JP2002134479A - Method for manufacturing semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a connecting hole communicating with a wiring material, having low plasma resistance by suppressing increase in a contact resistance, without depending on the area or the depth of an opening, and assuring a processing capability. SOLUTION: A method for manufacturing a semiconductor device comprises the steps of forming an insulating film on a board 10, by using a mixed gas of an octafluorocyclobutane (C4F8) or an octafluorocyclopentene (C5F8), a carbon monoxide (CO), oxygen (O2) and argon (Ar) and processing an insulating film (a second insulating film 24). In this method, supply flow rate of the octafluorocyclobutane (C4F8) or the octafluorocyclopentene is set to 15 to 25 cm3/min.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a semiconductor device, and more particularly, to a method for manufacturing a semiconductor device using an etching gas containing C ₄ F ₈ or C ₅ F ₈ .

[0002]

2. Description of the Related Art In forming connection holes for interconnecting aluminum, aluminum alloy, etc. wires used in a method of manufacturing a semiconductor device, it is required to process very deep holes and to have high plasma resistance to wiring materials. .

[0003]

However, since the plasma resistance of the wiring material is low, there has been a problem that the electrical characteristics between the wirings, especially the contact resistance, increase. When the insulating film is etched using the technique disclosed in Japanese Patent Application Laid-Open No. 11-330057, C ₄ F ₈ or C ₅ F ₈ mainly serving to etch the insulating film.
Is as low as 1 cm ³ / min or more and 4 cm ³ / min or less, so that the etching rate is reduced. for that reason,
There was a problem that it was not possible to escape from insufficient processing capacity and the resulting increase in production costs. Also, when the flow rate of C ₄ F ₈ or C ₅ F ₈ is about 10 cm ³ / min,
In the case where connection holes having different opening areas are to be opened in the same manner, a phenomenon that etching of connection holes having a large opening area stops is problematic.

[0004]

SUMMARY OF THE INVENTION The present invention is a method for manufacturing a semiconductor device which has been made to solve the above-mentioned problems.

The method of manufacturing a semiconductor device according to the present invention comprises the steps of: octafluorocyclobutane (C ₄ F ₈ ) or octafluorocyclopentene (C ₅ F ₈ );
In the method for manufacturing a semiconductor device in which an insulating film is formed on a substrate by using a mixed gas of O), oxygen (O ₂ ), and argon (Ar) as an etching gas, the octafluorocyclobutane (C ₄ F ₈ ) or the supply flow rate of the octafluorocyclopentene (C ₅ F ₈ ) is set to 15 cm ³ / min or more.

In the method of manufacturing a semiconductor device, the supply flow rate of octafluorocyclobutane (C ₄ F ₈ ) or octafluorocyclopentene (C ₅ F ₈ ) is 15 cm ^3.
/ Min or more and 25 cm ³ / min or less,
The etching rate of the barrier layer that should not be etched can be suppressed while ensuring a sufficient etching rate. Therefore, it is possible to process a connection hole having a large aspect ratio at a high speed.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of a method of manufacturing a semiconductor device according to the present invention will be described with reference to a schematic sectional view of FIG. 1 and a schematic sectional view of an etching apparatus of FIG.

First, an example of an etching apparatus used in this embodiment will be described with reference to FIG. As shown in FIG. 2, the etching apparatus 101 is provided with a processing chamber 102 configured to be airtight. In the processing chamber 102,
An upper electrode 111 is provided. Further, the upper electrode 11
A semiconductor substrate 10 to be etched
Is mounted on the lower electrode 121.

The upper electrode 111 is, for example, a pipe 141
Is supplied to the processing chamber 102 through the upper electrode 111. A high frequency power supply 113 is connected to the upper electrode 111.

[0010] Outside the processing chamber 102, a gas supply unit 130 constituted by a plurality of gas sources 131 to 135 is provided. The gas sources 131 to 135 are, for example, an octafluorocyclobutane (C ₄ F ₈ ) gas source 1
31, octafluorocyclopentene (C ₅ F ₈ ) gas source 132, oxygen (O ₂ ) gas source 133, carbon monoxide (C
An O) gas source 134 and an argon (Ar) gas source 135 are provided. On the supply side of each of the gas sources 131 to 135, valves 136 to 140 for controlling individual gas flow rates are installed. The gas sources 131 to 135 are connected to the upper electrode 111 as one system pipe by a pipe 141 via the valves 136 to 140. The piping 141 has valves 136 to 140 and the processing chamber 10.
142 for controlling the flow rate of the gas mixed between
Is installed.

On the other hand, the lower electrode 121 has a susceptor structure on which the substrate 10 can be mounted.
2 are connected.

Further, an exhaust pipe 103 connected to an exhaust system for exhausting unnecessary gas in the chamber is connected to the processing chamber 102.

In the etching apparatus 101, the semiconductor substrate 1
A method of etching 0 will be briefly described. First, the semiconductor substrate 10 is loaded into the processing chamber 102, and
The inside is brought into an industrial vacuum state. Thereafter, each gas source 131
The gases controlled by the valves 135 to 135 are mixed in the gas supply unit 130, diffused by the upper electrode 111 through the pipe 141, and supplied into the processing chamber 102. For example, individual gas flows may be
140, and the flow rate of the mixed gas after mixing is controlled by the valve 142.

Next, while supplying high frequency power from the high frequency power supply 113 to the upper electrode 111,
2, a high frequency power is supplied to the upper electrode 111 to generate a plasma 151 of the mixed gas supplied into the processing chamber 102 between the upper electrode 111 and the lower electrode 121. Processing room 1
02 is regulated to a constant value by an exhaust system constituted by an exhaust device and a pressure regulating valve,
It is preferable that the pressure is set in a range from 27 mPa to 106 mPa.

It is preferable that the temperature of the semiconductor substrate 10 is controlled by the lower electrode 121 and set in a range of 30 ° C. or more and 110 ° C. or less.

An etchant supplied from the plasma 151 to the semiconductor substrate 10 etches an insulating film (not shown) formed on the semiconductor substrate 10 to form a connection hole.

Next, a method of forming a connection hole in an insulating film formed on a semiconductor substrate in a method of manufacturing a semiconductor device will be described with reference to a manufacturing process diagram of FIG.

As shown in FIG. 1A, a semiconductor substrate 1
On 0, a first insulating film 21 is formed. This first
A wiring portion 22 made of, for example, polysilicon is formed on the insulating film 21. The wiring portion 22 is formed of a barrier layer 23 containing at least titanium. On the first insulating film 21, a second insulating film 24 covering the wiring portion 22 including the barrier layer 23 is formed. Further, an etching mask 25 is formed on the second insulating film 24. The etching mask 25 has an opening 26 for forming a connection hole communicating with the wiring portion 22.

Next, as shown in FIG. 1B, the second insulating film 2 is formed using the etching mask 25 as a mask.
4 is etched to form a connection hole 27 communicating with the wiring portion 22 in the second insulating film 24. In this etching, the etching apparatus described with reference to FIG. 2 is used, and octafluorocyclobutane (C ₄ F ₈ ) is used as an etching gas.
And carbon monoxide (CO), oxygen (O ₂ ), and argon (A
r) is used. The supply flow rate of octafluorocyclobutane (C ₄ F ₈ ) is 15 cm ³ / min
At least 25 cm ³ / min. The partial pressure of octafluorocyclobutane (C ₄ F ₈ ) in the mixed gas is 1.33 Pa or more and 2.66 Pa or less. Also, octafluorocyclobutane (C
₄ F ₈₎ and the flow ratio of oxygen (O ₂₎ is 0.5 to 0.7
The following is assumed. The flow ratio of octafluorocyclobutane (C ₄ F ₈ ) to carbon monoxide (CO) in the mixed gas is 2 or more and 3 or less.

In the above etching gas, octafluorocyclobutane (C ₄ F ₈ ) was used, but octafluorocyclopentene (C ₅ F ₈ ) can be used instead of octafluorocyclobutane (C ₄ F ₈ ). The flow rates and flow ratios when octafluorocyclopentene (C ₅ F ₈ ) is used are all the same as those for octafluorocyclobutane (C ₄ F ₈ ).

As a result of the etching, the opening 2 of the mask 25 is formed.
The second insulating film 24 is etched along 6 to form a connection hole 27. The formation of the connection hole 27 is performed by the barrier layer 23.
It is required to satisfy both of the following conditions: In the case where connection holes having different opening areas are simultaneously opened, it is also required to process the connection hole 27 having a narrow opening and the connection hole (not shown) having a wide opening to the same depth. . In the above etching, these results were satisfied.

On the other hand, when the flow rate of octafluorocyclobutane (C ₄ F ₈ ) or octafluorocyclopentene (C ₅ F ₈ ) as an etchant is small, FIG.
As shown in (2), the connection hole 27 is formed so as to penetrate the barrier layer 23. This is because the amount of the polymer supplied from the etchant also decreases because the flow rate of the etchant is low, and the thickness of the polymer formed on the barrier layer 23 is thereby reduced. as a result,
The etching proceeds through the barrier layer 23. In such a state, it was confirmed that the contact resistance with the upper wiring (not shown) formed later increased, and as a result, the electric resistance increased.

As described in the above embodiment, octafluorocyclobutane (C ₄ F ₈ ) serving as an etchant
Alternatively, the etching rate can be sufficiently ensured by increasing the flow rate of octafluorocyclopentene (C ₅ F ₈ ) from the flow rate conventionally used. In addition, it is possible to suppress the etching of the barrier layer 23 that should not be etched.

Under the conventional etchant conditions, if etching of the barrier layer 23 is suppressed, it is difficult to etch deep connection holes. Therefore, as described above, the barrier layer 23 is formed by setting the partial pressure of octafluorocyclobutane (C ₄ F ₈ ) or octafluorocyclopentene (C ₅ F ₈ ) as an etchant to 1.3 mPa or more and 2.7 mPa or less. It is possible to form a deep connection hole while suppressing the etching of the substrate. In particular, in the processing of deep connection holes having an aspect ratio exceeding 3.8, the partial pressure of octafluorocyclobutane (C ₄ F ₈ ) or octafluorocyclopentene (C ₅ F ₈ ) is 1.7 m.
It is preferable to set it to Pa or more and 2.3 mPa or less.

On the other hand, when the partial pressure of octafluorocyclobutane (C ₄ F ₈ ) or octafluorocyclopentene (C ₅ F ₈ ) as the etchant is high, as shown in FIG. Since the reaction product is not sufficiently discharged, the reaction at the time of etching is stopped, and a phenomenon called etch stop occurs. As described above, when the connection hole 27 does not reach the barrier layer 23, the connection hole 27 is electrically insulated by the second insulating film 24 remaining on the barrier layer 23. In other words, since an electric circuit to be originally formed is not formed, circuit formation is not feasible and causes a failure.

FIG. 5 shows the relationship between the etch stop and the degree of penetration of the barrier layer observed when the flow rate of the etchant is constant, and the partial pressure of the etchant. As shown in FIG. 5, it is found that when the partial pressure of the etchant is too high, the penetration of the barrier layer increases, and when the partial pressure of the etchant is too low, the etch stop increases. According to this result, the partial pressure of the etchant (octafluorocyclobutane (C ₄ F ₈ ) or octafluorocyclopentene (C ₅ F ₈ )) is not less than 1.3 mPa and not more than 2.7 mP.
It can be seen that when the thickness is not more than a, preferably not less than 1.7 mPa and not more than 2.3 mPa, it becomes possible to prevent an etch stop and reduce the penetration of the barrier layer.

The above-mentioned phenomenon shows the same behavior at the ratio between the oxygen flow rate and the etchant flow rate. When the oxygen flow rate ratio is higher than 0.70, the barrier layer penetrates as described with reference to FIG. Conversely, if the oxygen flow ratio is lower than 0.50, an etch stop occurs as described with reference to FIG. In particular, the oxygen flow rate ratio should be 0.55 or more.
By setting the thickness to 65 or less, even a deep connection hole having an aspect ratio exceeding 3.8 can be processed without generating an etch stop. At that time, penetration of the barrier layer was not confirmed. Therefore, as described above, the flow ratio of octafluorocyclobutane (C ₄ F ₈ ) to oxygen (O ₂ ) in the mixed gas (etchant) is 0.5 or more and 0.7 or less, preferably 0.55 or more and 0 or less. .6
5 or less.

As described above, when carbon monoxide (CO) is added as a gas to be supplied, the flow ratio of carbon monoxide (CO) to the etchant should be 2.0 or more and 3.0 or more.
The shape of the connection hole can be favorably maintained by setting the value to be significantly lower than the conventional value of 35 or more.

On the other hand, when the flow ratio of carbon monoxide (CO) is 2.
If it is lower than 0, as shown in FIG. 6, the connection hole 27 formed in the second insulating film 24 has a so-called bowing shape in which an intermediate portion is expanded. This is because the amount of carbon supplied from carbon monoxide (CO) is insufficient because the flow ratio of carbon monoxide (CO) is too low, and the middle of the connection hole 27 is laterally etched and spread. When such a bowing shape occurs, abnormal formation of the tungsten plug formed inside the connection hole 27 occurs,
Problems such as an increase in electrical resistance occur.

On the other hand, when the carbon monoxide (CO) flow ratio is 3.0
If it is too high, as shown in FIG.
The shape of 7 is a so-called necking shape. this is,
If the carbon monoxide (CO) flow ratio is too high, the amount of carbon supplied from carbon monoxide (CO) becomes excessive, and the connection holes 27
The necking shape is such that the upper part is narrowed. When necking occurs, the bottom area of the connection hole 27 is significantly reduced, and a problem such as an increase in electric resistance occurs.

FIG. 8 shows the relationship between the degree of occurrence of bowing and necking and the flow rate ratio of carbon monoxide (CO). As shown in FIG. 8, when the carbon monoxide (CO) flow ratio is too low, the bowing increases, and when the carbon monoxide (CO) flow ratio is too high, necking increases. As described above, it is particularly preferable that the flow rate ratio of carbon monoxide (CO) be in the range of 2.3 or more and 2.7 or less in order to maintain good contact resistance.

The flow rates of the various gases described in this specification are those at 25 ° C. and 101.325 kPa.

[0033]

As described above, according to the method of manufacturing a semiconductor device of the present invention, the supply flow rate of octafluorocyclobutane (C ₄ F ₈ ) or octafluorocyclopentene (C ₅ F ₈ ) is 15 cm ³ / min. More than 25
Since the etching rate is not more than cm ³ / min, a sufficient etching rate can be ensured, and furthermore, the etching of the barrier layer which should not be etched can be suppressed. Therefore, it is possible to process a connection hole having a large aspect ratio at a high speed. At the same time, a connection hole having a wide opening existing in the same substrate is formed. In addition, connection can be formed while the shape of the connection hole is well maintained. The connection hole can be formed without shaving the titanium nitride film or the silicon nitride film formed on the wiring. As a result, good electrical characteristics of the connection hole can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing an example of an embodiment according to a method for manufacturing a semiconductor device of the present invention.

FIG. 2 is a schematic configuration diagram of an etching apparatus.

FIG. 3 is a schematic configuration sectional view showing an etching state of a connection hole when a flow rate of an etchant is small.

FIG. 4 is a schematic cross-sectional view showing an etching state of a connection hole when a partial pressure of an etchant is high.

FIG. 5 is a diagram showing the relationship between the etch stop and the degree of penetration of the barrier layer observed when the flow rate of the etchant is constant, and the partial pressure of the etchant.

FIG. 6 is a schematic configuration sectional view showing an etching state of a connection hole when a flow ratio of carbon monoxide is too lower than 2.0.

FIG. 7 is a schematic cross-sectional view showing an etching state of a connection hole when a flow ratio of carbon monoxide is too high than 3.0.

FIG. 8 is a graph showing the relationship between the degree of occurrence of bowing and necking and the flow rate ratio of carbon monoxide.

[Explanation of symbols]

 10: substrate, 24: second insulating film

Continued on the front page (72) Inventor Wataru Fudo 4-1-1, Kamidadanaka, Nakahara-ku, Kawasaki-shi, Kanagawa F-term in Fujitsu Limited (Reference) 4M104 DD08 DD15 HH15 5F004 AA05 BA04 BB28 CA02 CA04 DA00 DA23 DA26 DA30 DB00 EA23 EB01 5F033 KK04 KK18 MM01 MM05 MM13 QQ09 QQ12 QQ15 QQ37 WW05 WW06 XX04

Claims (4)

[Claims] 1. An octafluorocyclobutane (C)
₄ F ₈ ) or octafluorocyclopentene (C ₅
F ₈ ) and a method for manufacturing a semiconductor device in which an insulating film formed on a substrate is processed using a mixed gas of carbon monoxide (CO), oxygen (O ₂ ), and argon (Ar) as an etching gas. ^{3. The} method of manufacturing a semiconductor device according to claim 1, wherein a supply flow rate of the octafluorocyclobutane (C ₄ F ₈ ) or the octafluorocyclopentene (C ₅ F ₈ ) is 15 cm ³ / min or more and 25 cm ³ / min or less. 2. The octafluoro in the gas mixture.
Rocyclobutane (C _FourF₈) Or the octafluoro
Locyclopentene (C_FiveF₈) Is less than 1.33Pa
2. The pressure is set to 2.66 Pa or less.
Manufacturing method of the semiconductor device described above. 3. The octafluor in the mixed gas.
Rocyclobutane (C _FourF₈) Or the octafluoro
Locyclopentene (C_FiveF₈) And oxygen (O_Two) And flow rate
Claims wherein the ratio is between 0.5 and 0.7
3. The method for manufacturing a semiconductor device according to claim 1 or 2. 4. The octafluor in the gas mixture.
Rocyclobutane (C _FourF₈) Or the octafluoro
Locyclopentene (C_FiveF₈) And carbon monoxide (CO)
Wherein the flow rate ratio is between 2 and 3 inclusive.
1. Manufacture of the semiconductor device according to claim 2 or claim 3.
Method.