JPH11345802A - Dry etching method and method for cleaning inside of apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a dry etching method and a method for cleaning inside of apparatus capable of stabilizing a process. SOLUTION: A Cr-Si-N thin film 3 to be a thin-film resistor is formed on a semiconductor substrate 1 and a TiW thin film 4 is formed as a barrier metal thereon. A CF4 -O2 -N2 system gas is used as an etchant, CDE(chemical dry etcher) is used to dry-etch the TiW thin film 4 under the condition that CF4 -O2 -N2 gas flow is at 40-80-280 sccm, respectively, and microwave power is at 600 W. The Cr-Si-N thin film 3 is then dry-etched.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dry etching method for processing a high melting point metal containing titanium (Ti) such as a Ti-W type high melting point metal and a method for cleaning the inside of an apparatus.

[0002]

2. Description of the Related Art For example, there is known a semiconductor device using a CrSi-based thin film as a resistor and using TiW as a barrier metal thereon as disclosed in Japanese Patent Application Laid-Open No. H10-56007. In this case, after depositing a CrSi-based thin film and a TiW thin film in this order on a semiconductor substrate,
The W thin film and the CrSi-based thin film are patterned into desired shapes. At this time, with the demand for miniaturization and higher precision, T
The need for iW dry etching is increasing.
When a TiW-based refractory metal is etched by dry etching, Ti is generally mixed with a gas (C) containing chlorine (Cl).
1 _2, etc.), W comprises fluorine (F) gas (CF _4, etc.)
It is known that etching can be performed by using a mixed gas of chlorine-based gas and fluorine-based gas as an etching gas. However, chlorine-based gas is highly corrosive and toxic, and causes environmental pollution and handling / management. It is not preferable in terms of use.

In addition, in the case of etching with a simple fluorine-based gas (in general, a CF ₄ —O ₂ system is used), there is a problem that Ti is not stably etched and the variation in etching rate becomes large.

[0004] Etching of TiW is performed at room temperature.
Etching hardly proceeds with CF ₄ —O ₂ based gas. However, since the temperature dependency is large, the etching proceeds when the substrate is heated to increase the temperature. However,
The temperature of the product generated by the etching during the movement in the reaction chamber decreases, solidifies and adheres to the wall surface of the reaction chamber, and a problem occurs that the etching rate decreases with an increase in the cumulative number of etching processes. In particular, dry etching of CrSi is greatly affected (1/10).
The following was found from the investigations of the inventors. Therefore, when dry etching is performed continuously on TiW and CrSi using the same apparatus, it is necessary to remove the deposit every time a predetermined number of sheets are processed. Therefore, the reaction chamber has to be released to the atmosphere and wet cleaning has to be performed with a solution containing alcohol or hydrogen peroxide. In addition, it is considered that the above-mentioned deposits on the wall surface of the reaction chamber function to weaken the activity of the reactive species, and the etching rate decreases with an increase in the number of cumulative etching treatments.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and an object of the present invention is to provide a dry etching method and a method for cleaning the inside of an apparatus, which can perform a stable process. is there.

[0006]

According to the dry etching method of the present invention, when a refractory metal containing titanium is processed by dry etching, a CF ₄ —O ₂ —N ₂ system is used as an etching gas. It is characterized by using gas. Therefore, stable etching can be performed by using CF ₄ —O ₂ —N ₂ -based gas.

The dry etching according to claim 2
The method comprises refractory gold containing titanium and tungsten
When processing metal by dry etching,
CF_Four-O_Two-N_TwoIt is noted that
It is a sign. Therefore, CF _Four-O_Two-N_TwoUse system gas
As a result, stable etching is performed.

[0008] According to a third aspect of the present invention, there is provided a method for cleaning the inside of an apparatus.
At the time of cleaning the inside of a device for treating a titanium-containing high melting point metal, a CF ₄ —O ₂ —N ₂ -based gas is used as a cleaning gas to remove the titanium-containing high melting point metal adhered to the inside of the device. It is characterized by doing. Therefore,
By using the CF ₄ —O ₂ —N ₂ -based gas, stable cleaning of the inside of the apparatus is performed.

Here, assuming that the processing apparatus performs dry etching continuously on a CrSi-based thin film on a semiconductor substrate and on a refractory metal containing titanium thereon, This is practically preferable.

Further, it is practically preferable to apply the etching of the refractory metal containing titanium while heating the semiconductor substrate, as described in claim 5.

[0011] The method for cleaning the inside of the apparatus according to claim 6 is as follows.
Treats refractory metals containing titanium and tungsten
When cleaning the inside of the equipment,
F_Four-O_Two-N_TwoAttached inside the device using system gas
To remove refractory metals containing tan and tungsten
It is characterized by that. Therefore, CF_Four-O_Two-N _Two
By using the system gas, stable cleaning of the inside of the equipment can be achieved.
Done.

Here, as in claim 7, the processing apparatus performs dry etching continuously on a CrSi-based thin film on a semiconductor substrate and a refractory metal containing titanium and tungsten thereon. Then, it becomes practically preferable.

It is practically preferable to apply the etching of the high melting point metal containing titanium and tungsten to a device which heats a semiconductor substrate, as described in claim 8.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view of the semiconductor device according to the present embodiment. This semiconductor device includes a bipolar transistor and a thin-film resistor 3 made of a CrSi-based thin film.

That is, the semiconductor substrate (silicon substrate) 1
An insulating film 2 is formed thereon, and a Cr—Si—N thin film 3 as a thin film resistor is disposed on the insulating film 2. Further, aluminum wirings 7a and 7b are connected to both right and left ends in the drawing of the Cr-Si-N thin film 3 via TiW thin films 4a and 4b as barrier metals. That is, Cr
On the -Si-N thin film 3, TiW thin films 4a and 4b, which are high melting point metals containing Ti, are provided, and aluminum wirings 7a and 7b are provided thereon.

Next, a method of manufacturing the semiconductor device thus configured will be described with reference to FIGS. First, as shown in FIG. 2, a semiconductor element (bipolar transistor) is formed on a semiconductor substrate (silicon substrate) 1 by an ordinary method. Thereafter, an oxide film (BPSG or the like) 2 as an insulating film is formed on the surface of the semiconductor substrate 1.

Further, as shown in FIG. 3, the thickness of the oxide film 2 is increased by a sputtering method in an atmosphere containing N ₂ gas (such as Ar-N ₂ ) using a target made of Cr—Si. A Cr-Si-N thin film 3 of about 15 nm is formed.

Thereafter, as shown in FIG.
A TiW thin film 4 having a thickness of about 150 nm is formed on the N thin film 3 by a sputtering method in a Ar gas using a Ti-W (10 wt% Ti) target.

Further, as shown in FIG. 5, a desired photoresist pattern 5 is formed on the TiW thin film 4 by using a photolithography technique. Using CDE (Chemical Dry Etcher), CF ₄ —O ₂ —N ₂ -based gas is used as an etching gas, CF ₄ —O ₂ —N ₂ gas flow rate is 40-80-280 sccm, microwave power 600 W, The TiW thin film 4 is dry-etched under the condition of no substrate heating.

[0020] Subsequently, using the same CDE (chemical dry etcher), as shown in FIG. 6, CF ₄ -O
_The Cr—Si—N thin film 3 is dry-etched using a _two- system gas. Then, the photoresist 5 is removed by O ₂ plasma ashing and organic cleaning.

Next, as shown in FIG. 7, a contact hole 6 is patterned in the insulating film 2 on the semiconductor substrate 1.
Further, an aluminum wiring 7 including aluminum wirings 7a and 7b is patterned thereon using a resist 8.

Further, as shown in FIG. 8, the Ti on the Cr—Si—N thin film 3 patterned using the resist 8 is formed.
Unnecessary portions of the W thin film 4 are removed by wet etching to complete the resistance pattern of the Cr—Si—N thin film 3.
Here, the etching solution includes an etching solution containing hydrogen peroxide (typically, 31% hydrogen peroxide: 29% by volume ratio).
Aqueous ammonia solution = 100: 5) is used.

Thereafter, as shown in FIG. 1, an interlayer insulating film 9, a via hole 10, a second-layer aluminum wiring pattern 11, and a protective film 12 are sequentially formed as shown in FIG.
Hereinafter, when a CF ₄ —O ₂ —N ₂ -based gas is used as an etching gas during dry etching of the TiW thin film 4 (gas flow rate CF ₄ —O ₂ —N ₂ = 40-80-280 s)
Various experiments were conducted for the effect of the case of ccm) and will be described.

CDE (Chemical Dry Etching)
Since the etching proceeds mainly by a chemical reaction due to radicals, when the object to be etched is composed of a plurality of non-volatile elements such as TiW, a gas system for etching each element and a composition ratio are used. It is desirable to set a gas flow ratio that meets the above. W is, CF ₄ gas only, or, a sufficient etching rate can be obtained by CF ₄ -O ₂ system gas, Ti is, CF ₄ also only CF ₄ gas
Not sufficient etching rate can be obtained even by -O ₂ based gas.
This is probably because the vapor pressure of TiF ₄ or TiO, which is considered to be a reaction product, is too low.

That is, as shown in Tables 1 and 2, CF_Four−
O_TwoSystem and CF_Four-N_TwoChange the mixing ratio in the system gas
The TiW thin film 120 seconds after the start of etching
Change in sheet resistance ρs (%) of film and etching
When measuring the progress, CF _Four-O_TwoSystem, CF_Four-N_Two
In a system, etching does not proceed even if the gas mixture ratio is changed.
I understood.

[0026]

[Table 1]

[0027]

[Table 2] However, CF ₄ was introduced with N ₂ CF ₄ -O ₂ system gas
With -O ₂ -N ₂ system gas, so that the etching reaction proceeds. This is presumed that the reaction product becomes a compound containing N, and therefore, the vapor pressure becomes relatively high and the etching reaction proceeds.

The results of an experiment conducted to confirm this are shown in FIG.
It is shown in FIG. This measurement uses a chemical dry etching system.
And CF_FourFlow rate of 40 sccm and power of 60
0W, without heating the substrate, CF_FourGas flow
Fixed, O_TwoAnd N_TwoEdge when changing the flow ratio
Sheet resistance ρs of the TiW thin film 3 minutes after the start of
The amount of change, emission color, and progress of etching are examined.
is there. Specifically, O _TwoAnd N_TwoOf the flow rate of O_Two/ N
_Two= 360sccm / 0sccm, 220sccm / 1
40 sccm, 180 sccm / 180 sccm, 14
0sccm / 220sccm, 80sccm / 280s
ccm, 40sccm / 320sccm, 0sccm /
There are seven types of 360 sccm.

The equipment used is CDE manufactured by Shibaura Seisakusho
-7 (chemical dry etching apparatus), which performs etching without heating. FIG.
Therefore, when the flow rate of CF ₄ gas is fixed and the flow rate ratio of O ₂ and N ₂ is changed, etching can be continuously performed without stopping halfway. O ₂ / N ₂ = 80 sccm / 280 s
ccm. That is, O ₂ / N ₂ = 360 sccm
Etching stops at / 0 sccm to 140 sccm / 220 sccm, and O ₂ / N ₂ = 40 sccm / 320
At sccm, the etching stops halfway, and O ₂ / N ₂ =
At 0 sccm / 360 sccm, etching did not proceed. Further, O ₂ / N ₂ = 80 sccm / 280 s
The rate of change of the sheet resistance ρs in ccm is large, and stable etching is possible. Therefore, in the above-described manufacturing process, under these conditions (CF ₄ —O ₂ —N ₂ gas flow rate is 40-80-280 sccm, microwave power 600
W, no heating of the substrate).

Observation of the emission color at the time of dry etching reveals that yellow emission, which is thought to be caused by W etching on the O ₂ rich side, is purple, which is thought to be caused by Ti etching on the N ₂ rich side. Light emission appears, and the above-mentioned optimal mixing ratio (O ₂ / N ₂ = 80 sccm / 280 sccm)
In the vicinity, emission of both neutral colors (blue to green) was observed.

It can be inferred from the result of observation of the emission color at the time of etching derived from the metal element that the etching reaction proceeds when N ₂ is introduced as described above (the reaction color of the W element is yellow, and the reaction color of the Ti element is yellow). Is purple).

From the above, it can be estimated as follows as the etching mechanism of TiW and the function of O ₂ and N ₂ . O ₂ assists in the etching of W, N ₂ assists in the etching of Ti, and when the etching rate of W and Ti reaches a balanced gas ratio, the overall etching rate is maximized and stable etching is possible. Becomes

Since the temperature dependence of the etching rate of each constituent element is not always the same, depending on the temperature, N ₂ /
The optimum value of the O ₂ gas flow ratio varies. As described above, the present embodiment has the following features.

When the TiW thin film 4 (high melting point metal containing titanium) is processed by dry etching, a CF ₄ —O ₂ —N ₂ -based gas is used as an etching gas.
Stable etching becomes possible.

That is, in dry etching of TiW using a CF ₄ -based gas, a problem that the etched substance is apt to be re-deposited or the etching is stopped halfway easily occurs, but this can be avoided. Also,
As an etching gas, a chlorine-based gas, which is a corrosive gas, is not used, and it is easy to handle without toxicity. (Second Embodiment) Next, a second embodiment will be described with reference to the first embodiment.
The following description focuses on the differences from this embodiment.

In this embodiment, the following method is used for dry etching of the TiW thin film 4 in FIG. 5 in the first embodiment, and the other is the same. CDE (Chemical Dry Etcher, CDE-7-4 manufactured by Shibaura Seisakusho)
The CF ₄ —O ₂ —N ₂ gas flow rate was set to 40
-80-280sccm, microwave power 600W,
The dry etching of the TiW thin film 4 is performed at a substrate temperature of 100 ° C. (Third Embodiment) Next, a third embodiment will be described with reference to the first embodiment.
The following description focuses on the differences from this embodiment.

In the present embodiment, the following method is used as the dry etching of the TiW thin film 4 in FIG. 5 in the first embodiment, and the other is the same. CDE
(MAS-1800 manufactured by Canon Inc.)
_The TiW thin film 4 is dry-etched under the conditions of a flow rate of _4- O ₂ gas of 33-17 sccm, a pressure of 0.3 Torr, a microwave power of 1000 W, and a substrate temperature of 100 ° C.

After the etching, the CF ₄ —O ₂ —N ₂ system gas is used to set the CF ₄ —O ₂ —N ₂ system gas flow rate to 10-20-70 sccm and the microwave power 1000
Under the condition of W, TiW attached to the inside of the apparatus is removed. The inside of the apparatus is cleaned by the dry cleaning in the reaction chamber.

[0039] Subsequently, using the same CDE (chemical dry etcher), as shown in FIG. 6, CF ₄ -O
_The Cr-Si-N thin film 3 is dry-etched using a _two- system gas.

As described above, the adhered products can be stably removed by dry cleaning without releasing the reaction chamber of the chemical dry etcher to the atmosphere, and the operation rate of the equipment can be increased.

That is, Ti using a CF ₄ —O ₂ gas is used.
Although the etching hardly proceeds at room temperature during the etching of W, the etching proceeds by heating the semiconductor substrate 1 to increase the temperature. At this time, the temperature of the product generated by the etching decreases while moving in the reaction chamber, solidifies and adheres to the wall surface of the reaction chamber, etc., and lowers the etching rate of the Cr—Si—N thin film 3. Each time about 1 to 25 sheets are processed, the adhered products are removed by dry cleaning using a CF ₄ —O ₂ —N ₂ -based gas. Therefore, when the reaction chamber is released to the atmosphere and wet cleaning is performed with a solution containing alcohol or hydrogen peroxide, the operation rate of the equipment is significantly reduced, but in comparison with this, the reaction chamber is not released to the atmosphere in this example. By the dry cleaning, adhered products can be removed and the operation rate of the equipment can be increased.

As described above, this embodiment has the following features. When cleaning the inside of the dry etching apparatus (i) TiW film 4 (high melting point metal containing titanium), as the cleaning gas adheres CF ₄ -O into the apparatus using a ₂ -N ₂ system gas TiW Since the removal is performed, the inside of the dry etching apparatus can be stably cleaned. (B) More specifically, the dry etching apparatus continuously dry-etches the Cr—Si—N thin film 3 (CrSi-based thin film) on the semiconductor substrate 1 and the TiW thin film 4 thereon. The etching of the TiW thin film 4 is performed while the semiconductor substrate 1 is heated.
However, the TiW can be removed stably, which is practically preferable.

The dry cleaning according to this method can be applied not only to a dry etching apparatus but also to a CVD deposition apparatus.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a semiconductor device in an embodiment.

FIG. 2 is a sectional view showing a manufacturing process of the semiconductor device.

FIG. 3 is a sectional view showing a manufacturing process of the semiconductor device.

FIG. 4 is a sectional view showing a manufacturing process of the semiconductor device.

FIG. 5 is a sectional view showing the manufacturing process of the semiconductor device.

FIG. 6 is a sectional view showing the manufacturing process of the semiconductor device.

FIG. 7 is a sectional view showing the manufacturing process of the semiconductor device.

FIG. 8 is a sectional view showing the manufacturing process of the semiconductor device.

FIG. 9 is a view showing various measurement results when the flow ratio of O ₂ and N ₂ is changed.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Semiconductor substrate, 3 ... Cr-Si-N thin film, 4 ... TiW
Thin film.

Claims (8)

[Claims] 1. A dry etching method for processing a refractory metal containing titanium by dry etching, wherein a CF ₄ —O ₂ —N ₂ -based gas is used as an etching gas. 2. A method of processing a refractory metal containing titanium and tungsten by dry etching, wherein a CF ₄ —O ₂ —N ₂ -based gas is used as an etching gas. Method. 3. A method for cleaning the interior of an apparatus for treating a titanium-containing high melting point metal, wherein the titanium-containing high melting point adhered to the inside of the apparatus using a CF ₄ —O ₂ —N ₂ -based gas as a cleaning gas. A method for cleaning the inside of a device, wherein a metal is removed. 4. The processing apparatus according to claim 1, wherein the processing apparatus comprises:
4. The method according to claim 3, wherein the dry etching is continuously performed on the i-type thin film and the refractory metal containing titanium thereon.
3. The method for cleaning the inside of an apparatus according to 1. 5. The method according to claim 4, wherein the etching of the refractory metal containing titanium is performed while heating the semiconductor substrate. 6. A method for cleaning the inside of an apparatus for treating a refractory metal containing titanium and tungsten, wherein titanium-adhered to the inside of the apparatus using a CF ₄ —O ₂ —N ₂ -based gas as a cleaning gas. A method for cleaning the inside of an apparatus, wherein a tungsten-containing high melting point metal is removed. 7. The processing apparatus according to claim 1, wherein the processing device comprises a CrS on the semiconductor substrate.
7. The method for cleaning the inside of an apparatus according to claim 6, wherein dry etching is continuously performed on the i-type thin film and a refractory metal containing titanium and tungsten thereon. 8. The method according to claim 7, wherein the etching of the refractory metal containing titanium and tungsten is performed while heating the semiconductor substrate.