JPS6284536A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To form a uniform aluminum wiring onto a semiconductor device by monitoring the status of anodic oxidation by an electrical means. CONSTITUTION:Positive potential is applied to a semiconductor substrate 1 and negative potential to an aluminum electrode 5 in an oxalic acid aqueous solution 3 by an DC power supply 6, thus anodic-oxidizing an aluminum film 15 on the semiconductor substrate 1. A measuring signal 11a from an ammeter 11 is inputted to a control section 13 when some time passes, and the control section 13 compares the measuring signal with a current value where the extent of the reduction of currents is set previously. When the presence of leakage currents is decided, a signal 12a is transmitted over a switch 12 and a current circuit is interrupted, and anodic oxidation processing is stopped. The signals 11a is inputted to the control circuit 13 again at an oxidation-completion set time, and the circuit 13 compares the signal 11a regarding the reaching of the signal 11a to a reference current value or less. When a reference is not satisfied, the signal 12a is outputted after only the prolongation time determined from a comparison with the reference value passes, and the current circuit is interrupted.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method of manufacturing a semiconductor device, and particularly to a method of forming aluminum wiring by an anodic oxidation method.

[Conventional technology]

Formation of aluminum wiring using conventional anodic oxidation method
This will be explained with reference to the figures and FIG.

As shown in FIG. 3(a), after the aluminum film 15 is entirely deposited on the semiconductor substrate 1, the aluminum film 15 is anodized for a predetermined time in an anodizing bath filled with an oxalic acid aqueous solution to thin the surface. The quality of the alumina layer 14 is changed. This is a rounding process that improves the adhesion of the photoresist film in the next step. A photoresist pattern 16t” is formed by patterning a photoresist on the alumina layer 14.
Shape ff. This semiconductor substrate 1 is placed facing an aluminum electrode 5 in an anodic oxidation tank 4 shown in FIG. Do this. Figure 3 (
As shown in b), the aluminum film 15 in other parts except the part covered with the photoresist pattern 16 is anodized and changed to alumina 18), and the photoresist pattern 1
6. Aluminum wiring 17 is formed in the portion where f81 is removed.

[Problem that the invention seeks to solve]

In the above-mentioned anodic oxidation method, the anodization time is set to a fixed time using a timer switch, so depending on the type of semiconductor substrate, the finish of the aluminum wiring may vary, as shown in Figure 3(e). This results in a lack of anodization as shown. Furthermore, if current leaks from a part of the semiconductor substrate, it cannot be detected, and therefore aluminum wiring is not formed in some parts, resulting in defects.

SUMMARY OF THE INVENTION An object of the present invention is to provide a manufacturing method capable of eliminating the above-mentioned drawbacks and forming uniform aluminum wiring by monitoring the anodic oxidation status by electrical means.

[Means for solving problems]

The present invention detects the current flowing through the semiconductor substrate at a time between the start of anodic oxidation and a predetermined oxidation end point in the process of forming aluminum wiring on a semiconductor substrate by an anodizing method, and detects the current flowing through the semiconductor substrate. Determining the presence or absence of leakage current from the decreasing situation, and detecting the current flowing through the semiconductor substrate at the oxidation end setting point,
Insufficient anodic oxidation is determined from the current reduction situation and oxidation is continued additionally.

[Effect]

As the anodic fermentation progresses, the current gradually stops flowing.

This is because less aluminum is anodized.

Therefore, the current flowing through the semiconductor substrate at the end of the anodizing process is checked in advance, and if the current value decreases after a predetermined end setting time and reaches the current value, the electric circuit is cut off and the anodizing process is stopped. .

In addition, leakage current from the semiconductor substrate is detected because the current flowing through the semiconductor substrate should have decreased by a specified amount after a predetermined amount of time as anodic oxidation progresses, but the current value has not decreased by that amount. It is possible. Therefore, if the current value decreases after a predetermined time and does not reach the above current value, leakage current is occurring from somewhere on the semiconductor substrate, so cut off the electric circuit, stop the anodizing process, and investigate. .

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a diagram showing an example of an anodizing apparatus to which the present invention is applied. A semiconductor substrate 1 treated with oxalic acid (FIG. 3) is placed on the liquid level of an anodic oxidation tank 4 filled with an aqueous oxalic acid solution 3, and oxalic acid is sprayed onto the upper surface of the semiconductor substrate 1 from a jet hole 2 using a jet pump 10. The aqueous solution is poured in. At the same time, the DC power supply 6 applies a positive potential to the semiconductor substrate 1 and a negative potential to the aluminum electrode 5 submerged in the oxalic acid aqueous solution 3, thereby anodizing the aluminum film 15 of the semiconductor substrate 1.

In this device, an ammeter 11. A control section 13 is provided which inputs the measurement signal 11a of the switch 12 and the ammeter 11 and outputs a signal 12a for turning the switch 12 on and off. The control section 13 has a timer and a current value comparison means, and as shown below, detects the anodic oxidation status based on temporal changes in the current value and controls the switch 12.

First, check for leakage current. After a certain period of time has elapsed, the control section 13 inputs the measurement signal 11a from the ammeter 11, and compares the degree of decrease in current with a set current value. For example, if the current value is 115 as a reference, and the current value is thicker than this value, it is determined that there is a leakage current, and the signal 1 is
2) Turn a to switch 12 to cut off the current circuit and stop the anodizing process. Since the alumina layer is transparent, the semiconductor substrate 1 can be taken out and observed under a microscope to confirm the progress of anodic oxidation and to investigate the cause of leakage current.

On the other hand, if the leakage current check satisfies the criteria, anodic oxidation is continued until the oxidation end set time.

At the set oxidation end time, the control circuit 13 again outputs the current measurement signal 1.
Input 1a and compare whether the current value is below the reference current value (for example, the current value of one excess of the starting current).

If this criterion is not met, the switch-off signal 12
A is not outputted immediately, but is outputted after an extension time predetermined from comparison with a reference value has elapsed, and the current circuit is cut off.

〔Effect of the invention〕

As described above, if current leaks from a part of the semiconductor substrate, it can be detected before the anodization is completed, and an accident in which part of the aluminum wiring is not formed can be prevented. Furthermore, by detecting the current and performing additional anodic oxidation at the set point of completion of the anodization, it is possible to reduce variations in the finished product of aluminum interconnection formation. Therefore, it is possible to improve the yield and reduce the number of man-hours.

[Brief explanation of drawings]

FIG. 1 is a diagram for explaining an embodiment of an anodizing device to which the present invention is applied, FIG. 2 is a conventional anodizing device corresponding to FIG. 1, and FIG. 3 is an illustration of forming aluminum wiring by anodizing. FIG. 2 is a cross-sectional view of a semiconductor substrate for explaining. 1... Semiconductor substrate, 2... Jet hole, 3...
Control unit, 4... Anodizing tank, 5... Aluminum electrode, 6... DC power supply, 10... Jet pump, 11... Ammeter, 12... Switch, 13...
...Control unit, 15...Aluminum film, 16...Photoresist pattern, 17...Aluminum wiring, 18...Alumina.

Claims (1)

[Claims] In the process of forming aluminum wiring on a semiconductor substrate by an anodizing method, a current flowing through the semiconductor substrate is detected at a time from the start of anodization to a predetermined oxidation end point, The present invention is characterized in that the presence or absence of leakage current is determined based on the state of current decrease, and at the time when the oxidation end is set, the current flowing through the semiconductor substrate is detected, and insufficient anodic oxidation is determined from the state of current decrease, and oxidation is additionally continued. A method for manufacturing a semiconductor device.