JP7278456B2 - Plasma processing equipment - Google Patents

Description

The following disclosure relates to plasma processing apparatus.

As the miniaturization of semiconductor devices progresses, research and development of techniques that enable fine dimensional processing are progressing. One of them is extreme ultraviolet lithography (EUVL).

For example, a technology has been proposed that uses EUVL to smooth edges to be processed (Patent Document 1). In this technique, after forming a passivation layer that preferentially deposits in the recesses to be processed, the protrusions on which the passivation layer has not deposited are removed by etching. The reason why the passivation layer preferentially deposits on the recesses rather than on the protrusions is that the recesses have a larger specific surface area than the protrusions. This technology is also said to be effective in reducing local critical dimension uniformity (LCDU).

U.S. Patent Application Publication No. 2016/0379824

This disclosure provides techniques that can improve the LCDU.

A plasma processing method according to one aspect of the present disclosure includes a first step, a second step, and an etching step. In the first step, a first film is formed on a processing object in which a plurality of openings having a predetermined pattern are formed. The second step is to form a second film having a different film thickness on the side surface of the opening according to the size of the opening and an etching rate lower than that of the first film on the object to be processed on which the first film is formed. do. In the etching step, etching is performed under predetermined processing conditions from above the second film until a portion of the first film is removed from at least a portion of the object to be processed.

According to the present disclosure, an LCDU can be improved.

FIG. 1 is a flow chart showing an example of the flow of plasma processing according to the first embodiment. FIG. 2A is a schematic cross-sectional view of an example of an object to be processed by plasma processing according to the first embodiment. FIG. 2B is a schematic top view of the processing object shown in FIG. 2A. FIG. 2C is a schematic cross-sectional view showing a state in which a first film and a second film are formed on the processing target shown in FIG. 2A. FIG. 2D is a diagram (1) for explaining the etching removal rate of the first film and the second film deposited on the side wall of the opening. FIG. 2E is a diagram (2) for explaining the etching removal rate of the first film and the second film deposited on the side wall of the opening. FIG. 3 is a diagram for explaining the LCDU improvement effect obtained by the plasma processing method according to the first embodiment. FIG. 4 is a diagram for explaining the relationship between film formation conditions and etching resistance. FIG. 5 is a diagram showing an example of a processing sequence of plasma processing according to the first embodiment. FIG. 6 is a diagram showing another example of the processing sequence of plasma processing according to the first embodiment. FIG. 7 is a diagram showing still another example of the processing sequence of plasma processing according to the first embodiment. FIG. 8 is a flow chart showing an example of the flow of plasma processing according to Modification 1. As shown in FIG. FIG. 9 is a diagram showing an example of a processing sequence of plasma processing according to Modification 1. As shown in FIG. FIG. 10 is a diagram showing another example of the processing sequence of plasma processing according to Modification 1. In FIG. FIG. 11 is a diagram showing still another example of the processing sequence of the plasma processing according to Modification 1. As shown in FIG. FIG. 12 is a flow chart showing an example of the flow of plasma processing according to Modification 2. As shown in FIG. FIG. 13 is a flowchart showing an example of the flow of plasma processing according to Modification 3. As shown in FIG. FIG. 14 is a diagram showing an example of a processing sequence of plasma processing according to Modification 3. As shown in FIG. FIG. 15 is a diagram showing an example of a longitudinal section of a plasma processing apparatus according to one embodiment.

The disclosed embodiments will be described in detail below with reference to the drawings. In addition, this embodiment is not limited. Further, each embodiment can be appropriately combined within a range that does not contradict the processing contents.

<First embodiment>
Dimensional variations in semiconductor microfabrication affect the final product performance. Consider, for example, the case of forming a gate electrode on a semiconductor substrate. First, a polysilicon layer for a gate electrode and a mask layer for etching are sequentially formed on a semiconductor substrate. A pattern corresponding to the gate electrode is formed on the mask layer by lithography such as EUVL. Then, using the mask layer, the polysilicon layer is etched to form a gate electrode. At this time, variations in the dimensions of the pattern of the mask layer result in variations in the dimensions of the gate electrode. Therefore, it is preferable to improve the uniformity of pattern dimensions at the stage of the mask layer. A first embodiment provides a technique for uniformizing the dimensions of a pattern formed on a processing object and improving the LCDU. In the plasma processing method according to the first embodiment, for example, when patterns with approximately the same size are repeatedly formed on a processing object, the sizes of the patterns are made uniform. The plasma processing method according to the first embodiment is also effective in improving the roughness of patterns such as semiconductor wafers.

<Example of Flow of Plasma Processing According to First Embodiment>
FIG. 1 is a flow chart showing an example of the flow of plasma processing according to the first embodiment. The plasma processing according to the first embodiment is performed, for example, by a plasma processing apparatus (see FIG. 15), which will be described later.

First, a processing target (for example, a wafer) having a plurality of openings having a predetermined pattern is placed in a space where plasma processing is performed. Then, the plasma processing apparatus executes the first step (step S11). A plasma processing apparatus forms a first film on a predetermined pattern to be processed in a first step. Next, the plasma processing apparatus executes the second process (step S12). The plasma processing apparatus forms a second film in the second step. A second film is formed to cover the first film. Here, the deposition of the second film is performed by setting processing conditions so that the amount of the second film deposited on the side surface of the opening varies according to the size of the opening on the object to be processed. Also, the deposition of the second film is performed by setting the processing conditions so that the etching rate is lower than that of the first film. Next, the plasma processing apparatus performs an etching process (step S13). In the etching step, the plasma processing apparatus is configured to etch a portion of the first film from above the second film on at least a portion of the processing target on which the first and second films are sequentially formed. Etching is performed under predetermined process conditions until removed. Then, the plasma processing apparatus determines whether or not the processing target satisfies a predetermined condition (step S14). When it is determined that the predetermined condition is not satisfied (step S14, No), the plasma processing apparatus returns to step S11 and repeats the process. On the other hand, when it is determined that the predetermined condition is satisfied (step S14, Yes), the plasma processing apparatus ends the processing. This is an example of the flow of plasma processing according to the first embodiment.

<LCDU improvement using loading effect and selection ratio>
The plasma processing according to the first embodiment will be further described with reference to FIGS. 2A to 2E. FIG. 2A is a schematic cross-sectional view of an example of an object to be processed by plasma processing according to the first embodiment. FIG. 2B is a schematic top view of the processing object shown in FIG. 2A.

The object to be processed shown in FIG. 2A includes a substrate SB, a layer to be etched EL, and a mask layer MK. A layer to be etched EL and a mask layer MK are sequentially formed on the substrate SB. A predetermined pattern is formed on the mask layer MK. As shown in FIG. 2B, when viewed from above, the predetermined pattern is formed of a plurality of substantially perfect circles, and the plurality of substantially perfect circles are aligned at predetermined intervals. The three openings on line V1-V1 in FIG. 2B are indicated by O1, O2 and O3, respectively. Widths of the openings O1, O2 and O3 along the line V1-V1 are denoted by W1, W2 and W3.

Here, in terms of design, the openings O1, O2 and O3 have the same dimensions, and the widths W1, W2 and W3 have the same length. However, when the pattern is formed on the mask layer MK by lithography such as EUVL, the dimensions of each opening may vary. For example, the width dimension of each opening may vary, such as W1<W2, W2>W3, W1<W3.

Therefore, the first step of the above embodiment is executed (FIG. 1, step S11). In one example, the first step is performed by chemical vapor deposition (CVD) using a loading effect material to form the first film. The loading effect is a phenomenon in which the thickness of a film formed differs depending on the density of the pattern. For example, the size of the pattern itself, such as the opening area of the opening, varies the size of the opening after film formation. In addition, the size of the opening after film formation differs depending on the shape and arrangement of patterns around the pattern. Due to the loading effect, the film thickness varies depending on the density of the pattern. Therefore, for example, as shown in FIG. The second film formed on the sidewall T2 of the large opening O2 is thickened (see FIG. 2C). FIG. 2C is a schematic cross-sectional view showing a state in which a first film and a second film are formed on the processing target shown in FIG. 2A. In addition, in FIG. 2C, the film thickness difference is displayed more emphasized than it actually is for the purpose of explanation.

Next, the second step of the above embodiment is performed (FIG. 1, step S12). For example, as in the first step, the second film is formed by CVD using a material having a loading effect. Then, like the first film, a second film is formed that is thin on the side wall T1 and thick on the side wall T2 (see FIG. 2C).

Next, the object to be processed is etched from above the first film and the second film ( FIG. 1 , step S13). First, the second film is etched away and gradually removed. At this time, the second film formed on the sidewall T2 is thicker than the second film formed on the sidewall T1. Therefore, even if the second film on the sidewall T1 is removed by etching, the second film remains on the sidewall T2.

FIGS. 2D and 2E are diagrams (1) and (2), respectively, for explaining removal rates by etching of the first film and the second film deposited on the side wall of the opening. A first film having a film thickness A and a second film having a film thickness B are deposited on the side wall T2 to be processed shown in FIG. 2D. A first film having a thickness of a and a second film having a thickness of b are deposited on the side wall T1 to be processed shown in FIG. 2E. Moreover, the magnitude relationship of the value of each film thickness is A>a and B>b.

First, it is assumed that it takes 12 seconds to etch away the second film (thickness B) on the sidewall T2. It is also assumed that it takes 10 seconds to etch away the second film (thickness b) on the sidewall T1. Then, if etching is performed for 12 seconds on the entire processing object, after the second film is removed on the side wall T2 in 12 seconds, the first film remains without being etched (removed film thickness is B). On the side wall T1, on the other hand, after the second film is removed for 10 seconds, the first film is etched for 2 seconds. Therefore, the film thickness removed on the sidewall T1 is the sum of the film thickness b of the second film and the film thickness α of the first film removed by etching for 2 seconds (the removed film thickness is The film thickness is b+α).

Here, if the etching rate of the first film and the etching rate of the second film are approximately the same, the film thickness removed by etching on the sidewall T1 is the same as the film thickness removed by etching on the sidewall T2. becomes (B=b+α). However, when the etching rate of the first film and the etching rate of the second film are different, there is a difference between the total amount of film thickness removed by etching on the sidewall T1 and the total amount of film thickness removed by etching on the sidewall T2. occurs (B≠b+α).

For example, when the etching rate of the first film is higher than the etching rate of the second film, B<b+α. The change in film thickness on the side wall T2 before and after plasma processing is A+BB=A, while the change in film thickness on the side wall T1 is a+b-(b+α)=a-α becomes. Then, the width W2 of the opening O2 is reduced by 2A, while the width W1 of the opening O1 is reduced by 2a-2α. That is, it is possible to reduce the opening dimension on the side of the wide opening O2 as compared to the side of the narrow opening O1. This effect can be further increased by setting the etching rate such that the value of α is increased. This phenomenon can be used to improve the LCDU to be processed.

FIG. 3 is a diagram for explaining the LCDU improvement effect obtained by the plasma processing method according to the first embodiment. The vertical axis in FIG. 3 indicates the opening size of the opening, and the horizontal axis indicates the processing time. A solid line indicates a change in opening size between the side walls T1 of the opening O1, and a dotted line indicates a change in opening size between the side walls T2 of the opening O2 (see FIG. 2C).

First, in opening O1, when the first step starts at time t0, a first film starts to deposit on sidewall T1. During the first step, the aperture size gradually decreases, and at time t1 when the first step ends, it decreases from WA1 before treatment to WA2. Next, when the second step starts at time t1, the second film starts to deposit on the side wall T1 of the opening O1. During the second step, the aperture size is gradually reduced, and at time t2 when the second step ends, the aperture size is further reduced to WA3.

On the other hand, in opening O2, when the first step starts at time t0, deposition of the first film on side wall T2 begins. During the first step, the aperture size gradually decreases from WB1 before treatment to WB2 at time t1 when the first step ends. Next, when the second step starts at time t1, the second film begins to deposit on the sidewall T2 of the opening O2. During the second step, the aperture size is gradually reduced, and at time t2 when the second step ends, the aperture size is further reduced to WB3.

Next, when the etching process starts at time t2, the second film is gradually removed at the opening O1, and the opening dimension is increased. At time t3, the second film deposited on sidewall T1 of opening O1 is completely removed by etching to expose the first film. Since the first film has a higher etching rate than the second film, after time t3, the speed at which the opening dimension increases, that is, the removal speed of the film by etching increases. The opening dimension of the opening O1 at time t5 when the etching process ends is WA4.

On the other hand, in the opening O2, when the etching process is started at the time t2, the second film is gradually removed similarly to the opening O1, and the opening size is increased. However, since the opening dimension WB1 of the opening O2 at the processing start time t0 is larger than the opening dimension WA1 of the opening O1, the first and second films deposited by the loading effect are thicker than the opening O1. . Therefore, the second film is completely removed from the opening O2 at time t4 after time t3. After time t4, etching of the first film also starts at the opening O2. The opening dimension of the opening O2 at time t5 when the etching process ends is WB4.

As can be seen from FIG. 3, the dimensional difference (WB4 -WA4) is decreasing. In particular, the dimensional difference is quickly reduced in the opening O1 by increasing the etching rate after the removal of the second film (time t3). Therefore, by increasing the etching selectivity between the first film and the second film, the dimensional difference of the opening can be quickly eliminated.

<Relationship between loading effect and LCDU improvement effect>
Next, the relationship between the loading effect and the LCDU improvement effect will be described. For example, as shown in FIG. 2C, it is assumed that an opening O1 and an opening O2 having an opening dimension larger than that of the opening O1 are formed on the object to be processed. The film thickness of the first film deposited in the first step and the film thickness of the second film deposited in the second step are a and b in the opening O1, and A and B in the opening O2. B. Also, the etching selectivity between the first film and the second film (ratio between the etching rate of the first film and the etching rate of the second film, that is, the etching rate of the first film/the etching rate of the second film) rate) is S.

At this time, when the second film is completely removed in the opening O1, the film thickness of the second film remaining in the opening O2 is (Bb). Then, when the second film remaining in the opening O2 is completely removed, the film thickness of the first film remaining in the opening O1 is (a−(S×(B−b) )). Then, the difference between the opening size of the opening O2 and the opening size of the opening O1 is reduced by just (A−(a−(S×(B−b))) (= LCDU improvement amount). Here, substituting Aa=X and Bb=Y into the above equation, the LCDU improvement amount can be expressed by the following equation (1).
(X+(S×Y)) Expression (1)
From equation (1), it can be said that the larger the values of X and Y, the larger the LCDU improvement. That is, for both the first film and the second film, the larger the loading effect (X, Y), the larger the LCDU improvement amount. That is, the larger the film thickness difference (X, Y) between the first film and the second film formed in the openings O1 and O2, the larger the LCDU improvement amount. Also, if there is a loading effect (X, Y) for either the first film or the second film, an improvement in LCDU is expected. Further, when the second film has a loading effect (Y) and the etching selectivity (S) between the first film and the second film is large, a large improvement effect is expected.

<Example without loading effect>
In the example of FIG. 3, by using the loading effect, the film thicknesses of both the first film and the second film formed in the openings O1 and O2 are controlled to be different. Alternatively, for example, the first film may be formed by a method that does not use the loading effect, and only the second film may be formed using the loading effect. For example, the first film may be formed using atomic layer deposition (ALD).

If there is a difference in the film thickness of the second film formed at the opening O1 and the opening O2, the timing at which the etching of the first film starts will be different. It is possible to make a difference in the film thickness of the film etched in . Therefore, even if the first film is formed without using the loading effect, the effect of this embodiment can be enjoyed.

<Etching rate and processing conditions>
FIG. 4 is a diagram for explaining the relationship between film formation conditions and etching resistance. The example shown in FIG. 4 shows that even if the first film and the second film are made of the same material, the selectivity can be obtained. The vertical axis in FIG. 4 indicates the etching rate (nm/min), and the horizontal axis indicates the O2 addition flow rate (sccm) during film formation.

The film forming conditions used in the example of FIG. 4 are as follows. In the following conditions, the applied power indicates the applied power for generating the plasma and the applied power for generating the bias voltage in this order.
・Pressure in chamber 10mT
・Applied power 1000W+0W
・Gas type and flow rate SiCl4/He/O2=25/100/@@sccm
・Processing time 60 seconds

The etching conditions used in the example of FIG. 4 are as follows.
Example 1
・Pressure in chamber 20mT
・Applied power 500W+100W
・Gas type and flow rate C4F8/Ar=40/200sccm
Example 2
・Pressure in chamber 20mT
・Applied power 500W+50W
・Gas type and flow rate Cl2 = 200sccm

As can be seen from the example of FIG. 4, even when the same SiO2 film is formed, the etching rate can be changed by changing the addition flow rate of O2. In the example of FIG. 4, the smaller the O2 addition flow rate, the higher the etching rate, and the higher the O2 addition flow rate, the lower the etching rate. Therefore, it is possible to form the SiO2 film as the first film by setting the O2 addition flow rate to be small, and then form the SiO2 film as the second film by setting the O2 addition flow rate to be large. The etching selectivity for the same SiO2 film can be controlled within a range of about 1 to 17 in the example of FIG. 4, although it varies depending on the type of etching gas.

<Processing sequence example 1>
FIG. 5 is a diagram showing an example of a processing sequence of plasma processing according to the first embodiment. In the first step, a SiO2 film is deposited as a first film by CVD using SiCl4 and O2 as process gases. In the second step as well, a SiO2 film is deposited as a second film by CVD using SiCl4 and O2 as process gases. However, in the second step, the etching rate of the first film is adjusted to be higher than the etching rate of the second film by increasing the flow rate of O2 compared to the first step. The etching process is performed using NF3. Thus, in the plasma processing method according to the first embodiment, the same kind of films can be formed as the first film and the second film by changing the processing conditions in the first step and the second step. .

<Processing sequence example 2>
FIG. 6 is a diagram showing another example of the processing sequence of plasma processing according to the first embodiment. In a first step, a first carbon film is deposited as a first film by CVD using a first type of carbon-containing gas as a process gas. The first type of carbon-containing gas is, for example, a CF-based gas. A first type of carbon-containing gas is, for example, C4F8, C4F6, and the like. Also, the first type of carbon-containing gas is, for example, a CHF-based gas. A first type of carbon-containing gas is, for example, CH2F2, CH3F, and the like. In a second step, a second carbon film is deposited as a second film by CVD using a second type of carbon-containing gas as a process gas. The second type of carbon-containing gas is, for example, a CH-based gas such as CH4. The etching process is performed using O2. A noble gas such as Ar may be used in the first step, the second step and the etching step.

<Processing Sequence Example 3>
FIG. 7 is a diagram showing still another example of the processing sequence of plasma processing according to the first embodiment. In the first step, a carbon film is deposited as a first film by CVD using a carbon-containing gas as a process gas. For example, a CF-based, CH-based, CHF-based gas, or the like can be used as the processing gas. In the second step, a SiO2 film is deposited as a second film by CVD using SiCl4 and O2 as process gases. The etching process is performed using NF3.

As described above, the plasma processing method according to the first embodiment can be performed by combining various gas species. Also, the film type of the first film and the second film may be the same.

<Number of cycles>
In the plasma processing method according to the first embodiment, the first step, the second step and the etching step are regarded as one cycle, and a plurality of cycles are performed until predetermined conditions are satisfied. The predetermined condition is, for example, that the dimensional difference between the plurality of openings formed on the processing target is equal to or less than a predetermined value, or that a predetermined number of cycles have been performed.

<Membrane type, gas type, etc.>
In the first embodiment, the film types of the first film and the second film are SiO2, carbon-containing films (for example, CF-based, CH-based, CHF-based), and the like. However, the first film and the second film are not limited to this, and may be silicon-containing films such as silicon oxide (SiOx), silicon nitride (SiN), silicon carbide (SiC), and silicon (Si). Also, the first film and the second film may be, for example, a titanium (Ti)-containing film or a tungsten (W)-containing film. Also, the first film and the second film may be, for example, boron-containing films.

As for the type of gas used in the etching process, a halogen-containing gas is suitable when the film to be etched contains silicon or metal. Moreover, when the film to be etched is a carbon-containing film, an oxygen-containing gas can be used as the etching gas.

<Etching method>
Also, isotropic and anisotropic etching, plasma etching, atomic layer etching (ALE), etc., can be used to etch the sidewalls in the etching process. In the etching step, the etching conditions may be changed when the second film is removed and at least a portion of the first film is exposed. For example, by changing the etching process conditions from the first process conditions suitable for etching the second film to the second process conditions suitable for etching the first film, the first film is removed by etching. You can speed it up even more. For example, when the first film is at least partially exposed, the etching gas species may be changed to increase the etching rate of the first film.

By modifying the first embodiment, the mask layer MK (see FIG. 2A) itself is used as the first film, and after depositing a film having a lower etching rate than the mask layer on the mask layer MK, , etching may be performed. The LCDU may be improved by varying the etching amount of the mask layer MK depending on the position. Also, instead of the two layers of the first film and the second film, two or more layers of films may be formed. Also, in that case, a difference in etching rate may be provided between the films. Also in this case, the etching rate is set so that the outer film has a lower etching rate.

In the above-described first embodiment, the pattern in which a plurality of perfect circles are aligned as shown in FIGS. 2A and 2B has been described as an example. However, the present embodiment is not limited to patterns having the shapes shown in FIGS. 2A and 2B, and can be applied to improve variations in LCDU and line shapes of elliptical patterns. For example, the present embodiment can be applied to improve LER (Line Edge Roughness) and LWR (Line Width Roughness).

<Effects of the First Embodiment>
The plasma processing method according to the first embodiment includes a first step, a second step, and an etching step. In the first step, the plasma processing apparatus forms a first film on a processing target having a plurality of openings having a predetermined pattern. In the second step, the plasma processing apparatus is configured such that the film thickness on the side surface of the opening differs depending on the size of the opening, and the etching rate is lower than that of the first film. A second membrane is formed. In the etching step, the plasma processing apparatus performs etching under predetermined processing conditions from above the second film until a portion of the first film is removed from at least a portion of the object to be processed. Therefore, according to the plasma processing method according to the first embodiment, the LCDU can be improved by utilizing the loading effect and the difference in etching rate between the first film and the second film. The plasma processing method according to the first embodiment can be applied, for example, to LCDU improvement of patterns manufactured using extreme ultraviolet lithography (EUVL).

Further, in the plasma processing method according to the first embodiment, the plasma processing apparatus changes the predetermined processing conditions to the first processing conditions when the first film is exposed on at least part of the processing object in the etching process. to the second processing condition. For example, the plasma processing apparatus changes the first processing conditions suitable for etching the second film to the second processing conditions suitable for etching the first film, thereby removing the first film by etching. You can speed it up even more. Therefore, the plasma processing apparatus can further improve the LCDU improvement effect.

Moreover, in the plasma processing method according to the first embodiment, the plasma processing apparatus repeatedly executes the first process, the second process, and the etching process until it is determined that a predetermined condition is satisfied. Therefore, the plasma processing apparatus can perform processing until a desired LCDU is achieved.

<Modification 1—Formation of Gradient Composition Film>
In the first embodiment, the LCDU is improved by etching after forming the first film and the second film. In Modification 1, by changing the deposition conditions while depositing only one layer, an effect equivalent to that of forming two films, the first film and the second film, in the first embodiment can be obtained. obtain.

FIG. 8 is a flow chart showing an example of the flow of plasma processing according to Modification 1. As shown in FIG. The plasma processing according to Modification 1 is performed, for example, by a plasma processing apparatus (see FIG. 15), which will be described later.

First, as in the plasma processing according to the first embodiment (see FIG. 1), a processing target (for example, a wafer) having a plurality of openings having a predetermined pattern is placed in a space where plasma processing is performed. do. The plasma processing apparatus performs a deposition process (step S81). In the deposition process, the plasma processing apparatus deposits a film on a pattern under processing conditions in which the etching rate of the deposited film gradually decreases as the distance from the object to be processed increases. It is to be noted that the film deposited in the deposition process has a different film thickness depending on the dimension of the opening due to the loading effect. Next, the plasma processing apparatus performs an etching process (step S82). Then, the plasma processing apparatus determines whether or not the processing target satisfies a predetermined condition (step S83). When it is determined that the predetermined condition is not satisfied (step S83, No), the plasma processing apparatus returns to step S81 and repeats the process. On the other hand, when it is determined that the predetermined condition is satisfied (step S81, Yes), the plasma processing apparatus ends the processing. This is an example of the plasma processing flow according to Modification 1. FIG.

<Processing sequence example 1>
FIG. 9 is a diagram showing an example of a processing sequence of plasma processing according to Modification 1. As shown in FIG. In the example of FIG. 9, a SiO2 film is deposited in the same manner as in the example of FIG. First, in the deposition step, a SiO2 film is deposited by CVD using, for example, SiCl4 and O2 as processing gases. The O2 flow rate is gradually increased during the deposition process. Therefore, in the sequence of FIG. 9, the etching rate of the SiO2 film formed on the processing target gradually decreases (see FIG. 4). The flow rate of SiCl4 is constant during the deposition process. After the deposition step, an etching step is performed by generating a plasma from NF3 gas. Thus, in the plasma processing method according to Modification 1, the etching rate of one film can be gradually changed by changing the processing conditions during the deposition process. For example, in the plasma processing method, a film can be deposited while the etching rate is continuously changed by gradually changing the ratio of a plurality of gases that are components of the film. Moreover, in the plasma processing method, the etching rate of one film can be gradually changed by increasing the flow rate of a predetermined gas.

<Processing sequence example 2>
FIG. 10 is a diagram showing another example of the processing sequence of plasma processing according to Modification 1. In FIG. In the example of FIG. 10, the film is deposited using two types of carbon-containing gases as in the example of FIG. However, unlike the example of FIG. 6, in the example of FIG. 10, the flow rate of the first carbon-containing gas is gradually decreased while the flow rate of the second carbon-containing gas is gradually increased during the deposition process. . Therefore, the deposited film has a strong property of the first carbon-containing gas at the start of the process, and gradually becomes a film having a strong property of the second carbon-containing gas. For example, as shown in FIG. 6, when the etching rate of the first carbon film is higher than the etching rate of the second carbon film, the process of FIG. A film can be deposited. The first carbon-containing gas is, for example, a CF-based gas (C4F8, C4F6, etc.) or a CHF-based gas (CH2F2, CH3F, etc.). Also, the second carbon-containing gas is, for example, a CH-based gas (CH4, etc.).

<Processing Sequence Example 3>
FIG. 11 is a diagram showing still another example of the processing sequence of the plasma processing according to Modification 1. As shown in FIG. In the example of FIG. 11, a film is deposited using the same process gas as in the example of FIG. However, unlike the example of FIG. 7, in the example of FIG. 11, the flow rate of the carbon-containing gas is gradually decreased while the flow rates of SiCl4 and O2 are gradually increased during the deposition process. Therefore, the deposited film is a carbon film at the start of the process, and gradually changes in composition to an SiO2 film. Therefore, by the process of FIG. 11, a film whose etching rate gradually decreases from the lower layer to the upper layer can be deposited.

As in the first embodiment, each sequence of Modification 1 can be repeated for an arbitrary number of cycles until the desired LCDU is achieved.

<Effect of Modification 1>
The plasma processing method according to Modification 1 includes a deposition process and an etching process. In the deposition process, the plasma processing apparatus is arranged such that the etching rate of a processing object having a plurality of openings having a predetermined pattern decreases as the distance from the processing object increases, and the number of openings increases according to the size of the openings. Films are deposited under processing conditions that result in different amounts of deposition on the sides. A plasma processing apparatus performs etching of a processing target on which a film is deposited in an etching process. Therefore, according to the plasma processing method according to Modification 1, it is possible to create a difference in etching rate by depositing one film under different processing conditions. Therefore, according to the plasma processing method according to Modification 1, the LCDU can be improved with a small number of steps.

Further, according to the plasma processing method according to Modification 1, the plasma processing apparatus deposits a film whose etching rate changes continuously by gradually changing the ratio of a plurality of supplied gases in the deposition process. For example, the plasma processing apparatus gradually increases the oxygen content of the supplied gas. Therefore, according to Modification 1, the plasma processing apparatus can improve the LCDU by simple processing.

Further, in the plasma processing method according to Modification 1, the deposition process and the etching process are repeatedly performed until it is determined that the predetermined condition is satisfied. Therefore, according to Modification 1, the LCDU can be improved to a desired level.

<Modification 2—Adjustment of etching rate by modification>
In Modification 1, the etching rate is changed in one film by changing the flow rates of the components when forming the film. In Modified Example 2, a modification process is performed on the formed film to form a first film, thereby making a difference in etching rate between the first film and the second film.

FIG. 12 is a flow chart showing an example of the flow of plasma processing according to Modification 2. As shown in FIG. The plasma processing according to Modification 2 is performed, for example, by a plasma processing apparatus (see FIG. 15), which will be described later.

First, as in the plasma processing according to the first embodiment (see FIG. 1), a processing target (for example, a wafer) having a plurality of openings having a predetermined pattern is placed in a space where plasma processing is performed. do. The plasma processing apparatus executes a first process (step S1201). The plasma processing apparatus first deposits a film on the pattern in the first step. Next, the plasma processing apparatus performs modification processing of the deposited film. The modification process is a process for increasing the etching rate of the film by modifying the surface of the film, such as making it brittle. This forms the first film. Next, the plasma processing apparatus executes the second process (step S1202). In the second step, the plasma processing apparatus deposits a second film on the first film by CVD or the like. It should be noted that the second step is executed under the conditions under which the loading effect can be obtained, as in the first embodiment. Next, the plasma processing apparatus performs an etching process (step S1203). Then, the plasma processing apparatus determines whether or not the processing target satisfies a predetermined condition (step S1204). When it is determined that the predetermined condition is not satisfied (step S1204, No), the plasma processing apparatus returns to step S1201 and repeats the process. On the other hand, if it is determined that the predetermined condition is satisfied (step S1204, Yes), the plasma processing apparatus ends the processing. This is an example of the flow of plasma processing according to Modification 2. FIG.

A modification process is, for example, a process of generating plasma without supplying a gas that is a film material. For example, in the first step, first, a nitride film (SiN) is deposited. Thereafter, hydrogen (H2) plasma is generated to expose the nitride film to the H plasma. Since this treatment makes the film surface fragile, the etching rate increases. However, the combination of the film type and the gas type for plasma generation is not limited to this. For example, after depositing an oxide film (SiO2) in the first step, the reforming process can be performed by generating plasma of hydrogen (H2) and exposing the oxide film to the H plasma.

Note that the modification process may be executed using the loading effect or may be executed without using the loading effect. When utilizing the loading effect, the larger the aperture size, the greater the degree of modification or the depth from the surface to be modified. When the nitride film is modified with H plasma, the portion having a larger surface area is exposed to the plasma at a higher degree. can.

<Effect of Modification 2>
The plasma processing method according to Modification 2 includes a first step, a second step, and an etching step. In the first step, the plasma processing apparatus forms a first film on the processing object in which a plurality of openings having a predetermined pattern are formed. In the second step, the plasma processing apparatus provides a film thickness on the side surface of the opening that differs according to the size of the opening, and a second film that has a lower etching rate than the first film. 2 film is formed. In the etching step, the plasma processing apparatus performs etching under predetermined processing conditions from above the second film until a portion of the first film is removed from at least a portion of the object to be processed. In Modified Example 2, in the first step, the plasma processing apparatus forms a first film having a higher etching rate than the second film by modifying the film deposited on the object to be processed. A modification process is, for example, a process of exposing a film to plasma under predetermined process conditions. Therefore, according to Modification 2, it is possible to deposit the same kind of film as the first and second films and to make the etching rate different by the modification process.

<Modification 3—Formation of second film by modification treatment>
In the modification 2, the etching rate of the first film and the second film are different by performing the modification process. In Modified Example 3, one layer of film is deposited, and modification treatment is performed after the deposition of the film, thereby obtaining an effect equivalent to depositing two films having different etching rates.

FIG. 13 is a flowchart showing an example of the flow of plasma processing according to Modification 3. As shown in FIG. The plasma processing according to Modification 3 is performed by a plasma processing apparatus (see FIG. 15), which will be described later.

First, as in the plasma processing according to the first embodiment (see FIG. 1), a processing target (for example, a wafer) having a plurality of openings having a predetermined pattern is placed in a space where plasma processing is performed. do. The plasma processing apparatus executes the first process (step S1301). The plasma processing apparatus first deposits a film on the pattern in the first step. Although the type of film deposited here is not particularly limited, for example, it is formed by executing CVD using the same type of gas without changing the processing conditions during the process. Next, the plasma processing apparatus executes the second process (step S1302). In the second step, the plasma processing apparatus modifies the film formed in the first step. The modification treatment is treatment for lowering the etching rate of the surface of the film formed in the first step. Also, the modification process is executed under conditions that produce a loading effect. In other words, the larger the opening size, the larger the degree of modification or the depth from the surface to be modified. Next, the plasma processing apparatus performs an etching process (step S1303). Then, the plasma processing apparatus determines whether or not the processing target satisfies a predetermined condition (step S1304). When it is determined that the predetermined condition is not satisfied (step S1304, No), the plasma processing apparatus returns to step S1301 and repeats the process. On the other hand, if it is determined that the predetermined condition is satisfied (step S1304, Yes), the plasma processing apparatus ends the processing. This is an example of the flow of plasma processing according to the third modification.

FIG. 14 is a diagram showing an example of a processing sequence of plasma processing according to Modification 3. As shown in FIG. In the example of FIG. 14, the plasma processing apparatus executes a modify process as a second process after the first process (CVD). After that, the plasma processing apparatus performs an etching process. In the first step in the example of FIG. 14, the plasma processing apparatus deposits a film using methane (CH4) and octafluorocyclobutane (C4F8) as process gases. In the second step, the plasma processing apparatus stops supplying CH4 and C4F8 and supplies rare gases such as argon (Ar), helium (He), nitrogen (N2), and hydrogen (H2) to generate plasma. The film deposited in the first step is compacted and densified by exposure to plasma. Therefore, the second step hardens the film and lowers the etching rate. At this time, since the film deposited in the first step is exposed to the plasma more as the opening size increases, the degree of modification or the modification depth varies depending on the opening size. Therefore, it is possible to obtain substantially the same loading effect as when the second film is deposited by utilizing the loading effect in the first embodiment or the like. After the second step, the plasma processing apparatus supplies O2 to etch the modified film.

Gas species that can be used in the process shown in FIG. 14 are not limited to C4F8 and CH4. In the first step, for example, a gas species containing silicon or carbon may be used to deposit the film. Then, in the second step, after stopping the supply of gas species containing silicon or carbon, a rare gas (such as Ar), hydrogen gas (H2), nitrogen gas (N2), or the like is supplied to generate plasma. may The CVD performed in the first step may be plasma CVD.

<Effect of Modification 3>
In the plasma processing method according to Modification 3, in the second step, the first film is subjected to a modification process to modify the first film, thereby forming the second film. In the modification treatment, the first film is exposed to plasma under treatment conditions such that the larger the size of the opening, the greater the depth from the surface modified by the plasma or the greater the degree of modification. Therefore, according to the plasma processing method according to Modification 3, the etching rate of the film can be varied by changing the properties of the film using the loading effect. For this reason, according to Modification 3, it is possible to obtain the same effect as in the first embodiment, which uses two films, by using one film.

Moreover, in the plasma processing method according to Modification 3, the deposition process and the etching process are repeatedly performed until it is determined that the predetermined condition is satisfied. Therefore, according to the plasma processing method according to Modification 3, a desired LCDU improvement effect can be obtained by adjusting the number of repetitions of the process.

<Example of plasma processing apparatus according to one embodiment>
The plasma processing methods according to the first embodiment and Modifications 1 to 3 can be performed using the plasma processing apparatus 1 described below.

A plasma processing apparatus 1 according to one embodiment will be described with reference to FIG. FIG. 15 is a diagram showing an example of a longitudinal section of the plasma processing apparatus 1 according to one embodiment. In the plasma processing apparatus 1 according to this embodiment, desired plasma processing such as plasma etching, film formation, and sputtering of semiconductor wafers is performed. The plasma processing apparatus 1 according to the present embodiment is a parallel plate type plasma processing apparatus (capacitively coupled plasma processing apparatus) in which a mounting table 20 and a gas shower head 25 are arranged in a chamber 10 so as to face each other. The mounting table 20 also functions as a lower electrode, and the gas shower head 25 also functions as an upper electrode.

The plasma processing apparatus 1 has a cylindrical chamber 10 made of, for example, aluminum whose surface is anodized (anodized). Chamber 10 is electrically grounded. A mounting table 20 for mounting a semiconductor wafer (hereinafter simply referred to as “wafer W”) is provided at the bottom of chamber 10 . A wafer W is an example of an object to be processed. The mounting table 20 has an electrostatic chuck 106 that holds the wafer W by electrostatic adsorption force, and a base 104 that supports the electrostatic chuck 106 . The base 104 is made of, for example, aluminum (Al), titanium (Ti), silicon carbide (SiC), or the like.

An electrostatic chuck 106 for electrostatically attracting a wafer is provided on the upper surface of the base 104 . The electrostatic chuck 106 has a structure in which a chuck electrode 106a is sandwiched between insulators 106b. A DC voltage source 112 is connected to the chuck electrode 106a, and a DC voltage HV is applied from the DC voltage source 112 to the chuck electrode 106a, whereby the wafer W is attracted to the electrostatic chuck 106 by electrostatic force. The upper surface of the electrostatic chuck 106 is formed with a holding surface for holding the wafer W and a peripheral portion that is lower than the holding surface. A wafer W is placed on the holding surface of the electrostatic chuck 106 . Hereinafter, the holding surface of the electrostatic chuck 106 is appropriately referred to as "the mounting surface of the mounting table 20".

A focus ring 108 is arranged on the peripheral edge of the electrostatic chuck 106 so as to surround the wafer W mounted on the mounting surface of the mounting table 20 . The focus ring 108 is made of silicon or quartz, for example. The focus ring 108 functions to improve in-plane etching uniformity.

A coolant flow path 104a is formed inside the mounting table 20 (base 104). A refrigerant inlet pipe 104b and a refrigerant outlet pipe 104c are connected to the refrigerant flow path 104a. A cooling medium such as cooling water or brine (hereinafter also referred to as "refrigerant") output from the chiller 107 flows through the refrigerant inlet pipe 104b, the refrigerant flow path 104a, and the refrigerant outlet pipe 104c and circulates. The cooling medium cools the mounting table 20 and the electrostatic chuck 106 .

A heat transfer gas supply source 85 supplies a heat transfer gas such as helium gas (He) to the back surface of the wafer W on the electrostatic chuck 106 through the gas supply line 130 . With such a configuration, the temperature of the electrostatic chuck 106 is controlled by the coolant circulated in the coolant channel 104a and the heat transfer gas supplied to the back surface of the wafer W. FIG.

A power supply device 30 that supplies two-frequency superimposed power is connected to the mounting table 20 . The power supply device 30 includes a first high-frequency power supply 32 that supplies first high-frequency power (plasma-generating high-frequency power) of a first frequency, and a second high-frequency power (bias voltage generating power) of a second frequency lower than the first frequency. and a second high frequency power supply 34 for supplying high frequency power. The first high frequency power supply 32 is electrically connected to the mounting table 20 via the first matching device 33 . A second high-frequency power supply 34 is electrically connected to the mounting table 20 via a second matching device 35 . The first high frequency power supply 32 applies a first high frequency power of 40 MHz to the mounting table 20, for example. The second high-frequency power supply 34 applies a second high-frequency power of, for example, 400 kHz to the mounting table 20 . Although the first high-frequency power is applied to the mounting table 20 in this embodiment, it may be applied to the gas shower head 25 .

The first matching device 33 matches the internal (or output) impedance of the first high frequency power supply 32 with the load impedance. The second matching device 35 matches the internal (or output) impedance of the second high frequency power supply 34 with the load impedance. The first matching box 33 functions so that the internal impedance of the first high-frequency power supply 32 and the load impedance apparently match when plasma is generated in the chamber 10 . The second matching device 35 functions so that the internal impedance of the second high-frequency power supply 34 and the load impedance apparently match when plasma is generated in the chamber 10 .

The gas shower head 25 is attached so as to block the opening in the ceiling of the chamber 10 via a shield ring 40 covering its peripheral edge. The gas showerhead 25 may be electrically grounded as shown in FIG. Alternatively, a variable DC power supply may be connected to apply a predetermined direct current (DC) voltage to the gas shower head 25 .

The gas shower head 25 is formed with a gas introduction port 45 for introducing gas. Inside the gas shower head 25, a central diffusion chamber 50a and an edge diffusion chamber 50b branched from the gas introduction port 45 are provided. A gas output from the gas supply source 15 is supplied to the diffusion chambers 50a and 50b through the gas inlet 45, diffused in the diffusion chambers 50a and 50b, and directed toward the mounting table 20 through a large number of gas supply holes 55. be introduced.

An exhaust port 60 is formed in the bottom surface of the chamber 10 , and the inside of the chamber 10 is exhausted by an exhaust device 65 connected to the exhaust port 60 . Thereby, the inside of the chamber 10 can be maintained at a predetermined degree of vacuum. A gate valve G is provided on the side wall of the chamber 10 . The gate valve G opens and closes the loading/unloading port when loading and unloading the wafer W from the chamber 10 .

The plasma processing apparatus 1 is provided with a control section 100 that controls the operation of the entire apparatus. The control unit 100 has a CPU (Central Processing Unit) 105 , a ROM (Read Only Memory) 110 and a RAM (Random Access Memory) 115 . The CPU 105 executes desired processing such as plasma processing, which will be described later, according to various recipes stored in these storage areas. The recipe includes the process time, pressure (gas exhaust), high-frequency power and voltage, various gas flow rates, chamber internal temperature (upper electrode temperature, chamber side wall temperature, wafer W temperature (electrostatic chuck temperature), the temperature of the refrigerant output from the chiller 107, and the like. Note that these programs and recipes indicating processing conditions may be stored in a hard disk or semiconductor memory. In addition, the recipe may be stored in a portable computer-readable storage medium such as a CD (Compact Disc)-ROM, a DVD (Digital Versatile Disc), etc., and may be set at a predetermined position and read out. .

For example, the controller 100 controls each part of the plasma processing apparatus 1 so as to perform the plasma processing method described above.

Moreover, the plasma processing according to the above embodiments is applicable not only to capacitively coupled plasma (CCP) processing apparatuses but also to other plasma processing apparatuses. Other plasma processing devices include, for example, inductively coupled plasma (ICP) processing, plasma processing devices using radial line slot antennas, helicon wave excited plasma (HWP: Helicon Wave Plasma) processing devices, electron cyclotrons A resonance plasma (ECR: Electron Cyclotron Resonance Plasma) processing device or the like may be used.

It should be considered that the embodiments disclosed this time are illustrative in all respects and not restrictive. The above-described embodiments may be omitted, substituted or modified in various ways without departing from the scope and spirit of the appended claims.

Further, the following additional remarks are disclosed regarding the above embodiments.

(Appendix 1)
a first step of forming a first film on a processing target in which a plurality of openings having a predetermined pattern are formed;
forming a second film having a different film thickness on the side surface of the opening in accordance with the size of the opening and having a lower etching rate than the first film on the object to be processed on which the first film is formed; 2 steps;
an etching step of performing etching under predetermined processing conditions from above the second film until a portion of the first film is removed from at least a portion of the object to be processed;
A plasma processing method comprising:
(Appendix 2)
The plasma processing method according to Supplementary Note 1, wherein the first step includes forming the first film having a higher etching rate than the second film by modifying the film deposited on the object to be processed. .
(Appendix 3)
3. The plasma processing method according to appendix 2, wherein the modification processing exposes the film to plasma under predetermined processing conditions.
(Appendix 4)
The plasma processing method according to Supplementary Note 1, wherein in the second step, the second film is formed by performing a modification process on the first film to modify it.
(Appendix 5)
Appendix 4, wherein the modification treatment exposes the first film to plasma under processing conditions in which the larger the size of the opening, the greater the depth from the surface modified by the plasma or the greater the degree of modification. Plasma treatment method.
(Appendix 6)
6. Any one of Supplementary Notes 1 to 5, wherein in the etching step, the predetermined processing conditions are changed from the first processing conditions to the second processing conditions when the first film is exposed on at least part of the object to be processed. 1. The plasma processing method according to claim 1.
(Appendix 7)
7. The plasma processing method according to any one of appendices 1 to 6, wherein the first step, the second step, and the etching step are repeatedly performed until it is determined that a predetermined condition is satisfied.
(Appendix 8)
A processing condition in which, in a processing object in which a plurality of openings having a predetermined pattern are formed, the etching rate decreases as the distance from the processing object increases, and the amount of deposition on the side surfaces of the openings varies according to the size of the openings. a deposition step of depositing the film at
an etching step of performing etching of a process target on which the film is deposited;
A plasma processing method comprising:
(Appendix 9)
9. The plasma processing method according to claim 8, wherein in the deposition step, the film whose etching rate changes continuously is deposited by gradually changing the ratio of a plurality of gases to be supplied.
(Appendix 10)
10. The plasma processing method according to appendix 9, wherein the oxygen content of the supplied gas is gradually increased in the deposition step.
(Appendix 11)
11. The plasma processing method according to any one of appendices 8 to 10, wherein said deposition step and said etching step are repeatedly performed until it is determined that a predetermined condition is satisfied.
(Appendix 12)
A storage unit that stores a program for executing the plasma processing method according to any one of appendices 1 to 11, a control unit that controls to execute the program,
A plasma processing apparatus comprising:

1 Plasma Processing Apparatus 10 Chamber 15 Gas Supply Source 20 Mounting Table 25 Gas Shower Head 32 First High Frequency Power Supply 34 Second High Frequency Power Supply 65 Exhaust Device 85 Heat Transfer Gas Supply Source 100 Control Part 104 Base 104a Cooling Channel 106 Electrostatic Chuck

Claims (17)

a chamber having a gas inlet and a gas outlet;
a substrate support within the chamber;
a plasma generator configured to generate a plasma within the chamber;
(a) a step of placing a substrate on the substrate support, wherein the substrate includes a processing target having a plurality of openings including a first opening and a second opening; a placing step, wherein the size of the portion is different from the size of the second opening;
(b) A processing condition in which a plurality of portions with different etching rates are formed, the etching rate decreases as the distance from the side surface increases, and the deposition amount on the side surface of the opening varies depending on the size of the opening. depositing a film on the side surface of the opening in
(c) etching the object to be processed after depositing the film to reduce the difference in opening size between the first opening and the second opening; a controller configured to control execution;
A plasma processing apparatus comprising: 2. The apparatus according to claim 1, wherein in the film deposition step, the control unit is configured to control the apparatus so as to deposit a film whose etching rate varies continuously by changing supply ratios of a plurality of gases. The plasma processing apparatus described. The plurality of gases includes oxygen gas,
3. The plasma processing apparatus according to claim 2, wherein the controller is configured to control the apparatus to change the supply ratio by increasing the ratio of the oxygen gas in the plurality of gases. The controller controls the apparatus to form a first film, form a second film on the first film, and perform etching after forming the second film in the film deposition step. 2. The plasma processing apparatus of claim 1, wherein the plasma processing apparatus is configured to control the The control unit etches a part of the second film in the etching step so that a part of the first film is exposed from the second film, and a part of the first film is exposed. 5. The plasma processing apparatus of claim 4 , configured to control the apparatus to continue etching afterward. The plasma processing apparatus according to any one of claims 1 to 5, wherein the control unit is configured to control the apparatus so as to repeat (b) and (c) until a predetermined condition is satisfied. 7. The control unit according to any one of claims 1 to 6, wherein the controller is configured to further control the apparatus to modify the film after the film deposition step and before the etching step. Plasma processing equipment. The controller reduces a difference in opening size between the first opening and the second opening in the film deposition process, and reduces the difference in opening size between the first opening and the second opening in the etching process. The plasma processing apparatus of any one of claims 1 to 7, configured to control the apparatus to further reduce size differences. A plasma processing apparatus,
a chamber having a gas inlet and a gas outlet;
a substrate support within the chamber;
a plasma generator configured to generate a plasma within the chamber;
(a) a step of placing a substrate on the substrate support, wherein the substrate includes a processing target and a pattern having a plurality of openings including a first opening and a second opening; a placing step, wherein the size of one opening is different from the size of the second opening;
(b) forming a first film on the pattern;
(c) forming a second film on the first film, wherein the second film has a lower etching rate than the first film, and the second film is formed in the opening; a forming step in which the film thickness of the side surface of the opening differs depending on the size of the
(d) removing a difference in opening size between the first opening and the second opening by etching the second film under predetermined processing conditions until a portion of the first film is removed; a controller configured to control the apparatus to perform a plasma treatment comprising: a reducing etching step;
A plasma processing apparatus comprising: The control unit deposits the material of the first film and modifies the material of the first film in the step of forming the first film so that the etching rate is higher than that of the second film. 10. The plasma processing apparatus of Claim 9, configured to control the apparatus to form the first film. 11. The plasma processing apparatus of claim 10, wherein the controller is configured to control the apparatus to expose the material of the first film to plasma to modify the material of the first film. The controller is configured to control the device to form the second film by modifying a portion of the material of the first film to form the second film. The plasma processing apparatus according to any one of claims 9-11. (i) the larger the size of the opening, the larger the depth from the surface of the material of the first film to be modified by the plasma; controlling the apparatus to modify a portion of the material of the first film by exposing the material of the first film to plasma under processing conditions such that the degree of modification of the material of the film of 13. The plasma processing apparatus of claim 12, wherein the plasma processing apparatus is configured to: In the etching step of the second film, the control unit changes the predetermined processing conditions from the first processing conditions to the second processing when the first film is exposed in at least part of the object to be processed. 14. The plasma processing apparatus of any one of claims 9-13, configured to control the apparatus to alter conditions. 15. The plasma processing apparatus according to any one of claims 9 to 14, wherein said control unit is configured to control said apparatus so as to repeat (b) to (d) until a predetermined condition is satisfied. The controller reduces a difference in opening size between the first opening and the second opening after the step of forming the second film compared to before the step of forming the first film, 16. The plasma processing apparatus according to any one of claims 9 to 15 , configured to control the apparatus so that the difference in opening size after the step of etching the second film becomes even smaller. The controller reduces a difference in opening size between the first opening and the second opening in the step of forming the first film and the second film, and reduces the difference in opening size between the first opening and the second opening in the etching step. 17. The plasma processing apparatus according to any one of claims 9 to 16 , configured to control the apparatus so that the difference in opening size between the first opening and the second opening is further reduced.

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