JPS6059316B2 - Method of forming patterned aluminum layer - Google Patents

Description

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

The wiring layer of a semiconductor integrated circuit device is usually made of an aluminum layer for various reasons. To form a wiring layer made of an aluminum layer for a semiconductor integrated circuit device, conventionally, an aluminum layer to be patterned is formed on a semiconductor substrate, and then a patterned photoresist mask is placed on the aluminum layer. It is common practice to form a patterned aluminum layer as a wiring layer by forming a patterned aluminum layer and then chemically etching the aluminum layer to be patterned using the above mask as a mask. 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 exposed from the side. Therefore, the patterned aluminum layer has a pattern that is one size smaller than the pattern of the mask layer by the amount of side etching. Incidentally, it is desirable that the patterned aluminum layer be obtained in the same pattern as the pattern 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 the amount side-etched, the amount side-etched will be smaller in the chemical etching process described above. , if expected, the pattern in the mask layer, allowing for the amount to be side-etched, saw around the desired pattern of the patterned aluminum layer to a larger pattern;
By forming the aluminum layer in advance, the patterned aluminum layer can be formed to have a desired pattern. However, in the case of the above-mentioned conventional method, in the above-mentioned chemical etching step,
It was extremely difficult to predict the amount of side etching mentioned above.

For this reason, the conventional method described above has drawbacks such as the fact that it is extremely difficult to form a patterned aluminum layer with a desired pattern in a fine and highly accurate manner. Ta. The present invention therefore seeks to provide a new method for forming patterned aluminum layers that does not suffer from the drawbacks mentioned above. The inventor first
As shown in FIG. On the layer 2, as shown in FIG. 1B, an aluminum layer 4 to be patterned is formed, as is known per se, for example by vapor deposition, and then on the aluminum layer 4 to be patterned. As shown in FIG. 1C, a patterned mask layer 5 made of, for example, photoresist is formed on the aluminum layer 4 on the insulating substrate 3, and a photomask is applied to the photoresist layer. The aluminum layer 4 to be patterned is formed on the insulating substrate 3, and the aluminum layer 4 to be patterned is formed on the insulating substrate 3. A substrate body 6 on which a patterned mask layer 5 was formed was obtained.

Then, as shown in FIG. 2, the substrate body 6 was washed with hydrochloric acid (
Electrolyte 11 consisting of an aqueous solution containing HC as the main solute
The aluminum layer 4 is immersed in a tank 12 containing the aluminum layer 4 so as to extend substantially vertically.
An electrode 13 made of, for example, platinum is immersed in the substrate 6 so as to face the aluminum layer 4 of the substrate 6, and the aluminum layer 4 to be patterned on the substrate 6 is masked by the mask layer 5. Connect the electrode 13 to the positive electrode side of the DC power supply 14 in the area where the electrode 13 is not connected.
Connected to the negative electrode side of the DC power supply 14 and connected to the aluminum layer 4.

Electrolytic etching was performed using the mask layer 5 as a mask and using an electrolytic solution consisting of an aqueous solution containing hydrochloric acid as the main solute. In such a case, the area of the aluminum layer 4 that is not masked by the mask layer 5 acts as an anode, and a chemical reaction expressed as Liu→2A13++6e- occurs on the anode side, and electrolysis occurs. A chemical reaction occurs in the liquid 11, and the electrode 13 acts as a cathode, and the chemical reaction expressed as follows occurs on the cathode side. The unmasked areas go from an unetched state as shown in FIG. 3A, to a state that is being etched from the surface, as shown generally in FIG. 3B, to a state as shown generally in FIG. 3C. As shown, it has been confirmed that a patterned aluminum layer 7 is formed under the mask layer 5 by etching the entire thickness.

However, in this case, the electrode 13 was made of platinum. Furthermore, the present inventor carried out the above-mentioned electrolytic etching by using the DC power supply 14 connected between the aluminum layer 4 to be patterned and the electrode 13 as a DC constant current source, and using the mask layer of the aluminum layer 4 as a DC constant current source. The voltage V (volt) between the area not masked by the electrode 13 and the electrode 13 was measured using a voltmeter 15.

In such a case, the relationship between the voltage V 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 (2) 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 has proposed that the above-mentioned electrolytic etching,
The above-mentioned voltage (2) increases rapidly until the point Ta, that is, the point where the area of the aluminum layer 4 not masked by the mask layer 5 is etched over its entire thickness, and the above-mentioned pattern is etched. When forming a patterned aluminum layer 7, the patterned aluminum layer 7
It has been determined that the side surfaces are generally obtained as side etched, as shown in FIG. 3C as being inside the side surfaces of the mask layer 5.

Further, the present inventor carried out the above-mentioned electrolytic etching by using the DC power source 14 connected between the aluminum layer 4 to be patterned and the electrode 13 as a DC constant voltage source, and from the DC constant current source. The current 1 (MA) flowing through the aluminum layer 4 was measured using an ammeter 16.

In such a case, the relationship between current 1 and time t (minutes) is as shown in FIG. 5, as shown in FIG. It was obtained that the current 1 suddenly decreases from . Furthermore, as a result of investigating the relationship of the current 1 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 current 1 increases with the time t. Until the time point Ta'' when the aluminum layer 4 gradually decreases, the area of the aluminum layer 4 that is not masked by the mask layer 5 is etched from the surface with time t, but once the time point Ta'' is reached, The areas of the aluminum layer 4 not masked by the mask layer 5 are etched over their entire thickness, resulting in a patterned aluminum layer 7, as generally shown in FIG. 3C. I came to confirm that it is. Furthermore, the present inventor carried out the above-mentioned electrolytic etching at the point Ta'' when the above-mentioned current 1 suddenly decreases, that is, the region of the aluminum layer 4 that is not masked by the mask layer 5.
up to the point where it is etched through its entire thickness;
When forming the patterned aluminum layer 7 described above, the patterned aluminum layer 7 is generally shown with its sides inward from the sides of the mask layer 5 in FIG. 3C. As such, we have confirmed that it is obtained with side etching.

Further, the present inventor carried out the above-mentioned electrolytic etching by setting the temperature T (°C) of the electrolytic solution 11 to a constant temperature Te (°C), and performing the electrolytic etching from the DC power supply 14 through the aluminum layer 4 on the substrate body 6 and the electrode 13. By changing the current 1 flowing through the electrolyte 11,
Therefore, the density J (MA
/Cri), when the DC power supply 14 is a DC low current source, the above-mentioned voltage V suddenly increases, and when the DC power supply 14 is a DC constant voltage source, the above-mentioned voltage V suddenly increases. When the current 1 decreases rapidly, up to the point where the area of the aluminum layer 4 not masked by the mask layer 5 is etched over its entire thickness, as described above. patterned aluminum layer 7
, and the amount by which the aluminum layer 7 is side etched, that is, the side etching amount Y (μm)
was measured.

In such a case, the relationship between the side etching amount Y and the current density J with the temperature T of the electrolytic solution as a parameter is as follows.
The result was obtained as shown in FIG.

However, as shown in FIG. 6, the electrolytic solution 11 is an aqueous solution containing only hydrochloric acid as a solute, and the temperature Te (℃) of the electrolytic solution 11 is 3.
These are the measurement results when the temperature was 3.0° C. and the aluminum layer 4 had a thickness of 1 μm. Therefore, the 6th
From the measurement results shown in the figure, it has been confirmed that when the temperature T of the electrolytic solution 11 is a constant temperature Te (° C.), if the current density J is increased, the above-mentioned side etching amount Y becomes smaller. .

b In addition, if the current flowing through the electrolyte 11 is increased so that the current density J is increased in this way, the amount of side etching Y can be reduced by increasing the current density J. For example, the electric field strength between the aluminum layer 4 and the electrode 13 is significantly stronger mainly in the direction connecting the aluminum layer 4 and the electrode 13 than in other directions,
For this reason, it is also confirmed that this is because the ratio of the rate at which the area of the aluminum layer 4 that is not masked by the mask layer 5 is etched in the thickness direction and the rate at which it is etched in the planar direction becomes large. I reached it. Furthermore, the current density J
When T is constant, if the temperature T of the electrolytic solution 11 is lowered,
It has been confirmed that the side etching amount Y described above is reduced. Furthermore, it has been confirmed that in order to obtain the same amount of side etching Y as described above, if the temperature T of the electrolytic solution 11 is increased, the current density J can be increased accordingly. Also, from the measurement results shown in Figure 6,
When the value of the side etching amount Y mentioned above becomes zero,
The relationship between the current density J and the temperature T of the electrolytic solution 11 is the seventh
As shown in the figure, and as mentioned above, when the temperature T of the electrolytic solution 11 is constant, if the current density J is increased, the above-mentioned side etching amount Y becomes smaller. The electrolytic etching is performed at a temperature T of the electrolytic solution 11.
If the temperature is set to TeCC) and the current density J is set to a current density equal to or higher than the current density e(MA/C7lf) given by, the above-mentioned patterned aluminum layer 7 will be formed as shown in FIG. , the above-mentioned side etching amount Y
We have also confirmed that it is formed as approximately zero.

Furthermore, the relationship between the current density J and the temperature of the electrolytic solution 11 can be obtained as shown in FIG.
In this case, if the temperature T of the electrolytic solution 11 is lowered, the above-mentioned side etching amount Y becomes smaller.
and the temperature T of the electrolyte 11 is the temperature TeC given by
C) It is also confirmed that if performed at a temperature below, the above-mentioned patterned aluminum layer 7 is formed with the above-mentioned side etching amount Y being approximately zero, as shown in FIG. I reached it.

Therefore, the present inventor has proposed 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 according to the present invention, in the step of electrolytically etching the aluminum layer to be patterned using the patterned mask layer as a mask, the side etching amount of the patterned aluminum layer to be formed is reduced. As is clear from the above description in FIG. 6, Y can be predicted based on the temperature T and current density J of the electrolytic solution. 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 electrolytic etching is performed by changing the temperature T of the electrolytic solution to the temperature TeCC).
If the current density J is set to a current density Je(MA/c!t) or more given by the above-mentioned equations (1a) to (1c), or the current density J is changed to the current density Je(
MA/Clt), and the temperature T of the electrolyte was set to (2) as described above.
If carried out at a temperature equal to or lower than the temperature TeCC given by formulas a) to (2c), the patterned aluminum layer becomes
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. In, when the temperature T of the electrolytic solution is ・temperature Te, the current density J
When the current density is equal to or higher than the current density Je given by the above equations (1a) to (1c), or when the current density J is the current density Je, the temperature T of the electrolytic solution is set to the above-mentioned (2a).
By setting the temperature to the temperature Te given by formula (2c) or less, a patterned aluminum layer having the desired pattern can be easily formed finely and with high precision. It has the following characteristics.

Furthermore, when the electrolytic etching described above is performed using a DC constant current source as the DC power source, the end point of the electrolytic etching in the electrolytic etching process is
an aluminum layer to be patterned as an anode;
Since this corresponds to the point in time when the voltage between the cathode electrode and the cathode electrode increases rapidly, the electrolytic etching described above is By repeating the process up to the point where the value suddenly increases, a patterned aluminum layer can be easily formed with a desired pattern with good reproducibility, fineness, and high precision. has.

Furthermore, when electrolytic etching is performed using a DC constant current source as a DC power source, the voltage between the aluminum layer to be patterned as an anode and the cathode electrode relative to the aluminum layer described above increases suddenly. This can be easily detected by various voltage detectors, and
Depending on the output of the voltage detector, the DC constant current source connected between the aluminum layer as the anode and the corresponding cathode electrode can be turned off, or the DC constant current source and the aluminum layer as the anode or The electrolytic etching described above is applied to the aluminum layer to be patterned as an anode, by simple means such as cutting the line between the cathode and the aluminum layer to be patterned. The process can be immediately and easily terminated at the point where the voltage between the opposing cathode and the cathode electrode suddenly increases.

In addition, when performing the electrolytic etching described above using a DC constant voltage source as a DC power source, the electrolytic etching! In the process of etching.

The end point of the electrolytic etching is determined by the DC constant voltage source.
Since this corresponds to the point at which the current flowing through the aluminum layer to be patterned as an anode suddenly decreases, the electrolytic etching described above can be carried out from a single constant DC voltage source.
By carrying out the process until the point where the current flowing through the aluminum layer to be patterned as an anode suddenly decreases, the patterned aluminum layer can be reproducibly given the desired pattern. It has the characteristics of being able to be formed finely, with high precision, and easily. Furthermore, when electrolytic etching is carried out using a direct current constant current source as the direct current power source, the point at which the current flowing from the direct current constant voltage source through the aluminum layer to be patterned as the anode described above suddenly decreases. can be easily detected by various current detectors, and by the output of the current detector, the aluminum layer as an anode,
Simple means such as turning off the DC constant voltage source connected between the cathode electrode and cutting the line between the DC constant voltage source and the aluminum layer or cathode electrode as the anode. This allows the electrolytic etching described above to be terminated immediately and easily at the point at which the current flowing from a DC constant voltage source through the aluminum layer to be patterned as anode suddenly decreases. can.

Therefore, the above-mentioned 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 solves this by
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.

Example 1 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, a photoresist layer is formed on the mask layer 5 and the aluminum layer 4, and the photoresist layer is exposed to light using a photomask and then developed. 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 placed in a tank 1 containing an electrolytic solution 11 made of an aqueous solution containing hydrochloric acid as a solute, as described above in FIG.
The aluminum layer 4 is immersed in the tank 2 so as to extend substantially vertically, and the electrode 13 made of platinum is immersed in the tank 12 so as to face the aluminum layer 4 of the substrate body 6. Then, the aluminum 4 to be patterned on the substrate body 6 is connected to the positive electrode side of the DC power source 14, which is a DC constant current source, in the area not masked by the mask layer 5, and the electrode 13 to the negative electrode side of the DC power supply 14, and
Electrolytic etching using an electrolytic solution 11 consisting of an aqueous solution containing hydrochloric acid as a solute was carried out until the voltage (2) between the aluminum layer 4 and the electrode 13 suddenly increased to obtain a patterned aluminum layer 7.

In this case, the temperature of the electrolyte 11 is 33.0, the current passed through the electrolyte 11 is 200.0 rT1A, and therefore the current density passed through the aluminum layer 4 is 5.0 (=2
00.0rT1A/40.0c1t) MA/CIL.

In that case, the patterned aluminum layer 7 was formed with approximately zero side etching amount. Example 2 DC power supply 14 in the case of Example 1 of the present invention described above
was used as a DC constant voltage source, and the electrolytic etching was carried out accordingly until the current 1 flowing through the aluminum layer suddenly decreased from the DC constant voltage source. A patterned aluminum layer 7 was obtained using the same steps as in Example 1 of the invention.

In this case, as in the case of Example 1 of the present invention described above, the patterned aluminum layer 7 was formed so that the amount of side etching was approximately zero.

[Brief explanation of the drawing]

FIGS. 1A, B, and C illustrate one sequence 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 present invention. It is a line cross-sectional view in the process of. 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 serves to explain the method of forming a patterned aluminum layer according to the invention by electrolytic etching of the aluminum layer to be patterned using a direct current power source consisting of a direct current constant current source. , is a diagram showing the dependence of the voltage V (volts) between the aluminum layer as an anode in the substrate body and the cathode electrode thereto with respect to time t (minutes) in the process of forming a patterned aluminum layer. be. FIG. 5 also shows an example of electrolytic etching of an aluminum layer to be patterned using a DC power source, which is a DC constant voltage source, to explain a method of forming a patterned aluminum layer according to the present invention. For time t (minutes) in the step of forming a patterned aluminum layer by
The figure shows the relationship between a current 1 (MA) flowing from a DC constant voltage source through an aluminum layer as an anode in a substrate body. FIG. 6 also provides an illustration of a method of forming a patterned aluminum layer according to the present invention.
In the present invention, the current density J (MA/Clt) with the temperature of the electrolytic solution as a parameter in the process of forming a patterned aluminum layer by electrolytic etching on the aluminum layer to be patterned. FIG. 3 is a diagram showing the relationship between the side etching amount Y (μm) of the patterned aluminum layer thus formed. 7th
The figure also illustrates the process of forming a patterned aluminum layer by electrolytic etching on the aluminum layer to be patterned, which serves to explain the method of forming a patterned aluminum layer according to the invention. , the current density J (MA/d
) is a diagram showing the relationship between FIG. 8 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... Board, 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, 16...Ammeter.

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 hydrochloric 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 a current density J (mA/cm ^2), Te=a・Je+ba
= 3.33 (1 ± 0.1) b = 16.5 (1 ± 0.1) Patterned aluminum characterized by conducting at a current density equal to or higher than Je (mA/cm^2) given by b = 16.5 (1 ± 0.1) How to form layers. 3. In the method for forming a patterned aluminum layer according to claim 1, the electrolytic etching is performed at a current density J (mA/cm^2) of Je (mA/cm^2).
m^2), the temperature of the electrolyte is T (℃), and Te=
a・Je+b a=3.33 (1±0.1) b=16.5 (1±0.1) A patterned aluminum layer characterized by being carried out at a temperature equal to or lower than Te (°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 hydrochloric 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 corresponding thereto. A patterned aluminum layer is formed by connecting a DC constant current source until the voltage between the aluminum layer to be patterned as an anode and the cathode electrode suddenly increases. A method of forming a patterned aluminum layer, the method comprising forming a patterned aluminum layer. 5. In the method of forming a patterned aluminum layer according to claim 4, the electrolytic etching is performed at a temperature T of the electrolytic solution.
(℃) is Te (℃), current density J (mA/cm^2
) at a current density equal to or higher than Je (mA/cm^2) given by Te=a・Je+ba=3.33 (1±0.1) b=16.5 (1±0.1) A method of forming a patterned aluminum layer featuring features. 6. In the method for forming a patterned aluminum layer according to claim 4, the electrolytic etching is performed at a current density J (mA/cm^2) of Je (mA/cm^2).
m^2), and the temperature T (℃) of the electrolyte is Te=a
・Je + b a=3.33 (1±0.1) b=16.5 (1±0.1) A patterned aluminum layer characterized by being formed at a temperature below Te (℃) given by a=3.33 (1±0.1) b=16.5 (1±0.1) How to form. 7 Forming an aluminum layer to be patterned on an insulating substrate, forming a patterned mask layer on the aluminum layer, and then applying hydrochloric 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 corresponding thereto. The patterned material was patterned by connecting a DC constant voltage source and conducting the process until the current flowing from the DC constant voltage source through the aluminum layer to be patterned as the anode suddenly became small. A method of forming a patterned aluminum layer comprising forming an aluminum layer. 8. A method of forming a patterned aluminum layer according to claim 7, as described above. Electrolytic etching is performed by changing the temperature T (℃) of the electrolyte solution to Te (
℃), and the current density J (mA/cm^2) is Te=a
・Je+ba=3.33(1±0.1)b=16.5(
A method for forming a patterned aluminum layer, characterized in that the process is carried out at a current density equal to or higher than Je (mA/cm^2) given by 1±0.1). 9 In the method for forming a patterned aluminum layer according to claim 7, the electrolytic etching is performed at a current density J (mA/cm^2) of Je (mA/cm^2).
m^2), and the temperature T (℃) of the electrolyte is Te=a
・Je + b a=3.33 (1±0.1) b=16.5 (1±0.1) A patterned aluminum layer characterized by being formed at a temperature below Te (℃) given by a=3.33 (1±0.1) b=16.5 (1±0.1) How to form.