DE102004045956A1 - Etching holder for use in etching system, has fixing unit that is adjustable, so that substrate is inserted into holder to form etching medium free area, and integrated radiation guidance beginning/ending at upper surface that limits area - Google Patents

Abstract

The holder has a fixing unit, which overlies on a flexible seal unit that circulates on a border area of a surface of a substrate wafer. The fixing unit is adjustable, so that the wafer is inserted into the holder to form an internal area that is free from etching medium. Integrated radiation guidance (12, 13) begin and end at an upper surface of the holder limiting the area and are connected with a radiation source and detector. An independent claim is also included for an etching system for controlling an etching process comprising an etchings mount.

Description

AREA OF INVENTION

The This invention relates to the production of substrates and more particularly an etch holder for a Substrate subjected to a one-sided etchant attack is, and an etching system for controlling an etching process.

BACKGROUND THE INVENTION

The surfaces Of substrate disks become common by etching processed, in particular for their further use in semiconductor technology. In this case, the substrate wafer is mounted on a substrate holder and for a certain amount of time in an etching bath immersed. Type, concentration and temperature of the etchant, Material of the substrate disk and other parameters influence the etching rate. To achieve a desired etch rate attacks one usually depends on corresponding empirical values of these parameters back.

An etching process can be used, for example, to the etching attack exposed areas of the substrate disc to a certain thickness or to etch a trench of a certain depth. The etching time in conjunction with the etching rate lead to the desired thickness change the exposed to the etching attack Area of the substrate disk. In the course of the etching process, however, the etching rate can be unpredictable Are subject to fluctuations, with the result that not exactly predicted can be when the substrate wafer the desired thickness change experienced or their specific final thickness has reached.

Around the etching depth or the remaining thickness of the substrate wafer as possible during the etching process Precise determination, therefore, are continuous measurement or thickness monitoring methods proposed.

For example, the DE 198 11 965 A1 a method for continuous optical thickness measurement of a substrate wafer during an etching process. In this method, the amount of light absorbed by the substrate wafer is determined. For this purpose, light in the wavelength range of 800 to 900 nm is irradiated from outside through the etching vessel to the etchant-free underside of a substrate wafer. The light emerging from the upper side of the substrate wafer is fed via light guides to light-sensitive detectors, with the aid of which the absorption of the light in the substrate wafer and therefrom the substrate slice thickness are continuously determined. In this measuring device, the light guides of the chemically aggressive etching solution (eg KOH, TMAH) are exposed. In the etching-technical series processing of substrate disks, therefore, the optical fibers are subject to such a strong optical degradation that they have to be replaced approximately every two weeks.

Out Elin Steinsland et al., "In Situ Measurement of Etch Rate of Single Crystal Silicon ", Transducers 1997, International Conference on Solid-State Sensors and Actuators, Chicago, pages 707-710, is another optical one Method for continuously measuring the etching rate of a silicon substrate wafer wherein the substrate disk is mounted in a holder and on one page over a circular opening to the etchant is exposed. In this method, the etching rate is determined interferometrically. For this purpose, radiation is in turn passed through an etchant-free area so that they do not by blowing in the etchant or by clouding affected becomes. The light source is one in the infrared wavelength range working laser whose beam with an angle of incidence of about 4 ° on the "dry" surface of the Substrate disc occurs, is partially reflected from there and partially to the "wet", i. exposed to the etchant attack, surface continues, to be reflected there again. These two reflected beam components are superimposed on each other and interfere with each other. With the help of a photodetector will the etching rate dependent on from the intensity or from the intensity changes and the wavelength the interfering beam parts determined. Concrete information on Holding the substrate disk during the etching process contains not this document.

The The present invention aims to provide a mount for an etch attack Substrate disc provided to provide, which Simplification of a continuous measurement of the etching progress or etching success contributes.

SUMMARY THE INVENTION

The The invention achieves this goal with the etching holder according to claim 1 and the etching system according to claim 16.

Further advantageous embodiments of the invention are specified in the dependent claims.

According to a first aspect of the invention, an etch holder for a substrate is provided, one (first) surface of which is subjected to an etchant attack monitored by an optical measuring device. The etch holder is also such formed, after receiving the substrate together with the other (second) surface of the substrate forms a sealed against the penetration of the etchant etchant-free space which is traversed by the rays of the optical measuring device. In this case, the etching holder is designed for a beam or measurement signal guide exclusively outside of the etchant.

The etching holder according to the present invention has the advantage that with her the current thickness of the substrate wafer or the etching rate in an etching process can be measured continuously. By measuring in the etchant-free Room performed is, may be a clouding or bubbling in the etchant do not affect the optical measurement, so that this more accurately and without too much fluctuation carried out the measurement can be.

The Providing an etching holder, which forms an etchant-free space together with the substrate wafer, protects the optical measuring device before the action of the etchant, so that no degradation the one for it used components occurs.

According to one preferred embodiment comprises the jet or measuring signal guidance on the two substrate surfaces directed and reflected by these rays, on the basis of which an interferometric measurement can be performed.

It can be provided that the Beam or measurement signal guidance at least partially within the etch holder to such a simple protection of the beam or measurement signal management (for example Optical fiber or electrical conductors) over the etchant put.

Farther can according to a embodiment be provided the invention that in the etchant-free Space delimiting surface sections the etching holder a radiation source and / or a radiation detector are integrated. As a result, etching holder, Radiation source and radiation detector compact as a device manageable and can together with the substrate disk with a handle from the etchant be removed.

According to one another embodiment The invention can be the etching holder Beam guides integrated in them Have (about light guide), which delimiting the etchant-free space surface the etching holder end or begin, through the etching holder pass through and with an external radiation source and / or an outside lying radiation detector are connected. The incident measuring beams occur at the the etchant-free Space delimiting surface the etching holder from the beam guide out and - after Reflection on the substrate disc - back into the beam guide. In this way it is possible radiation source and radiation detector at a sufficient distance from the etchant to arrange so that itself in case of accidental penetration of etchant into the etchant-free Room no damage or degradation of the measuring device takes place.

The Radiation source may be light of a predetermined wavelength or a predetermined wavelength range emit at the / the substrate disc at least partially transparent is. Especially with a substrate made of silicon or the like Material can be the source of light with a wavelength in the near Emit infrared range, for example in a wavelength range greater than 1 μm, there Silicon in this wavelength range is transparent.

According to one another embodiment According to the invention, the radiation detector can be an element for the spectral Dissecting the light and having an intensity measuring element, the a wavelength-sensitive Detection of the intensities allow the reflected light. This allows for a more accurate Measurement of the thickness change and on the other hand also the determination of the absolute thickness of the substrate.

Around the etchant-free To form space, a fixing device may be provided to to attach the substrate to the holder, wherein the fixing device is formed corresponding to a peripheral edge of the substrate. The Fixing device is advantageous because it is the substrate in one fixed, defined position, which allows an accurate measurement.

To the Sealing of the etchant-free Raums may be provided a sealing device, the so between the substrate and the etch holder is arranged that during an etching process penetration of the etchant in the etchant-free space is prevented. In particular, for sealing the etchant-free Raums the bracket connected to a vacuum pump to the Substrate by means of negative pressure in the etchant-free Space to press the bracket.

According to a further embodiment of the invention, the holder may comprise a spacer element for arranging the fixed substrate at a predetermined distance and in a predetermined orientation on the holder so that the light falls on the second surface of the substrate at a predetermined angle. This is particularly useful if the radiation source and the radiation detector are spatially separated from each other are arranged, wherein the reflection direction of the light reflected on the substrate depends on the orientation of the substrate.

Instead of the one optical measuring device according to a further embodiment also a plurality of optical measuring devices may be provided, each one are connected to an evaluation unit, depending on the / the measured intensities of the reflected light the etching progress and / or the residual thickness at several measuring surfaces of the substrate. Especially with multiple optical Measuring devices, the evaluation unit may be designed so that inhomogeneities of the etching process by comparing the etch progress or residual thickness detected at a plurality of measuring surfaces of the substrate wafer can be. With the help of the detected inhomogeneities can thus parameters of the etching process can be further improved so that the etching process is made more homogeneous.

According to one Another aspect of the present invention is an etching system with an etching holder the basic form described above or one of the preferred embodiments intended. The etching system has a control unit which is connected to the evaluation unit and an adjustment device that allows the etching process to influence. In particular, the control unit can be designed in this way be that she dependent from an etching parameter the etching process regulates. It can the temperature and / or the etchant concentration set by the control unit by means of the adjusting device become. By selective adjustment of the etching parameters during the etching can so the etching progress be specified exactly.

Farther For example, the control unit may drive the adjustment device to the etching holder after determining a predetermined residual thickness of the substrate wafer the etching attack to withdraw. For this purpose, the adjustment as mechanical Device may be configured, the etching holder after the detection the remaining thickness of the substrate wafer removed from the etchant. this has the advantage that the etching process is terminated automatically at the right time, so that the achieved etching depth as accurately as possible is complied with.

Further Features of the invention are apparent from the following detailed description of embodiments and the attached Drawings visible.

DESCRIPTION THE DRAWINGS

The Invention will be described below with reference to preferred embodiments and attached Drawings further explained. Show it:

1 a first embodiment of an etching holder according to the invention;

2 a second embodiment of an etching holder according to the invention; and

3 an etching system for controlling the etching process according to another embodiment of the invention.

DESCRIPTION THE PREFERRED EMBODIMENTS

1 shows an etching holder according to the invention 5 which is a substrate disk 2 receives and is immersed together with this for etching the disc in an etching bath. The etching holder 5 holds the substrate disk 2 so that from it only a defined section of its total surface, in the following first surface 3 exposed to the etchant, but the remaining surface, at least that of the first surface 3 opposite surface portion of the substrate disc 2 , in the following second surface 4 , is protected from an etchant attack. The etching holder 5 has a fixing device for this purpose 6 on, which - via an elastic sealing element 7 circumferentially on an edge region of the first surface 3 the substrate disk 2 rests. The fixing device 6 is adjustable by a suitable device (not shown), so that the substrate wafer 2 in the etching holder 5 can be used and fixed. This will cause a through the substrate disk 2 and the holder 5 educated interior 8th kept free of etchant and the pressure of the fixing 6 on the substrate disk 2 distributed as evenly as possible.

The substrate disk 2 lies with its second surface 4 on a spacer element 10 on a support surface 9 the holder 5 on, so that the sealing element 7 , the substrate disk 2 and the spacer 10 between the fixing device 6 and the bearing surface 9 are clamped. This will force on the flexible sealing element 7 exercised so that the interior 8th sealed against penetration of etchant.

The optical measuring device serves to increase the thickness of the substrate wafer 2 or their change in thickness in a Meßflecken- or reference area 17 to measure on the first surface, which is exposed according to a masking the etching attack. Preferably, the position of the reference area 17 suitably chosen so that the etching attack takes place as possible without fluctuations due to external influences in order to be able to measure there averaged for the entire etching surface etch rate. The location of the measurement should therefore be representative of the entire substrate. The holder 5 has a base section 11 through, through which a first and a second optical waveguide 12 . 13 are guided. The optical fibers 12 . 13 are with an optical measuring device 14 . 15 connected, which is a light source 14 and a photodetector 15 having. The light source, preferably a laser diode or LED, emits light of a predetermined wavelength or a predetermined wavelength range. The emitted light has a wavelength or a wavelength range at which the substrate wafer 2 at least partially translucent. The photodetector 14 is designed so that it over the second optical fiber 13 receive guided light beam wavelength selective and can measure the intensities of the individual wavelengths.

The first fiber optic cable 12 ends at the support surface 11 or indoors 8th so that light from the light source 14 through the etchant-free interior 8th on the second surface 4 the substrate disk 2 is delivered.

That through the interior 8th on the second surface 4 the substrate disk 2 directed light is on the one hand on the second surface 4 as well as on the first surface to be etched 3 reflected, so that the reflected light rays on a (also) in the support surface 9 the holder 5 lying end of the second optical waveguide 13 hit and be coupled there in this. The ends of the first and second optical fibers 12 . 13 are so in the bearing surface 9 arranged that of the first optical fiber 12 emitted light after reflection on both surfaces on the end of the second optical waveguide 13 falls. That is, the angle of emission of the light from the first optical waveguide 12 , the distance of the substrate disc 2 from the support surface 9 and the position of the end of the second optical fiber 13 are matched to each other so that the at the substrate disc 2 reflected light mostly from the end of the second optical fiber 13 can be included. The second optical fiber 13 then passes the captured light to the photodetector 15 the measuring device 14 . 15 , This is in turn connected to an evaluation unit (not shown), which is connected to the photodetector 15 Received signal evaluates.

The underlying measurement method is an interferometric measurement method. That from the light source 14 over the first optical fiber 12 on the substrate disk 2 directed light becomes a first portion of the second surface 4 due to the refractive index differences between the gas (air) in the interior 8th and the material of the substrate wafer 2 and to a second portion on the first surface 3 due to refractive index differences between the liquid etchant and the substrate disk material 2 reflected. The at the first and second surface 3 . 4 Reflected light rays are transmitted to the end of the second optical fiber 13 thrown back. The incident there light beams are superimposed, the two light beams interfere with each other due to the different maturities and a resulting light beam is produced, the intensity of which depends on the phase shift of the two reflected light beams.

If the change in the intensity of the resulting light beam over time is considered, at a known wavelength of the light source 14 emitted light beam, the etching rate of the on the first surface 3 attacking etching process can be determined. When using a light beam with several different wavelengths or with a wavelength range, it is possible by wavelength-selective evaluation of the resulting, via the second optical waveguide 13 received light beam, the remaining remaining thickness of the substrate wafer 2 in the reference area 17 determine. This can be done in the photodetector 15 the measuring device be provided with a spectrometer, with the resulting, returned light beam is decomposed into individual wavelengths, and from the intensities of the individual wavelength components, the remaining thickness of the substrate wafer is determined in a conventional manner.

In 2 a further embodiment of the present invention is shown in which, in contrast to the first embodiment, the substrate wafer by means of negative pressure on the etching holder 31 is fixed and the radiation source 39 or the radiation detector 40 are integrated in the etching holder. This embodiment provides an etch holder 31 on which several retaining pins 32 are applied to a patch substrate disc 33 against lateral slippage or displacement relative to the holder 31 to fix. The substrate disk 33 has a first surface which is exposed to the etching attack, however, a region to be etched may be selected from the first surface by a suitable etch mask. The substrate disk 33 comes with a second surface 34 on a sealing ring 35 placed on the substantially the same shape as the peripheral edge of the substrate wafer 33 having. The sealing ring 35 has a diameter that is slightly smaller than the diameter of the substrate wafer 33 , The sealing ring 35 , the substrate disk 33 and the holder 31 form a shielded against the etchant interior 38 ,

The holder 31 is via a pipe connection with a vacuum pump 37 connected, wherein the tube connection in the between the substrate disc 33 and the holder 31 as well as you tung ring 35 formed interior 38 ends. The vacuum pump 37 serves to the substrate disk 33 against the sealing ring to the holder 31 by pulling in the interior 38 generates a negative pressure.

In the etching holder 31 is the light source 39 , For example, in the form of a light-emitting diode, arranged so that they light of a wavelength or a specific wavelength range in the interior in the direction of the surface 34 the substrate disk 33 radiates to the area to be etched. The sensitive in the same wavelength range photodetector 40 is so in the holder 31 arranged that on him the substrate disc 33 reflected light of the LED 39 at least for the most part hits.

The wavelength of the light source 39 is chosen so that it lies in a wavelength range in which the substrate wafer is transparent. The photodetector 40 receives as the resulting light beam interfering with each other at the first and second surfaces of the substrate wafer 33 reflected light rays. By determining the change in the intensity of the resulting light beam is in an evaluation 42 connected to the light emitting diode 39 as well as the photodetector 40 via electrical connection lines 41 the measuring signals is connected determines the etching rate.

Preferably, the photodetector 40 formed spectrally dissolving and may for example consist of a semiconductor material such as InGaAs. For example, if the substrate disk 2 is formed of crystalline silicon, the light emitting diode should preferably emit light in the infrared wavelength range, in particular in the wavelength range greater than 1.1 microns, in which this material is transparent.

The Here proposed etch holders are but also for Substrate discs made of other materials usable, wherein an etching process the substrate discs are then monitored can be if the material is at least in a wavelength range is optically transparent. In particular, as materials silicon, GaAs, SiC, GaN, Ge, quartz, and other III-V semiconductors for substrate wafers usable.

The embodiments of the 1 and 2 may be provided with a plurality of measuring devices which are connected to the evaluation unit and depending on the measured intensities of the reflected light, the etching progress and / or the remaining thickness at a plurality of measuring spots on the substrate wafer 2 . 33 determine. The evaluation unit is then designed so that by comparing the individual etching rates or etching depths inhomogeneities of the etching process can be determined. Detected differences can then be used to adjust parameters of the etching process.

In 3 is an etching system with an etching tank 50 , a control unit 51 and a lifting device 52 shown. The lifting device 52 is designed so that an associated etching holder, in the example shown, the etch holder 31 of the 2 , from the etching tank 50 can be pulled out. The etching tank 50 is with an etching liquid, eg KOH, TMAH or similar. filled into which the etch holder 31 with the substrate disc to be etched attached thereto 33 , is immersed in the etching liquid.

The evaluation unit 42 now determines the etching rate of the etching process. It is with the control unit 51 which receives the etch rates and monitors the etch process. The control unit 51 determined by the time duration during which the etching attack on the substrate wafer 33 how much of the substrate material has already been etched. The control unit determines this dependent 51 the remaining thickness of the substrate wafer 33 and terminates the etching process when a desired residual thickness of the substrate wafer 33 is reached. The etching process is stopped by the control unit 51 the lifting device 52 instructs the etch holder 31 to lift out of the etching liquid.

The control device 51 can also determine whether the etch rate is constant or whether it decreases in order to influence the etching process by suitable Ätzpararneter depending on the decrease of the etching rate. This is the control device 51 with a heater 53 which can heat the etching liquid to enhance the etching attack. Furthermore, the control device 51 over a pipeline 54 additional etchant in the etching tank 50 initiate to counteract exhaustion of the etchant.

Of course, the etching system of 3 also with an etch holder of the embodiment of the 1 operate. Furthermore, it is possible that instead of the lifting device 52 also an outlet valve on the etching tank 50 is attached to when reaching the required thickness of the substrate wafer 33 and to stop the etching process, the etching liquid from the container 50 leave out and if necessary to start a subsequent flushing process.

Claims (20)

Etch holder for a substrate ( 2 ; 33 ) whose one (first) surface ( 3 ) is subjected to an etchant attack monitored by means of an optical measuring device, wherein the etch holder is designed in such a way that, after receiving the substrate ( 2 ; 33 ) together with the other (second) surface ( 4 . 34 ) of the substrate ( 2 ; 33 ) an etchant-free space sealed against the penetration of the etchant ( 8th ; 38 ), which is traversed by the rays of the optical measuring device, characterized in that the etching holder for a beam guide ( 12 . 13 ; 39 . 40 ) or measurement signal management ( 41 ) is designed exclusively outside the etchant. Etched mount according to claim 1, characterized in that the beam guide ( 12 . 13 ; 39 . 40 ) on the two substrate surfaces ( 3 . 4 ; 34 ) and reflected by these rays comprises. Etch holder according to claim 1 or 2, characterized in that the beam or measuring signal guide ( 12 . 13 ; 39 . 40 ; 41 ) extends at least partially within the etch holder. An etch holder according to claim 3, characterized in that the etchant-free space ( 8th ; 38 ) limiting surface sections a radiation source ( 39 ) and / or a radiation detector ( 40 ) are integrated. Etch mount according to claim 3, characterized by beam guides integrated therein ( 12 . 13 ), which at the etchant-free space ( 8th ; 38 ) boundary surface of the etching holder or begin to pass through the etching holder and with an external radiation source ( 14 ) and / or an external radiation detector ( 15 ) are connected. An etch holder according to claim 4 or 5, characterized in that the radiation source ( 14 ; 39 ) Emits light of a predetermined wavelength or a predetermined wavelength range for which the substrate (s) ( 2 ; 33 ) is at least partially transparent. An etch holder according to one of Claims 4 to 6, characterized in that the radiation source ( 14 ; 39 ) Emits light with a wavelength in the near infrared range, in particular in a wavelength range above 1 micron. Etched mount according to one of Claims 4 to 7, characterized in that the radiation detector ( 15 ; 40 ) has an element for the spectral decomposition of the light and / or an intensity measuring element. An etch holder according to one of the preceding claims, characterized in that a substrate ( 2 ; 33 ) holding fixer ( 6 . 7 ) is provided corresponding to a peripheral edge of the substrate ( 2 ; 33 ) is trained. Etching holder according to one of the preceding claims, characterized in that between the substrate ( 2 ; 33 ) and the etching holder a the etchant-free space ( 8th ; 38 ) surrounding sealing device ( 7 ; 35 ) is arranged. Etch holder according to one of the preceding claims, characterized by a space free of the etchant ( 8th . 38 ) vacuuming vacuum pump ( 37 ) for generating a negative pressure. Etch holder according to one of the preceding claims, characterized by a spacer element ( 10 ), with which the fixed substrate ( 2 ; 33 ) can be arranged at a predetermined distance from, and given orientation to the surface portion of the etch holder opposite the substrate. Ätzhalterung according to one of the preceding claims, characterized that further optical Measuring devices are provided, with which the intensity of the reflected Light can be measured. An etch holder according to claim 13, characterized in that an evaluation unit connected to the optical measuring devices ( 42 ) and is designed such that, based on the measured intensities, the etching progress and / or the residual thickness of the substrate ( 2 ; 33 ) as well as inhomogeneities of the etching process can determine. Ätzhalterung according to one of the preceding claims, characterized that she is adjustable so that the monitoring of the etchant attack at a predetermined representative Location of the substrate feasible is. An etch system for controlling an etch process, comprising: an etch mount according to claim 14; - a control unit ( 51 ) connected to the evaluation unit ( 42 ) connected is; and a device ( 52 . 53 . 54 ) for adjusting the etching process. An etching system according to claim 16, wherein the control unit ( 51 ) is configured to control or regulate the etching process in response to one or more etching parameters. An etching system according to claim 17, wherein the control unit ( 51 ) is designed such that it determines the temperature and the etchant concentration in dependence on one or more etching parameters with the aid of the adjusting device ( 52 . 53 . 54 ). An etching system according to any one of claims 16 to 18, wherein the adjustment device ( 52 . 53 . 54 ) is designed such that it reaches a ge desired residual thickness of the substrate wafer ( 2 ; 33 ) the etching holder ( 5 . 31 ) eludes the etching attack. An etching system according to claim 19, wherein the adjustment device is a mechanical device ( 52 ) is formed, which upon reaching the desired residual thickness of the substrate wafer ( 2 . 33 ) the etching holder ( 5 . 31 ) removed from the etchant.