DE19737802A1 - Thermal treatment especially of semiconductor wafers - Google Patents

Abstract

During thermal treatment of a substrate positioned parallel to a plate within a reaction chamber, the radiation in the space between the substrate and the plate is optically detected for determining the substrate temperature. An Independent claim is also included for a substrate thermal treatment apparatus comprising a reaction chamber (2), a heat source (3) and a plate (9) positioned parallel to the substrate (6), the plate (9) having an aperture (14) for exit of radiation from the space (15) between the substrate (6) and the plate (9). Preferred Feature: The substrate, the plate and the space form a hollow body radiator.

Description

The invention relates to a method for thermal loading deal with substrates, especially semiconductor sub straten or wafers, in which at least one substrate in a reaction chamber with at least one heating source is heated, with a plate parallel to the be acting substrate is provided. The invention be continues to hit a device for thermal loading handling of substrates, with a reaction chamber, we at least a heat source and a plate that is parallel is arranged to the substrate to be treated.

A method and a device of this type is known from the DE 44 37 361 C going back to the same applicant knows. In addition, there are rapid heating processes and systems systems based on the same applicant Publications DE 40 12 615 C, DE 42 23 133 C or the DE 44 14 391 A, and from US Pat. Nos. 5,226,732, 5,359,693 and 5,628,564. More Schnellheizver Driving and devices are in the publications J. Nackos: 2nd International Rapid Thermal Conference, RTP '94. Monterey CA, Proc. p. 421-428 (1994), Arun K. Nanda, Terrence J. Riley, G. Miner et al: "Evaluation of Applied Materials Rapid Thermal Processor Using SEMATECH Metrologies for 0.25 µm Technology Thermal Applications " Part 11, Presentation at the Rapid Thermal and Integrated Processing Conference MRS Spring Meeting '96, San Fran cisco CA and Terrence F. Riley, Arun K. Nandam G. Miner et al .: "Evaluation of Applied Materials Rapid Thermal Processor Using SEMATECH Methodologies for 0.25 µm Technology Thermal Applications "Part I.lbid as well the publication R. Bremsensdorfer, S. Marcus and Z. Nenyei: "Patters Related Nonuniformities During Rapid Thermal Processing ", Presentation at the Rapid Thermal and Integrated Processing Conference MRS Spring Meeting  '96, San Francisco CA and the post-published Druch written by Z. Nenyei, G. Wein, W. Lerch, C. Grunwald, J. Gelpey and S. Wallmüller: "RTP Development Requirements", presented at RTP '97 Conference Sept. 3-5, 1997 New Orle ans, with one for the latter two articles the inventor of this application is a co-author. At all These methods and devices make it difficult and, if at all, only with great effort, the for the treatment process and for its control and Regulation required substrate temperature in the required to determine accuracy. The temperature determination is particularly difficult because the heat beam development of the substrate to be treated, for example one Semiconductor wafers, from the reflected radiation of the Heat source (s), for example separated from the lamp radiation because the reflected radiation is the measurement result influenced. In addition, the heat radiation changes of the wafer with its emissivity, the or their changes a priori is not known. To measure the temperature To be able to perform as accurately as possible is time-consuming Selective filter required, which the lamp radiation in a narrow optical frequency band in the area of measurement suppress wavelength. Also different emissivities are compensated for as well as possible. Dar In addition, the measurement results are not only the reflected lamp radiation, but also by the Transmission affected by the substrate to be treated, so that due to the background radiation a sufficiently accurate measurement of the substrate temperature is difficult. In addition, those with pyrometri measurement results obtained by measuring methods Interference effects on the surfaces of the substrates ver fakes that through thin layers on the substrate top areas arise.

In addition to wavelength selective and intensity modulation selective processes, such as those from the  US 507 605 known so-called "Ripple- Technology "are still wave vector selective Pyrometry process known to the background beam Select a larger energy range. At This procedure uses the angular distribution of the whole Lamp radiation with different reflector shapes charak teristically directed, and the temperature measurement takes place from a direction in which the background radiation Minimum.

In all of these known methods is suppression the background radiation, if at all, only with great Effort possible to determine the substrate temperature for the tax control the treatment process sufficiently well can.

The invention is therefore based on the object, a Ver drive and a device for rapid thermal loading act to specify or create substrates with with which a reliable determination of Substrate temperature in a wide temperature range simple way is possible.

Starting from the above, from DE 44 37 361 C2 known method, the task is solved in that the temperature in the space between between the substrate and the plate to determine the tem temperature is determined optically. With this known ver driving will adversely affect the temperature measurement flowing background radiation caused by reflection, Transmission and interference effects arise, widely separated from the actual substrate emission, see above that very good, uninfluenced measurement results are achieved can.

According to a very advantageous embodiment of the inven Form the substrates, the plate and the intermediate  space between the substrate and the plate a cavity radiator whose temperature is measured optically. Of the Cavity emitter ensures that those appearing from the outside Influences in temperature determination largely avoided because the temperature of the substrate is direct is measured and controlled, in contrast to conventional process. In this way it is avoided that the Temperature measurement through reflections or transmissions of the substrates or plates or by optical thin Layers on the substrate surfaces, be they on the Front or back of the substrate or the Disk, or its changes disturbed or affected can be.

Preferably in the cavity radiator or in the Zwi space between the substrate and the plate radiation through a hole in the plate in front of it is preferably arranged in the middle of the plate, exits, measured and evaluated to determine the temperature. The radiation emerging from the hole is in front preferably measured and evaluated with a pyrometer. A calibration that may be required is feasible in the usual, conventional manner.

According to a further advantageous embodiment of the Invention is the radiation after emerging from the hole so focused that the one coming from the edge of the hole Radiation is not detected by the measuring device. The Measuring device therefore "sees" the edge of the hole Plate not, so that the measurement results by the Randbe rich of the hole can not be adversely affected.

The measuring device preferably detects or measures preferably a pyrometer, which from the space between radiation emerging from the substrate and the plate at a selected frequency. The measurement is however advantageously also in a narrow band and ins  especially in a broadband frequency range Advantage possible.

It is very advantageous if between the substrate and the plate has a thermal equilibrium. This can be achieved with advantage that both the side of the substrate facing away from the plate, as well as the side of the plate facing away from the substrate Radiant heaters are irradiated, so that a double-sided There is heating. It is particularly advantageous also, the upper and lower radiant heaters or lam to control pen banks independently of each other apply in order to be able to establish a thermal equilibrium nen. This creates one of the ideal black bodies radiation approximate radiation from the cavity radiator, which are kept essentially free from external influences can be.

An embodiment of the invention in which the plate and / or the substrate is opaque, contributes to improvement of the method according to the invention, since thereby the Cavity heater is additionally stabilized.

Starting from the device mentioned at the outset DE-44 37 361 C, which goes back to the same applicant is known, the task is inventively also solved in that the plate has a hole for exit that in the space between the substrate and the plate radiation occurring. The previously together Hang described with the inventive method Advantages also occur with the device according to the invention tion.

Preferably, the substrate, the plate and the Clearance between the substrate and the plate Cavity radiator formed, which is a determination of the Substrate temperature allows without external A  flows, reflection and transmission properties or Changes in the substrate surface appear disruptive to step.

The radiation emerging from the hole in the plate becomes by an optical measuring device, preferably a Py rometer, measured and to determine the substrate temperature tur evaluated, this for a selected Fre quenz, or in a narrower or wider frequency bound the radiation depending on the existing circumstances and requirements can be carried out.

According to a particularly advantageous embodiment of the Invention is the distance between the substrate and the Plate small in diameter. The bigger the Plate and substrate diameter, and the smaller the distance between plate and substrate is selected, de ideal properties of the cavity radiator themselves, because by doing so the edge areas of the through plate and Cavity emitter formed substrate practically vernach are casual. To improve the cavity egg properties, it is still advantageous both on the Substrate as well as on the plate side of the substrate Plate arrangement at least one radiant heater or to arrange individual lamps, if necessary and before can also be controlled independently of one another can to the substrate-plate arrangement as possible to give good thermal balance.

The measurement results are according to a further embodiment tion form of the invention additionally improved when between rule the measuring device and the hole, preferably di right in front of the hole, a wide-angle lens is provided is so that there is no radiation emanating from the edge of the hole the measuring device or the pyrometer falls, causing a adverse influence on the measurement result by edge areas of the hole can be avoided.  

It is also advantageous to use light lines to the beam transmission between the substrate hole and the measurement device.

The term substrates are used in this context Semiconductor wafers, masks, plates, and all objects too understand the surface of a thermal Undergo treatment.

The invention is described below with reference to a preferred one Embodiment with reference to the only Fi gur explained, which is a schematic cross-sectional representation development of a rapid heating device.

In a mirrored chamber 1 there is a reactor chamber 2 , which is preferably made of quartz glass. On the top and on the bottom of the reaction chambers 2 , heating sources 3 in the form of lamps are net angeord. The reactor chamber 2 has a gas supply pipe 4 for introducing a reaction gas and a chamber door 5 for introducing and removing a substrate 6 , in the present case a semiconductor wafer with a diameter of 150 to 200 mm. On a quartz substrate carrier 7 there is a plate 9 spaced from it by spacers 8 , which is also referred to as a hotliner plate and preferably has the same diameter, ie 150 or 200 mm, as the substrate 6 . Parallel to the hotliner plate 9 and at a distance of preferably 5 to 6 mm from it, the substrate 6 is arranged in the reactor chamber 2 . Concentric to the hotliner plate 9 , a compensation ring 10 is provided with which better thermal homogeneity can be achieved. Gas distributor plates 13 are located in the vicinity of an inlet opening 11 of the gas supply 4 .

The quick heater described above, as well as de Ren details and functions are already from the mentioned, going back to the same applicant DE 44 37 361 C2 is known, so that reference is made to it. Around To avoid repetition, this publication is in if made to the content of the present application.

In the illustrated embodiment, a hole or hole 14 is formed in the center of the hotliner plate 9 , which preferably has a diameter of 1 to 2 mm and by the radiation from the space 15 between the substrate 6 and the hotliner plate 9 emerges, and through a broadband lens 16 , that is, through optics for large sea angles, from the reactor chamber 2 and then from the chamber 1 to the outside and, if necessary, after passing through at least one further lens or another lens system 17 a py rometer 18 falls.

The reactor chamber 2 and the hotliner plate 9 together form a cavity radiator which, owing to its relative latitude, contains radiation which is essentially independent of external influences, such as lamp radiation, reflections, surface properties of the substrate 6 or the hotliner plate 9 or any other background radiation. The cavity radiator comes closer to the ideal of a black radiator, the larger the diameter of the substrate 6 and the hotliner plate 9 and the smaller the distance between them. Because of the cavity emitter properties are practically independent of the edge area.

The invention has been described with reference to a preferred exemplary embodiment. However, refinements, modifications and modifications are possible for the person skilled in the art without thereby departing from the inventive idea. For example, it is possible to arrange the hotliner plate 9 on the other side of the substrate 6 than is the case in the exemplary embodiment shown. In particular, it is also possible to provide a further plate on the side of the substrate 6 facing away from the hotliner plate 9 , in particular when a treatment process of a lightly doped semiconductor substrate is to be carried out at below 600 ° C. The lamp plate is also shielded from above by the additional plate. The entire substrate 6 is therefore in a cavity which represents a black body, with the advantage that structure-related thermal and process inhomogeneities are excluded even more completely. In addition, it is additionally possible to provide a thermocouple element which is arranged on the quartz carrier in such a way that the downward-facing sides of the substrates 6 come into contact with this thermocouple. The measuring accuracy of the contact thermocouples is much better due to the hotliner plate 9 , since this shields the thermocouple contact point at which the thermocouple is in contact with the substrate 6 against the lamp radiation. The temperature measurement with the contact thermocouple is therefore more reliable and less prone to errors. The measurement of the substrate temperature with at least one contact thermocouple is particularly advantageous in the low temperature range, i.e. around and below 600 ° C, but can also be used with high-temperature processes or with gradually changing temperatures.

In the following, the invention is further explained by means of embodiments for emission compensation by means of at least one plate ( 9 ) - hereinafter referred to as a hotliner - from which additional advantages, details and possible embodiments of the invention result and which express them even more clearly.

For an optical steel, the conservation law applies in every point of its path

α + τ + ρ = 1 (1)

With
α absorption coefficient
τ transmission coefficient
ρ reflection coefficient
or in words, the beam is either absorbed, transmitted or reflected. Kirchhoff's law also applies to emissivity ε

α = ε (2)

Emissivity, reflectivity and transmission are therefore corresponding quantities

ε = 1 - ρ -τ (3)

or

ε = 1 - ρ for τ = 0 (4).

The thermal radiation emitted by a black radiator, which is dependent on temperature and wavelength, is determined by Planck's radiation density

described. Wafers are generally selective emitters, ie the emitted radiance must be scaled with the wavelength-dependent emissivity ε (λ) <1

K ' _λ (T) = ε (λ) K _λ (T) (6)

or but

K ' _λ (T) = (1- ρ (λ) - τ (λ)) K _λ (T) (7)

K ' _λ (T) = (1 - ρ (λ)) K _λ (T) for τ = 0 (8).

A system consisting of a hotliner and an overlying wafer is considered. The transmission τ _{hl of} the hotliner is zero due to its high doping. For Si wafers, this only applies depending on the doping from temperatures above about 600-700 ° C. It is assumed that the Si wafer is in this temperature range, ie τ _w = 0. There is a small hole in the center of the hotliner through which radiation can escape. This gives the hotliner a certain (very small) transmission τ _hl locally.

The intensities of the thermal radiation I _hl and I _w emitted by the wafer and hotliner in a narrow optical band around λ ₀ depend on the emissivities ε _hl = ε _hl (λ ₀ ) and ε _w = ε _w (λ ₀ ) with the corresponding blackbody radiation I _BB together. So it applies

I _w = ε _w I _{w, BB} = (1 - ρ _w ) I _{w, BB} (9)

respectively.

I _hl = ε _hl I _{hl, BB} = (1 - ρ _hl ) I _{hl, BB} (10).

The principle of operation can now be explained as follows. According to its temperature, the wafer emits heat radiation with the intensity I _w . This hits the hotliner, through the hole of which a portion of

I ₀ = τ _hl I _w (11)

exit. The remaining radiation is reflected according to the reflection coefficient of the hot liner ρ _hl , hits the wafer again, is reflected there again according to the reflection coefficient of the wafer ρ _w and hits the hot liner again. So a second part is added to the part that has already left

I ^0.1 = τ _hl (1 + ρ _hl ρ _w ) I _w (12).

The reflected portion makes a round again and hits the hotliner, etc. again

I ^{0, 1, 2,. . .} = τ _hl (1 + ρ _hl ρ _w + (ρ _hl ρ _w ) ² +...) I _w (13)

So there is a geometric series

which converges because of ρ _hl ρ _w <1:

Analogously, one can take into account the radiation emitted by the hotliner, which after the first reflection on the wafer takes the same course as that of the wafer, i.e. only has to be multiplied by ρ _w :

A pyrometer sees radiation intensity from the hole

emerge. It is believed that the hotliner plate and the wafer have identical temperatures. This implies that blackbody radiation from wafers and hotliners is considered the same

I _{w, BB} = I _{hl, BB} = I _BB (21)

can be accepted. The pyrometer now sees the intensity

I _tot is therefore neither dependent on the optical properties of the hotliner nor on those of the wafer, but only on the black body radiation I _{BB, which is} exclusively temperature-dependent at a specific optical wavelength.

Claims (23)

1. A method for the thermal treatment of substrates, in particular of semiconductor wafers, in which at least one substrate is heated in at least one reaction chamber with at least one heating source, wherein a plate is provided in parallel with the substrates to be treated, characterized in that the radiation in Gap between the substrate and the plate for determining the temperature of the substrate is optically detected. 2. The method according to claim 1, characterized in that that the substrate, the plate and the space a cavity between the substrate and the plate Form radiators whose temperature is measured optically becomes. 3. The method according to claim 1 or 2, characterized records that the in the space between the Radiation occurring from the substrate and the plate a hole emerges in the plate and for identification the temperature is measured. 4. The method according to claim 3, characterized in that the radiation emerging from the hole with a Pyrometer is measured. 5. The method according to any one of the preceding claims, characterized in that the radiation after Aus emerges from the hole so that the focus is on Radiation from the edge of the hole from the pyrometer is not recorded. 6. The method according to any one of the preceding claims, characterized in that the pyrometer the the space between the substrate and the plat  te emerging radiation in a selected Fre quenz, in a narrowband frequency range and / or in a broadband frequency range sums up. 7. The method according to any one of the preceding claims, characterized in that the substrate and the Plate in thermal equilibrium. 8. The method according to any one of the preceding claims, characterized in that the plate facing away te side of the substrate and the abge the substrate turned side of the plate each from radiant heaters be irradiated. 9. The method according to any one of the preceding claims, characterized in that the substrate and / or the plate is opaque. 10. Device for a thermal treatment of substrates ( 6 ), in particular semiconductor wafers, with a reaction chamber ( 2 ), at least one heating source ( 3 ) and a plate ( 9 ) which is arranged parallel to the substrate ( 6 ) to be treated, since characterized in that the plate ( 6 ) has a hole ( 14 ) for the exit of the radiation occurring in the intermediate space ( 15 ) between the substrate ( 6 ) and the plate ( 9 ). 11. The device according to claim 10, characterized in that a cavity emitter is formed by the substrate ( 6 ), the plate ( 9 ) and the intermediate space ( 15 ) between the substrate ( 6 ) and the plate ( 9 ). 12. The apparatus according to claim 10 or 11, characterized by an optical measuring device for measuring the radiation emerging from the hole ( 14 ) of the plate ( 9 ). 13. The apparatus according to claim 12, characterized in that the measuring device ( 18 ) is a pyrometer. 14. Device according to one of claims 10 to 13, characterized in that the distance between the substrate ( 6 ) and the plate ( 9 ) is small in terms of their diameter. 15. Device according to one of the preceding claims, characterized in that at least one heating source ( 3 ) is arranged both on the substrate and on the plate side of the substrate-plate arrangement. 16. The device according to one of claims 10 to 15, characterized in that a wide-angle lens ( 16 ) is arranged in front of the hole ( 14 ). 17. The device according to one of claims 10 to 16, characterized in that light lines are provided for transmitting the radiation between the radiation exit hole ( 14 ) and the pyrometer ( 17 ). 18. Device according to one of claims 10 to 17, characterized in that a plate ( 9 ) is arranged on both sides of the substrate ( 6 ). 19. Device according to one of claims 10 to 18, characterized in that the substrates ( 6 ) and / or plates ( 6 ) have a diameter of 100 to 300 mm and preferably a diameter of 150 to 200 mm. 20. Device according to one of claims 10 to 18, characterized in that the distance between the substrate ( 6 ) and the plate ( 6 ) is 2 to 10 mm and preferably 5 to 6 mm before. 21. Device according to one of claims 10 to 18, characterized in that the hole ( 14 ) has a diameter of 0.5 to 5 mm and preferably from 1 to 2 mm. 22. Device according to one of claims 10 to 21, characterized in that the substrate ( 6 ) is in contact with a contact thermocouple. 23. The apparatus according to claim 22, characterized in that the contact thermocouple is arranged at a point at which it is shielded by the plate ( 6 ) ge compared to the heat sources ( 3 ).