DE102004054658B3 - Static megasound cleaning system for cleaning substrates, has outer basin with four side walls with acoustic irradiation surfaces, where each surface is responsible for treatment of only small partial area of entire substrate surface - Google Patents

Abstract

The system has an outer basin with front and rear walls, and four side walls that are angled to each other. Each of the acoustic irradiation surfaces (A, B, C, D) is fitted to each side wall, where an acoustic irradiation of a substrate (1) to be treated takes place, from four different lateral directions, by using megasound generators (4). Each irradiation surface is responsible for treatment of only a small partial area of the entire substrate surface. An independent claim is also included for an operating software for a static megasound cleaning system.

Description

For the future semiconductor technology It is necessary to impurities on semiconductor substrates effectively clean, without the on the substrates located fine Structures thereby become damaged. The substrates are mostly disc-shaped objects, which usually have fine structures on one side.

These Substrates are successively in diverse semiconductor manufacturing Immersed in process tanks filled with liquid. For support In addition, these wet-chemical process steps become physical with megasonic vibrations acted on the substrates. The frequency used in megasonic cleaning systems is usually in a range of> 700kHz. By the combination of chemical and physical treatment the substrates it is possible to remove the smallest particles from the substrate surface.

It is proven to increase with the megasonic performance not only the cleaning efficiency but also the degree of damage the fine structures increases. Because the structures on the substrates future ever smaller dimensions have, bump conventional Cleaning systems with megasonic support for some applications already at your limits, because of a certain minimum megahall performance on the substrates must be applied to a good particle cleaning effect to achieve. However, this minimum megasonic power is already large enough for structure sizes <100nm, around the fine structures on the substrates due to the megasonic caused cavitation effect implosion of unresolved gas bubbles in the cleaning liquid) to damage. Thus, in conventional Megasonic systems with high cleaning efficiency a corresponding high degree of damage structures are accepted.

Out US 6026832A discloses an ultrasonic cleaning device, cleaned at the substrates in an inner container by means of ultrasound generated by ultrasonic generators attached to an outer container are. For transmission of the ultrasound are the inner container as well as the outer container with Fluid filled. The ultrasonic generators can alternately, to avoid interference, be switched off. For generating a mutual multi-directional vibration field be several ultrasonic generators on different sides of the container attached and operated at the same time, which means an increase in intensity for the total field.

In the currently existing indirectly sonicated megasonic cleaning systems, such as in 3 and 4 most of them are liquid-filled quartz glass inner bowls 3.3 into which a cassette 3.6 with the substrates to be treated 3.1 is dipped. The liquid of the inner basin 3.3 can z. Example, be a chemical that is particularly suitable for the detachment of the particles to be removed on the substrate surfaces. The indoor pool 3.3 sits in an outdoor pool 3.2 Depending on the design, megasonic surfaces MS on the ground ( 3 ) or on the two side walls ( 4 ) and which is filled with a liquid used as a transfer medium. The megasonic waves are usually one-sided from below ( 3 ) or from two sides ( 4 ) via a transfer medium into the inner process tank 3.3 introduced through the quartz glass wall. The Quarzglaswandung has a defined angle θ to the sound surface and a defined wall thickness t with respect to the megasonic frequency f, so that almost all the megasonic power through the quartz wall into the inner pool 3.3 and thus on the substrates to be cleaned 3.1 gets without being changed in the direction.

Formel 1 The familiar formula is:

formula 1

At the in 4 shown known embodiment, for example, only two sides megasonic introduced so that the direction of the sound waves of both opposite sound surfaces MS by entering the cleaning basin 4.3 be broken so that they meet at an angle of not equal to 180 °. Since this is only sonicated from two sides, the Megaschalleistung each sounding side must be chosen so large that each at least half of the substrate surface 4.1 is cleaned by them. The sound surfaces MS of both sides are activated at the same time, which can lead to interference and thus to uneven cleaning, since interference produces energy-intensive and energy-weak areas. This can also damage the structures on the substrate surface 4.1 be caused in very high energy areas.

at another known embodiment does not come with an indirect megahall insertion of one Outer container in an inner container sonicated but the sound elements are from the outside directly to the two side walls of the proper process tank attached, making one possible intensive sonication of the substrate surfaces are made possible by megasonic should. Again, only from two opposite sides sonicated, wherein the sound elements strip-shaped in horizontal or vertical Direction attached to the container walls are. Even with this system, the megasonic performance of each chosen so high on both sides be that at least half Each substrate must be cleaned from a public address area.

The Problematic with the existing types of systems is that through Sonication of only two sides the required megasonic power everyone Sound side needs to be sized so that a large area the substrate surface is sufficiently cleaned by them. For systems that only off sounding in one direction, even the complete substrate surface of cleaned from a single sound field from one direction only become. In all listed Systems must have the sound power due to the required cleaning effect chosen so high that fine structures on the substrate are already damaged can.

Thereby reduces the number of usable areas of a substrate for the further chip production partly considerable.

to solution This problem became a static megasonic cleaning system constructed with indirect sound, its megasonic fields be placed and controlled so that the to be cleaned Although the substrate-acting megacycle performance is large enough to one To achieve good cleaning effect, but still small enough can be held to prevent damage to the structures on the To cause substrates. The megasonic elements are doing so in a way placed around the substrate to be treated, that on the whole substrate surface a uniform cleaning takes place without the cassette which the substrates in the inner basin Hold the Sound waves hindered.

The first part of the invention is to make the sonication of the indirectly sonicated megasonic cleaning system from as many different lateral directions as possible to act on the substrates to be cleaned, but at least from four different directions), so that from each sound field only a small sub-segment of a Substrate surface is to clean. The other segments of the substrate surface are each treated by another sound field from another direction. As a result, the megasonic performance of the individual sounding surfaces can be substantially reduced, yet, overall, a good and even over the entire surface of the substrate cleaning effect is achieved. The fact that now elected a much lower sound power who which is the case with the conventional ultrasonic cleaning systems, the damage of structures on the substrate surface is avoided.

Of the second part of the invention is the different sound fields in an order of activation, sonication intensity and sonication time adapted to the substrate to feed and use these parameters as a sonication recipe specifically for this Save the substrate type as a file using the operating software. A file created this way can then be changed at any time depending on the time treated substrate type called, modified or executed. Therefore different substrates usually different parameters are needed (some substrates are thinner or have smaller structures on the surface or have different Particle sizes that it must be removed) can thus be optimized for each type of substrate Sound prescription created and saved as a file. It can Any number of files can be created and saved.

By Operator software is now available for each substrate type individually the program with the appropriate one Sound parameters are started.

An embodiment of the invention show the 1 and 2 , Where 1 a front view and 2 a side view of a 5-sided megasonic cleaning system represents.

In the 1 and 2 shown preferred design consists of an inner basin made of quartz glass 3 with at least four side and differently angled side walls as well as a front and a back wall.

The inner basin made of quartz glass 3 is in an outdoor pool 2 positioned, which also has five lateral surfaces in addition to the front and rear wall. On the five lateral surfaces of the outer basin 2 In each case only one sounding surface (A, B, C, D, E) are attached.

Each of the five sound surfaces of the outdoor pool 2 have opposite the sidewalls of the inner basin 3 in each case a defined angle θ, in connection with the resonant frequency f used and the wall thickness t of the inner quartz glass basin 3 calculated and selected so that the megasonic power without reflection and refraction losses in the inner basin 3 arrives.

To activate the PA fields (A, B, C, D, E) is an arrangement of at least one megasonic generator 4 and a control box 5 used. The one or more megasonic generators) 4 be with the control box 5 which in turn is connected to the sound fields (A, B, C, D, E).

The control box 5 can now be programmed by means of a specially developed software so that any sound area (A, B, C, D, E) of the five side walls can be activated with an arbitrarily selected power between 0 and Pmax and an arbitrarily selected between 0 and Tmax sound duration , and all sound surfaces in any order one after the other or two sound surfaces simultaneously.

One thus created public address prescription can with the specially developed Server software saved as a file and called up at any time.

Thus, for various substrates 1 a specially adapted public address recipe is called and executed.

through The operating software can recreate a sound prescription or an already created and stored sound reinforcement recipe be called, modified or started.

The control box 5 then activates the respective generator 4 which in turn activates the public address areas (A, B, C, D, E) according to the sounding prescription selected by the operating software in the predetermined sequence with the prescribed sound power and with the given sound duration.

Claims (4)

Static megasonic cleaning system for cleaning substrates ( 1 ), consisting of an outdoor pool ( 2 ) with front and rear wall and at least four mutually angled side walls, wherein on the side walls in each case only one sound surface (A, B, C, D, ...) is mounted, wherein in the outdoor pool ( 2 ) an indoor pool ( 3 ) consists of quartz glass, which consists of at least four side walls in addition to the front and rear wall, which at a defined angle θ to the respective sound surfaces (A, B, C, D, ...) of the outer basin ( 2 ), in which the megasonic waves can pass without refraction through the quartz glass wall into the inner basin and wherein the outer basin ( 2 ) is filled with a transfer medium (eg water or another medium) and the inner basin is filled with at least one fluid, characterized in that the sonication of the substrates to be treated ( 1 ) is performed from at least four different, lateral directions and that each of the sound surfaces (A, B, C, D, ...) is each responsible for the treatment of only a small partial area of the entire substrate surface, whereby the sound power of the individual Beschallungsfächen (A , B, C, D, ...) can be reduced accordingly, so that damage to the structures is prevented by excessive sonication energy. Operating software for A static megasonic cleaning system according to claim 1, comprising the activation order, the sound intensity and the Sonication duration of the individual sounding areas (A, B, C, D, ...) and can be stored as a file, for different types of substrate to be processed thus created individual, optimized sound reinforcement recipes, can be saved or activated. Apparatus according to claim 1, wherein a plurality of sound surfaces (A, B, C, D, ...) can be activated simultaneously. Apparatus according to claim 3, wherein a megasonic generator ( 4 ) and a control box ( 5 ) are combined in one device.