JPS59139630A - Detector for completion of etching - Google Patents

Abstract

PURPOSE:To automate processes easily, to apply the titled detector without depending upon the electrode structure of an IC and to improve safety and productivity by providing a treating tank executing etching treatment, a degassing tank, a drier, a pump sucking a generated gas and a hydrogen gas detector. CONSTITUTION:A large number of semiconductor slices 20 coated with aluminum layers to be treated according to a pattern and photo-resist layers of a predetermined pattern are arranged in a treating tank 22 together with an etching liquid 21. A de-atmosphere tank 23 absorbs an acid (a phosphoric acid group) in a gas generated in the etching treating tank 22. The de-atmosphere tank 23 is connected to a vacuum pump 26 through a drier 24 for absorbing moisture and a hydrogen detector 25. The hydrogen detector 25 is connected to a micro-computer 28 through an amplifier 27 amplifying a detected signal. When aluminum is etched completely, the maximum point of a detecting level of the hydrogen detector 25 is detected by the micro-computer 28, and the end point of etching can be confirmed.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an apparatus and method for automatically detecting the end of an aluminum etching process.

BACKGROUND OF THE INVENTION Aluminum wiring is widely used for interconnection of semiconductor devices such as integrated circuits (ICs) due to its good conductivity, ease of processing, and low cost.

After the final diffusion step of the IC manufacturing process, this wiring is formed on an insulating film such as silicon dioxide in order to interconnect predetermined semiconductor elements, and an etching process is performed on the aluminum layer to give a predetermined pattern. It is carried out against.

This etching process for pattern formation is becoming an increasingly important processing step as the degree of integration of ICs increases and the line width of interconnection wiring becomes narrower. In particular, in order to obtain aluminum interconnections with extremely narrow line widths, the end of the etching process must be precisely controlled.

Description of the Prior Art Currently, there are two methods of etching aluminum: wet and dry. The dry etching method has many advantages, but (1) non-uniform reaction progress due to the alumina (A1203) layer on the surface, (2) contamination of the metal surface by 01 gas, and (3) the next step. Wet etching is widely used in mass production of ICs due to problems in covering steps.

However, in wet etching, it is important to accurately detect the end point, and recently an apparatus for detecting the end of etching of aluminum has been developed. Recent end point detection devices can be classified into contact type and infrared light type.

The principle of the contact-type etching completion detection device is to utilize the change in the electrode potential of aluminum, and has a configuration as shown in FIG. A large number of semiconductor slices 2 are arranged in an etching bath 1, and platinum electrodes 3, 4 are placed inside the etching bath 1.
It is immersed in an etching solution 5 along with the above.

An aluminum layer and a photoresist mask are formed on the surface of the semiconductor slice 2. While the aluminum is being etched, hydrogen replacement takes place, so a voltage of about 1.6 volts is detected by the voltmeter 6 as shown in FIG. When a predetermined amount of etching is completed, the hydrogen substitution is completed and the potential difference between the platinum electrodes 3, 4 drops to near O volts.

This voltage change is read and the etching process is completed. As a technique in this field, the technique disclosed in Japanese Patent Application Laid-Open No. 55-46567 can be referred to.

In such a contact type end point detection device, the detection electrode 3 must be brought into direct contact with at least one semiconductor slice in the etching bath 1, which makes it difficult to automate the device and has low productivity. . Still IC
Depending on the structure, this method may not be applicable. For example, in the case of bipolar ICs, those with a structure in which there is a lower metal layer such as a titanium-tungsten layer (alloy or mixed layer) under the aluminum layer are good because electrons are transported through this layer, but normally, there is no such layer. In this IC, if the part of the platinum electrode 3 where the contact is located is etched first, it becomes impossible to accurately detect the end point of the etching of the internal aluminum layer that is not electrically connected to this part.

The principle of the second infrared light type end point detection device utilizes the fact that the transmittance of infrared light changes depending on the presence or absence of aluminum, and has a configuration as shown in FIG. The semiconductor slices 10 are placed on a rotary table 12 connected to a scrubbing motor 11, and an etching solution is sprayed onto each slice 10 by a spray method. rotating slice 10
An infrared light emitting diode 13 and a photodiode 14 for receiving and detecting this light are provided on both sides of the outer periphery of the etching.As the etching progresses, an amplifier 15 detects changes in the transmittance or shielding property of the infrared light (Fig. 4). and optically detected using a voltmeter 16.

However, this infrared light method also has problems.

Semiconductor slices have different infrared light transmittances depending on their manufacturing process or manufacturer.

When one device is used for different slices,
The setting of the transmittance must be changed each time, which is an obstacle in automating the process and makes it impossible to improve productivity.

Contrary to the contact method mentioned above, if there is another metal layer (Ti:w) under the aluminum layer, the transmission of infrared light will not change even after the etching of the aluminum is finished, so this type of structure is This infrared light method cannot be used with existing ICs. Another disadvantage of this system is that the equipment itself is the same price.

OBJECTS AND SUMMARY OF THE INVENTION The present invention has been made in view of the problems of the prior art, and provides an aluminum layer that is easy to automate the process, can be applied regardless of the electrode structure of IC, is safe, has little variation, and has high productivity. The present invention provides an etching end point detection device.

Example An etching completion detection mechanism according to the present invention is shown in FIG.

A number of semiconductor slices 20, on which are deposited an aluminum layer to be patterned and a photoresist layer of a predetermined pattern, are placed in a processing bath 22 together with an etching solution 21. As shown in FIG. This processing tank 22 has a hole that receives the atmosphere from the outside, and its upper part is connected to a deatmosphere tank 23 through a pipe. This deatmosphere tank 23 is a tank that absorbs acid (phosphoric acid type) in one gas generated in the etching treatment tank 22.

The deatmosphere tank 23 is equipped with a dryer 24 for further absorbing moisture.
It is connected to a vacuum pump 26 via a hydrogen detector 25. Although a metal oxide semiconductor gas sensor that utilizes gas adsorption is used as the hydrogen detector 25, other gas sensors may also be used.

This type of gas sensor is used in toxic gas alarms, etc., and a potential barrier that limits conductivity exists at the grain boundaries of sintered metal oxides due to the adsorption of oxygen in the atmosphere. It has the function of detecting and measuring changes in conductivity due to changes in the height of the potential barrier due to the reaction between this oxygen and various gases.

The hydrogen detector 25 includes an amplifier 21 that amplifies the detected signal.
It is connected to the microcomputer 28 via.

Hydrogen gas is generated from the treatment tank 22 in proportion to the progress of etching the aluminum layer in the treatment tank 22. When etching of aluminum is completed, the amount of hydrogen gas detected decreases from that point to the highest point. Therefore, the etching end point can be determined by the microcomputer 28 by detecting the highest point of the detection level of the hydrogen detector 25.

Microcomputer 28 that informs the end point of etching
In response to the output 1~, the lid of the processing tank 22 is opened, and the slices 20 and the basket containing the slices 20 are taken out of the processing tank and transported to the next cleaning step. This operation can be performed automatically using a small robot that operates in response to the output of the microcomputer 28. An external view of this small robot 30 is shown in FIG. The arm 31 of the robot 30 is
A basket (or board) on which slices are placed is placed in a loading/unloading section 33 that is arranged to be operated with respect to the processing tank 22, the steaming slice drying tank 32, and the basket loading/unloading section 33. -) ff:, robot 3
When processing such as etching and washing is completed, the basket is placed in the drying tank 32 in response to the output of the microcomputer 28.
Set to . The dried slices are returned to the side load/unload section 33 by the arm 31 of the robot 30 while remaining in the basket.

If the hydrogen detector 25 is directly connected to the outlet pipe of the etching tank 20, which is different from the configuration shown in FIG. 5, it may take a long time for the detection level to return to zero after one etching process. Understood.゛It was also found that the detection level after the second time was very unstable. This seems to be because the hydrogen detector 25 was corroded by acid and malfunctioned.

A deatmosphere tank 23 is located between the processing tank 22 and the hydrogen detector 25.
and a dryer 24, and a true gun pump 26 is installed behind the hydrogen detector 25 to forcibly suck the gas generated in the processing tank 22, thereby approximately doubling the hydrogen detection capability (detection signal level). However, since the acid component did not adhere to the detector 25, stable hydrogen detection was possible. This provides a very significant benefit in continuous etching of aluminum.

FIG. 7 shows the functions of the microcomputer 28. This microcomputer 28 is the engineering 10 interface 4
0, the hydrogen detector 25, the temperature sensor 41 provided in the processing tank 22, etc., the mechanical control 42 of the arm 31 of the robot 30, the pulp 43 of the processing tank 22, the pulp 44 of the drying tank 32, the loading/unloading section (or loader) 33, a heater 45 of the drying tank 32, etc., and controls these operations according to a program. The microcomputer 28 further includes a servo system printed circuit board 46 and a servo system amplifier circuit 4.
7 controls the movement axis 48 of the robot 30. Further, the spin rotation 51 within the drying tank 32 is controlled via another servo system printed circuit board 49 and an amplifier circuit 50.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram of a contact-type etching end detection device according to the prior art, Figure 2 is a time change diagram of the voltage detected by the voltmeter of the device shown in Figure 1, and Figure 6 is an infrared ray according to the prior art. FIG. 4 is a schematic diagram showing a temporal change in the output of the amplifier shown in FIG. 6, FIG. FIG. 5 is an external view of a small robot that operates in response to the output of the microcomputer, and FIG. 7 is a diagram for explaining the functions of the microcomputer shown in FIG. Representative Asamura Akigai 4 people Figure 1 Wa 11゜0

Claims (1)

[Claims] a processing tank for performing an etching process on semiconductor slices; a deatmosphere tank connected to the processing tank; a dryer connected to the deatmosphere tank; a pump for sucking gas generated in the processing tank; A device for detecting the end of etching, comprising a hydrogen gas detector provided between a device and the pump.