JP2019129313A - Etching method - Google Patents

Abstract

To provide an etching method capable of etching one of SiGe-based materials which differ in Ge concentration from each other at a higher selection ratio for the other.SOLUTION: A processed body having a first SiGe-based material and a second SiGe-based material differing in Ge concentration from each other is supplied with an etching gas, and a difference in incubation time up to a start of etching with the etching gas between the first SiGe-based material and second SiGe-based material is utilized to etch one of the first SiGe-based material and second SiGe-based material selectively for the other.SELECTED DRAWING: Figure 1

Description

  The present disclosure relates to an etching method for etching a SiGe-based material.

  In recent years, silicon germanium (referred to as SiGe) is known as a new semiconductor material other than silicon (hereinafter referred to as Si), and after laminating a Si layer and a SiGe layer as a semiconductor element using this SiGe, a SiGe layer is formed. What is etched selectively with respect to the Si layer, and what is etched selectively with respect to the SiGe layer is required for the Si layer.

As a technique for selectively etching SiGe relative to Si, one using ClF ₃ and XeF ₂ as etching gases (Patent Document 1), one using HF (Patent Document 2), NF ₃ gas and O ₂ gas The thing using the plasma of mixed gas, such as (patent document 3), is known. Further, as a technique for selectively etching Si with respect to SiGe, a technique is known in which etching is performed by adding a gas containing germanium to an etching gas containing SF ₆ or CF ₄ (Patent Document 4).

Further, Patent Document 5 describes that selective etching of SiGe to Si and selective etching of Si to SiGe are possible by changing the ratio of F ₂ gas and NH ₃ gas.

Japanese Patent Application Publication No. 2009-510750 JP 2003-77888 A Patent No. 6138653 JP, 2013-225604, A JP, 2016-143781, A

  By the way, although all of the above-mentioned techniques selectively etch SiGe relative to Si or selectively etch Si relative to SiGe, recently, although the Ge concentrations of the SiGe-based materials are different from each other. It is also being demanded to etch one with a high selectivity with respect to the other, and the above technique cannot sufficiently cope with such etching.

  Therefore, the present disclosure provides an etching method capable of etching one of SiGe-based materials having different Ge concentrations from each other with a high selectivity.

  In an etching method according to an aspect of the present disclosure, an etching gas is supplied to an object having a first SiGe-based material and a second SiGe-based material having different Ge concentrations, and the first SiGe-based material And a difference in incubation time until etching of the second SiGe-based material by the etching gas is started to use one of the first SiGe-based material and the second SiGe-based material to the other And selectively etch.

  In an etching method according to another aspect of the present disclosure, an etching gas is supplied to an object to be processed having a first SiGe-based material and a second SiGe-based material having different Ge concentrations, and the first SiGe The first SiGe-based material and the first SiGe-based material are repeatedly subjected to an etching process at an etching time in which one of the base material and the second SiGe-based material is etched and the other is not substantially etched, and purging of the processing space a plurality of times. One of the second SiGe based materials is selectively etched relative to the other.

  In an etching method according to still another aspect of the present disclosure, an etching gas is supplied at a low temperature range to an object to be processed having a first SiGe-based material and a second SiGe-based material having different Ge concentrations, One of the SiGe-based material of 1 and the second SiGe-based material is selectively etched with respect to the other.

  According to the present disclosure, it is possible to etch one of the first SiGe-based material and the second SiGe-based material with high selectivity without etching the other very little.

It is a figure for demonstrating schematically the etching method which concerns on the 1st example of 1st Embodiment. It is a figure which shows the relationship between the etching time at the time of 80 degreeC, 100 degreeC, and 120 degreeC of a Si-10% Ge film | membrane and a Si-30% Ge film | membrane. It is a figure which expands and shows a part of FIG. It is a figure for demonstrating schematically the etching method which concerns on the 1st example of 2nd Embodiment. When the Ge concentration was etched 0% Si film ClF ₃ gas is a diagram showing the temperature dependency of the etching amount. When the Ge concentration was etched 30 at% of the SiGe film (Si-30% Ge film) by ClF ₃ gas is a diagram showing the temperature dependency of the etching amount. Etching of the Si-30% Ge film to the Si-10% Ge film when the Si-10% Ge film and the Si-30% Ge film are etched at 120 ° C. which is the high temperature region at 35 ° C. which is the low temperature region It is a figure which shows a selection ratio. It is a schematic sectional drawing which shows the 1st example of the structure of the to-be-processed object to which 1st and 2nd embodiment is applied, and is a figure which shows the state before an etching. It is a schematic sectional drawing which shows the 1st example of the structure of the to-be-processed object to which 1st and 2nd embodiment is applied, and is a figure which shows the state after an etching. It is a schematic sectional drawing which shows the 2nd example of the structure of the to-be-processed object to which 1st and 2nd embodiment is applied, and is a figure which shows the state before an etching. It is a schematic sectional drawing which shows the 2nd example of the structure of the to-be-processed object to which 1st and 2nd embodiment is applied, and is a figure which shows the state after an etching. It is a schematic block diagram which shows an example of the processing system which mounts the etching apparatus used for implementation of 1st Embodiment and 2nd Embodiment. It is sectional drawing which shows an example of the etching apparatus for enforcing the etching method of the 1st example of 1st and 2nd embodiment. It is a figure which shows an example of the etching apparatus for enforcing the etching method of the 2nd example of 1st and 2nd embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the attached drawings.

First Embodiment
First, the first embodiment will be described.
In this embodiment, an etching gas, for example, a gas containing a fluorine-containing gas, is supplied to a target substrate having a first SiGe-based material and a second SiGe-based material having different Ge concentrations, and the first SiGe-based material The temperature at which the difference in the incubation time until the etching of the material and the second SiGe-based material with the etching gas starts is utilized to take advantage of the difference in the incubation time to determine the first SiGe-based material and the second SiGe-based material. One is selectively etched relative to the other. In the present embodiment, the SiGe-based material also includes the case where Ge is 0% (that is, the case of Si).

  In the first example of this embodiment, the first film made of SiGe having a relatively high Ge concentration as the first SiGe-based material and the relative Ge concentration as the second SiGe-based material An object to be treated having a low SiGe film or a second film consisting of a Si film of 0% Ge is prepared, and a fluorine-containing gas is supplied as an etching gas to the object to treat the first film as a second film. Etch selective to film. In addition to the fluorine-containing gas, an inert gas such as Ar gas may be supplied. At this time, it is preferable that the selection ratio of the first film to the second film is 5 or more, while the second film is hardly etched.

As the fluorine-containing gas, ClF ₃ gas, F ₂ gas, IF ₇ gas or the like can be used.

  At this time, when the above-mentioned fluorine-containing gas is used as the etching gas, the first film having a high Ge concentration is more easily etched than the second film having a low Ge concentration. Although it is possible to selectively etch one film relative to the second film, the second film is also etched particularly in the high temperature region, in the etching using only the difference in chemical reactivity by the etching gas. It is not preferable.

  On the other hand, in the present example, selective etching is performed using a difference in incubation time of etching reaction of the first film and the second film in a predetermined temperature range, particularly in a high temperature range as described later. The incubation time is the time from when the etching gas is supplied to when the etching reaction is actually started, and as shown in FIG. 1, the incubation time (T2) of the second film with low Ge concentration is This is longer than the incubation time (T1) of the high Ge concentration first film. By utilizing this difference in incubation time (ΔT), the first film is etched while etching of the second film is sufficiently suppressed, and highly selective etching is performed.

Such a difference in incubation time (ΔT) exists because a SiO ₂ film as a natural oxide film that is difficult to etch with a fluorine-containing gas is formed more on the surface of the second film than the first film. It is thought that.

  The incubation time can be adjusted by the temperature of the object (etching temperature) during etching, and etching is performed so that a sufficient incubation time difference (ΔT) is formed between the first film and the second film. It is preferable to set the temperature. At this time, the time required for etching the first film is more preferably equal to or less than the incubation time (T2) of the second film, that is, the incubation period. Thus, the first film can be etched at a high selectivity with respect to the second film without almost etching the second film.

  In this example, as described above, a Si0% Ge film is also acceptable as the low Ge concentration second film, but the effect is more exhibited when both the first and second films are SiGe films. Further, as a specific numerical value, the Ge concentration of the first film having a high Ge concentration is preferably in the range of 20 to 50 at%, more preferably 25 to 35 at%, for example, 30 at%. The second film preferably has a Ge concentration in the range of 0 to 20 at% (not including 20 at%), more preferably 5 to 15 at%, and for example 10 at%.

In this embodiment, the etching temperature is preferably a high temperature range of 100 ° C. or higher, and more preferably 100 to 125 ° C. Most preferred is 120 ° C. When the SiGe film is etched with a fluorine-containing gas such as ClF ₃ gas, the lower the temperature, the easier it is to etch, and the natural oxide film is also easier to etch. Although depending on the film quality of SiGe, near 80 ° C., the surface natural oxide film is easily etched even in a SiGe film having a low Ge concentration, and the incubation time is short and it is difficult to take the difference in incubation time. On the other hand, in the high temperature range of 100 ° C. or more, the etching rate of the natural oxide film on the surface of the SiGe film and the film itself is lowered, and the natural oxide film becomes difficult to etch in the low Ge concentration SiGe film, The incubation time of the low Ge concentration second membrane can be extended, and the incubation time difference can be increased. In particular, in the vicinity of 120 ° C., the SiGe film having Ge of 10 at% can sufficiently increase the incubation time to about 10 min, and the etching time is about 10 min without almost etching the second film having a low Ge concentration. For example, the first film with a high Ge concentration of 30 at% can be etched at a high selectivity. However, when the etching temperature is 130 ° C. or higher, the first film having a high Ge concentration is hardly etched.

  The pressure during the etching is preferably in the range of 10 to 1000 mTorr (1.33 to 133 Pa), for example, 120 mTorr (16 Pa).

Next, experimental results of the first example of the first embodiment will be described.
Here, the etching temperature is applied to a SiGe film (Si-10% Ge film) having a Ge concentration of 10 at% and a SiGe film (Si-30% Ge film) having a Ge concentration of 30 at% using a ClF ₃ gas as an etching gas. Were changed to 80 ° C., 100 ° C. and 120 ° C., and the relationship between the etching time and the etching amount was determined. The results are shown in FIG. FIG. 3 is a diagram showing a part of FIG. 2 in an enlarged manner.

  As shown in these figures, both the Si-10% Ge film and the Si-30% Ge film have a large amount of etching at 80 ° C., and the Si-30% Ge film is Si-10 at any temperature. It can be seen that the etching amount is larger than the% Ge film. Also, at 80 ° C., the incubation time is short for both the Si-10% Ge film and the Si-30% Ge film, and the etching for the Si-10% Ge film is started in a short time, and the Si-10 for 600 seconds (10 min) It can be seen that the etching amount of the% Ge film is 10 nm or more. On the other hand, when the etching temperature is 100 ° C., the incubation time of the Si-10% Ge film is 100 sec, and it is understood that the etching using the difference of the incubation time with the Si-30% Ge film is possible. Further, even if the etching time is 600 sec (10 min), the etching amount of the Si-10% Ge film is about 3 nm, and the etching of the Si-10% Ge film can be suppressed to etch the Si-30% Ge film. The In addition, when the etching temperature is 120 ° C, the incubation time of the Si-10% Ge film is 600 sec (10 min), and the selectivity of the Si-30% Ge film to the Si-10% Ge film is infinite for a long period of 600 sec. It was confirmed that the etching was possible. Further, when the etching temperature was 120 ° C., the etching amount of the Si-10% Ge film was as small as about 5 nm even when the etching time was 1200 seconds.

Next, a second example of the present embodiment will be described. The second example is a first film made of SiGe having a relatively high Ge concentration as the first SiGe-based material and a SiGe film having a relatively low Ge concentration as the second SiGe-based material. An object to be processed having a second film made of a Si film with 0% Ge is prepared, and a fluorine-containing gas and NH ₃ gas are supplied as an etching gas to the object to be processed. Etch selective to film. That is, contrary to the first example, the second film having a low Ge concentration is selectively etched with respect to the first film having a high Ge concentration. At this time, it is preferable that the selection ratio of the second film to the first film is 5 or more, with the second film being hardly etched.

By adding such the NH ₃ gas as an etching gas, the difference in Ge concentration is inverted by the NH ₃ gas to the fluorine-containing gas is added, more of SiO ₂ is a natural oxide film on the surface etched It is easy to be done. As the fluorine-containing gas, ClF ₃ gas, F ₂ gas, IF ₇ gas, or the like can be used as in the first example. The ratio of the fluorine-containing gas to the NH ₃ gas is preferably in the range of 1/500 to 1.

  Also in this example, the Ge concentrations of the first film and the second film are the same as in the first example, and only the etched side is different. The same applies to the etching temperature, preferably 100 ° C. or higher, more preferably 100 to 125 ° C., and most preferably 120 ° C.

Second Embodiment
Next, a second embodiment will be described.
In the present embodiment, an etching gas, for example, a gas containing a fluorine-containing gas is supplied to a substrate to be processed having a first SiGe-based material and a second SiGe-based material having different Ge concentrations. The first SiGe-based material and the second SiGe-based material are formed by repeating the etching process with an etching time in which one of the system-based material and the second SiGe-based material is etched and the other is not substantially etched, and purging the processing space multiple times. Selectively etch one of the SiGe based materials with respect to the other. In the present embodiment, the SiGe-based material includes a case where Ge is 0% (that is, Si).

  In the first example of this embodiment, the first film made of SiGe having a relatively high Ge concentration as the first SiGe-based material and the relative Ge concentration as the second SiGe-based material An object to be treated having a low SiGe film or a second film consisting of a Si film of 0% Ge is prepared, and a fluorine-containing gas is supplied as an etching gas to the object to be treated as shown in FIG. The etching process (S1) and the purging process (S2) of the processing space at an etching time in which the film of 1 is etched and the second film is not substantially etched are repeated predetermined times. The purge step (S2) of the processing space can be performed by evacuating the processing container that defines the processing space. An inert gas may be supplied as a purge gas to the processing space together with the evacuation. As described above, by repeating the etching step (S1) and the purge step (S2) a predetermined number of times, the first film is etched at a high selectivity with respect to the second film with almost no etching of the second film. can do. At this time, it is preferable that the selection ratio of the first film to the second film is 5 or more, while the second film is hardly etched.

  One etching step (S1) is preferably completed in a period in which the second film is etched within the incubation period. As a result, even if the etching step (S1) is repeated, only the first film can be repeatedly etched to obtain a desired etching amount, without substantially etching the natural oxide film on the surface of the second film. Therefore, in the present embodiment, even if the difference in incubation time between the first film and the second film is small, substantially only the first film can be etched by a desired amount, so that a temperature margin is provided as compared with the first example. Is wide.

As the fluorine-containing gas, ClF ₃ gas, F ₂ gas, IF ₇ gas, or the like can be used as in the first embodiment. In addition to the fluorine-containing gas, an inert gas such as Ar gas may be supplied.

  As described above, a Si0% Ge film is also acceptable as a low Ge concentration second film, but it is more effective when both the first and second films are SiGe films. Further, as a specific numerical value, the Ge concentration of the first film having a high Ge concentration is preferably in the range of 20 to 50 at%, more preferably 25 to 35 at%, for example, 30 at%. The Ge concentration of the second film is preferably in the range of 0 to 20 at% (not including 20 at%), more preferably 5 to 15 at%, for example 10 at%.

  As described above, the margin of the etching temperature is wider than that of the first embodiment, but also in this example, the etching temperature is preferably 100 ° C. or higher, and more preferably 100 to 125 ° C. Most preferred is 120 ° C.

  In this example, the time for one etching step (S1) is preferably 1 to 10 seconds, and the time for one purge step (S2) is preferably 5 to 30 seconds. The pressure during etching is preferably in the range of 10 to 1000 mTorr (1.33 to 133 Pa), for example, 120 mTorr (16 Pa).

Next, a second example of the present embodiment will be described. The second example is a first film made of SiGe having a relatively high Ge concentration as the first SiGe-based material and a SiGe film having a relatively low Ge concentration as the second SiGe-based material. A target object having a second film made of a Si film with 0% Ge is prepared, and a fluorine-containing gas and NH ₃ gas are supplied as an etching gas to the target object, and the second film is etched. An etching process with an etching time during which the first film is not substantially etched and a process space purging process are repeated a predetermined number of times. That is, contrary to the first example, the second film having a low Ge concentration is selectively etched with respect to the first film having a high Ge concentration. At this time, it is preferable that the selection ratio of the second film to the first film is 5 or more, with the second film being hardly etched.

Thus, by adding NH ₃ gas as the etching gas, the difference in Ge concentration is reversed on the same principle as the second example of the first embodiment.

Third Embodiment
Next, a third embodiment will be described.
In this embodiment, a gas containing an etching gas, for example, a fluorine-containing gas, is supplied in a low temperature range to a target substrate having a first SiGe-based material and a second SiGe-based material having different Ge concentrations. Selectively etch one of the SiGe-based material and the second SiGe-based material with respect to the other. Unlike the first embodiment in which the incubation time difference is used in this embodiment, the selectivity is secured by the difference between the etching amounts of the two. In the present embodiment, the SiGe-based material includes a case where Ge is 0% (ie, Si).

  In the first example of this embodiment, the first film made of SiGe having a relatively high Ge concentration as the first SiGe-based material and the relative Ge concentration as the second SiGe-based material An object to be treated having a low SiGe film or a second film consisting of a Si film of 0% Ge is prepared, and a fluorine-containing gas is supplied as an etching gas to the object to treat the first film as a second film. Etch selective to film. In addition to the fluorine-containing gas, an inert gas such as Ar gas may be supplied. At this time, it is preferable that the selection ratio of the first film to the second film is 5 or more, while the second film is hardly etched.

As the fluorine-containing gas, ClF ₃ gas, F ₂ gas, IF ₇ gas or the like can be used.

  At this time, when the above-mentioned fluorine-containing gas is used as the etching gas, the first film having a high Ge concentration is more easily etched than the second film having a low Ge concentration. One film can be etched selectively to the second film.

  The pressure during the etching is preferably in the range of 10 to 1000 mTorr (1.33 to 133 Pa), for example, 120 mTorr (16 Pa).

  In the present embodiment, the etching temperature is in a low temperature range, preferably 60 ° C. or less. More preferably, it is in the range of 0 to 60 ° C.

  The reason will be described below based on FIGS. 5 and 6 in which the relationship between the temperature and the etching amount is actually grasped.

FIG. 5 is a view showing the temperature dependency of the etching amount when etching a Si film having a Ge concentration of 0% with a fluorine-containing gas, ClF ₃ gas, and the etching time at each temperature of 20 to 120 ° C. The tendency of the etching amount at the time of etching set as 30 sec is shown. The etching conditions for the Si film were as follows: ClF ₃ gas flow rate: 20 to 500 sccm, Ar gas flow rate: 100 to 1000 sccm, and pressure: 500 to 3000 mTorr. As shown in this figure, the etching amount of the Si film does not have linearity with respect to temperature, and the etching amount is large in the middle temperature range around 80 ° C., and the etching amount tends to be small at 60 ° C. or less and 100 ° C. . In particular, at 60 ° C. or less, the etching amount of the Si film is smaller. Such a tendency is considered to be due to the strong influence of the characteristics of chemical adsorption in Si film etching with ClF ₃ gas. This tendency is considered to be the same as in the case of a SiGe film with a small amount of Ge (for example, Si-10% Ge film).

On the other hand, FIG. 6 is a diagram showing the temperature dependency of the etching amount when etching a SiGe film (Si-30% Ge film) having a Ge concentration of 30 at% with ClF ₃ gas, and each of 20 to 120 ° C. The etching amount at the time of making etching time 30 seconds by temperature is shown. The etching conditions for the Si-30% Ge film were ClF ₃ gas flow rate: 1 to 100 sccm, Ar gas flow rate: 100 to 1000 sccm, and pressure: 10 to 1000 mTorr. From this figure, it appears that the physical adsorption characteristics are strong in the etching of the Si-30% Ge film, the etching amount has linearity with respect to the temperature, and the etching amount tends to increase as the temperature decreases.

  From FIG. 5 and FIG. 6, the etching amount of the Si-30% Ge film increases and the etching amount of the Si film decreases. In the low temperature range of 60 ° C. or less, the Si-30% Ge film to the Si film The etching selectivity can be increased, and the value tends to increase as the temperature decreases. As shown in FIG. 7 described later, the etching selectivity of the Si-30% Ge film to the Si-10% Ge film exhibiting an etching tendency similar to that of the Si film exhibits a high value of 20 or more. In FIGS. 5 and 6, there is only data up to 20 ° C., but it is considered that a high selection ratio can be obtained at least up to 0 ° C. from the tendency of these figures. Thus, the Ge concentration of the first film made of SiGe having a high Ge concentration is relatively low, preferably in a low temperature range of preferably 60 ° C. or less, more preferably 0 to 60 ° C., and more preferably 20 to 60 ° C. The second film made of SiGe (including 0%) can be etched with a very high selectivity without using the incubation time difference.

  The higher the temperature, the lower the etching amount of the Si-30% Ge film, which adversely affects the etching selectivity of the Si-30% Ge film to the Si film, but at 100 ° C. or higher than around 80 ° C. The etching amount of the Si film is reduced. For this reason, even in the high temperature range of 100 ° C. or higher, the etching selectivity of the Si-30% Ge film to the Si film can be made relatively high without using the incubation time difference. However, as described in the first embodiment, in the high temperature region, the first film can be etched with higher selectivity to the second film by utilizing the difference in incubation time.

Next, experimental results of the first example of the third embodiment will be described.
First, using a ClF ₃ gas as an etching gas, a SiGe film having a Ge concentration of 10 at% (Si-10% Ge film) and a SiGe film having a Ge concentration of 30 at% (Si-30% Ge film) are in a low temperature region. And at a high temperature of 120.degree. FIG. 7 is a plot of etching at 35 ° C. and etching at 120 ° C. with the etching amount of the Si-30% Ge film taken on the horizontal axis and the etching amount of the Si-10% Ge film taken on the vertical axis. FIG. The etching conditions at this time were a ClF ₃ gas flow rate of 1 to 100 sccm, an Ar gas flow rate of 100 to 1000 sccm, and a pressure of 10 to 1000 mTorr. As shown in the figure, the etching selectivity of the Si-30% Ge film to the Si-10% Ge film was 24.6 at 35 ° C. and 11.2 at 120 ° C. From these results, it was confirmed that a high etching selectivity of 20 or more was obtained in the low temperature range, and an etching selectivity of 10 or more was obtained in the high temperature range, although not as low as in the low temperature range.

<Example of Structure of Object to be Applied to First and Second Embodiments>
Next, structural examples of the object to which the first and second embodiments are applied will be described. The object to be processed is typically a semiconductor wafer (hereinafter simply referred to as a wafer).

8A and 8B are diagrams showing a first example of the structure of the object to be processed.
In this example, as shown in FIG. 8A, a high Ge concentration SiGe film (for example, 30 at% of Ge concentration) 11 as a first film to be etched and a second film are formed on a semiconductor substrate 1 such as a Si substrate. As shown, a laminated structure with a low Ge concentration SiGe film (for example, Ge concentration 10 at%) 12 is formed. Specifically, a low Ge concentration SiGe film 12 and a high Ge concentration SiGe film 11 are sequentially laminated on the semiconductor substrate 1, and the uppermost layer is a low Ge concentration SiGe film 12, on which, for example, SiO _2. An etching mask 13 made of a film is formed. The number of stacked layers of the low Ge concentration SiGe film 12 and the high Ge concentration SiGe film 11 may be one or more.

In this state, the object to be processed is held at a predetermined temperature, and fluorine-containing gas such as ClF ₃ gas is supplied as in the first example of the first embodiment, or the first embodiment of the second embodiment. The high Ge concentration SiGe film 11 is etched by repeating the supply of the fluorine-containing gas and the purge as in the example of FIG. 8B, for example. At this time, the low concentration GeSiGe film 12 is hardly etched. Although a part of the high Ge concentration SiGe film 11 is etched in FIG. 8B, the whole may be etched. Alternatively, a Si film may be used instead of the low concentration GeSiGe film 12.

9A and 9B are diagrams showing a second example of the structure of the object to be processed.
In this example, as shown in FIG. 9A, a high Ge concentration SiGe film (eg, Ge) as a first film to be etched on a semiconductor substrate 21 such as a Si substrate via an insulating film (not shown). (A concentration 30 at%) 31 and a Si film 32 are formed, and portions corresponding to the source and drain of the semiconductor substrate 21 are formed on both sides of the stacked structure 30 via an insulating film 41 such as a Low-k film. And a low Ge concentration SiGe film (for example, Ge concentration of 10 at%) 42 that functions as a protective layer and serves as a second film, and a high Ge concentration SiGe film (for example, Ge concentration of 30 at%) 43 provided on the outside thereof. . In the laminated structure 30, an Si film 32 and a high Ge concentration SiGe film 31 are sequentially laminated on the semiconductor substrate 21, and the uppermost step is the Si film 32, and an etching mask 33 made of, for example, a SiO ₂ film is formed thereon. Is formed.

In this state, the object to be processed is held at a predetermined temperature, and fluorine-containing gas such as ClF ₃ gas is supplied as in the first example of the first embodiment, or the first embodiment of the second embodiment. The high Ge concentration SiGe film 31 is etched by repeating the supply and the purge of the fluorine-containing gas as in the example of FIG. 9B, for example. At this time, the low concentration GeSiGe film 42 is hardly etched, functions as a protective layer, and prevents the high Ge concentration SiGe film (for example, Ge concentration 30 at%) 43 from being etched.

  In the above two structural examples, in the case of the second example of the first embodiment and the second embodiment, a state in which the high Ge concentration SiGe film and the low Ge concentration SiGe film (or Si film) are inverted. It becomes.

<Processing system>
Next, an example of a processing system equipped with an etching apparatus used to carry out the first embodiment and the second embodiment will be described.
FIG. 10 is a schematic block diagram showing an example of the processing system. The processing system 100 includes a loading / unloading unit 102 for loading / unloading a wafer W as an object to be processed having the structure shown in the above structural example, and two load lock chambers 103 provided adjacent to the loading / unloading unit 102. A heat treatment apparatus 104 provided adjacent to each load lock chamber 103 for performing heat treatment on the wafer W, and an etching apparatus provided adjacent to each heat treatment apparatus 104 for etching the wafer W 105 and a control unit 106.

  The loading / unloading unit 102 has a transfer chamber 112 in which a first wafer transfer mechanism 111 for transferring the wafer W is provided. The first wafer transfer mechanism 111 has two transfer arms 111a and 111b for holding the wafer W substantially horizontally. On the side portion in the longitudinal direction of the transfer chamber 112, a mounting table 113 is provided, to which, for example, three carriers C for storing a plurality of wafers W such as FOUP can be connected. ing. Further, an alignment chamber 114 for aligning the wafer W is provided adjacent to the transfer chamber 112.

  In the loading / unloading unit 102, the wafer W is held by the transfer arms 111a and 111b, and moved straight up or down in a substantially horizontal plane by the drive of the first wafer transfer mechanism 111 to be transferred to a desired position. The transfer arms 111a and 111b move into and out of the carrier C on the mounting table 113, the alignment chamber 114, and the load lock chamber 103, respectively.

  Each load lock chamber 103 is connected to the transfer chamber 112 with a gate valve 116 interposed between the load lock chamber 103 and the transfer chamber 112. In each load lock chamber 103, a second wafer transfer mechanism 117 for transferring the wafer W is provided. Also, the load lock chamber 103 is configured to be able to evacuate to a predetermined degree of vacuum.

  The second wafer transfer mechanism 117 has an articulated arm structure, and has a pick for holding the wafer W substantially horizontally. In the second wafer transfer mechanism 117, the pick is positioned in the load lock chamber 103 in a state where the articulated arm is contracted, and by extending the articulated arm, the pick reaches the heat treatment apparatus 104 and is further extended. It is possible to reach the etching apparatus 105, and the wafer W can be transferred between the load lock chamber 103, the heat treatment apparatus 104, and the etching apparatus 105.

  The control unit 106 is typically a computer, and includes a main control unit having a CPU that controls each component of the processing system 100, an input device (keyboard, mouse, etc.), an output device (printer, etc.), a display A display etc.) and a storage device (storage medium). The main control unit of the control unit 106 causes the processing system 100 to execute a predetermined operation based on, for example, a storage medium incorporated in the storage device or a processing recipe stored in the storage medium set in the storage device. .

  In such a processing system 100, a plurality of wafers W on which the above-described structure is formed are stored in a carrier C and transported to the processing system 100. In the processing system 100, one wafer W is loaded by the carrier arm 111a or 111b of the first wafer transfer mechanism 111 from the carrier C of the loading / unloading unit 102 with the gate valve 116 on the atmosphere side open. To the pick of the second wafer transfer mechanism 117 in the load lock chamber 103.

  Thereafter, the gate valve 116 on the atmosphere side is closed to evacuate the load lock chamber 103, and then the gate valve 154 is opened, the pick is extended to the etching apparatus 105, and the wafer W is transferred to the etching apparatus 105.

  Thereafter, the pick is returned to the load lock chamber 103, the gate valve 154 is closed, and the etching process of the high Ge concentration SiGe film is performed by the etching method described above in the etching apparatus 105, for example.

  After the etching process is completed, the gate valves 122 and 154 are opened, and the wafer W after the etching process is transferred to the heat treatment apparatus 104 by the pick of the second wafer transfer mechanism 117 and the etching residue and the like are removed by heating.

  After the heat treatment in the heat treatment apparatus 104 is completed, the wafer is returned to the carrier C by one of the transfer arms 111a and 111b of the first wafer transfer mechanism 111. This completes the processing of one wafer.

  In the case where it is not necessary to remove the etching residue or the like, the heat treatment apparatus 104 may not be provided, and in that case, the wafer W after the etching process is load-locked by the pick of the second wafer transfer mechanism 117. It may be retracted to the chamber 103 and returned to the carrier C by one of the transfer arms 111a and 111b of the first wafer transfer mechanism 111.

<Etching device>
Next, an example of the etching apparatus 105 for performing the etching method of the first example of the first and second embodiments will be described in detail.
FIG. 11 is a cross-sectional view showing an example of the etching apparatus 105. As shown in FIG. As shown in FIG. 11, the etching apparatus 105 includes a chamber 140 having a sealed structure as a processing container that defines a processing space, and the wafer W is placed in a substantially horizontal state inside the chamber 140. A mounting table 142 is provided. The etching apparatus 105 further includes a gas supply mechanism 143 for supplying an etching gas to the chamber 140 and an exhaust mechanism 144 for exhausting the inside of the chamber 140.

  The chamber 140 is configured of a chamber main body 151 and a lid 152. The chamber main body 151 has a substantially cylindrical side wall portion 151 a and a bottom portion 151 b, and the upper portion is an opening, and the opening is closed by the lid portion 152. The side wall portion 151a and the lid portion 152 are sealed by a seal member (not shown), and airtightness in the chamber 140 is ensured.

  The lid portion 152 has a lid member 155 which constitutes the outside, and a shower head 156 which is fitted inside the lid member 155 and provided so as to face the mounting table 142. The shower head 156 has a main body 157 having a cylindrical side wall 157a and a top wall 157b, and a shower plate 158 provided at the bottom of the main body 157. A space 159 is formed between the main body 157 and the shower plate 158.

  A gas introduction passage 161 is formed through the lid member 155 and the upper wall 157b of the main body 157 up to the space 159, and a fluorine-containing gas supply piping 171 of a gas supply mechanism 143 described later is connected to the gas introduction passage 161. It is done.

  A plurality of gas discharge holes 162 are formed in the shower plate 158, and the gas introduced into the space 159 through the gas supply pipe 171 and the gas introduction path 161 is discharged from the gas discharge holes 162 into the space in the chamber 140. .

  The side wall 151 a is provided with a loading / unloading port 153 for loading / unloading the wafer W with the heat treatment apparatus 104, and the loading / unloading port 153 can be opened and closed by the gate valve 154.

  The mounting table 142 has a substantially circular shape in plan view, and is fixed to the bottom 151 b of the chamber 140. Inside the mounting table 142, a temperature controller 165 for adjusting the temperature of the mounting table 142 is provided. The temperature controller 165 includes, for example, a pipeline through which a temperature control medium (for example, water or the like) circulates, and heat exchange with the temperature control medium flowing in such a pipeline performs a mounting table 142. The temperature of the wafer W on the mounting table 142 is controlled.

The gas supply mechanism 143 includes a fluorine-containing gas supply source 175 that supplies a fluorine-containing gas such as ClF ₃ gas, and an inert gas supply source 176 that supplies an inert gas such as Ar gas. One end of the fluorine-containing gas supply pipe 171 and the inert gas supply pipe 172 are connected. The fluorine-containing gas supply pipe 171 and the inert gas supply pipe 172 are provided with a flow rate controller 179 that performs the opening and closing operation of the flow path and the flow rate control. The flow rate controller 179 is constituted by, for example, an on-off valve and a mass flow controller. The other end of the fluorine-containing gas supply pipe 171 is connected to the gas introduction path 161 as described above. The other end of the inert gas supply pipe 172 is connected to the fluorine-containing gas supply pipe 171.

  Therefore, the fluorine-containing gas is supplied from the fluorine-containing gas supply source 175 through the fluorine-containing gas supply pipe 171 into the shower head 156, and the inert gas is supplied from the inert gas supply source 176 to the inert gas supply pipe 172 and the fluorine. The gas is supplied to the shower head 156 through the contained gas supply pipe 171, and these gases are discharged from the gas discharge holes 162 of the shower head 156 toward the wafer W in the chamber 140.

  Among these gases, a fluorine-containing gas is a reactive gas, and an inert gas is used as a dilution gas and a purge gas. A desired etching performance can be obtained by supplying a fluorine-containing gas alone or by mixing a fluorine-containing gas and an inert gas.

  The exhaust mechanism 144 has an exhaust pipe 182 connected to the exhaust port 181 formed in the bottom 151 b of the chamber 140, and further, an automatic pressure provided in the exhaust pipe 182 for controlling the pressure in the chamber 140. A control valve (APC) 183 and a vacuum pump 184 for evacuating the chamber 140 are provided.

  Two capacitance manometers 186 a and 186 b are provided on the side wall of the chamber 140 as pressure gauges for measuring the pressure in the chamber 140 so as to be inserted into the chamber 140. The capacitance manometer 186a is for high pressure, and the capacitance manometer 186b is for low pressure. A temperature sensor (not shown) for detecting the temperature of the wafer W is provided in the vicinity of the wafer W mounted on the mounting table 142.

  In such an etching apparatus 105, the wafer W having the above-described structure is loaded into the chamber 140 and placed on the mounting table 142. The pressure in the chamber 140 is in the range of 10 to 1000 mTorr (1.33 to 133 Pa), for example 120 mTorr (16 Pa), and the temperature controller 165 of the mounting table 142 preferably sets the wafer W to 100 ° C. or more, more preferably And 100.degree.-125.degree. C., most preferably 120.degree.

Then, when etching is performed according to the first example of the first embodiment, a fluorine-containing gas, for example, ClF ₃ gas, is supplied into the chamber 140 at a flow rate of preferably 1 to 100 sccm to obtain high Ge concentration SiGe. Etch the film. As a result, the high Ge concentration SiGe film can be etched at a high selectivity with respect to the low Ge concentration SiGe film or the Si film, while hardly etching the low Ge concentration SiGe film or the Si film. At this time, an inert gas such as Ar gas may be supplied together with the fluorine-containing gas at a flow rate of 100 to 1000 sccm, for example. After the etching is completed, the inside of the chamber 140 is purged with an inert gas, and the wafer W is unloaded from the chamber 140.

When performing etching according to the first example of the second embodiment, a fluorine-containing gas, for example, ClF ₃ gas, is preferably supplied into the chamber 140 at a flow rate of 1 to 100 sccm to etch the high Ge concentration SiGe film. Etching the high Ge concentration SiGe film with a desired etching amount by repeating the etching step and the purge step of purging the processing space in the chamber 140 by evacuating or by using evacuating or a combination of evacuating and supplying inert gas. . As a result, the high Ge concentration SiGe film can be etched at a high selectivity with respect to the low Ge concentration SiGe film or the Si film, while hardly etching the low Ge concentration SiGe film or the Si film. At this time, in the etching step, together with the fluorine-containing gas, an inert gas such as Ar gas may be supplied at a flow rate of, for example, 100 to 1000 sccm. After the etching is completed, the inside of the chamber 140 is purged with an inert gas, and the wafer W is unloaded from the chamber 140.

When etching is performed according to the second example of the first and second embodiments, etching is performed by an etching apparatus 105 ′ shown in FIG. The etching apparatus 105 ′ has a gas supply mechanism 143 ′ having a fluorine-containing gas supply source 175, an inert gas supply source 176, and an NH ₃ gas supply source 177 instead of the gas supply mechanism 143 of the etching apparatus 105 of FIG. Use what you have. One end of an NH ₃ gas supply pipe 173 is connected to the NH ₃ gas supply source 177. The other end of the NH ₃ gas supply pipe 173 is connected to the fluorine-containing gas supply pipe 171. Similar to the fluorine-containing gas supply pipe 171 and the inert gas supply pipe 172, the NH ₃ gas supply pipe 173 is provided with a flow rate controller 179.

About the wafer W having a structure in which the high Ge concentration SiGe film and the low Ge concentration SiGe film (or Si film) are inverted from the two structural examples shown in FIGS. 5 and 6 by such etching apparatus 105 ′. The low Ge concentration SiGe film (or the Si film) can be etched at a high selectivity to the high Ge concentration SiGe film using a fluorine-containing gas and an NH ₃ gas.

<Other applications>
As mentioned above, although embodiment was described, it should be thought that embodiment disclosed this time is an illustration and restrictive at no points. The embodiments described above may be omitted, substituted, or changed in various forms without departing from the scope of the appended claims and the subject matter thereof.

  For example, the structural example of the object of the above embodiment is merely an example, and an object having a first SiGe-based material and a second SiGe-based material (including the case of 0% Ge) having mutually different Ge concentrations Any processing body is applicable. Further, the structure of the above processing system and individual apparatus is merely an example, and the etching method of the present invention can be carried out by systems and apparatuses having various configurations.

1, 21: semiconductor substrate 11; high Ge concentration SiGe film 12; low Ge concentration SiGe film 13; etching mask 30; laminated structure 31; high Ge concentration SiGe film 32; Si film 33; etching mask 41; k film)
42; Low Ge concentration SiGe film 43; High Ge concentration SiGe film 100; Processing system 105, 105 '; Etching apparatus 143, 143'; Processing gas supply mechanism 175; Fluorine-containing gas supply source W; Semiconductor wafer (object to be processed)

Claims (17)

  An etching gas is supplied to an object having a first SiGe-based material and a second SiGe-based material having different Ge concentrations, and the etching of the first SiGe-based material and the second SiGe-based material is performed. One of the first SiGe-based material and the second SiGe-based material is selectively etched with respect to the other by using a difference in incubation time until gas etching starts. Etching method.   An etching gas is supplied to an object having a first SiGe-based material and a second SiGe-based material having different Ge concentrations, and one of the first SiGe-based material and the second SiGe-based material is supplied. Etching is performed while the other is not substantially etched, and the processing space is repeatedly purged multiple times to set one of the first SiGe-based material and the second SiGe-based material to the other. Etching method characterized by selectively etching.   3. The etching method according to claim 2, wherein one time of the etching treatment is 1 to 10 seconds and one time of the purge is 5 to 30 seconds.   The etching method according to any one of claims 1 to 3, wherein a temperature during the etching is 100 ° C or higher.   The etching method according to claim 4, wherein a temperature at the time of the etching is 100 to 125 ° C. 5.   An etching gas is supplied at a low temperature range to an object having a first SiGe-based material and a second SiGe-based material having different Ge concentrations, and the first SiGe-based material and the second SiGe-based material Etching one of the layers selectively with respect to the other.   The etching method according to claim 6, wherein a temperature at the time of the etching is 60 ° C or less.   The etching method according to claim 7, wherein a temperature at the time of the etching is 0 to 60C.   The etching method according to any one of claims 1 to 8, wherein the etching gas is a gas containing a fluorine-containing gas. The etching method according to claim 9, wherein the fluorine-containing gas is at least one selected from the group consisting of ClF ₃ gas, F ₂ gas, and IF ₇ gas.   The first SiGe-based material is a first film composed of a SiGe film having a relatively high Ge concentration, and the second SiGe-based material is composed of a SiGe film or a Si film having a relatively low Ge concentration The second film according to claim 9 or 10, characterized in that the first film is selectively etched with respect to the second film using a fluorine-containing gas as an etching gas. Etching method. The first SiGe-based material is a first film made of a SiGe film having a relatively high Ge concentration, and the second SiGe-based material is made of a SiGe film or a Si film having a relatively low Ge concentration. 10. The second film according to claim 9, wherein the second film is selectively etched with respect to the first film using a fluorine-containing gas and an NH ₃ gas as an etching gas. Item 11. The etching method according to Item 10.   13. The etching method according to claim 11, wherein the object to be processed is configured by laminating the first film and the second film one or more times on a substrate.   The object to be processed is a structure portion having the first film to be etched on a substrate, and a non-etching object SiGe having a Ge concentration equivalent to that of the first film provided outside the structure portion. 12. The etching according to claim 11, wherein the second film provided as a protective layer for the non-etching target film is formed between the film, the structural portion and the non-etching target SiGe film. Method.   The etching method according to any one of claims 1 to 14, wherein a pressure at the time of etching is 1.33 to 133 Pa.   The first film has a Ge concentration of 20 to 50 at%, and the second film has a Ge concentration of 0 to 20 at%, according to any one of claims 11 to 15. Etching method. The etching method according to claim 16, wherein the first film has a Ge concentration of 25 to 35 at%, and the second film has a Ge concentration of 5 to 15 at%.

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