JP7512761B2 - Substrate Bonding Equipment - Google Patents

Description

The present invention relates to a substrate bonding device.

Silicon carbide is a compound semiconductor material composed of silicon and carbon. Silicon carbide has a dielectric breakdown field strength ten times that of silicon, and a band gap three times that of silicon, making it an excellent semiconductor material. Furthermore, it is possible to control the p-type and n-type required for device fabrication over a wide range, and so it is expected to be a material for power devices that surpasses the limitations of silicon.

In addition, silicon carbide has the advantage that it can achieve high voltage resistance even with a thinner thickness, so by making it thinner, it is possible to obtain a semiconductor with low on-resistance and low loss.

However, compared to silicon semiconductors, which have been widely used up to now, it is difficult to obtain large-area silicon carbide single crystal substrates, and the manufacturing process is complicated. For these reasons, silicon carbide semiconductors are more difficult to mass-produce and more expensive than silicon semiconductors.

Various efforts have been made to reduce the cost of silicon carbide semiconductors. For example, Patent Document 1 describes a method for manufacturing a silicon carbide substrate, which includes at least preparing a silicon carbide single crystal substrate and a silicon carbide polycrystalline substrate having a micropipe density of 30 pieces/cm2 or ^less , performing a step of bonding (joining) the silicon carbide single crystal substrate and the silicon carbide polycrystalline substrate, and then performing a step of thinning the single crystal substrate to manufacture a substrate in which a single crystal layer is formed on the polycrystalline substrate.

Furthermore, Patent Document 1 describes a method for manufacturing a silicon carbide substrate in which a step of implanting hydrogen ions into the single crystal substrate to form a hydrogen ion implanted layer is performed before the step of bonding the single crystal substrate and the polycrystalline substrate, and after the step of bonding the single crystal substrate and the polycrystalline substrate, and before the step of thinning the single crystal substrate, a heat treatment is performed at a temperature of 350°C or less, and the step of thinning the single crystal substrate is a step of mechanically peeling it off at the hydrogen ion implanted layer.

This method makes it possible to produce many more bonded silicon carbide substrates from a single silicon carbide single crystal ingot.

JP 2009-117533 A

The method of manufacturing a silicon carbide wafer described in Patent Document 1 involves bonding a silicon carbide single crystal substrate, on which a thin ion-implanted layer has been formed by implanting hydrogen ions, to a silicon carbide polycrystalline substrate, and then heating and peeling the two together.

When bonding a band gap semiconductor substrate such as a silicon carbide single crystal substrate to a handle substrate such as a silicon carbide polycrystalline substrate, the substrates are bonded by a method called room temperature bonding. In general, argon (Ar) ions or neutral argon particles are first irradiated onto the bonding surfaces of each substrate in a high vacuum atmosphere to remove interface termination components such as oxygen, hydrogen, and hydroxyl groups (OH groups) present on the bonding surfaces of the substrates, activating the surfaces. The activated bonding surfaces are then brought into contact with each other to bond the substrates.

Conventionally, as mentioned above, surface activation processing has been performed by irradiating the substrate with argon ions or neutral argon particles. However, when irradiating the substrate with these particles, the particles have mass and attack the substrate surface, which in principle causes the sputtering phenomenon. For this reason, during irradiation, two problems can occur: (1) particles that are repelled by sputtering and ejected from the substrate or vacuum chamber aggregate to form particles, and particles that are ejected from the substrate or vacuum chamber adhere to the chamber walls and then peel off to form particles, resulting in the generation of particles; and (2) metal contamination of materials in the vacuum chamber.

Furthermore, if the generated particles become trapped between the bonding surfaces, voids may form at the bonding surface after bonding. It has also been confirmed that contamination by particles ejected from the substrates or vacuum chamber due to the sputtering phenomenon can cause defects as impurities in the bonded substrates. For these reasons, preventing these problems has been a major challenge.

Therefore, the present invention aims to provide a substrate bonding device capable of reducing voids and contamination in a bonded substrate manufacturing device that bonds a band gap semiconductor substrate and a handle substrate.

The substrate bonding apparatus of the present invention is a substrate bonding apparatus for manufacturing a bonded substrate by bonding a band gap semiconductor substrate and a handle substrate, and includes a bonding chamber for bonding the band gap semiconductor substrate and the handle substrate, a substrate holder provided in the bonding chamber and having a first holder for holding either the band gap semiconductor substrate or the handle substrate and a second holder for holding the other of the band gap semiconductor substrate or the handle substrate, an ultraviolet irradiation device for irradiating ultraviolet light onto at least one of the bonding surfaces of the band gap semiconductor substrate and the handle substrate held by the substrate holder, and a vacuum device for creating a vacuum inside the bonding chamber.

The substrate bonding apparatus of the present invention may further include a heater for heating the band gap semiconductor substrate and the handle substrate held by the substrate holder.

The substrate bonding device of the present invention may have a suction mechanism in which the substrate holder electrostatically suctions the band gap semiconductor substrate and the handle substrate.

The substrate bonding device of the present invention may further include at least one of a substrate holder driving means and an ultraviolet irradiation device driving means, in which the holding surface of the first holder and the holding surface of the second holder face each other in the substrate holder, and the ultraviolet irradiation device is disposed between the holding surface of the first holder and the holding surface of the second holder.

In the substrate bonding apparatus of the present invention, the vacuum device may have a turbomolecular pump provided near each of the first holder and the second holder.

The substrate bonding apparatus of the present invention may be configured such that the ultraviolet irradiation device has an irradiation source that irradiates ultraviolet light with a wavelength of 170 nm to 260 nm.

The substrate bonding device of the present invention may be such that the band gap semiconductor substrate is a single crystal substrate and the handle substrate is a polycrystalline substrate.

In the substrate bonding device of the present invention, the band gap semiconductor substrate and the handle substrate may both be silicon carbide substrates.

The substrate bonding device of the present invention can reduce voids and contamination in a bonded substrate produced by bonding a band gap semiconductor substrate and a handle substrate.

1 is a side view showing a schematic view of an interior of a bonding chamber of a substrate bonding apparatus according to an embodiment of the present invention; 2 is a plan view showing a schematic view of the inside of a bonding chamber of the substrate bonding apparatus shown in FIG. 1 . 2 is a side view showing a state in which substrates are held by a substrate holder in the substrate bonding apparatus shown in FIG. 1 ; 2 is a side view showing a state where the substrates held by the substrate holders are irradiated with ultraviolet light in the substrate bonding apparatus shown in FIG. 1 ; FIG. 2 is a side view showing a state in which substrates held by substrate holders are bonded in the substrate bonding apparatus shown in FIG. 1 ; FIG. 2 is a side view showing a schematic state after the substrates have been bonded in the substrate bonding apparatus shown in FIG. 1 ; FIG. 2 is a side view showing a schematic diagram of a state in which a bonded substrate is being transported in the substrate bonding apparatus shown in FIG. 1 . FIG. FIG. 2 is a side view that illustrates a schematic diagram of a modified example of the substrate bonding apparatus illustrated in FIG. 1 . FIG. 9A is a plan view that shows a bonded substrate in which voids have occurred, and FIG. 9B is a plan view that shows a method for cutting the bonded substrate into chips and evaluating them.

[Substrate bonding device]
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A substrate bonding apparatus according to an embodiment of the present invention will be described with reference to the drawings. However, the present invention is not limited to the following embodiment.

The substrate bonding apparatus of this embodiment can be applied to the manufacture of a bonded substrate W, in which a bandgap semiconductor substrate S and a handle substrate P are stacked together to obtain a bonded substrate W in which the bandgap semiconductor substrate S and the handle substrate P are stacked together.

In addition, when manufacturing a bonded substrate W using the substrate bonding apparatus of this embodiment, a single crystal substrate can be used as the band gap semiconductor substrate S, and a polycrystalline substrate can be used as the handle substrate P. In addition, this embodiment can be suitably applied to the case of manufacturing a bonded substrate W in which the band gap semiconductor substrate S and the handle substrate P are both silicon carbide (SiC) substrates, silicon (Si) substrates, or gallium nitride (GaN) substrates.

Specifically, for example, when obtaining a silicon carbide substrate as the bonded substrate W, a silicon carbide single crystal substrate can be used as the band gap semiconductor substrate S, and a silicon carbide polycrystalline substrate can be used as the handle substrate P.

The silicon carbide single crystal substrate used as the band gap semiconductor substrate S may be, for example, a 4H-SiC single crystal substrate obtained by processing a bulk single crystal of silicon carbide created by sublimation, or a 4H-SiC single crystal substrate obtained by epitaxial growth on a single crystal wafer by chemical vapor deposition. The silicon carbide single crystal substrate used as the band gap semiconductor substrate S may contain dopants such as nitrogen and aluminum.

The silicon carbide polycrystalline substrate used as the handle substrate P can be, for example, a 3C-SiC polycrystalline substrate obtained by forming a silicon carbide polycrystalline film by chemical vapor deposition.

The shape of the bandgap semiconductor substrate S and the handle substrate P can be, for example, a circular parallel plate shape. The thickness of the bandgap semiconductor substrate S and the handle substrate P is not particularly limited, and can be, for example, about 200 μm to 500 μm each.

The substrate bonding apparatus 100 of this embodiment includes a bonding chamber 10, a substrate holder 20, a heater 30, a transport robot 40, an ultraviolet irradiation device 50, a suction mechanism 60, a vacuum device 70, and a pressurizing means (not shown). As shown in FIG. 1, the substrate holder 20, the heater 30, the transport robot 40, the ultraviolet irradiation device 50, the suction mechanism 60, the vacuum device 70, and the pressurizing means are provided in the bonding chamber 10. In addition, each device in the bonding chamber 10 of the substrate bonding apparatus 100 is formed using stainless steel. In this embodiment, the direction of the arrow A in FIG. 1 is the vertical direction, and the band gap semiconductor substrate S and the handle substrate P are held facing each other vertically in the substrate bonding apparatus 100, but the direction of the arrow A is not limited to the vertical direction. For example, the direction of the arrow A may be the horizontal direction (left-right direction).

Figures 1 and 3 to 7 are side views that show the inside of the bonding chamber of the substrate bonding apparatus 100, and Figure 2 is a plan view that shows the inside of the bonding chamber of the substrate bonding apparatus 100 as seen from above. Also, in Figures 3 to 6, the first conveyor table 41, the second conveyor table 43, part of the first arm 42, part of the second arm 44, and the vacuum device 70 are not shown.

The bonding chamber 10 is where the band gap semiconductor substrate S and the handle substrate P are bonded.

The substrate holder 20 is provided inside the bonding chamber 10 and holds the bandgap semiconductor substrate S and the handle substrate P. The substrate holder 20 has a first holder 21 that holds either the bandgap semiconductor substrate S or the handle substrate P, and a second holder 22 that holds the other of the bandgap semiconductor substrate S or the handle substrate P. There is no particular limitation on which of the bandgap semiconductor substrate S or the handle substrate P is held by the first holder 21, but since it is more important to prevent dust and the like from adhering to the bandgap semiconductor substrate S, the following description will be given assuming that the first holder 21 holds the bandgap semiconductor substrate S.

The first holder 21 has a first holding part 211 that holds the band gap semiconductor substrate S, and a first arm 212 that is a moving means for moving the first holding part 211 along the arrow A in FIG. 1. The second holder 22 has a second holding part 221.

In addition, inside the first holding part 211 and the second holding part 221, there are provided an adsorption mechanism 60 for holding the band gap semiconductor substrate S and the handle substrate P, and a heater 30 for heating the held band gap semiconductor substrate S and the handle substrate P.

The first holding portion 211 and the second holding portion 221 are provided so that the holding surface 211a of the first holding portion 211 and the holding surface 221a of the second holding portion 221 face each other. This allows the substrate holder 20 to hold the band gap semiconductor substrate S and the handle substrate P so that the bonding surfaces S1 and P1 face each other.

The heater 30 heats the bandgap semiconductor substrate S and the handle substrate P held by the substrate holder 20. The heater 30 has a first heater 31 provided in the first holding portion 211 of the substrate holder 20, and a second heater 32 provided in the second holding portion 221. By providing the heater 30, the bandgap semiconductor substrate S and the handle substrate P can be heated in the process of bonding the bandgap semiconductor substrate S and the handle substrate P, thereby increasing the bonding strength.

The transport robot 40 transports the band gap semiconductor substrate S, the handle substrate P, and the bonded substrate W within the bonding chamber 10.

The transport robot 40 has a first transport table 41 that holds and transports the band gap semiconductor substrate S, a first arm 42 that moves the first transport table 41, a second transport table 43 that holds and transports the handle substrate P, a second arm 44 that moves the second transport table 43, and an arm shaft portion 45 that serves as an axis about which the first arm 42 and the second arm 44 rotate.

The first conveyor 41 and the second conveyor 43 are provided with an adsorption mechanism 60, which can adsorb and transport the band gap semiconductor substrate S, the handle substrate P, and the bonded substrate W to the adsorption surface 41a, which is the upper surface of the first conveyor 41, and the adsorption surface 43a, which is the lower surface of the second conveyor 43.

As shown in FIG. 2, the first arm 42 and the second arm 44 can rotate around the arm shaft 45. That is, the first arm 42 moves along the arrow B and can transport the band gap semiconductor substrate S and the bonded substrate W that are adsorbed and held on the first transport stage 41. The second arm 44 moves along the arrow C and can transport the handle substrate P that is adsorbed and held on the second transport stage 43.

The ultraviolet irradiation device 50 irradiates ultraviolet light onto the bonding surfaces S1, P1 of the band gap semiconductor substrate S and the handle substrate P held by the substrate holder 20. The ultraviolet irradiation device 50 may irradiate ultraviolet light onto at least one of the bonding surfaces S1, P1 of the band gap semiconductor substrate S and the handle substrate P held by the substrate holder 20, but in order to more reliably activate the bonding surfaces of the substrates, it is preferable that the ultraviolet irradiation device 50 is configured to irradiate ultraviolet light onto both the bonding surfaces S1, P1 of the band gap semiconductor substrate S and the handle substrate P held by the substrate holder 20, as in this embodiment.

The ultraviolet irradiation device 50 has a first irradiation device 51 that irradiates ultraviolet rays upward to irradiate the band gap semiconductor substrate S, a second irradiation device 52 that irradiates ultraviolet rays downward to irradiate the handle substrate P, and an arm 53 that moves the first irradiation device 51 and the second irradiation device 52 in the direction of arrow D in Figure 1. As shown in Figure 1, the first irradiation device 51 and the second irradiation device 52 are integrated vertically.

The first irradiation device 51 has a frame 511 that is open only upward, and an ultraviolet lamp 512 housed in the frame 511. The second irradiation device 52 has a frame 521 that is open only downward, and an ultraviolet lamp 522 housed in the frame 521. The frames 511 and 521 are configured so that ultraviolet light is not irradiated in any direction other than the open top and bottom directions. This allows ultraviolet light to be efficiently irradiated onto the substrate held by the substrate holder 20.

The ultraviolet lamps 512 and 522 can be irradiation sources that irradiate ultraviolet rays with wavelengths of 10 nm to 280 nm, and preferably use irradiation sources that irradiate ultraviolet rays with wavelengths of 170 nm to 260 nm, which are particularly easy to obtain. In this embodiment, as shown in Figures 1 and 2, the ultraviolet lamps 512 and 522 are each composed of five cylindrical Xe excimer lamps, and the five lamps are arranged in a line in the width direction. The ultraviolet irradiation source can be changed in various ways according to the desired ultraviolet wavelength, and is not limited to Xe excimer lamps (172 nm), and for example, low-pressure mercury lamps (254 nm, 185 nm) can be used.

The arm 53 (ultraviolet ray irradiation device driving means) is configured to be contractible in the direction of the arrow D in FIG. 1, so that the first irradiation device 51 and the second irradiation device 52 can be moved in the direction of the arrow D in FIG. 1 to insert the first irradiation device 51 and the second irradiation device 52 between the holding surface 211a of the first holding part 211 and the holding surface 221a of the second holding part 221. That is, the ultraviolet ray irradiation device 50 can position the first irradiation device 51 and the second irradiation device 52 between the bonding surfaces S1 and P1 of the band gap semiconductor substrate S and the handle substrate P held opposite to the substrate holder 20 by the arm 53 (ultraviolet ray irradiation device driving means). This also makes the ultraviolet ray irradiation direction of the first irradiation device 51 and the second irradiation device 52 perpendicular to the bonding surfaces S1 and P1.

Since the ultraviolet irradiation device 50 can be inserted between the bonding surfaces S1, P1 of the band gap semiconductor substrate S and the handle substrate P held opposite each other by the substrate holder 20, the ultraviolet irradiation direction of the first irradiation device 51 and the second irradiation device 52 can be perpendicular to the bonding surfaces S1, P1, and ultraviolet rays can be irradiated more uniformly over the entire bonding surfaces S1, P1 than when ultraviolet rays are irradiated from an oblique direction. By irradiating the bonding surfaces S1, P1 with ultraviolet rays evenly, the entire bonding surfaces S1, P1 can be activated more than when ultraviolet rays are irradiated from an oblique direction.

In this embodiment, the first irradiation device 51 and the second irradiation device 52 are moved by the arm 53 (ultraviolet irradiation device driving means) of the ultraviolet irradiation device 50, but the substrate bonding device may be provided with a substrate holder driving means, and the substrate holder may be moved so that the ultraviolet irradiation device is positioned between the substrates. Also, the substrate bonding device may be provided with both a substrate holder driving means and an ultraviolet irradiation device driving means, and the substrate holder and the ultraviolet irradiation device may be moved closer to each other so that the ultraviolet irradiation device is positioned between the substrates.

The suction mechanism 60 electrostatically suctions the band gap semiconductor substrate S and the handle substrate P, thereby holding the substrates. The suction mechanism 60 is provided on the first holding part 211 and the second holding part 221 of the substrate holder 20, and on the first transport table 41 and the second transport table 43 of the transport robot 40.

By providing an adsorption mechanism 60 that electrostatically adsorbs the substrate, the substrate can be held more securely and transported or joined.

The suction mechanism 60 may be provided only on the first holding unit 211 and the second conveyance table 43, which hold the substrate on the underside. In this embodiment, the suction mechanism 60 is also provided on the first conveyance table 41 and the second holding unit 221, so that the substrate can be held more reliably.

The vacuum device 70 creates a vacuum inside the bonding chamber 10. The vacuum device 70 also has turbomolecular pumps 71 and 72 provided near the first holder 21 and the second holder 22 of the substrate holder 20. That is, the turbomolecular pumps 71 and 72 are provided near the bandgap semiconductor substrate S and the handle substrate P, respectively, held by the substrate holder 20.

Here, for example, when manufacturing a bonded substrate W in which both the band gap semiconductor substrate S and the handle substrate P are silicon carbide substrates, a higher degree of vacuum may be required than when bonding silicon substrates or the like in the bonding chamber 10. Even in such a case, the vacuum device 70 has turbo molecular pumps 71, 72 provided near the first holder 21 and the second holder 22 of the substrate holder 20, so that the substrates can be activated and the surrounding area of the bonding site can be more reliably made into a high vacuum.

The pressurizing means applies pressure to the inside of the bonding chamber 10 to a predetermined pressure. The pressurizing method is not particularly limited, and for example, a hydraulic method can be used. The bandgap semiconductor substrate S held by the first holder 21 and the handle substrate P held by the second holder 22 can be bonded to each other by applying pressure while they are stacked together.

By using the substrate bonding apparatus of this embodiment, activation of the bonding surfaces S1, P1 of the band gap semiconductor substrate S and the handle substrate P, and bonding of the band gap semiconductor substrate S and the handle substrate P can be performed in one apparatus. In other words, the time from activation processing of the bonding surfaces S1, P1 to bonding can be shortened, and bonding can be performed while more reliably maintaining the activated state of the bonding surfaces S1, P1.

[Method of manufacturing bonded substrate]
Next, the operation of the substrate bonding apparatus and the method for manufacturing the bonded substrate will be described. The method for manufacturing the bonded substrate described below is one example of the method for manufacturing the bonded substrate using the substrate bonding apparatus 100 of the present embodiment, and various conditions can be changed within a range that does not cause problems.

In the method for manufacturing a bonded substrate using the substrate bonding apparatus of this embodiment, a bonded substrate W can be manufactured by performing an activation process in which the bonding surface S1 of the band gap semiconductor substrate S and the bonding surface P1 of the handle substrate P are activated by irradiating them with ultraviolet light in a vacuum, and a bonding process in which the bonding surface S1 of the band gap semiconductor substrate S and the bonding surface P1 of the handle substrate P are overlapped and bonded after the activation process.

In the activation treatment step, the wavelength of the ultraviolet light is preferably 10 nm to 280 nm, and the vacuum is preferably 1×10 ⁻⁴ Pa or less.

In other words, in the activation process, it is preferable not to irradiate particles having mass, such as Ar, as has been done in the past. Instead of irradiating particles having mass, the bonding surface S1 of the band gap semiconductor substrate S and the bonding surface P1 of the handle substrate P are activated by irradiating with ultraviolet light.

In addition, it is preferable to mirror-polish and clean the bonding surfaces S1 and P1 of the band gap semiconductor substrate S and the handle substrate P before subjecting them to the activation process.

(Activation Treatment Step)
Next, the activation treatment step will be described in detail.

The activation process is a process in which at least one of the bonding surface S1 of the band gap semiconductor substrate S and the bonding surface P1 of the handle substrate P is activated by irradiating them with ultraviolet light in a wavelength range of 10 nm to 280 nm, i.e., VUV (10 nm to 200 nm) to UV-C (200 to 280 nm), under vacuum.

Here, activation of the bonding surfaces S1 and P1 refers to removing interface termination components such as oxygen, hydrogen, and hydroxyl groups (OH groups) and oxide films present on the bonding surfaces S1 and P1 between the band gap semiconductor substrate S and the handle substrate P to form dangling bonds.

The wavelength of the ultraviolet light in the activation process can be 170 nm to 260 nm, which is within the range of 10 nm to 280 nm and is the range where lamps that serve as the irradiation source are easily available. If the wavelength of the ultraviolet light is longer than 260 nm, the amount of energy is small, and it may not be possible to provide sufficient energy to the bonding surfaces S1 and P1 to promote surface activation.

In the activation process, the activation process time for irradiating ultraviolet light may be any time that can provide sufficient energy to the bonding surfaces S1 and P1. Since the amount of energy is the product of the intensity of the ultraviolet light and the irradiation time, the time required for irradiation can be calculated from the intensity of the ultraviolet light to be irradiated. Specifically, when the intensity of the ultraviolet light to be irradiated is, for example, 5 mW/ ^cm2 , the time can be set to about 2 minutes or more.

In the activation process, the degree of vacuum can be set to 1×10 ⁻⁴ Pa (N/m ² ) or less, and more preferably, ultra-high vacuum (JIS Z 8126-1) of 1×10 ⁻⁶ Pa or less. If the degree of vacuum in the activation process is low, the amount of activity of the activated surfaces (bonding surfaces S1, P1) after irradiation with ultraviolet light may be low, and sufficient bonding strength may not be obtained in the bonding process.

The activation process using the substrate bonding device 100 of this embodiment is carried out according to the following procedure.

Prior to the activation process, the inside of the bonding chamber 10 is evacuated to a predetermined vacuum level (for example, 5×10 ⁻⁶ Pa) by the vacuum device 70, and the vacuum state is maintained.

First, the bandgap semiconductor substrate S and the handle substrate P are held by the substrate holder 20. First, the bandgap semiconductor substrate S is placed on the adsorption surface 41a on the upper surface of the first conveyor 41 and held by electrostatic adsorption, and the handle substrate P is held by electrostatic adsorption on the adsorption surface 43a on the lower surface of the second conveyor 43. At this time, the first conveyor 41 and the second conveyor 43 are in the position shown in FIG. 2 (initial state position).

Then, the first arm 42 is moved toward the substrate holder 20 along the direction of arrow B in FIG. 2, and the second arm 44 is moved toward the substrate holder 20 along the direction of arrow C in FIG. 2. As a result, the band gap semiconductor substrate S moves directly below the first holding portion 211 of the substrate holder 20, and the handle substrate P moves directly above the second holding portion 221 of the substrate holder 20.

Furthermore, the electrostatic adsorption of the adsorption mechanisms 60 of the first and second conveyance tables 41 and 43 is switched to the electrostatic adsorption of the adsorption mechanisms 60 of the first and second holding parts 211 and 221 of the substrate holder 20, so that the bandgap semiconductor substrate S is electrostatically adsorbed to the first holding part 211, and the handle substrate P is electrostatically adsorbed and held by the second holding part 221. At this time, the bonding surfaces S1 and P1 of the bandgap semiconductor substrate S and the handle substrate P face each other (FIG. 3). After that, the first and second conveyance tables 41 and 43 are moved in the opposite direction to the previous one to retreat to their initial positions.

Next, as shown in FIG. 4, the arm 53 of the ultraviolet irradiation device 50 is extended to move the first irradiation device 51 and the second irradiation device 52 along the direction of the arrow D1, and insert them between the bonding surfaces S1, P1 of the bandgap semiconductor substrate S and the handle substrate P held opposite to each other by the substrate holder 20. At this time, the bandgap semiconductor substrate S, the first irradiation device 51, the second irradiation device 52, and the handle substrate P are positioned vertically aligned in a straight line.

Furthermore, the ultraviolet lamps 512, 522 irradiate the bonding surface S1 of the band gap semiconductor substrate S and the bonding surface P1 of the handle substrate P with ultraviolet light at a predetermined intensity (e.g., 172 nm ultraviolet light at 10 mW/ ^cm2 ) for a predetermined time (e.g., 2 minutes) (FIG. 4). As a result, the bonding surfaces S1, P1 are activated, and the activation process is completed.

In the above explanation, an example is shown in which ultraviolet light is irradiated onto both the bonding surface S1 of the band gap semiconductor substrate S and the bonding surface P1 of the handle substrate P, but ultraviolet light may be irradiated onto at least one of the bonding surface S1 of the band gap semiconductor substrate S and the bonding surface P1 of the handle substrate P.

(Joining process)
Next, the joining step will be described.

The bonding process is a process in which, after the activation process, the bonding surface S1 of the band gap semiconductor substrate S and the bonding surface P1 of the handle substrate P are bonded to obtain a bonded substrate W. In the bonding process described below, the bonding surface S1 of the band gap semiconductor substrate S and the bonding surface P1 of the handle substrate P are surfaces that are irradiated with ultraviolet light in the activation process.

It is preferable to bond the band gap semiconductor substrate S and the handle substrate P while the bonding surfaces S1 and P1 are maintained in an activated state, and the time between the activation process and the bonding process is preferably within a few seconds to one minute.

The temperature of the bandgap semiconductor substrate S and the handle substrate during the bonding process can be, for example, about 200°C to 400°C, although the optimal conditions vary depending on the type and combination of the bandgap semiconductor substrate S and the handle substrate P.

If the temperature of the bandgap semiconductor substrate S and the handle substrate in the bonding process is too low, such as below 200°C, sufficient bonding strength between the bandgap semiconductor substrate S and the handle substrate P cannot be obtained, and the occurrence of voids may not be sufficiently reduced. If the temperature of the bandgap semiconductor substrate S and the handle substrate in the bonding process is too high, such as above 400°C, distortion may occur between the bandgap semiconductor substrate S and the handle substrate P, and one or both of the substrates may crack when cooled after the bonding process.

In addition, in the bonding process, the pressure applied to the band gap semiconductor substrate S and the handle substrate P using the pressure means can be 50 kgf to 500 kgf (0.49 kN to 4.90 kN).

The degree of vacuum in the bonding chamber 10 during the bonding process can be the same as that during the activation process.

The processing time for the bonding process is not particularly limited as long as the band gap semiconductor substrate S and the handle substrate P are sufficiently bonded, and can be, for example, 10 seconds to 5 minutes.

The bonding process using the substrate bonding device 100 of this embodiment is carried out according to the following procedure.

As shown in FIG. 5, the arm 53 of the ultraviolet irradiation device 50 is retracted, and the first irradiation device 51 and the second irradiation device 52 are moved along the direction of the arrow D1 to retract the ultraviolet irradiation device 50. Then, the first arm 212 of the substrate holder 20 is extended to move the band gap semiconductor substrate S held by the first holding portion 211 along the direction of the arrow A1 in FIG. 5 to a position where the bonding surfaces S1 and P1 come into contact and overlap.

Here, in the activation process, the band gap semiconductor substrate S, the first irradiation device 51, the second irradiation device 52, and the handle substrate P are aligned in a vertical line, so that the band gap semiconductor substrate S and the handle substrate P can be moved to overlap in the minimum time and distance required, shortening the time between the activation process and the bonding process, and preventing dust and the like from adhering to the activated bonding surfaces S1 and P1.

After the bandgap semiconductor substrate S is moved to a position where the bonding surfaces S1 and P1 come into contact and overlap, the bandgap semiconductor substrate S and the handle substrate P are further heated by the first heater 31 and the second heater 32. As the substrates are heated, the overlapped bandgap semiconductor substrate S and the handle substrate P are pressurized to a predetermined pressure (e.g., 100 kgf (0.98 kN)) inside the bonding chamber 10 by the pressurizing means and maintained for a predetermined time (e.g., 3 minutes), thereby bonding the bandgap semiconductor substrate S and the handle substrate P. This forms the bonded substrate W.

Next, the bonded substrate W is collected. After the electrostatic adsorption of the suction mechanism 60 of the second holding unit 221 is turned off and the bonded substrate W is held by the first holding unit 211 through electrostatic adsorption, the first arm 212 is retracted and the first holding unit 211 is returned to its initial position along the direction of the arrow A1 in FIG. 6, as shown in FIG. 6. Next, as shown in FIG. 7, the first arm 42 is moved toward the substrate holder 20 along the direction of the arrow B in FIG. 2 to move the first conveying table 41 to a position directly below the first holding unit 211 of the substrate holder 20. Then, the suction mechanism 60 of the first holding unit 211 is switched to the suction mechanism 60 of the first conveying table 41 to hold the bonded substrate W on the first conveying table 41. Finally, the first arm 42 is moved in the opposite direction to the previous one to return the first conveying table 41 to its initial position and collect the bonded substrate W. This completes the manufacturing of the bonded substrate W.

(Comparison with conventional bonded substrate manufacturing methods and manufacturing equipment)
In conventional methods and apparatus for manufacturing bonded substrates, in order to activate the bonding surfaces, argon (Ar) ions or neutral argon particles are irradiated onto the bonding surfaces of the respective substrates, thereby removing interface termination components such as oxygen, hydrogen, and hydroxyl groups (OH groups) present on the bonding surfaces of the substrates, thereby activating the surfaces.

However, irradiation with argon ions or argon particles is an attack by particles with mass, and in principle causes a sputtering phenomenon, which causes problems such as (1) the generation of particles derived from particles repelled by sputtering, and (2) the generation of metal contamination of materials in the vacuum chamber. In addition, the sputtering phenomenon on the bonding surfaces caused by particles with mass causes the bonding surfaces to become unevenly textured, which causes gaps (voids, for example, void V in bonded substrate 700 in FIG. 9(A)) on the bonding surfaces after bonding. In addition, contamination caused by particles that fly out of the substrate or vacuum chamber due to the sputtering phenomenon causes defects in the bonded substrate.

The voids that occur in the bonded substrate can be observed using an optical microscope or a laser microscope.

The inventors discovered that by activating the bonding surfaces between the band gap semiconductor substrate and the handle substrate by irradiating them with ultraviolet light, an activated bonding surface can be obtained without generating particles or metal contamination caused by sputtered particles such as argon particles.

The substrate bonding apparatus of this embodiment can activate the bonding surface S1 of the band gap semiconductor substrate S and the bonding surface P1 of the handle substrate P without using particles with mass such as argon, making it possible to obtain a bonded substrate W with reduced voids and contamination.

The present invention is not limited to the above-described embodiment, but includes other configurations that can achieve the object of the present invention, and also includes modifications of the above-described embodiment.

For example, the substrate bonding apparatus 100A shown in FIG. 8 has a different direction of movement of the first conveyance table 41 and the second conveyance table 43 from the substrate bonding apparatus 100 of the above-mentioned embodiment. That is, the transport robot 40A has a first conveyance table 41, a first arm 42A, a second conveyance table 43, a second arm 44A, and an arm support part 45A. In the modified example shown in FIG. 8, the first arm 42A expands and contracts in the direction of the arrow E, and the second arm expands and contracts in the direction of the arrow F, thereby moving the first conveyance table 41 and the second conveyance table 43. In this way, the method of moving the first conveyance table and the second conveyance table is not limited to the above-mentioned embodiment or this modified example, and any configuration may be used as long as it can move the substrate between the transport robot and the substrate holder.

In addition, in the above-described embodiment, an apparatus for processing band gap semiconductor substrates S and handle substrates P one by one has been described, but multiple substrates may be processed in a single manufacturing batch by using a substrate holder or a transport robot that handles multiple band gap semiconductor substrates S and handle substrates P.

Although the best configurations and methods for implementing the present invention have been disclosed above, the present invention is not limited thereto. That is, the present invention has been described mainly with respect to specific embodiments, but those skilled in the art can make various modifications to the above-described embodiments in terms of shape, material, quantity, and other detailed configurations without departing from the scope of the technical idea and purpose of the present invention. Therefore, the descriptions limiting the shapes, materials, etc. disclosed above are provided as examples to facilitate understanding of the present invention, and do not limit the present invention. Therefore, descriptions of the names of components that have some or all of the limitations on the shapes, materials, etc. removed are included in the present invention.

The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to these examples in any way.

In this example, a silicon carbide single crystal substrate was used as the band gap semiconductor substrate, and a silicon carbide polycrystalline substrate was used as the handle substrate to manufacture a silicon carbide bonded substrate in which a silicon carbide single crystal substrate and a silicon carbide polycrystalline substrate were bonded. In addition, the substrate bonding apparatus 100 of the above-described embodiment was used as the manufacturing apparatus. The substrate bonding apparatus 100 is equipped with Xe excimer lamps as the ultraviolet lamps 512 and 522.

[Example 1]
(Manufacture of silicon carbide bonded substrates)
The silicon carbide single crystal substrate used was a 4H-SiC single crystal substrate with a diameter of 4 inches produced by sublimation. The silicon carbide polycrystalline substrate used was a 3C-SiC polycrystalline substrate with a diameter of 4 inches obtained by depositing a silicon carbide polycrystalline film by chemical vapor deposition.

First, prior to the activation process, the bonding surfaces of the silicon carbide single crystal substrate and the silicon carbide polycrystalline substrate were mirror-polished and cleaned. Next, as an activation process, the mirror-polished and cleaned bonding surfaces of the silicon carbide single crystal substrate and the silicon carbide polycrystalline substrate were irradiated with ultraviolet light without irradiating with Ar ions or Ar particles.

That is, the silicon carbide single crystal substrate and the silicon carbide polycrystalline substrate were held by the substrate holder 20, and the inside of the bonding chamber 10 was made into an ultra-high vacuum atmosphere with a degree of vacuum of 5×10 ⁻⁶ Pa or less. Furthermore, the bonding surfaces of the silicon carbide single crystal substrate and the silicon carbide polycrystalline substrate were irradiated with ultraviolet light having a wavelength of 172 nm at an intensity of 10 mW/cm ² for 2 minutes by the Xe excimer lamps (ultraviolet lamps 512 and 522).

Next, a bonding process was carried out. The silicon carbide single crystal substrate and the silicon carbide polycrystalline substrate were stacked so that the activated bonding surfaces were in contact with each other, and the bonding chamber 10 was heated to 300°C under the same vacuum conditions as in the activation process. A pressure of 100 kgf (0.98 kN) was applied to the stack of silicon carbide single crystal substrate and silicon carbide polycrystalline substrate, and the substrate was held for 3 minutes. In this way, a bonded substrate of the silicon carbide single crystal substrate and the silicon carbide polycrystalline substrate was obtained. Furthermore, the temperature in the bonding chamber 10 was lowered to room temperature, and the pressure in the bonding chamber 10 was restored to atmospheric pressure, and the bonded substrate was removed and evaluated.

(Evaluation of Silicon Carbide Bonded Substrates)
The resulting bonded substrate was evaluated for the presence or absence of voids, the presence or absence of contamination, and the bonding strength.

To check for the presence or absence of voids, microscopic observation was performed using an optical microscope to check whether voids occurred in the resulting bonded substrate. If voids occurred in the bonded substrate, point-like voids V could be confirmed, as in the bonded substrate 700 shown in Figure 9.

The bonded substrate was also subjected to X-ray fluorescence analysis to check whether it contained impurities and to evaluate the presence or absence of contamination. The X-ray fluorescence analysis device used was a NANOHUNTER II (manufactured by Rigaku).

The bond strength was also evaluated by cutting the resulting bonded substrate into chips of 5 mm square and checking for the presence or absence of delamination between the silicon carbide single crystal substrate and the silicon carbide polycrystalline substrate. If there were 3 or fewer delaminations out of 270, the bond strength was deemed sufficient, and if there were more than 5 delaminations, the bond strength was deemed insufficient.

Even if the bonding strength of the bonding substrate is sufficient, if voids V occur in the bonding substrate as in the bonding substrate 800 shown in FIG. 9(B), a chip that does not contain voids V (e.g., chip 810 in FIG. 9(B)) is a good product, but a chip that contains voids V (e.g., chips 820, 830, 840 in FIG. 9(B)) can cause defects when used in a later process. Therefore, it can be evaluated that the more chips that contain voids V, the lower the yield.

As a result of evaluating the bonded substrate, no voids were found, and measurements of metal impurities showed that they were below the inspection limit, meaning no contamination was found. Furthermore, when the bonded substrate was cut into 270 5 mm square chips, no peeling was found, and the bonding strength was determined to be sufficient.

[Example 2]
In Example 2, a bonded substrate was manufactured and evaluated in the same manner as in Example 1, except that the Xe excimer lamp of the substrate bonding device 100 was irradiated from an oblique direction to the substrate. As a result of evaluating the obtained bonded substrate, no voids were found, and the metal impurities were below the inspection limit in the measurement, so no contamination was found. In addition, when the bonded substrate was cut into chips of 5 mm square, peeling was found only in one chip out of 270 chips. From the above, it was shown that the bonding strength was sufficient, but that the bonding strength could be further increased by irradiating the substrate with ultraviolet light in a perpendicular direction.

In Examples 1 and 2 using the substrate bonding apparatus 100, which is an exemplary embodiment of the present invention, it was shown that by irradiating the bonding surfaces of the band gap semiconductor substrate and the handle substrate with ultraviolet light without irradiating particles having mass such as Ar, the bonding surfaces are activated, and a bonded substrate with reduced voids and contamination can be obtained without generating particles or metal contamination due to sputtered particles such as argon particles.

100 Substrate bonding apparatus 10 Bonding chamber 20 Substrate holder 30 Heater 40 Transport robot 50 Ultraviolet ray irradiation device 53 Arm (ultraviolet ray irradiation device driving means)
60 Adsorption mechanism 70 Vacuum device 71, 72 Turbo molecular pump S Band gap semiconductor substrate S1 Bonding surface of band gap semiconductor substrate P Handle substrate P1 Bonding surface of handle substrate W Bonding substrate

Claims (8)

A substrate bonding apparatus for manufacturing a bonded substrate by bonding a band gap semiconductor substrate and a handle substrate, comprising:
a bonding chamber for bonding the band gap semiconductor substrate and the handle substrate therein;
a substrate holder provided inside the bonding chamber, the substrate holder including a first holder for holding one of the band gap semiconductor substrate and the handle substrate, and a second holder for holding the other of the band gap semiconductor substrate and the handle substrate;
an ultraviolet irradiation device that irradiates ultraviolet light onto at least one of the bonding surfaces of the band gap semiconductor substrate and the handle substrate held by the substrate holder;
a vacuum device for creating a vacuum in the bonding chamber ;
The ultraviolet irradiation device has a first irradiation device equipped with an ultraviolet lamp and a second irradiation device equipped with an ultraviolet lamp, and the ultraviolet irradiation device is disposed between a bonding surface of the band gap semiconductor substrate and a bonding surface of the handle substrate which are arranged opposite each other, and is a substrate bonding device that irradiates ultraviolet rays while the band gap semiconductor substrate, the first irradiation device, the second irradiation device, and the handle substrate are positioned in a straight line . The substrate bonding apparatus of claim 1, further comprising a heater for heating the band gap semiconductor substrate and the handle substrate held by the substrate holder. The substrate bonding device according to claim 1 or 2, wherein the substrate holder has an adsorption mechanism that electrostatically adsorbs the band gap semiconductor substrate and the handle substrate. In the substrate holder, a holding surface of the first holder and a holding surface of the second holder face each other,
A substrate bonding apparatus as described in any one of claims 1 to 3, further comprising at least one of a substrate holder driving means and an ultraviolet irradiation device driving means for positioning the ultraviolet irradiation device between a holding surface of the first holder and a holding surface of the second holder. The substrate bonding apparatus according to any one of claims 1 to 4, wherein the vacuum device has a turbomolecular pump provided near each of the first holder and the second holder. The substrate bonding device according to any one of claims 1 to 5, wherein the ultraviolet irradiation device has an irradiation source that irradiates ultraviolet light with a wavelength of 170 nm to 260 nm. The substrate bonding device according to any one of claims 1 to 6, wherein the band gap semiconductor substrate is a single crystal substrate and the handle substrate is a polycrystalline substrate. The substrate bonding device according to any one of claims 1 to 7, wherein the band gap semiconductor substrate and the handle substrate are both silicon carbide substrates.

Images