terminations and H group termination / F group termination, a hydrophobic action acts during etching, and the chemical etchant repels the treatment surface, making it difficult for the chemical solution to reach the treatment surface. Thus, it is considered that the progress of etching is inhibited.

  Therefore, since the surface of the metal oxide film or metal silicon oxide film before the start of etching has many hydrophilic OH group ends, the etching proceeds immediately after the start of etching, but thereafter, the OH group ends are H group ends and F groups end. It is replaced by the end, and the progress of the etching is gradually hindered, and the etching rate gradually decreases.

  Therefore, in the method of manufacturing a semiconductor device according to the present invention, by introducing the OH group termination forming step, the H group termination and F group termination of the processing surface that inhibits etching are replaced with the OH group termination, and the processing surface is etched. By recovering to the same state as before, it is presumed that a reduction in the etching rate can be prevented and a high etching rate can be obtained. However, even when the OH group termination formation step is performed before the etching step, there is an effect of increasing the OH group termination of the metal oxide film or the metal silicon oxide film and improving the etching rate.

  On the other hand, since the silicon oxide film always contains an OH group even after being exposed to the chemical solution, the silicon oxide film does not inhibit the progress of etching unlike the metal oxide film and the metal silicon oxide film, and the etching rate does not change.

Therefore, the metal oxide film or metal silicon oxide film is subjected to the OH group termination forming step during or before the etching process, thereby making the metal oxide film or metal silicon oxide film selection ratio E _Me / E _OX higher than the conventional method. Can also be increased.

In addition, it is not necessary to add an acidic chemical | medical solution, when the selectivity _EMe / _EOX > 1 can be achieved by introduce | transducing an OH group termination | terminus formation process, without adding an acidic chemical | medical solution to the chemical | medical solution for an etching. Of course, if an acidic chemical is added, the etching selectivity can be further improved.

  From the above, in the embodiment of the present invention, the metal oxide film or metal silicon oxide film having a high dielectric constant is etched in the following procedure.

FIG. 4 is a diagram illustrating an etching method according to an embodiment of the present invention. In the conventional etching method described above, the treatment is performed in the flow of the rinsing step and the drying step after the chemical treatment step using a chemical solution containing hydrofluoric acid or a salt thereof. On the other hand, in the following embodiment, as shown in FIG. 4, (2) a rinsing step and (3) a drying step are added as an “OH group termination forming step” in the etching step, and then the chemical treatment step again. It is characterized by implementing. In other words, in the etching process, two or more sets of combinations of the chemical treatment step and the subsequent OH group termination formation step are repeated. Here, the OH group termination formation step may be added a plurality of times in the etching process. In FIG. 4, reference numeral 1 indicates a chemical solution containing hydrogen fluoride or a salt thereof, reference numeral 3 indicates a metal oxide film or metal silicon oxide film, reference numeral 5 indicates a substrate, and reference numeral 7 indicates a cleaning liquid for rinsing. Reference numeral 8 denotes a gas such as N ₂ .

FIG. 3 is a diagram showing changes in the etching rate and selectivity of the metal oxide film or metal silicon oxide film depending on the number of OH group termination forming steps in the etching method of the present invention. Note that the selection ratio shown in FIG. 2 is significantly different from the selection ratio shown in FIG. 2, which shows the selection ratio of the metal silicon oxide film to th-SiO ₂ in FIG. 3, whereas FIG. This is because the selection ratio of the metal oxide film to th-SiO ₂ is shown.

  As shown in FIG. 3, by performing the OH group termination forming step a plurality of times in the etching step, both the etching rate and the selectivity can be gradually increased even if the total processing time of the chemical solution processing step is the same. I understand that. This is because the H group termination and the F group termination of the metal oxide film or the metal silicon oxide film proceed rapidly in seconds in the chemical treatment step, and etching is required to improve both the etching rate and the selectivity. While performing more OH group termination | terminus formation processes in a process, it is thought that it is preferable to shorten time of the chemical | medical solution processing step per time as much as possible. However, in actuality, if the number of repetitions of the chemical treatment step and the OH group termination formation process increases, the processing time of the entire etching process becomes longer and the operation becomes complicated. Therefore, the optimum OH in the actual gate electrode formation process, etc. What is necessary is just to select suitably the frequency | count of addition of a base termination formation process according to the design of a semiconductor device.

  Various other steps may be performed before and after the chemical solution treatment step and the added OH group termination formation process, and another step is inserted between the rinsing step and the drying step in the OH group termination formation process. May be.

Further, as the chemical for etching, it is preferable to use a water-soluble chemical obtained by mixing a chemical containing hydrofluoric acid or a salt thereof with an acidic chemical that lowers pH (or pKa; acid dissociation constant). When the effect of the selection ratio E _Me / E _OX > 1 can be obtained even with a chemical solution containing an acid or a salt thereof, an acidic chemical solution that lowers the pH of the chemical solution may not be added to the chemical solution.

(Embodiment)
An example of the etching method according to the embodiment of the present invention described above will be described. Note that the etching method of this embodiment is used, for example, when forming a gate insulating film of a MOS transistor. In this case, etching is performed after a mask is formed on a region where a gate electrode is formed in an insulating film made of a metal silicon oxide film or a metal oxide film. This mask may be formed after a polysilicon film, a metal silicide film, or a metal film as a gate electrode material is formed on the insulating film. Thereby, a gate insulating film and a gate electrode having a predetermined shape can be formed.

  FIG. 5A is a cross-sectional view showing an etching method according to a comparative example of this embodiment, and FIG. 5B is a cross-sectional view showing an etching method according to this embodiment.

First, as shown in FIG. 5B, an etching chemical 13 is supplied from above the metal silicon oxide film 15 made of, for example, HfSiO _x (Hf: Si = 4: 6) formed on the substrate 17 (see FIG. 5B). (1) Chemical solution supply step). For example, 0.1% -HF / 3.7% -HCl / 96.2% -H ₂ O (pH 0.8) is used as the chemical solution 13. In an actual semiconductor device manufacturing process, etching may be performed with the metal oxide film or metal silicon oxide film exposed, but the gate electrode material film is formed on the metal oxide film or metal silicon oxide film. Thereafter, the metal silicon oxide film 15 may be etched in the same process as the etching of the gate electrode material film. The medicinal solution treatment step is performed, for example, at 0 to 96 ° C. for 20 seconds. In this step, HfSiO _x (Hf: Si = 4: 6) is formed by MOCVD and then PDA (Post-Deposition anneal).

  Next, as a rinse step, a cleaning liquid 19 is supplied from above the metal silicon oxide film 15 to form OH group terminations on the surface (exposed surface) of the metal silicon oxide film 15 ((2) rinse step). Examples of the cleaning liquid 19 include pure water and those obtained by adding an oxidizing agent such as ozone.

Next, the exposed surface of the metal silicon oxide film 15 is dried while supplying an inert gas such as nitrogen (N ₂ ) 21 to the substrate 17 ((3) drying step).

  Next, the chemical solution 13 is again supplied to the metal silicon oxide film 15 at 0 to 96 ° C. for 40 seconds to process the metal silicon oxide film 15 ((4) chemical solution processing step).

  Next, a rinsing step and a drying step are performed under the same conditions as in steps (2) and (3) (steps (5) and (6); OH group termination formation step).

  By the above method, the metal silicon oxide film can be removed at a high etching rate and selectivity as described above. For this reason, for example, when the etching method of the present embodiment is used in the gate electrode formation process of the MOSFET, the gate insulating film can be formed in a relatively short time without affecting the silicon oxide film used for STI or the like. Become. Furthermore, since a water-soluble chemical solution is used, a semiconductor device can be manufactured at a lower cost than when an organic chemical solution is used. Further, when manufacturing a capacitor using a metal oxide film or a metal silicon oxide film as a capacitor film, the etching method of this embodiment can be used to form an interlayer insulating film, a contamination prevention film formed on a bevel portion of a wafer, or the like. It is possible to form a capacitor film having a desired shape without being affected. For this reason, if the etching method of this embodiment is used, it becomes possible to improve the yield of the semiconductor device provided with the metal oxide film and metal silicon oxide film which are high dielectrics.

  In addition, although this experiment was performed on the conditions of pH = 0.8, when performing the process of terminating the exposed surface of an insulating film by OH group, pH = -1.0 or more shown in FIG. The same effect can be obtained even under the condition of about 3.9 (about 4.0) which is the pH of the hydrofluoric acid aqueous solution as the upper limit.

  Next, specifically, in this embodiment, the effect of adding the OH group termination formation step to the etching step will be shown in comparison with the etching method in the case where the OH group termination formation step is not added.

As shown in FIG. 5A, the inventor of the present application uses the same chemical solution (0.1% -HF / 3.7% -HCl / 96.2% -H ₂ O (pH 0. 0) as in the etching method of the present embodiment. 8)), (1) a chemical solution treatment step for 60 seconds, (2) a rinse step, and (3) a drying step using N ₂ 21 to perform a metal silicon oxide film and a silicon oxide film (th-SiO ₂ ). The etching rate was measured and compared with the results of the etching method of this embodiment. The metal silicon oxide film to be etched was the same as the etching method of this embodiment.

  As a result of comparing the above two types of methods, as shown in FIG. 6A, in the etching method of the present embodiment, a rinse step that is an “OH group termination formation step” and a drying step are added. It was found that the etching rate was improved by 16% from 21.6 nm / min to 25.0 nm / min compared to the above method.

Moreover, as shown in FIG.6 (b), it turned out that 47% of selection ratio _EMe / _EOX also increases from 64 to 94 compared with the method of a comparative example. In addition, the result shown to Fig.6 (a), (b) is an average value of 4 examples for each method.

  From this, it was confirmed that the etching rate and the selectivity of etching can be improved by adding a rinsing step and a drying step, which are OH group termination forming steps, in the method of the present embodiment.

  Next, the effect of inducing the pH of the chemical solution in the present embodiment to an acidic region will be shown in comparison with the conventional etching method.

FIG. 7A is a view showing a conventional etching method using a chemical solution having a composition of 0.1% -HF / 99% -H ₂ O (pH 3.9), and FIG. _{% -HF / 3.7% -HCl / 96.2} % -H 2 O a (pH 0.8) is a diagram showing an etching method using a chemical solution. In either etching method, (1) a chemical solution treatment step for 60 seconds, (2) a rinsing step, and (3) a drying step are performed, and an additional OH group termination forming step is not performed. In addition, as the metal silicon oxide film to be etched, an HfSiO _x (Hf: Si = 4: 6) film formed by MOCVD and subjected to PDA (Post-Deposition anneal) was used.

FIGS. 8A and 8B are diagrams respectively showing the measurement results of the etching amount and the selectivity of the metal silicon oxide film in the etching method under the conditions shown in FIGS. 7A and 7B.
In the rinse step, pure water was used, and in the drying step, N ₂ was used. The result shown here is an average of 4 cases for each method.

  As shown in FIG. 8A, the etching rate when using a chemical solution with a low pH is 22 nm / min, an increase of 22% compared to the etching rate of 18 nm / min in the conventional etching method. I found out.

  Further, as shown in FIG. 8B, the selection ratio in the etching method using the chemical solution having a low pH is 64, which is 2.8 times as large as the selection ratio 23 in the conventional etching method. It turns out that it improves.

  Next, the results of examining the metal silicon oxide film formed by various methods and the etching selectivity of the metal oxide film to the silicon oxide film will be described.

9 (a) and 9 (b) show the case where (1) the chemical solution having a composition of 0.1% -HF / 99% -H ₂ O (pH 3.9) is used as described above. When 0.1% -HF / 3.7% -HCl / 96.2% -H ₂ O (pH 0.8) chemical solution is used, (3) the composition is 0.1% -HF / 3.7 % using a chemical _{-HCl / 96.2% -H 2 O (} pH0.8), it illustrates respectively etching amount and the selection ratio of the respective conditions of adding the OH group termination formation step.

From the results of FIGS. 9A and 9B, the metal oxide film has a lower etching rate than the metal silicon oxide film, but the etching chemical used in this embodiment is used (no OH group termination formation step). When the etching method of this embodiment is applied (there is an OH group termination formation step), the selectivity ratio E _Me / E _OX > 1 can be achieved for any metal oxide film formed by any method. confirmed. As for the metal oxide film, the film formed by the PVD (Physical Vapor Deposition) method tended to have higher etching rate and selectivity than the film formed by the ALD (Atomic Layer Deposition) method. In addition, when the etching chemical used in this embodiment is used (no OH group termination formation step) and when the etching method of this embodiment is applied (with OH group termination formation step), the presence or absence of the PDA treatment is determined. Regardless, the selection ratio E _Me / E _OX > 1 could be achieved. For the metal silicon oxide film and the metal oxide film, the etching method of this embodiment (with an OH group termination forming step) and the chemical solution used in this embodiment were used regardless of the film formation conditions and the presence or absence of PDA treatment. The etching rate and etching selectivity were high in the order of the etching method (no OH group termination step) and the conventional etching method.

  As described above, the etching method according to the present embodiment and the etching method using the chemical solution used in the etching method according to the present embodiment are selective to the metal silicon oxide film and the metal oxide film formed by any method. There is an effect to increase. The effect of the etching method of this embodiment is effective regardless of the presence or absence of the PDA treatment of the film. In addition, it is considered that the same result can be obtained for a metal silicon oxide film or a metal oxide film of a metal species other than Hf (La, Ce, Pr, Nd, Th, Sc, Y, Zr, Ta). Further, it is considered that the same result as described above can be obtained regardless of the presence or absence of the PDA treatment of the film.

In the etching method of the present embodiment, Ar, O ₂ , N ₂ O, or air may be used instead of N ₂ in the drying step. Further, N ₂ added with O ₂ or ozone (O ₃ ) may be used in the drying step. In this case, formation of OH termination can be further promoted. Moreover, you may dry using organic agents, such as IPA.

In the method of the present embodiment, an oxidizing agent may be added to either or both of the chemical solution used in the chemical treatment step and the cleaning solution used in the rinse step. In this way, the formation of the OH group terminal can be further promoted. As a specific example, H ₂ O ₂ is added as an oxidizing agent in an amount of 0.01% or more and 50% or less in an etching chemical solution or rinsing cleaning solution, or a chemical solution or a rinsing cleaning solution. It is preferable to add an arbitrary amount of ozone water having an ozone concentration of 10 mg / L or less.

  In addition, when the oxidizing agent is added to the chemical solution used in the chemical solution treatment step, even if etching is performed by a method that does not add both the rinse step and the drying step or either the rinse step and the drying step, An effect is obtained. In this way, the sequence of the etching process can be shortened.

  In addition, when adding an oxidizing agent to the washing | cleaning liquid used at a rinse step, an effect is acquired even if it does not add a drying step. Even in this case, the etching process sequence can be shortened.

In the OH group termination forming step of the present embodiment, after performing the rinsing step and the drying step, a step of performing plasma oxidation on the treatment surface under conditions of 600 ° C. or less may be further performed. In this way, the amount of OH group termination on the treated surface is increased, and the etching rate (E _Me ) and the selection ratio E _Me / E _{OX of the} metal oxide film or metal silicon oxide film are improved. An example in which this processing is added will be described with reference to the following table.

As shown in Table 1, in the etching method of this embodiment, the etching rate (E _Me ) of the metal oxide film or the metal silicon oxide film is 1.4 to 5 times that of the etching method according to the first prior art. ing. Moreover, the etching method of this embodiment is a metal oxide film compared with the second prior art disclosed in Patent Document 1, which uses an etching solution prepared by mixing an organic chemical solution IPA with a hydrofluoric acid chemical solution. Alternatively, the etching rate (E _Me ) of the metal silicon oxide film increases 25 to 70 times.

Furthermore, as shown in Table 2, according to the etching method of the present embodiment, the selection ratio E _Me / E _OX is 4 to 20 times that of the first conventional technique, and 2.5 times that of the second conventional technique. It increases to about 10 times. Here, the numerical values shown in Tables 1 and 2 are obtained by subjecting a metal silicon oxide film formed by MOCVD as a film to be etched to PDA treatment. In addition, it has been confirmed that the method of the present embodiment may have effects more than those shown in Tables 1 and 2 depending on the type of the metal silicon oxide film.

  The etching method of the present invention can also be applied to the formation of a capacitor dielectric film or a MEMS (Micro Electro Mechanical Systems) material.

  As described above, the method for manufacturing a semiconductor device according to the present invention is based on lanthanoids and actinides (La, Ce, Pr, Nd, Th), other Group 3 elements (Sc, Y), and Group 4 elements (Zr, Hf). This is useful for manufacturing various semiconductor devices including a metal oxide containing a Group 5 element (Ta) and a metal silicon oxide film as a gate insulating film, a capacitor insulating film, or the like.

(A) is a figure which shows the pH dependence of the etching rate of the metal oxide film (metal silicon oxide film) in a hydrofluoric acid solution, (b) is the etchant presence rate in the hydrofluoric acid aqueous solution. It is a figure which shows pH dependence. It shows the pH dependence of the selectivity to TEOS (Tetraethyl orthosilicate) film selection ratio and metal oxide film to a thermal oxide film of the metal oxide film in a hydrofluoric acid solution (th-SiO _2). In the etching method of this invention, it is a figure which shows the change of the etching rate and selectivity of a metal oxide film or a metal silicon oxide film by the frequency | count of an OH group termination | terminus formation process. It is a figure for demonstrating the etching method of this invention. (A) is sectional drawing which shows the etching method which concerns on the comparative example of embodiment of this invention, (b) is sectional drawing which shows the etching method which concerns on embodiment of this invention. (A), (b) is a figure which respectively shows the comparison of the etching amount in the etching method which concerns on embodiment of this invention, and the etching method which concerns on a comparative example, and the comparison of etching selectivity. (A) is a figure which shows the conventional etching method, (b) is a figure which shows the etching method using the chemical | medical solution of this invention. (A), (b) is a figure which respectively shows the measurement result of the etching amount in the etching method on the conditions shown to FIG. 7 (a), (b), and the selectivity of a metal silicon oxide film. (A), (b) is a figure which respectively shows the etching amount and selection ratio of a metal oxide film and a metal silicon oxide film on various conditions. It is a figure which shows the conventional general chemical | medical solution processing method. (A) is a figure which shows the manufacturing process of the semiconductor device described in the nonpatent literature 1, (b) is a figure which shows the SEM photograph of the gate electrode patterned in the conventional semiconductor device.

Explanation of symbols

1 chemical
3 Metal oxide film or metal silicon oxide film
5 Substrate 7 Cleaning liquid
8 Gas
13 Chemicals
15 Metal silicon oxide film
17 Substrate
19 Cleaning liquid
23 Selectivity

Claims (21)

An insulating film made of metal oxide or metal silicon oxide containing at least one element selected from La, Ce, Pr, Nd, Th, Sc, Y, Zr, Hf, and Ta is formed on the substrate. Using the first cleaning liquid after the step (a), the step (b) for rinsing the exposed surface of the insulating film, and the step (a). a step (c) of drying the insulating film after b);
A method of etching an insulating film, comprising performing a step of terminating an exposed surface of the insulating film with an OH group before or during the step (a). The step (a)
Etching the insulating film using the chemical solution (a1);
After the step (a1), a step (a2) of terminating the exposed surface of the insulating film with an OH group using a second cleaning liquid;
The method for etching an insulating film according to claim 1, further comprising a step (a 3) of etching the insulating film again after the step (a 2).   3. The insulating film etching method according to claim 2, wherein the chemical solution contains hydrofluoric acid or a salt thereof.   The insulating film etching method according to claim 3, wherein the chemical solution is a water-soluble chemical solution mixed with an acidic chemical that lowers the pH.   The insulating film etching method according to claim 4, wherein the chemical solution has a pH of −1.0 or more and 4.0 or less.   5. The insulating film etching method according to claim 4, wherein the chemical solution has a pH greater than 0 and 2 or less.   The method for etching an insulating film according to claim 2, wherein in the step (a), the step (a2) and the step (a3) are alternately repeated a plurality of times.   The insulating film etching according to claim 2, wherein the step (a2) includes a step of rinsing an exposed surface of the insulating film using the second cleaning liquid. Method.   9. The insulating film according to claim 8, wherein the step (a2) further includes a step of drying the insulating film after rinsing the exposed surface of the insulating film using the second cleaning liquid. Etching method. The insulating film etching according to claim 9, wherein when the insulating film is dried in the step (a2), at least one of N ₂ , Ar, and N ₂ O gas is used. Method. The method for etching an insulating film according to claim 10, wherein O ₂ or O ₃ is added when the insulating film is dried in the step (a2).   The insulating film etching method according to claim 8, wherein the second cleaning liquid contains an oxidizing agent. The second cleaning liquid is characterized in that, as the oxidizing agent, H ₂ O ₂ having a weight ratio of 0.01% or more and 50% or less, or O ₃ having a concentration of 10 mg / L or less is added. The method for etching an insulating film according to claim 12.   The method of etching an insulating film according to claim 2, wherein the chemical solution contains an oxidizing agent. The chemical solution is characterized in that, as the oxidizing agent, H ₂ O ₂ having a weight ratio of 0.01% or more and 50% or less, or O ₃ having a concentration of 10 mg / L or less is added. Item 15. The method for etching an insulating film according to Item 14.   16. The process according to claim 2, wherein the step (a) further includes a step of plasma oxidizing the exposed surface of the insulating film between the step (a2) and the step (a3). The insulating film etching method according to any one of the above. Before the step (a), the method further includes a step (d) of forming a mask on or above a part of the insulating film,
The insulation according to any one of claims 2 to 16, wherein in the step (a), the insulating film in a region that is not covered with the mask in a plan view is selectively etched. Method for etching the film. A silicon oxide film is further formed on the substrate,
In the step (a), when the etching rate of the silicon oxide film by the chemical solution is E _ox and the etching rate of the insulating film is E _Me , (E _Me / E _ox )> 1. The method for etching an insulating film according to claim 1. Etching the insulating film made of metal oxide or metal silicon oxide formed on the substrate with a chemical solution into a predetermined shape (a), and using the cleaning liquid after the step (a) And (b) rinsing the exposed surface of the insulating film, and (c) drying the insulating film after the step (b),
The said chemical | medical solution contains the hydrofluoric acid or its salt, The etching method of the insulating film which is a water-soluble chemical | medical solution with which the acidic chemical | medical agent which drops pH was mixed.   The method of etching an insulating film according to claim 19, wherein the chemical solution has a pH of -1.0 or more and 4.0 or less.   20. The method of etching an insulating film according to claim 19, wherein the chemical solution has a pH greater than 0 and 2 or less.