JP2006258958A - Method and device for bonding substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a device and a method for bonding substrates that bonds the substrates in a short bonding time with high bonding strength. <P>SOLUTION: The substrate bonding method includes a 1st process of washing a 1st main surface of a 1st substrate and a 1st main surface of a 2nd substrate; a 2nd process of coating at least one of the main surfaces of the 1st and 2nd substrates with resin containing silicon; a 3rd process of irradiating the resin with plasma; and a 4th process of putting the 1st main surface of opposing the 1st substrate and the 1st main surface of the 2nd substrate to each other and bonding the 1st and 2nd substrates together by compression. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a substrate bonding method and a substrate bonding apparatus, and more specifically to a substrate bonding method and a substrate bonding apparatus for bonding two substrates.

  If two substrates such as glass and silicon wafer can be bonded together at low temperature, various new devices including biochips and microchannels can be realized. Conventionally, as a method for bonding substrates, there are known a fusion bonding method, a pressure bonding bonding using a diluted hydrofluoric acid, and the like.

  However, the above-described fusing method has a problem that it is necessary to heat to a high temperature, and it takes a long time to bond the substrates, and it is difficult to adjust the temperature of the furnace. In addition, bubbles are likely to be generated at the bonding interface between the two substrates, and there is a problem of poor bonding in which the bonding strength is reduced. Even in the crimping bonding, there is a problem that it takes a long time to bond the substrates.

  On the other hand, a method is disclosed in which when two substrates in a liquid crystal display device or the like are bonded to each other with a predetermined gap, plasma treatment is performed on the substrate surface as a pretreatment for adhesion, and the surface is modified and then adhered. (For example, refer to Patent Document 1). In the method disclosed in Patent Document 1, after the surface of the substrate is modified, a sealing material is applied and adhesion is performed.

However, this method does not perform plasma treatment on the sealing material, but modifies the surface of the substrate itself, so that the element formed on the back surface of the substrate is susceptible to plasma.
Japanese Patent Laid-Open No. 2002-229044

  The present invention provides a substrate bonding method and a substrate bonding apparatus for bonding two or more substrates at low temperature with high bonding strength and short bonding time.

According to one aspect of the invention,
A first step of cleaning each of the first main surface of the first substrate and the first main surface of the second substrate;
A second step of applying a resin containing silicon to at least one of the first main surface and the second main surface;
A third step of irradiating the resin with plasma;
A fourth step of pressure-bonding the first and second substrates with the first main surface of the first substrate facing the first main surface of the second substrate;
A substrate bonding method is provided.

According to another aspect of the invention,
A cleaning unit for cleaning the substrate;
An application unit for applying a resin to the main surface of the substrate;
A plasma processing unit for irradiating the main surface of the substrate coated with the resin with plasma;
A bonding unit for crimping the substrate;
A substrate bonding apparatus is provided.

  According to the present invention, it is possible to provide a substrate bonding method and a substrate bonding apparatus that can efficiently bond two or more substrates with a strong bonding force.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a flowchart showing a main part of a substrate bonding method according to an embodiment of the present invention. FIG. 2 is a process cross-sectional view illustrating the main part of the substrate bonding method according to the present embodiment. Steps S1 to S4 in FIG. 1 correspond to the process cross-sectional views of FIGS. 2A to 2D, respectively.

  First, as step S1, the substrate 10 is cleaned. As the substrate 10, in addition to a glass substrate made of quartz, soda glass, or the like, a silicon (Si) wafer, various other semiconductors, dielectrics, insulators, or the like can also be used. Further, according to the present invention, the substrates are not limited to the same substrates, and different substrates can be bonded. For example, it is possible to bond a glass substrate and a silicon wafer, or bond a wafer made of a compound semiconductor such as InP and a silicon wafer.

Examples of the substrate cleaning method include SPM cleaning (sulfuric acid hydrogen peroxide cleaning). SPM cleaning is a method of boiling cleaning in a boiled H ₂ SO ₄ : H ₂ O ₂ = 3: 1 solution. Thereafter, the substrate is washed in the order of warm water rinsing, DHF (Diluted Hydrofluoric acid) 5%, and pure rinsing.

  Next, as step S <b> 2, a resin containing silicon is applied on the substrate 10. As such a resin, for example, porous MSQ (MSQ: Methyl Silsesquioxane) can be used. Specifically, for example, after applying MSQ having a thickness of about 100 nanometers by spin coating, baking is performed at 250 degrees Celsius for 1 minute, and then curing is performed at 400 degrees Celsius for about 30 minutes. In this way, a porous MSQ film 11 can be formed on the substrate 10. In addition, HSQ (Hydrogen Silsesquioxane) etc. can also be used instead of MSQ.

  Next, plasma processing is performed as step S3. Specifically, for example, radical-rich oxygen plasma is generated with an oxygen flow rate of several hundred sccm, a pressure of 100 Pa, and input power of several hundred watts, and the surface of the porous MSQ film 11 is irradiated. At this time, the substrate temperature is maintained at about 250 degrees Celsius.

Subsequently, in step S4, the two substrates 10 (W1, W2) on which the MSQ film 11 is thus formed are stacked in a direction in which the respective MSQ films 11 face each other, and are subjected to pressure bonding. Specifically, for example, the bonding is performed in a vacuum of 10 ⁻⁴ to 10 ⁻⁵ Pa by pressing with a pressing force of 1.5 MPa and a pressing time of 1 hour. The atmosphere is not limited to a vacuum but may be a reduced pressure atmosphere. However, when exposed to the atmosphere, impurities such as carbon in the atmosphere will adhere, so it is not desirable to expose to the atmosphere. Further, the substrate temperature at the time of bonding may be heated to about 400 degrees Celsius, or may be performed at room temperature.

FIG. 3 is a schematic cross-sectional view showing the bonded substrate bonded in this way. An MSQ film 11 is interposed between the two substrates 10 and 10 and is firmly bonded. Further, according to the present embodiment, since the two substrates are bonded through the MSQ film 11 as described above, it is not always necessary to mirror-treat the surface of the substrate 10 as in the conventional bonding (bonding) method. Absent. That is, even if the surface of the substrate 10 has some unevenness, it can be flattened by the MSQ film 11 and stably adhered. For example, even if the surface of the substrate 10 has unevenness of several nanometers or more, it can be planarized by the MSQ film 11. As a result, a polishing process such as CMP (chemical mechanical polishing) and a mirror finishing process are not required, and two substrates can be easily bonded in a wide range of applications.
Further, according to the present embodiment, it is possible to stack three or more substrates and bond them to each other. As a result, a device having a complicated structure can be easily realized, and various new functions can be expected.

FIG. 4 is a schematic cross-sectional view illustrating the reaction mechanism in the main part of the substrate bonding method according to this embodiment. That is, the reaction mechanism in the MSQ film 11 when the surface of the porous MSQ film 11 is irradiated with oxygen plasma 12 is shown. As shown in FIG. 4A, when the plasma treatment is performed, the oxygen plasma 12 is released on the surface of the MSQ film 11a (11) containing the methyl group (CH ₃ ) 14 formed on the substrate 10. Oxygen radicals 13 come in. Then, as shown in FIG. 4B, the methyl group (CH ₃ ) 14 activated by the oxygen radical 13 is decomposed and replaced with oxygen. That is, the methyl group is desorbed as CO _X or H ₂ (reference numeral 15 in the figure) by the action of the oxygen radicals 13, and is modified into the MSQ film 11b (11) mainly composed of Si—OH bonds. The As a result, the methyl group (CH ₃ ) in the MSQ film 11 is substituted to form a silanol group (Si—OH).

FIG. 5A is a graph showing a change in peak intensity with time obtained by FTIR (Fourier Transform Infrared Spectroscopy). That is, the horizontal axis in the figure is the time when the porous MSQ film 11 is irradiated with oxygen plasma, and the vertical axis is the peak intensity of each of Si—OH, Si—CH ₃ , and C—H bonds measured by FTIR. is there.
As can be seen from FIG. 5 (a), when the oxygen plasma is irradiated, the peak intensities of Si—CH ₃ and C—H bonds are attenuated, whereas new Si—OH bonds are generated, and the peaks are reduced. Strength increases. That is, it can be seen that the methyl group contained in the MSQ film 11 is almost lost and a silanol group (Si—OH) is generated.

  FIG. 5B is a graph showing the change over time of the thickness of the porous MSQ film. In the figure, the horizontal axis represents the time for which the MSQ film 11 was irradiated with oxygen plasma, and the vertical axis represents the amount of decrease in the thickness of the MSQ film 11. As can be seen from the figure, when the oxygen plasma is irradiated, the thickness of the MSQ film 11 decreases. It is recognized that the amount of decrease in film thickness tends to be larger for a porous MSQ film.

In addition, the wettability of the film tends to increase due to the chemical reaction such as the generation of silanol groups (Si—OH), the decomposition of methyl groups (CH ₃ ), and the generation of CO _X and H _2. Is recognized.

As described above, in the substrate bonding method according to this embodiment, as a pretreatment for substrate bonding, the porous MSQ film formed on the surface of the substrate is irradiated with oxygen plasma to modify the MSQ film. That is, by irradiating the MSQ film with oxygen plasma and modifying the MSQ film, the methyl group (CH ₃ ) in the MSQ film is substituted to generate a silanol group (Si—OH). As a result, the wettability increases and the adhesion strength increases. That is, two substrates can be bonded with a strong bonding strength. Therefore, a reliable adhesive substrate can be manufactured.

Further, since the organic MSQ film is modified to an inorganic film by eliminating the methyl group (CH ₃ ), the curing time after bonding the substrate can be significantly shortened. As a result, the throughput of the substrate bonding process can be increased.

Next, a modified example of this embodiment will be described. That is, a case where a resin containing silicon is applied only to the surface of one of the two substrates to be bonded will be described.
FIG. 6 is a process cross-sectional view illustrating the main part of the substrate bonding method according to the present embodiment. In this figure, the same elements as those described above with reference to FIG.

  That is, as shown in FIGS. 6A to 6C, cleaning, application of MSQ, and plasma irradiation treatment are performed. However, in this embodiment, as shown in FIG. 6D, the MSQ is applied only to the surface of one of the two substrates W1 and W2 to be bonded and plasma-treated. In this way, the process of applying MSQ to the surface of the substrate W2 can be omitted, so that the manufacturing time can be further shortened. Further, since the thickness of the MSQ film is reduced, the distance between the substrates W1 and W2 can be reduced. As a result, a finer device, a cell with a small gap, or the like can be formed.

FIG. 7 is a schematic diagram showing the configuration of the substrate bonding apparatus according to the embodiment of the present invention.
The substrate bonding apparatus 20 of the present embodiment includes a control unit 21, a cleaning unit 22 controlled by the control unit 21, a resin coating unit 23, a plasma processing unit 24, a bonding unit 25, and an inspection unit 26. Further, the substrate bonding apparatus 20 may include a transport robot (not shown) that transports the supplied substrates W1 and W2 to the next unit.

Further, between these units, for example, a predetermined reduced pressure atmosphere of about several tens of pascals or an atmosphere purged with a rare gas such as He, Ar, N ₂ may be used, and the substrate may be transferred in-line. . For example, when the substrate is transported from the plasma processing unit 24 to the bonding unit 25, it is possible to prevent moisture from adhering to the surface of the resin and oxidation from proceeding if it is not exposed to the atmosphere.

  When the substrates W1 and W2 are supplied to the substrate bonding apparatus 20, the substrate is transported in the order of the cleaning unit 22, the resin coating unit 23, the plasma processing unit 24, and the bonding unit 25, and cleaning, MSQ coating, plasma processing, and bonding are performed respectively. Perform with the unit. Finally, the bonded substrates are conveyed to the inspection unit 26 and inspected for adhesive strength and the like.

FIG. 8 is a schematic view illustrating the configuration of the plasma processing unit 24.
As shown in the figure, the plasma processing unit 24 has a structure in which a lower electrode 28 and an upper electrode 30 are respectively provided in a chamber 27. The substrate 10 is placed on the lower electrode 28. Then, gas is supplied to the inside of the chamber 27, and the vacuum pump 29 is evacuated to a predetermined pressure in the chamber. Then, plasma 12 is generated between the upper electrode 30 and the lower electrode 28 inside the chamber 27 using a high frequency power source. The lower electrode 28 has a built-in heater 31 and can heat the substrate 10 to a predetermined temperature. Using such a unit, the substrate 10 is irradiated with gaseous plasma 12 containing oxygen gas or the like.
However, the structure of the plasma processing unit 24 in the present embodiment is not limited to that illustrated in FIG. 8, and any structure that can generate plasma may be used. For example, as means for generating plasma, a microwave or the like may be used instead of the high-frequency power source.

FIG. 9 is a schematic view illustrating the configuration of the joining unit 25.
As shown in the figure, the substrates W1 and W2 are electrostatically attracted to the upper substrate holder 38 and the lower substrate holder 32, respectively. When the lower substrate holder 32 is moved up and down by the motor 33, the substrates W1 and W2 are pressure-bonded. The upper substrate holder 31 and the lower substrate holder 32 include heaters 34 and 35, respectively, to heat the substrates W1 and W2 to a predetermined temperature. The chamber 36 can be evacuated by a vacuum pump 37. Instead of evacuating the chamber 36 with the vacuum pump 37, the chamber 36 may be purged with a rare gas or nitrogen gas.

  As described above, the substrate bonding apparatus 20 according to the present embodiment includes the plasma processing unit 24 in the previous process of the bonding unit 25. By modifying the MSQ film 11 on the surface as a pretreatment of the substrates to be bonded, it is possible to improve the bonding strength and shorten the bonding time as described above.

In the present embodiment, each unit does not necessarily have to be independent.
FIG. 10 is a schematic view illustrating a substrate bonding apparatus in which the plasma processing unit 24 and the bonding unit 25 are configured using a common chamber.
That is, plasma processing and substrate pressure bonding can be performed in the same chamber. In this way, the apparatus can be miniaturized and can be pressure-bonded without exposing the substrate to the atmosphere after plasma processing.

  The embodiments of the present invention have been described above with reference to specific examples. However, the present invention is not limited to these specific examples.

  For example, the conditions and materials of each step constituting the substrate bonding method of the present invention are not limited to the above specific examples, and those appropriately selected and adopted by those skilled in the art include the present invention as long as they include the gist of the present invention. It is included in the range.

It is a flowchart showing the principal part of the manufacturing method of the semiconductor device concerning embodiment of this invention. It is process sectional drawing showing the principal part of the manufacturing method of the semiconductor device concerning embodiment of this invention. It is a schematic cross section showing the adhesive substrate adhere | attached by the method of this embodiment. It is a cross-sectional schematic diagram which illustrates the reaction mechanism in the principal part of the manufacturing method of the semiconductor device concerning embodiment of this invention. (A) is a graph showing the change over time of the peak intensity obtained by FTIR, and (b) is a graph showing the change over time of the film thickness of the MSQ film. It is process sectional drawing showing the principal part of the manufacturing method of the semiconductor device concerning a present Example. It is a schematic diagram showing the structure of the semiconductor device concerning embodiment of this invention. It is a schematic diagram which illustrates a part of semiconductor device concerning embodiment of this invention. It is a schematic diagram which illustrates a part of semiconductor device concerning embodiment of this invention. 4 is a schematic view illustrating a substrate bonding apparatus in which a plasma processing unit 24 and a bonding unit 25 are configured using a common chamber. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Substrate 11 Silicon-containing resin film 12 Plasma 12 Oxygen plasma 13 Oxygen radical 15 H ₂ , CO _X
20 substrate bonding apparatus 21 control unit 22 cleaning unit 23 coating unit 24 plasma processing unit 25 bonding unit 26 inspection unit 27 chamber 28 lower electrode 29 vacuum pump 30 upper electrode 31 heater 31 substrate holder 32 lower substrate holder 33 motor 34, 35 heater 36 Chamber 37 Vacuum pump 38 Upper substrate holder

Claims (10)

A first step of cleaning each of the first main surface of the first substrate and the first main surface of the second substrate;
A second step of applying a resin containing silicon to at least one of the first main surface and the second main surface;
A third step of irradiating the resin with plasma;
A fourth step of pressure-bonding the first and second substrates with the first main surface of the first substrate facing the first main surface of the second substrate;
A substrate bonding method comprising:   2. The substrate bonding method according to claim 1, wherein the resin containing silicon is MSQ (Methyl Silsesquioxane).   2. The substrate bonding method according to claim 1, wherein the resin containing silicon is HSQ (Hydrogen Silsesquioxane).   The substrate adhesion method according to claim 1, wherein the plasma is oxygen-containing plasma.   The substrate bonding method according to claim 1, wherein the third step is performed in a reduced pressure atmosphere.   The substrate bonding method according to claim 1, wherein the fourth step is performed in a reduced pressure atmosphere.   6. The substrate bonding method according to claim 1, wherein the fourth step is performed in a gas atmosphere different from the atmosphere.   The resin containing silicon is applied to the first main surface of the first substrate and the first main surface of the second substrate in the second step, respectively. The substrate bonding method according to any one of 1 to 7. A cleaning unit for cleaning the substrate;
An application unit for applying a resin to the main surface of the substrate;
A plasma processing unit for irradiating the main surface of the substrate coated with the resin with plasma;
A bonding unit for crimping the substrate;
A substrate bonding apparatus comprising: The substrate bonding apparatus according to claim 9, wherein the plasma processing unit and the bonding unit are provided in a common chamber.

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