JPH0562818B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for detecting the end point of etching when patterning a metal layer on a wafer by immersion etching.

2. Description of the Related Art In the manufacturing process of semiconductor devices, there is a process of forming a wiring pattern on a wafer. In such a process, first, a metal layer such as aluminum is deposited on the wafer, and then a resist serving as a mask is patterned on the metal layer. When etching is performed using the immersion etching method, a wafer carrier containing a plurality of these wafers is immersed in an etching bath, and the metal layer not covered with resist is etched.

By the way, in order to detect the end point of the etching when pattern etching the metal layer, first connect one electrode of an ammeter to the peripheral edge of one of the wafers housed in the carrier, and then connect the electrode of, for example, platinum, to the other electrode. The plate and the like are immersed together with the wafer in an etching bath. With this arrangement, a current path is formed through the metal ions flowing into the etchant according to the ionization tendency, so the etching state can be monitored by detecting the current value at this time, and the current value indicates the progress of etching. Taking advantage of the fact that the current value decreases as the current value decreases, the end point of etching is determined when the current value is minimum.

Problems to be Solved by the Invention By the way, in immersion etching, the metal layer is etched from the periphery of the wafer toward the center. Therefore, even if the metal layer near the periphery of the wafer on which the electrode connected to the ammeter is attached is etched, the metal layer near the center of the wafer remains. At this time, the metal layer remaining near the center is not electrically connected to the electrode, so even though the metal layer remains unetched near the center of the wafer, the metal layer near the facet of the wafer is etched. There is no change in the current value when the current value is changed. In this way, with the conventional method, even if the end point of etching is confirmed, it cannot be said that the true end point of etching of the wafer has been detected. Since immersion continues until complete etching is achieved, there is a problem in that if the setting time during this period is incorrect, side etching will proceed and the wiring pattern will become unnecessarily thin.

Therefore, an object of the present invention is to detect the true end point of etching in immersion etching.

Means for Solving the Problems In order to achieve the above object, the present invention uses a wafer for monitoring in which a dissimilar metal layer that is not etched with the same etchant as the metal layer is interposed directly below the metal layer to be pattern etched. One electrode of an ammeter was attached to the peripheral edge of this monitor wafer as a wafer, and the other electrode of the ammeter was positioned near the monitor wafer.
That is, the etching end point of the metal layer was detected with the monitoring wafer and the other electrode of the ammeter immersed in the etching tank. Note that the monitor wafer and the other electrode are located adjacent to each other.

Function Even if the area near the facet of the wafer, that is, the area where one electrode of the ammeter is attached, is etched and the metal layer near the center of the wafer remains, the remaining metal layer will pass through the different metal layer to the ammeter. The current continues to flow until the remaining metal layer is etched.

Embodiment FIG. 1 is an explanatory diagram showing an outline of an embodiment of the present invention.

In the figure, 1 is an etching tank filled with an etching solution. A plurality of wafers 3 housed in a wafer carrier 2 are immersed in the etching bath 1. As shown in FIG. 2, the wafer 3 has a metal layer 31 made of aluminum or the like with a thickness of 1 μm.
In addition, a resist 32 serving as a mask is patterned. Reference numeral 4 denotes a monitor wafer, and as shown in FIG.
A metal layer 42, which is the same as the metal layer 31, is formed to a thickness of about 1 μm, and a resist 43 is patterned in the same manner as the resist 32. That is, the dissimilar metal layer 41 is provided directly under the metal layer 42, and the dissimilar metal layer 41
Each layer except for 3 is formed under substantially the same conditions as each layer formed on the wafer 3 to be etched.

Reference numeral 5 denotes an ammeter, one electrode 51 of which is formed in the shape of a clip, and is attached to the facet portion of the monitor wafer 4. Further, the other electrode 52 of the ammeter 5 is attached to a platinum plate 6 formed in the same shape as the wafer.

Therefore, the wafer 3 and the monitor wafer 4,
Etching is started by immersing the platinum plate 6 into the etching bath 1.

The progress of this etching is shown in Figures 4 and 5.
This will be explained according to the diagram. First, during the immersion time period _t0 to _t1 , etching of the metal layer 42 progresses as shown in FIG. 5a, and the current value based on the amount of etching at that time becomes approximately constant at _i2 . Between the immersion time _t1 and _t2 ,
As shown in FIG. 5b, the metal layer 42 remains in a lumpy state, and the current value gradually decreases from _i2 to _i1 . Then, when the immersion time _t2 comes, the etching of the metal layer 42 is completed as shown in FIG. 5c, and the current value reaches its minimum value at _i1 . Therefore, if this current value i ₁ is set as the current value at the end point of etching, and if the current value i ₁ is checked and etching is completed in advance, the true end point of etching can be detected. I can say that it is. Note that the current value after the immersion time _t2 remains approximately constant at _i1 , but does not show 0. This is because the side etching of the metal layer 42 to be left, that is, the portion that will become the wiring pattern, progresses slightly.

Therefore, if a portion of the metal layer 42 that is not covered with the resist 43 of the monitor wafer 4 remains near the center, the remaining metal layer 42 is electrically connected to the dissimilar metal layer 41 provided directly below it. Therefore, the current value is between i ₂ and i ₁ and does not yet indicate the current value at the end point of etching. However, conventionally, this point indicates the end point of etching, and therefore an estimated time is required for etching the remaining metal layer 42.

In this example, the dissimilar metal layer was described as being formed only on the monitor wafer, but the dissimilar metal layer may be provided on all wafers. In that case, the dissimilar metal layer may be removed by another etchant after the etching of the metal layer is completed. However, since the dissimilar metal layer is formed extremely thinly compared to the metal layer, the wiring pattern is not affected even through an etching process for removing the dissimilar metal layer.

Effects of the Invention As explained above, according to the present invention, when a part of the metal layer remains near the center of the monitor wafer, the remaining metal layer causes a current to flow through the dissimilar metal layer directly below it. Since conduction is conducted to one electrode of the meter, the current value of the ammeter becomes even smaller.
In other words, since the ammeter does not indicate the minimum value until the metal layer has been etched so that no part of the metal layer remains to be etched, the expected time to etch the remainder after detecting the end point of etching as in the conventional method is There is no need to go out of your way to provide one. Therefore, since the present invention can detect the true end point of etching a metal layer, it is possible to easily manufacture a wiring pattern with good reproducibility.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing an outline of an embodiment of the present invention, FIG. 2 is an explanatory cross-sectional diagram of a wafer 3, FIG. 3 is an explanatory cross-sectional diagram showing a monitor wafer 4, and FIG. 4 is an explanatory diagram of immersion time and current. FIG. 5 is a cross-sectional view of the monitor wafer 4 showing the progress of etching. DESCRIPTION OF SYMBOLS 1...Etching tank, 3...Wafer, 4...Monitor wafer, 41...Different metal layer, 42...Metal layer, 5...Ammeter, 51...One electrode, 52...
...The other electrode.

Claims (1)

[Claims] 1 A dissimilar metal layer is formed directly below the metal layer to be etched to form a monitoring wafer, one electrode of an ammeter is attached to the peripheral edge of the monitoring wafer, and the wafer is immersed in the etching tank. The other electrode is immersed in the vicinity of the monitor wafer, the metal layer of the monitor wafer is selectively etched, and the metal layer is etched until the dissimilar metal layer is exposed. A method for detecting the end point of etching, characterized by determining a current value as the end point of etching.