JP3497848B2 - Method and apparatus for forming antireflection film and antireflection film - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for forming an antireflection film and an antireflection film, and more specifically, a method for forming an antireflection film having a desired refractive index and extinction coefficient on a substrate, and The present invention relates to an apparatus therefor and an antireflection film effectively formed by such a method for forming an antireflection film.

[0002]

2. Description of the Related Art In recent years, the miniaturization of semiconductor devices has been accelerated, and the line width of metal wiring and the like tends to be extremely thin. Accordingly, in photolithography in the manufacture of semiconductor devices, an antireflection film (ARC; An
ti-Reflective Coating) is often used. The antireflection film has an antireflection function mainly by canceling the phase of the light reflected from the upper surface and the light reflected from the lower surface. However, the exposure wavelength used in lithography, the thickness of the antireflection film, and the optical Depending on the relationship with the characteristics,
It may be difficult to completely eliminate the reflected light due to the phase difference, and in order to compensate for it, the antireflection film is required to have some light absorption characteristics.

This absorption characteristic exhibited by the antireflection film is generally represented by an index called an extinction coefficient. In order to ensure the required performance in lithography, the film thickness of the antireflection film, the refractive index, and the above extinction coefficient are used. It is necessary to manage and control the three physical quantities. As such an antireflection film, for example, an antireflection insulating film (DARC; Dielectric Anti-Reflective Coating) such as a silicon oxynitride film (SiON film).
Etc. As a method for forming this DARC, for example, a film forming gas containing a silane-based gas as a silicon (Si) source and a dinitrogen monoxide (N ₂ O) gas as a nitrogen and oxygen source is used as a Si wafer or the like. Examples of the method include a thermal CVD method of heating a Si wafer while supplying the Si wafer on the substrate, a plasma CVD method, and the like.

[0004]

By the way, the above-mentioned optical characteristics (refractive index and extinction coefficient) required for an antireflection film in lithography are usually the underlayer of the antireflection film (for example, a metal film such as aluminum, It is determined so as to match the optical characteristics of the polysilicon film). On the other hand, the conventional DARC including a SiON film has a constant refractive index and extinction coefficient even if various film forming conditions such as a film forming gas mixture ratio, a film forming pressure, and a film forming temperature are changed. Tends to show a correlation of

That is, in the conventional DARC, it is extremely difficult to change (control) the refractive index and the extinction coefficient independently. Therefore, it is not possible to form an antireflection film that satisfies both the desired refractive index and extinction coefficient required by lithography, and in some cases it may be difficult to obtain the desired line width in patterning the resist film. .

Therefore, the present invention has been made in view of such circumstances, and provides a method for forming an antireflection film and an apparatus therefor capable of realizing an antireflection film exhibiting a desired refractive index and extinction coefficient. The purpose is to provide. Also,
An object of the present invention is to provide an antireflection film that exhibits a desired refractive index and extinction coefficient.

[0007]

In order to solve the above problems, the method for forming an antireflection film according to the present invention comprises:
A method for forming an antireflection film exhibiting a predetermined refractive index and extinction coefficient, which comprises supplying a film forming raw material gas onto a substrate,
A film forming step of forming a film to be processed on the substrate, a reforming gas containing oxygen atoms in the molecule is supplied to the substrate on which the film to be processed is formed, and plasma is generated around the substrate. In the film formation process, which is obtained before the film formation process, the modification process of forming the film to be processed into an antireflection film having a different refractive index and extinction coefficient from the film to be processed. Based on the correlation between the refractive index and extinction coefficient of the film to be processed obtained when the film forming conditions are changed, and the predetermined refractive index and extinction coefficient required for the antireflection film, the film forming step And a condition setting step for determining the plasma processing conditions in the reforming step. When forming the film to be processed in the film forming step, plasma may be formed as in the plasma CVD method.

According to the method of forming an antireflection film having such a structure, first, a film forming step is carried out, for example, CVD.
A film to be processed is formed by the method. The film to be processed corresponds to an antireflection film formed by a conventional film forming method, and the film to be processed obtained when the film forming conditions are changed in the film forming step has a certain correlation. It has a refractive index and an extinction coefficient.

For example, FIG. 8 is a graph showing measured data of the refractive index and extinction coefficient of the films to be treated (conventional antireflection films) obtained in Comparative Examples 1 to 13 by the conventional film forming method described later. A line Lk in the figure shows a fitting straight line obtained by linearly least-squares approximation of these data. The constant correlation is expressed by a correlation equation specific to each wavelength of probe light for measuring the refractive index. Although the detailed mechanism by which such a relationship is established is still unknown, it is presumed that the composition of the antireflection film may be governed to some extent. However, the operation is not limited to this.

Next, a reforming step is carried out, a reforming gas is supplied onto the substrate on which the film to be treated is formed, and plasma is formed around the substrate. For example, electric discharge can be used to form plasma, whereby the reforming gas is activated, dissociated, or ionized to generate active species such as ions and radicals derived from the reforming gas in the plasma. Is generated,
The treated film on the substrate is exposed to these active species. Among the active species, those containing oxygen atoms oxidize the film to be treated as an oxidizing factor to obtain an antireflection film in which the modified or oxidized state has progressed to the oxidized state.

The inventor of the present invention formed a SiON film as a film to be processed in the film forming step and further oxidized and modified the SiON film as an antireflection film in the modification step to obtain the refractive index and the extinction coefficient. As a result of the measurement, the refractive index and the extinction coefficient of the antireflection film have a certain correlation with the refractive index and the extinction coefficient of the processed film corresponding to the conventional antireflection film (see FIG. 8).
It was confirmed that it was significantly different from the line Lk (see the inside). This is because at least a part of the film to be processed is oxidized and modified by plasma processing, and the composition, density, and
It is considered that the crystalline / amorphous state is different from that of the film to be processed.

Here, in the present invention, a part or all of the condition setting step is carried out before the film forming step is carried out to determine the film forming condition in the film forming step, and the modifying step is carried out. Before, the other part of the condition setting step is performed to determine the plasma processing conditions. That is, based on the constant correlation between the refractive index and the extinction coefficient of the film to be processed, and the predetermined refractive index and extinction coefficient required for the finally formed antireflection film, Film forming conditions and plasma processing conditions are determined.

Specifically, the film forming conditions of the film to be processed, for example, the supply flow rate of the film forming source gas, the total pressure around the substrate,
When the gas partial pressure, the substrate temperature, other geometrical parameters, etc. are changed, the values of the refractive index and the extinction coefficient of the film to be processed can be varied within the range satisfying the above-mentioned certain correlation.
Further, when the plasma processing conditions for the film to be processed, for example, the high frequency output when high frequency power is used to generate glow discharge, the frequency, the plasma formation time, etc. are changed, the film to be processed is originally processed. The refractive index that develops and their rate of change (rate of change) from the extinction coefficient can vary.

Therefore, if the relationship between the refractive index and the extinction coefficient of the film to be processed and the variation thereof is acquired in advance under known film forming conditions and plasma processing conditions, any desired antireflection film can be obtained. The film forming conditions and the plasma processing conditions to be applied to the film forming process and the modifying process to obtain the refractive index and the extinction coefficient can be reliably and easily set.

In the condition setting step, the refractive index required for the antireflection film is obtained by performing the modifying step on the film to be processed obtained under arbitrary film forming conditions in the film forming step. Film formation for forming a film to be processed for obtaining an antireflection film based on the difference between the extinction coefficient of a virtual film having a substantially equal refractive index and the extinction coefficient required for the antireflection film It is preferable to determine the conditions.

According to the knowledge of the inventor of the present invention, when the film to be processed having the refractive index and the extinction coefficient on the line Lk shown in FIG. The extinction coefficient tends to decrease with respect to the film to be treated. At this time, when the same plasma processing condition is applied to the films to be processed having different combinations of the refractive index and the extinction coefficient on the line Lk, the refractive index and the extinction coefficient which are obtained by the various antireflection films are obtained by the line Lk. Does not show a parallel correlation with
It was confirmed that, depending on the plasma treatment conditions, the extinction coefficient is different while the refractive index is substantially constant.

Therefore, first, plasma is used to obtain an antireflection film having a refractive index substantially the same as the required refractive index of the antireflection film, with the film to be processed obtained under certain arbitrary film forming conditions as a standard or reference. It is assumed that the standard film to be processed is subjected to a modification process under the processing conditions to obtain the above'virtual film '. As described above, the plasma processing conditions have various relationships between various known film forming conditions and plasma processing conditions, and various refractive indices and extinction coefficients of the film to be processed and the antireflection film obtained by them. It can be easily set by acquiring it. Then, if the difference between the virtual film extinction coefficient and the required anti-reflection film extinction coefficient is obtained, the required standard (arbitrary) film formation conditions can be changed. It is possible to determine whether a film to be processed can be formed to obtain the antireflection film.

In other words, the method for forming an antireflection film according to the present invention comprises a film forming step of forming a film to be processed on the substrate by supplying a film forming raw material gas onto the substrate. By supplying a modifying gas containing oxygen atoms in the molecule to the treated substrate and performing plasma treatment, the film to be treated is changed into an antireflection film having a refractive index and an extinction coefficient different from those of the film to be treated. And a film forming condition of the film to be processed in the film forming process so that the extinction coefficient of the antireflection film changes while maintaining the refractive index of the antireflection film substantially constant. And adjusting the plasma processing conditions in the reforming step.

Alternatively, a film forming step of supplying a film forming raw material gas onto a substrate and forming a film to be processed having a constant correlation between a refractive index and an extinction coefficient on the substrate, and a film to be processed. While supplying a reforming gas containing oxygen atoms in the molecule on the substrate on which the plasma is formed, plasma is formed around the substrate,
A modification step of modifying the film to be processed into an antireflection film having a refractive index and an extinction coefficient deviating from a certain correlation is provided, and a certain correlation (for example, line L shown in FIG. 8).
k)) and the refractive index and extinction coefficient required for the antireflection film, the film forming conditions of the film to be processed in the film forming process, and the plasma in the modifying process. This method is characterized by determining processing conditions.

More specifically, when a plurality of kinds of gases are used as the film forming source gas in the film forming step, the supply flow rate ratio of the plurality of kinds of gases is determined as the film forming condition in the film forming step, It is preferable to determine the plasma formation time as the plasma processing condition in the reforming process.

Among the film forming conditions described above, when the film forming raw material gas is composed of a mixed gas of a plurality of kinds of gases, when the supply flow rate ratio of each gas (mixing ratio, each gas partial pressure) is changed, The refractive index and extinction coefficient sharply increase and decrease. It is presumed that this is because the composition of the film to be formed changes to such an extent that it causes a significant change in the refractive index. For example, when the film forming raw material gas is composed of SiH ₄ gas and N ₂ O gas when forming the SiON film, the supply flow rate ratio of both gases can be changed by changing the SiH ₄ gas flow rate. You can

Further, among the plasma processing conditions, it is easy to significantly control the difference between the refractive index and extinction coefficient of the film to be processed and those of the obtained antireflection film by changing the plasma formation time. It is in. This is because the time during which the film to be processed is exposed to the active species varies depending on the plasma formation time, and thus the thickness and volume of the film to be processed to be oxidized / modified changes to change the refractive index and quenching of the entire antireflection film. It is considered that the extinction coefficient fluctuates moderately and significantly.

Further, when plasma is formed by applying high frequency power to the electrodes, the refractive index and extinction coefficient of the antireflection film can be adjusted by appropriately selecting the frequency of the high frequency power. . The frequency is not particularly limited, but preferably 1 to 50 MHz. Furthermore, if the output of the high frequency power is constant, the higher the frequency is, the higher the active species density is, and conversely, the active species energy tends to be smaller. When the density or energy of the active species changes in this way, it is assumed that the degree of oxidation / modification of the film to be processed, for example, the depth (film thickness) of oxidation / modification may change. It is estimated that the refractive index and the extinction coefficient of the obtained antireflection film fluctuate appropriately and significantly.

Further, in the film forming step, a silane-based gas as a film forming source gas, a gas containing nitrogen atoms in the molecule, and a gas containing oxygen atoms in the molecule are supplied onto the substrate to form an antireflection film. As a silicon oxynitride film (SiON film)
In the reforming step, it is useful to supply a nitric oxide-based gas as a reforming gas onto the substrate.

Here, as the silane-based gas, unsubstituted monosilane or higher order silane, or monosilane or higher order silane in which at least one hydrogen atom in the molecule is replaced with an organic functional group or an organic non-functional group ( Organosilane gas), and the substituent is not particularly limited,
Examples thereof include an alkyl group, an alkynyl group, an alkenyl group, an alkoxyl group (alkoxy group), and a group having an aromatic ring (aryl group, aralkyl group, alkylaryl group, etc.) and the like.

When forming a film containing no oxygen atoms as a film to be treated, a silane-based gas containing no oxygen atoms in the molecule is useful, and monosilane gas is used from the viewpoint of industrial applicability and handleability. And disilane gas are particularly preferable. On the other hand, when an oxide film is obtained as the film to be processed, an organic silane-based gas having an oxygen-containing group such as an alkoxyl group, that is, an organic oxysilane-based gas may be used. A particularly useful organooxysilane is TE
Ethoxysilanes such as OS (tetraethyl orthosilicate) and ethyltriethoxysilane can be mentioned. In addition, these gases can be used alone or in combination of two or more as a silane-based gas.

Examples of the gas containing nitrogen atoms in the molecule include nitric oxide gas, nitrogen (N ₂ ) gas, ammonia (NH ₃ ) gas, etc., which will be described later. As the gas containing oxygen atoms in the molecule, Is also a nitric oxide-based gas, oxygen (O
₂ ) Gas and ozone ( ₃ ) gas.

Further, as the nitric oxide type gas, dinitrogen oxide (N ₂ O), nitric oxide (NO), dinitrogen trioxide (N ₂ O ₃ ), nitrogen dioxide (N ₂ O), dipentapentoxide. Nitrogen (N ₂
O ₅ ), and a gas containing at least one of nitric oxide (NO ₃ ), industrial utility,
From the viewpoint of excellent stability and handleability, N ₂ O gas is preferably used. When a nitric oxide-based gas is used as the reforming gas in this way, when a silane-based gas that does not contain oxygen atoms in its molecule is used as the film-forming raw material gas, the gas that remains around the substrate after the film-forming process is completed. Since the reaction between the film forming material gas and the reforming gas is unlikely to occur, there is an advantage that the reforming step can be carried out immediately after the film forming step.

The antireflection film forming apparatus according to the present invention is for effectively carrying out the method for forming an antireflection film of the present invention, and exhibits a predetermined refractive index and extinction coefficient on a substrate. A device in which an antireflection film for
(A) a film-forming chamber that accommodates a substrate, and a film-forming source gas supply unit that is connected to the film-forming chamber and supplies a film-forming source gas into the film-forming chamber. A film forming part on which a film to be processed is formed on a substrate, (B) a reforming chamber containing the substrate on which the film to be processed is formed, and an oxygen atom in a molecule connected to the reforming chamber. A reforming gas supply unit that supplies the reforming gas containing the reforming gas into the reforming chamber, an electrode installed in the reforming chamber, and a high-frequency power source connected to the electrode. By applying high-frequency power output from the electrodes to the electrodes, plasma is formed in the reforming chamber, and the film to be processed is changed to an antireflection film having a refractive index and extinction coefficient different from those of the film to be processed. Change the film forming conditions for the film to be processed in the reforming part to be improved and (C) film forming part Based on the correlation between the refractive index and the extinction coefficient of the film to be processed obtained when the film is formed, and the refractive index and the extinction coefficient of the antireflection film, the film forming conditions in the film forming section and the modifying section And a control unit that adjusts the plasma processing condition.

Further, the film-forming source gas supply unit supplies a silane-based gas as a film-forming gas, a gas containing a nitrogen atom in the molecule, and a gas containing an oxygen atom in the molecule into the film-forming chamber. Therefore, it is useful that the reforming gas supply unit supplies the nitric oxide-based gas as the reforming gas into the reforming chamber.

The antireflection film according to the present invention is effectively formed by the method for forming an antireflection film according to the present invention, and has the following formula (1); k> 1.690 × n-3. 046 (1), a silicon oxynitride film (SiON) satisfying the relationship expressed by
Membrane). In the formula, k has a film thickness of 30
shows the extinction coefficient of the antireflection film in nm, and n shows the refractive index of the antireflection film in the thickness of 30 nm.
The refractive index n and the extinction coefficient k used here are n & k Analyzer 1200 and 1500 manufactured by n & k, and the probe light wavelength is 248 nm (Deep-UV ray).
Indicates the value measured when. In addition, when another measuring device is used, a method of normalizing to the measured value of the n & k Analyzer can be adopted. Examples of other measuring instruments include UV1280SE manufactured by KLA Tencor.

[0032]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below. The same elements will be denoted by the same reference symbols, without redundant description. Further, the positional relationship such as up, down, left and right is based on the positional relationship shown in the drawings unless otherwise specified. The dimensional ratios in the drawings are not limited to the illustrated ratios.

FIG. 1 is a horizontal sectional view schematically showing a preferred embodiment of an apparatus for forming an antireflection film according to the present invention. The processing apparatus 1 has three side walls of a transfer chamber 2 having a main frame having a substantially rectangular cross section.
A twin chamber 3 in which two Si wafers W (substrates) are accommodated at the same time is combined, and a load lock chamber 6 in which load lock chambers 6a and 6b are provided is connected to the remaining side wall. Transfer chamber 2
A wafer transfer robot 23 having two extendable and retractable arm portions 21 is installed therein, and the Si wafer W is placed and held at the tip end portions of these arm portions 21. Further, each twin chamber 3 has two susceptors 5 on which the Si wafer W is placed.

FIG. 2 is a sectional view (partial configuration diagram) showing an essential part of the processing apparatus 1 shown in FIG. 1, and the portion of the sectional view shows a section taken along the line II-II in FIG. In the figure, the twin chamber 3 is formed by arranging two chambers 4 (which also serve as a film forming chamber and a reforming chamber) side by side in a chamber housing 11. Each chamber 4 has the above-mentioned susceptor 5 on which the Si wafer W is placed, and above each susceptor 5, a shower head portion 40 having a hollow disk shape is provided.

The susceptor 5 is airtightly provided in the chamber 4 by an O-ring, a metal seal, etc.
It is provided so as to be vertically movable by a movable mechanism (not shown). With this movable mechanism, the distance between the Si wafer W and the shower head portion 40 is adjusted. Further, the susceptor 5 is internally provided with a heater 51, which heats the Si wafer W to a desired predetermined temperature.
Furthermore, the susceptor 5 is grounded to a predetermined potential.

On the other hand, the shower head portion 40 includes a body portion 41 having a base plate as an upper wall, which is provided in common to the two chambers 4 and has a gas supply port 9 provided for each chamber 4, and a plurality of shower head portions 40. Blocker plate 43 and face plate 4 in the form of a perforated plate having through holes
5 and. The body portion 41 has a concave portion that forms a substantially cylindrical internal space that communicates with the gas supply port 9, and the peripheral edge portion of the face plate 45 is coupled to the inner peripheral portion on the lower end side of the concave portion. A blocker plate 43 is installed above the face plate 45 substantially in parallel with the face plate 45. The blocker plate 43 is provided between the upper wall of the body 41 and the blocker plate 43, and between the blocker plate 43 and the face plate 45. A space communicating with the gas supply port 9 is defined therebetween.

Further, a high frequency power source R grounded to the same potential as the susceptor 5 is connected to the shower head portion 40 of each chamber 4 via an impedance matching device 60 for matching impedance. The high frequency power supply R may be a fixed frequency type or a frequency variable type equipped with a frequency inverter, for example.

Furthermore, an opening 7 is provided in the lower portion of each chamber 4, and the inside of each chamber 4 is depressurized and the gas is supplied from a gas supply unit 30 to be described later according to the supply flow rate of each gas. An exhaust system 70 having a vacuum pump capable of maintaining the pressure inside each chamber 4 at a constant pressure is connected via a valve system V.

The valve system includes, for example, a two-blade type turbo throttle valve arranged on the upstream side (twin chamber 3 side) and an isolation valve arranged on the downstream side (exhaust system 70 side). It can be configured, and a gate valve may be added. The type of vacuum pump used for the exhaust system 70 is not particularly limited, and examples thereof include a turbo molecular pump with a dry pump and the like.

In the twin chamber 3, a monosilane (SiH ₄ ) gas supply source 31 (film forming raw material gas supply section), a dinitrogen oxide (N ₂ O) gas supply source 32 (film forming raw material gas supply section) And a helium (He) gas supply source 33, and a nitrogen (N ₂ ) gas supply source 34 are also connected. These gas supply sources 31 to 34 are MFCs (mass flow rate controllers) 31a and 32 for controlling the supply flow rates of the respective gases.
It is connected to the gas supply port 9 of each shower head portion 40 via a pipe 10 provided with a, 33a and 34a.

With these, S as a raw material gas for film formation
iH ₄ gas and N ₂ O gas, the N ₂ O gas as a gas reforming, He gas as a carrier gas or diluent gas, as well as the N ₂ gas as a purge gas as required, a shower head of each chamber 4 The blocker plate 43 and the face plate 45 are introduced into the section 40.
Is supplied to each chamber 4 via. In this way, the film forming unit is constituted by each chamber 4 and the gas supply unit 30. Further, the reforming unit is configured by the chambers 4, the gas supply unit 30, the high frequency power sources R, and the impedance matching units 60.

The pipe 10 is connected to a cleaning system 8 which employs remote plasma processing. The cleaning system 8 includes a reactor cavity 81 arranged on the pipe 10 side and an MFC 8
It has a supply source 82 of a gas containing fluorine atoms, such as NF ₃ gas, connected through 2a. The reactor cavity 81 is equipped with a microwave generator (not shown) for generating plasma,
The NF ₃ gas as the cleaning gas supplied from the gas supply source 82 is dissociated to generate active species, and mainly neutral active species are supplied into the chamber 4 depending on the conditions.

Further, the processing apparatus 1 includes MFCs 31a to 3a.
4a, each impedance matching device 60, and the control part 80 connected to each high frequency power supply R. The control unit 80 controls the film thickness of the antireflection film formed on the Si wafer W,
In addition, a recipe including film forming conditions and modifying conditions determined according to optical characteristics such as a refractive index and an extinction coefficient is input, and based on the recipe, the MFCs 31a to 3 are used.
4a, each impedance matching device 60, and each high frequency power supply R are controlled.

Although not shown, the space inside the chamber 4 on the front surface side of the Si wafer W and the space inside the chamber 4 on the back surface side are gas-sealed from each other. That is, from the gas supply unit 30 to the shower head unit 4 on the front surface side.
Each gas is supplied through 0, and the back side is supplied with a purge gas from a back side purge system (not shown) so that both gases do not flow into the space regions on the opposite side.

An example of the method for forming an antireflection film according to the present invention using the processing apparatus 1 thus constructed will be described. In addition, each operation of the processing device 1 described below is controlled automatically or based on an operation by an operator, by the above-described control unit 80 and / or another control device (system) (not shown) or manually. FIG. 3 is a flowchart showing the flow of processing including the procedure of one embodiment of the method for forming an antireflection film according to the present invention. FIG. 4 is a flow chart showing the flow of processing in a part of the procedure shown in FIG. 3 in more detail. Further, FIGS. 5A to 5D are process diagrams showing a state in which an antireflection film is formed on the Si wafer W by the procedure shown in FIG.

First, prior to the formation of the antireflection film, Si
A base layer 101 made of Al, polysilicon, or the like is formed on the base layer 100 of the wafer W (step S1; FIG. 5A).
reference). Next, the exhaust system 70 is operated to reduce the pressure in each chamber 4 to a predetermined pressure. Under this reduced pressure, the wafer transfer robot 23 moves the load lock chambers 6a, 6a and 6b.
The Si wafer W having the underlayer 101 previously held in b is transferred into the predetermined twin chamber 3 via the transfer chamber 2.

Next, the two Si wafers W are placed and accommodated on the susceptors 5 in the two chambers 4 provided in the twin chamber 3. After that, He gas is supplied from the gas supply source 33 through the pipe 10 into both chambers 4, and the pressure is adjusted so that the inside of each chamber 4 has a constant pressure. After the pressure in each chamber 4 is stabilized, SiH ₄ gas, N ₂ O gas, and He gas are supplied from the respective gas supply sources 31 to 33 to the respective shower head parts 40 through the pipe 10. At this time, the pressure in each chamber 4 is preferably 250 to 1600 Pa (2
~ 12 Torr), more preferably 500-1300P
It is adjusted to be a (4 to 10 Torr).

The supply flow rate of each gas at this time varies depending on the properties of the antireflection film to be finally formed, the volume of the chamber 4, etc., and can be set appropriately, but the thickness is about 100 to 400 Å. When forming the ultra-thin film, the flow rate range shown below is suitable, for example.・ SiH ₄ gas: 50 to 200 ml / min (sccm) ・ N ₂ O gas: 100 to 600 ml / min (sccm) ・ He gas: 2000 to 8000 ml / min (sccm) Further, SiH ₄ gas supply flow rate and N ₂ It is suitable to supply both gases so that the ratio to the supply flow rate of O gas is preferably 1: 1 to 1: 4, more preferably 1: 2 to 1: 3. By appropriately adjusting the supply flow rate ratio of both gases, the refractive index and the extinction coefficient of the film to be processed 102 can be set to any combination that satisfies a certain correlation.

Each gas introduced into the inner space of each shower head portion 40 from the gas supply port 9 in this manner is dispersed and sufficiently mixed by the blocker plate 43, and the blocker plate 43 and the face are passed through a plurality of through holes. It flows out into the space between the plate 45. The mixed gas flows out below the shower head portion 40 through the plurality of through holes of the face plate 45, and is supplied onto the Si wafer W placed on the susceptor 5.

On the other hand, while supplying these gases into each chamber 4, electric power is supplied to the heater 51 of the susceptor 5 to heat the Si wafer W to a predetermined temperature via the susceptor 5. In this case, the temperature of the Si wafer W (substrate temperature, film formation temperature) is preferably 100 ° C. or higher, more preferably 350 to 500 ° C. As a result, the film forming raw material gas reaching the Si wafer W is reacted.

Immediately above the Si wafer W, various elementary reactions (thermochemical reactions) occur and are involved in a complicated manner, and the active species (controlling factor) of the chemical species depending on the equilibrium and rate-controlling conditions according to the state of the reaction field. ) Is generated, various intermediate products are formed by the reaction of these chemical species, and the processed film 102 made of the SiON film is deposited and formed on the Si wafer W (step S).
2, film forming step; see FIG. 5 (b)). This processed film 102
The film thickness of is preferably not excessively thick, for example, from the viewpoint of sufficiently exhibiting the effect of modification described later, for example, several nm to
The present invention can be extremely effective for the film to be processed 102 having a film thickness of 300 nm, or even several nm to 100 nm.

The supply of each gas is stopped after the film forming process is carried out for a time corresponding to the film forming speed until the film 102 to be processed having a predetermined film thickness is formed. Then, continuously or as necessary, the gas remaining in each chamber 4 is purged with He gas or N ₂ gas, and then N ₂ O gas is supplied to the gas supply source 3
It is supplied from 2 to each shower head portion 40 through the pipe 10. At this time, the pressure in each chamber 4 is adjusted to preferably 250 to 1600 Pa (2 to 12 Torr), and more preferably 400 to 1300 Pa (3 to 10 Torr).

After the pressure in the chamber 4 becomes stable, the high frequency power is output from the high frequency power supply R and the shower head section 40 is operated.
Apply to. As a result, the Si wafer W in the chamber 4 is
Plasma is formed by glow discharge in the upper space. At this time, the impedance matching device 60 is used to
The output impedance of the high frequency power supply R is matched with the combined impedance of the impedance of the plasma and the impedance of the impedance matching device 60 on the plasma (strictly speaking, glow discharge part) side, that is, the load. Here, the condition of the high frequency power is not particularly limited, but examples thereof include the following conditions.・ Frequency: 1 to 50 MHz ・ Output: 0.2 to 5 kW

If this frequency is less than 1 MHz, it tends to be difficult to obtain a sufficient active species density in plasma. On the other hand, if the frequency exceeds 50 MHz, it tends to be difficult to obtain sufficient active species energy. The output is 0.
When it is less than 2 kW, there is a tendency that the plasma processing efficiency cannot be sufficiently enhanced. On the other hand, if this output exceeds 5 kW, arcing discharge may occur in the chamber 4.

Active species such as ions and radicals derived from N ₂ O gas are generated in the plasma, and the film 102 to be processed on the Si wafer W is exposed to these active species. Among the active species, those containing oxygen atoms (for example, O ^* , NO ^*, etc.) oxidize the film to be processed 102 from its surface layer portion or as an oxidizing factor by diffusing the inside or interface portion. Target film 10
The portion in contact with the oxidizing factor in 2 is further oxidized to change its composition to form the antireflection film 103 in which at least a part of the film is modified (step S3, modification step; FIG. 5).
(See (C)).

At least a part of the antireflection film 103 thus obtained by the oxidation and modification is the film to be treated 102.
And the composition or the denseness of the film may differ significantly. As a result, a refractive index and an extinction coefficient that are significantly different from the refractive index and the extinction coefficient that satisfy the certain correlation expressed by the film to be processed 102 are developed. Then, after a lapse of a predetermined time, the application of the high frequency power from the high frequency power supply R to the shower head portion 40 is stopped, and step S3 as the reforming step is ended.

Next, S with the antireflection film 103 formed thereon
The i-wafer W is carried out of each chamber 4, and the organic photosensitive resin composition for photoresist is applied onto the antireflection film 103 of the Si wafer W by, for example, spin coating to form a resist film 104 ( Step S4; FIG. 5 (D)
reference). After that, exposure is performed using a mask, and further development is performed to perform processing such as transferring the mask pattern onto the Si wafer W.

Although a series of processing has been described above with respect to steps S1 to S4, in the present embodiment, prior to step S2, film formation conditions are determined (step S1).
0) is performed, the plasma processing conditions are determined (step S20) prior to step S3, and these conditions are input to the control unit 80 as a part of the recipe. The procedure of the processes in steps S10 and S20 will be described with reference to FIGS.

FIG. 6 is a graph-like drawing showing the relationship between the refractive index and extinction coefficient of the film to be processed formed in step S2 and the refractive index and extinction coefficient of the antireflection film formed in step S3. Is. Line Lk in FIG.
Is a straight line showing an example of a constant correlation between the refractive index and the extinction coefficient of the film to be processed, and the line Lk in FIG.
Is the same as Further, the subscripted region R indicates the range of the refractive index and extinction coefficient (hereinafter, simply referred to as “film quality” in the description of FIGS. 4 and 6) of the film to be processed, and the subscripted region X is The range of film quality of the antireflection film obtained by modifying the treated film is shown. Further, the symbol F with a subscript indicates the supply flow rate or the supply flow ratio of the SiH ₄ gas when forming the film to be processed, and the symbol t with a subscript indicates the plasma formation time when the film to be processed is modified. Indicates.

The film quality required for the antireflection film 103 is assumed to be that of the region Xm shown in FIG. First, the film to be processed is formed by variously changing the film forming conditions, the film qualities of the obtained plural films to be processed are measured, and the relationship represented by the reference line Lk is acquired from these measurement data. Yes (step S31). Next, for example, F1 when forming a film to be processed having the film quality with the region R0 in FIG. 6 as a reference region
Figure out. Further, a plasma formation time t1 as a plasma processing condition for obtaining an antireflection film in the region X0 having a refractive index similar to that of the antireflection film 103 in the region Xm is previously obtained for the film to be processed in the region R0. It is determined from the relationship between the plasma processing conditions and the variation of the film quality (step S32).

Next, a difference Δkm between the extinction coefficient of the antireflection film 103 in the area Xm having substantially the same refractive index and the extinction coefficient of the antireflection film in the area X0 is calculated (step S33). Based on this difference Δkm, the region Rm corresponding to the film to be processed for obtaining the antireflection film 103 having the film quality of the region Xm by the plasma processing is determined (step S34). Along with this, the plasma formation time tm can also be determined. Furthermore, the distance between the region Rm and the region R0 on the line Lk,
That is, from the variation of the film quality from the region R0 to Rm, SiH
The difference ΔFm of the _four gases is determined (step S35).

Then, the SiH ₄ gas flow rates F1 and ΔFm
To obtain the film to be processed having the film quality of the region Rm from
The film forming condition including the iH ₄ flow rate Fm is determined, and the plasma processing condition including the plasma forming time tm for the target film is determined (step S36). As described above, while the film to be processed (conventional antireflection film) obtained by the conventional film forming method is limited to the film quality that satisfies the relationship of the line Lk, according to the present embodiment, the line in FIG. As indicated by Ln, only the extinction coefficient can be independently changed while keeping the refractive index substantially constant.

From a different point of view, if the conventional film forming method is performed starting from the film quality of the region X0, the relationship is probably limited to the line Le shown in FIG. According to this embodiment, it becomes possible to control the refractive index and the extinction coefficient independently to obtain an antireflection film having an arbitrary film quality. The regions X0, Xm and the regions R0,
Rm is set as appropriate or desired, and the area X shown in FIG.
It can be generalized and expressed as i and Ri.

According to the processing apparatus 1 thus configured and the method of forming an antireflection film using the processing apparatus 1, the step S2 is performed.
In each chamber 4, Si having an underlayer 101
After the processed film 102 made of the SiON film is formed on the wafer W, step S3 is continuously performed in the same chamber 4, the processed film 102 is subjected to N ₂ O plasma processing, and at least a part thereof is oxidized.・ Reform. The antireflection film 103 thus obtained is considered to be different from the film to be treated 102 in composition, density, crystalline / amorphous state, etc. of the modified portion, and as a result, the antireflection film 103 as a whole is Significantly different from the target film 102, that is, the line L
A refractive index n and an extinction coefficient k that are not bound by the relationship of k are developed. Therefore, for example, it is possible to obtain the antireflection film 103 capable of exhibiting the desired refractive index n and extinction coefficient k required by lithography depending on the underlying layer 101.

Prior to steps S2 and S3, desired antireflection film 103 is formed in steps S10 and S20.
The film forming conditions and the plasma processing conditions capable of accurately obtaining the required refractive index and extinction coefficient are determined, and the antireflection film 103 is formed by the film formation and the modification of the film to be processed 102 according to the recipe corresponding thereto. Since the formation is performed, the antireflection film 103 can be surely obtained. Therefore, the controllability of the refractive index and extinction coefficient of the antireflection film can be markedly improved, and the optical characteristics of the antireflection film required by lithography can be widely applied.

Further, when the SiH ₄ gas flow rate as the film forming condition and the plasma forming time as the plasma processing condition are properly adjusted, the refractive index and the extinction coefficient of the antireflection film 103 can be more easily and sharply adjusted. Can be controlled. Therefore, it becomes possible to form the antireflection film 103 which is more versatile.

Furthermore, since N ₂ O gas, which has lower reactivity with the silane-based gas than O ₂ gas or O ₃ gas, is used as the reforming gas, SiH ₄ gas is used as the film forming raw material gas. In the above-described embodiment, after performing the film forming process in step S2, the plasma treatment in step S3 can be performed without discharging the residual SiH ₄ gas in the chamber 4. Therefore, the processing efficiency and thus the throughput can be improved.

The present invention is not limited to the above-described embodiment, and for example, step S2 (film forming step)
In, in the same manner as in step S3 (reforming step) described above, plasma may be formed by applying high frequency power.
The condition of the high frequency power in this case is not particularly limited, and examples thereof include the following conditions: -Frequency: 1 to 50 MHz-Output: 0.01 to 1 kW. Furthermore, as a plasma processing condition, instead of or in addition to the plasma formation time, a high frequency power source is used.
The refractive index and extinction coefficient of the antireflection film 103 may be controlled by appropriately adjusting the frequency of the high frequency power output from R.

Further, the apparatus for forming the antireflection film is not limited to the apparatus having the twin chamber 3 like the processing apparatus 1, but may be a CVD chamber composed of a monochamber or a system provided in the CVD chamber main frame. Furthermore, as the reforming gas, N ₂ O is used.
O ₂ gas or the like may be used in place of the gas. In this case, after the film 102 to be processed is formed in step S2, the inside of the chamber 4 is once purged so that SiH ₄ remaining in the chamber 4 can be removed. There is an advantage that the reaction between the gas and O ₂ gas can be suppressed. In addition, the film forming raw material gas and the reforming gas are not limited to those in the above embodiment.

[0070]

EXAMPLES Hereinafter, specific examples according to the present invention will be described, but the present invention is not limited thereto.

<Embodiment 1> The processing apparatus 1 shown in FIGS.
A processing device (Applied Materials, Inc .; a device based on Producer (registered trademark)) having the same configuration as the above was prepared. Using this device, the film to be processed 1 on the Si wafer W
02 (film thickness: approximately 30 nm) was formed (step S
2). At this time, the pressure in each chamber 4 of the twin chamber 3 was reduced to about 9.5 Torr, and SiH ₄ gas, N ₂ O gas, and He gas were supplied at a flow rate of 115 sccm, 240 sccm, and 4400 sccm for 10 seconds, respectively, and then 1
A high frequency power of 3.56 MHz was applied to the shower head portion 40 at an output of 70 W to form plasma and deposit for 10 seconds.

Then, SiH ₄ gas, N ₂ O gas and He
The gas supply was stopped, the valve system V was opened for 5 seconds to exhaust the residual gas in the chamber 4, and then N ₂ O gas was supplied into the chamber 4 at a flow rate of 4000 sccm to a pressure of about 2.5 Torr. After that, high frequency power of 13.56 MHz was applied to the shower head portion 40 at an output of 240 W to form plasma, and plasma treatment was performed for 30 seconds.
Next, the application of high frequency power is stopped and N ₂ is applied for 10 seconds.
After continuing the supply of O gas, high frequency power of 13.56 MHz was applied again to the shower head portion 40 at an output of 240 W to form plasma, and the plasma treatment was performed again for 30 seconds. As a result, the film to be processed 102 was oxidized and modified to form the antireflection film 103.

At this time, the SiH ₄ gas flow rate as the film forming condition and the plasma formation time as the plasma processing condition were calculated as follows. Reference is now made to FIG. 7 for ease of explanation. FIG. 7 shows measurement data of the refractive index n and the extinction coefficient k of the antireflection film obtained in Example 1 and the processed films obtained in Comparative Examples 1 to 13 (described later) (refractive index n and (Measurement of extinction coefficient k))). In the figure, the region Xa shows the range of the refractive index and the extinction coefficient required for the antireflection film obtained in Example 1.

First, the measured data for the comparative example was function-fitted by the method of least squares to obtain a constant correlation (line Lk). Then, from the relationship between the arbitrary regions R0 on the line Lk in FIG. 7 and the regions Xa, X0, Ro, the extinction coefficient difference Δka is determined in the same manner as described with reference to FIGS. 4 and 6. The difference ΔFa of the SiH ₄ flow rate was obtained, and the film forming conditions and plasma processing conditions in the above-mentioned steps S10 and S20 were determined.

Table 1 shows the main processing conditions. In the table,
The chambers A and B indicate the two chambers 4 provided in the twin chamber 3, and the gas flow rate under the film forming conditions and the reforming conditions is the total supply flow rate to both chambers A and B. The other conditions are common to both chambers. Further, “RF” in the table indicates high frequency power, and “spacing” indicates a distance (distance) between the lower surface of the face plate 45 of the shower head unit 40 and the upper surface of the Si wafer W.

<Comparative Examples 1 to 13> Without carrying out the reforming step,
Except that the film forming conditions in the film forming step were variously changed as shown in Table 1, the film to be processed 102 (film thickness: generally, was formed on the Si wafer W by using the same device as that used in Examples 1 and 2. 30 nm) was deposited.

<Measurement of Refractive Index n and Extinction Coefficient k> For the antireflection films formed in Examples 1 and 2 and Comparative Examples 1 to 13, n & k Analyzer 120 manufactured by n & k was used.
0 and 1500, the probe light wavelength is 248 nm
(Deep-UV ray), refractive index n and extinction coefficient k
Was measured. Table 1 also shows the measurement results of the refractive index n and the extinction coefficient k.

[0078]

[Table 1]

In FIG. 7 referred to above, the white symbols indicate that they are the data of the antireflection film of the embodiment,
The black symbols indicate the data of the antireflection film of the comparative example. It was found that the correlation formula of the line Lk obtained from the comparative example is represented by the following formula (2); k = 1.690 × n−3.046 (2) Shows the extinction coefficient, and n shows the refractive index). On the other hand, it was confirmed that the refractive index and the extinction coefficient of the antireflection film obtained in Example 1 were within the required region Xa existing at the position deviating from the line Lk on the graph. From this result, the antireflection film according to the present invention shows that the refractive index n and the extinction coefficient satisfying the relationship represented by the following formula (1); k> 1.690 × n−3.046 (1) It is understood to express k.

[0080]

As described above, according to the method and apparatus for forming an antireflection film of the present invention, a film to be processed obtained by performing the film forming process is subjected to plasma treatment to form the film to be processed. Since the oxidized / modified antireflection film is formed, it is possible to realize an antireflection film exhibiting an arbitrary and desired refractive index and extinction coefficient that cannot be achieved conventionally. In addition, the processing conditions in the film forming step and the modifying step are determined based on the correlation between the refractive index and the extinction coefficient of the film to be processed and those of the required antireflection film, thereby obtaining the desired value. Since the antireflection film can be reliably formed, the controllability of the refractive index and extinction coefficient of the antireflection film can be significantly improved. Therefore, the antireflection film formed by the method and apparatus for forming an antireflection film of the present invention exhibits desired refractive index and extinction coefficient.

[Brief description of drawings]

FIG. 1 is a horizontal sectional view schematically showing a preferred embodiment of an apparatus for forming an antireflection film according to the present invention.

FIG. 2 is a sectional view (partial configuration diagram) showing a main part of the processing apparatus 1 shown in FIG.

FIG. 3 is a flowchart showing a processing flow including a procedure of an embodiment according to a method for forming an antireflection film according to the present invention.

FIG. 4 is a flowchart showing in more detail the flow of processing in part of the procedure shown in FIG.

5A to 5D are process diagrams showing a state in which an antireflection film is formed on the Si wafer W by the procedure shown in FIG.

FIG. 6 is a graph format showing the relationship between the refractive index and extinction coefficient of the film to be processed formed in step S2 and the refractive index and extinction coefficient of the antireflection film formed in step S3.

7 is an antireflection film obtained in Example 1, and Comparative Examples 1 to 1. FIG.
14 is a graph showing measurement data of the refractive index n and the extinction coefficient k of the film to be processed obtained in No. 13.

FIG. 8 is a graph showing measurement data of refractive index and extinction coefficient of the films to be processed obtained in Comparative Examples 1 to 13.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Processing device (antireflection film forming device), 4 ... Chamber (film forming chamber, reforming chamber), 5 ... Susceptor,
8 ... Cleaning system, 30 ... Gas supply part, 31 ... Gas supply source (film forming raw material gas supply part), 32 ... Gas supply source (reforming gas supply part), 40 ... Shower head part, 51 ... Heater, 60 ... Impedance matching device, 70 ... Exhaust system,
80 ... Control part, 101 ... Underlayer, 102 ... Processed film, 1
03 ... Antireflection film, 104 ... Resist film, R ... High frequency power source, W ... Si wafer (base).

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI H01L 21/027 G02B 1/10 A 21/31 H01L 21/30 574 (56) Reference JP-A-10-96801 (JP, A ) JP 9-25571 (JP, A) JP 11-11901 (JP, A) JP 2000-290044 (JP, A) JP 2003-100592 (JP, A) JP 2000-282233 (JP , A) Special table 2002-513948 (JP, A) (58) Fields surveyed (Int.Cl. ⁷ , DB name) G02B 1/11

Claims (9)

(57) [Claims] 1. A method of forming an antireflection film exhibiting a predetermined refractive index and extinction coefficient on a substrate, which comprises supplying a film forming source gas onto the substrate and subjecting the substrate to treatment. A film forming step of forming a film, a reforming gas containing oxygen atoms in its molecule is supplied onto the substrate on which the film to be processed is formed, and plasma is formed around the substrate to form the film. A modification step of modifying the treated film into the antireflection film having a refractive index and an extinction coefficient different from those of the film to be treated, and a film-forming step obtained in advance before carrying out the film-forming step. Based on the correlation between the refractive index and the extinction coefficient of the film to be processed obtained when the film conditions are changed, based on the predetermined refractive index and extinction coefficient required for the antireflection film, Condition setting process for determining film forming conditions in the film forming process and plasma processing conditions in the modifying process And
A method for forming an antireflection film, comprising: 2. The condition setting step is obtained by performing the modifying step on a film to be processed obtained under arbitrary film forming conditions in the film forming step, and is required for the antireflection film. Film to be processed for obtaining the antireflection film based on the difference between the extinction coefficient of a virtual film having a refractive index substantially equal to that of the antireflection film and the extinction coefficient required for the antireflection film. The method for forming an antireflection film according to claim 1, wherein the film forming conditions for forming a film are determined. 3. A film forming step of supplying a film forming source gas onto a substrate to form a film to be processed on the substrate, and oxygen atoms in the molecule on the substrate on which the film to be processed is formed. A reforming step of reforming the film to be treated into an antireflection film having a refractive index and an extinction coefficient different from those of the film to be treated by supplying a reforming gas containing the same to perform a plasma treatment. A film forming condition of the film to be processed in the film forming step, and the modifying step so that the extinction coefficient of the antireflection film changes while maintaining the refractive index of the antireflection film substantially constant. A method for forming an antireflection film, comprising: adjusting the plasma treatment conditions in step 1. 4. A film forming step of supplying a film forming raw material gas onto a substrate to form a film to be processed on which the refractive index and the extinction coefficient have a constant correlation, On the substrate on which the film is formed, while supplying the reforming gas containing oxygen atoms in the molecule, plasma is formed around the substrate, and the film to be processed is refracted out of the above-mentioned certain correlation. A modification step of modifying the antireflection film to have a refractive index and an extinction coefficient, and the difference between the constant correlation and the refractive index and the extinction coefficient required for the antireflection film. A method of forming an antireflection film, wherein film forming conditions of the film to be processed in the film forming step and plasma processing conditions in the modifying step are determined according to the above. 5. When a plurality of kinds of gases are used as the film forming source gas in the film forming step, a supply flow ratio of the plurality of kinds of gas is determined as a film forming condition in the film forming step, 2. The plasma formation time is determined as a plasma processing condition in a quality process.
5. The method for forming an antireflection film according to any one of items 4 to 4. 6. In the film forming step, a silane-based gas as the film forming material gas, a gas containing a nitrogen atom in the molecule, and a gas containing an oxygen atom in the molecule are supplied onto the substrate, 6. A silicon oxynitride film is formed as the antireflection film, and in the reforming step, a nitrogen oxide-based gas is supplied onto the substrate as the reforming gas. The method for forming an antireflection film as described in 1 above. 7. An apparatus in which an antireflection film exhibiting a predetermined refractive index and extinction coefficient is formed on a substrate, the film forming chamber containing the substrate, and the film forming chamber. A film forming source gas supply unit that is connected and that supplies a film forming source gas into the film forming chamber; and a film forming unit that forms a film to be processed on the substrate; A reforming chamber that accommodates a substrate on which a treated film is formed, and a reforming gas that is connected to the reforming chamber and that supplies a reforming gas containing oxygen atoms in its molecule into the reforming chamber. A gas supply unit, an electrode installed in the reforming chamber, and a high-frequency power source connected to the electrode, and high-frequency power output from the high-frequency power source is applied to the electrode. Plasma is formed in the reforming chamber, and the film to be processed becomes And a modified portion that is modified into the antireflection film having a different refractive index and extinction coefficient, and the processed film obtained when the film forming conditions are changed in the film forming unit. Based on the correlation between the refractive index of the film and the extinction coefficient and the refractive index and the extinction coefficient of the antireflection film, the film forming conditions in the film forming section and the plasma processing conditions in the modifying section are set. An apparatus for forming an antireflection film, comprising: a controller for adjusting. 8. The film forming chamber, wherein the film forming source gas supply unit supplies a silane-based gas as the film forming gas, a gas containing a nitrogen atom in a molecule, and a gas containing an oxygen atom in a molecule. 8. The reforming gas supply section supplies a nitric oxide-based gas as the reforming gas into the reforming chamber. Anti-reflection film forming device. 9. An antireflection film is formed by the method according to claim 1, and is represented by the following formula (1); k> 1.690 × n−3.046 (1) ), K: extinction coefficient at a film thickness of 30 nm, n: refractive index at a film thickness of 30 nm, which is made of a silicon oxynitride film.