JP3258240B2 - Etching method - 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 etching a semiconductor substrate, and more particularly to an etching method suitable for controlling a processing shape on a side surface of a wiring material used in an LSI or the like, in particular, a multilayer or single-layer Al wiring. .

[0002]

2. Description of the Related Art Most Al wirings in LSIs have a three-layer structure of a TiN cap layer / Al--Cu alloy / TiN barrier layer. BCl ₃ / C
Dry etching using l ₂ gas is widely used. In the etching of the BCl ₃ / Cl ₂ system, since the etching rate of the Al—Cu alloy is higher than the etching rate of TiN, as shown in the cross-sectional view of the conventional multilayer Al wiring in FIG. Side etching 305 occurs on the substrate, and A
There is a problem that a notch 306 is generated in the l-Cu alloy layer 303. In FIG. 3, reference numeral 302 denotes a TiN barrier layer, 301 denotes an insulating film, and 300 denotes a semiconductor substrate. In order to realize a good processed shape, it is necessary to etch the Al wiring while controlling the formation of the sidewall protective film. As a countermeasure, for example, Journal of
Vacuum Science & Technology
gy, Vol. As described in 1232-1237, N ₂ is added to a BCl ₃ / Cl ₂ based gas to reduce the notch 306 and to reduce the Al—Cu alloy layer 3.
03 anisotropic processing was achieved. The sidewall protective film formed by this means is formed by the reaction between B from BCl ₃ and N in the TiN layer.
Since it contains an N compound, it is a sidewall protective film that is more effective in shape control than conventional BCl ₃ / Cl ₂ etching.

Conventionally, as disclosed in JP-A-60-169140, plasma etching of aluminum and aluminum alloys under reduced pressure has been proposed.
A high frequency power of 13.56 MHz is applied to the electrodes on the wafer installation side of the pair of electrodes, and a CH ₄ gas is added to the BCl ₃ + Cl ₂ gas to achieve high-speed and anisotropic etching with a low high frequency power, There is one that suppresses damage to the resist.

[0004]

The above-mentioned BCl ₃ / C
In the method of adding N ₂ to the l ₂ -based etching gas, the notch 306 is reduced by efficiently forming the sidewall protective film containing the BN compound. However, since the sidewall protective film containing the BN compound has a chemically strong bond, there is a problem that it is difficult to remove the sidewall protective film by an ashing process and a solution process subsequent to the etching. In addition, since the formation and deposition reaction of the BN compound occurs on the inner wall of the etching chamber,
Foreign matter is easily generated in the etching apparatus, which is a problem when applying to mass production of LSI. Therefore, it is necessary to provide a means for forming a sidewall protective film which is strong and is easily removed after etching instead of the BN compound.

On the other hand, in plasma etching, the photoresist mask is also shaved by the plasma, and the shaved photoresist adheres to the side surface to be etched and functions as a side wall protective film. However, in recent years, in the case where the photoresist mask is small relative to the etching area, such as ASIC or logic, for example, 30% or less of the wafer area, in other words, the area of the portion to be etched is 70% or more, the plasma is generated during etching. The absolute amount of the photoresist to be removed is small, the function as the sidewall protective film is small, and it is necessary to separately form the sidewall protective film. The process described in Japanese Patent Application Laid-Open No. Sho 60-169140 discloses only achieving high-speed and anisotropic etching with low high-frequency power and suppressing damage to a resist. No action is disclosed.

An object of the present invention is to provide an etching method capable of obtaining a reliable etching shape in a sample in which the area of a portion to be etched is larger than the area of a resist mask. Another object of the present invention is to provide an etching method capable of performing processing while forming a sidewall protective film which is easily removed after etching and whose shape can be easily controlled during etching.

[0007]

An object of the present invention is to provide a multi-layer or single-layer Al wiring formed on a semiconductor substrate by using BCl ₃
In a method of etching using + Cl ₂ gas plasma, at least one gas selected from C _x H _y Cl _z (x, y, z = 0 to 8) gas, and at least one gas selected from the group consisting of:
An Ar gas in an amount greater than the amount of one or more gases is added to the BCl ₃ + Cl ₂ gas to form an etching gas, and etching is performed using the plasma of the etching gas. Matching etching shape
This is achieved by setting the flow rate ratio accordingly . The above-described object is a multi-layer or single-layer Al wirings formed on a semiconductor substrate, a method of etching using a plasma of BCl ₃ + Cl ₂ gas, C _x H _y Cl _z
(x, y, z = 0 to 8) at least one or more gases selected from the gases and the amount of the at least one or more gases
The large amount of Ar gas, was added to each the BCl ₃ + Cl ₂ gas as an etching gas, with a plasma of the etching gas, the addition of the Ar gas, et
The flow rate is set in accordance with the shape of the etching, and the wall temperature of the etching chamber in which the plasma is formed is set to 80 to 2
This is achieved by controlling and etching at a predetermined temperature in the range of 50 ° C. Similarly, the object is to prepare a sample in which the material to be etched is an Al-based wiring film by using BCl ₃ + Cl ₂
In a method of performing etching by plasma of an etching gas obtained by adding a CH ₄ gas to a gas, an etching gas is obtained by adding an Ar gas in an amount larger than the amount of the CH ₄ gas to the etching gas. Etching using the plasma of the application gas and adding the Ar gas
This is achieved by setting the flow rate ratio in accordance with the etching shape . Further, the object is to prepare a sample whose material to be etched is an Al-based wiring film by using BCl ₃ + Cl _2.
In the method of performing an etching process using an etching gas plasma obtained by adding a CH ₄ gas to a gas, when the area of a portion to be etched of the sample is larger than the area of a resist mask, the amount of the CH ₄ gas is included in the etching gas. A larger amount of Ar gas is added to form an etching gas, and etching is performed using the plasma of the etching gas.
This is achieved by setting the flow rate ratio accordingly .
Still another object of the present invention is to provide a method for etching a sample whose material to be etched is an Al-based wiring film by using a plasma of an etching gas obtained by adding a CH ₄ gas to a BCl ₃ + Cl ₂ gas. After plasma cleaning the chamber, an etching gas is added to the etching gas by adding an Ar gas in an amount larger than the amount of the CH ₄ gas, and etching is performed using the plasma of the etching gas.
This is achieved by setting the flow ratio according to the etching shape .

[0008]

DETAILED DESCRIPTION OF THE INVENTION The present invention provides single etching chamber of wafer etching apparatus O ₂ plasma chestnut - after removing the training to organics, BCl controls wall temperature of the chamber to a predetermined temperature of 80 to 250 ° C. _The multilayer Al wiring is plasma-etched with a mixed gas of ₃ , Cl ₂ , CH ₄ and Ar using an organic resist film mask. The gas mass flow ratio at that time is such that BCl ₃ , CH ₄ and Ar are 5 to 50, 1 to 20, and 50 to 500, respectively, with respect to Cl ₂ : 100. The O ₂ plasma cleaning may be performed for each of a plurality of continuous processes or for each wafer process. Thereby, C
Since the organic component dissociated from H ₄ efficiently forms the sidewall protective film, side etching and notch can be suppressed, and etching of a multilayer Al wiring having a good processed shape becomes possible. Further, by adding Ar, the thickness of the sidewall protective film can be controlled by the sputtering effect,
The controllability of the processing shape can be further improved. The sidewall protective film formed by the above method can be easily removed by a usual post-process. Further, the addition of CH ₄ does not affect the maintainability of the etching apparatus. Normal,
When etching to which an organic gas such as CH ₄ is added is applied to mass production, the processed shape changes over time. However, in the present invention, etching is performed by removing organic substances in the chamber by periodic O ₂ cleaning and controlling the chamber wall temperature. Atmosphere stability and reproducibility have been improved to enable application to mass production.

An embodiment of the present invention will be described below with reference to a sample sectional view shown in FIG. 1 and a schematic view of an etching apparatus shown in FIG. First, as shown in FIG.
On the insulating film 101, the TiN barrier layer 102,
A Cu alloy layer 103 and a TiN cap layer 104 are laminated,
Further, a sample having a resist film 105 formed in a desired pattern on the TiN cap layer 104 is carried into a sample exchange chamber of an etching apparatus. In the etching apparatus, the microwave generated by the magnetron 200 passes through the waveguide 201 and the introduction window 202 as shown in FIG.
3 and the magnetic field control coil 2 in the etching chamber 203.
The magnetic field and the microwave electric field formed by 04 cause electron cyclotron resonance to generate high density plasma.
A high-frequency power source 206 is connected to the sample holder 205 so that an RF bias can be applied independently of plasma generation. Before the sample is carried into the etching chamber 203, an O ₂ plasma cleaning process is performed to remove organic substances in the etching chamber. Cleaning condition is O ₂
Flow rate: 100sccm, total gas pressure: 2Pa, microwave output:
800W.

After cleaning, the temperature of the inner wall of the etching chamber is set and controlled at 100 ° C.
Transport to 03. The sample was formed by using the patterned resist film 105 as a mask to form the TiN cap layer 104, Al-
The Cu alloy layer 103 and the TiN barrier layer 102 are sequentially etched. As a main etching condition at this time, in the case (1), the gas flow rate is set to BCl ₃ : 20 scc.
m, Cl ₂ : 80 sccm, CH ₄ : 4 sccm, total gas pressure: 2P
a, microwave power: 800 W, RF power: 60 W, and substrate temperature: 40 ° C., the results shown in FIG. 1B were obtained. In case (2), the gas flow rate is set to BCl ₃ :
_{20sccm, Cl 2: 80sccm, CH} 4: 4scc
When m and Ar were 96 sccm and the total gas pressure was 3 Pa, the result shown in FIG. 1C was obtained. Here, the other etching conditions are the same as in the case shown in FIG. Also,
The control of each gas flow rate was performed using the flow rate controller 207 by mass flow control. Note that overetching was continued for 15 seconds after the etching of the TiN barrier layer 102 determined using the plasma emission monitor was completed.

In the case of the case (1), the cross-sectional shape of the sample after the above-mentioned etching treatment is such that a side wall protective film is formed as shown in FIG. 1 (b), and the etching shape can be controlled. In this case, the side wall protective film is formed by the organic components of C and CH contained in the plasma by the CH ₄ gas, and the components are the same as those of the resist mask made of an organic substance. Therefore, the side wall protective film can be removed by the same process as resist ashing.
Note that, in this case, the side wall protective film formed by the CH ₄ gas was too thick, so that the taper formed a forward taper (referred to as a taper that spread downward as shown in the figure). That is, the organic components of C and CH contained in the plasma adhere as a side wall protective film, and because of a large amount of the organic components, they serve as a mask and spread in a tapered shape with etching. Note that the thickness of the side wall protective film can be controlled by changing the amount of CH ₄ gas, and vertical etching can be performed by optimizing the thickness. By using this process, for example, AS
This is effective when the area of the portion to be etched is larger than the area of the resist mask patterned like an IC or a logic, especially when the area ratio between the resist mask and the portion to be etched is 3: 7. is there. That is, when the resist mask area is 30% or more, for example, 40%, a part of the resist mask is also sputter-etched by the action of ions in the plasma during plasma etching, and a part of the sputter-etched resist is formed. Adheres to the side wall surface of the etching and slightly acts as a side wall protective film. However, if the resist mask area is 30% or less, the amount of resist to be sputter-etched is reduced and the effect is almost eliminated. As described above, in a sample having a small resist mask area, the same organic components of C and CH as in the resist mask using CH ₄ gas can be supplied into the plasma, so that the sidewall protective film can be effectively formed. it can. Further, since vertical etching can be performed while minimizing the side wall protective film, as shown in FIG. 3A, the line width is 0.5 μm or less, the pattern width is 0.5 μm or less, and the depth is 0.5 μm. It is also possible to etch the wiring film having the above-mentioned laminated structure having a fine shape. As a result, an insulating film is formed on the portion etched into the fine shape, and FIG.
A semiconductor device configured as shown in (b) can be manufactured.

In case (2), as shown in FIG. 1 (c), Ar gas is added to the process of case (1), and vertical etching is performed. That is,
By adding Ar gas, the thickness of the side wall protective film is controlled by the sputtering property of Ar ions during etching, and Ti
N cap layer 104, Al—Cu alloy layer 103, TiN
It is considered that each side surface of the barrier layer 102 was processed vertically. Also in this case, the etching side surface is covered by a by-product during etching, that is, the sidewall protective film 106 made of an organic substance such as C and CH. Therefore, the sidewall protective film 106 can be easily removed together with the removal of the resist mask by post-processing after the etching process, for example, resist ashing. According to the process of the case (2), the thickness of the side wall protective film can be more easily controlled by adding Ar gas than in the case (1). That is, in case (1), the amount of CH ₄ gas is originally small, and it is difficult to adjust the amount. On the other hand, in the case (2), since the amount of Ar gas is large, it is possible to easily set an optimum flow ratio in accordance with the etching shape, thereby easily obtaining a desired etching shape. . Therefore, a sample having a small resist mask, for example, a sample having a small area (30% of the wafer area)
Below) or a thin resist mask (1 μm
This method is suitable for etching of a material having a large selectivity with respect to a resist and a resist that is not so much removed.

According to this embodiment, the TiN cap layer 104 is used.
Etching of a multilayer Al wiring having a good shape can be performed without generating a notch in the Al-Cu alloy layer 103 immediately below.
Further, the removal of the resist film 105 and the side wall protective film 106 in the post-etching step is easy. Further, even if 25 samples are continuously etched after the O ₂ cleaning process, the processed shape hardly changes. That is, by performing the O ₂ cleaning process periodically, even when applied to mass production, there is no change over time in the processing shape of the multilayer Al wiring, and there is no hindrance to the maintainability of the device.
Here, the effect has been confirmed for the normal continuous processing of 25 sheets in one lot.
Continuous processing of more than one sheet is also possible. Needless to say, continuous processing of 25 or less sheets, for example, 1, 5, and 10 sheets is effective.

In this embodiment, the temperature of the inner wall of the etching chamber is set and controlled to 100 ° C., but even if the temperature is controlled within the range of 80 to 250 ° C., the flow rate ratio of BCl ₃ / Cl ₂ / CH ₄ / Ar Can be adjusted to obtain the same effect.
A guide for a suitable mass flow ratio is B: Cl ₂ : 100.
Cl ₃ , CH ₄ and Ar are 5 to 50, 1 to 20, 50, respectively.
５００500. In this embodiment, the case where CH ₄ and Ar gas are added to BCl ₃ / Cl ₂ is described. Other CxHyClz (x, y, z = 0 to 8), CxHyB
at least one of rz (x, y, z = 0 to 8) gas
The same effect can be expected by using a mixed gas of one or more and at least one of Ar, Xe, and Kr.
As a result of the experiment, it was found that addition of CH ₄ and Ar gas was effective. In this embodiment, BCl ₃ / Cl ₂ is used as an etching gas, but it is also effective to use another chlorine-based gas such as SiCl ₄ or CCl ₄ .

In this embodiment, the TiN / Al-Cu alloy layer / TiN laminated film is etched.
The upper and lower films of the u alloy layer may be Ti / TiN films, TiW films, W films, or the like. Further, the same effect can be obtained not only by the laminated film but also by an Al single layer film (a single layer film of Al or Al alloy). Although the present embodiment has been described using an ECR type etching apparatus, other plasma etching apparatuses, for example, ICP (Inductively Coupled Plasma)
The same effect can be obtained by using an etching apparatus.

[0016]

According to the present invention, there is an effect that a reliable etching shape can be obtained in a sample in which the area of the portion to be etched is larger than the area of the resist mask. In addition, there is an effect that the etching process can be performed while forming a sidewall protective film which is easily removed after etching and whose shape can be easily controlled at the time of etching.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a sample according to an embodiment of the present invention.

FIG. 2 is a schematic diagram of an etching apparatus which is an embodiment of an apparatus for implementing the present invention.

FIG. 3 is a cross-sectional view illustrating an example of a semiconductor device manufactured by applying the present invention.

FIG. 4 is a diagram showing a cross-sectional shape of a conventional Al wiring.

[Explanation of symbols]

100 semiconductor substrate, 101 insulating film, 102 TiN
Barrier layer, 103 ... Al-Cu alloy layer, 104 ... TiN
Cap layer, 105: resist film, 106: side wall protective film, 107: insulating film, 200: magnetron, 201 ...
Waveguide, 202: introduction window, 203: etching chamber, 20
4: magnetic field control coil, 205: sample holder, 206: high frequency power supply, 207: mass flow controller.

────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-7-273192 (JP, A) JP-A-5-102097 (JP, A) JP-A-7-58079 (JP, A) JP-A-7-273 106312 (JP, A) JP-A-5-343366 (JP, A) JP-A-6-283524 (JP, A) JP-A-52-131939 (JP, A) JP-A-6-302565 (JP, A) JP-A-7-230996 (JP, A) JP-A-8-111401 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 21/3065 C23F 4/00 H01L 21/3213

Claims (5)

(57) [Claims] 1. A method of etching a multilayer or single-layer Al wiring formed on a semiconductor substrate by using a plasma of BCl ₃ + Cl ₂ gas, wherein C _x H _y Cl _z (x, y, z = 0 to 0) 8) At least one or more gases selected from the gases and an Ar gas in an amount larger than the amount of the at least one or more gases are mixed with the BCl ₃ gas , respectively.
+ Cl ₂ gas to be used as an etching gas, and etching using this etching gas plasma
Then, the addition of the Ar gas matches the etching shape.
An etching method comprising setting a flow rate ratio . 2. A method for etching a multi-layer or single-layer Al wiring formed on a semiconductor substrate by using plasma of BCl ₃ + Cl ₂ gas, wherein C _x H _y Cl _z (x, y, z = 0 to 0) 8) At least one or more gases selected from the gases and an Ar gas in an amount larger than the amount of the at least one or more gases are mixed with the BCl ₃ gas , respectively.
+ Cl ₂ was added to the gas as the etching gas, with a plasma of the etching gas, the Ar
By adding gas, the flow rate ratio according to the etching shape
After setting, the wall temperature of the etching chamber where the plasma is formed is set to 8
An etching method, characterized in that etching is performed at a predetermined temperature within a range of 0 to 250 ° C. 3. A method for etching a sample whose material to be etched is an Al-based wiring film by plasma of an etching gas obtained by adding a CH ₄ gas to a BCl ₃ + Cl ₂ gas, wherein the etching gas includes the CH ₄ gas. Quantity greater than the quantity of
Is added as an etching gas, and etching is performed using the plasma of the etching gas.
Then, the addition of the Ar gas matches the etching shape.
An etching method comprising setting a flow rate ratio . 4. A method for etching a sample whose material to be etched is an Al-based wiring film by plasma of an etching gas obtained by adding CH ₄ gas to BCl ₃ + Cl ₂ gas, wherein the area of the etched portion of the sample is When the sample is larger than the area of the resist mask, an etching gas is obtained by adding an Ar gas in an amount larger than the amount of the CH ₄ gas to the etching gas, and etching is performed using the plasma of the etching gas.
Then, the addition of the Ar gas matches the etching shape.
An etching method comprising setting a flow rate ratio . 5. A method of etching a sample whose material to be etched is an Al-based wiring film using plasma of an etching gas obtained by adding a CH ₄ gas to a BCl ₃ + Cl ₂ gas, wherein an etching chamber in which the plasma is formed is formed. after plasma cleaning, in the etching gas, greater than the amount of the CH ₄ gas amount
Is added as an etching gas, and etching is performed using the plasma of the etching gas.
Then, the addition of the Ar gas matches the etching shape.
An etching method comprising setting a flow rate ratio .