JP2022176179A - Manufacturing method of bonded substrate and manufacturing device for bonded substrate - Google Patents

Abstract

To provide a manufacturing method of a bonded substrate capable of consistently performing processing from smoothing work to super-low-damage surface activation, and a manufacturing device for the bonded substrate.SOLUTION: The present invention relates to a method for manufacturing a bonded substrate by bonding a first inorganic crystal material substrate 14 and a second inorganic crystal material substrate 13. The method includes: a smoothing processing step of using a GCIB device capable of changing an irradiation condition to make surface roughness of the first inorganic crystal material substrate 14 disposed in vacuum equal to or less than Ra several nm with which bonding is possible; a surface activating step of using the GCIB device to respectively activate in an inert gas atmosphere a bonding surface of the first inorganic crystal material substrate 14 after a super smoothing processing step and a bonding surface of the second inorganic crystal material substrate 13 in such a manner that a thickness of a damage layer formed on a bonding interface between the first inorganic crystal material substrate 14 and the second inorganic crystal material substrate 13 becomes equal to or less than 2 nm; and a bonding step of contacting and bonding the activated bonding surface of the first inorganic crystal material substrate 14 with the activated bonding surface of the second inorganic crystal material substrate 13.SELECTED DRAWING: Figure 1

Description

The present invention relates to a bonded substrate manufacturing method and a bonded substrate manufacturing apparatus.

2. Description of the Related Art In recent years, manufacturing a bonded substrate by bonding an inorganic crystal material substrate to an inorganic crystal material substrate of the same kind or a different kind as the inorganic crystal material substrate has been carried out in various industrial fields. In this specification, the term "inorganic crystal material substrate" refers to a wafer-like or chip-like substrate made of metals, semiconductors, ceramics, oxides, nitrides, carbides, silicides, and inorganic crystal materials containing them. It's about.

For example, silicon wafers can be bonded together to create three-dimensional semiconductor devices and MEMS sensor devices, and compound semiconductors and silicon semiconductors can be bonded to create multiple layers of different types of devices and multi-junction solar cells. In recent years, optical elements have been manufactured by bonding oxide crystal materials, and surface acoustic wave filters have been manufactured by bonding piezoelectric single crystal wafers.

Such bonding cannot be performed at high temperatures (e.g., 150° C. or higher) due to the heat resistance limitations of the elements and materials formed on the substrate, and heat treatment at high temperatures (post-annealing) is required after bonding. Can not do it.

In addition, in the case of bonding different types of substrates, since the coefficient of thermal expansion differs between the materials of the different types of substrates, thermal strain and thermal stress occur when bonding at high temperatures, making it impossible to bond or degrading the characteristics after bonding. There is also the problem of deterioration.

Because of the problems described above, a bonding method capable of bonding at a low temperature or room temperature of 150° C. or less is used for bonding an inorganic crystal material substrate and an inorganic crystal material substrate of the same or different type as the inorganic crystal material substrate. It's like One such bonding method is Surface Activated Bonding (SAB). In surface activated bonding, an ion beam is created by ionizing an inert gas such as argon, and by irradiating the surface of the material to be bonded with this ion beam or plasma, oxide films and contamination existing on the surface of the bonding material are removed. By removing the layer and activating the surface, bonding at low temperature/normal temperature is realized.

However, in surface activation bonding, the surfaces to be bonded must be brought into close contact at low and room temperature, so the activated surfaces to be bonded must be extremely flat. For example, super-smoothing with a surface roughness Ra (arithmetic mean surface roughness) of less than 1 nm is required.

In addition, since the surface is irradiated with ions, most crystalline inorganic materials inevitably form a damaged layer having a thickness of nearly 5 nm on the activated surface due to ion irradiation. This damaged layer can be directly observed as an aggregate of amorphous or fine crystal grains by observation with a transmission electron microscope.

For example, in silicon and compound semiconductors, an amorphous layer with a thickness of about 5 nm or more is formed, which reduces interfacial electrical conduction, and is known to have a problem that a solar cell does not reach theoretical power generation efficiency. In addition, it is also known that the piezoelectric single crystal also suffers damage to the crystal layer, leading to a decrease in piezoelectric characteristics.

On the other hand, in the field of high-speed communication represented by high-power electronic devices and 5G information communication, the heat dissipation of devices has become a major issue due to the increase in power consumption. In the same field, diamond, which has high thermal conductivity, is expected to be a good inorganic crystal substrate material for heat dissipation substrates. On the other hand, polycrystalline diamond films formed on substrates such as Si by Chemical Vapor Deposition (CVD) are expected to serve as substrates with high thermal conductivity, as substrates of about 4 inches to 6 inches have begun to be distributed in recent years. ing. In order to use this diamond substrate as a high thermal conductivity substrate, it is necessary to bond it to a power device made of a wide bandgap semiconductor or the like or a high frequency device such as a SAW filter. It is known that a grain damage layer is formed. Therefore, there arises a problem that the interfacial thermal resistance cannot be reduced to the theoretical value.

Since the damage layer described above reduces the heat conduction effect at the bonding interface, it is extremely important to reduce the thickness of the damage layer when diamond is used as the heat dissipation substrate. Especially for future power devices, heat dissipation technology is highly expected.

As described above, in manufacturing a bonded substrate using an inorganic crystal material substrate, 1) in order to bond at a low temperature and room temperature of 150° C. or less, the surface roughness Ra (arithmetic average surface roughness) must be 1 nm. 2) the damage layer on the activated bonding surface should be as thin as possible in order not to impair the properties of the bonding substrate.

However, in the case of a diamond substrate, which is an example of an inorganic crystal material substrate, the surface of the as-grown CVD diamond polycrystal has unevenness of several hundred nanometers, which is similar to GaN or LT/LN. It is not possible to bond wafer substrates that constitute a single device. Also, a single crystal substrate or a polycrystalline self-supporting substrate has surface roughness of several tens of nanometers or more, and cannot be bonded as it is.

In order to smoothen diamond, which is the hardest material, conventional polishing requires a long time (about 1000 hours). In addition, in polishing using conventional abrasive grains, it is not possible to stably polish to a level of roughness (for example, arithmetic mean surface roughness Ra of 1 nm or less) that allows room temperature bonding with a wafer substrate as described above. .

Compound semiconductors such as GaN substrates are not as hard as diamond, but they are chemically unstable depending on the direction of the crystal. There is Moreover, in the activation by ion irradiation, there is also a problem that N-deficient defects are introduced into the activated surface because Ga and N desorb from the surface at different velocities.

These defects and damages can be reduced by heating the bonded substrate to 300° C. or more by post-annealing after bonding. I can't.

Therefore, processing using a gas cluster ion beam (GCIB) (hereinafter referred to as GCIB) is conceivable. Processing by GCIB is a molecular process, and processing is performed with kinetic energy greater than the bonding energy between atoms of the material to be processed, so smoothing is possible regardless of the hardness of the material to be processed.

However, in the smoothing process by GCIB, the relationship between the machining speed and the roughness of the machined surface does not necessarily match, and often becomes contradictory. Even in the case of diamond, the ultimate roughness does not reach 1 nm in terms of arithmetic mean surface roughness Ra under the condition that the rough surface can be smoothed at high speed.

However, it is possible to etch 1 μm on the entire surface of a 4-inch (Φ4″) diamond substrate having a surface roughness of about Ra 150 nm with a GCIB irradiation of 100 μA/cm ² in about 108 minutes. However, it takes about 3.7 hours under ultra-smoothing conditions to achieve a surface roughness Ra of about 0.5 nm. is possible.

SUMMARY OF THE INVENTION An object of the present invention is to provide a bonding substrate manufacturing method and a bonding substrate manufacturing apparatus capable of consistently performing surface activation treatment with ultra-low damage from smoothing processing by using a gas cluster ion beam (GCIB) apparatus. That is.

TECHNICAL FIELD The present invention relates to a method of manufacturing a bonded substrate by bonding a first inorganic crystal material substrate and a second inorganic crystal material substrate of the same kind or a different kind as the first inorganic crystal material substrate. As used herein, the term "inorganic crystal material substrate" refers to a wafer-like or chip-like substrate made of metals, semiconductors, ceramics, oxides, nitrides, carbides, silicides, and inorganic crystal materials containing them. be.

The manufacturing method of the present invention uses a gas cluster ion beam (GCIB) device capable of changing irradiation conditions to measure the surface roughness of the first inorganic crystal material substrate placed in a vacuum at the Ra number that can be bonded. The thickness of the damage layer formed at the bonding interface between the first inorganic crystal material substrate and the second inorganic crystal material substrate in the smoothing treatment step to make the surface roughness to be 1 nm or less (for example, the arithmetic mean surface roughness Ra is 1 nm or less). The bonding surface of the first inorganic crystal material substrate and the bonding surface of the second inorganic crystal material substrate that have undergone the ultra-smoothing treatment step are each subjected to an inert gas atmosphere using a GCIB apparatus so that the thickness is 2 nm or less. and a bonding step of contacting and bonding the activated bonding surface of the first inorganic crystal material substrate and the activated bonding surface of the second inorganic crystal material substrate.

According to the present invention, it is possible to perform the smoothing treatment of the first inorganic crystal material substrate, the surface activation treatment of the first and second inorganic crystal material substrates, and the subsequent bonding in a manufacturing apparatus that consistently implements the present invention. Therefore, it is possible to streamline the manufacturing process and improve reliability.

In the smoothing treatment step, while monitoring the surface roughness of the first inorganic crystal material substrate placed in a vacuum, the rough surface of the first inorganic crystal material substrate having a surface roughness Ra of several 100 nm is removed based on the monitoring results. The surface roughness that can be bonded and the intensity of the scattered light on the optical monitor are correlated in advance by switching from the irradiation conditions for flattening processing to reduce it to about several tens of nanometers to the irradiation conditions for ultra-smoothing processing. The surface of the first inorganic crystal material substrate is ultra-smoothed based on the relationship between . In this way, the operation of switching from the irradiation conditions for the flattening treatment to the irradiation conditions for the ultra-smoothing treatment can be performed with high accuracy by monitoring, so that the surface roughness of the first inorganic crystal material substrate can be It is possible to ensure that the Ra several nanometers or less, which enables bonding, can be achieved.

The monitoring is based on the change in the ratio of the scattered light and the reflected light of the light irradiated from the light source arranged in the GCIB apparatus to the first inorganic crystal material substrate due to the surface roughness, and the electric signal corresponding to the surface roughness. , and the GCIB apparatus may switch the irradiation conditions by an electrical signal. In this way, automation becomes possible.

As for the second inorganic crystal material substrate, a method suitable for the second inorganic crystal material substrate is used in advance to reduce the surface roughness to Ra several nanometers or less, which enables bonding, and at least surface activation treatment is performed. and joining may be performed according to the present invention. That is, the second inorganic crystal material substrate is subjected to the same smoothing treatment process as that for the first inorganic crystal material substrate, so that the surface roughness is reduced to Ra several nanometers or less, which enables bonding. Alternatively, the surface roughness may be reduced to Ra several nanometers or less at which bonding is possible through a smoothing treatment step different from the smoothing treatment step for the first inorganic crystal material substrate.

The first inorganic crystal material substrate may be a wafer-like or chip-like substrate made of metal, semiconductor, ceramics, oxide, nitride, carbide, silicide, or an inorganic crystal material containing them. It may be a diamond substrate. More specifically, it may be a CVD diamond substrate having a diamond layer formed by chemical vapor deposition (CVD).

The present invention can also be specified as a manufacturing apparatus for manufacturing a bonded substrate by bonding a first inorganic crystal material substrate and a second inorganic crystal material substrate of the same kind or a different kind as the first inorganic crystal material substrate. can. The bonded substrate manufacturing apparatus of the present invention includes a gas cluster ion beam (GCIB) device capable of changing irradiation conditions, a monitoring device for monitoring the surface roughness of the first inorganic crystal material substrate placed in a vacuum, A bonding device for bonding a first ultra-smoothed inorganic crystal material substrate and a second inorganic crystal material substrate in vacuum, wherein the GCIB device is configured to bond the first inorganic crystal material substrate placed in vacuum. The thickness of the damage layer formed at the bonding interface between the first inorganic crystal material substrate and the second inorganic crystal material substrate is the thickness of the ultra-smoothing treatment step of reducing the surface roughness to Ra several nanometers or less that allows bonding. The bonding surface of the first inorganic crystal material substrate and the bonding surface of the second inorganic crystal material substrate, which have undergone the ultra-smoothing process, are each subjected to activation in an inert gas atmosphere using a GCIB apparatus so as to have a thickness of 2 nm or less. and a surface activation step of activating the surface.

1 is a schematic diagram (cross-sectional view) of a manufacturing apparatus for a bonded substrate according to the present embodiment; FIG. FIG. 3 is a schematic diagram for explaining the details of a GCIB apparatus that constitutes a part of the bonded substrate manufacturing apparatus; (a) is a schematic diagram of a porous Faraday cup device, and (b) is a schematic partial cross-sectional view of a Faraday cup main body. It is a schematic diagram used in order to demonstrate the principle of an optical surface-roughness monitoring apparatus. It is a simple graph which shows the relationship between the intensity|strength of scattered light and reflected light, and surface roughness. It is the graph which confirmed the relationship between the cluster size and the thickness of the damaged layer by simulation and experiment. Fig. 10 is a graph showing that the cluster size can be changed by the cluster resizing mechanism; FIG. 10 is a schematic diagram (cross-sectional view) of a bonded substrate manufacturing apparatus according to a second embodiment;

FIG. 1 is a schematic diagram (cross-sectional view) showing an embodiment of a bonded substrate manufacturing apparatus of the present invention for carrying out the method of the present invention. A bonded substrate manufacturing apparatus is roughly divided into a GCIB apparatus, a process chamber, an optical surface roughness monitoring apparatus, a bonding apparatus, and a load lock chamber.

The GCIB apparatus has a gas cluster chamber 1 that generates clusters, an ion chamber 2 that ionizes and accelerates these clusters (can remove monomer ions and insert a magnetic field for cluster size selection), and uses the ionized clusters as an electrostatic lens. It has a neutralization chamber 3 that converges and neutralizes with an Einzel lens 31 of . The gas cluster chamber 1 for generating this cluster has a cluster size changing mechanism 1C capable of changing the positional relationship between the nozzle 1A and the skimmer 1B in order to change the cluster size. It can be confirmed by the multi-hole Faraday cup device 25 in FIG. The GCIB apparatus is connected to turbo pumps 6A and 6B for exhausting the area and a gas introduction system GIS.

As will be described later, the first inorganic crystal material substrate 14 is irradiated with a gas cluster ion beam (hereinafter sometimes referred to as GCIB) using a GCIB apparatus to measure the surface roughness of the first inorganic crystal material substrate. is smoothed to the Ra number nm or less where bonding is possible. In this embodiment, the surface roughness that enables bonding is assumed to be 1 nm or less in terms of arithmetic mean surface roughness Ra.

The process chamber 5 has a mechanical scanning stage on which a first inorganic crystalline material substrate 14, which is a workpiece, is placed. In this embodiment, the first inorganic crystalline material substrate 14 is specifically a CVD diamond substrate having a diamond layer formed by chemical vapor deposition (CVD).

The optical surface roughness monitoring device 18 monitors the surface roughness of the diamond substrate.

The load lock chambers 8 and 10 are chambers that can be vacuum-isolated from the process chamber 5 . For example, when the first inorganic crystal material substrate 14 to be smoothed by the GCIB apparatus is set on the sample holder 16A transported by the transport mechanism 16 and introduced into the process chamber 5, the load lock chamber 10 is evacuated in advance. It is a chamber for pulling. A turbo pump 6</b>C is connected to the load lock chamber 8 , and a turbo pump 9 is connected to the load lock chamber 10 . The high vacuum bellows 11 and 12 can move back and forth while maintaining the vacuum.

The second inorganic crystal material substrate 13 is pre-ultra-smoothed so as to be bonded to the first inorganic crystal material substrate 14, that is, has a surface roughness Ra several nm or less (arithmetic mean surface roughness Ra 1 nm) that enables bonding. below) (which may be ultra-smoothed in this device). In this embodiment, the second inorganic crystal material substrate 13 is a GaN substrate. Immediately before bonding, the substrate is transported to the GCIB irradiation position of the GCIB device by the transportation mechanism 7, and the bonding surface is irradiated with GCIB of an inert gas (for example, Ar gas) using the GCIB device to perform surface activation treatment. The surface activation treatment removes deposits on the bonding surface and at the same time, surface atoms are excited and activated with ultra-low damage.

The first inorganic crystal material substrate 14 ultra-smoothed by the GCIB apparatus is treated with an inert gas (for example, Ar gas) GCIB using the GCIB apparatus, as is the case with the second inorganic crystal material substrate 13, if necessary. After the surface activation treatment by , it is held by the sample holder 16A and transported to a position facing the second inorganic crystal material substrate 13 under the same vacuum environment. Then, the first inorganic crystal material substrate 14 is press-contacted with the second inorganic crystal material substrate 13 previously transported by the transport mechanism 7 to the position shown in FIG. chemically bonded [SAB]).

The reason why the first inorganic crystal material substrate 14 is subjected to the surface activation treatment "if necessary" is that the GCIB irradiated at the end of the ultra-smoothing treatment is an inert gas (for example, Ar gas). ), the intention is that there is no need to perform the surface activation treatment as a separate step, and the intention is not that the surface activation treatment is unnecessary.

The bonded first inorganic crystal material substrate 14 and second inorganic crystal material substrate 13 are transported to the load lock chamber 10 by the sample holder 16A, or transported to the load lock chamber 8 by the transport mechanism 7, and then loaded and locked. After the chamber 8 and/or the load lock chamber 10 are vacuum-isolated from the process chamber 5, they are taken out of the apparatus.

FIG. 2 is a schematic diagram for explaining the details of the GCIB apparatus constituting part of the bonded substrate manufacturing apparatus, and FIG. 3 is a schematic diagram showing a porous Faraday cup apparatus 25 for confirming the cluster size. is. Each of the plurality of holes H formed in the Faraday cup main body 25A has a diameter of about Φ1 mm, and a plurality of small-diameter Faraday cups 25B are installed corresponding to the respective holes H, and the Faraday cup 25B has a beam diameter to be measured. is placed in an area where the half-value width of is sufficiently measurable. FIG. 4 is a schematic diagram showing the principle of the monitoring device, FIG. 5 is a simple graph showing the relationship between the intensity of scattered light and reflected light and surface roughness, and FIG. 10 is a graph showing the correlation between distance and cluster size;

As shown in FIG. 2, the GCIB apparatus includes a gas introduction system GIS, a cluster generating part (gas cluster chamber 1, nozzle 1A, and skimmer 1B), and ionizing, accelerating, and converging the cluster with an electrostatic lens. It has a neutralizing portion (ion chamber 2, neutralization chamber 3, extraction electrode 4, einzel lens 31, magnet 32, neutralizer 33) and is placed on sample folder 16A extending into process chamber 5. The first inorganic crystal material substrate 14 is irradiated with GCIB. The apparatus is also equipped with a mechanism (transport mechanism 34, high-vacuum bellows 35) capable of inserting a magnet 32 for removing monomer ions MI or sorting the cluster size into the cluster beam path. By installing the porous Faraday cup device 25 shown in FIG. 3, the irradiation position of the GCIB can be measured, and the size of the cluster obtained by changing the size of the gas cluster GC by the cluster size changing mechanism 1C can be known from that position. . Specifically, the smaller the cluster deflected by the magnet 32, the greater the bending. to judge. Other constituent members and the like are as specified in FIG.

In this embodiment, the GCIB apparatus is equipped with an optical surface roughness monitoring device 18 for performing the smoothing process. The optical surface roughness monitoring device 18 measures the surface roughness of the first inorganic crystal material substrate 14 according to the principle shown in FIG. In FIG. 4, the monitoring device 18 includes a light source 19 such as a semiconductor laser, polarizing plates 20 and 20', a hemispherical concave mirror 21, a reflected light photosensor 22, and a scattered light photosensor 23. The concave mirror 21 has a hole at its vertex through which the reflected light passes. GCIB is a gas cluster ion beam for processing, SL is scattered light, PL is polarized light passing through the polarizing plate 20, RL is reflected light, 20′ is a polarizing plate that matches the polarization direction of the incident light from the reflected light, and 11 is the same. It is the reflected light that has passed through the polarizing plate.

The laser light emitted from the light source 19 passes through the polarizing plate 20 and becomes polarized light PL, and the surface of the first inorganic crystal material substrate 14, which is the workpiece, is irradiated with the polarized light PL. The irradiation position matches the position where the GCIB is irradiated. When the surface roughness is large, the polarized light PL is scattered, part of which becomes scattered light SL, which is scattered from the surface to the surroundings, and part of which is reflected inside the concave mirror 21 with a hole and collected for use as scattered light. The light is received by the photosensor 23 . The reflected light RL passes through the hole of the concave mirror 21, passes through the polarizing plate 20', and the component in the polarization direction of the incident light enters the reflected light photosensor 22. FIG.

As the GCIB irradiation progresses and the surface roughness of the workpiece decreases, the scattered light SL decreases and the reflected light RL increases. This process is as shown in FIG.

The relationship between the surface roughness and the indicated values of the two photosensors (reflected light photosensor 22 and scattered light photosensor 23) is obtained in advance, and when the desired roughness is achieved, the irradiation conditions of the GCIB are exceeded. Switch to smoothing conditions. For the flattening process, reactive gases such as SF ₆ , NF ₃ and CF ₄ or Ar, Kr, Xe, etc. may be added to the above reactive gases, and the gas species can be selected according to irradiation conditions. Switching from the flattening process to the super-smoothing process is performed by changing irradiation parameters such as irradiation energy, irradiation current, cluster size, irradiation angle, and substrate temperature in addition to the above gas species. At this time, it is also possible to insert a magnetic field into the beam path of the GCIB to remove the monomer ions MI and confirm the cluster size with the multi-hole Faraday cup device 25 . If the change in the amount of light is sufficient, either one of the signals may be used, and if the change is insufficient, both may be calculated and used. Furthermore, in the same way, when an indication value indicating that an ultra-smooth state has been obtained, the ultra-smoothing treatment is completed, and if necessary, using a GCIB apparatus, an inert gas (eg, Ar gas) by GCIB After the surface activation treatment, as shown in FIG. 1, bonding to the inorganic material substrate is performed.

In this manner, in the present embodiment, by using the optical surface roughness monitoring device 18, the smoothing treatment process can be performed by reducing the rough surface of the substrate having a surface roughness Ra of several 100 nm to several tens of nm. It is carried out in two stages: processing and ultra-smooth processing to reduce Ra several nanometers or less, which enables bonding.

FIG. 6 shows a graph confirming the relationship between the cluster size and the thickness of the damaged layer through simulation and experiment. In the same figure, the damage layer was confirmed by simulation and experiment when the Si surface was irradiated with Ar clusters (irradiated at 5 KV) in various sizes, and in this case, the thickness of the damage layer can be sufficiently reduced to less than 1 nm. ing.

FIG. 7 also shows that the cluster size can be changed by the cluster size changing mechanism 1C shown in FIG. From the figure, it can be seen that by changing the distance between the nozzle 1A and the skimmer 1B by about 5 mm, the peak position of the cluster size can be changed from about 1000 to about 5000.

FIG. 8 is a schematic diagram (sectional view) of a bonded substrate manufacturing apparatus, showing a second embodiment of the present invention. The bonding substrate manufacturing apparatus is composed of a GCIB apparatus chamber 100 , a pretreatment chamber 101 and a bonding chamber 102 . The pretreatment chamber 101 and the bonding chamber 102 each have an exhaust system and are separated by gate valves to independently control the pressure in each chamber. The bonding chamber maintains an ultra-high vacuum of 10 −7 to 10 −8 Pa, and the pretreatment chamber 101 is also evacuated to the same pressure as the bonding chamber 102 when the gate valve is opened. Substrates are carried in and out between the pretreatment chamber 101 and the bonding chamber 102 by a transport mechanism (not shown).

The pretreatment chamber 101 includes a GCIB device, an XY stage 103 that holds a substrate, and a monitoring device 18 that monitors surface roughness. By driving the substrate in the XY directions with the XY stage 103, the GCIB can be scanned on the substrate. By using the XYZ stage 103, the irradiation conditions may be adjusted by varying the relative distance between the GCIB apparatus and the substrate. Also, by providing an angle varying mechanism for the substrate stage, the incident angle of the GCIB with respect to the normal to the substrate may be optimized.

The bonding chamber 102 receives substrates to be bonded from the pretreatment chamber 101 and holds the substrates to be bonded on upper and lower bonding stages 106 and 106'. After aligning the substrates, the elevating devices 105 and 105' are driven to move the upper and lower bonding stages 106 and 106' relative to each other so that the substrates to be bonded are brought closer to each other and brought into contact with each other. The substrate to be bonded is pressurized for a predetermined time by the control device. The pressing force and time may be set according to the substrate to be bonded. Heaters may be provided on the upper and lower bonding stages to control the temperature of the bonding surfaces.

The pretreatment chamber 101 performs planarization processing, ultra-smoothing processing, surface activation processing, and film formation processing on substrates before bonding. Flattening processing and ultra-smoothing processing may be collectively performed as smoothing processing. The planarization process is a process of planarizing a substrate having an uneven structure until the surface roughness Ra is several tens of nm or less. A GCIB apparatus is used to irradiate the substrate surface with GCIB to remove a portion of the substrate material and perform planarization. In this embodiment, a reactive gas such as SF ₆ , CF ₄ , NF ₃ or CHF ₃ is used for flattening to achieve high speed processing. However, inert gases such as Ar and _N2 may be used, and _O2 , _N2O , _C2F6 , _C3F8 , _{C4F6 , SiF4} , _COF2 , _Kr , _Xe , etc. Including, the gas species may be appropriately selected according to the irradiation conditions. If the surface roughness Ra of the bonding target substrate is several tens of nanometers or less, the planarization processing may be omitted.

The ultra-smoothing process is a process for smoothing the surface roughness Ra of the bonding target substrate to 1 nm or less. The same GCIB apparatus is used for planarization processing, but the planarization processing is characterized by changing the GCIB irradiation conditions. During the planarization process, the monitoring device 18 measures in-situ the surface roughness of the substrate during the planarization process. When the surface roughness satisfies a predetermined value, the control mechanism changes the GCIB irradiation conditions. In this embodiment, the magnet for removing monomer ions is made to protrude into the beam path of the GCIB at the timing of switching from the flattening process to the ultra-smoothing process. By retracting the magnet for removing monomer ions during the planarization process, the processing current can be increased and the etching processing rate can be increased. By protruding the monomer ion removing magnet during the ultra-smoothing process, the monomer ions that cause damage to the substrate surface can be reliably removed.

The surface activation treatment is treatment for activating the bonding surfaces of the substrates to be bonded. The surface activation process also uses the same GCIB equipment for planarization and ultra-smoothing. During ultra-smoothing, the monitoring device 18 also measures in-situ the surface roughness of the substrate being processed. Since the amount of change in surface roughness during ultra-smoothing is very small, the monitoring device 18 is equipped with a highly accurate optical system and is capable of detecting the amount of change in surface roughness in sub-Angstrom units. When the surface roughness satisfies a predetermined value, the control mechanism changes the GCIB irradiation conditions. In the present embodiment, the gas type is changed from the reactive gas to the inert gas at the timing of switching from ultra-smooth processing to surface activation processing. Fluorine-based reactive gases have a high etching rate and are suitable for flattening and ultra-smooth processing, but they remain on the bonding surface. It also activates.

The film formation process is a process of depositing a material suitable for bonding on the bonding surfaces of the substrates to be bonded. Materials for film formation include metals such as Si, Fe, Ti, Al, and Cu, oxides, and nitrides. The same GCIB apparatus is used for the film forming process for flattening process, ultra-smoothing process, and surface activation process, and switching from etching to deposition is performed by changing the gas type and acceleration voltage. The film formation process may be performed before the bonding process. After super-smoothing and film formation, surface activation may be performed before bonding, or surface activation may be performed after ultra-smooth processing, followed by film formation and then bonding. good too. If the substrate surface is inactivated by the film forming process, the surface activation process should be performed after the ultra-smoothing process, then after the film forming process, the surface activation process should be further performed, and then the bonding process should be performed. By performing the surface activation process before the film forming process, there is also an effect that the material is easily deposited during the film forming process. Furthermore, when a difficult-to-process material is used as the film-forming material, the film-forming process may be performed before the flattening process or ultra-smoothing process.
In this embodiment, a single GCIB apparatus can perform planarization processing, ultra-smoothing processing, surface activation processing, and film formation processing, which contributes to simplification of the device configuration and cost reduction. . Further, flattening processing, ultra-smoothing processing, and surface activation processing also contribute to cleaning the substrate surface.

In this embodiment, the pretreatment chamber 101 is one chamber, but a plurality of pretreatment chambers may be provided. For example, planarization processing may be performed in the first pretreatment chamber, and ultra-smoothing processing, surface activation processing, and film formation processing may be performed in the second pretreatment chamber. If a reactive gas is used in the first pretreatment chamber and an inert gas is used in the second pretreatment chamber, it is possible to prevent the reactive gas from being brought into the bonding chamber and prevent contamination of the bonding chamber.

The switching of GCIB irradiation conditions may be determined according to the type of substrate and required specifications. Parameters for switching irradiation conditions include gas species, gas flow rate, current, cluster size, irradiation energy, incident angle, substrate temperature, and the like.

In the present embodiment, the monitoring device 18 is used to switch the GCIB irradiation conditions, but the conditions may be set in advance and the GCIB irradiation conditions may be switched by time control.

By using GCIB in ultra-smoothing and surface activation treatment, it is possible to obtain an activated surface with less damage and less distortion than when a monatomic ion beam is used.

Although diamond is used for the bonding substrate in this embodiment, the type of substrate is not limited to this. This device may be used to bond piezoelectric single crystals such as LiNbO ₃ and LiTaO ₃ to acoustic layers such as sapphire and SiOx, and other inorganic materials.

1 gas cluster chamber 2 ion chamber 3 neutralization chamber 5 process chamber 6A, 6B, 6C, 9 turbo pump 7 transfer mechanism 8, 10 load lock chamber 11, 12 bellows for high vacuum 13 second inorganic crystal material substrate 14 first Inorganic crystal material substrate 16 transport mechanism 16A sample holder 17 pressure contact mechanism 18 monitoring device

Claims (7)

A method of manufacturing a bonded substrate by bonding a first inorganic crystal material substrate and a second inorganic crystal material substrate of the same type or different type as the first inorganic crystal material substrate, comprising:
Using a gas cluster ion beam (GCIB) device capable of changing irradiation conditions, the surface roughness of the first inorganic crystal material substrate placed in a vacuum is made ultra-smooth to Ra several nanometers or less for bonding. a chemical treatment step;
The first inorganic crystal material substrate that has undergone the ultra-smoothing treatment step is adjusted so that the damage layer formed at the bonding interface between the first inorganic crystal material substrate and the second inorganic crystal material substrate has a thickness of 2 nm or less. a surface activation step of activating the bonding surface of the crystal material substrate and the bonding surface of the second inorganic crystal material substrate in an inert gas atmosphere using the GCIB apparatus;
and a bonding step of contacting and bonding the activated bonding surface of the first inorganic crystal material substrate and the activated bonding surface of the second inorganic crystal material substrate. Substrate manufacturing method. In the ultra-smoothing treatment step, while monitoring the surface roughness of the first inorganic crystal material substrate placed in a vacuum, the surface roughness Ra of the first inorganic crystal material substrate is 100 nm based on the monitoring results. From the irradiation conditions for flattening processing that reduces the rough surface of the surface to about several tens of nanometers, the surface roughness that can be bonded and the optical monitor are determined by switching to the irradiation conditions for ultra-smoothing processing. 2. The method of manufacturing a bonded substrate according to claim 1, wherein the surface of said first inorganic crystal material substrate is ultra-smoothed based on the relationship with the intensity of scattered light. The monitoring is based on the fact that the ratio of the scattered light and the reflected light of the light irradiated to the first inorganic crystal material substrate from the light source arranged in the GCIB apparatus changes depending on the surface roughness. Conducted using a monitoring device that outputs an electrical signal corresponding to
3. The method of manufacturing a bonded substrate according to claim 2, wherein said GCIB device switches said irradiation conditions according to said electric signal. The second inorganic crystal material substrate is subjected to the same smoothing treatment step as the smoothing treatment step for the first inorganic crystal material substrate, and the surface roughness thereof is reduced to Ra several nanometers or less, which enables bonding. Item 2. A method for manufacturing a bonded substrate according to item 1. The second inorganic crystal material substrate undergoes a smoothing treatment step different from the smoothing treatment step for the first inorganic crystal material substrate, and the surface roughness of the second inorganic crystal material substrate is reduced to Ra several nm or less, which enables bonding. The method for manufacturing a bonded substrate according to claim 1. 2. The method for manufacturing a bonded substrate according to claim 1, wherein said first inorganic crystal material substrate is a diamond substrate. A manufacturing apparatus for manufacturing a bonded substrate by bonding a first inorganic crystal material substrate and a second inorganic crystal material substrate of the same type or different type as the first inorganic crystal material substrate,
a gas cluster ion beam (GCIB) device capable of changing irradiation conditions;
a monitoring device for monitoring the surface roughness of the first inorganic crystal material substrate placed in a vacuum;
a bonding device for bonding the ultra-smoothed first inorganic crystal material substrate and the second inorganic crystal material substrate in the vacuum,
The GCIB apparatus includes a smoothing treatment step of reducing the surface roughness of the first inorganic crystal material substrate placed in a vacuum to several nanometers or less of Ra, which enables bonding, and The joining surface of the first inorganic crystal material substrate that has undergone the ultra-smoothing treatment step and the first and a surface activation step of activating the bonding surfaces of the inorganic crystal material substrates in an inert gas atmosphere using the GCIB apparatus according to 2 above. .

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