JPS6056440B2 - Method of forming patterned aluminum layer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for forming a patterned aluminum layer on an insulating substrate, and is particularly suitable for application to forming wiring layers of semiconductor integrated circuit devices.

The wiring layer of a semiconductor integrated circuit device is usually made of an aluminum layer for various reasons.

By the way, in order to form a wiring layer made of an aluminum layer of a semiconductor integrated circuit device, conventionally, an aluminum layer to be patterned is formed on a semiconductor substrate, and then a patterned photoresist is deposited on the aluminum layer. It is common practice to form a patterned aluminum layer as a wiring layer by forming a mask using the mask and then chemically etching the aluminum layer to be patterned using the mask as a mask. It was. However, in the case of such a conventional method, in the step of chemically etching the aluminum layer to be patterned using the patterned mask layer as a mask, the patterned aluminum layer is etched from the side. In other words, it is forced to be obtained as a so-called side-etched material.

For this reason, the pattern. The etched aluminum layer is formed to have a pattern that is one size smaller than the pattern of the mask layer by the side-etched amount. Preferably, the patterned aluminum layer is obtained with the same pattern as that of the mask layer. The reason is that by simply forming a mask layer in the same pattern as the patterned aluminum layer to be formed, the patterned aluminum layer can be formed with the desired pattern. This is because it is possible to do so.

However, even if the patterned aluminum layer is formed with a pattern that is one size smaller than the pattern of the mask layer by an amount that is side-etched,
In the chemical etching process described above, if the amount of side etching is predicted, the pattern of the mask layer is formed at the location of the patterned aluminum layer to be formed, taking into account the amount of side etching. By forming in advance a pattern that is larger around the saw than the initial pattern, the patterned aluminum layer can be formed to have the desired pattern. However, in the case of the conventional method described above, it is extremely difficult to predict the amount of side etching described above in the chemical etching process described above.

Therefore, in the case of the above-mentioned conventional method, there are drawbacks such as the fact that it is extremely difficult to form a patterned aluminum layer with a desired pattern finely and with high precision. The present invention therefore seeks to propose a new method for forming a patterned aluminum layer that does not have the above-mentioned disadvantages. For example, an insulating substrate 3 in which an insulating layer 2 made of silicon oxide (SiO2) is formed on a substrate 1 made of silicon is prepared in advance, and a first The aluminum layer 4 to be patterned is formed, as shown in FIG. As shown, a patterned mask layer 5 made of, for example, a photoresist is formed on an aluminum layer 4 on an insulating substrate 3, and the photoresist layer is exposed to light using a photomask, followed by development. The aluminum layer 4 to be patterned is thus formed on the insulating substrate 3, and the patterned mask layer 5 is formed on the aluminum layer 4. A substrate body 6 on which was formed was obtained.

Then, as shown in FIG.
The aluminum layer 4 is immersed in a tank 12 containing an electrolytic solution 11 consisting of an aqueous solution containing H3PO4 as the main solute, so that the aluminum layer 4 extends substantially vertically, and in the tank 12, An electrode 13 made of platinum, for example, is immersed so as to face the aluminum layer 4 of the substrate body 6, so that the aluminum layer 4 to be patterned on the substrate body 6 is not masked by the mask layer 5. In the region, it is connected to the positive electrode side of the DC power supply 14, and also connected to the positive electrode side of the DC power supply 14.
3 was connected to the negative electrode side of the DC power source 14, and the aluminum layer 4 was electrolytically etched using the mask layer 5 as a mask and an electrolytic solution consisting of an aqueous solution containing phosphoric acid as the main solute.

In that case, the area of the aluminum layer 4 not masked by the mask layer 5 acts as an anode, and
On the anode side, a chemical reaction expressed as occurs, and in the electrolyte 11, a chemical reaction expressed as occurs, and furthermore, the electrode 13 acts as a cathode, and on the cathode side, a chemical reaction expressed as occurs. With this mechanism, the area of the aluminum layer 4 that is not masked by the mask layer 5 is etched from the unetched state shown in FIG. 3A to the surface generally shown in FIG. 3B. After the etching process, we observe that a patterned aluminum layer 7 is formed under the mask layer 5 through its entire thickness, as generally shown in FIG. 3C. It has arrived.

However, in this case, the electrode 13 was made of platinum. Further, the present inventor performed the electrolytic etching described above by measuring the voltage (volts) between the area of the aluminum layer 4 that is not masked by the mask layer 5 and the electrode 13 using a voltmeter.
5 while making measurements.

In such a case, the relationship between the voltage ■ and the time t (minutes) is as shown in FIG. 4, as shown in FIG. was obtained as rapidly increasing in size.

Furthermore, as a result of investigating the relationship of the voltage V with respect to the time t mentioned above and the state of etching of the region of the aluminum layer 4 that is not masked by the mask layer 5, the inventor found that the voltage V changes with time t. The point in time when Ta is gradually increasing
Until then, the mask layer 5 of the aluminum layer 4
The areas not masked by the mask layer 5 are etched from the surface with time t, but once the time Ta is reached, the area of the aluminum layer 4 not masked by the mask layer 5 has been etched over its entire thickness. Figure 3C
It has now been confirmed that a patterned aluminum layer 7 is obtained, as generally shown in FIG.

Furthermore, the present inventor carried out the above-mentioned electrolytic etching at a point t1 when the above-mentioned voltage (2) suddenly increases, that is, when the region of the aluminum layer 4 not masked by the mask layer 5 is completely covered with its entire thickness. 3C to the point where it is etched to form the patterned aluminum layer 7 described above, the patterned aluminum layer 7 has a side surface that is closer to the side surface of the mask layer 5 in FIG. 3C. We have come to the conclusion that it is generally obtained as side etched, as shown on the inside.

The present inventor also performed the electrolytic etching described above using the temperature TCC of the electrolytic solution 11 as a parameter, and the DC power supply 14.
By changing the current flowing into the electrolytic solution 11 through the aluminum layer 13 and the electrode 13 in the substrate body 6, and therefore changing the density 1 (MA/Cl,) of the current flowing into the aluminum layer 4, the above-mentioned voltage (2) can be adjusted. , up to the point Ta where the area of the aluminum layer 4 which is not masked by the mask layer 5 is etched over its entire thickness, until the patterned aluminum layer described above is etched. 7 is formed, and the amount by which the aluminum layer 7 is side etched, that is, the side etching amount Y (μ
m) was measured.

In such a case, the relationship between the side etching amount Y and the current density 1 using the temperature T of the electrolytic solution as a parameter is as follows.
The result was obtained as shown in FIG. However, FIG. 5 shows the measurement results when the electrolytic solution 11 is an aqueous solution containing only phosphoric acid (H3PO4) as a solute, and the aluminum layer 4 has a thickness of 1 μm. Therefore, from the measurement results shown in FIG. 5, if the temperature T of the electrolytic solution 11 is constant, and the current density 1 is increased, the side etching amount Y described above will be reduced.
We have come to the conclusion that it becomes small.

Furthermore, if the current flowing through the electrolytic solution 11 is increased so that the current density 1 is increased, the side etching amount Y
If the current density 1 is increased, the electric field strength between the aluminum layer 4 and the electrode 13 is mainly related to the direction connecting the aluminum layer 4 and the electrode 13. , is much stronger than in other directions, and therefore, the rate at which the region of the aluminum layer 4 not masked by the mask layer 5 is etched in the thickness direction,
We have also confirmed that this is because the ratio to the etching speed in the planar direction is large.

Further, from the measurement results shown in FIG. 5, it has been confirmed that when the current density I is kept constant, the side etching amount Y described above can be reduced by lowering the temperature T of the electrolytic solution 11. Furthermore, it has been confirmed that in order to obtain the above-mentioned side etching amount Y at the same value, if the temperature T of the electrolytic solution 11 is increased, the current density 1 can be increased accordingly.

Moreover, from the measurement results shown in FIG. 5, the temperature T of the electrolytic solution 11 when the value of the side etching amount Y becomes zero
As shown in FIG. 6, the relationship between the current density 1 and the current density 1 is obtained as shown in FIG. Since the amount Y becomes small, the electrolytic etching process described above is performed with the temperature T of the electrolytic solution 11 being T8 (°C) and the current density 1 being given by (MA/Clt) or more. For example, it has been confirmed that the above-mentioned patterned aluminum layer 7 is formed with the above-mentioned side etching amount Y being approximately zero, as shown in FIG.

Furthermore, the relationship between the current density I and the temperature T of the electrolytic solution 11 is obtained as shown in FIG. This is because the side etching amount Y mentioned above becomes small, so the electrolytic etching mentioned above is carried out at a current density of 1.
(MA/CTl), and the temperature T of the electrolytic solution 11 is below the temperature TeCC given by, the above-mentioned patterned aluminum layer 7 will be formed as shown in FIG. It has also been confirmed that the side etching amount Y is approximately zero.

Therefore, the present inventor has come to propose the invention described in the claims as an invention according to the present invention.

The method of forming a patterned aluminum layer according to the invention has now been clarified.

According to the method 13 of the present invention, in the step of electrolytically etching the aluminum layer to be patterned using the patterned mask layer as a mask, side etching of the patterned aluminum layer formed is performed. As is clear from the above description in FIG. 5, the amount Y is determined by the temperature T of the electrolyte and the current density 1.
Can be predicted. Therefore, in the step of forming a patterned mask layer on the aluminum layer to be patterned, the patterned mask is formed taking into account the expected side etching amount Y, so that the patterned mask layer is not patterned. The present invention has the characteristic that an aluminum layer having a desired pattern can be easily formed finely and with high precision.

In addition, in the electrolytic etching process described above, the electrolyte temperature T is TeCC), and the current density 1 is given by the above equations (1a) to (1c) (MA/Clt). If carried out at a current density of
Alternatively, if the current density is 1 (MA/Clt) and the temperature T of the electrolyte is below Te (℃) given by the above equations (2a) to (2c), a patterned aluminum layer can be formed. However, the side etching amount Y is approximately zero.

For this reason, in the process of forming a patterned mask layer, the mask layer is formed in the same pattern as the intended pattern of the patterned aluminum layer to be formed, and also in the electrolytic etching process described above. When the temperature T of the electrolytic solution is L, the current density 1 is equal to or higher than the current density given by the above equations (1a) to (1c), or when the current density 1 is set to By setting the temperature T at a temperature equal to or lower than the temperature Te given by equations (2a) to (2c) above, the patterned aluminum layer can be finely and highly heated to have the desired pattern. It has the characteristics of being easy to form with high precision.

Furthermore, in the electrolytic etching process described above,
Since the end point of the electrolytic etching corresponds to the point where the voltage between the aluminum layer to be patterned as an anode and the cathode electrode increases rapidly, the electrolytic etching described above is The patterned aluminum layer has the desired pattern by increasing the voltage between the aluminum layer to be patterned and the cathode electrode to the point where the voltage suddenly increases. It has the characteristics that it can be easily formed with good reproducibility, fineness, and high precision.

Furthermore, at the point in time when the voltage between the aluminum layer to be patterned as an anode and the cathode electrode thereto suddenly increases, this can be easily detected using various voltage detectors. In addition, depending on the output of the voltage detector, it is possible to turn off the DC power supply connected between the aluminum layer as the anode and the corresponding cathode electrode, or to turn off the DC power supply and the anode electrode. The above-mentioned electrolytic etching can be carried out by simple means such as cutting the line between the aluminum layer or the cathode electrode, by reducing the voltage between the aluminum layer to be patterned as an anode and the cathode electrode therewith. It can be terminated immediately and easily at the point when the value suddenly increases.

Therefore, the present invention has the feature that the above-described features of the present invention can be reliably and easily exhibited.

Further, the patterned aluminum layer formed by the method for forming a patterned aluminum layer according to the present invention functions as a wiring layer. Therefore, the present invention is characterized in that it is extremely suitable for application to forming wiring layers of semiconductor integrated circuit devices.

Next, an example of the present invention will be described.

In the same manner as described above with reference to FIG. 1A, an insulating substrate 3 having an insulating layer 2 formed on the substrate 1 was prepared in advance.

However, in this case, the substrate 1 was made of silicon and had a surface area of about 40.0 d. Further, the insulating layer 2 was made of silicon oxide (SiO2). Thus, on the insulating layer 2 of the insulating substrate 3, an aluminum layer 4 to be patterned was formed in the same manner as described above with reference to FIG. 1B. however,
In this case, the aluminum layer 4 was formed by vapor deposition to have a thickness of 1 μm. Next, a patterned mask layer 5 was formed on the aluminum layer 4 in the same manner as described above in FIG. 1C.

However, in this case, the mask layer 5 can be made of a photoresist by forming a photoresist layer on the aluminum layer 4, exposing the photoresist layer to light using a photomask, and subsequently developing it. Formed as. In this way, an aluminum layer 4 to be patterned on an insulating substrate 3, similar to that described above in FIG. 1C.
A substrate body 6 was obtained in which a patterned mask layer 5 was formed on the aluminum layer 4.

Next, the substrate body 6 is prepared using phosphoric acid (
The aluminum layer 4 is immersed in a tank 12 containing an electrolytic solution 11 made of an aqueous solution containing H3PO4) as a solute, so as to extend substantially vertically. The electrode 13 is connected to the aluminum layer 4 of the substrate body 6.
The aluminum layer 4 to be patterned on the substrate body 6 is immersed in the mask layer 5 so as to face the aluminum layer 4 to be patterned on the substrate body 6.
In the area not masked by
4, and connect the electrode 13 to the positive electrode side of the DC power source 14.
The aluminum layer 4 is not electrolytically etched using an electrolytic solution 11 made of an aqueous solution containing phosphoric acid as a solute until the voltage V between the aluminum layer 4 and the electrode 13 suddenly increases. , a patterned aluminum layer 7 was obtained.

In this case, the temperature of the electrolyte 11 is 20.0°C, the current passed through the electrolyte 11 is 50.0r11A, and therefore the current density passed through the aluminum layer 4 is 1.25 (=50
．． 0/40.0c11) MA/d.

In that case, a patterned aluminum layer was formed with approximately zero side etching.

[Brief explanation of the drawing]

Figures 1A, B and C illustrate the sequential steps of forming a patterned mask layer on an aluminum layer to be patterned, illustrating a method of forming a patterned aluminum layer according to the invention. It is a sectional view along the route. FIG. 2 likewise illustrates the process of forming a patterned aluminum layer by electrolytic etching on the aluminum layer to be patterned, illustrating the method of forming a patterned aluminum layer according to the invention. It is a route map showing. FIG. 3 likewise illustrates the process of forming a patterned aluminum layer by electrolytic etching on the aluminum layer to be patterned, illustrating the method of forming a patterned aluminum layer according to the invention. It is a sectional view along the route. FIG. 4 likewise illustrates the process of forming a patterned aluminum layer by electrolytic etching on the aluminum layer to be patterned, illustrating the method of forming a patterned aluminum layer according to the invention. FIG. 3 is a diagram showing the relationship of voltage between an aluminum layer as an anode in a substrate body and a cathode electrode thereto with respect to time t (minutes) in FIG. Similarly, FIG.
To explain the method for forming a patterned aluminum layer according to the present invention, the temperature of the electrolyte is a parameter in the step of forming a patterned aluminum layer by electrolytic etching on the aluminum layer to be patterned. current density 1 (MA/Clt)
FIG. 3 is a diagram showing the relationship between the amount of side etching Y (μm) of a patterned aluminum layer formed according to the present invention and the amount of side etching Y (μm). FIG. 6 also shows the formation of a patterned aluminum layer by electrolytic etching on the aluminum layer to be patterned, which serves to illustrate the method of forming a patterned aluminum layer according to the invention. In the forming process, the current density 1 (MA/Clt) with respect to the temperature T (°C) of the electrolytic solution when the side etching amount Y of the patterned aluminum layer formed by the present invention becomes zero It is a figure showing a relationship.
FIG. 7 is a cross-sectional view showing an example of a patterned aluminum layer obtained by the method of forming a patterned aluminum layer according to the present invention. 1・
...Substrate, 2 ... Insulating layer, 3 ... Insulating substrate, 4 ... Aluminum layer to be patterned, 5 ... ... Patterned mask layer, 6
... Substrate body, 7 ... Patterned aluminum layer, 11 ... Electrolyte, 12 ...
... Tank, 13 ... Electrode, 14 ... DC power supply, 15 ... Voltmeter.

Claims (1)

[Claims] 1. An aluminum layer to be patterned is formed on an insulating substrate, a patterned mask layer is formed on the aluminum layer, and then the mask layer is applied to the aluminum layer. A patterned aluminum layer is formed by performing electrolytic etching using a mask and an electrolytic solution consisting of an aqueous solution containing phosphoric acid as the main solute. How to form. 2. In the method for forming a patterned aluminum layer according to claim 1, the electrolytic etching is performed at a temperature T (°C) of the electrolytic solution at T_e (°C),
The current density I (mA/cm^2) is T_e=aI_e+
ba = 2.09 (1 ± 0.1) b = 17.5 (1 ± 0.1) Method of forming an aluminum layer. 3. In the method of forming a patterned aluminum layer according to claim 1, the electrolytic etching is performed at a current density I (mA/cm^2) of I_e (mA
/cm^2), and the temperature T (℃) of the electrolyte is T_
e=aI_e+ba a=2.09 (1±0.1) b=17.5 (1±0.1) A patterned aluminum layer characterized in that it is carried out at a temperature equal to or lower than T_e (°C) given by How to form. 4 Forming an aluminum layer to be patterned on an insulating substrate, forming a patterned mask layer on the aluminum layer, and then applying phosphoric acid to the aluminum layer using the mask layer as a mask. Electrolytic etching is performed using an electrolytic solution consisting of an aqueous solution containing as the main solute, using the aluminum layer to be patterned as an anode, and between the aluminum layer to be patterned as the anode and the cathode electrode therefor. A method for forming a patterned aluminum layer, characterized in that the patterned aluminum layer is formed by applying a voltage of up to a point where the voltage suddenly increases. 5. In the method of forming a patterned aluminum layer according to claim 4, the electrolytic etching is performed at a temperature T (°C) of the electrolytic solution at T_e (°C),
The current density I (mA/cm^2) is T_e=aI_e+
ba = 2.09 (1 ± 0.1) b = 17.5 (1 ± 0.1) Method of forming an aluminum layer. 6. In the method for forming a patterned aluminum layer according to claim 4, the electrolytic etching is performed at a current density I (mA/cm^2) of I_e (mA/cm^2).
cm^2), and the temperature T (°C) of the electrolyte is T_e
=aI_e+b a=2.09 (1±0.1) b=17.5 (1±0.1) The patterned aluminum layer is formed at a temperature below T_e (°C) given by How to form.