JPH0127572B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method and apparatus for forming electrical wiring on a conductive layer on a substrate by chemical etching using an etching solution.

When forming electrical wiring, a method is used in which the conductive layer attached to the substrate is chemically etched using an etching solution and selectively removed, but the progress of this etching process is monitored. There is no suitable method to do this, and conventionally management has been based on visual inspection and experience.

Etching can also be accomplished by conventional visual and empirical methods if temperature and time control are strictly performed. However, as the degree of integration of circuit elements increases, the degree of integration of electrical wiring also increases, the wiring on the board becomes thinner and the spacing becomes extremely narrow, and patterns become more complex and require higher precision. Conventional methods have drawbacks such as variations in etching from person to person, even if the person is an expert, resulting in overetching or insufficient etching.

Further, electrolytic etching is used for etching the conductive layer. Electrolytic etching is a method in which a DC voltage is applied between two electrodes to force a current to flow between the two electrodes, and the current accelerates etching.

FIG. 1 is a block diagram of an electrolytic etching bath and an electric circuit.

1 is an etching tank, 2 is a substrate on which aluminum is deposited, 3 is an aluminum wire, 5 is a platinum wire, and 4 is a resin holder for bringing the aluminum deposited on the substrate 2 into contact with the aluminum wire 3 and holding it down. 6 is a resistor, 7 is a battery, and 8 is an etching liquid containing phosphoric acid as a main component.

After aluminum is deposited on the substrate 2 and a photoresist is applied thereto, a mask is applied, the substrate is exposed to light and developed, and an etching solution 8 is used to selectively remove the aluminum in the areas where the resist is not attached.

Using the holder 4, the aluminum wire 3 is brought into contact with the aluminum part on the substrate 2 to serve as one pole, and the platinum wire 5 is used as the other pole with the etching solution 8.
When placed in the substrate 2 and a current is applied, a chemical change occurs and the etching of the aluminum on the substrate 2 is promoted.

Etching solution 8 contains phosphoric acid with a concentration of 85% at a volume ratio of 17.
The composition used is one volume ratio of nitric acid with a concentration of 63% and two volume ratios of water. When using this etching solution, the etching speed at a temperature of 22°C and a current of 30mA is
It was 600 Å/min.

FIG. 2 is a diagram showing the temporal change in current value when the substrate 2 is immersed in the etching solution 8 and etched.

Since the current depends on the area of exposed aluminum, near the end point, the aluminum pattern is cut one after another, so the current value decreases rapidly, and you can tell that you are near the end point of etching. . However, since this point is not the end point itself, it is necessary to continue etching. This extended etching time is determined based on past data, but this method requires strict temperature control of the etching solution, control of the mixing ratio of the etching solution, and the like.

The present invention is a novel invention that eliminates the above defects, and in chemical etching that selectively removes a conductive layer attached to a substrate, the conductive layer of the substrate is used as the first pole, and other conductive objects are used as the first pole. The etching rate is calculated from the thickness of the conductive layer and the time required for the current flowing between the two electrodes to become smaller than a set reference current value, and based on the etching rate, the This is accomplished by a method of forming electrical interconnects that has a defined etching time.

Furthermore, the present invention provides an electrical wiring forming apparatus that selectively chemically etches a conductive layer attached to a substrate and is equipped with a device for recognizing the etching state; one pole in contact with the conductive layer, the other pole made of a conductive object made of a material different from the conductive layer, means for measuring the current flowing between the two electrodes by immersing the two poles in an etching solution, and the conductive layer. Etching is performed using a layer initial thickness setting switch, a reference current circuit for determining the etching end point, the initial thickness of the conductive layer, and the time required for the current flowing between the two electrodes to reach a value smaller than the set reference current value. This is achieved by an electrical wiring forming apparatus characterized by comprising a processing device that calculates the rate and determines the overetching time based on the rate, and an overetching film thickness setting switch.

In the method of the present invention, the predetermined current is preferably I ₀ /2 or less with respect to the initial current I ₀ .

SUMMARY OF THE INVENTION An object of the present invention is to provide a method that allows the same etching to be performed at all times, and to provide a method for forming electrical interconnections of high quality.

Still another object of the present invention is to provide a method for forming electrical wiring that is less affected by the temperature and mixing ratio of the etching solution.

Yet another object of the present invention is to provide a method of forming electrical wiring that does not require rigorous experimentation.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the drawings, taking an example of electrical wiring on a semiconductor wafer.

FIG. 3 is a block diagram of an etching bath and an electric circuit according to the present invention.

10 is an amplifier; 11 is a timer; 12 is a switch for setting the initial thickness of the aluminum conductive layer for electrical wiring on the wafer; 13 is a reference current setting circuit for determining whether the terminal is close to the end point; an overetch film thickness setting switch for performing etching, 15 a processing device, 16 a display and a buzzer;
17 is a start switch.

When the wafer 2 is placed in the etching bath 1 and the start switch 17 is pressed, the timer 11 is activated to measure time. The current generated by electrolytic etching is converted into a voltage by a resistor 6, amplified by an amplifier 10, inputted to a processing device, and compared with the value of a reference current setting circuit 13.
When the etching current becomes smaller than the value of the reference current setting circuit 13, the processing device sets the timer 11 at that time.
output T and output W of the initial thickness setting switch 12
, calculate the etching amount per unit time, that is, the etching rate W/T, then read the output W' of the overetch film thickness setting switch 14, and divide it by the etching rate to calculate the overetch time W'/WT. calculate. When the output of the timer 11 reaches T+W'/WT, the processing device turns on the display and buzzer 16 to indicate that etching is complete.

According to the present invention, since the etching rate is calculated for each etching process, it is possible to perform etching by taking into consideration subtle fluctuations in conditions such as fluctuations due to the mixing ratio of etching liquid and fluctuations due to temperature. This enables high-quality etching.

Furthermore, according to the present invention, desired etching can be achieved without the need for many experiments using various conditions.

In the above explanation, the initial thickness setting switch 1 of the conductive layer is
We have described the case in which two sets of switches, 2 and overetch film thickness setting switch 14, are provided, but since the initial thickness W of the conductive layer and the overetch film thickness W' are known in advance, the ratio W'/W can be set. It is clear that the present invention can also be implemented by providing a set of switches.

In the above explanation, the case of electrolytic etching in which a current is forced to flow to promote etching has been described, but the present invention is not limited to this. It is clear that the same method can be realized in which the etching state is recognized by detecting the current flowing due to the voltage generated by the battery action when the etching material is immersed in the electrolytic solution.

FIG. 4 is a sectional view of the semiconductor before etching, and FIG. 5 is a sectional view of the semiconductor after etching.

41 is a semiconductor silicon wafer, 42 is an insulating film such as silicon dioxide, 43 is a vapor-deposited aluminum layer, and 44 is a resist that follows an electrical wiring pattern.

When etching is performed by bringing the aluminum wire 3 into contact with the aluminum layer, the portions of the aluminum layer to which the resist 44 is not applied are removed, as shown in FIG. After removing the aluminum layer to which the resist 44 is not added in this way,
The aluminum wire 4 is removed and the resist 44 is removed in a normal process to obtain electrical wiring in a predetermined pattern.

Although the above description has been made regarding electrical wiring on a semiconductor wafer, the present invention is not limited thereto, and it goes without saying that it can also be used for precision etching including the formation of other electrical wiring.

As explained above, according to the present invention, precise, high-quality, and homogeneous etching can be performed while correcting the effects of changes in the temperature and mixing ratio of the etching solution.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an electrolytic etching tank and an electric circuit, and FIG. 2 is a diagram showing the temporal change in current value when the substrate 2 is immersed in an etching solution 8 and etched.
FIG. 3 is a block diagram of an etching bath and electric circuit according to the present invention, FIG. 4 is a sectional view of the semiconductor before being etched, and FIG. 5 is a sectional view of the semiconductor after etching. 1 is an etching bath, 2 is a substrate, 3 is an aluminum wire, 5 is a platinum wire, 4 is a holder, 6 is a resistor, 7
is a battery, 8 is an etching liquid, 10 is an amplifier, 11
is a timer, 12 is an initial thickness setting switch, 13 is a reference current setting circuit, 14 is an overetch film thickness setting switch, 15 is a processing device, 16 is a display and a buzzer, 17 is a start switch, 41 is a silicon wafer, and 42 is an insulator. Membrane, 43 is aluminum layer, 4
4 is a resist.

Claims (1)

[Claims] 1. In chemical etching for selectively removing a conductive layer attached to a substrate, the conductive layer of the substrate is used as a first pole, and another conductive object is used as a second pole. The etching rate is calculated from the thickness of the conductive layer and the time until the current flowing between the two electrodes becomes smaller than a set reference current value, and the overetching time is determined based on the etching rate. How to form electrical wiring. 2. In an electrical wiring forming apparatus equipped with a device for selectively chemically etching a conductive layer attached to a substrate and recognizing the etching state; bringing an object made of the same type of material as the conductive layer into contact with the conductive layer of the substrate; one pole made of a conductive object made of a material different from that of the conductive layer; a means for measuring the current flowing between the two electrodes by soaking the two poles in an etching solution; The etching rate is calculated from the thickness setting switch, the reference current circuit for determining the etching end point, the initial thickness of the conductive layer, and the time until the current flowing between the two electrodes reaches a value smaller than the set reference current value. What is claimed is: 1. An electrical wiring forming apparatus comprising: a processing device that determines an overetching time based on the overetching time; and an overetching film thickness setting switch.