JP3190098B2 - Method for manufacturing semiconductor device - 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 for manufacturing a semiconductor device, and more particularly to a method for filling a connection hole.

[0002]

2. Description of the Related Art In recent years, large-scale integrated circuits (ICs) formed by integrating a large number of transistors, resistors, and the like into an important part of a computer or a communication device so as to achieve an electric circuit are integrated on one chip. LSI) is frequently used. For this reason, the performance of the entire device is greatly related to the performance of the LSI alone.

[0003] The performance of an LSI alone can be improved by increasing the degree of integration, that is, by miniaturizing elements. As the element becomes finer, the diameter of the contact hole such as a contact hole or via hole becomes smaller, and the aspect ratio of the contact hole becomes higher. As a result, the connection hole is formed by Al
If the film is buried, the thickness of the Al film on the side wall at the bottom of the connection hole becomes thin, which causes a problem of disconnection failure. Further, since the Al film has a high reflectance, there is a problem that the dimensional accuracy of the resist pattern is deteriorated.

[0004] That is, as shown in FIG.
When the connection hole 45 of the interlayer insulating film 42 formed on the substrate 1 is buried with the uneven Al film 43, the portion not to be exposed by the reflected light 47 of the exposure light 46 incident on the uneven portion, in this case, The resist 44 on the connection hole 45 is exposed.

As a result, as shown in FIG. 17B, there arises a problem that the resist pattern 48 on the connection hole 45 becomes smaller than a predetermined size. Therefore, an attempt has been made to bury a metal, particularly tungsten (W), in the connection hole by using a selective CVD method to flatten the buried shape.

However, in order to embed connection holes having different depths by this kind of method, as shown in FIG. 18A, the amount of W to be buried is adjusted to the shallower connection hole 45b, or FIG. As shown in (b), it is aligned with the deeper connection hole 45a. When the buried amount of W is adjusted to the shallower connection hole 45b, the deeper connection hole 4b is formed.
W cannot be buried up to the upper surface of 5a. On the other hand, if it is adjusted to the deeper side, there is a problem that W overflows from the shallower connection hole.

[0007]

As described above, in the conventional method of filling the connection holes using the sputtering method, the thickness of the Al film on the side wall at the bottom of the connection holes becomes thin, so that a disconnection failure occurs. was there. Further, in the method of filling the connection holes using the selective CVD method, if there are connection holes having different depths, there is a problem that not all the connection holes can be filled with W to the upper surface.

The present invention has been made in consideration of the above circumstances, and an object thereof is to provide a method in which all connection holes having different depths are formed by W to the upper surface without lowering the reliability due to disconnection or the like. An object of the present invention is to provide a method for manufacturing a semiconductor device which can be embedded.

[0009]

The gist of the present invention resides in that an etching gas containing chlorine, sulfur hexafluoride and oxygen is used.

[0010]

[0011]

[0012]

In order to achieve the above object, a method for manufacturing a semiconductor device according to the present invention comprises the steps of: forming a plurality of connection holes having different depths in an insulating film provided on a substrate; Selectively forming a tungsten film in the connection hole so that the tungsten film is filled up to the upper surface of the deepest connection hole by using a selective CVD method, and forming a resist so that the tungsten film is covered on the insulating film. And etching the tungsten film and the resist by discharging an etching gas containing chlorine, sulfur hexafluoride, and oxygen, and embedding the tungsten film in the connection holes, the resist Detecting the disappearance of the resist from the intensity of emission of carbon monoxide generated during the etching of the resist.

The etching of the tungsten film and the resist is performed by accommodating the semiconductor substrate in a reaction vessel, applying a high-frequency power to the reaction vessel to discharge the etching gas, and a power density of the high-frequency power. To P
o (W / cm ₂ ), pressure Pr (mTo
rr), when the diameter of the connection hole is R (μm) and the thickness of the tungsten film overflowing from the upper surface of the connection hole is F (μm), the flow rate of the chlorine, the flow rate of the sulfur hexafluoride, and The oxygen flow rate is -240Po + 0.44Pr-0.8 [(Cl ₂ flow rate) ÷ {(Cl ₂ flow rate) + (SF ₆ flow rate) + (O ₂ flow rate)}] + 115-28.8 {( F + R) ÷ F} ≦ (O ₂ flow rate) ÷ {(Cl ₂ flow rate) + (SF ₆ flow rate) + (O ₂ flow rate)} ≦ −240Po + 0.44Pr-0.8 [(Cl ₂ flow rate It is desirable that the flow rate is set at (flow rate) ÷ {(flow rate of Cl ₂ ) + (flow rate of SF ₆ ) + (flow rate of O ₂ )}] + 115 + 11.1 {(F−0.05) ÷ F}.

In the above etching, instead of an etching gas containing chlorine, sulfur hexafluoride and oxygen,
When an etching gas having at least sulfur hexafluoride and oxygen is used, the flow rate of the sulfur hexafluoride and the flow rate of the oxygen are calculated as follows: -240Po + 0.38Pr + 210-28.8 {[(F + R) ÷ F} ≦ (O ₂ flow rate) ÷ {((SF ₆ flow rate) + (O ₂ flow rate)} ≦ −240Po + 0.38Pr + 210 + 11.1 {(F-0.05) ÷ F} Instead of the etching gas containing sulfur fluoride and oxygen, an etching gas containing at least chlorine and sulfur hexafluoride may be used.

[0016]

[0017]

[0018]

[0019]

In the method of manufacturing a semiconductor device according to the present invention (claim 1) , the W film and the resist are etched using an etching gas containing chlorine, sulfur hexafluoride, and oxygen. At this time, carbon atoms of the resist are combined with oxygen radicals to generate carbon monoxide, and emission light due to the carbon monoxide is generated during discharge. The intensity of the emitted light (emission intensity) of carbon monoxide depends on the remaining amount of the resist. That is, since the disappearance of the resist basically starts from a certain portion on the substrate and thereafter tends to spread over the entire substrate, the emission intensity becomes weaker as the loss of the resist spreads over the entire substrate, and It becomes constant at the time of disappearance. Therefore, by monitoring the light emission intensity, it is possible to know the point at which the resist has disappeared, so that over-etching of the W film can be prevented, and a good embedded shape can be easily obtained.

[0020]

Embodiments will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram of a dry etching apparatus using a magnetron discharge according to a first embodiment of the present invention.

A cathode plate 7 is provided at the bottom of the etching chamber 2 of the etching apparatus. This cathode plate 7
Is fixed to the reaction vessel 1 constituting the etching chamber 2 by the insulating member 15. 13.56 MHz high frequency power is supplied to the cathode plate 7 from the power supply 9 via the matching circuit 8. The cathode plate 7 has a cooling pipe 10
a, 10b are provided, and the temperature of the cathode plate 7 is controlled by a solvent flowing from the cooling pipe 10a toward the cooling pipe 10b. The cooling pipe 10b also serves as a lead wire for supplying high-frequency power to the cathode plate 7. A copper plate 12 sandwiched between polyimide films 11 is adhered on the cathode plate 7. A voltage of 4 kV is applied to the copper plate 12 from a power supply 13. As a result,
The substrate 17 to be processed is attracted and fixed to the cathode plate 7 by electrostatic force.

On the other hand, the upper wall of the etching chamber 2 is
It is 8. The anode plate 18 is provided with a gas inlet 3 for introducing a reaction gas. The reaction gas introduced into the etching chamber 2 through the gas inlet 3 is exhausted from the exhaust port 4 to the outside of the chamber.

Outside the etching chamber 2, a magnetic field generator comprising a plurality of permanent magnets 5 and a driving mechanism 6 for rotating these permanent magnets 5 is provided. A magnetic field is formed in a space between the anode and the anode plate 18.

In the drawing, reference numeral 14 denotes a gas introduction pipe for introducing a gas into the back surface of the substrate 17 to control the temperature of the substrate 17, and 16 denotes a lead of the copper plate 12 of the electrostatic chuck and a cathode plate. 7 shows an insulating member for preventing electrical connection between the power supply 7 and the power supply 7. Next, a method of flattening the W film using the etching apparatus configured as described above will be described with reference to the process sectional view of FIG.

First, as shown in FIG. 2A, a W film 22 is deposited on a substrate 21 on which desired element processing has been performed. Here, the surface shape of the W film 22 depends on the influence of a base or the like, for example,
The surface is uneven due to wiring and the like. Next, as shown in FIG. 2B, a resist 23 is applied on the W film 22 to flatten the substrate surface.

Next, after the substrate 21 is placed on the cathode plate 7 of the etching apparatus of FIG. 1, the W film 22 and the resist 23 are etched using Cl ₂ gas and SF ₆ gas. Here, Cl ₂ gas and SF ₆ gas are used because the selectivity of the W film 22 to the resist 23 can be set to 1.0 by using these gases. FIG. 3 is a characteristic diagram showing the relationship between the SF ₆ concentration and the etching rate, indicating this. Here, the SF ₆ concentration is defined as in the following equation. (Concentration of SF ₆ ) = (concentration of SF ₆ ) ÷ 100 {(flow rate of Cl ₂ ) + (
SF ₆ flow rate)}

From this figure, it can be seen that the etching rate of W sharply increases as the concentration of SF ₆ increases. This is probably because W is mainly etched by F radicals. Further, it can be seen from this figure that the etching rate of the resist gradually increases as the SF ₆ concentration increases. This is considered to be due to the promotion of the effect of extracting the hydrogen atoms in the resist by the F radicals. When the etching rate of W is compared with the etching rate of the resist, the etching rate of the resist is initially higher than the etching rate of W.
It can be seen that when the concentration of F ₆ is about 80% or more, the etching rate of W becomes higher than the etching rate of the resist. Therefore, by adjusting the concentration of SF ₆ , the selectivity between W and the resist can be made 1.0.
In this embodiment, etching was performed under the following conditions in order to set the selectivity of the W film 22 to the resist 23 to 1.0.

That is, the inside of the etching chamber 2 is 75 mTorr.
r, the substrate temperature was set to 45 ° C., and Cl ₂ gas at a flow rate of 20 SCCM and SF _{6 at a} flow rate of 80 SCCM were supplied from the gas inlet tube 3.
Gas was introduced into the etching chamber 2 and the RF power density was 0.58 W / cm ^2. Is applied to the cathode plate 7, and the horizontal magnetic flux density on the substrate 21 is set to 120 Gauss. When etching is performed under these conditions until the resist 23 disappears, as shown in FIG.
A W film 22 having a flat surface is obtained. Thus, according to the present embodiment, by using the Cl ₂ gas and the SF ₆ gas, the W film 22 having the unevenness on the surface can be easily flattened. FIG.
FIG. 4 is a process cross-sectional view for explaining a method of burying a connection hole according to a second embodiment of the present invention. First, FIG.
As shown in (1), after an interlayer insulating film 32 is deposited on a substrate 31 on which desired element processing has been performed, a connection hole 33 is formed.
Next, as shown in FIG. 4B, after the connection hole 33 is filled with a W film 34 by using a selective CVD method, a resist 3 is formed on the entire surface.
5 is applied.

Next, the substrate 31 is placed on the cathode plate 7 of the etching apparatus shown in FIG. Then, CI ₂ gas and SF ₆ gas are supplied from the gas inlet 3 at flow rates of 20 SCCM and 80 SCCM, respectively.
CM was introduced and the RF power density was reduced to 0.58 W / cm ² The pressure in the etching chamber 2 is set to 75 mTorr, the horizontal magnetic flux density on the substrate is set to 120 Gauss, the substrate temperature is set to 45 ° C., and etching is performed until the resist 35 disappears. As a result, as shown in FIG. 4C, the W film 32 overflowing from the connection hole 33 is removed, and the surface of the interlayer insulating film 32 becomes flat.

Even if the depths of the connection holes are different, as shown in FIG. 5A, after selectively growing the W film 32 in accordance with the deeper connection holes 33a, a resist 33 is applied to the entire surface. Then, if the etching is performed under the above-mentioned etching conditions until the resist 35 disappears, as shown in FIG. 5B, the W film 32 can be buried up to the upper surfaces of the connection holes 33 and 33a. Even when there are three or more connection holes having different depths, if the W film is selectively grown in accordance with the deepest connection hole, the W film 32 is similarly formed up to the upper surfaces of all the connection holes.
Can be embedded.

Thus, according to the present embodiment, even when there are connection holes having different depths, the W film can be buried up to the upper surfaces of all the connection holes, and a good buried shape which does not cause a disconnection failure or the like can be obtained. . Further, even if a metal wiring such as an Al wiring is formed thereon, the base is flat, so that a favorable wiring shape without steps or the like can be obtained. Next, how to select the SF ₆ concentration for setting the selection ratio of W to the resist at 1.0 will be described.

FIG. 6 shows SF ₆ having a selectivity of W to the resist of 1.0, which was examined using the etching apparatus of FIG.
4 is a graph showing a relationship between a concentration and a pressure in an etching chamber. This reduces the RF power density to 0.58 W / cm ² This was fixed and examined. The other conditions, that is, the horizontal magnetic flux density on the substrate, the substrate temperature, and the RF frequency are each 1
20 Gauss, 45 ° C., 13.56 MHz.

FIG. 7 is a graph showing the relationship between the RF power density and the SF ₆ concentration at which the selectivity of W to the resist was 1.0, which was examined using the etching apparatus of FIG. This was obtained by fixing the pressure in the etching chamber at 75 mTorr. Other conditions are the same as those in FIG. Based on these two graphs, when the concentration of SF ₆ at which the selectivity of W to the resist is 1.0 is expressed by using the pressure in the etching chamber and the RF power density, (concentration of SF ₆ ) = 100Po-0.5Pr + 50 (1) Where Po is RF expressed in units of W / cm ₂
The power density, and Pr is the pressure in the etching chamber expressed in units of mTorr.

FIG. 8 shows a case where a mixed gas of SF ₆ gas and O ₂ gas is used (curve b) and a case where a mixed gas of Cl ₂ gas, SF ₆ gas and O ₂ gas is used (curve). A diagram showing the relationship between each etching time and the W film in a) is shown.

The sample was prepared by forming a connection hole in an oxide film having a thickness of 0.5 μm, depositing 1.0 μm of W, and then applying a resist so that the surface becomes flat. This sample is called S
Mixed gas of F ₆ gas and O ₂ gas, Cl ₂ gas and SF ₆ gas
Etching was performed using a mixed gas of a gas and an O ₂ gas.

The etching conditions in the case of using the mixed gas of SF ₆ gas and O ₂ gas, 50S the flow rate of the SF ₆ gas
The flow rate of CCM and O ₂ gas is set to 50 SCCM, and the cathode plate 7
RF power density is 0.75 W / cm ² (RF power = 3
00W), the pressure in the etching chamber was adjusted to 50 mTorr, and the horizontal magnetic flux density on the substrate was 1
20 Gauss was set and the substrate temperature was heated to 65 ° C.

When a mixed gas of Cl ₂ gas, SF ₆ gas and O ₂ gas is used, the etching condition is Cl ₂ gas.
Gas flow rate is 9 SCCM, SF ₆ gas flow rate is 36 SC
CM, O ₂ gas flow rate is 55 SCCM, RF power density is 0.58 W / cm ² (RF power = 234 W), pressure is 200 mTorr, horizontal magnetic flux density is 120 Gauss,
The substrate temperature was 45 ° C.

As can be seen from FIG. 8, the W film thickness is 0.5 μm.
The point indicated by m is the position corresponding to the contact depth and the position of the end point of the etching. When a mixed gas of SF ₆ gas and O ₂ gas is used, the etching rate of W is 500 nm / min until the etching end point, and 1300 n from the end point.
m / min. It has been recognized that this tendency becomes significant as the power density decreases, and also as the pressure increases. However, Cl ₂
When a mixed gas of a gas, SF ₆ gas, and O ₂ gas is used, the etching rate of W does not change before and after the end point of the etching, and becomes 270 nm / min. That is, if a gas obtained by adding a Cl ₂ gas to a mixed gas of the SF ₆ gas and the O ₂ gas is used, the fluctuation of the W etching rate at the end point of the etching can be suppressed. Therefore, it is possible to sufficiently solve the problem that the upper surface of the embedded W film is recessed from the upper surface of the connection hole.

Further, the present inventors etched back the W film by the method described with reference to FIG. 4, and thereafter, deposited Al and examined its shape and the resistance in the connection hole. The diameter of the connection hole was 0.8 μm, and the thickness of the W film overflowing from the upper surface of the connection hole was 0.5 μm.

As a result, when the upper surface of the W film is depressed by 0.8 μm or more from the upper surface of the connection hole, that is, when the aspect ratio becomes 1 or more, the Al coating shape is deteriorated, the wire is easily broken, and the resistance is increased. However, it turned out that it was not suitable as a device. Further, it was found that even when the diameter of the connection hole was changed, when the aspect ratio was 1 or more, the shape of Al coating deteriorated, and the device was not suitable for a device. If the upper surface of the W film protrudes from the upper surface of the connection hole by 0.05 μm or more, the shape of the AI coating deteriorates at the protruding inclined portion of the W film, and the wire is easily broken.

Therefore, the position of the upper surface of the W film is
The recess must be 0.8 μm or less and the protrusion must be 0.05 μm or less based on the upper surface of the connection hole. The dent of the W film is 0.8μm or less and the protrusion is 0.05μm
In order to achieve the following, the selectivity of the W film to the resist is set to 0.
It should be between 9 and 2.6. The range is the range of the oblique lines shown in FIGS. The diameter of the connection hole is F (μm), and the thickness of the W film overflowing from the upper surface of the connection hole is R
(Μm) and using the equation (1), the range of the concentration of SF ₆ at which the selectivity of W to the resist is 0.9 to 2.6 is 100Po-0.5Pr + 50-1.1 {(F-0.05 ) ÷ F} ≦ (flow rate of SF ₆ ) ÷ {(flow rate of Cl ₂ ) + (flow rate of SF ₆ )} ≦ 100Po-0.5Pr + 50 + 13.5 {(F + R) ÷ F} Next SF ₆ concentration selectivity to resist the W film will be described when it is set to other than 1.0 in the method of FIG.

The etching rate of the W film 34 is
9A, the W film 34 is etched so that its center is depressed, as shown in FIG. 9A. When the etching of the W film 34 is completed on the upper surface of the interlayer insulating film 32, as shown in FIG. 9B, the W film 34 remains outside the connection hole 33.

On the other hand, when the etching rate of the resist 35 is faster than the etching rate of the W film 34,
As shown in (a), the W film 34 is etched so that its central portion protrudes. Then, as shown in FIG. 10B, etching is performed even after the resist 35 is completely removed, and the W film 3 overflowing from the upper surface of the connection hole 33 is formed.
4 is removed, as shown in FIG.
The W film 34 does not remain on the outside of 3. here,
As described above, the thickness of the W film 34 overflowing from the connection hole 32 is set to 0.0
Make it 5 μm or less. In order to obtain such a W film 34, etching may be performed within a range defined by the following equation (2). 1 ≦ S ≦ F ÷ (F−0.05) (2) where S is the selectivity of the W film 34 to the interlayer insulating film 32, and F is the thickness of the W film 34 overflowing from the connection hole 32. That's it. Next, a description will be given of a method of embedding a connection hole according to a third embodiment of the present invention.

The method of this embodiment differs from that of the second embodiment in that a mixed gas of Cl ₂ gas, SF ₆ gas and O ₂ gas is used as an etching gas. When such an etching gas is used, carbon monoxide (CO) generated when oxygen radicals are bonded to carbon atoms in the resist emits light during discharge. FIG. 11 is a characteristic diagram showing the relationship between the etching time and the emission intensity due to CO when the etching apparatus of FIG. 1 is used.

This is because the flow rate in the etching chamber is 9
SCCM, 36 SCCM, 55 SCCM Cl ₂ gas,
SF ₆ gas and O ₂ gas are introduced, an RF power density of 0.58 W / cm ₂ is applied to the lower electrode 7, the pressure in the etching chamber is adjusted to 200 mTorr, and the horizontal magnetic flux density on the substrate is reduced. This was obtained by setting the temperature to 120 Gauss, heating the substrate temperature to 45 ° C., and measuring the emitted light having a wavelength of 451 nm. The average value of the etching rate under this condition was 280 nm / min. The thickness of the resist was 450 nm.

From this figure, it can be seen that the emission intensity of CO begins to decrease after the etching time exceeds 1 minute and 30 seconds, decreases to 1 minute and 45 seconds, and becomes constant thereafter. C
The reason why the emission intensity of O changes in this way is that after 1 minute and 30 seconds, a region without a resist starts to expand and the emission intensity decreases, and at 1 minute and 45 seconds, all the resist disappears and the emission intensity decreases. Because it stops. Therefore, C
By monitoring the emission intensity of O, the end point of the etching can be detected. That is, the etching may be terminated when the emission intensity of CO becomes a certain value after the emission intensity decreases.

As described above, according to this embodiment, the end point of the etching can be detected by monitoring the emission intensity of CO, so that the W film can be prevented from being over-etched and the like, and thus the surface shape can be improved. An embedded shape can be easily obtained.

FIGS. 12, 13 and 14 show the etching chamber when the selection ratio of W to the resist becomes 1.0 when a mixed gas of Cl ₂ , SF ₆ and O ₂ is used as the etching gas. graph showing the relationship between the pressure and concentration of O _2, it is a graph representing the relationship between the pressure and the SF ₆ concentration of the etching chamber, a graph representing the relationship between the Cl ₂ concentration and the O ₂ concentration is shown. In the case of FIG. 12, the etching conditions are a horizontal magnetic flux density of 120 Gauss on the substrate, a substrate temperature of 45 ° C., and an RF power density of 0.58 W / cm ^2. ,
The flow ratio of Cl ₂ to SF ₆ was set to 1: 4. FIG.
In the case of 3, the pressure in the etching chamber is set to 75 mTorr.
The flow ratio between r, Cl ₂ and SF ₆ was 1: 4. FIG.
The RF power density is 0.58 W / cm ² The pressure in the etching chamber was set to 75 mTorr. Also, Cl
_{The 2} concentration and the O ₂ concentration are defined as follows. (O ₂ concentration) = (O ₂ flow rate) 2100 {(Cl ₂ flow rate) + (SF ₂
Flow rate) + (flow rate of O ₂ )} (concentration of Cl ₂ ) = (flow rate of Cl ₂ ) ÷ 100 {(flow rate of Cl ₂ ) + (
SF ₆ flow rate) + (O ₂ flow rate)}

Based on these graphs, the concentration of O ₂ when the selectivity of the W film to the resist becomes 1.0 is expressed by
The following equation (3) of the function of the pressure, the RF power density, and the concentration of Cl ₂ is obtained. (Concentration of O ₂ ) =-240Po + 0.44Pr-0.8 (concentration of Cl ₂ ) +115 (3)

Further, for the same reason as described above, the range where the selectivity of the resist to the W film is 0.9 to 2.6 is the range shown by the hatched lines in FIGS. 12, 13 and 14. When the diameter of the connection hole is R (μm), and the thickness of the W film overflowing from the upper surface of the connection hole is F (μm), using the equation (3), the selectivity ratio of W to the resist is 0.9 to 0.9. The range of the concentration of SF ₆ to be 2.6 is -240Po + 0.44Pr-0.8 [(Cl ₂ flow rate) ÷ {(Cl ₂ flow rate) + (SF ₆ flow rate) + (O ₂ flow rate)} ] + 115-28.8 {(F + R) ÷ F} ≤ (O ₂ flow) ÷ {(Cl ₂ flow) + (SF ₆ flow) + (O ₂ flow)} ≤-240Po + 0.44Pr -0.8 [(Cl ₂ flow rate) ÷ {(Cl ₂ flow rate) + (SF ₆ flow rate) + (O ₂ flow rate)}] + 115 + 11.1 {(F-0.05) {F}.

The selectivity of the W film to the resist is 1.0 or less, and the thickness of the W film overflowing from the connection hole is 0.05 μm.
In order to reduce the value to m or less, the etching may be performed within the range defined by the equation (2) as in the previous embodiment.

FIGS. 15 and 16 show the pressure and the O ₂ concentration in the etching chamber when the selectivity of W to the resist becomes 1.0 when a mixed gas of SF ₆ and O ₂ is used as the etching gas, respectively. And a graph showing the relationship between the RF power density and the O ₂ concentration. The etching conditions were such that the horizontal magnetic flux density on the substrate was 12
0 Gauss, and the substrate temperature was 65 ° C. And FIG.
5, the RF power density was 0.75 W / cm ² In the case of FIG. 16, the pressure in the etching chamber is set to 50
It is fixed to mTorr. The O ₂ concentration is defined as in the following equation. (O ₂ concentration) = (O ₂ flow rate) ÷ 100 {(SF ₂ flow rate) + (O ₂ flow rate)} Based on these graphs, the selectivity of the W film to the resist was reduced to 1.0. When the concentration of O ₂ is expressed by pressure and RF power density, the following equation (4) is obtained. (Concentration of O ₂ ) =-240Po + 0.38Pr + 210 (4)

For the same reason as described above, the range where the selectivity of the resist with respect to the W film is 0.9 to 2.6 is the range shown by oblique lines in FIGS. The diameter of the connection hole is R (μm), and the thickness of the W film overflowing from the upper surface of the connection hole is F
(Μm) and using the equation (4), the range of the concentration of SF ₆ at which the selectivity ratio of W to the resist is 0.9 to 2.6 is -240Po + 0.38Pr + 210-28.8 {[(F + R) ÷ F} ≤ (O ₂ flow rate) ÷ {((SF ₆ flow rate) + (O ₂ flow rate)} ≤-240Po + 0.38Pr + 210 + 11.1 {(F-0.05) ÷ F} .

Further, the present inventors used the etching apparatus shown in FIG. 1 and determined the relationship between the etching time and the emission intensity due to CO when a mixed gas of SF ₆ gas and O ₂ gas was used as the etching gas. I checked.

That is, a flow rate of 50 SCCM is set in the etching chamber.
SF ₆ gas and O ₂ gas with a flow rate of 50 SCCM were introduced.
A voltage that makes the RF power density 0.75 W / cm ₂ is applied to the lower electrode 7, and the pressure inside the etching chamber is set to 50 mTorr.
To adjust the horizontal magnetic flux density on the substrate to 120 Gauss.
, The substrate temperature is heated to 65 ° C., and the wavelength is 451 nm.
Was measured. The average value of the etching rate was 520 μ / min, and the thickness of the resist was 800 nm.

As a result, a characteristic diagram similar to that of FIG. 11 was obtained. That is, the etching time starts to decrease after 1 minute and 30 seconds, decreases to 1 minute and 45 seconds, and becomes a constant value thereafter.

Therefore, Cl _{2 is used} as an etching gas.
Gas, SF ₆ gas and O ₂ gas,
The end point of the etching can be detected by monitoring the light emission intensity of, and a good buried shape having a flat surface shape can be easily obtained.

In the above embodiment, the W film has been described, but the same effect can be expected with other metal films. In addition, various modifications can be made without departing from the scope of the present invention.

[0059]

As described above in detail, according to the present invention, W
Since the selectivity of the film to the resist can be set to 1.0, even if the W film has irregularities on the surface, it can be flattened, and even if there are a plurality of connection holes having different depths, all connections can be made without causing disconnection failure. The hole can be filled with the W film up to its upper surface.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a dry etching apparatus according to a first embodiment of the present invention.

FIG. 2 is a process sectional view for explaining a method of flattening a W film using the dry etching apparatus of FIG. 1;

FIG. 3 is a characteristic diagram showing a relationship between SF ₆ concentration and etching rate.

FIG. 4 is a process cross-sectional view for explaining a method of burying a connection hole according to a second embodiment of the present invention.

FIG. 5 is a process sectional view for describing an embedding method when there are connection holes having different depths.

FIG. 6 is a diagram showing a relationship between SF ₆ concentration and pressure in an etching chamber.

FIG. 7 is a diagram showing a relationship between SF ₆ concentration and RF power density.

FIG. 8 is a diagram showing a relationship between an etching time and a W film thickness.

FIG. 9 is a view showing a buried shape when the etching rate of W is higher than that of resist etching.

FIG. 10 is a view showing a buried shape when the etching rate of W is lower than that of resist etching.

FIG. 11 is a characteristic diagram showing a relationship between etching time and emission intensity.

FIG. 12 is a diagram showing a relationship between pressure and O ₂ concentration.

FIG. 13 is a diagram showing the relationship between pressure and SF ₆ concentration.

FIG. 14 is a graph showing the relationship between Cl ₂ concentration and O ₂ concentration.

FIG. 15 is a diagram showing a relationship between pressure and O ₂ concentration.

FIG. 16 is a diagram showing a relationship between RF power density and O ₂ concentration.

FIG. 17 is a view for explaining a problem of a conventional method of embedding a connection hole.

FIG. 18 is a view for explaining a problem of a conventional method of embedding a connection hole.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Reaction container, 2 ... Etching chamber, 3 ... Gas inlet, 4
... exhaust port, 5 ... permanent magnet, 6 ..., 7 ... cathode plate, 8 ... matching circuit, 9 ... power supply, 10a, 10b ... cooling pipe, 11
... Polyimide film, 12 ... Copper plate, 13 ... Power supply, 14 ... Gas introduction tube, 15 ... Insulating member, 16 ... Insulating member, 17 ... Substrate to be processed, 18 ... Anode plate, 21 ... Substrate, 22 ... W film, 23
... resist, 31 ... substrate, 32 ... interlayer insulating film, 33 ... connection hole, 34 ... W film, 35 ... resist, 41 ... substrate, 42
... interlayer insulating film, 43 ... Al film, 44 ... resist, 45,
45a, 45b: connection holes, 46: exposure light, 47: reflected light, 48: resist pattern.

Continued on the front page (58) Fields investigated (Int.Cl. ⁷ , DB name) H01L 21/28-21/288 H01L 21/44-21/445 H01L 29/40-29/43 H01L 29/47 H01L 29 / 872 H01L 21/3065

Claims (2)

(57) [Claims] A step of forming a plurality of connection holes having different depths in an insulating film provided on a substrate; and a step of filling the tungsten film up to an upper surface of the deepest connection hole by using a selective CVD method. Selectively forming a tungsten film in the hole, applying a resist on the insulating film so as to cover the tungsten film, discharging an etching gas containing chlorine, sulfur hexafluoride and oxygen. Etching the tungsten film and the resist to bury the tungsten film in the connection holes, and detecting the disappearance of the resist from the intensity of emission of carbon monoxide generated during the etching of the resist. A method for manufacturing a semiconductor device, comprising: 2. The etching of the tungsten film and the resist is performed by accommodating the semiconductor substrate in a reaction vessel, applying high-frequency power to the reaction vessel to discharge the etching gas, and reducing the power density of the high-frequency power. Po (W /
cm ² ), pressure Pr (mTorr) in the reaction vessel,
When the diameter of the connection hole is R (μm) and the thickness of the tungsten film overflowing from the upper surface of the connection hole is F (μm), the flow rates of the chlorine, sulfur hexafluoride, and oxygen are And -240Po + 0.44Pr-0.8 [(Cl ₂ flow rate) ÷ {(Cl ₂ flow rate) + (SF ₆ flow rate) + (O ₂ flow rate)}] + 115-28.8 {(F + R ) ÷ F} ≤ (O ₂ flow rate) ÷ {(Cl ₂ flow rate) + (SF ₆ flow rate) + (O ₂ flow rate)} ≤-240Po + 0.44Pr-0.8 [(Cl ₂ flow rate) ÷ _2. The method according to claim 1 , wherein the flow rate is set to {(Cl ₂ flow rate) + (SF ₆ flow rate) + (O ₂ flow rate)}] + 115 + 11.1 {(F−0.05) ÷ F}. The manufacturing method of the semiconductor device described in the above.