JP7014850B2 - Board holders and methods for bonding two boards - Google Patents

Description

The present invention relates to a substrate holder, a device having such a substrate holder, the use of such a substrate holder, a method for bonding two substrates, and a product manufactured by such a method, particularly a substrate. With respect to the laminate and the use of such a substrate holder for such a method.

In the semiconductor industry, multiple substrates, especially wafers, are aligned and coupled to each other in a variety of different ways. The bonding process is called bonding. Different bonding techniques need to be used depending on the material to be bonded for optimal results.

Now, in recent years, bonding technology at room temperature has become more and more established, but metals are bonded to each other, for example, by a diffusion process at high temperature and high pressure.

Substrates with surfaces having atoms that preferably form covalent bonds are directly bonded to each other by adhesive forces. However, the adhesive force does not exhibit the maximum bond strength between the surfaces because it is initially just a van der Waals bond. Appropriate processes, especially heat treatment, can convert such van der Waals bonds into covalent bonds. A bonding process in which two surfaces are bonded by forming a covalent bond is called a fusion bonding process. In recent years, it has become increasingly clear that maximizing the contact area, in particular, makes a decisive contribution to improving such bonding. This opens up entirely new possibilities for bonding such surfaces to each other at room temperature, especially without heat treatment, or even with very slight temperature increases. Recent measurements show that such optimizations can achieve bond strengths that are approximately equivalent to the theoretical strength of the materials bonded to each other.

Care must be taken to ensure that neither of the substrates is uncontrollably distorted before and / or between and / or after alignment, especially due to thermal loading, especially in the case of fusion bonding. Distortion causes expansion or contraction of the substrate, which in turn causes displacement and / or misalignment of the substrate's marks to be aligned with each other, especially the chips. This displacement and / or misalignment generally increases from the center to the edges. The error caused by this is known in the prior art, and especially in the semiconductor industry, by the name run-out. Compensating for this error is called runout compensation. This error is described in more detail below.

One of the most significant technical issues in permanent bonding of two boards is the alignment accuracy of the functional units between the individual boards. The boards can be aligned very accurately with each other by the alignment equipment, but distortion of the boards can occur during the bonding process itself. Due to the distortion thus generated, the functional units are not always properly aligned with each other in all positions. Alignment inaccuracies at specific points on the substrate can result in distortion, scaling errors, lens defects (magnification or reduction errors), and the like. In the semiconductor industry, all thematic areas related to such problems are included in the concept of "overlay". A corresponding introduction to this subject can be found, for example, in Mack, Chris's "Fundamental Principles of Optical Lithography-The Science of Microfabrication" (publisher WILEY, 2007, reprint 2012).

Each functional unit is computer designed prior to the actual manufacturing process. For example, conductor paths, microchips, MEMS, or any other structure that can be manufactured using microcontroller system technology is also designed in a CAD (computer aided design) program. However, during the manufacture of functional units, it has been found that there is always a discrepancy between an ideal functional unit built in a computer and an actual functional unit built in a clean room. Differences can be primarily due to hardware limitations, that is, technical engineering issues, but often due to physical limitations as well. That is, the resolution accuracy of the structure manufactured by the photolithography process is limited by the size of the aperture of the photomask and the wavelength of the light beam used. Mask strain is transferred directly to the photoresist. Mechanical linear motors can only reach reproducible positions within specified tolerances. Therefore, it is no wonder that the functional units of the board cannot be exactly equal to the structures constructed in the computer. Therefore, all substrates already have a negligible one from the ideal state before the bonding process.

Comparing the positions and / or shapes of the two functional units of the two boards facing each other, assuming that neither of the two boards is distorted by the coupling process, generally already in both functional units. It turns out that there is an incomplete match. This is because these functional units deviate from the ideal computer model due to the errors described above. The most frequent errors are in Figure 8 (http://commons.wikimedia.org/wiki/File:Overlay_typical_model_terms_DE.svg, 24.05.2013 and Mack, Chris's Fundamental Principles of Optical Lithography-The Science of Microfabrication. Chichester. (Publisher WILEY, p. 312, 2007, reprint 2012). As shown in the drawings, overlay error can be roughly divided into overall overlay error and local overlay error, or symmetric overlay error and asymmetric overlay error. The overall overlay error is uniform and therefore location independent. The overall overlay error produces the same deviation between two functional units located facing each other, regardless of position. Typical overall overlay errors are the errors I. and II. Due to the translation or rotation of both substrates relative to each other. Translation or rotation of both boards causes a corresponding translational or rotational error on the boards for all functional units located facing each other. Local overlay errors are location-related and are primarily caused by elastic and / or plasticity problems, especially elastic and / or plasticity caused by continuously propagating bonding waves. Caused by a problem. Of the overlay errors shown, errors III. And IV. In particular are referred to as "run-out" errors. This "runout" error is caused by distortion of at least one substrate, especially during the bonding process. Due to the distortion of at least one substrate, the functional unit of the first substrate is also distorted with respect to the functional unit of the second substrate. However, the errors I. and II. Can also be caused by the bonding process, but are usually significantly superimposed by the errors III and IV. Therefore, the errors I. and II. Are either extremely difficult to detect or become extremely difficult to detect. It becomes difficult to measure.

The biggest problem with bringing two substrates close together is that the ambient environment is generally not in a thermodynamic equilibrium with the substrate. A thermodynamic equilibrium always exists when all thermodynamic intensive variables, especially temperature, are equal for all subsystems to be considered. In many cases, one substrate, especially the one anchored to the lower substrate holder, has a relatively high temperature.

In many cases, it is desirable or even desirable to set a different temperature for the lower board, which is higher than the temperature of the upper board, in order to compensate for the previously described board runout error in a controlled manner. It is intended to do so. In this case, it may be necessary to control the temperature of the lower substrate accordingly, especially heating or cooling.

Here, when the first upper substrate fixed in position on the substrate holder according to the present invention is brought closer to the second lower substrate, the second lower substrate and, in particular, the entire lower substrate holder as a whole. The first substrate on the upper side is heated and thermally expanded to be subjected to a particularly complicated heating distribution. This heating distribution is obtained by the temperature / time curve. In this case, even the slightest temperature difference between the first and second substrates can cause significant distortion of the upper first substrate, or according to complex temperature transitions, the upper first. Can heat the substrate. The temperature of the upper substrate rises as the distance between the two substrates increases and remains constant in the saturation region for a short period of time, then decreases exponentially, especially with further processes, and then the boundary conditions. If does not change, it remains constant. The prior art has in particular the problem that the substrates are coupled to each other in a temperature region where the temperature changes as a function of time. That is, the bonding waves are exposed to different temperatures at different times, or in other words, at different positions, thereby producing the runout error described above.

Therefore, a task of the present invention is to provide an improved substrate holder and an improved method that can overcome the shortcomings of the prior art and, in particular, compensate for runout errors and, in particular, completely avoid them. Is.

The above problems are solved by the substrate holder according to the present invention, the apparatus according to the present invention, the use according to the present invention, the method according to the present invention, and the product according to the present invention, and the use according to the present invention, respectively, as described in the independent claims. ..

An advantageous development of the invention is described in the dependent claims. All combinations of at least two features described in the specification, claims, and / or drawings are also within the framework of the present invention. Within the stated range of values, the values themselves within the listed range should also be considered disclosed as limit values and can be claimed in any combination.

The core of the invention is controlled by any heat absorbed so that the fixed, especially upper substrate (also referred to below as the first substrate) can be adjusted as desired. The substrate holder according to the present invention, particularly the upper substrate holder (hereinafter, also referred to as the first substrate holder) is configured so that the substrate holder is discharged to the back side of the substrate holder in the state of being discharged, and is discharged through the heat exchanger there. To do.

A further important feature of the present invention is to optimize the thermal resistance of the device as expected so that the temperature difference ΔT can be adjusted as expected based on the present invention. be.

In particular, an important feature of the present invention is to adjust the desired temperature difference ΔT between the lower substrate and the upper substrate by appropriate selection of thermal resistance. This temperature difference ΔT is generally a function of time or a function of the spacing between the two substrates. However, according to the present invention, the temperature difference ΔT in the temperature region of temperature saturation of the lower substrate is mainly important, and in the following description of the present specification, d is added to this temperature region. In this temperature region d, it is required to keep the temperature difference ΔT constant. By adjusting and maintaining the temperature difference ΔT as desired, the adverse “runout” error can be reduced or even eliminated altogether.

The temperature difference ΔT, especially in the temperature saturation region d, is generally (i) by thermal resistance and / or (ii) especially by the heating element of the heating device in the lower substrate holder and / or (iii) cooling. It is adjusted as expected by the elements, especially the cooling fluid.

According to the present invention, the substrate holder has a position-fixing surface for holding the substrate, and the substrate holder is preferably and / or the position-fixing surface for exhausting heat from the position-fixing surface. Has a heat conductor to supply heat to the.

A further object of the present invention is an apparatus for bonding a first substrate to a second substrate, wherein the apparatus is one of the preceding embodiments for holding at least one of both the substrates. With respect to an apparatus having at least one substrate holder according to. In this regard, the description of the substrate holder in particular is referred to.

A further object of the present invention relates to the use of the substrate holder according to the present invention as the upper substrate holder.

A particularly independent further object of the present invention is a method for bonding a first substrate to a second substrate, wherein in the first step the substrates are brought into close proximity to each other, thereby the first. When the temperature of the substrates rises, the approach between the substrates is stopped in the second step, the distance between the substrates is kept constant, and when the distance is constant, the first step is performed for at least a predetermined period of time. The present invention relates to a method in which a constant temperature of a substrate is generated, and in a third step, both the substrates are bonded to each other at least temporarily within the period in which the first substrate is at a constant temperature.

Such a situation can also be explained as the temperature difference ΔT between the two substrates is constant in the well-defined temperature region d. Furthermore, the magnitude of the temperature difference ΔT can be adjusted by correctly selecting the thermal resistance.

A further object of the present invention relates to a product having a first substrate and a second substrate, particularly a product in which the substrates are bonded to each other by the method according to the present invention in a substrate laminate.

A further object of the invention relates to the use of such a substrate holder to hold the substrate during the implementation of such a method.

In general, the substrate holder, especially the upper substrate holder, should be thermally coupled to the ambient temperature as well as possible. This can result in heat supply and / or exhaust. By bringing the two substrates closer together, the upper substrate in particular is heated by the lower substrate or the lower substrate holder. In particular, the heat mass of the upper substrate holder is large, and the thermal conductivity of the substrate holder is as high as possible, so that heat is particularly discharged from the upper substrate. Therefore, in the substrate holder according to the present invention, the temperature distribution of the substrate holder when approaching the lower substrate or the lower substrate holder, and particularly the temperature distribution of the upper substrate can be adjusted as expected. It is configured as follows.

In this case, the thermal resistance of the substrate holder according to the present invention is designed so that the temperature adaptation of the thermal conductor, and thus the upper substrate, to the cooling fluid is performed as quickly and efficiently as possible. Therefore, thermal resistance is preferably minimized. The cooling fluid is preferably an ambient atmosphere. Therefore, the temperature of the cooling fluid is preferably room temperature.

By grasping the temperature / time curve, especially in the upper substrate holder or in particular the upper substrate, it is possible to identify the time point at which the throughput increases at the same time, which is most suitable for bonding. The corresponding process or method is also an important, especially independent, inventive feature of the invention.

All temperature distributions disclosed herein can be regarded as the temperature distribution of the substrate on the substrate holder, or the temperature distribution of the substrate holder. The thermal coupling between the substrate and the substrate holder is preferably so efficient that the temperature shift is negligible. In practice, the temperature of the lower substrate when the lower substrate holder is heated may be slightly lower than the temperature of the lower substrate holder. The temperature of the upper substrate is generally slightly higher than the temperature of the upper substrate holder according to the present invention. This slight temperature difference is related to the non-zero thermal resistance between the substrate holder and the substrate.

According to the substrate holder according to the invention, which is also referred to below as a sample holder, any heat generated as described above is controlled and released to the back side, where it is converted via a heat exchanger, according to the present invention. It is discharged from the board holder. Furthermore, the large thermal mass of the upper substrate holder in particular results in temperature stabilization of the upper substrate in particular, thereby minimizing thermal fluctuations in the surrounding ambient environment. A further important feature of the present invention is that the relatively large thermal mass stabilizes the temperature of the upper substrate or the temperature difference ΔT between the lower substrate and the upper substrate during the bonding process. be.

Furthermore, by grasping the heat transport passing through the substrate holder according to the present invention, it is possible to specify the temperature / time diagram particularly regarding the upper substrate holder or the upper substrate, and the substrate holder according to the present invention. By changing the parameters, it is possible to change this diagram.

The substrate holder according to the present invention can be used as an upper and / or lower substrate holder. The substrate holder according to the present invention is configured as an upper substrate holder in particular, so that the upper first substrate positioned on it is deformed in the direction of gravity unless it is particularly entirely positioned. To.

In the following, the surface roughness will be mentioned many times. Roughness is expressed herein as either arithmetic mean roughness, squared roughness, or average roughness depth. Arithmetic Mean Roughness Calculations, Square Roughness Calculations, and Average Roughness Depth Calculations are generally different for the same measurement path or surface, but within the same digit range. be. Therefore, the following numerical range for roughness should be understood as one of the values of arithmetic mean roughness, squared roughness, or average roughness depth.

The substrate holder according to the invention can heat and / or cool, among other things, the upper first substrate. The heat is discharged through the heat conductor, especially from the upper first substrate, and is preferably conducted to the cooling fluid. In this case, the heat conductor is a cooling body. However, it is also conceivable that the fluid is a heating fluid that discharges heat to the heat conductor to heat the upper first substrate. In this case, the heat conductor is a heated body.

The cooling fluid is preferably an ambient atmosphere. The temperature of the cooling fluid is preferably room temperature.

In a preferred embodiment, the heat conductor has ribs for discharging and / or supplying the heat, particularly on the side of the heat conductor opposite to the position-fixed surface (hereinafter also referred to as the back side). .. These ribs can be placed, among other things, over the entire backside of the heat conductor, which makes it possible to improve heat exchange.

Heat can be distributed through the ribs along a relatively large surface, the so-called rib surface. The ribs can be placed, among other things, perpendicular to the fixed surface. The ribs are preferably arranged parallel to each other. If a thermal conductor that functions as a cooling body is used, it is a cooling rib. When a heat conductor that functions as a heating body is used, the ribs can also be referred to as heating ribs, and these heating ribs optimally conduct heat from the fluid to the heat conductor. Hereinafter, the rib will be described in the following description. Unless explicitly stated, heat conductors are primarily considered cooling bodies, ribs are considered cooling ribs, and fluids are considered cooling fluids in the following description.

Embodiments of the substrate holder according to the present invention are preferably designed such that the ribs are arranged within the capsule encapsulation, eg, the housing. The capsule encapsulation section preferably has at least two access sections. One of the access units is used for fluid supply and the other is used for drainage. This allows the fluid to flow continuously through the ribs of the heat conductor, especially in a spatially isolated state from the surrounding environment. Such a compact structure also makes it possible to isolate embodiments according to the invention from surrounding components. If the cooling is gas cooling, especially air cooling, it may be sufficient to have a gas stream, especially an air stream, flowing through the ribs by a fan to ensure efficient cooling. In a very particularly preferred embodiment, the cooling ribs are cooled only by the ambient atmosphere.

Preferably, the flow velocity of the fluid can be controlled. In this case, the flow velocity is faster than 1 mm / sec, preferably faster than 1 cm / sec, even more preferably faster than 10 cm / sec, and most preferably faster than 1 m / sec. The compact capsule encapsulation also allows the fluid to be placed under pressure. In this case, the pressure of the fluid preferably corresponds to the ambient pressure. However, the fluid can also be used under overpressure. In this case, the pressure is greater than 1 bar, preferably greater than 2 bar, even more preferably greater than 5 bar, most preferably greater than 10 bar, and most preferably greater than 20 bar. The supply of fluid to the capsule encapsulation and thus to the ribs is preferably carried out via a hose system connected to the access.

Optional cooling and heating elements In addition to the heat conductors described below and the heat exchangers behind them, the substrate holders according to the invention are additional cooling and / or heating elements that can be actively controlled. Can have. These additional cooling and / or heating elements are preferably incorporated within the substrate holder according to the invention, especially in the heat conductor. It is also conceivable to install cooling and / or heating elements around the heat conductor to keep the heat conductor as homogeneous as possible and not to cause temperature jumps due to additional incorporated components.

The heating element is preferably an inductive heater. However, since temperature compensation only needs to be performed for a relatively small temperature difference, it is possible to control the temperature more accurately, more quickly, and more efficiently, and the temperature of the heat conductor is controlled by radiant heat. It is also conceivable to install an infrared source that can be raised in the temperature range on the side of the thermal conductor.

The cooling element can also be an additional installed Pelche element, which is an additional substrate holder, especially the heat conductor, according to the invention, independent of the original heat conductor according to the invention. Allows for cooling. The Pelche element is preferably mounted on the outside of the thermal conductor so as not to disrupt the material homogeneity of the thermal conductor.

The original inventive feature of the present invention is a thermal conductor.

Thermal Conductor A thermal conductor is a component that has as large a thermal mass as possible. The heat mass is the product of the specific heat capacity and the mass of the object. If the density distribution is constant, the product of density and volume may be used instead of mass.
C _th = m ・_cm = ρ ・ V ・_cm

The concept of thermal mass is mainly used in the engineering field. In the scientific field, heat capacity, which is a more commonly used concept, is mainly used. The unit of heat capacity is J / K. Heat capacity is a measure of an object's ability to store heat at a particular temperature. An object with a large heat capacity is a heat storage device that can be used as a cushioning element.

Generally, when the temperature Tk of the cooling fluid used is different from the temperature of the upper substrate, the temperature gradient is lowered via the heat conductor. The average temperature can be considered instead of the temperature gradient. In the following description of the present specification, the temperature gradient or the average temperature is referred to as Tw. The temperature of the cooling fluid is preferably kept constant during the implementation of the process according to the invention, while the temperature gradient or average temperature Tw generally varies. The temperature Tw preferably always coincides with the temperature of the upper substrate and deviates only slightly from this temperature.

An important recognition by the present invention is that the temperature of the upper substrate and the temperature of the thermal conductor according to the invention or the temperature of the upper substrate holder according to the invention, especially if the thermal resistance Rth4 between the two substrates is infinite. Should match the temperature of the cooling fluid, especially the ambient temperature. However, due to the finite value of the thermal resistance Rth4, a heat flow rate from the lower substrate to the upper substrate can occur.

According to the present invention, in order to reduce, or preferably completely eliminate, the "runout" error, in particular the temperature difference ΔT between the spacing d between the substrates is known and adjusted as desired. It is especially important to be able.

An object according to the present invention of the embodiment according to the present invention is to discharge the temperature of the substrate in a controlled state as much as possible and to stabilize the temperature of the substrate accordingly, so that the heat conductor has a heat capacity as high as possible. The heat capacity of the heat conductor is as large as possible to allow efficient heat storage or to compensate for heat fluctuations as efficiently as possible. The temperature stability is also reflected in the stability of the temperature difference ΔT. For the majority of solids, the heat capacity at a constant volume differs only slightly from the heat capacity at a constant pressure when the temperature and pressure are moderate. Therefore, in the following description, these two heat capacities are not distinguished. Furthermore, the specific heat capacity is shown. The specific heat capacity of the thermal conductor is particularly greater than 0.1 kJ / (kg · K), preferably greater than 0.5 kJ / (kg · K), even more preferably greater than 1 kJ / (kg · K), and most. It is preferably larger than 10 kJ / (kg · K), and most preferably larger than 20 kJ / (kg · K). If the density and geometry of the heat conductor are known, the specific heat capacity can be converted to absolute heat capacity by the above equation.

The material of the heat conductor should have the highest possible thermal conductivity, as the heat must be transported as quickly as possible. The thermal conductivity is between 0.1 W / (m · K) and 5000 W / (m · K), preferably between 1 W / (m · K) and 2500 W / (m · K), and even more preferably 10 W. It is between / (m · K) and 1000 W / (m · K), most preferably between 100 W / (m · K) and 450 W / (m · K). Copper, which is the most commonly used constituent material for discharging heat, has a thermal conductivity of, for example, about 400 W / (m · K). Thermal conductivity defines how much energy is delivered per unit time over a given distance at a given temperature difference. The energy or amount of heat transported per unit time is called the heat flow. The heat flow is greater than 1 J / sec, preferably greater than 10 J / sec, even more preferably greater than 100 J / sec, most preferably greater than 200 J / sec, and most preferably greater than 500 J / sec.

The heat conductor is preferably actively or passively cooled behind the heat conductor. Passive cooling is carried out, among other things, by releasing heat through the largest possible surface area. Active cooling is carried out by the cooling fluid. The cooling fluid can be a gas or a liquid. For example, the following can be considered:
● Liquid, especially ○ Water ○ Oil ● Gas, especially ○ Noble gas ・ Helium ・ Argon ○ Molecular gas ・ HFCKW
・ HFKW
・ FCKW
・ PFKW
・ CO2
・ N2
・ O2
● Mixed gas, especially ○ Air, especially ・ Ambient air

The cooling fluid absorbs heat through the heat conductor, thereby heating it and at the same time cooling the heat conductor. The heated cooling fluid is preferably circulated in the cooling circuit to dissipate heat at different points in the circuit system, where it is cooled again and fed back to the cooling circuit again. Preferably, cooling gas is used because it is easy to handle. When the cooling fluid is ambient air, cooling is carried out by discharging heat from the heat conductor into the ambient air. The locally heated ambient air then propagates through the ambient atmosphere, which results in temperature adaptation and cooling.

Dispersing heat through a relatively large surface improves the efficiency of heat dissipation or heat transfer to the cooling fluid. By consciously increasing the surface roughness, the surface area can be further increased. In this case, the roughness is greater than 10 nm, preferably greater than 100 nm, even more preferably greater than 1 μm, most preferably greater than 10 μm, and most preferably greater than 100 μm.

It is also conceivable to use a heat conductor without ribs, which simplifies the manufacture of the heat conductor.

In a further embodiment of the present invention, it may be conceivable to provide open pores at least on the front side of the thermal conductor. In this case, the pore size is greater than 100 nm, preferably greater than 1 μm, even more preferably greater than 10 μm, most preferably greater than 100 μm, and most preferably approximately 1 mm. The cooling fluid passes through the open pores, at which time it absorbs heat more efficiently based on its large surface area. In order to further increase the surface area of the rib, it is conceivable to provide open pores only in the rib.

The main subject of the substrate holder, especially the thermal conductor, according to the present invention is to regulate and stabilize the temperature of the substrate, or to regulate the temperature difference between the lower substrate and the upper substrate and to stabilize the temperature difference. Is. In addition to this, the substrate holder according to the invention supplies heat to the substrate and / or exhausts heat from the substrate depending on the need for cooling and / or heating of the substrate. According to the substrate holder according to the present invention, the maximum temperature or the temperature difference ΔT between the upper substrate and the lower substrate can be adjusted as desired, and moreover, both substrates in particular. The temperature stability of the maximum temperature or the temperature difference ΔT is guaranteed for the same period as required for bonding, and even more preferably for a longer period.

Further description refers to a plurality of embodiments according to the invention, each of which differs from at least one feature. All the embodiments according to the present invention described above can be optionally combined with each other so as to be able to create a further corresponding embodiment according to the present invention in which the plurality of features described above are combined.

In an exemplary embodiment of the invention, the substrate holder according to the invention has a separate position fixing portion on which the thermal conductor is placed. That is, the heat conductor and the position fixing portion are two components that are different from each other but are coupled to each other. The most efficient thermal coupling of the two components is carried out through the flattest surface possible. In this case, the roughness of the surface of the position fixing portion or the heat conductor in contact with each other is less than 100 μm, preferably less than 10 μm, still more preferably less than 1 μm, most preferably less than 100 nm, and most preferably less than 10 nm. be. Thermal transfer can be further improved by using a thermally conductive paste.

In a more preferred embodiment, the fixed surface is integrally formed with the thermal conductor. In other words, the heat conductor itself is configured as a position fixing portion. The heat conductor and the position fixing portion or the position fixing surface are integrally formed. However, it does not have a decisive effect on the functionality of the present invention and will not be dealt with, illustrated or described further. According to the embodiment of the present invention, since there is no boundary surface between the position fixing portion and the heat conductor, it is possible to improve the heat conduction.

Since the embodiment according to the invention in which the thermal conductor is integral or consists of one part is the optimum embodiment according to the present invention, all the modifications below are related to this basic type. do. Therefore, the fixed position and the heat conductor are used as synonyms in the following description.

In a further particularly preferred embodiment according to the invention, the substrate holder has at least one, in particular movable, preferably driveable, deformable element for deforming the substrate, wherein the at least one deformable element is: It is preferably arranged in the center of the substrate holder. The at least one deforming element is, among other things, movable perpendicular to the position-fixed surface or the position-fixed substrate, and can be particularly driveable. The at least one deformable element is preferably configured so that the substrate can be deformed in a direction away from the position fixing surface. The substrate holder or thermal conductor can have a particularly centrally formed and / or consistently extending hole in which at least one deforming element is particularly mobile, preferably. Are driveably arranged or this hole allows access to at least one deforming element capable of deforming a fixed substrate. At least one variant is, for example:
● Pin ● Spike ● Ball ● Nozzle, especially ○ Gas nozzle

The deforming element is manipulated or controlled so that the substrate can be deformed at least locally, preferably centered, by being driven as desired. In this case, the deformation is preferably concave when viewed from the side of the deforming element. Deformation is used, among other things, for the process of dissociating a substrate from a fixed part or fixed surface.

In a further embodiment according to the invention, the heat conductor has at least one on the position-fixed surface to ensure that the contact between the substrate and the position-fixed surface or the contact between the substrate and the material of the heat conductor is as low as possible. It has two recesses and / or recesses. This reduces the so-called effective position fixed surface area. The effective position-fixed surface area is the area of the position-fixed surface that is actually in contact with the substrate. Preferably, at least one recess is placed on the fixed surface so that the substrate can be held away from the fixed surface. The advantage of the embodiment according to the present invention is that the contamination of the substrate by the surface of the thermal conductor is reduced. In order to carry out heat transfer efficiently, a gas having a correspondingly high thermal conductivity and a correspondingly high heat capacity is introduced into, among other things, into at least one recess and / or recess. Can be done. In this case, the substrate is positioned only on a few position fixing elements, especially on the peripheral and / or centered position fixing elements. Such embodiments are disclosed in WO 2013/023708 (WO2013 / 023708A1), and the disclosures of this document relating to these embodiments are expressly included in the disclosures of this application.

In a further embodiment according to the invention, protrusion-shaped (protrusions) and / or needle-shaped and / or column-shaped elements are arranged in at least one recess, which allows the substrate to be displaced from the position-fixed surface. They can be held apart and these elements can extend sharply, especially towards the substrate. These elements reach the surface of the thermal conductor and support the fixed substrate. In order to ensure the thermal coupling between the positioned substrate and the thermal conductor, in this embodiment of the invention, a fluid having a large heat capacity is placed in the intermediate space of the protrusions and / or the needles and / or columns. It is also possible to let it flow.

Positioning Elements All embodiments of the present invention according to the present invention can position substrates, especially wafers, and even more preferably semiconductor wafers. In this case, the positioning can be performed by any arbitrary positioning element. Preferably, the position fixing element for fixing the position of the substrate is disposed on the inside of the position fixing surface, and / or on the surface, particularly entirely. The possible ones are as follows.
● Vacuum type position fixing ● Static type position fixing ● Magnetic type position fixing ● Mechanical position fixing, especially ○ Clamp ● Adhesive type position fixing, especially ○ Position fixing by adhesive film

A vacuum-type position-fixing or vacuum passage (hereinafter also referred to as a vacuum channel), which is dispersed and arranged over the position-fixing surface, is particularly preferable. The vacuum-type position fixing consists of a plurality of vacuum channels terminated by a vacuum opening provided on the position fixing surface of the substrate holder.

In another embodiment according to the invention, the vacuum channels are coupled to each other so that the vacuum channels can be exhausted and / or injected simultaneously.

In another embodiment of the invention, at least the individual vacuum channels are coupled together to form a corresponding group of vacuum channels. In this case, each vacuum channel group can be individually controlled, whereby the position fixing and / or dissociation for each division of the substrate can be realized. In a particular embodiment according to the invention, the plurality of vacuum openings are arranged in a plurality of centered circles, each having a different radius, to form a group of vacuum channels. Advantageously, all vacuum channels contained in the same circle are controlled simultaneously, thereby controlling the positioning and / or dissociation of the substrate to start in the center and proceed radially outward. Can be done. This provides a particularly efficient means for fixing and / or dissociating the substrate in a controlled manner.

Thermal Resistance: Equivalent Circuit Diagram A further important inventive feature of the present invention is, among other things, the optimization of heat flux through the substrate holder according to the present invention. The heat flux between the heat source and the heat sink is decisively affected by the thermal resistance. Each static multi-particle system, and thus fluids such as gases and liquids, as well as solids has thermal resistance. The definition of thermal resistance is well known to those of skill in the art. Thermal resistance is not a pure material parameter. Thermal resistance depends on thermal conductivity, thickness, and cross-sectional area.
R = d / (A · λ)

In the following description of the present specification, it is assumed that the heat flow always flows through the same cross-sectional area, so that the thermal resistance at a certain cross-sectional area is the thermal conductivity and thickness of each material under consideration. Should be considered a function of. Thermal resistance is abbreviated in the drawings using Rth and subscripts. According to the present invention, there are, among other things, eight related thermal resistances. Rth1 to Rth8 are (i) the thermal resistance of the lower substrate holder, (ii) the thermal resistance of the fluid or vacuum between the lower substrate holder and the lower substrate, and (iii) the thermal resistance of the lower substrate. Resistance, (iv) thermal resistance of fluid or vacuum between both substrates, (v) thermal resistance of upper substrate, (vi) thermal resistance of fluid or vacuum between upper substrate and upper substrate holder, (v) vii) The thermal resistance of the heat conductor, and (viii) the thermal resistance of the fluid flowing between the cooling ribs in particular.

The heat flow is directly proportional to the temperature difference applied between the heat source and the heat sink. Thermal resistance is a constant of proportionality. Therefore, the following applies:
R = (1 / ΔT) · (dQ / dt)

In particular, a further important inventive feature of the present invention is to minimize the thermal resistance above and / or below the substrates and maximize the thermal resistance between the substrates. Therefore, according to the present invention, the thermal resistance should be designed specifically as follows:
Rth1 is minimized by selecting a material with a particularly high thermal conductivity.
Rth2 is minimized by choosing a fluid with a particularly high thermal conductivity.
Rth3 should be minimized by choosing a substrate with high thermal conductivity.
Rth4 is maximized by passing a gas with particularly low thermal conductivity and / or by vacuum and / or by optimized process control, especially by clever selection of spacing.
Rth5 should be minimized by choosing a substrate with high thermal conductivity.
Rth6 is minimized by choosing a fluid with a particularly high thermal conductivity.
Rth7 is minimized by selecting a material with a particularly high thermal conductivity, and / or Rth8 is minimized by selecting a fluid with a particularly high thermal conductivity.

Particularly important features of the embodiments according to the present invention are that the temperature of the upper substrate or the temperature difference ΔT between the lower substrate and the upper substrate can be adjusted as desired, and the bonding process. It is to keep it as constant as possible during the period. This is achieved by correctly selecting the thermal resistance based on the present invention. By maximizing the thermal resistance Rth4, the heat flow from the lower substrate to the upper substrate is minimized and, on the contrary, completely shut off. However, since it is not possible to completely shut off the heat flow, in reality, the temperature of the upper substrate always changes. The temperature difference ΔT is particularly less than 20 ° C., preferably less than 10 ° C., even more preferably less than 5 ° C., most preferably less than 1 ° C., and most preferably less than 0.1 ° C.

On the other hand, in particular, the temperature of the lower substrate should be able to be precisely adjusted by the heating device in the lower substrate holder. In particular, the temperature of the lower substrate should match the temperature of the lower substrate holder. The lower substrate holder is particularly temperature controlled to less than 100 ° C, preferably less than 75 ° C, even more preferably less than 50 ° C, most preferably less than 30 ° C.

Furthermore, the temperature of the upper substrate, among other things, should match the temperature of the cooling fluid and / or the thermal conductor. In a very specific embodiment according to the invention, the temperature of the cooling fluid particularly coincides with the ambient temperature. This is especially true when the atmosphere itself is used as the cooling fluid. The cooling fluid is particularly temperature controlled below 100 ° C, preferably below 75 ° C, even more preferably below 50 ° C, and most preferably below 30 ° C. In a very specific embodiment according to the invention, the ambient atmosphere is used as the cooling fluid and thus has room temperature or ambient temperature.

The diameter of the substrate cannot be changed. The thermal conductivity and thickness of the substrate used are also often predetermined by manufacturing conditions and are often not available for optimization according to the present invention. By correctly selecting the thermal resistance based on the present invention, the heat flux from the lower substrate to the upper substrate is preferably minimized, and the heat flux from the upper substrate to the cooling fluid is maximized. .. Therefore, the temperature difference ΔT remains constant according to the present invention.

A further goal of thermal resistance selection according to the present invention is to keep the temperature of the upper substrate constant, especially at ambient temperature, and thus minimize the effects of other heat sources, especially the heat source of the lower substrate. Is to become. If the temperature of the lower substrate holder, and thus the temperature of the lower substrate, is kept constant, this will be between the upper substrate and the lower substrate, especially during the bonding process in the temperature region d. It is synonymous with maintaining the temperature difference ΔT of. This is achieved especially by maximizing the thermal resistance Rth4 between the substrates. On the other hand, the temperature T1u of the lower substrate should be controllable as efficiently as possible by the heating device. In this case, Tp is attached to the temperature of the lower substrate holder. Preferably, the temperature Tp of the lower substrate holder is the same as the temperature T1u of the lower substrate at any time point. The conduction of heat from the heater to the lower substrate is achieved, especially by minimizing the thermal resistances Rth1 and Rth2.

Process The method according to the present invention or the process according to the present invention can be described based on a so-called temperature / time diagram. In this temperature / time diagram, the temperature, particularly the temperature T of the substrate positioned and fixed to the substrate holder according to the present invention, is shown as a function of the time t (temperature graph). In this case, the temperature is shown on the vertical axis at the left end of the temperature / time diagram. It is also possible to describe an interval / time curve (interval graph) in the temperature / time diagram, and from this curve, it is possible to read at what time and how large the interval between the two substrates is. In this case, the vertical axis of the interval / time curve is shown at the right end of the temperature / time diagram. Since the interval / time curve shows the interval from mm to nm, it is preferably logarithmically scaled (scaled). However, for clarity, the interval / time curves in the drawings are shown by linear scaling. In the following description, for the sake of simplification, only the temperature / time diagram, or the Tt diagram for short, will be referred to. In addition to the Tt diagram relating to the position-fixed substrate, it is also possible to explain the Tt diagram relating to the substrate holder according to the present invention. However, these two Tt diagrams differ only slightly from each other, especially in view of the minimum deviation along the temperature axis. Therefore, in the following description of the present specification, the Tt diagram is used synonymously with respect to the temperature / time diagram of the position-fixed substrate and / or the substrate holder according to the present invention. This assumption is justified, especially when the thermal resistances Rth2 and Rth6 are minimal. In this case, the thermal coupling between the substrate holder and the substrate is so good that it can be assumed that the temperature of the substrate holder and the temperature of the substrate are more or less the same.

Each diagram can generally be divided into six sections, especially time sections.

In the first first division a, the substrates are brought close to each other from a state where the distance is relatively large. The distance between the two substrates in category a is greater than 1 mm, preferably greater than 2 mm, even more preferably greater than 3 mm, most preferably greater than 10 mm, and most preferably greater than 20 mm. The movement of the substrate in category a is a temperature rise due to the other substrate, in particular the lower second substrate, or the other substrate holder which can be heated to a temperature generally above room temperature, in particular the lower second substrate holder. Does not cause temperature rise due to. Between the two substrates, the effect of heat radiation from the second lower substrate or the second lower substrate holder and / or the effect of thermal convection of the gas around the upper first substrate. As the spacing decreases, a moderate temperature rise occurs in the upper first substrate.

This region b of moderate temperature rise is called the coarse approach region. In this case, the distance between the two substrates is between 10 mm and 0 mm, preferably between 5 mm and 0 mm, even more preferably between 1 mm and 0 μm, and most preferably between 100 μm and 0 μm.

When the substrates are further brought closer to each other, the temperature of the upper first substrate at the end of the coarse approach region b rises sharply. A kind of thermal bond occurs between the two substrates. Since the distance / diameter ratio between the substrate spacing and the substrate diameter is small, the first substrate on the upper side is heated by heat. Since the ambient gas heated by heat radiation can no longer diffuse at a sufficient rate from the intermediate space between the two substrates, it is preferable to transfer heat directly from the lower second substrate to the upper first substrate. Communicate Similar considerations apply to thermal radiation, which may only reach the surface of the first substrate on the upper side substantially. This region where the substrate is strongly heated is called the close proximity region c. In this case, the distance between the two substrates is between 1 mm and 0 mm, preferably between 100 μm and 0 μm, even more preferably between 10 μm and 0 μm, and most preferably between 1 μm and 0 μm.

The transition of the temperature distribution from the close proximity region c to the so-called temperature saturation region d is preferably carried out by a transition that is mathematically as stationary as possible but indistinguishable. It is also conceivable to carry out the transition continuously, thereby making it impossible to uniquely carry out the separation between the regions c and d. The shape of the temperature / time diagram looks like a "shark fin". However, other shapes are also conceivable.

The bonding process according to the present invention is preferably carried out in the temperature saturation region d. The translational approach between the substrates is stopped, i.e. the spacing between the substrates remains constant. At this point, the upper first substrate has a constant temperature T4o for a well-defined period t1 corresponding to the length of the temperature saturation region d. The constant temperature T4o means that the maximum temperature fluctuation is 4K at the maximum, preferably 3K at the maximum, more preferably 2K at the maximum, 1K at the maximum, and 0.1K at the maximum. .. The distance between the two substrates is constant in this region, between 1 mm and 0 mm, preferably between 100 μm and 0 μm, even more preferably between 10 μm and 0 μm, and most preferably between 1 μm and 0 μm. In a particular embodiment according to the invention, it is also possible to bring both substrates closer together in region d. However, it should be noted that in this case, sufficient time must still be left for the original bonding process. Further, in the temperature saturation region d, the temperature difference ΔT between the lower substrate and the upper substrate remains constant. In this case, the variation of the temperature difference ΔT is less than 4K, preferably less than 3K, even more preferably less than 2K, most preferably less than 1K, and most preferably less than 0.1K. In particular, the temperature difference ΔT can be adjusted accurately and reproducibly by the choice of thermal resistance and / or heat source, especially the heater in the lower substrate holder, and / or by the choice of heat sink, especially the cooling fluid.

In particular, the period t1 in which the interval d3 is constant and the constant temperature T4o is generated is longer than 5 seconds, preferably longer than 10 seconds, still more preferably longer than 15 seconds, and even more preferably longer than 20 seconds. Long, most preferably longer than 40 seconds. This advantageously leaves ample time for the bonding process.

Furthermore, the period t1, the interval d3, and / or the constant temperature T4o, among other things, are performed prior to the first step, especially by experience, preferably taking into account the temperature of the second substrate. / Or determined in consideration of the substrate holder, the thermal conductor, and / or the material of the substrate and / or the approach speed. Therefore, with particular advantage, the method can be defined or calibrated prior to the first step so that the optimum parameters of the method can be determined.

The bonding process, in particular the fusion bonding process, requires a period t2, particularly less than or equal to the length of the period t1. A more important feature according to the present invention is that the bonding process is preferably carried out within the period of the temperature saturation region d at a given temperature T4o. This has the advantage that the bonding process can be performed without changing the temperature of the first substrate, thereby avoiding, or at least reducing, the runout error described above. It will be possible.

In the cooling region e that follows, the upper first substrate is cooled particularly exponentially.

Finally, in the region f that follows, a constant saturation temperature is generated that is higher than the initial temperature of the upper first substrate in the first section a before the approach process. However, this saturation temperature is generally lower than the temperature of the lower second substrate or substrate holder. It is also conceivable to carry out the bonding process in the region f at the temperature T6o.

Preferably, before using the method according to the invention, all required physical parameters that make it possible to obtain an accurate judgment regarding the temperature / time diagram are sought. The present invention is made by varying the physical parameters during the original bonding process until it is guaranteed that a temperature / time distribution that allows optimal bonding of both substrates and also results in a reasonable throughput is produced. It is necessary to change the method by. By using the corresponding thermal conductors according to the invention, which have the corresponding heat mass, the correct cooling fluid, the correct cooling fluid pressure, the correct cooling fluid flow velocity, the correct approach distribution, etc., the saturation temperature T4o in the region d, the region d The period t1 and all other desired regions of the temperature / time diagram can be adjusted accordingly.

Once the system was calibrated for temperature-time behavior, it was also ensured that the upper first substrate had a well-defined temperature at a well-defined time point, and this temperature was reached. It is also guaranteed that from the starting point, a well-defined time is available to perform the original bonding process, especially by position-fixing bending and / or release caused by vacuum. The fact that bonding is already possible from an early stage of the region d provides two important features that are the basis of the present invention. First, it allows early initiation of bonding, which significantly increases throughput. Second, it is guaranteed that the substrate will have a very constant temperature within a well defined period. This makes it possible to completely avoid the run-out problem, which is really well known in the prior art, according to the present invention. It is guaranteed that both substrates have a substantially constant temperature during the period of region d and that the temperature of region d does not change substantially during the bonding process. In this regard, it should be reiterated that the constant temperature conditions described above do not mean that both substrates must have the same temperature. It may be highly desirable to preheat at least one of both substrates to a relatively high temperature or to cool it to a relatively low temperature, by forcing thermal expansion as expected. The desired compulsory board dimensions are adjusted, which only results in the matching of both functional units on both boards. However, according to the present invention, these once-adjusted temperatures are kept constant during the bonding process.

In any of the methods according to the invention described above, the substrate can be pretreated and / or posttreated. The following can be considered as pretreatment.
● Cleaning, especially ○ By chemical processes, especially by liquids, especially
● By water ○ By physical process, especially by sputtering
● By ions, especially
○ By plasma activation
● By uncharged particles ● Grinding ● Polishing ● Alignment, especially ○ Mechanical alignment and / or ○ Optical alignment ● Sedimentation

The following can be considered as post-processing.
● Cleaning, especially ○ By chemical processes, especially by liquids, especially
● By water ○ By physical process, especially by sputtering
● By ions
● By uncharged particles ● Grinding ● Polishing ● Inspection, especially ○ Bonding interface inspection, especially ・ Regarding defective parts (voids) ・ Regarding alignment error, especially
● Regarding run-out error ● Heat treatment, especially ○ In-furnace ○ Heater plate ● Especially, re-peeling of the substrate by the method described in International Publication No. 2013/0911714 (WO2013 / 091714A1)

According to the embodiment of the present invention, it is possible to compensate for the run-out error, which is particularly known in the prior art. Therefore, in some cases, the alignment accuracy has been sufficiently minimized for the purpose of separating the substrates from each other again by a special method, particularly by the method described in International Publication No. 2013/091714 (WO2013 / 091714A1). It is especially important to inspect the bonding interface after bonding both substrates to confirm. This avoids the loss of both boards or the entire board laminate and allows the boards to be realigned and bonded to each other as needed.

The alignment accuracy achievable by the apparatus according to the invention or the process according to the invention is better than 100 μm, preferably better than 10 μm, even more preferably better than 500 nm, and most preferably better than 200 nm. Most preferably, it is better than 100 nm. Alignment accuracy is the same, especially at any position in the substrate laminate, which is a decisive and characteristic feature of successful runout error compensation. In this case, the standard deviation of the alignment accuracy calculated by averaging all the alignment errors of the substrate laminate is less than 1 μm, preferably less than 500 nm, even more preferably less than 250 nm, most preferably less than 100 nm, most preferably less than 100 nm. Is less than 50 nm.

After the bonding process according to the present invention, if the result of the inspection, which is optional but preferable to be carried out, is positive, the substrate is heat-treated as necessary. This heat treatment is especially necessary for fusion bonded substrates. In this case, the heat treatment produces permanent bonding of both substrates that can no longer be dissociated. If heat treatment of the substrate is no longer required after the bonding process according to the invention, heat treatment is omitted accordingly.

In the method according to the invention, the bonding of both substrates is carried out by deforming the first substrate, which is particularly upper in the region d. The deformation is preferably carried out in the center by the deformation elements already described. The advantage of the first process according to the present invention is particularly throughput. Since the bonding process has already been performed in Category d and there is no need to wait for the upper first substrate to cool, the throughput (ie, the number of substrates that can be processed per unit time using the embodiments according to the invention) has been conventionally determined. It can be increased compared to technology. Cooling the upper first substrate is a process of adapting to an ambient temperature determined primarily by the ambient atmosphere and / or by the lower second substrate or the lower second substrate holder.

In another process according to the invention, the bonding of both substrates is carried out by deforming the first substrate, especially on the upper side, in the region f. The deformation is preferably carried out in the center by the deformation elements already described.

The temperatures T4o, T6o can be varied and optimally adapted by the substrate holder according to the invention, in particular by thermal mass, cooling elements and equipment, cooling process, cooling fluid and the like.

Further advantages, features, and details of the present invention will become apparent with reference to the drawings from the following description of preferred embodiments.

FIG. 3 is a schematic cross-sectional view of the first embodiment of the substrate holder according to the present invention, which is not according to the scale. FIG. 3 is a schematic cross-sectional view of the second embodiment of the substrate holder according to the present invention, which is not in scale. FIG. 3 is a schematic cross-sectional view of the third embodiment of the substrate holder according to the present invention, which is not in scale. FIG. 3 is a schematic cross-sectional view of the fourth embodiment of the substrate holder according to the present invention, which is not according to the scale. FIG. 5 is a schematic cross-sectional view of the fifth embodiment of the substrate holder according to the present invention, which is not in scale. 6a is a non-scaled schematic cross-sectional view of the first step of the method according to the invention, FIG. 6b is a non-scaled schematic cross-sectional view of the second step, and FIG. 6c is a non-scaled schematic cross-sectional view. 3 is a non-scaled schematic cross-sectional view of step 3, FIG. 6d is a non-scaled schematic cross-sectional view of the fourth step, and FIG. 6e is a non-scaled schematic cross-sectional view of the fifth step. FIG. 6f is a schematic cross-sectional view of the sixth step, not in scale. FIG. 7a is a schematic diagram of a first temperature / time diagram and an interval / time diagram, and FIG. 7b is a schematic diagram of a second temperature / time diagram and an interval / time diagram. It is a schematic diagram of a possible overlay error. It is a schematic diagram of a heat equivalent circuit.

In the drawings, the same components and components having the same function are designated by the same reference numerals.

FIG. 1 shows a first embodiment of the present invention of a substrate holder 1 having a position fixing portion 4 and a thermal conductor 2. The position-fixing portion 4 has a position-fixing element 5, particularly a vacuum passage, and more preferably a vacuum passage that can be individually controlled, and these position-fixing elements 5 place a first substrate 11 (not shown) on the position-fixing surface. The position can be fixed to 4o. The thermal conductor 2 preferably has a plurality of ribs 3, which can release heat to a fluid (not shown) through the rib surface 3o of the ribs 3. The heat conductor 2 is coupled to the position fixing portion 4 via the boundary surface 6.

FIG. 2 shows a preferred second embodiment of the present invention of the substrate holder 1'according to the present invention, wherein the substrate holder 1'has a thermal conductor 2'that also functions as a position fixing portion. In other words, the heat conductor 2'and the position fixing portion are formed from one portion, that is, integrally, unlike the embodiment of FIG. 1. This eliminates the presence of a interface between the position fixation and the thermal conductor 2', which is advantageous to the fluid from the first substrate 11 (not shown) flowing around the rib 3 (not shown). There are no thermal barriers that impede the transport of heat.

FIG. 3 shows an even more preferred third embodiment of the substrate holder 1 ″ according to the present invention, wherein the substrate holder 1 ″ has a hole 7 in the thermal conductor 2 ″. The hole 7 is for allowing the deformation element 8 of the substrate 11 (not shown), particularly the spikes, to access the backside 11o (not shown). Since this embodiment is consistent with the embodiment of FIG. 2 in other respects, the description of FIG. 2 is referred to.

FIG. 4 shows a fourth embodiment according to the present invention of the substrate holder 1'' according to the present invention, wherein the substrate holder 1'''' is the back side (not shown) of the first substrate 11 (not shown). In addition to the features described in FIG. 3, the position fixing surface 4o also has a recess 9 to minimize contact with (not shown). This minimization helps to avoid substrate contamination, especially metal contamination, by the position-fixed surface 4o. This minimization also helps to avoid local deformation of the substrate by the particles. The recess 9 can be filled with a fluid having high heat capacity and / or thermal conductivity to increase thermal coupling.

FIG. 5 shows a fifth embodiment of the present invention of the substrate holder 1 ^IV according to the present invention, wherein the substrate holder 1 minimizes contact with a back side (not shown) of the first substrate 11 (not shown). And / or having recesses 9 filled with protrusions and / or needles and / or columns 10 in addition to the features described in FIG. 4 to ensure near-total support of the first substrate 11. .. This minimization also helps to avoid contamination, especially metal contamination. The recess 9 can be filled with a fluid having high heat capacity and / or thermal conductivity to increase thermal coupling.

FIG. 6a shows a first step of an exemplary method according to the invention, in which the first upper substrate 11 is first spaced d1 from the second lower substrate 11'. positioned. This process step is performed in the region a already defined above in the corresponding Tt diagram. Both substrates 11 and 11'are brought close to each other, and the thermal effect of the lower second substrate 11'or the lower substrate holder 14 on the upper first substrate 11 has already been described above. It is eliminated to the maximum by the relatively large spacing.

In the subsequent step, both substrates 11 and 11'are brought close to each other up to the interval d2. At this point, the system is already located in the region b defined above, the so-called coarse approach region, where the first on the upper side, especially due to the heat radiation of the lower substrate 11'. The substrate 11 of the above is relatively slightly heated.

In the steps that follow, both substrates 11, 11'are further approached to each other up to the well-defined spacing d3 already described above. At this point, the system is located in the region c already defined above, the so-called close proximity region, where the abruptness of the upper first substrate 11 is particularly due to heat radiation and heat convection. Heating is carried out.

In the subsequent step of FIG. 6d, the bonding process of both substrates 11 and 11'is carried out. Both boards 11 and 11'are located at a constant interval d3. At this point, the substrates 11 and 11'are located in the region d already defined above, that is, in the so-called bonding region, in which the temperature T4o is constant over the period t1.

Subsequent steps in FIG. 6e perform cooling of the substrate 11 and / or 11'in the region e already defined above. The cooling itself is in the process of adapting the temperature of the upper first substrate 11 to the ambient temperature, especially the temperature of the ambient atmosphere and / or the temperature of the lower second substrate 11'or the lower substrate holder 14. be. However, at this point, the coupling of the two substrates 11, 11'has already been carried out, especially by prebonding.

It is omitted that the region f already defined above is illustrated by further drawings. Because you can't get important knowledge from here. As already disclosed in the description of the specification, it is also possible to carry out the bonding process in a constant temperature region in region f.

FIG. 7a shows the temperature and time already described above, having the six characteristic temperature regions a, b, c, d, e, f already defined above, shown on the upper horizontal axis. The diagram is shown. On the lower horizontal axis, the time t is shown in seconds, and on the left vertical axis, the temperature T is plotted in Kelvin. On the right vertical axis, the unscaled spacing d (a.u.) between both substrates 11 and 11'is plotted. In addition, four temperature graphs 12, 12', 12'', and 12''' are entered. The temperature graph 12 represents the temperature of the first substrate 11. The temperature graph 12'represents the temperature of the heat conductors 2, 2', 2'', 2''', 2 ^IV , which are more or less consistent with the temperature Tk of the cooling fluid. This temperature is almost the same as the temperature T1o of the upper substrate 11 before both the substrates 11 and 11'are brought close to each other. The temperature graph 12 ″ represents the temperature of the second substrate 11 ′. The temperature graph 12'''represents the temperature of the lower substrate holder 14. If the thermal coupling between the second substrate 11'and the lower substrate holder 14 is large enough, these two temperatures will be approximately the same.

Further, an interval graph 13 showing an interval d between both substrates 11 and 11'is also shown. The interval graph 13 should be construed exclusively as a symbol, and in practice negatively accelerates, i.e., brakes the substrate, so to show a relatively gentle transition from region c to region d. Become. In particular, the substrate can also change its speed during the approaching stage. The temperature difference ΔT between the temperature of the lower substrate and the temperature of the upper substrate in the temperature saturation region d is due to thermal resistance and / or by a heat source, especially by the heater in the lower sample holder 14. It can be adjusted accurately and reproducibly by the heat sink, especially the cooling fluid.

The transitions of the temperature graph 12 and the interval graph 13 during the implementation of the exemplary method according to the invention are as shown below: time at the start of the method, i.e., in the region labeled a (so-called temperature region a). On the far left of the scale, both substrates 11, 11'are brought closer to each other, thereby reducing the spacing d between the substrates 11, 11'. At the start of this method, the distance between the substrates 11 and 11'is d1, and this distance d1 is continuously reduced. In the temperature region a, the temperature of the first or upper substrate 11 is substantially constant at T1o.

The temperature region a is followed by a temperature region b in terms of time, and in this temperature region b, the temperature of the substrate 11 rises relatively slightly (temperature curve section T2o), while the substrates 11 and 11' The interval d between them is further reduced.

The temperature region b is followed by a temperature region c in terms of time, and in this temperature region c, the temperature of the substrate 11 increases relatively significantly compared to the temperature region b (temperature curve section T3o), while the substrate is on the other hand. The interval d between 11 and 11'is further reduced. At the end of the temperature region c, a substantially constant final spacing d is realized between the substrates 11 and 11'.

The temperature region c is followed by a temperature region d, in which the interval d remains constant and the temperature T4o of the first substrate 11 is substantially constant. The same applies to the temperature difference ΔT between the lower substrate 11'and the upper substrate 11. This constant temperature T4o is maintained for time t1. In particular, it should be pointed out that the transition from the temperature region c (so-called close proximity region c) to the temperature region d (so-called bonding region d) is rapidly carried out.

The temperature region d is followed by a temperature region e, in which the temperature of the substrate 11 drops (temperature curve section T5o), while the interval d remains substantially constant. In the temperature region f that follows, the temperature of the substrate 11 is substantially constant (see temperature curve section T6o).

FIG. 7b shows another temperature / time diagram with the six characteristic temperature regions a, b, c', d', e, f already defined above. The interval graph 13 is the same as the interval graph of FIG. 7a. Since the temperature graph 12 corresponds to the temperature graph of FIG. 7a in the temperature regions a, b, c, and f, the description of FIG. 7a is referred to for these regions. Differences from FIGS. 7a become apparent in the regions c'and d'when compared with the regions c and d of FIG. 7a. In this example, the transition from the close proximity region c'to the bonding region d'is not carried out abruptly as shown in FIG. 7a, but is carried out continuously and slowly.

FIG. 8 shows FIG. ~ VII. Shown are the plurality of overlay errors already described or defined above that may occur between the upper structure 15 of the upper substrate 11 and the lower structure 15'of the lower substrate 11'. At least some of them can be avoided using the present invention. Some of the overlay errors are known as run-out errors.

FIG. 8-I. The overlay error of is a mismatch of the overlay of the upper structure 15 and the lower structure 15', which is a typical result of the runout error. The structures 15, 15'are the same in shape, but do not match. The causes of this type of error are (i) the structures 15, 15'on the substrates 11, 11'are fundamentally inaccurate and / or (ii) before bonding, especially the substrate 11. , 11'distortion of the structure 15, 15'and / or (iii) distortion of the structure 15, 15'due to the distortion of the substrate 11, 11'during bonding. Yet another possibility is that both substrates 11, 11'are displaced from each other as a whole. However, in this case, it is caused by a basic alignment problem regarding the overall alignment of the two substrates with each other, and has little to do with the concept of runout.

FIG. 8-II. Shows yet another overlay error of the two structures 15 and 15'rotating with respect to each other. The rotation of both structures 15 and 15'with respect to each other is exaggerated and illustrated, and in reality only a few degrees, especially a few tenths of a degree, occur. Such rotation occurs when (i) both structures 15, 15'are not properly manufactured on both substrates 11, 11' and / or (ii) prior to the bonding process. When both structures 15, 15'are rotated against each other, especially locally, where there is a particularly local strain in the vicinity of, 15', and / or during the (iii) bonding process, the structure. This is the case when there is a particularly local strain in the vicinity of the bodies 15 and 15'and the corresponding structures 15 and 15' are rotated relative to each other, especially locally. Yet another possibility is that both substrates 11, 11'would twist together as a whole. In this case, 8-II. It should be seen that the overlay error of the form of is increasing radially from the inside to the outside, especially at multiple positions between the substrates 11, 11'.

Figure 8-III. -8-VII. Overlay errors are primarily due to (i) scaling errors caused by inaccurate manufacturing and / or (ii) scaling errors caused by distortion of structures 15, 15'before bonding, especially due to distortion of substrates 11, 11'. And / or (iii) scaling error caused by distortion of structures 15, 15'during bonding, especially due to distortion of substrates 11, 11'. These are typically not called runout errors.

FIG. 9 shows a schematic cross-sectional view of a non-scaled portion of the substrate holder according to the invention, which has the equivalent circuit diagram described above the thermal resistances Rth1 to Rth8. In particular, the thermal resistances Rth1 to Rth3 should be minimized as much as possible in order to be able to maximize heat conduction from the lower substrate holder 14 with the heating device (not shown) to the lower substrate 11'. Is. This enables efficient and rapid heating of the lower substrate 11'according to the present invention. Furthermore, with a series of minimum thermal resistances, a very rapid change in temperature T1u of the lower substrate 11'can be achieved.

The thermal resistance Rth4 should be maximum according to the present invention. In a purely theoretically ideal case where the thermal resistance Rth4 is infinite, the amount of heat does not reach the upper substrate 11 from the lower substrate 11'. Due to the finiteness of the thermal resistance Rth4, a small amount of heat that cannot be ignored always reaches the upper substrate 11 from the lower substrate 11'. The thermal resistance Rth4 can be adjusted relatively easily and accurately by selecting a vacuum or a special mixture between the substrates 11 and 11'.

According to the present invention, the thermal resistances Rth5 to Rth8 are also minimized so that the heat conduction between the cooling fluid, especially the atmosphere, and the upper substrate 11 can be maximized and thus as efficient as possible. Should be done. During the bonding process in the temperature saturation region d, the temperature difference ΔT between the upper temperature T4o or the temperature T4o of the upper substrate 11 and the temperature T1u of the lower substrate 11'is exactly as expected. Further and reproducible adjustment is crucial according to the present invention. This is, in particular, according to the invention, (i) selecting at least one of the thermal resistances Rth1 to Rth8 as desired, and / or (ii) particularly in the lower substrate holder 14. It is realized by adjusting the lower temperature T1u to Tp using a heating device and / or (iii) particularly by adjusting the upper temperature T1o to Tk using the cooling fluid according to the present invention.

1,1', 1'', 1''', 1 ^IV substrate holder 2,2', 2'', 2''', 2 ^IV thermal conductor 3 ribs 3o rib surface 4 position fixing part 4o position fixing surface 5 Position fixing element 6 Boundary surface 7 Hole 8 Deformation element 9 Recess / recess / dent 10 Protrusion / needle 11, 11'Board 12, 12', 12'', 12'''Temperature graph 13 Interval graph 14 Bottom Side board holder 15,15'Structure d1, d2, d3 Board spacing t1 Period T1o, T2o, T3o Temperature / temperature curve section T4o, T5o Temperature / temperature curve section Tp Board holder temperature Tw Thermal conductor temperature Tk Cooling Fluid temperature a, b, c, c', d, d', e, f temperature range

Claims (2)

In the method for bonding the first substrate (11) to the second substrate (11'),
In the first step, the substrate holder holding the first substrate (11) is thermally coupled to the ambient temperature, and the second substrate is heated by the heating device in the substrate holder holding the second substrate (11'). The temperature (T1u) of the substrate (11') is made higher than the temperature (T1o) of the first substrate (11), and the first and second substrates (11, 11') are brought close to each other. As a result, the temperature (T2o, T3o) of the first substrate (11) rises due to the heat radiation of the second substrate (11') .
In the second step, the approach between the first and second substrates (11, 11') is stopped, and the distance (d3) between the first and second substrates (11, 11') is set. Keep constant and adjust the thermal resistance (Rth4) of the interval (d3) by vacuum at the interval (d3) or by selecting the fluid at the interval (d3) when the interval (d3) is constant. However , the thermal conductor of the substrate holder holding the first substrate (11) causes the first substrate (11) to generate a constant temperature (T4o) for at least a predetermined period (t1). , The temperature difference (ΔT) between the temperature (T1u) of the second substrate (11') higher than the temperature (T4o) of the first substrate (11) and the temperature (T4o) of the first substrate (11). ) To be constant,
In the third step, both the first and second substrates (11, 11') are bonded to each other at least temporarily within the period (t1).
Method. The period (t1) in which the interval (d3) is constant and the constant temperature (T4o) is generated is made longer than 5 seconds.
The method according to claim 1.

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