JPS60124942A - Terminal detection mechanism for wet etching - Google Patents

Abstract

PURPOSE:To facilitate the automation of the etching process by a method wherein, in the wet etching of a metal thin film of Al, Al-Si, or the like formed on a semiconductor wafer, a reflection system photosensor is arranged in proximity to the thin film; thereby, the output signal according to the amount of reflected light from the thin film is obtained, and the finish of etching is judged by the variation of this output. CONSTITUTION:The upper part in an etching device 1 having an exhaust duct 2 is povided with a draft 4 having an illuminating device 3 on the lower surface, and the bottom is provided with a liquid circulator 11 incorporating a heater 10 for etchant temperature adjustment. A flow-down bath 6 having an inclined plane 5 along which an etchant 7 flows down is provided between the draft 4 and the circulator 11; a wafer transfer mechanism 8 is installed on this inclined plane 5, and a wafer 9 supported thereby is etched as required while being slid over the inclined plane 5. At this time, the photosensor receiving the amount of reflected light of light beams is provided on the wafer 9, and the etching is judged as finished at the time of the change of the output signal according to the amount of reflected light.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention is applicable to the semiconductor wafer manufacturing process.
The present invention relates to a wet etching detection mechanism for detecting the end point of etching, which is incorporated into a wet etching apparatus that performs etching operations for forming patterns such as electrode patterns on thin metal films such as -8i.

[Background of the invention]

Thin film etching methods can be roughly divided into wet methods that use acid or alkali aqueous solutions, and dry methods that use ion beams or plasma containing some reactive gases. In the process of forming patterns for transistor parts, electrode wiring, etc. in the wafer manufacturing process, higher and higher densities and higher precision are being promoted. It is considered the most important of all semiconductor processes, and the equipment used in it is required to be extremely precise.

The means for highly precise pattern formation of thin films is being shifted from wet etching, which was once the mainstream, to dry etching. However, among various thin films, AI
To dry-etch metal coatings such as Al-8T, chlorine-based CC1 gas is often used as the reaction gas, and Cl-ion may remain in the surface even after cleaning, impairing the properties. However, it had the disadvantage of corroding the vacuum system of the device.

Therefore, wet etching using acid or alkali is preferable for etching metal films such as Al and Al-8i, but in this case, quality control is difficult even though most wafer processing equipment is mechanized. There are few examples in which the determination and detection of the etching end point, which is a key point, is automated, and the actual situation is that the process is performed manually, relying on visual determination by an operator.

In general, compared to Si, N4, PSG films, etc., the A6 film has the characteristic that the amount of reflected light is the largest when irradiated with the same amount of light beam, and when the underlying layer begins to be exposed at the etching end point. Easiest to identify. However, like many other etching solutions, the etching group used for etching Al films is a strong acid solution and requires a draft device. Therefore, automation of the work is desirable from the standpoint of safety and quality control. .

[Objective of the Invention 1] The object of the present invention is to provide a wet etching method that can reliably determine and detect the etching end point and automate the etching process when wet etching a metal film formed on a semiconductor wafer. The purpose of the present invention is to provide a termination detection mechanism.

[Summary of the invention]

The present invention relates to aluminum formed on a semiconductor wafer.

When wet etching a metal coating such as A7-8i, a reflective photosensor is placed close to the metal coating on the semiconductor wafer, and the output of this photosensor is used to generate an output signal corresponding to the reflected light from the metal coating. The wafer transfer mechanism is characterized in that the end point of etching is determined based on a change in the output signal according to the amount of reflected light, and the wafer transfer mechanism is operated.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIG. The etching apparatus 1 has an exhaust duct 2 and is constantly supplied with 4JF air from a draft upper part 4 equipped with an illumination device 3. The lower part of the draft upper part 4 has a flow tank 6 having an inclined surface 5.
is arranged, and the ethotic liquid 7 flows down along the inclined surface 5. In the middle part of the slope 5 is a sea urchin transfer mechanism 8.
A plurality of machines are provided on the left and right sides of the upper F1, and they operate simultaneously, and they perform a machine 11 that moves the sea urchins back and forth between the etching section and the washing section. F' of downstream tank 6
) A liquid circulation mechanism equipped with an etching heater lO] 1 is provided.An operation panel 12 is provided on the front surface of the apparatus 11.

The operating procedure of the etching apparatus is as follows: First, the cleaning section side wafer transfer mechanism 8 is arranged in parallel on the tilting barrel +15 of the downstream tank 6.
Place the wafer 9 on the support arm of the device and
Operate the operation panel 12 that has been set up and immerse it in the etching solution 7 made of an aqueous solution containing phosphoric acid, acetic acid, and nitric acid.
The progress of etching is checked by the brightness of the wafer 9 reflecting the illumination light from the illumination device 3 provided in the upper part of the draft 4, and when the etching of the Al film is completed, the etching is transferred to a cleaning solution.

Since the above-mentioned etching time is a short time of several minutes, it is necessary to strictly suppress fluctuations in determining the end of etching, so the number of sheets processed at one time is limited. In order to accurately determine the end of etching, an etching end determination mechanism and a control circuit are provided in conjunction with the sea urchin transfer mechanism 8.

FIG. 2 shows this etching end determination mechanism, and FIG. 3 is a diagram showing the control system including the detection of etching amount determination and wafer/transfer. The I mounting table 20 is provided with a sea urchin fixing groove 21, and a transfer throat 22 in which the sea urchin I9 is set is attached to this portion. Ueno 9 and Uni I
- The etching group 7 is flowing down on the platform 20. Opposed to the sea urchin 9 placed on the etching section, a reflective photosessor 23 made of a light-emitting diode with an optical fiber moves coarsely in a direction perpendicular to the surface of the sea urchin 9, and faces the sea urchin 9. A sensor drive head 244 that moves slightly in parallel is fixed, and a detection head 26 that receives the reflected beam of the original beam 25 irradiated from the photosensor 23 onto the sea urchin I9.
It is equipped with an amplifier 27 for amplifying the received light output.

The device that activates the etching end detection mechanism is the mounting table 2 A-r-/ having the fixed a21.
・9 is the support arm 2 attached to the wafer transfer mechanism 8
2 and then drive head 24 of sensor 23
is lowered to a predetermined position, for example, a distance of 30 meters, and if! t
A) With the wafer 94 head surface kept parallel so as to receive an average of 25 light beams from 1 MII pattern.
Rotate or move from side to side. The wafer has fine patterns and unevenness, and the k formed on the E
Since there is a difference in the amount of reflected light in the film at microscopic positions, it is necessary to move the inspection sensor slightly. It depends on the surface condition being etched, the concentration and temperature of the etching solution.As the etching progresses, the reflected light received by the photosensor 23 changes as shown in Figure 3, and suddenly near the end of the etching solution. Changes to

On the other hand, in etching, in order to prevent the formation of residues of the ruptured etching film, etching is usually carried out for a few seconds to the extent that it does not affect the pattern dimensions, the shape of the edges, or the properties of the base film. It is common to add Therefore, the control circuit detects a sudden change in the light receiving output of the photosensor 23 at the time t. From the time t set by the timer.

When this is reached, a signal is sent to the drive circuit of the wafer transfer mechanism 8 and the photosensor 23, the photosensor 23 is pulled up, and the wafer 9 is moved to the cleaning side. 1. -10 is the overetching time.

In addition, even when a plurality of transfer ends 22 are connected to one sea urchin/S transfer mechanism 8 in this apparatus, if the etching liquid 7 flowing down forms a uniform laminar flow, the sea urchin to be etched is - Since there is little variation in the etching speed, one photosensor 23 is sufficient to achieve the purpose.

〔Effect of the invention〕

According to the present invention, a reflective photosensor is provided close to the metal film formed on the semiconductor sea urchin/S, and the end point of etching is determined based on the change in the output signal according to the amount of reflected light from the metal film. Since the configuration is such that the transfer mechanism is activated, the etching process can be fully automated by arranging robots for automatic feeding and discharging to the cassette containing the sea urchins, the sea urchin I, and the transfer mechanism IWI. can be achieved.

In addition, even when workers supply and carry out ueno,
It is possible to carry out reliable etching end detection by continuously using any transfer and detection unit for one cycle, and it has the advantage that it is possible to process a large amount of wet material with extremely high etching accuracy.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing one example of a wet etching apparatus incorporating the etching end detection mechanism according to the present invention, and FIG.
The figure is a diagram showing the relationship between the final firing time of the process link according to the present invention and the amount of reflected light. 6... Armpit tank, 7... Etching liquid, 8... Sea urchin... Transfer mechanism, 9... Sea urchin..., 23... Reflective photo sensor, 24... Sensor drive head.

Claims (1)

[Claims] When wet etching a metal film such as AI or Al-8T formed on a semiconductor wafer, a reflective photosensor is placed close to the metal film on the semiconductor wafer, and the output of this photosensor is used to remove the metal film from the metal film. Wet etching is characterized in that it has a function for obtaining an output signal according to the amount of reflected light, and the end point of etching is determined based on the change in the output signal according to the amount of reflected light, and the wafer is transferred. end detection mechanism.