JPH0475332A - Semiconductor manufacturing apparatus - Google Patents

Abstract

PURPOSE:To reduce the labor of a lift-off process by a method wherein an ultrasonic beam which has been converged and expanded by using an acoustic lens is impinged on the surface of a wafer and a region to be removed by the lift-off process is separated by using the beam. CONSTITUTION:The focus of an ultrasonic beam 9 is impinged, by using an acoustic lens, on a resist layer 23, a metal layer 24 or its neighborhood which is to be lifted off. A cracked or stripped region 100 is formed in the lift-off layer 23, 24 by the concentrated ultrasonic power; the removal effect of a resist removal liquid 5 used as a medium is added; the layers are separated and removed from a lift-off spacer layer 22. Even when the ultrasonic beam 9 is scanned in the direction of an arrow 90 and is impinged on the whole region of the surface of a wafer, the ultrasonic power is weakened in the part of a metal-layer pattern 25 to be formed because the beam is defocused. A lift-off operation is executed effectively by this effect and by the difference in the close contact power of individual layers.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to an apparatus for manufacturing semiconductor devices such as integrated circuits or various electronic devices having fine patterns, and particularly relates to an apparatus used in a lift-off process using photoresist.

[Conventional technology]

In FETs and their integrated circuits using compound semiconductors, particularly GaAs, a process called a lift-off process is used to form source and drain ohmic electrodes and gate electrodes. As shown in FIG. 5(a), the metal layers 24 and 25 of the electrode material shown above are deposited on the photoresist pattern 23, and then the photoresist 2
In this technique, a desired pattern is obtained based on the principle of removing unnecessary metal layer 24 at the same time by removing metal layer 24 (FIG. 3(b)). Note that normally, as shown in the same figure, S i 0
A lift-off spacer 22 made of, for example, 2 is used. Conventionally, this process involves: ■ immersing the wafer in a resist removal solution, and ■ using an ultrasonic cleaner to remove unnecessary materials.
Lift-off was performed using the steps of ■ rinsing and ■ drying. However, in the conventional technology, in order to remove the resist under the metal layer with a resist removal solution, the wafer immersion time and ultrasonic cleaning time are long, and this process requires a large amount of work time. Furthermore, in order to shorten the above working time, if the mechanical force of the ultrasonic cleaner is increased too much, the metal layer that is to be left as a pattern will be peeled off along with it. was using the machine. Furthermore, in the conventional lift-off process, the photoresist layer under the metal layer is removed in principle by the resist removal liquid penetrating through the opening of the step and dissolving or peeling off the resist, so that the photoresist layer under the metal layer is removed from a large resist area. Another drawback was that it was very difficult to lift off. For this reason, it is necessary to repeat the steps of immersion in a resist removal solution and ultrasonic cleaning several times, which requires excessive manpower and becomes an obstacle to mass production.

[Problem to be solved by the invention]

An object of the present invention is to provide an apparatus that can perform a lift-off process with labor savings.

[Means to solve the viA problem]

In order to achieve the above object, in the present invention, an apparatus is constructed based on the principle that an ultrasonic beam that can be converged and expanded by an acoustic lens is applied to the surface of a wafer, and a region to be removed by lift-off is separated by the beam.

[Effect]

Since the ultrasonic energy is concentrated near the focal point of the ultrasonic beam, when this is placed on the photoresist on the wafer surface, this area will separate or crack. If the depth of focus of the ultrasonic beam is small compared to the lift-off step, if the focus of the beam is scanned to match the photoresist layer, only the region desired to be lifted off will be easily separated by the force of the ultrasonic wave. When the lift-off step is small, the beam is selectively scanned only to a certain area of the photoresist. Here, if a photoresist removal solution is used as the ultrasonic propagation medium, lift-off becomes easier. By using ultrasonic waves having a wavelength that is comparable or less than that of the lift-off step, it is possible to distinguish between areas that should be lifted off and areas that should not be lifted off, based on the phase of the ultrasonic signal reflected from the surface. In addition, the acoustic impedance of the photoresist is much smaller than that of the semiconductor substrate and is close to that of the removal solution, so the intensity of the reflected signal in the area where the photoresist is attached is smaller than that in the area where the photoresist is not attached. Therefore, it is possible to distinguish between areas that should be lifted off and areas that should not be lifted off also based on the intensity of the reflected signal. Therefore, by receiving the ultrasonic waves reflected from the wafer surface and monitoring this information, or by feeding it back to the ultrasonic beam oscillator, lift-off can be performed under optimal conditions. Furthermore, by controlling the ultrasonic wavelength to about four times the thickness of the photoresist, it is possible to cause a resonance phenomenon in the photoresist portion and perform lift-off with high selectivity and efficiency. [Example] The present invention will be described in detail below. FIG. 1 shows a basic diagram of an apparatus according to an embodiment of the present invention for removing photoresist during a lift-off process. This device includes a part 6 that fixes a wafer 10 and can rotate and move, its controller 7, and a solution 5 that applies an ultrasonic beam (formed by 1 and 2) to a lift-off layer 12 on the wafer surface.
This state is monitored through 4. It is basically configured with 8 controllable parts. FIG. 2 shows the principle of lift-off performed by this basic configuration. The ultrasonic beam 9 is focused by an acoustic lens on or near a portion of the resist layer 23 and metal layer 24 to be lifted on. This concentrated ultrasonic force causes cracks or peeling areas 100 in the lift-off layers 23 and 24.
is formed, and is separated and removed from the lift-off spacer layer 22 with the added removal effect of the resist removal liquid 5 used as a medium. Even if the ultrasonic beam 9 is scanned as shown by the arrow 90 and applied to the entire wafer surface, the ultrasonic power becomes weak in the part where the metal layer pattern 25 is to be formed due to the defocus of the beam, and this effect and the above-mentioned Lift-off is performed effectively because of the difference in adhesion between the layers. The lift-off conditions in this example are shown below. (1) Related sample: GaAs semiconductor substrate; 450 pm thickness Si
O2 spacer layer thickness: o, 7 μm Photoresist thickness: 2 μm
m A u G e alloy metal layer thickness; o, 3 μm. (2) Ultrasonic relationship: Frequency: 2GH7 Output: 1ook/cm2 Beam diameter at focal position: 1 μm Depth of focus: 1 μm Beam moving speed: 1 cm/s Solution: Resist removal liquid Another embodiment according to the present invention is shown in FIG. show. In this embodiment, the ultrasonic beams 32' are linearly arranged and scanned over the wafer 12 in the direction of an arrow 34 to improve throughput. The wafer is set rotatably as shown by the arrow 35, and is spun on with the lift-off layer together with the solution. Yet another embodiment according to the invention is shown in FIG. This figure is an enlarged view of a portion of the wafer surface, showing the state after selective scanning with an ultrasonic beam. A lift-off layer 42 and a metal layer 4 are formed on the surface of the wafer 40.
1 and the area 44 scanned by the ultrasound beam.
is indicated by diagonal lines. This is because the sample that requires such scanning has a thin resist with a thickness of about 1 μm or less, and the intensity of the focused ultrasonic beam is too strong, which adversely affects the metal layer pattern 41. The beam is operated in correlation with the pattern position on the wafer. Although the embodiments of the present invention have been described above, the scope of application of the present invention is not limited to the case of a cylindrical lens as in the embodiments, but also extends to the case of using a spherical lens. Furthermore, it goes without saying that the scope of application of the apparatus of the present invention is not limited to the lift-off process, but is also effective in a normal resist removal process. Further, the present invention has been described above by showing an example in which pattern formation by lift-off is performed on a semiconductor wafer.
It should be added that the scope of the present invention is not limited to this. [Effects of the Invention] Since the present invention is configured as described above, it has the following effects. (1) The lift-off process has been changed from the conventional random method.
Since the method has been changed to the controlled method according to the present invention, it is possible to completely eliminate defects in the work. (2) Since the lift-off layer on the wafer surface is reliably removed by ultrasonic force, the working time can be significantly shortened (about 1/10) compared to the conventional method. (3) This device is used to transport wafers, ■transfer mechanism, ■cleaning mechanism,
Since it can be used in combination with a drying mechanism to form an integrated lift-off device, the process can be automated to save labor and time, making mass production possible.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a device according to an embodiment of the present invention, FIG. 2 is a diagram explaining the principle of the present invention, FIG. 3 is a block diagram of a device according to another embodiment of the present invention, and FIG. FIG. 5, which is a plan view of the wafer surface according to the embodiment, is a diagram explaining the principle of pattern formation by lift-off. Explanation of symbols 1... Ultrasonic vibration element 2... Acoustic lens 5... Solution (medium) 6... Sample stage 9... Ultrasonic beam 10... Wafer 23... Photoresist layer 24. 25...metal layer

Claims (1)

[Scope of Claims] 1. A semiconductor manufacturing apparatus that forms a desired pattern shape by lift-off, and is characterized in that the lift-off is performed by applying at least a focused ultrasonic beam to the surface of a wafer. 2. The semiconductor device according to claim 1, further comprising a mechanism for converging the ultrasonic beam so as to destroy the lift-off resist layer and moving the ultrasonic beam or the wafer to scan the beam. Manufacturing equipment. 3. The semiconductor manufacturing apparatus according to claim 1 or 2, further comprising a mechanism for receiving an ultrasonic reflected signal and a mechanism for controlling lift-off processing in accordance with the received signal. 4. The semiconductor manufacturing apparatus according to claim 1, 2 or 3, wherein the range in which the ultrasonic beam scans the wafer surface is the entire surface of the wafer. 5. The semiconductor manufacturing apparatus according to claim 1, 2 or 3, wherein the range in which the ultrasonic beam scans the wafer surface is at least a portion excluding a pattern formed by lift-off. 6. The semiconductor manufacturing apparatus according to claim 1, 2, 3, 4 or 5, wherein the ultrasonic wavelength is substantially equal to four times the thickness of the resist layer to be lifted off.