JP7345283B2 - Plasma treatment method and plasma treatment device - Google Patents

Description

The following disclosure relates to a plasma processing method and a plasma processing apparatus.

A plasma enhanced atomic layer deposition (PE-ALD) method is known as a type of method for forming a film on a substrate. Various techniques, including PE-ALD, are used to pattern semiconductor devices.

For example, a method using ALD has been proposed in which film formation is selectively promoted depending on the position of an opening formed in a substrate to be processed (Patent Document 1). Furthermore, a method has been proposed in which a SAM (Self-assembled monolayer) is selectively formed and then vapor phase etching is performed (Patent Document 2). Furthermore, a method for selectively forming a film on 3D nanostructures using ion implantation has been proposed (Non-Patent Document 1).

US Patent Application Publication No. 2017/0140983 US Patent Application Publication No. 2017/0148642

Woo-Hee Kim et al., “A Process for Topographically Selective Deposition on 3D Nanostructures by Ion Implantation” ACS Nano 2016, 10, 4451-4458.

The present disclosure provides a technique that can achieve precise dimensional control of a pattern formed on a substrate.

A plasma processing method performed by a plasma processing apparatus according to one aspect of the present disclosure includes a first step and a second step. In the first step, the plasma processing apparatus forms a first film having a different thickness on the sidewall of the opening of the processing target depending on the distance between the opposing pair of sidewalls. In the second step after the first step, the plasma processing apparatus performs one or more film forming cycles to form a second film having a different thickness depending on the distance between the opposing sidewall pairs.

According to the present disclosure, precise dimensional control of a pattern formed on a substrate can be achieved.

FIG. 1 is a diagram showing an example of the configuration of a plasma processing apparatus according to an embodiment. FIG. 2A is a diagram for explaining a chemical adsorption step of a precursor gas in ALD. FIG. 2B is a diagram for explaining a precursor gas purge step in ALD. FIG. 2C is a diagram for explaining an activation step using a reactive gas in ALD. FIG. 2D is a diagram for explaining a reaction gas purge step in ALD. FIG. 3A is a diagram (1) for explaining incubation in a plasma processing method according to an embodiment. FIG. 3B is a diagram (2) for explaining incubation in the plasma processing method according to one embodiment. FIG. 3C is a diagram (3) for explaining incubation in the plasma processing method according to one embodiment. FIG. 3D is a diagram (4) for explaining incubation in the plasma processing method according to one embodiment. FIG. 3E is a diagram (5) for explaining incubation in the plasma processing method according to one embodiment. FIG. 3F is a diagram (6) for explaining incubation in the plasma processing method according to one embodiment. FIG. 4A is a diagram for explaining size control of an opening formed in a mask. FIG. 4B is a diagram for explaining an example of an opening formed in a mask. FIG. 4C is a diagram showing an example of a pattern formed when etching is performed using the mask of FIG. 4B. FIG. 5A is a diagram for explaining the XY pattern. FIG. 5B is a diagram for explaining example 1 of dimension control of the XY pattern. FIG. 5C is a diagram for explaining the second example of dimension control of the XY pattern. FIG. 6 is a flowchart illustrating an example of a general flow of a plasma processing method in a plasma processing apparatus according to an embodiment. FIG. 7 is a diagram for explaining an example of the loading effect. FIG. 8A is a diagram (1) for explaining the X>Y shrink effect obtained by the plasma processing method according to one embodiment. FIG. 8B is a diagram (2) for explaining the X>Y shrink effect obtained by the plasma processing method according to one embodiment. FIG. 9 is a diagram showing an example of a combination of materials to be processed to which the plasma processing method of one embodiment is applied. FIG. 10A is a diagram for explaining the first step of the plasma processing method according to Modification 2. FIG. FIG. 10B is a diagram for explaining the second step of the plasma processing method according to Modification 2.

Below, the disclosed embodiments will be described in detail based on the drawings. Note that this embodiment is not limited. Moreover, each embodiment can be combined as appropriate within the range that does not conflict with the processing contents.

<Incubation mechanism in ALD>
Before describing the embodiments, the mechanism of incubation in ALD will be described.

2A to 2D are diagrams for explaining an example of a general ALD flow. FIG. 2A is a diagram for explaining a chemical adsorption step of a precursor gas in ALD. FIG. 2B is a diagram for explaining a precursor gas purge step in ALD. FIG. 2C is a diagram for explaining an activation step using a reactive gas in ALD. FIG. 2D is a diagram for explaining a reaction gas purge step in ALD. ALD typically includes the following four steps, as shown in FIGS. 2A-2D.
(1) Chemical adsorption step in which a processing target (for example, a semiconductor substrate) placed in a processing chamber is exposed to a precursor gas (see Figure 2A)
(2) Purging the precursor gas remaining in the processing chamber (see Figure 2B)
(3) Reaction step of exposing the processing target placed in the processing chamber to the reaction gas (see Figure 2C)
(4) Purging the reaction gas remaining in the processing chamber (see Figure 2D)
In the following description, it is assumed that the reaction step (3) is performed by turning the reaction gas into plasma. In ALD, the above steps (1) to (4) are repeatedly executed to form a film on the processing target. Note that purge steps (2) and (4) are optional steps and do not necessarily have to be performed.

In ALD, a SiO2 film can be deposited on a processing object using, for example, a silicon-containing gas as a precursor gas and an O-containing gas as a reaction gas. In this case, first, in step (1), a processing target placed in a processing chamber is exposed to a silicon-containing gas that is a precursor gas. Then, the silicon-containing gas is chemically adsorbed onto the surface of the object to be treated. The precursor gas remaining in the processing chamber without being chemically adsorbed onto the processing object is purged in step (2). Thereafter, in step (3), the O-containing gas is turned into plasma, and the oxygen radicals react with silicon-containing molecules chemically adsorbed on the object to be treated (oxidizing silicon) to form one layer of SiO2 film. The O-containing gas remaining in the processing chamber is purged in step (4). ALD basically forms a film one layer at a time, and the process stops when there is no surface on which atoms can be chemically adsorbed on the object to be processed, so it is possible to form a conformal film in a self-controlled manner.

By the way, if a factor that inhibits the chemical adsorption of the precursor gas (hereinafter also referred to as an inhibitor) is present on the surface of the processing object, the precursor gas will not be chemically adsorbed to the processing object in step (1) and film formation by ALD will not be performed. do not have. The delay in the start of film formation caused by such inhibitory factors is called incubation. 3A to 3F are diagrams (1) to (6) for explaining incubation in the plasma processing method according to one embodiment.

FIG. 3A shows a state in which a CF film is formed on the surface of the object to be processed by chemical vapor deposition (CVD) using CF (fluorocarbon). In FIG. 3A, fluorine atoms (CF: fluorine atoms covalently bonded to carbon) are indicated by black circles. Furthermore, atoms to be processed (substrate) are indicated by white circles.

FIG. 3B shows an example of a state in which an ALD cycle has been performed once on the processing target shown in FIG. 3A. Since a CF film as an inhibitor exists on the surface to be treated, the precursor gas (silicon-containing gas) is not chemically adsorbed and film formation by ALD is not performed. Conversely, the CF film is gradually removed from the surface to be processed due to the influence of oxygen radicals generated by oxygen plasma during the ALD cycle.

FIG. 3C shows an example of a state in which the ALD cycle has been performed five times on the processing target shown in FIG. 3A. In the example of FIG. 3C, all of the CF film has been removed by five ALD cycles.

3D, FIG. 3E, and FIG. 3F show examples of states in which the ALD cycle is executed 6 times, 8 times, and 10 times for the processing target shown in FIG. 3A, respectively. As shown in FIG. 3C, by performing five ALD cycles, the CF film is removed and the layer beneath the CF film is exposed. Since there is a substance that can chemically adsorb the precursor gas on the surface to be treated in this state, the precursor gas chemically adsorbs and reacts with the reaction gas, and film formation starts as shown in FIG. 3D. Thereafter, as shown in FIGS. 3E and 3F, the film thickness increases each time an ALD cycle is performed. In FIGS. 3D, 3E, and 3F, the circles in the second layer from the top indicate the Si-containing precursor gas, and the circles at the top indicate oxygen atoms.

<X-Y pattern control>
By the way, when manufacturing a semiconductor device, various patterns are formed on a substrate. For example, a plurality of openings having similar shapes may be formed on one substrate. In such cases, precise control of the dimensions of the opening affects the performance of the semiconductor device.

FIG. 4A is a diagram for explaining size control of an opening formed in a mask. The substrate S shown in FIG. 4A is formed by self-aligned double patterning. Therefore, on the surface of the substrate S, there are lines A, B, C, B, A, B, C formed of different types of material A (core), material B (spacer), and material C (fill). , B, and A are arranged in that order. Hereinafter, a line formed using material A will be referred to as line A, a line formed using material B will be referred to as line B, and a line formed using material C will be referred to as line C. Here, consider etching the substrate S using a mask having the shape shown by the dotted line in FIG. 4A. In FIG. 4A, openings O1, O2, O4, O5, O6, and O7 are formed such that their two ends are located on separate lines C, and openings O1, O2, O4, O5, O6, and O7 are formed such that their two ends are located on separate lines A, respectively. An opening O3 to be formed is shown. For convenience of explanation, the longitudinal direction of the line shown in FIGS. 4A to 4C will be referred to as the X1 direction, and the direction across the line will be referred to as the Y1 direction.

If a mask having the shape shown in FIG. 4A can be formed, there will be no major problem in the shape of a pattern formed by subsequent etching. However, as shown in FIG. 4B, suppose that the opening of the mask is formed at a position shifted from the desired position in the Y1 direction. FIG. 4B is a diagram for explaining an example of an opening formed in a mask. In this case, when the substrate S is etched using the mask, the position of the opening formed on the substrate S is further shifted in the Y1 direction, and the opening is not formed to connect the line C, as shown in FIG. 4C. there is a possibility. FIG. 4C is a diagram showing an example of a pattern formed when etching is performed using the mask of FIG. 4B. When a mask as shown in FIG. 4B is formed, in order to prevent defects as shown in FIG. 4C from occurring, it is convenient if the dimensions of the opening of the mask once formed can be adjusted. In particular, in the case of the mask having the shape shown in FIG. 4A, the size control in the long side direction of the opening has more influence on the subsequent wiring formation than the size control in the short side direction. Such a substantially rectangular opening having short sides and long sides when viewed from above is sometimes referred to as an XY pattern.

FIG. 5A is a diagram for explaining the XY pattern. FIG. 5A is a partial top view of an XY pattern formed on a substrate. The substrate shown in FIG. 5A is formed with a plurality of substantially rectangular openings aligned in a top view. The plurality of openings have substantially the same dimensions. Note that the XY pattern may not only have a substantially rectangular shape when viewed from above, but may also have a substantially elliptical shape when viewed from above. The XY pattern refers to a pattern that has different dimensions in two orthogonal directions (X direction and Y direction) when viewed from above.

FIG. 5B is a diagram for explaining example 1 of dimension control of the XY pattern. FIG. 5C is a diagram for explaining the second example of dimension control of the XY pattern. The example in FIG. 5B is a control example in which the opening size on the long side Y is reduced while maintaining the opening size on the short side X (X<Y shrink: the opening is ). In the example of FIG. 5B, after the XY pattern is formed, a film is formed on the substrate so that the Y side becomes shorter. On the other hand, the example in FIG. 5C is a control example in which the opening size on the long side Y is maintained while reducing the opening size on the short side (make the opening smaller). In the example of FIG. 5C, after the XY pattern is formed, a film is formed on the substrate so that the X sides are shortened.

In order to prevent the defects shown in Figure 4C from occurring, it is possible to minimize the amount of decrease in the Y side of the opening by executing X>Y shrinkage (Figure 5C) of the opening in the mask shown in Figure 4B. It would be good if possible.

<Embodiment>
In view of the above, in the plasma processing apparatus according to the present embodiment, after forming a first film by CVD having a film thickness difference depending on the state of a pattern formed on a substrate, the first film is formed with an inhibitor. A second film is formed by performing an ALD cycle using a material that functions as a film. The plasma processing apparatus forms a first film having a difference in film thickness by CVD, for example, using a loading effect. After that, when an ALD cycle is executed, the first film is gradually scraped away by the influence of the plasma, but an incubation time is required depending on the thickness of the first film. For this reason, for example, the second film is formed thinly at a position where the first film is formed thickly, and the second film is formed thickly at a position where the first film is formed thinly. . In this manner, the plasma processing apparatus according to this embodiment utilizes incubation and loading effects to achieve precise dimensional control.

<An example of a plasma processing apparatus according to an embodiment>
FIG. 1 is a diagram showing an example of the configuration of a plasma processing apparatus 10 according to an embodiment. As shown in FIG. 1, for example, the plasma processing apparatus 10 in this embodiment is made of aluminum or the like whose surface has been anodized, and has a chamber 21 that defines a substantially cylindrical processing space inside. Chamber 21 is safety grounded. The plasma processing apparatus 10 in this embodiment is configured, for example, as a capacitively coupled parallel plate plasma processing apparatus. A support stand 23 is arranged within the chamber 21 with an insulating plate 22 formed of ceramics or the like interposed therebetween. A susceptor 24 is provided on the support base 23 and is made of, for example, aluminum and functions as a lower electrode.

An electrostatic chuck 25 is provided approximately at the upper center of the susceptor 24 to attract and hold a semiconductor wafer W, which is an example of a processing target, by electrostatic force. The electrostatic chuck 25 has a structure in which an electrode 26 made of a conductive film or the like is sandwiched between a pair of insulating layers. A DC power source 27 is electrically connected to the electrode 26 . Note that the electrostatic chuck 25 may be provided with a heater (not shown) for heating the semiconductor wafer W.

A focus ring 25a is arranged above the susceptor 24 so as to surround the electrostatic chuck 25. The focus ring 25a improves the uniformity of plasma near the edge of the semiconductor wafer W. The focus ring 25a is made of, for example, single crystal silicon. An inner wall member 28 is provided around the support base 23 and the susceptor 24 so as to surround the support base 23 and the susceptor 24. The inner wall member 28 is made of, for example, quartz and has a substantially cylindrical shape.

A refrigerant chamber 29 is formed inside the support base 23, for example, along the circumferential direction of the support base 23. A refrigerant at a predetermined temperature is circulated and supplied to the refrigerant chamber 29 from an externally provided chiller unit (not shown) via piping 30a and piping 30b. By circulating the refrigerant at a predetermined temperature in the refrigerant chamber 29, the temperature of the semiconductor wafer W on the electrostatic chuck 25 can be controlled to a predetermined temperature through heat exchange with the refrigerant. Further, heat transfer gas supplied from a gas supply mechanism (not shown) is supplied between the top surface of the electrostatic chuck 25 and the back surface of the semiconductor wafer W placed on the electrostatic chuck 25 via the piping 31. Ru. The heat transfer gas is, for example, helium gas.

Above the susceptor 24 functioning as a lower electrode, an upper electrode 40 is provided so as to face the susceptor 24 across the processing space in the chamber 21 . A space between the upper electrode 40 and the susceptor 24 and surrounded by the chamber 21 is a processing space in which plasma is generated. The upper electrode 40 includes a top plate 42 that functions as an electrode main body, and a top plate support portion 41 that supports the top plate 42.

The top plate support section 41 is supported on the upper part of the chamber 21 via an insulating member 45. The top plate support portion 41 is formed into a substantially disk shape and made of a conductive material with relatively high thermal conductivity, such as aluminum whose surface is anodized. Further, the top plate support portion 41 also functions as a cooling plate that cools the top plate 42 heated by the plasma generated in the processing space. The top support part 41 includes a gas introduction port 46 for introducing processing gas, a diffusion chamber 43 for diffusing the processing gas introduced from the gas introduction port 46, and a diffusion chamber 43 for dispersing the processing gas diffused into the diffusion chamber 43 downward. A plurality of flow ports 43a, which are flow paths for allowing flow to flow, are formed.

The top plate 42 is made of a silicon-containing material such as quartz and has a substantially disk shape. A plurality of gas introduction ports 42a are formed in the top plate 42, passing through the top plate 42 in the thickness direction of the top plate 42. Each gas introduction port 42a is arranged so as to communicate with any one of the flow ports 43a of the top plate support section 41. Thereby, the processing gas supplied into the diffusion chamber 43 is diffused and supplied into the chamber 21 through the flow port 43a and the gas introduction port 42a in the form of a shower.

A plurality of valves 50a to 50c are connected to the gas inlet 46 of the top support portion 41 via piping 47. A gas supply source 48a is connected to the valve 50a via a mass flow controller (MFC) 49a. When the valve 50a is controlled to be in the open state, the processing gas supplied from the gas supply source 48a is supplied into the chamber 21 through the pipe 47 with the flow rate controlled by the MFC 49a. The gas supply source 48a supplies, for example, a precursor gas into the chamber 21.

Further, a gas supply source 48b is connected to the valve 50b via an MFC 49b. When the valve 50b is controlled to be open, the gas supplied from the gas supply source 48b is supplied into the chamber 21 through the pipe 47 with the flow rate controlled by the MFC 49b. The gas supply source 48b supplies purge gas into the chamber 21, for example. As the purge gas, for example, an inert gas such as argon gas or nitrogen gas is used.

Further, a gas supply source 48c is connected to the valve 50c via an MFC 49c. When the valve 50c is controlled to be open, the gas supplied from the gas supply source 48c is supplied into the chamber 21 through the pipe 47 with the flow rate controlled by the MFC 49c. The gas supply source 48c supplies, for example, a reaction gas into the chamber 21.

In addition, when supplying the precursor gas and the reactive gas to the chamber 21, an additive gas is added for the purpose of productivity such as reducing the usage amount of the precursor gas and the reactive gas and making the gas distribution uniform inside the chamber 21. may be used. As the additive gas, for example, an inert gas such as argon gas or nitrogen gas can be used. For example, an inert gas supplied from gas supply source 48b via valve 50b and MFC 49b may be added to the precursor gas supplied from gas supply source 48a via valve 50a and MFC 49b. Further, for example, an inert gas supplied from the gas supply source 48b via the valve 50b and the MFC 49b may be added to the reaction gas supplied from the gas supply source 48c via the valve 50c and the MFC 49c.

Adjustment of the flow rate of each gas by each of the MFCs 49a to 49c and opening and closing of each of the valves 50a to 50c are controlled by a control device 60, which will be described later.

A high frequency power source 52 is electrically connected to the upper electrode 40 via a matching box 51. The high frequency power supply 52 supplies high frequency power (HF) for plasma excitation of about 40 MHz to the upper electrode 40, for example. The high frequency power supplied from the high frequency power supply 52 is controlled by a control device 60, which will be described later.

A high frequency power source 34 is electrically connected to the susceptor 24 functioning as a lower electrode via a matching box 33. The high frequency power supply 34 applies high frequency power (LF: Low Frequency) for bias to the susceptor 24 . The high frequency power supply 34 supplies high frequency power at a frequency of 13.56 MHz or lower, for example, 2 MHz, to the susceptor 24 via the matching box 33. By supplying high frequency power to the susceptor 24, active species such as ions in the plasma are drawn into the semiconductor wafer W on the electrostatic chuck 25. The high frequency power supplied from the high frequency power supply 34 is controlled by a control device 60, which will be described later.

An opening 78 is formed in the side wall of the chamber 21, and the pipe 38 is connected to the opening 78. The piping 38 is branched into two, one end of which is connected to a valve 37a, and the other end is connected to one end of a valve 37b. The other end of the valve 37a is connected to a pressure gauge 36a via a pipe 38a, and the other end of the valve 37b is connected to a pressure gauge 36b via a pipe 38b. The pressure gauges 36a and 36b are, for example, capacitance manometers.

By controlling the valve 37a to an open state, the pipe 38 and the pipe 38a communicate with each other. Thereby, the pressure gauge 36a is exposed to the processing space inside the chamber 21 through the opening 78 formed in the side wall of the chamber 21. Thereby, the pressure gauge 36a can measure the pressure within the processing space. On the other hand, by controlling the valve 37a to a closed state, that is, to a closed state, the pipe 38 and the pipe 38a are cut off. Thereby, the pressure gauge 36a is shielded from the processing space within the chamber 21.

In addition, by controlling the valve 37b to be in an open state, the pipe 38 and the pipe 38b communicate with each other. Thereby, the pressure gauge 36b is exposed to the processing space in the chamber 21 through the opening 78 formed in the side wall of the chamber 21. Thereby, the pressure gauge 36b can measure the pressure within the processing space. On the other hand, by controlling the valve 37b to a closed state, the pipe 38 and the pipe 38b are cut off. Thereby, the pressure gauge 36b is shielded from the processing space within the chamber 21. Opening and closing control of the valves 37a and 37b is performed by a control device 60, which will be described later.

An exhaust port 71 is provided at the bottom of the chamber 21 , and an exhaust device 73 is connected to the exhaust port 71 via an exhaust pipe 72 . The exhaust device 73 includes a vacuum pump such as a DP (Dry Pump) or a TMP (Turbo Molecular Pump), and can reduce the pressure inside the chamber 21 to a desired degree of vacuum. The displacement of the exhaust device 73 and the like are controlled by a control device 60, which will be described later. For example, when the precursor gas is supplied into the chamber 21 from the gas supply source 48a, the control device 60 controls the valve 37a to be open and the valve 37b to be closed. Then, the pressure in the chamber 21 is controlled to a predetermined pressure by controlling the exhaust amount of the exhaust device 73, etc. based on the pressure in the chamber 21 measured by the pressure gauge 36a. Further, for example, when a reaction gas is supplied into the chamber 21 from the gas supply source 48c, the control device 60 controls the valve 37a to be in a closed state and the valve 37b to be in an open state. Then, the pressure in the chamber 21 is controlled to a predetermined pressure by controlling the exhaust amount of the exhaust device 73, etc. based on the pressure in the chamber 21 measured by the pressure gauge 36b.

An opening 74 for loading and unloading the semiconductor wafer W is provided in the side wall of the chamber 21 . The opening 74 can be opened and closed by a gate valve G. Further, a deposit shield 76 is detachably provided on the inner wall of the chamber 21 along the wall surface. Further, a deposit shield 77 is detachably provided on the outer circumferential surface of the inner wall member 28 along the outer circumferential surface of the inner wall member 28 . The deposit shields 76 and 77 prevent reaction byproducts (deposits) from adhering to the inner wall of the chamber 21 and the inner wall member 28. A conductive member (GND block) 79 connected to the ground is provided at a position of the deposit shield 76 at approximately the same height as the semiconductor wafer W placed on the electrostatic chuck 25 . The GND block 79 prevents abnormal discharge within the chamber 21 .

The operation of the plasma processing apparatus 10 described above is totally controlled by the control device 60. The control device 60 includes a memory 61 such as a ROM (Read Only Memory) or a RAM (Random Access Memory), a processor 62 such as a CPU (Central Processing Unit) or a DSP (Digital Signal Processor), and a user interface 63. have The user interface 63 includes, for example, a keyboard through which a user such as a process manager inputs commands to manage the plasma processing apparatus 10, a display that visualizes and displays the operating status of the plasma processing apparatus 10, and the like.

The memory 61 stores recipes including process condition data and the like for realizing various processes in the plasma processing apparatus 10, and control programs (software). Then, the processor 62 controls each part of the plasma processing apparatus 10 by reading an arbitrary recipe from the memory 61 and executing it in response to an instruction from the user via the user interface 63. Thereby, desired processing such as film formation is performed by the plasma processing apparatus 10. Note that recipes and control programs containing processing condition data, etc. may be stored in a computer-readable recording medium, or may be transmitted from another device, for example, via a communication line. It is also possible to use things. Examples of computer-readable recording media include hard disks, CDs (Compact Discs), DVDs (Digital Versatile Discs), flexible disks, and semiconductor memories.

Note that although a plasma processing apparatus 10 using capacitively coupled plasma (CCP) as a plasma source will be described here as an example, the disclosed technology is not limited to this; Plasma processing apparatus 10 using any plasma source such as plasma or microwave plasma can be employed.

<Example of flow of plasma processing method according to one embodiment>
FIG. 6 is a flowchart illustrating an example of the general flow of a plasma processing method in the plasma processing apparatus 10 according to an embodiment.

First, a processing target (for example, a wafer W) is placed in the chamber 21 of the plasma processing apparatus 10 . The plasma processing apparatus 10 first forms a mask layer on the surface of the processing target (step S61). Next, the plasma processing apparatus 10 forms a pattern on the mask layer by etching (step S62). The pattern includes, for example, openings having an XY pattern. Here, steps S61 and S62 may not be executed within the plasma processing apparatus 10, but may be executed in another apparatus. For example, after forming a mask layer and a pattern on the wafer W in another apparatus, the wafer W may be moved into the chamber 21 of the plasma processing apparatus 10 and the following process may be performed.

Next, the plasma processing apparatus 10 performs CVD using a gas that forms a film and becomes an inhibitor from above the formed pattern (step S63, first step). By CVD, a first film (hereinafter also referred to as an inhibitor layer) having a thickness that varies depending on the shape of a pattern on the processing target is formed. Next, the plasma processing apparatus 10 executes the ALD cycle a predetermined number of times from above the first film (step S64, second process). The ALD cycle forms a second film on the object to be processed. After that, the plasma processing apparatus 10 determines whether a predetermined condition is satisfied (step S65). If it is determined that the predetermined condition is satisfied (step S65, Yes), the plasma processing apparatus 10 ends the processing. On the other hand, if it is determined that the predetermined condition is not satisfied (step S65, No), the plasma processing apparatus 10 returns to step S63 and repeats the process. This is the general flow of the plasma processing method according to one embodiment. Note that another process may be executed after step S64. In the following description, one process from step S63 to step S64 is also referred to as one sequence.

<Film thickness of first film>
The thickness of the first film forming the inhibitor layer formed by the plasma processing apparatus 10 by CVD is determined by various factors. For example, by utilizing the loading effect, the plasma processing apparatus 10 can form the first film to a desired thickness. The loading effect is a phenomenon in which the thickness of a deposited film varies depending on the coarse density of the pattern. For example, the size of the opening after film formation varies depending on the size of the pattern itself, such as the opening area of the opening. Furthermore, the opening dimensions after film formation vary depending on the shape and arrangement of patterns around the pattern.

One reason why the loading effect occurs is that the aspect ratio of the opening determines the angle at which the deposition material such as gas can enter the opening from the opening side, which in turn determines the amount of deposition material that can enter the opening. It is thought that this is because the FIG. 7 is a diagram for explaining an example of the loading effect. As shown in FIG. 7, when the aspect ratio of the opening on the processing target is small, the penetration angle (Ω) of the material becomes large. On the other hand, if the aspect ratio of the opening is large, the penetration angle of the material will be small. Therefore, the amount of film deposited at each opening varies depending on the angle of entry. As a result, the amount of film formed on the X side of the small opening is smaller than the amount of film formed on the Y side of the large opening.

In this way, the thickness of the first film increases, for example, as the aspect ratio of the opening decreases. Further, for example, the thickness of the first film increases as the solid angle of the opening increases. Further, for example, the thickness of the first film varies depending on the width and depth of the opening. For example, the wider and shallower the opening, the thicker the first film becomes. Further, the thickness of the first film varies depending on the density, line and space (L/S), etc. of the pattern formed on the processing target.

Note that the material of the first film formed in the plasma treatment according to the embodiment is not particularly limited as long as it is a material that inhibits the formation of the second film. For example, the first membrane is a hydrophobic membrane. Further, for example, the first film is a film containing fluorine (F). Further, for example, the first film is a film formed of a gas containing fluorocarbon. Further, for example, the first film is a film formed of a gas that does not contain hydrogen. For example, the first film is a modification film that modifies the surface to be treated.

<Film thickness of second film>
During the formation of the second film, the first film functions as an inhibitor layer and inhibits chemisorption of the precursor gas. Therefore, the thickness of the second film is controlled according to the thickness of the first film.

For example, suppose that the first film is formed thinly on the X side and thickly formed on the Y side due to the loading effect. In this case, if an ALD cycle is performed from above the first film to form the second film, it will take longer to remove the first film on the Y side than it takes to remove the first film on the X side by the ALD cycle. It takes longer for the first film to be removed by the ALD cycle. Then, the timing at which the formation of the second film by the ALD cycle starts on the X side is earlier than the timing at which the formation of the second film by the ALD cycle starts on the Y side. As a result, if the same number of ALD cycles are performed on both the X side and the Y side, the second film formed on the X side will be thicker on the Y side. The film thickness becomes thicker than that of the second film.

For example, assume that the thickness of the first film formed on the Y side is A, and the thickness of the first film formed on the X side is B (where A>B). Then, in the second step (step S64), the thickness of the first film removed per ALD cycle is x, and the thickness of the second film formed per ALD cycle is y. Then, it is assumed that A=10x and B=2x. In this case, if the ALD cycle is executed 12 times in step S64, the thickness of the second film formed on the Y side will be 2y, and the thickness of the second film formed on the X side will be 10y. . However, the amount (thickness) of the first film formed in the first step (step S63) removed in one ALD cycle is the same as the thickness of the second film formed in one ALD cycle. They are not the same (x≠y). Therefore, the processing conditions of the first and second steps, such as processing time and number of cycles, are adjusted in consideration of the amount of first film removed and the amount of second film formed in the second step. can do.

Therefore, if an inhibitor layer having a shape similar to that of the film formed on the substrate in FIG. 5B can be formed using the loading effect, X>Y shrink can be achieved through subsequent ALD cycles. Further, if an inhibitor layer having a shape similar to that of the film formed on the substrate in FIG. 5C can be formed, X<Y shrink can be realized by the subsequent ALD cycle.

FIGS. 8A and 8B are diagrams for explaining the X>Y shrink effect obtained by the plasma processing method according to one embodiment. FIG. 8A schematically shows a state in which steps S63 and S64 shown in FIG. 6 are repeated three times to form the second film on the X side. Further, FIG. 8B schematically shows a state in which steps S63 and S64 shown in FIG. 6 are repeated three times to form the second film on the Y side. In either case, after one CVD is performed to form a CF film in step S63, ALD cycles are repeatedly performed a predetermined number of times in step S64, and the sequence of steps S63 and S64 is repeated three times. did.

As shown in FIG. 8A, on the X side, the length of the X side is reduced by 8.12 nanometers [nm] on average due to the second film formed on the side walls opposite to each other with the X side in between. ing. That is, a second film having an average thickness of 8.12 nanometers is formed on the sidewall. On the other hand, on the Y side, the length of the Y side is reduced by 6.37 nanometers on average due to the second film formed on the side walls facing each other with the Y side in between. That is, a second film having an average thickness of 6.37 nanometers is formed on the sidewall. It can be seen from FIGS. 8A and 8B that by repeatedly performing steps S63 and S64, it is possible to reduce both opening dimensions while decreasing the opening dimension on the X side to a greater extent than the opening dimension on the Y side. That is, it can be seen that X>Y shrink can be achieved. Further, by further increasing the number of times steps S63 and S64 are executed, the X>Y shrinking effect can be increased.

<Examples of substrates and other materials>
The plasma processing method of this embodiment can be applied to processing objects made of various materials.

FIG. 9 is a diagram showing an example of a combination of materials to be processed to which the plasma processing method of this embodiment is applied. Here, a second film is formed by applying the plasma processing method of this embodiment to a processing target in which a layer to be etched and a mask are sequentially formed on a substrate in order to control the dimensions of the mask. do. Note that a stop layer may be formed between the layer to be etched and the substrate.

In this case, for example, a layer to be etched of silicon nitride (SiN), silicon (Si), or silicon germanium (SiGe) can be formed on a silicon substrate, and a mask of silicon dioxide (SiO2) can be formed. In this case, silicon dioxide (SiO2) can be used as the second film.

Moreover, SiO2 can be used for the layer to be etched, SiN can be used for the mask, and SiN can be used for the second film. Furthermore, SiO2 can be used as the layer to be etched, and titanium nitride (TiN), tungsten carbide (WC), or zirconium dioxide (ZrO2) can be used as the mask. In this case, TiN or WC can be used as the second film.

Regardless of the combination of materials, processing can be realized using a device such as a CCP.

Further, the plasma processing method of the above embodiment can be applied not only to a processing object in which an etched layer and a mask are sequentially formed on a substrate, but also to processing objects having other configurations. For example, the present invention can be applied to a processing target in which a layer to be etched, an organic layer, a silicon-containing antireflection layer, etc. are sequentially formed on a silicon substrate, and a mask layer such as a photoresist is formed on the antireflection layer. In this case, for example, a layer formed by multi-patterning may be interposed on the substrate. Then, the pattern dimensions of the mask may be adjusted using the plasma processing method of the above embodiment so that the pattern formed on the mask is aligned with each line of the layer formed by multi-patterning. The plasma processing method of the above embodiment can be used to precisely adjust the positions where vias and contacts are formed by adjusting the pattern dimensions of the mask.

<Effects of embodiment>
The plasma processing method according to the above embodiment includes a first step and a second step. In the first step, the plasma processing apparatus forms a first film having a different thickness on the sidewall of the opening of the processing target depending on the distance between the opposing pair of sidewalls. In a second step after the first step, the plasma processing apparatus performs a film forming cycle one or more times to form a second film having a different thickness depending on the distance between the pair of opposing side walls. Therefore, the plasma processing apparatus can form a second film having a thickness difference depending on the state of the pattern on the processing target. Therefore, even if it is difficult to form a second film having a desired thickness difference in one step, the plasma processing apparatus according to the embodiment can use the loading effect or incubation to obtain the desired thickness. It is possible to form a second film having a film thickness difference of . Therefore, the plasma processing apparatus according to the embodiment can realize precise dimensional control of the pattern formed on the substrate.

Further, in the plasma processing method according to the embodiment, in the first step, the plasma processing apparatus includes a second sidewall pair formed on the processing target on a second sidewall pair facing each other at a narrower interval than the first sidewall pair formed on the processing target. A first film is formed that is thinner than the first film formed on the first pair of sidewalls. Further, in the second step, the plasma processing apparatus forms a second film thicker than a second film formed on the first sidewall pair on the second sidewall pair. Therefore, the plasma processing apparatus according to the embodiment can control the dimensions by adjusting the film thickness for each pair of side walls facing each other at different intervals, and can improve pattern accuracy.

Further, in the plasma processing method according to the embodiment, the plasma processing apparatus forms, in the first step, a first film containing a component that inhibits the formation of the second film in the film forming cycle. Therefore, the plasma processing apparatus according to the embodiment can precisely control the thickness of the second film that is subsequently formed by the thickness of the first film.

Further, in the plasma processing method according to the embodiment, the plasma processing apparatus forms a hydrophobic first film in the first step. Further, in the first step, the plasma processing apparatus forms a first film containing fluorine (F). Further, in the first step, the plasma processing apparatus forms the first film using a gas that does not contain hydrogen but contains fluorocarbon (CF). In this way, the plasma processing apparatus according to the embodiment can form the first film by selecting a material that causes incubation of the second film, and can precisely control the dimensions of the pattern.

Furthermore, in the plasma processing method according to the embodiment, the plasma processing apparatus forms the second film after removing the first film in the second step. Therefore, in the plasma processing apparatus according to the embodiment, the thickness of the second film can be precisely controlled by the thickness of the first film.

Furthermore, in the plasma processing method according to the embodiment, the plasma processing apparatus repeatedly executes the sequence including the first step and the second step one or more times. Therefore, the plasma processing apparatus according to the embodiment can precisely control the thickness of the second film to be formed by adjusting the number of repetitions of the sequence.

Further, the plasma processing method according to the embodiment includes, after the second step, a third step of etching using the second film as a mask. Therefore, the plasma processing apparatus according to the embodiment can perform etching after precisely controlling the dimensions of the second film that is a mask, and can precisely control the dimensions of the pattern formed by etching. be able to.

Furthermore, the pair of sidewalls to be processed in the plasma processing method according to the embodiment includes at least a partially curved surface. Therefore, the plasma processing apparatus according to the embodiment can precisely control the dimensions of not only a linearly formed pattern but also a curved pattern.

Further, in the plasma processing method according to the embodiment, in the second step, the atomic layer deposition cycle is performed one or more times to form the second film. Therefore, the plasma processing apparatus according to the embodiment can easily control the thickness of the second film by utilizing the self-control properties of atomic layer deposition.

Furthermore, in the first step of the plasma processing method according to the embodiment, the plasma processing apparatus forms the first film by chemical vapor deposition or plasma enhanced chemical vapor deposition. Therefore, the plasma processing apparatus according to the embodiment can efficiently perform processing.

Further, in the first step of the plasma processing method according to the embodiment, the plasma processing apparatus includes the aspect ratio, the solid angle, the width and depth of the opening formed on the processing target, the area of the opening, A first film is formed which has a thickness difference depending on at least one of pattern density, line and space. Therefore, the plasma processing apparatus according to the embodiment can precisely control the dimensions of the pattern by using loading effects that occur due to various factors.

Further, the plasma processing method according to the embodiment includes the steps of forming a first film on the processing target, and executing a film formation cycle on the processing target. The film forming cycle uses a precursor gas that does not chemically adsorb to the surface of the first film but chemically adsorbs to the surface to be treated, and a reactive gas that generates radicals that turn into plasma and remove the first film. is executed. Therefore, the plasma processing method according to the embodiment can control the thickness of the film formed in the film formation cycle using the first film. Therefore, the plasma processing method according to the embodiment can precisely control the dimensions of the pattern.

Further, the plasma processing method according to the embodiment includes a process of removing a first predetermined amount of the first film on the processing target, and a process of removing the second film by a second predetermined amount different from the first predetermined amount on the processing target. A film forming cycle including a process of depositing a predetermined amount and a process of simultaneously performing the process using the same gas is executed. Therefore, the plasma processing method according to the embodiment can realize two different processes, ie, film removal and film formation, in one process. Therefore, the plasma processing method according to the embodiment can efficiently control the dimensions of the pattern.

<Modification 1>
Now, in the above embodiment, the incubation time of the film forming cycle, for example, the ALD cycle, is controlled depending on the thickness of the first film. Alternatively, for example, the thickness of the first film may be constant, and the thickness of the second film may be varied by subjecting the first film to a modification process using an ALD cycle.

For example, in step S63 of FIG. 6, instead of forming a first film having a different thickness depending on the shape of the pattern on the processing object, a first film having a uniform thickness is formed on the processing object. do. At this time, as a film forming method, thermal CVD (thermal chemical vapor deposition), a method of supplying two types of organic gases and causing a polymerization reaction under temperature control to form a film, or the like can be used.

Then, in step S64 of FIG. 6, a modification process using the loading effect is executed. For example, during an ALD cycle, a silicon-containing gas is supplied to chamber 21 as a precursor gas in the chemisorption step (see FIG. 2A). Then, in the reaction step (see FIG. 2C), fluorocarbon (CxFy, eg, C4F6)) and an O-containing gas are supplied to the chamber 21 as a reaction gas. A purge step of purging the inside of the chamber 21 may be performed after each of the chemisorption step and the reaction step.

In this case, the silicon-containing gas is not chemically adsorbed at the location where the first film is formed in the chemisorption step, and the first film is removed by the O-containing plasma in the reaction step. Further, in the reaction step, fluorocarbon contained in the reaction gas is deposited on the first film. On the other hand, at locations where the first film (and the fluorocarbon film deposited on the first film) has been removed by the O-containing plasma, silicon-containing gas is chemisorbed in the chemisorption step, and oxygen radicals and oxygen radicals are absorbed in the reaction step. The silicon-containing molecules react to form a SiO2 film.

In the reaction step, among the patterns on the processing target, CxFy is difficult to enter into areas where the pattern is dense, and CxFy is likely to enter into areas where the pattern is sparse. Therefore, the denser the pattern (X side), the smaller the amount of CxFy film formation, and the sparser the pattern (Y side), the more CxFy film formation. Furthermore, O-containing plasma is difficult to enter into areas where the pattern is dense, and O-containing plasma is likely to enter into areas where the pattern is sparse. Therefore, the denser the pattern (X side), the smaller the amount of the first film removed by the O-containing plasma generated from the O-containing gas, and the sparser the pattern (Y side), the smaller the amount of first film removed. will increase. By adjusting the ratio of fluorocarbon and O-containing gas contained in the reaction gas so that the removal rate of the first film on the X side is faster than the removal rate of the first film on the Y side, X>Y A shrinking effect (FIG. 5C) can be obtained. Therefore, the X>Y shrink effect (see FIG. 5C) can also be achieved by the plasma processing method according to the modification.

<Modification 2>
Further, in the above embodiment, the processing conditions of the ALD cycle are such that sufficient processing time is provided to complete self-controlled adsorption and reaction on the surface of the processing target. The present invention is not limited to this, and the processing conditions of the ALD cycle may be set so that self-controlled adsorption and reaction on the surface of the processing target are not completed. For example, so-called unsaturated ALD (hereinafter also referred to as subconformal ALD) may be used in the second step. Subconformal ALD can be realized, for example, in the following two ways.
(1) The precursor is adsorbed onto the entire surface of the object to be treated. The reaction gas introduced thereafter is controlled so as not to spread over the entire surface of the object to be treated.
(2) The precursor is adsorbed only on a part of the surface of the object to be treated. The reaction gas introduced thereafter forms a film only on the surface portion where the precursor is adsorbed.
By utilizing subconformal ALD, the second film can be formed such that the thickness of the second film gradually decreases from the top to the bottom.

FIG. 10A is a diagram for explaining the first step of the plasma processing method according to Modification 2. FIG. FIG. 10B is a diagram for explaining the second step of the plasma processing method according to Modification 2. The XY pattern shown in FIG. 10A is similar to the XY pattern shown in FIG. 5B, but the amount of film deposited on the short side X is set smaller than in the example shown in FIG. 5B.

In the first step of Modified Example 2, CVD is used to control the opening size on the long side Y while maintaining the opening size on the short side X (X<Y shrink). After that, in the second step, control is performed using subconformal ALD to maintain the opening size on the long side Y while reducing the opening size on the short side X (X>Y shrink). At this time, on the short side X, the second film is formed by unsaturated ALD so that the film thickness becomes gradually thinner from the top to the bottom. Further, the second film is not formed on the bottom of the short side X. In this way, by using subconformal ALD, the amount of film deposited on the bottom of the object to be processed can be suppressed. Furthermore, even when subconformal ALD is used, the relationship is maintained that the thicker the first film is, the thinner the second film formed in the same portion is. Therefore, according to this plasma processing method, it is possible to realize dimension control of the XY pattern.

As in Modification 2, the plasma processing method of the present embodiment includes, in the second step, subconformal ALD cycles performed one or more times under processing conditions in which self-limiting adsorption or reaction on the surface of the processing target is not completed. may be applied to form a second film. Therefore, the plasma processing method not only controls the XY pattern, but also suppresses the amount of film formed at the bottom of the pattern, making it possible to easily perform subsequent processing such as etching.

The embodiments disclosed this time should be considered to be illustrative in all respects and not restrictive. The embodiments described above may be omitted, replaced, or modified in various forms without departing from the scope and spirit of the appended claims.

10 Plasma processing device 21 Chamber 24 Susceptor 25 Electrostatic chuck 40 Upper electrodes 48a to 48c Gas supply source 60 Control device 61 Memory 62 Processor 63 User interface 73 Exhaust device W Wafer

Claims (15)

A step of providing a processing object having at least one opening, the side wall of the opening facing in a first direction along a surface of the processing object in which the opening is formed, when viewed from above. a first pair of side walls; and a second pair of side walls facing each other in a second direction along the surface of the processing target in which the opening is formed and perpendicular to the first direction. and the second pair of side walls face each other at a narrower interval than the first pair of side walls;
a first step of forming a first film on the sidewalls of the opening, the first film being thinner than the first film formed on the first pair of sidewalls on the second pair of sidewalls; the first step of forming a film ;
After the first step, a second step of forming a second film on the sidewalls by performing a film formation cycle using plasma one or more times, the second step comprising: forming a second film on the second sidewall pair; the second step of forming a second film that is thicker than the second film formed on the first sidewall pair;
including;
In the first step, the first film is formed by chemical vapor deposition or plasma chemical vapor deposition to form the first film containing a component that inhibits the formation of the second film in the film forming cycle. The first step is to form the first hydrophobic film.
The plasma processing method according to claim 1 . The first step is to form the first film containing fluorine (F).
The plasma processing method according to claim 2 . In the first step, the first film is formed using a gas that does not contain hydrogen and contains fluorocarbon (CF).
The plasma processing method according to claim 3 . The second step is to form the second film after removing the first film.
The plasma processing method according to any one of claims 1 to 4 . repeating a sequence including the first step and the second step one or more times;
The plasma processing method according to any one of claims 1 to 5 . 6. The plasma processing method according to claim 1, further comprising a third step of etching using the second film as a mask after the second step. The plasma processing method according to any one of claims 1 to 7 , wherein the sidewall pair includes at least a partially curved surface. 9. The plasma processing method according to claim 1, wherein in the second step, the second film is formed by performing one or more atomic layer deposition (ALD) cycles. 2. From claim 1, wherein in the second step, the second film is formed by performing one or more subconformal ALD cycles under processing conditions in which self-limiting adsorption or reaction on the surface to be processed is not completed. 8. The plasma processing method according to any one of 8 . The second step is
an adsorption step of exposing the processing target to a precursor gas;
a reaction step of exposing the processing target to a reaction gas;
9. The plasma processing method according to claim 1, wherein the second film is formed by performing a cycle including the steps one or more times. 11. In the adsorption step, the precursor is adsorbed on a part of the surface of the object to be treated, or in the reaction step, the reaction gas is prevented from spreading over the entire surface of the object to be treated. The plasma treatment method described in . The first step includes determining at least one of the aspect ratio, the solid angle, the width and depth of the opening formed on the processing target, the area of the opening, the density of the pattern, and the line and space. forming the first film having a corresponding thickness difference;
The plasma processing method according to any one of claims 1 to 12. A step of providing a processing object having at least one opening, the side wall of the opening facing in a first direction along a surface of the processing object in which the opening is formed, when viewed from above. a first pair of side walls; and a second pair of side walls facing each other in a second direction along the surface of the processing target in which the opening is formed and perpendicular to the first direction. and the second pair of side walls face each other at a narrower interval than the first pair of side walls;
a first step of forming a first film containing fluorine on the sidewall of the opening by plasma chemical vapor deposition;
a second step of forming a second film on the sidewall by performing a film formation cycle one or more times after the first step;
including;
The film forming cycle is
an adsorption step of exposing the processing target to a precursor gas containing a silicon-containing gas;
a reaction step of exposing the object to be treated to oxygen-containing plasma;
including;
In the first step, a first film that is thinner than a first film formed on the first sidewall pair is formed on the second sidewall pair,
In the plasma processing method, in the second step, a second film that is thicker than a second film formed on the first sidewall pair is formed on the second sidewall pair. A storage unit that stores a program for executing the plasma processing method according to any one of claims 1 to 14, and a control unit that controls the execution of the program.
A plasma processing apparatus comprising:

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