JP3176312B2 - Dry etching method for aluminum alloy film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a semiconductor device having a wiring of aluminum or the like, and more particularly to a method of forming a wiring suitable for miniaturization.

[0002]

2. Description of the Related Art In recent years, miniaturization of semiconductor devices has been rapidly advanced, and accordingly, the era of wiring has also entered the quarter micron level (0.25 μm). In patterning such a miniaturized structure, the difference in etching rate due to the density of the pattern becomes significant, and it becomes difficult to process a fine pattern. That is, as the pattern to be etched becomes finer, the so-called microloading effect, in which the etching depth decreases, is observed.

FIG. 4 is a diagram for explaining a microloading effect at the time of processing a metal wiring. Referring to FIG. 4, the etching rate in a wide space is represented by a, and the etching rate in a narrow space is represented by b. In general, the difference (ab) in the etching rate due to the density of the pattern is represented by the etching rate a of the sparse pattern portion. The value obtained by dividing the value by a percentage (%) is called a “microloading effect” (also referred to as a “μ loading effect”). μ loading effect (%) = (ab) / a × 100

[0004] The microloading effect is that ions and radicals as etchants are less likely to reach the surface to be etched in a dense pattern portion than in a sparse pattern portion.
And the etching products are less likely to desorb. FIG. 5 is a diagram schematically illustrating the cause of the occurrence of the microloading effect during metal wiring processing. In the figure, an inverted triangle indicates ions as an etchant, a double circle indicates an etching product, and in a dense pattern portion, (1)
This shows how the shortage of the amount of the etchant and (2) difficulty in desorbing the etching product occur. In the drawing, PR indicates a photoresist film, TiN functions as a reflection preventing film, and AlCu indicates a wiring layer.

To solve such a problem, see, for example,
In order to efficiently remove a reaction product from a substrate, suppress a microloading effect, and increase processing accuracy, Japanese Patent Application Laid-Open No. 291908/88 discloses light having energy to excite core electrons of a reaction product atom during etching. An etching method characterized by intermittent irradiation and applying a negative voltage to an electrode facing an etching substrate has been proposed.

According to this conventional etching method, when a silicon surface is irradiated with light capable of exciting halogen atoms such as chlorine and fluorine and inner atoms of silicon atoms, a silicon halide ionized reaction product is obtained. Desorption from the surface and, at the same time, application of a vertical electric field to the substrate facilitates the desorption of the generated ions, and allows the reaction product to be easily pulled out from the fine grooves on the silicon surface, resulting in a microloading effect. It is said that can be deterred.

As a second conventional method, in a semiconductor device having a metal film, an impurity such as phosphorus is ion-implanted in advance in a region where the wiring pattern is dense in the metal film, and the etching rate of the dense pattern portion is reduced. A method of reducing the microloading effect by increasing the size is known (for example, Japanese Patent Application Laid-Open No. 8-78414).
In this conventional method, RIE (Reactive Io)
This is a method that utilizes a phenomenon that, when impurity ions are implanted in advance when patterning a metal thin film such as aluminum by a dry etching method such as n Etching (reactive ion etching) method, the etching rate increases. .

Further, as a third conventional method, a method is known in which a nitrogen gas or a chlorofluorocarbon gas is added to the main gas as an etching gas to suppress the microloading effect (for example, JP-A-7-74156). Gazette). This is a method in which a deposition gas such as a nitrogen gas or a chlorofluorocarbon gas is added to enhance the deposition property of a wide opening, and the etching rate is reduced, thereby reducing a rate difference due to pattern density.

[0009]

However, the above-mentioned conventional method has the following problems.

(1) First, the above-mentioned JP-A-6-291088
It has been proposed in Japanese Patent Application Publication, during etching, intermittently irradiating light having energy to excite inner-shell electrons of reaction product atoms, and applying a negative voltage to an electrode facing the etching substrate. The conventional etching method aims at easily removing an etching product existing inside a fine pattern from a surface in order to improve a microloading effect, but will be described with reference to FIG. As you can see, the microloading effect
The fact that the etchant does not easily enter the inside of the fine pattern is also a factor. In the conventional method proposed in the above-mentioned Japanese Patent Application Laid-Open No. 6-291088, no consideration is given to this point.

In addition, an apparatus for realizing the etching method proposed in the above-mentioned Japanese Patent Application Laid-Open No. 6-291088 requires a special apparatus configuration, and the optimization of conditions becomes more difficult due to an increase in parameters. Problems.

(2) Next, the ion implantation of phosphorus or the like is performed in advance in the narrow opening, and the microloading effect is reduced by increasing the etching rate of the narrow opening. With regard to (2), not only the number of steps is increased, but also there is a concern that the characteristics and reliability of the device may be deteriorated due to the implantation of unnecessary ions into the wiring.

(3) Further, in the third method of adding a nitrogen gas or a chlorofluorocarbon gas to the main gas as an etching gas to suppress the microloading effect, first, the inside of the chamber by adding a deposition gas is used. There is a concern that the number of particles will increase.

Also, the addition of the deposition gas causes a problem that the partial pressure of chlorine, which is the main etching gas, is reduced, so that the etching rate is reduced and the selectivity with respect to the mask is reduced. are doing.

Accordingly, the present invention has been made in view of the above-mentioned problems, and has as its object to eliminate the need for a special device configuration or a special pre-processing step for suppressing the microloading effect, and to provide a data processing device. An object of the present invention is to provide a method for manufacturing a semiconductor device that suppresses a microloading effect without using a positional gas.

[0016]

To achieve the above object, according to an aspect of, the present invention, by using a gas containing chlorine, aluminum by an ion saturation current density approximately 20 mA / cm ² or more 40 mA / cm ² for plasma The alloy film is dry-etched.

[0017]

Embodiments of the present invention will be described below. The present invention, in its embodiment, preferably has a value of the ion saturation current density of 20 mA / cm.
By applying high-density plasma of ² or more and 40 mA / cm ² or less to metal wiring etching,
The micro loading effect can be significantly suppressed. This is because, given a constant bias power value, by increasing the plasma density,
Since the self-bias voltage (Vdc) decreases and the incident energy of ions decreases, it becomes difficult to remove the deposition adhering to the surface of the workpiece. Then, the etch rate of the sparse pattern region to which the deposition type easily adheres decreases. Due to this phenomenon, there is an effect that the microloading effect is suppressed.

It is to be noted that simply reducing the power value applied to the bias and lowering the ion energy does not provide the same effect as the above-described present invention. This is because, in a fine pattern, an etching residue occurs, and in a sparse pattern, side etching occurs.

[0019]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of the present invention;

FIG. 1 shows a schematic configuration of an etching apparatus used in one embodiment of the present invention. This etching apparatus is equipped with a helicon wave plasma source, and further has a Langmuir probe mounted on the diffusion chamber wall for plasma analysis. Thereby, the ion saturation current density distribution of about 25 mm on the wafer can be measured. In FIG. 1, 100 is a chamber, 101 and 101 'are high frequency (RF) power supplies, 102 is an electromagnetic coil, 103 is a substrate (etching sample), 104 is an electrode (substrate side electrode), 1
05 is a Langmuir probe, 106 is an RF antenna,
A high frequency is applied from the RF antenna 106, and electrons are accelerated and turned to generate ions.

The structure of the sample for evaluating the microloading effect is as follows: PR (photoresist film) / TiN (antireflection film) / A
1Cu (wiring) / TiN (barrier metal) / Sub (substrate) = 1000/25/900/50 (nm), and etching was performed at a specified time so that it could be stopped in the middle of the AlCu film.

The etching conditions were as follows: chlorine 80 sccm, boron trichloride 20 sccm, pressure 10 mTorr, bias power 140 W, magnetic field coil current value IN / OUT = 4
0 A / 25 A, and the relationship between the ion saturation current density and the microloading effect was evaluated by changing the source power from 1 to 3 kW.

In this example, the difference between the open area and the etching rate inside the 0.4 μm space was evaluated for the evaluation of the microloading effect. The result is shown in FIG. In FIG. 2, the horizontal axis represents the ion saturation current density (mA / cm ² ), and the vertical axis represents the microloading effect (%) (100 × (ab) / a; the etching rate of the sparse portion, b: the etching rate of the dense portion). Is shown.

From the results shown in FIG. 2, the microloading effect is remarkably reduced as the ion saturation current density increases up to the ion saturation current density of 24 mA / cm ² . Conversely, it became clear that the microloading effect tends to increase and saturate.

FIG. 2 shows that the ion saturation current density is 20 mA.
It can be seen that the microloading effect can be reduced to 10% or less when the value is in the range of / mA ^{2 to} 40 mA / cm ² .

FIG. 3 shows the ion etching current density dependence of the aluminum etching rate in the sparse pattern portion and the aluminum etching rate in the 0.4 μm space. FIG.
It can be seen from the results that the aluminum etching rate has a peak in both the sparse pattern portion and the dense pattern portion.

That is, at first, the etching rate tends to increase as the etchant increases, but the ion energy relatively decreases as the ion current density increases. For this reason, it is considered that when the threshold value is not more than a certain threshold value, it is difficult to remove the deposition attached to the surface, so that the etch rate is reduced.

The reason why the value of the ion current density at the time of taking the peak value differs between the sparse pattern portion and the dense pattern portion is that deposition is more likely to occur in the sparse pattern portion, so that the etching is necessary for etching. This is considered to be due to the high ion energy threshold.

As described above, since the value of the ion current density at which the maximum value of the aluminum etch rate is different between the sparse pattern portion and the dense pattern portion, at the ion current density value at which the aluminum etch rate of the dense pattern portion becomes maximum, The microloading effect is most suppressed.

As described above, according to the present embodiment, the microloading effect can be achieved without using any special device configuration or special pretreatment step, and without using the deposition gas which causes particles. It becomes possible to suppress.

[0031]

As described above, according to the present invention,
By using a gas containing chlorine and applying high-density plasma having an ion saturation current density of 20 mA / cm ² or more and 40 mA / cm ² or less to the etching of the aluminum alloy film, the microloading effect is significantly suppressed. The effect is that it can be done.

[Brief description of the drawings]

FIG. 1 is a diagram showing a schematic configuration of an etching apparatus and a plasma measuring apparatus used in one embodiment of the present invention.

FIG. 2 is a diagram showing a relationship between an ion saturation current density and a microloading effect in one embodiment of the present invention.

FIG. 3 is a diagram showing a relationship between an ion saturation current density and an aluminum etch rate in one example of the present invention.

FIG. 4 is a diagram illustrating a micro-loading effect during metal wiring processing.

FIG. 5 is a diagram illustrating the cause of the occurrence of a microloading effect during metal wiring processing.

[Explanation of symbols]

 REFERENCE SIGNS LIST 100 chamber 101 high frequency power supply (RF power supply) 102 electromagnetic coil 103 substrate (sample) 104 electrode (substrate side electrode) 105 Langmuir probe 106 RF antenna coil 107 bell jar

────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-1-321634 (JP, A) JP-A-6-132258 (JP, A) JP-A-4-29316 (JP, A) JP-A-5-132 275376 (JP, A) JP-A-8-17796 (JP, A) JP-A-6-248459 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 21/3065

Claims (1)

(57) [Claims] With 1. A gas containing chlorine, characterized in ion saturation current density to form a dry etching to the wiring patterns of aluminum alloy film from 20 mA / cm ² at 40 mA / cm ² in the range of plasma, it Manufacturing method of a semiconductor device.