Method for reducing dielectric constant and method for manufacturing semiconductor device

Abstract

Provided are a method for reducing a dielectric constant of a Low-K film, in which the dielectric constant can be appropriately reduced even for a damaged Low-K film that can be considered to be a porous film having a very small pore size, and a method for manufacturing a semiconductor device. The present disclosure relates to a method for reducing the dielectric constant of a Low-K film, the method including a step for processing the Low-K film at a temperature above 100°C using a silylating agent which is a compound represented by the following general formula (1). (1) SiR1 aX4-a In the formula, R1 is same or different and represents a hydrogen atom or an alkyl group. X is the same or different and represents an N(R2)2 group or a halogen atom. R2 is the same or different and represents a hydrogen atom or an alkyl group, and a represents 1 or 2.

Description

Method for reducing dielectric constant and method for manufacturing semiconductor device

[0001] The present disclosure relates to methods for reducing dielectric constant and methods for manufacturing semiconductor devices.

[0002] In the manufacture of semiconductor devices, silicon dioxide films with a dielectric constant of approximately 4 have long been used as insulating films, such as interlayer insulating films. However, in recent years, the demand for higher performance in semiconductor devices has led to their advancement in miniaturization, necessitating the need for insulating films with lower dielectric constants. Under these circumstances, active research and development has been conducted into low-k films with lower dielectric constants, for example, by using organosilicon-based films or other organic films as the film, or by introducing pores into the film (making it porous).

[0003] Low-K films are typically formed using chemical vapor deposition (CVD). However, because CVD is not site-selective, the low-K film is first deposited over a wide area and then patterned using a photoresist process or similar to leave the low-K film only where necessary. In this process, after etching, the photoresist and other mask layers are removed from above the low-K film using dry plasma processing or similar. This damages the exposed low-K film. Specifically, functional groups such as hydroxyl groups, i.e., damaged sites, are generated on the outermost surface of the low-K film and on the surfaces of its internal pores. The dielectric constant of the low-K film increases due to the increase in these functional groups and the moisture adsorbed by these functional groups. There is a need to restore the dielectric constant of low-K films after they have been damaged, and methods for achieving this have been researched and developed (e.g., Patent Documents 1 and 2).

[0004] Recently, low-k films have been developed that have a very low dielectric constant, for example, 2.7 to 2.8. Although such low-k films have a low dielectric constant and are considered to be porous, their porosity cannot be directly observed, and therefore they are considered to be porous films with very small pore diameters.

[0005] JP 2009-158610 A JP 2008-518460 A

[0006] Low-K films, particularly recent low-K films that are considered to be porous films with very low dielectric constants and very small pore diameters, have sometimes been difficult to reduce their dielectric constants again after being damaged by, for example, plasma processing.

[0007] An object of the present disclosure is to provide a method for reducing the dielectric constant of a low-k film, which can suitably reduce the dielectric constant even in a low-k film that is considered to be a porous film with an extremely small pore size, and a method for manufacturing a semiconductor device.

[0008] As a result of extensive research, the present inventors have discovered that the dielectric constant of a low-k film can be suitably reduced by treating the film with a specific polyfunctional silylating agent, and have thus completed the present disclosure.

[0009] The present disclosure (1) relates to a method for reducing the dielectric constant of a low-k film, which includes a step of treating the low-k film at a temperature above 100° C. with a silylating agent, which is a compound represented by the following general formula (1): SiR １ ａ X ４－ａ (1) In the formula, R １ are the same or different and represent a hydrogen atom or an alkyl group; X are the same or different and represent N(R ２ ) ２ group or a halogen atom, R ２ are the same or different and represent a hydrogen atom or an alkyl group; a represents 1 or 2;

[0010] The present disclosure (2) relates to the method for reducing a dielectric constant according to the present disclosure (1), which includes a step of supplying the silylating agent in a gaseous state to a surface of a low-K film at 100° C. or less before the treating step.

[0011] The present disclosure (3) relates to the method for reducing the dielectric constant according to the present disclosure (1) or (2), in which the Low-K film is plasma-treated.

[0012] The present disclosure (4) relates to the method for reducing a dielectric constant according to any one of the present disclosures (1) to (3), wherein the Low-K film has no pores observed under a transmission electron microscope at a magnification of 500,000 times, in bright field mode, and at an accelerating voltage of 200 keV.

[0013] The present disclosure (5) relates to the method for reducing a dielectric constant according to any one of the present disclosures (1) to (4), wherein the Low-K film is a silicon oxycarbonitride film or a silicon oxycarbide film.

[0014] The present disclosure (6) relates to the method for reducing the dielectric constant according to any one of the present disclosures (1) to (5), in which the dielectric constant of the Low-K film is 3.6 or less.

[0015] The present disclosure (7) relates to the method for reducing a dielectric constant according to any one of the present disclosures (1) to (6), wherein a in the general formula (1) represents 2.

[0016] The present disclosure (8) relates to R in the general formula (1). １ are the same or different and represent a hydrogen atom or a methyl group; R ２ are the same or different and represent a hydrogen atom or a methyl group.

[0017] The present disclosure (9) relates to the method for reducing a dielectric constant according to any one of the present disclosures (1) to (8), wherein X in the general formula (1) is a halogen atom.

[0018] The present disclosure (10) relates to the method for reducing a dielectric constant according to any one of the present disclosures (1) to (9), wherein the silylating agent is dimethyldichlorosilane.

[0019] The present disclosure (11) relates to a method for manufacturing a semiconductor device, comprising a step of applying the dielectric constant reduction method according to any one of the present disclosures (1) to (10) to a substrate having a Low-K film, thereby reducing the dielectric constant of the Low-K film.

[0020] According to the present disclosure, even in the case of a Low-K film, which is considered to be a porous film with very small pore diameters, the dielectric constant of the Low-K film can be reduced.

[0021] FIG. 1 is a schematic diagram showing an experimental apparatus for carrying out the method for reducing the dielectric constant used in the examples.

[0022] The present disclosure will be described in detail below, but the following description of the constituent elements is an example of an embodiment of the present disclosure, and the present disclosure is not limited to these specific details. Various modifications can be made within the scope of the gist of the present disclosure.

[0023] In this specification, unless otherwise specified, the expression "X to Y" in the description of a numerical range means at least X and at most Y. For example, "1 to 5% by mass" means "at least 1% by mass and at most 5% by mass."

[0024] [Method for Reducing the Dielectric Constant of a Low-K Film] (Treatment Step) The method for reducing the dielectric constant of a Low-K film according to the present disclosure includes a step of treating the Low-K film at a temperature above 100° C. using a silylating agent, which is a compound represented by the following general formula (1): SiR １ ａ X ４－ａ (1) In the formula, R １ are the same or different and represent a hydrogen atom or an alkyl group; X are the same or different and represent N(R ２ ) ２ group or a halogen atom, R ２ are the same or different and represent a hydrogen atom or an alkyl group; a represents 1 or 2;

[0025] The treatment temperature in the treatment step is preferably 120° C. or higher, more preferably 150° C. or higher, and even more preferably 200° C. or higher. The treatment temperature is usually 400° C. or lower, and preferably 350° C. or lower.

[0026] The pressure conditions in the treating step are not particularly limited, and may be 5 Pa to 100 kPa, 10 Pa to 90 kPa, or 20 Pa to 80 kPa. The treating step may be carried out using a gaseous silylating agent, a silylating agent adsorbed in the pores of the low-K film, or both. However, by using a silylating agent adsorbed in the pores of the low-K film, the treating step can be carried out even under low-pressure conditions. The treating step can be suitably carried out in a chamber in which the temperature and pressure conditions can be adjusted.

[0027] The treatment time in the treatment step is preferably 1 to 600 minutes, more preferably 5 to 300 minutes, even more preferably 10 to 150 minutes, and particularly preferably 20 to 80 minutes.

[0028] In the method for reducing the dielectric constant of the present disclosure, a compound having two or three functional groups, which are amino groups or halogen atoms, represented by the general formula (1) (also referred to as a polyfunctional silylating agent in this specification) is used as a silylating agent. For example, even in the case of a low-k film, which is considered to be a porous film with an extremely small pore size, and which is difficult to reduce the dielectric constant again after being damaged by plasma treatment or the like, the dielectric constant can be reduced by the method for reducing the dielectric constant of the present disclosure. In this specification, the term "amino group" refers to NH ２ group, and NH ２ The H in the group refers to a group substituted with an alkyl group.

[0029] The reason why the dielectric constant can be reduced is not entirely clear, but it is presumed to be due to the following mechanism. By silylating damaged sites (functional groups such as hydroxyl groups) on the outermost surface of the low-k film or on the surfaces of internal pores, the functional groups themselves are reduced and water adsorption to the functional groups is prevented, thereby reducing the dielectric constant of the low-k film. The following, for example, is thought to be the chemical reaction formula when a bifunctional silylating agent is used: Si-OH+SiR １ ２ X ２ →Si—O—SiR １ ２ X+HX 2Si-OH+SiR １ ２ X ２ →Si—O—SiR １ ２ -O-Si+2HX

[0030] Porous low-K films with very small pore diameters have a relatively large surface area within the pores compared to the pore volume. While the number of silylating agents within the pores depends on the pore volume, the number of damaged sites (functional groups such as hydroxyl groups) is thought to depend on the surface area. Therefore, it is necessary to efficiently react with the damaged sites within the pores using a small amount of silylating agent. Therefore, in order to restore more damaged sites with a small amount of silylating agent, it is thought that a monofunctional silylating agent with one functional group is not sufficient, and it was necessary to use a multifunctional silylating agent.

[0031] In particular, it is preferable that a in the general formula (1) is 2. In other words, the polyfunctional silylating agent is preferably a bifunctional silylating agent. It is thought that a trifunctional silylating agent having three functional groups tends to react near the pore entrance, filling the pore entrance and making it difficult to enter the pore, but this is not the case with a bifunctional silylating agent.

[0032] Examples of the bifunctional silylating agent that is a compound represented by the general formula (1) include dimethyldifluorosilane, dimethyldichlorosilane, dimethyldibromosilane, dimethyldiiodosilane, diethyldifluorosilane, diethyldichlorosilane, diethyldibromosilane, diethyldiiodosilane, dipropyldifluorosilane, dipropyldichlorosilane, dipropyldibromosilane, dipropyldiiodosilane, dibutyldifluorosilane, dibutyldichlorosilane, dibutyldibromosilane, dibutyldiiodosilane, methylethyldifluorosilane, methylethyldichlorosilane, methylethyldibromosilane, methylethyldiiodosilane, methylpropyldifluorosilane, methylpropyldichlorosilane, methylpropyldibromosilane, methylpropyldiiodosilane, difluoromethylsilane, dichloromethylsilane, Examples thereof include silane, dibromomethylsilane, diiodomethylsilane, difluoroethylsilane, dichloroethylsilane, dibromoethylsilane, diiodoethylsilane, difluoropropylsilane, dichloropropylsilane, dibromopropylsilane, diiodopropylsilane, difluorobutylsilane, dichlorobutylsilane, dibromobutylsilane, diiodobutylsilane, difluorosilane, dichlorosilane, dibromosilane, diiodosilane, di(dimethylamino)silane, di(diethylamino)silane, di(dipropylamino)silane, di(dibutylamino)silane, di(methylamino)silane, di(ethylamino)silane, di(propylamino)silane, di(butylamino)silane, diaminosilane, dimethyldi(dimethylamino)silane, and bis(diethylamino)dimethylsilane. One or more of these may be used.

[0033] Examples of the trifunctional silylating agent that is a compound represented by the general formula (1) include methyltrifluorosilane, methyltrichlorosilane, methyltribromosilane, methyltriiodosilane, ethyltrifluorosilane, ethyltrichlorosilane, ethyltribromosilane, ethyltriiodosilane, propyltrifluorosilane, propyltrichlorosilane, propyltribromosilane, propyltriiodosilane, butyltrifluorosilane, butyltrichlorosilane, butyltribromosilane, and butyltriiodosilane. Examples thereof include silane, trifluorosilane, trichlorosilane, tribromosilane, triiodosilane, tri(dimethylamino)silane, tri(diethylamino)silane, tri(dipropylamino)silane, tri(dibutylamino)silane, tri(methylamino)silane, tri(ethylamino)silane, tri(propylamino)silane, tri(butylamino)silane, triaminosilane, methyltri(dimethylamino)silane, and methyltri(diethylamino)silane, and one or more of these may be used.

[0034] R in the general formula (1) １ are the same or different and represent a hydrogen atom or an alkyl group, preferably a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, more preferably a hydrogen atom, a methyl group, or an ethyl group, still more preferably a hydrogen atom or a methyl group, and particularly preferably a methyl group.

[0035] In addition, R in the general formula (1) １ When R is an alkyl group having 3 or more carbon atoms, it may be a cyclic alkyl group (cycloalkyl group). １ Examples of the silylating agent in which is a cycloalkyl group include dichlorosilacyclobutane.

[0036] In the general formula (1), X may be the same or different and each represents N(R ２ ) ２ N(R) represents a group or a halogen atom, preferably a halogen atom. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom, preferably a chlorine atom. ２ ) ２ The group is NH２ Motoya NH ２ and an amino group in which H in the group is substituted with an alkyl group. ２ The dimethylamino group is preferred.

[0037] R in the general formula (1) ２ are the same or different and represent a hydrogen atom or an alkyl group, preferably a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, more preferably a hydrogen atom, a methyl group, or an ethyl group, still more preferably a hydrogen atom or a methyl group, and particularly preferably a methyl group.

[0038] The silylating agent preferably has a molecular weight of 500 or less, more preferably 300 or less, even more preferably 200 or less, still more preferably 150 or less, and particularly preferably 140 or less. The lower limit of the molecular weight is preferably 150 or less, more preferably 140 or less, more preferably 150 or less, and most preferably 140 or less. ２ (NH ２ ) ２ ) is 62.

[0039] Most preferably, the silylating agent is dimethyldichlorosilane.

[0040] The Low-K film to be treated in the treatment step may be any film having a dielectric constant lower than that of a silicon dioxide film.

[0041] The Low-K film treated in the treating step is preferably a silicon oxycarbonitride film (SiOCN, where SiOCN does not indicate the stoichiometric ratio of each element but refers to a film containing silicon atoms, oxygen atoms, carbon atoms, and nitrogen atoms) or a silicon oxycarbide film (SiOC, where SiOC does not indicate the stoichiometric ratio of each element but refers to a film containing silicon atoms, oxygen atoms, and carbon atoms), and more preferably a silicon oxycarbonitride film.

[0042] The low-k film treated in the treatment step preferably has a dielectric constant of 2.3 to 3.6, and may also have a dielectric constant of 2.5 to 3.5, 2.7 to 3.4, or 2.9 to 3.3. The dielectric constant is the relative dielectric constant measured by the mercury probe method described in the examples.

[0043] The low-k film treated in the treatment step is preferably one in which no pores are observed under a transmission electron microscope at a magnification of 500,000x, in bright field mode, and at an acceleration voltage of 200 keV. Low-k films, particularly those with a low dielectric constant as described above, are considered to be porous films, and the fact that no pores are observed under the above conditions under a transmission electron microscope suggests that the pore diameters are very small. The method of the present disclosure can be suitably applied to such low-k films.

[0044] The low-k film treated in the treatment step is preferably a damaged low-k film that has been damaged by a treatment such as plasma treatment. The method of the present disclosure can be suitably applied to such a low-k film. In this specification, a damaged low-k film refers to a low-k film whose dielectric constant has increased before and after a treatment such as plasma treatment. The increase in dielectric constant is typically 0.1 or more, and may be 0.2 or more, 0.3 or more, or 0.4 or more. This makes the effect of the dielectric constant reduction method of the present disclosure more pronounced. The upper limit of the increase in dielectric constant is not particularly limited, but is typically 3 or less. Note that various known methods can be used for treatments that cause damage, as long as they increase the dielectric constant of the low-k film before and after the treatment as described above. However, plasma treatment is preferred, and oxygen plasma treatment is more preferred.

[0045] The low-k film treated in the treatment step preferably has, for example, (1) a dielectric constant of 2.8 to 3.5, (2) no pores are observed under a transmission electron microscope at a magnification of 500,000x in bright field mode at an accelerating voltage of 200 keV, and (3) is a damaged low-k film that has been subjected to plasma treatment and whose dielectric constant has increased by 0.1 or more. While it has been difficult to reduce the dielectric constant of such a low-k film again using conventional methods, the dielectric constant can be sufficiently reduced by applying the method of the present disclosure.

[0046] The low-k film treated in the treatment step preferably has an average film thickness of 10 to 10,000 nm. The average film thickness is more preferably 20 to 5,000 nm, even more preferably 30 to 1,000 nm, and particularly preferably 50 to 500 nm. The average film thickness can be measured by the method using an ellipsometer described in the Examples.

[0047] The Low-K film treated in the treating step is preferably formed on a substrate. The substrate is not particularly limited as long as the Low-K film is formed on the substrate, but is preferably a semiconductor device substrate, and examples thereof include a silicon substrate, a compound semiconductor substrate, a quartz substrate, and a glass substrate. In addition to the Low-K film, an insulating film other than the Low-K film, a semiconductor film, a metal wiring film, etc. may be formed on the surface of the substrate. An embodiment in which the Low-K film is exposed is suitable for the dielectric constant reduction method of the present disclosure.

[0048] The method for forming the low-k film is not particularly limited, but examples include CVD. The pore size can be adjusted by adjusting the plasma irradiation conditions when depositing the organosilicon compound gas with plasma, and a stronger film can be formed by reducing the pore size. Such low-k films can also be purchased from manufacturers. Furthermore, since low-k films are typically formed by irradiating them with plasma, functional groups such as hydroxyl groups, i.e., damaged sites, are already present on the outermost surface of the low-k film and on the surfaces of internal pores before they are damaged by treatments such as plasma processing, i.e., at the time the low-k film is formed. Therefore, the method disclosed herein is applicable not only to damaged low-k films, but also to low-k films in general.

[0049] (Supplying Step) The dielectric constant lowering method may include, before the treating step, a step of supplying the gaseous silylating agent to the surface of the low-K film. The temperature in the supplying step is not particularly limited and may be as high as the treatment temperature in the treating step. However, from the viewpoint of enhancing the effects of the present disclosure, it is preferable that the dielectric constant lowering method includes, before the treating step, a step of supplying the gaseous silylating agent to the surface of the low-K film at 100°C or less. The reason for this is thought to be that by performing the supplying step at a low temperature, a larger amount of silylating agent can penetrate into the pores of the low-K film, and then by increasing the temperature to promote silylation, the reaction inside the low-K film can be further promoted.

[0050] From the viewpoint of allowing a larger amount of silylating agent to penetrate, the temperature in the supplying step is preferably 90° C. or lower, 80° C. or lower, 70° C. or lower, 60° C. or lower, 50° C. or lower, or 40° C. or lower. From the viewpoint of preventing condensation (liquefaction) of the silylating agent, the temperature in the supplying step is preferably 10° C. or higher, 20° C. or higher, 30° C. or higher, 40° C. or higher, 50° C. or higher, 60° C. or higher, or 70° C. or higher.

[0051] In the supplying step, the pressure conditions at 100°C or less before the supplying step are preferably 0 Pa or more and less than 5 kPa, more preferably 0 to 1 kPa, and even more preferably 0 to 150 Pa. The temperature and pressure conditions in the supplying step may be appropriately adjusted so that the silylating agent becomes gaseous while maintaining the temperature at 100°C or less. Preferred temperature and pressure conditions vary depending on the type of silylating agent, but are 5 to 100 kPa, 10 to 90 kPa, or 20 to 80 kPa at 100°C or less. The supplying step can be suitably performed in a chamber in which the temperature and pressure conditions can be adjusted.

[0052] (Other Steps) The dielectric constant reduction method of the present disclosure preferably includes a step of subjecting the chamber in which the substrate is placed to a reduced pressure state before the supplying step. Furthermore, the dielectric constant reduction method of the present disclosure more preferably includes a step of exhausting the reacted gas from the chamber and subjecting the chamber to a reduced pressure state after the step of treating the low-k film with the silylating agent of the present disclosure in the chamber. This is because it is possible to remove by-products generated during the treatment of the low-k film. Furthermore, the dielectric constant reduction method of the present disclosure may include a step of introducing an inert gas into the chamber after the step of exhausting the reacted gas and subjecting the chamber to a reduced pressure state. The reduced pressure state refers to a state in which the pressure in the chamber is lower than that during the treatment of the low-k film, and is preferably, for example, 150 Pa or less.

[0053] [Dielectric Constant Reducing Device] The dielectric constant reducing method of the present disclosure can be realized, for example, by using the following dielectric constant reducing device. The dielectric constant reducing device of the present disclosure includes a chamber, a heating means for heating the inside of the chamber, and a silylation agent gas supply unit for supplying a gaseous silylating agent into the chamber. The dielectric constant reducing device of the present disclosure may further include a pressure reducing means for reducing the pressure inside the chamber and an inert gas supply unit for supplying an inert gas into the chamber. The pressure reducing means may also serve as a gas exhaust means.

[0054] Fig. 1 is a schematic diagram illustrating an example of a dielectric constant reduction device according to an embodiment of the present disclosure. The dielectric constant reduction device 100 shown in Fig. 1 includes a chamber 3 on whose inner bottom surface a substrate 7 is placed, a silylation agent supply unit 1 connected to the chamber 3 via a pipe and supplying a gaseous silylating agent, a pressure reduction unit (vacuum pump) VAC connected to the chamber 3 via a pipe and applying a reduced pressure to the chamber 3, and an inert gas supply unit 11 connected to the chamber 3 via a pipe and supplying an inert gas. Note that the dielectric constant reduction device 100 does not necessarily have to include the inert gas supply unit 11.

[0055] Furthermore, the dielectric constant reducing device 100 may include a control unit (not shown). This control unit is, for example, a computer, and includes a program, a memory, and a CPU. The program incorporates steps for performing a series of operations in the dielectric constant reducing method, and performs the following operations in accordance with the program: adjusting the temperature of the substrate 7, opening and closing the valves of each supply unit, adjusting the flow rate of each gas, adjusting the pressure inside the chamber 3, etc. This program is stored in a computer storage medium, such as a compact disc, a hard disk, a magneto-optical disc, or a memory card, and is installed in the control unit.

[0056] A substrate 7 is placed on the bottom of the chamber 3. The substrate 7 may be placed on a stage (a mounting table for placing a substrate). A hot plate 9 for heating the bottom of the chamber 3 is installed below the chamber 3 in contact with the bottom of the chamber 3. Furthermore, a pipe serving as a gas inlet and a pipe serving as a gas outlet are connected to the top of the chamber 3, and the pressure inside the chamber 3 can be adjusted. This allows the dielectric constant reduction method of the present disclosure to be suitably carried out using the procedure according to the present disclosure.

[0057] The chamber 3 is not particularly limited as long as it is resistant to the gases used and can be depressurized to a predetermined pressure, but a general SUS chamber used in semiconductor etching equipment is usually used. Furthermore, the piping serving as the gas inlet and the piping serving as the gas outlet are also not particularly limited as long as they are resistant to the gases used, and general piping can be used.

[0058] A heating means (for example, a ribbon heater 5 or the like) for heating at least a part of the side wall and bottom of the chamber 3 may be further provided outside the chamber 3 .

[0059] As described above, the chamber 3 is provided with a pressure reducing means for reducing the pressure inside the chamber. The vacuum pump VAC, which serves as the pressure reducing means, exhausts gas before and after the reaction from the chamber 3 through piping. For example, the gas after the reaction can be recovered by providing a liquid nitrogen trap (not shown) between the piping and the vacuum pump VAC. The pressure inside the chamber can also be adjusted by providing a valve in this piping. In addition, in FIG. 1, PI is a pressure gauge, and the control unit can control each flow rate adjusting means and each valve based on the indicated value.

[0060] After the process of discharging the gas after the reaction and placing the chamber under reduced pressure, the inert gas supply unit 11 supplies the inert gas into the chamber 3 through a pipe, adjusting the supply amount using a valve or the like as necessary.

[0061] Examples of inert gases include Ar and N ２ , He, Ne, Kr, etc. These may be used alone or in combination of two or more. Among them, Ar, N are preferred because they are stable and inexpensive. ２ is preferred.

[0062] The dielectric constant reduction apparatus 100 may also be used as an etching apparatus or a protective layer forming apparatus in the manufacture of semiconductor devices, and may further include, for example, an etching gas supply unit, an electrode, a high-frequency power supply, and the like for use in etching.

[0063] The dielectric constant reduction method will be specifically described using the dielectric constant reduction device 100 as an example. [Dielectric constant reduction method using the dielectric constant reduction device] In the dielectric constant reduction method of the present disclosure, the dielectric constant of a low-k film is reduced by treating the low-k film with the silylation agent of the present disclosure.

[0064] In the dielectric constant reduction method of the present disclosure, first, a substrate 7 on which a low-k film has been formed is placed on the bottom of the chamber 3. Next, the inside of the chamber 3 and the piping are evacuated to a predetermined pressure by the vacuum pump VAC. Once the inside of the chamber has stabilized, a gaseous silylating agent is supplied from the silylation agent supply unit 1 to the piping at 100°C or below.

[0065] A gaseous silylating agent is introduced into the chamber 3, thereby controlling the pressure inside the chamber 3 to a predetermined level. Thereafter, the chamber is heated to above 100°C using a heating means (ribbon heater 5, hot plate 9) for a predetermined period of time, and the silylating agent is used to silylate functional groups, such as hydroxyl groups, contained in the low-k film, thereby treating the low-k film and thereby reducing the dielectric constant of the low-k film. The flow rate of the gaseous silylating agent can be appropriately set based on the volume and pressure of the chamber. After introducing the gaseous silylating agent into the chamber 3, and before heating the chamber to above 100°C, the gaseous silylating agent inside the chamber may be pushed out by introducing an inert gas from the inert gas supply unit 11 into the chamber, or the vacuum pump VAC may be started to exhaust the inert gas and place the chamber under reduced pressure.

[0066] After the processing step is completed, the vacuum pump VAC is started to discharge the gas after the reaction, and then an inert gas is introduced from the inert gas supply unit 11 and released. As described above, the dielectric constant of the low-k film can be reduced by the dielectric constant reduction method of the present disclosure using the dielectric constant reduction device.

[0067] [Method for Manufacturing a Semiconductor Device] The method for manufacturing a semiconductor device according to the present disclosure is characterized by including the dielectric constant reduction method according to the present disclosure described above. The dielectric constant reduction method according to the present disclosure described above can be applied to a substrate having a low-k film, such as a damaged low-k film, in the manufacturing process of a semiconductor device, and can be used as a method for reducing the dielectric constant of the low-k film. By using the dielectric constant reduction method according to the present disclosure to reduce the dielectric constant of the low-k film on the substrate, high-performance semiconductor devices can be easily manufactured.

[0068] The method for manufacturing a semiconductor device according to the present disclosure preferably further includes a step of depositing a Low-K film using a CVD method or the like, a step of patterning the deposited Low-K film using a photoresist process or the like, and a step of removing the photoresist and mask layer on the Low-K film using dry plasma, etc. The method for manufacturing a semiconductor device according to the present disclosure also includes other steps that are conventionally known in the art for semiconductor devices, such as an etching step and a protective layer formation step.

[0069] The present disclosure will be described in detail below using examples, but the present disclosure is not limited to these examples.

[0070] (Film Thickness Measurement) The film thickness of the substrate to be treated was measured using a spectroscopic ellipsometer (manufactured by Nippon Semilab Co., Ltd., product name: SE-2000).

[0071] (Measurement of dielectric constant of low-k film) The dielectric constant of the low-k film before and after plasma treatment was measured by the following method. Before measurement, the film was dried under reduced pressure in an oven at 100°C. Analysis method: mercury probe method. Analysis equipment: automatic mercury probe CV measurement equipment (SSM 495) manufactured by SSM. Mercury contact area (electrode area): 0.7 mm ２ Measurement frequency (CV measurement): 100 kHz. The relative dielectric constant of the low-k film was calculated from the CV curve and the film thickness evaluated separately by ellipsometry.

[0072] (XPS Measurement) The surface composition of the low-K film was measured by the following method. Analysis method: X-ray photoelectron spectroscopy (XPS) Analysis equipment: XPS equipment (PHI 5000 Versa Probe II) manufactured by ULVAC-PHI, Inc. X-ray source used: Al (Kα) ray (1.5 keV) Photoelectron take-off angle: 45° X-ray beam diameter: 100 μm Neutralization gun conditions: 1 V, 20 μA

[0073] [Examples and Comparative Examples] Samples: A silicon oxycarbonitride (SiOCN) film with a thickness of approximately 170 nm formed on a silicon wafer was used as the low-k film. Pore size was measured using a transmission electron microscope (TEM) at a magnification of 500,000x, in bright field mode, and at an accelerating voltage of 200 keV. No pores were observed. The dielectric constant of the low-k film before plasma treatment was 2.72.

[0074] Furthermore, the composition of the low-K film was evaluated by XPS, and Si, O, C, and N were detected. ２The dielectric constant of the low-k film was 2.72, while that of SiN and SiC were 3.9, 7, and approximately 10, respectively. Therefore, it is presumed that the low-k film is porous, and that its porosity contributes to its low dielectric constant. Furthermore, it is presumed that the reason that no pores were observed with TEM is that the arrangement of pores in the porous film was not regular like that of a crystalline structure, and that the pore diameter was very small.

[0075] The silicon wafer on which the low-K film was formed was cut into a piece of 5 cm x 5 cm. ２ The surface layer was removed by about 100 nm by plasma treatment. The dielectric constant after that was 3.16. This was used as a test piece (sample) of a low-k film that had been damaged by plasma.

[0076] Experimental Procedure: Figure 1 is a schematic diagram showing the experimental apparatus used to implement the dielectric constant reduction method used in the examples. A test specimen was placed at the bottom of chamber 3, a stainless steel container (internal volume approximately 1 L), and the lid was placed on the chamber. The chamber 3 was depressurized to 1 Torr (133 Pa) or less using a vacuum pump (VAC), an oil-sealed rotary pump. A treatment agent (silylating agent) was introduced and heat treatment was performed. Specifically, the silylating agent was introduced at room temperature (25°C) up to its vapor pressure, and the stainless steel container was heated to 230°C from the outside. After holding for 20 minutes, the pressure was reduced using the oil-sealed rotary pump. Next, nitrogen gas was introduced from the inert gas supply unit 11 to atmospheric pressure, and the chamber was opened, and the sample was removed.

[0077] The experimental procedure was carried out using the silylation agents listed in Table 1 below. The dielectric constant of the low-k film after silylation treatment was measured, and the dielectric constant of the damaged low-k film before silylation treatment was subtracted from the measured dielectric constant to determine the amount of dielectric constant recovery (decrease) due to silylation treatment. The results are shown in Table 1 below.

[0078] In Table 1, "number of functional groups" indicates the number of non-Si-C bonds around the Si atom of the silylating agent, and is the number of sites that can react with SiOH on the damaged Low-K film surface. However, Si-OR had low reactivity. "Reactivity" indicates whether or not there is silylation reactivity to the extent that the contact angle increases when the silylating agent is applied alone to the Low-K film surface. In Table 1 below, "yes" indicates that the contact angle on the Low-K film surface (contact angle of 5 degrees or less) increased to about 50-70 degrees after contact.

[0079] In Table 1, DMDCS represents dimethyldichlorosilane. DMADMS represents bis(dimethylamino)dimethylsilane. HMDS represents hexamethyldisilazane. TMCS represents trimethylchlorosilane. MTCS represents methyltrichlorosilane. MTMS represents methoxytrimethylsilane. DMDMS represents dimethoxydimethylsilane. MDCS represents dichloromethylsilane.

[0080]

[0081] The results shown in Table 1 indicate that silylating agents containing amino groups or halogen atoms are reactive with the outermost surface of low-k films. In particular, multifunctional silylating agents containing two or more amino groups or halogen atoms are capable of restoring the dielectric constant of damaged low-k films. It is believed that such multifunctional silylating agents effectively silylate damaged sites within pores in damaged low-k films.

[0082] Next, in Example 1, the experimental procedure was changed as shown in Table 2 below, and the results are shown in Table 2 below.

[0083]

[0084] Table 2 shows that the dielectric constant recovery rate is greater when the silylating agent is introduced at a low temperature and then heated after introduction. In Example 5, when the gaseous silylating agent was introduced into the chamber at room temperature and held there for 2 minutes, the silylating agent was adsorbed into the pores of the low-K film, and it is believed that the use of this silylating agent enables the silylation reaction to occur even under low-pressure conditions.

[0085] This application claims priority under the Paris Convention or the laws of countries that have adopted it, based on Japanese Patent Application No. 2024-135718, filed on August 15, 2024. The contents of that application are incorporated herein by reference in their entirety.

[0086] REFERENCE SIGNS LIST 1 silylation agent supply unit 3 chamber 5 ribbon heater 7 substrate 9 hot plate 11 inert gas supply unit 100 dielectric constant reduction device PI pressure gauge VAC vacuum pump

Claims

1. A method for reducing the dielectric constant of a low-k film, comprising the step of treating the low-k film at a temperature above 100°C with a silylating agent, which is a compound represented by the following general formula (1): SiR １ ａ X ４－ａ (1) In the formula, R １ are the same or different and represent a hydrogen atom or an alkyl group; X are the same or different and represent N(R ２ ) ２ group or a halogen atom, R ２ are the same or different and represent a hydrogen atom or an alkyl group; a represents 1 or 2; 2. The method for reducing a dielectric constant according to claim 1, further comprising the step of supplying the silylating agent in a gaseous state to the surface of the low-K film at 100°C or less before the treating step.

3. The method for reducing the dielectric constant according to claim 1 or 2, wherein the low-k film is plasma-treated.

4. The method for reducing the dielectric constant according to any one of claims 1 to 3, wherein no holes are observed in the Low-K film when examined with a transmission electron microscope at a magnification of 500,000x in bright field mode at an accelerating voltage of 200 keV.

5. The method for reducing a dielectric constant according to any one of claims 1 to 4, wherein the Low-K film is a silicon oxycarbonitride film or a silicon oxycarbide film.

6. The method for reducing the dielectric constant according to any one of claims 1 to 5, wherein the dielectric constant of the low-k film is 3.6 or less.

7. The method for reducing a dielectric constant according to any one of claims 1 to 6, wherein a in the general formula (1) represents 2.

8. R in the general formula (1) １ are the same or different and represent a hydrogen atom or a methyl group; R ２ and are the same or different and represent a hydrogen atom or a methyl group.

9. The method for reducing a dielectric constant according to any one of claims 1 to 8, wherein X in the general formula (1) is a halogen atom.

10. The method for reducing a dielectric constant according to any one of claims 1 to 9, wherein the silylating agent is dimethyldichlorosilane.

11. A method for manufacturing a semiconductor device, comprising the step of applying the dielectric constant reduction method according to any one of claims 1 to 10 to a substrate having a Low-K film, thereby reducing the dielectric constant of the Low-K film.

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