JPH0137965B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus for processing molten wax, and more specifically, it is generally in a solid state or a highly viscous state at room temperature, and is used to polish, wrap or mirror-finish the surface of semiconductor wafers. (called polishing)
The present invention relates to an apparatus that removes and refines contaminant particles by passing through the wax used to fix the semiconductor wafer to the polishing plate.

Conventionally, a membrane made of polytetrafluoroethylene or a membrane made of sintered metal has been used to cover this wax.

By the way, wax used for fixing semiconductor wafers is easily deteriorated by oxidation at temperatures far above its softening or melting temperature, so when solid impurities are removed from the wax by passing through it, the temperature of the wax is softened. It must be suppressed to a temperature slightly higher than the melting temperature. As a result, the semiconductor wafer fixing wax must be passed through while remaining relatively highly viscous.

However, when trying to filter highly viscous wax under pressure through a membrane made of polytetrafluoroethylene, the membrane deforms due to its flexibility or viscoelasticity, and the size of the pores increases. There was a risk that things would change, and it would be difficult to make mistakes, for example.

On the other hand, in sintered metal permedia, the pores are relatively large and the particle size is small.
It is only possible to remove particulate matter of about 1 μm or more by filtration, and it is not necessarily preferable for filtration of wax for fixing semiconductor wafers. Furthermore, conventional sintered metal permedia has pores of substantially uniform size along its thickness.
Since the entire layer is formed to act as an overlayer, it is necessary to make the overlayer considerably thicker in order to impart appropriate mechanical strength to the overmedia. I needed to apply pressure.

The present invention has been made in view of the above-mentioned points, and its purpose is to not only allow wax for fixing semiconductor wafers to be easily coated while maintaining a relatively high viscosity, but also to form solid particles with extremely small particle size. It is an object of the present invention to provide a wax cleaning device that can easily and reliably remove even objects.

According to the present invention, the object is to provide an overlayer made of porous ceramics for passing wax, and an overlayer made of porous ceramics superimposed on and supporting the overlayer and having pores larger than the overlayer. a supermedia consisting of a support layer; a case containing the media and whose inside is divided into two chambers by the media; a heater for heating and melting the wax; a first container connected to one chamber of the case for accommodating the conditioned wax and supplying the wax to the one chamber in contact with the overlayer;
This is achieved by means of a wax filtration device comprising a second container connected to the other chamber of the case in contact with the support layer for containing the wax after rinsing.

In this specification, wax for fixing semiconductor wafers refers to wax that is obtained by polishing the surface of flat semiconductor wafers cut out with various crystal planes depending on the type of semiconductor and the use of the semiconductor wafer to eliminate warpage, distortion, etc. This wax is used to fix a semiconductor wafer to a polishing plate when finishing the surface with a small thickness, small thickness unevenness, and high flatness.

At the temperature used for fixing, for example, room temperature, this wax is in a highly viscous state that can be considered solid or substantially solid. Waxes include not only esters of fatty acids and water-insoluble higher monohydric alcohols or dihydric alcohols, but also
So-called waxes, such as wood waxes made of aliphatic carbides (paraffins) with high melting points, petroleum waxes, etc. may be used, and chemically a mixture may be used, but the softening or melting temperature is high enough not to soften due to heating during polishing. (e.g. 60℃ or higher, preferably 80℃ or higher),
In addition, it is preferable that the range of melting temperature is small enough to uniformly soften when applied to a polishing plate, and the thermal conductivity is high. As this kind of wax,
Examples include refined paraffin, sierraque, pine resin (mixed with olive oil), and mixtures of sealing wax and beeswax.

A molten state refers to a state in which the material has substantially fluidity, and a state in which the viscosity is approximately 1×10 ⁻¹ poise or less.

The ceramic constituting the permeable medium may be not only a metal oxide such as alumina, but also a nitride, a carbide, etc., or a mixture thereof. Furthermore, the superlayer and the support layer may be made of different ceramics.

The porous ceramic support layer is preferably made of a sintered body of alumina particles of comparable particle size, but has a thickness that provides the overmedia with sufficient mechanical strength to withstand overpressure; As long as the support layer has pores that can reduce the pressure loss when the relatively high viscosity molten wax passed through the overlayer flows through the pores of the support layer to the same level or less as the pressure loss in the overlayer, ceramic particles of various sizes etc. Other materials such as a sintered body may also be used.

The porous ceramic overlayer is preferably as thin as possible, and is preferably fixed to the support layer by sintering. It is preferable that the pores of the overlayer have a smaller pore diameter and a smaller variation in pore diameter.

For example, according to the method disclosed in Japanese Unexamined Patent Publication No. 57-71604, porous alumina porcelain having pores of 15 to 20 μm is formed as a support layer, and one surface of the support layer is formed so that the pore size gradually becomes smaller. If an alumina slip layer with an adjusted grain size range is deposited at least twice on the base and fired in one piece, the thickness will be
An overlayer with an average pore size of about 0.2 μm is formed when the pores are about 10 μm.

In addition, the outer diameter 19 mm and inner diameter 15 mm formed in this way
With hypermedia, which has an overlayer of about 10 μm on the inner circumference of a support layer of mm, the radial crushing strength measured with a ring with a length of 15 mm reaches 740 Kg/cm ² , and the hypermedia has a sufficient overpressure of about 10 atm. I could endure it.

The overmedia may be formed by adhering an overlayer to the outer periphery of a tubular support layer, or by adhering an overlayer to the inner and outer peripheries of a tubular support layer, or may be formed by at least one of a flat support layer and a curved support layer. It may also be formed by depositing an overlayer on one surface.

Next, a filter device 1 according to an embodiment of the present invention will be explained based on FIGS. 1 and 2. FIG.

In the figure, 2 is the alumina main body,
The filter main body 2 includes a cylindrical case 3 made of alumina,
Three tubular overmedia 4, 5, 6 made of alumina are arranged symmetrically in the case 3, and a support part 7 fixes both ends of the tubular overmedia 4, 5, 6 to both ends of the case 3. It consists of 8. Upper support part 7
has an alumina support frame 9 airtightly fitted to the upper end of the case 3, and a hole 10 communicating with the upper end opening of each overmedia 4, 5, 6. 6 and a partition plate part 11 made of alumina, the upper end of which is airtightly fitted. Lower support part 8
It has an alumina support frame 12 airtightly fitted to the lower end of the case 3 and a hole 13 in the center, and the lower end opening of the overmedia is connected to the packing 14.
It consists of a partition plate part 14 made of alumina that is liquid-tightly sealed via a.

The case 3 and the supports 7, 8 may be made of another ceramic instead of alumina, and the temperature of the molten wax as a covering material, e.g.
It may be made of other materials such as metal or plastic as long as it can withstand temperatures of about 100 to 200°C.

The case 3 may have another shape such as a rectangular tube shape instead of a cylindrical shape. Note that a through hole may be provided in the upper part of the peripheral wall of the case 3.

The overmedia 4 is integrally fixed to a support layer 15 made of a relatively thick tubular alumina sintered body with a relatively large pore diameter and high mechanical strength, and an inner wall of the support layer 15. Overlayer 16 made of a thin tubular alumina sintered body with small pore diameters
It consists of The pore diameter of the supporting layer 15 is 10 to 30μ
The thickness is about 1.5 to 2 mm, and the superlayer 1
The average diameter of the pores in No. 6 is about 1.0 to 0.1 μm, preferably about 0.5 to 0.1 μm, and the thickness is 100 to 20 μm.
about 40 to 20 μm, preferably about 40 to 20 μm. The overmedia 5 and 6 are constructed similarly to the overmedia 4.

Note that the support layer 15 may be composed of a plurality of layers, and may be formed such that the outer layer in the radial direction has a larger pore diameter. Support layer 1
The boundary between the overlayer 16 and the overlayer 16 does not need to be clear, and it is sufficient that the overlayer that carries the molten wax and the support layer 15 that mechanically supports the overlayer 16 are substantially formed.

The number of tubular overmedia provided in the main body 2 may be one or two, or four or more.

Reference numeral 17 denotes a crucible for accommodating unmelted wax 18 in cooperation with the main body 2, and a chamber 19 within the crucible 17 is provided with tubular permeable media 4, 5 through a hole 10 located at the bottom of the crucible 17. , 6 are in communication with the cylindrical hole portions 20 of the holes. In the chamber 19 in the crucible 17, a tube 22 for introducing pressurized inert gas having an inlet 21 in the support 7 extends to the upper part.
23 is a band that is engaged with the support frame 9 of the support part 7; 24 is a band that pushes up the upper part 25 of the band 23 to engage the band 23 with the support frame 9 and fixes the crucible 17 to the container body 2; This is a tightening screw for

27 is a crucible which is fixed to the apparatus main body 2 by a support part 8 and is used to accommodate the molten wax 28 after evaporation. Space 30 inside the case 3 around the tubular permediates 4, 5, and 6
is communicated with.

Reference numeral 31 denotes a pedestal, and the pedestal 31 supports a crucible 33 consisting of the crucible 27, the crucible body 2, and the crucible 17 at the bottom 32 of the crucible 27 and the support frame portion 12 of the support portion 8.

34 is a heater that heats the crucibles 17, 27 and the reactor body 2. In addition, the heater 34
7 and the filter main body 2 may be heated.

In the coating device 1 constructed as described above, wax coating is carried out as follows.

First, the screw 24 is screwed into the crucible 17 side to disengage the lower end engaging portion of the band 23 and the support frame portion 9 of the container body 2, and the crucible 17 is removed.

Next, the wax, which is in a substantially solid state as a whole and contains high melting point impurity components to be removed by filtration, is placed on the partition plate part 11 constituting the bottom wall of the crucible 17, either as a lump or crushed into pieces. , crucible 1
7, and the annular lower edge of the crucible 17 is pressed against the partition plate portion 11 via the packing using the band 23 and the screw 24 to seal the chamber 19.

Next, the entire heating apparatus 1 is heated to a suitable temperature of about 100 to 200 DEG C. depending on the type of wax using a furnace or heater 34. This temperature is kept within a range that can avoid deterioration of the wax due to oxidation, thermal decomposition, etc., and is usually about 180 to 200°C at the most.

If there is a risk that the wax 18 may be oxidized by this heating, the apparatus 1 must be filled with an inert gas such as nitrogen gas or the like before heating.
The interior may be substantially evacuated.

By heating with the heater 34, the wax 18 in the crucible 17 becomes molten and enters the hole 20 of the tubular permeable medium 4, 5, 6 through the hole 10.

After the holes 20 are filled with molten wax, a pressurized inert gas, such as pressurized nitrogen gas or pressurized argon gas, is introduced into the upper part of the chamber 19 in the crucible 17 via the gas inlet tube 21. As a result, in addition to the weight of the molten wax 18, an overpressure is applied due to the pressure difference between the chambers 19 and 30 on both sides of the overlayer 16, and the wax 2 other than solid impurities with a high melting temperature is
8 immediately passes through the overlayer 16 into the chamber 30 and further through the hole 13 and accumulates in the chamber 29 of the crucible 27. In the apparatus 1, since the filtration is carried out using ceramic media 4, 5, and 6 having high mechanical strength, the pressure of the pressurized air can be increased, and even the highly viscous wax 18 can be filtrated in a short time.

In the apparatus 1, since the overlayer 16 is thin and the overmediaries 4, 5, and 6 with low pressure loss are used for evaporation, if the viscosity of the wax 18 is not so high, additional overpressure is applied by the pressurized gas. Even without it, you can make a mistake relatively quickly.

At the end of the overlayer, the pressurized gas enters the overlayer 16.
To enter chamber 30 through
It is performed using 8's own weight. In addition, a through hole is provided in the upper part of the peripheral wall of the case 3, and the pressurized air is passed through the pipe 22.
If you want to install it continuously from
Overpressure can be applied with gas until the filtration is complete.

Once substantially all of the wax 18 has been applied, at least the lower end 32 of the device 1 is connected to the heater 34.
The apparatus 1 is moved downward relative to the heater 34 so as to be located outside, and the handle 31a is turned to open the lower end opening of the crucible 27 and take out the molten wax 28.

In the wax 28 obtained in this way,
Solids with a particle size of, for example, 1 μm or more are considered virtually non-residue.

3 and 4 show a part of a polishing device 36 for polishing the surface of the semiconductor wafer 35 in order to finish the surface of the wafer 35. As shown in FIG.

In the polishing device 36, 37 is a polishing cloth 38
has a fixed horizontal surface 39 and an axis 40
41 is a turntable configured to rotate in the A direction around an axis 42, and configured to rotate in the B direction around an axis 42 and configured to press in the C direction, with the surface 43 The polishing plate is mounted on the main body of the device 36 so as to be kept parallel to the surface 39 of the turntable 37.

44 is a layer of wax 28 that fixes the semiconductor wafer 35 to the surface 43 of the polishing plate 41.

When fixing a semiconductor wafer 35 cut out along an appropriate crystal plane depending on the type of semiconductor and the application of the semiconductor wafer to the surface 43 of the polishing plate 41 with wax 28, a predetermined surface 43 of the polishing plate 41 is Wax 28 heated and melted on the area
A semiconductor wafer 35 is placed on the applied molten wax 28, and the wafer 35 is pressed against the plate 41 until the wax 28 cools and solidifies. The wafer 35 is fixed to the plate 41 by the wax layer 44 formed when the thin liquid layer of the wax 28 solidifies, but the wax 28, in its molten state, contains solid impurities with a large particle size of, for example, over 1 μm. The wax layer 44 is extremely thin (for example, about 1 to 10 μm) to prevent
The surface 4 of the semiconductor wafer 35 can be of uniform thickness.
5 can be positioned parallel to the surface 43 of the polishing plate 41 with high precision.

By polishing the surface 46 of the semiconductor wafer 35 fixed to the polishing plate 41 through the wax layer 44 with the polishing cloth 38 of the device 36, the surface 46 of the wafer 35 is polished with high precision relative to the surface 45. It becomes one plane that can be parallelized and has a high degree of flatness.

The wafers obtained in this way have unevenness within 1 μm in terms of lap and polish finishing accuracy.
Alternatively, it is suitable for use as a wafer for monolithic integrated circuits that requires parallelism on both surfaces.

Embodiment A tubular supermedia with open ends (outer diameter 19
mm, inner diameter 15mm, length 70mm, overlayer thickness about 10μ
A tubular overlayer (effective surface area of the inner circumferential surface of the overlayer 16: 2500 mm ² ), which is made by sealing one opening of a pore with a heat-resistant rubber (with a pore diameter of 0.1 to 0.9 μm), is placed vertically, and a semiconductor is placed vertically. A wax for fixing or adhering the wafer (eg, commercially available "Melt Wax" or "Photomax") was used.

During the heating process, first, solid wax was crushed and placed in a tubular strainer, and the whole strainer was heated in a constant temperature bath. This wax melted at about 85°C. At this time, the wax is approximately 45mm inside the tubular tube.
It was at a depth of .

When the temperature of the wax was set to 90°C, it was observed that the wax oozed out from the tube wall of the tube, but due to the high viscosity of the wax, the wax did not substantially flow out.

When the temperature of the wax was maintained at 110° C., the viscosity of the wax decreased and an excess wax of 10 c.c. was obtained in about 5 hours.

On the other hand, when the temperature of the wax was maintained at 130° C. with other conditions being the same, the viscosity of the wax further decreased and the excess amount reached 10 c.c. in about 3 hours.

Further, keeping other conditions the same, a tube was connected to the open end of the above-mentioned strainer, and pressurized nitrogen gas was supplied through the tube to apply a constant pressure of 200 mbar to the unfiltered wax in the strainer. If the wax temperature is 130
℃, an overwax of 10 c.c. was obtained in 20 minutes.

In addition, in the above, when the previous wax was observed under a metallurgical microscope, there were 2 particles/cm ² on the surface of the molten wax with a particle size of approximately 20 μm (approximately 120 particles/cm ² of particles larger than approximately 1 μm). However, in the molten wax after treatment, the particle size was approximately 20 μm.
However, only about 5 particles/ ^cm2 with a particle size of about 1 to 3 μm were observed. 1μ between
It can be considered that there is practically no possibility that particles exceeding m are present.

As described above, in the wax filtration device according to the present invention, the permeable medium has a porous ceramic overlayer for passing the wax, and a porous ceramic overlayer that is superimposed on the overlayer to support the overlayer and has pores larger than the overlayer. The case houses the media, which divides the interior into two chambers;
A container is connected to one chamber to contain the wax that has been molten by the heater and to supply the wax to one chamber of the case that is in contact with the overlayer, so that the wax flows through the overlayer through a small pore size. Since the flow flows from the overlayer to the support layer with larger pores, it is possible to prevent the support layer in the media from clogging, and the reinforcement by the support layer can prevent destruction of the overlayer, resulting in In addition, by reinforcing the overlayer with the supporting layer, the wax supply pressure can be increased and relatively high viscosity waxes can be handled, and the overlayer with a small pore size can also reduce solids. can also be easily removed.

The apparatus of the present invention can also be applied to other waxes that require the removal of solids, as well as waxes for fixing semiconductor wafers.

[Brief explanation of drawings]

FIG. 1 is a front explanatory view of an embodiment of the wax filtration apparatus according to the present invention, FIG. 2 is a plan view of the apparatus shown in FIG. FIG. 4 is an explanatory diagram of a polishing plate of the apparatus of FIG. 3. 4, 5, 6... overmedia, 15... support layer, 16... superlayer, 18, 28, 44... wax, 34... heater, 35... semiconductor wafer.

Claims (1)

[Scope of Claims] 1. A porous ceramic overlayer for passing wax, and a porous ceramic support that is superimposed on and supports the overlayer and has larger pores than the overlayer. a supermedia consisting of a layer; a case containing the media and whose inside is divided into two chambers by the media; a heater for heating and melting the wax; and a heater for heating and melting the wax; a first container connected to one chamber of the case in contact with the overlayer for accommodating the applied wax and supplying the wax to the one chamber of the case; a second container connected to the other chamber of the case in contact with the wax filtration device. 2. The device according to claim 1, wherein the first container is provided on the case so that the wax is supplied to the one chamber by its own weight. 3. The device according to claim 1 or 2, wherein the medium is a cylindrical body, and the overlayer is arranged on the inner circumferential side and the support layer is arranged on the outer circumferential side.