KR20100065875A - Dry etch method for silicon oxide - Google Patents

Abstract

Provided is a dry etching method of a silicon oxide film. Dry etching process according to the invention by using a mixed gas of HF gas and NH ₃ mixed gas or HF gas and the NH ₃ gas and isopropyl alcohol in the gas (IPA) as an etching gas, a silicon layer formed over the substrate according to the present invention It is possible to etch the oxide film with a very fast etching rate, and it is possible to etch the oxide film without the difference in the etching selectivity of each oxide film with respect to the composite oxide film including the thermal oxide film and other oxide films other than the thermal oxide film.

Description

Dry etch method for silicon oxide

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a semiconductor device, and more particularly, to a method of dry etching a silicon oxide film which is commonly formed for manufacturing a semiconductor device. The technical field of the present invention may be broadly defined as removing a silicon oxide film formed on a substrate by an etching gas.

In general, the manufacturing process of a semiconductor device is a process of realizing an electronic circuit that performs a certain function by combining thin films, such as conductive films, semiconductor films, and insulating films, having different properties on a substrate, by combining the order of stacking and the shape of a pattern. I can speak. Accordingly, in the semiconductor device manufacturing process, deposition and etching of various thin films are repeatedly performed.

Among various thin films, in particular, the silicon oxide film is widely used as an insulating film because it has excellent compatibility with silicon commonly used as a substrate, is easy to form by a method such as thermal oxidation, and is easy to handle. Conventionally, the silicon oxide film is etched by wet etching using HF diluent or BOE (buffered oxide etchant), but as the design rule of the semiconductor device decreases, a dry etching method for forming a finer pattern has been proposed. .

Conventional silicon oxide dry etching method often uses only HF gas, which is slower in etching than wet etching, which requires longer processing time, reduces throughput, and increases the etching selectivity of other oxides over thermal oxide. There is a problem that it is only applicable to a single type of oxide film, and needs improvement.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and a problem to be solved by the present invention is that the silicon oxide film can be efficiently etched at a substantially high etching rate and is applicable to a composite oxide film including a plurality of oxide films. It is to provide a dry etching method.

In order to solve the above problems, in the dry etching method according to the present invention, a silicon oxide film chamber is formed by using HF gas and NH ₃ gas or a mixed gas of HF gas and NH ₃ gas and isopropyl alcohol (IPA) as an etching gas. It is characterized by etching within. The substrate temperature during dry etching is determined in the range of 60 ° C to 85 ° C. Further, after the dry etching, a post heat step of removing the etching by-products from the substrate by raising the substrate temperature is further performed in-situ. At temperatures below 60 ° C., the throughput of the etch apparatus is reduced and at temperatures above 85 ° C. it is difficult to apply to composite oxide films containing oxide films other than thermal oxides and thermal oxides in etching selectivity.

In this case, at least one inert gas selected from N ₂ , Ar, and He may be further included and used. In dry etching, the lower the pressure inside the chamber, the longer the process time and the corrosion problem. Therefore, the pressure in the chamber during dry etching may be in the range of 10 mTorr to 100 Torr in consideration of this point.

The flow rate ratio of the HF gas: NH ₃ gas: IPA and the inert gas may be set to x: y: z, and may be a combination of x = 1 to 5, y = 1 to 5, and z = 1 to 5. The post-heat treatment is preferably performed in the range of 100 ° C to 150 ° C. If it is less than 100 ° C, the removal of the etch by-products is not easy, and if it is more than 150 ° C, there may be a problem of thermal damage.

In a preferred embodiment, the silicon oxide film is a composite oxide film including an oxide film other than the thermal oxide film and the thermal oxide film, the silicon oxide film is etched so that the etching selectivity of the oxide film other than the thermal oxide film with respect to the thermal oxide film is 1 or less. While producing etch byproducts on the substrate.

According to the present invention, by using a mixed gas of HF gas and NH ₃ gas (and IPA) as an etching gas, the silicon oxide film formed on the substrate can be etched with a very fast etching rate.

This reduces process time, reduces component damage in the chamber, maximizes etch efficiency, reduces etching costs, and improves throughput of the etch apparatus. Furthermore, the high throughput enables the replacement of conventional wet etching.

In addition, by dry etching, it is easier to set the process conditions such as the etching rate by adjusting the gas type, flow rate, and etching time, and the etching rate can be controlled by adjusting the flow rate, process time, and mixing ratio. It is possible to etch by a precisely controlled amount.

In addition, since the etching selectivity of the other oxide film with respect to the thermal oxide film can be made to be 1 or less, it is possible to apply to a composite oxide film including a plurality of oxide films.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, embodiments of the present invention may be modified in many different forms, and the scope of the present invention should not be construed as being limited to the embodiments described below. The embodiments of the present invention are provided to more completely explain the present invention to those skilled in the art. Accordingly, the shape of the elements in the drawings and the like are exaggerated to emphasize a clearer description.

(Example)

1 is a configuration diagram showing an example of an etching apparatus for performing a silicon oxide dry etching method according to the present invention.

This etching apparatus 100 has a chamber 10 in which a substrate w is loaded. The susceptor 20 on which the substrate w is disposed may be installed at a lower side of the inner space of the chamber 10 so as to be liftable. It is provided with a predetermined heater (not shown) to adjust the temperature inside the substrate w and / or the chamber 10. A showerhead 30 may be provided at an upper side of the inner space of the chamber 10 to inject an etching gas to etch the silicon oxide film formed on the substrate w.

On the other hand, the chamber 10 is further provided with a gas supply system 40 for introducing a flow-controlled etching gas into the chamber 10. In the present invention, the HF gas is not used alone, but a mixed gas including at least NH ₃ gas is used as the etching gas, and each component gas constituting the etching gas is not mixed beforehand in the chamber 10. The gas supply system 40 is independently provided for each component gas constituting the etching gas so as to be supplied and mixed. That is, although not shown in detail, the gas supply system 40 includes a gas supply path 40b connected to a supply source of each component gas (such as a gas cylinder or a canister containing a liquid), and a flow controller 40c and an MFC provided therein. ), And the like.

The showerhead 30 is a means for injecting the component gas supplied from the gas supply system 40 into the chamber 10, and is mixed in the showerhead 30 and premixed into the chamber 10. The type may be good for maintenance of the showerhead 30. To this end, there is at least one jet plate in the shower head 30 and a dual type may be employed for uniformity. Of course, the means for injecting the component gas into the chamber 10 may be in a form other than a showerhead such as a gas nozzle or a gas jet plate, and each gas may be introduced from below or side rather than above the chamber 10. It may be a configuration method.

1 is a single etching apparatus that processes one sheet at a time, but the present invention is not limited thereto, and a batch etching method capable of etching a plurality of substrates at once is possible. It can also be applied using a device. The substrate w is not limited to a semiconductor substrate such as a silicon wafer, but can also be applied to an LCD substrate, a glass substrate, and the like. In addition, the method of the present invention may be applied to an etch back for removing a silicon oxide film on the entire surface without a mask in addition to patterning that forms a mask with a photoresist or the like on a silicon oxide film and then etches only a portion thereof. Furthermore, the method of the present invention can be applied without regard to the type of silicon oxide film such as natural oxide film, thermal oxide film, deposited oxide film, chemical oxide film, coated oxide film, and the like. When applied to the composite oxide film of the type can be excellent effect.

Next, the method of the present invention that can be performed using the etching apparatus configured as described above will be described.

2 is a flowchart of a silicon oxide dry etching method according to the present invention.

The substrate w on which the silicon oxide film is formed is loaded into the chamber 10 of the etching apparatus 100 (step s11), and the silicon oxide film is dry-etched using a mixed gas of HF gas and NH ₃ gas as an etching gas. (Step s12). The etching gas may further include an IPA gas.

Specifically, the pressure inside the chamber 10 is adjusted to 10 mTorr to 100 Torr and the susceptor 20 temperature is set to 60 ° C. to 85 ° C., and then the substrate w is loaded. The susceptor 20 temperature is selected in the temperature range most suitable for the etching reaction of the etching gas. The susceptor 20 temperature becomes the substrate w temperature. In this case, the substrate w may be deposited on the high temperature susceptor 20 through a predetermined preheating step. However, in the reverse order, the substrate w may be first placed on the susceptor 20, and then the temperature of the substrate w may be adjusted by adjusting the temperature of the susceptor 20. At this time, the chamber 10 wall may be maintained at 80 ℃ to 100 ℃ for the purpose of preventing corrosion by the etching gas.

Then, the flow-controlled HF gas from the HF gas supply system is introduced into the chamber 10, while the flow-controlled NH ₃ gas from the NH ₃ gas supply system is introduced into the chamber 10. In addition, when the IPA gas is additionally used for the etching gas, the flow-controlled IPA is introduced into the chamber 10 from the IPA supply system. At room temperature, IPA is liquid, so it is introduced by evaporation through a suitable bubbling or vaporizer. The temperature of the gas supply path 40b is adjusted to 100 to 150 degreeC so that it may not liquefy on the gas supply path 40b according to the characteristic of the source which is liquid at room temperature.

As such, the HF gas and NH ₃ gas (and IPA) introduced into the chamber 10 are mixed while being injected into the chamber 10 through the shower head 30 to form the mixed gas on the substrate w. The silicon oxide film is etched and removed. The temperature of the showerhead 30 may be maintained at 90 ° C. to 150 ° C. to prevent the etching gas from condensing.

In this case, the etching gas may further include at least one inert gas selected from N ₂ , Ar, and He. The inert gas does not directly act as an effective part of the etching, but serves as a carrier gas so that each component gas constituting the etching gas can be delivered to the substrate w. At this time, the inert gas may be supplied alone through a different path from the component gas of the etching gas, or may be supplied by mixing with HF gas or NH ₃ gas or IPA gas. The flow rates of the HF gas, the NH ₃ gas, the IPA, and the inert gas may be selected from 10 to 300 sccm, respectively, and, for example, 60 sccm may be supplied to set the flow rate ratio of the HF gas: NH ₃ gas: IPA and the inert gas to 1: 1. Can be set to 1. However, an appropriate flow rate ratio can be set from 1 to 5: 1 to 5: 1 to 5. By adjusting the flow rate ratio of each gas, it is possible to change the etching rate, the selection ratio and the like, all of which will belong to the scope of the present invention.

The temperature of the substrate w during dry etching is set to 60 ° C. to 85 ° C., when the silicon oxide film formed on the substrate w is a composite oxide film containing an oxide film other than the thermal oxide film and the thermal oxide film. This is to produce (NH ₄ ) ₂ SiF ₆ on the substrate w, which is an etching by-product when using a mixed gas of HF gas and NH ₃ gas (and IPA) while having almost no difference. If the etching by-products are diffused into the chamber 10 during the etching process, the composition affects the atmosphere in the chamber 10, such as the composition of the etching gas to be supplied. In particular, in the present invention, the etching by-products are accumulated on the substrate w for a predetermined time. The temperature range is configured because the thermal oxide film and the oxide film other than the thermal oxide film are etched almost identically by using the effect of suppressing the etching reaction. If the substrate (w) temperature during dry etching is less than 60 ° C, the etching time is long, and the throughput of the etching apparatus is reduced, and at a temperature above 85 ° C, the composite including an oxide film other than the thermal oxide film and the thermal oxide film in the etching selectivity It is difficult to apply to oxide film. In addition, at a temperature of less than 60 ℃ occurs that becomes a white powder affects the etching characteristics and particles.

Although HF gas alone is not efficient in removing the silicon oxide film, the silicon oxide film can be efficiently removed by mixing NH ₃ gas therein according to the present invention, and the reaction time can be shortened more when IPA gas is further mixed. This can improve throughput. When HF gas, NH ₃ gas and silicon oxide film react, water is formed. In case of using IPA additionally, this water evaporates quickly, which improves the overall reaction rate, resulting in an increase in the etching rate, and further etching uniformity. To improve. As a result of the experiment, the etching speed is 300 kW per minute. However, as shown in the experimental example described below, the use of IPA is not necessarily necessary when the substrate (w) temperature during dry etching is 60 ° C or higher.

In this manner, after the silicon oxide film is etched, the temperature of the substrate w is raised to a temperature between 100 ° C. and 150 ° C. while maintaining the substrate w in the chamber 10. The post-heat treatment step of removing the etch byproducts is further performed in-situ (step s13).

In this case, since the etching process and the necessary post process are performed in one chamber, the throughput is improved, and the chamber 10 is exited in the state where the by-products are removed. Therefore, in the process of moving to another post-treatment chamber without removing the by-products, there is an effect of preventing contamination that may occur in other parts such as a transfer module.

The post-heat treatment is preferably performed in the range of 100 ° C. to 150 ° C., since the removal of the etch by-products is not easy when the temperature is less than 100 ° C., and when the temperature exceeds 150 ° C., there may be a problem of thermal damage.

Experimental Example 1

By applying the present invention, the etching rate according to the type of silicon oxide film was tested.

First, a substrate on which a thermal oxide film was formed and a PETEOS oxide film (Plasma Enhanced Tetra Ethyl Ortho Silicate) were prepared. The thickness of the thermal oxide film was 1000 mW and the uniformity was 1%. The thickness of the PETEOS oxide film was 2000 mW and the uniformity was 2%.

The pressure inside the chamber 10 was divided into 1 Torr and the temperature of the susceptor 20 at 60 ° C. and at 85 ° C., and the temperature at the wall of the chamber 10 was 90 ° C., the gas supply passage 40c and the like. The temperature of the showerhead 30 used 100 degreeC conditions. And, the spacing between the showerhead 30 and the substrate was maintained at 50mm. Etching gas are HF gas and NH ₃ gas were used only the flow rate of HF gas and NH ₃ gas was supplied to all 20 sccm, respectively (that is, HF gas: NH ₃ gas flow rate ratio of 1: 1). The post heat treatment step was performed for 60 seconds at a substrate temperature of 130 ° C., and the etched amount was measured for 25 points by removing the substrate subjected to post heat treatment.

Meanwhile, for comparison with the present invention, the remaining conditions were the same, and the case where the susceptor 20 temperature was increased to 90 ° C. during dry etching (comparative example) was also tested.

Figure 3 is a graph of the results of the etching rate by applying the present invention (60 ℃ process using a mixed gas of HF gas and NH ₃ gas).

In the graph, the x-axis shows the etching time and the y-axis shows the amount etched. According to the present invention, after the etching for 30 seconds, the thermal oxide layer (-◆-) was etched in 81Å and the PETEOS oxide layer (-■-) was etched in 77Å. As a result of calculating the etching rate from the etching amount after 60 seconds, the etching rate of 152.3 kPa / min for the thermal oxide film (-◆-) and 134.4 kPa / min for the PETEOS oxide film (-■-) was obtained.

4 is a graph showing the results of the etching rate when a comparative example (90 ° C. process using a mixed gas of HF gas, NH ₃ gas and IPA) is applied.

In the graph, the x-axis shows the etching time, the y-axis shows the amount of etching, and in the case of thermal oxide (-◆-), an etching rate of 35.1Å / min can be obtained, and in the case of PETEOS oxide (-■-), an etching rate of 88.7Å / min can be obtained. there was.

Therefore, in the case of the present invention to which the 60 ° C. process is applied, it can be seen that the etching rate is significantly improved, and it can be seen that the difference in etching selectivity according to the type of oxide film is not large. In particular, the selectivity of the PETEOS oxide film to the thermal oxide film is 1 or less. It can be seen that

In addition, when the 85 ° C. process is applied according to the present invention, as shown in FIG. 5, both the thermal oxide film and the PETEOS oxide film may be etched at the same speed or at a speed close thereto. In the graph of FIG. 5, the x-axis indicates the type of silicon oxide layer and the y-axis indicates the etching rate. The etching rate of the thermal oxide layer was 71.1 kV / min, and the PETEOS oxide layer of 70.9 kV / min. As such, since the thermal oxide film and the PETEOS oxide film can be etched at the same speed or near the same rate through the temperature control, when the composite oxide film including the thermal oxide film and the PETEOS oxide film is etched, there is no difference in selectivity for each oxide film. Etching can be performed.

In general, PETEOS oxides are softer oxides than thermal oxides. Due to these differences, PETEOS oxides are usually less etched than PETEOS oxides even when the same etching conditions are applied. However, in the semiconductor process, as shown in FIG. 6, there may be cases where a sandwich structure of a PETEOS oxide film, a thermal oxide film, and a PETEOS oxide film is used. When the photoresist is patterned on the composite oxide film and then the contact hole is etched through it, if the difference in etching selectivity between the thermal oxide film and the PETEOS oxide film is large, as shown in FIG. As it is etched, it is unclear whether the PETEOS oxide underneath is opened, which may cause a so-called open problem. However, if the etching selectivity difference between the thermal oxide film and the PETEOS oxide film is reduced as in the present invention, as shown in FIG. 6 (b), there is no such problem and the contact hole can be drilled. Therefore, the present invention can exert an excellent etching effect on the composite oxide film containing different types of oxide film.

Experimental Example 2

The etching characteristics of the process temperature were compared.

7 is a graph showing a trend of etching time according to etching time according to the type of oxide film by selecting a comparative example in which the conditions different from those of the present invention are the same and the process temperature is 30 ° C., and FIG. Shows a trend of etching amount according to etching time according to the type of oxide film.

As shown in FIG. 7, a process time of 60 seconds or more is required for the selectivity of the SOD (-■-) oxide, which is another oxide film based on the thermal oxide film (− ◆ −), to be 1 or less in the 30 ° C. process. . In addition, since the characteristics of the selectivity change as the process time changes, in order to obtain a stable selectivity, the supply of HF and NH ₃ must be increased, thereby causing a problem that the device throughput falls.

On the contrary, referring to FIG. 8, a process time of about 20 seconds is required for the selection ratio of another oxide film PETEOS oxide film (− ■ −) to 1 or less based on a thermal oxide film (− ◆ −). In addition, even if the process time is increased, the selection ratio does not change, and thus it can be used stably. In addition, as the processing time is shortened, the device throughput is improved.

9 is a susceptor photograph after etching and post-heat treatment are performed in the same chamber according to a comparative example in which the conditions different from the present invention are the same and the process temperature is 30 ° C. As the etch by-products that existed on the substrate as the progress of etching and then heat-treated in the same chamber decomposition HF, NH _3, H ₂ O, such as a lower susceptor section that is generated by the temperature to _{30 ℃ NH 4 F, NH 4} F The phenomenon that (HF) compound is adsorbed and becomes white powder occurs. This compound will affect the etching properties and particles. Accordingly, in order to prevent the compound from occurring, the apparatus becomes structurally complicated by increasing the temperature of the susceptor in the post-heating process, or accompanied by the constraints such as the isolation of the etching and the post-heating process, and the processing time is long, resulting in increased productivity. Fall, and device prices rise.

10 is a susceptor photograph after the etching and post-heat treatment in the same chamber in accordance with the present invention proceeding to 60 ℃ process. It can be seen that the white powder does not occur in the susceptor, which indicates that the susceptor has a relatively high temperature, so that there is no adsorption of the compound due to the decomposition of by-products, thereby performing a stable etching process. In addition, since there is no compound adsorption, there is no restriction on the post-heat treatment method.

On the other hand, since HF (hydrofluoric anhydride) corrodes most metals, and the lower the temperature, the higher the possibility of corrosion, the 30 ° C process may cause a reduction in mechanical properties of metals due to corrosion and metal contamination. However, the 60 ° C process is safe from corrosion because of the relatively high temperature of the susceptor.

11 is a case where the silicon oxide film is etched according to a comparative example in which the conditions different from those of the present invention are the same and the process temperature is 30 ° C., wherein a mixed gas of HF and NH ₃ gas is used as an etching gas, and N ₂ is used here. when using the HF and NH ₃ gas, and mixed gas of the IPA it was used as the carrier gas as an etching gas, and a comparison of etch rates in the case of using N ₂ as a carrier gas here.

When IPA was not added, the thermal oxidation etch rate was 93Å / min, and when IPA was added, etch rate was 123Å / min. IPA was added to increase the etching rate and improve the uniformity. The repeatability may not be good.

Inde 12 is a case of etching the silicon oxide film according to the present invention to proceed with the 60 ℃ process, a mixed gas of HF and NH ₃ gas as an etching gas and the amount of the IPA gas, using the N ₂ herein as a carrier gas It is the result of measuring the etching speed by increasing.

Since the process progress temperature of the substrate is relatively high, the effect of increasing the etching rate and the uniformity according to the IPA addition is not as compared with that of the 30 ° C comparative example, and since the IPA is not necessarily used, the reproducibility is good and the unit cost can be lowered.

On the other hand, when the process temperature is 60 ° C as in the present invention, it takes a relatively short time to increase the substrate temperature for the post-heat treatment compared to the case of 30 ° C has the effect of further increasing the device throughput. .

Experimental Example 3

FIG. 13 is a graph illustrating a change in etching rate according to etching temperatures of a thermal oxide film and a PETEOS oxide film.

According to the present invention, in the case of dry etching, the substrate temperature may be etched at 60 ° C. to 85 ° C. with little difference in etching selectivity between the two oxide films. The difference in selectivity is large, indicating that the reaction mechanism changes at process temperatures above 85 ° C.

In the above, the present invention has been described in detail with reference to some preferred embodiments, but the present invention is not limited to the above embodiments, and various modifications may be made by those skilled in the art within the technical spirit of the present invention. It is obvious. Accordingly, all such modifications are intended to be included within the scope of this invention.

1 is a view of an etching apparatus capable of performing a dry etching method according to the present invention.

2 is a flowchart of a silicon oxide dry etching method according to the present invention.

3 and 5 is a graph showing the results of the etching rate by applying the present invention.

4 is a graph showing the results of the etching rates when the comparative example is applied.

FIG. 6 is a diagram illustrating a result of an etching selectivity difference during contact hole formation of a composite oxide layer used in a semiconductor process.

FIG. 7 is a graph showing a trend of etching time by etching time according to the type of oxide film by selecting a comparative example, and FIG. 8 is a graph illustrating a trend of etching time by etching time according to the type of oxide film in the present invention.

9 is a photo susceptor after the etching and post-heat treatment in the same chamber according to the comparative example, Figure 10 is a photo susceptor after the etching and post-heat treatment in the same chamber according to the present invention.

11 is inde case of etching the silicon oxide film according to inde would present the effect of addition of IPA, 12 is the present invention when etching the silicon oxide film according to a comparative example, a mixed gas of HF and NH ₃ gas as an etch gas In addition, the etching rate is measured while increasing the amount of IPA gas added while using N ₂ as a carrier gas.

FIG. 13 is a graph illustrating etching rate change trends of the thermal oxide film and the PETEOS oxide film according to the etching temperature.

Claims (7)

In the method of dry etching the silicon oxide film formed on the substrate in the chamber, A mixed gas of HF gas and NH ₃ gas is used as an etching gas, The substrate temperature during dry etching is 60 ℃ to 85 ℃, And a post-heat treatment step of removing the etch by-products from the substrate by increasing the substrate temperature after dry etching, by in-situ. The method of claim 1, wherein isopropyl alcohol (IPA) gas is further included in the etching gas to be used. 3. The method of claim 1, wherein the etching gas further comprises at least one inert gas selected from N ₂ , Ar, and He. 4. The method of claim 3, wherein the internal pressure of the chamber during dry etching is 10 mTorr to 150 Torr. The method of claim 3, wherein the flow rate ratio of the HF gas: NH ₃ gas: IPA and the inert gas is set to 1 to 5: 1 to 5: 1 to 5. The method of claim 1, wherein the post-heat treatment is performed in the range of 100 ℃ to 150 ℃ silicon oxide film dry etching method. The method of claim 5, wherein the silicon oxide film is a composite oxide film including an oxide film other than the thermal oxide film and thermal oxide film, And etching by-products are formed on the substrate while the silicon oxide film is etched so that an etching selectivity of oxides other than the thermal oxide film with respect to the thermal oxide film is 1 or less.

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