CN111370339A - Room temperature isostatic pressing metal bonding method for wafers - Google Patents

Abstract

The present disclosure provides a room temperature isostatic pressing metal bonding method for wafers, including: step S1: cleaning the wafer to be bonded to remove impurities on the wafer surface; step S2: depositing a metal intermediate layer on the cleaned wafer surface; Step S3: Align the front faces of the two wafers on which the metal interlayer deposition has been completed, mount them into the mold after fixing, and use a vacuum pump to vacuumize and seal the mold; Step S4: Place the well-sealed mold in an isostatic In the high-pressure cylinder of the pressure bonding machine, lock the high-pressure cylinder and fill it with a liquid pressure medium, so that the mold is completely immersed in the liquid pressure medium and directly contacts with the liquid pressure medium; Step S5: Set the bonding pressure and bonding time, and treat the The bonded wafers are bonded, and after the bonding is completed, the pressure is released and the bonded wafers are taken out to complete the room temperature isostatic metal bonding of the wafers.

Description

Room temperature isostatic pressing metal bonding method for wafers

technical field

The present disclosure relates to the technical field of wafer bonding technology, and in particular, to a room temperature isostatic pressing metal bonding method of wafers, which adopts isostatic pressing bonding equipment to realize the room temperature bonding of wafers.

Background technique

Semiconductor wafer bonding technology is an important technology in semiconductor technology. It has greatly promoted the realization of quasi-monolithic integration of devices of different materials, the performance improvement of optoelectronic devices and the development of new semiconductor devices. Common wafer bonding methods include: adhesive bonding, anodic bonding, direct wafer bonding, and metal eutectic bonding.

The adhesive bonding uses organic materials such as epoxy resin as the bonding layer for wafer bonding. During the bonding, the surface morphology of the sample can be compensated and some surface treatment steps are avoided. However, due to the use of The thickness of the adhesive is usually in the micron level, and the adhesive itself has poor thermal conductivity, so it will seriously affect the heat dissipation of the device; anodic bonding is a process of applying a strong electrostatic field to the bonding material at a certain temperature to achieve bonding. This technology has lower requirements on the surface roughness of the wafer than direct bonding, and relatively loose requirements for the bonding environment. This technology is generally used for the bonding of alkali-containing glass materials. After bonding, there may be relatively Large residual thermal stress; direct wafer bonding is a wafer bonding method developed in recent years that does not require an intermediate layer. Avoiding the intermediate layer can indeed effectively reduce the thermal resistance of the bonding interface. However, this bonding technology The requirements for wafer surface roughness and cleanliness are very high, and it is undoubtedly very expensive and complicated to obtain a bonding surface that meets the requirements, which poses great challenges to the cost and efficiency of wafer bonding. In addition, the method The surface modification of the wafer surface is carried out by infiltration or dry treatment, which makes the wafer surface extremely hydrophilic or hydrophobic, so the scope of application is also limited. Metal eutectic bonding is achieved by the fusion of two metals into an alloy and solidification. Compared with the above several bonding methods, metal eutectic bonding is more attractive. The main reason is that the metal forms a fluid state and is easy to bond. Region expansion, so can accommodate higher surface topography and non-planarity than other bonding methods, however, the metal melt height must be high enough to wet the profiled region (usually 3-5 μm thick) and be able to form a high melting point metal at the interface For inter-compounds, the eutectic metal bonding temperature needs to reach the eutectic temperature of the alloy, which usually needs to be hundreds of degrees Celsius.

With the development of MEMS, optoelectronic technology, chip integration and system packaging, new requirements have been put forward for the low-temperature wafer bonding process. Low-temperature bonding technology that is non-destructive to devices has become an inevitable development.

public content

(1) Technical problems to be solved

Based on the above problems, the present disclosure provides a room temperature isostatic pressing metal bonding method for wafers, so as to alleviate the device damage caused by high cost, low efficiency, high temperature or uneven pressure in wafer bonding in the prior art. question.

(2) Technical solutions

In the present disclosure, a room temperature isostatic pressing metal bonding method for wafers is provided, including:

Step S1: cleaning the wafer to be bonded to remove impurities on the surface of the wafer;

Step S2: depositing a metal intermediate layer on the cleaned wafer surface;

Step S3: align the front faces of the two wafers on which the metal intermediate layer deposition has been completed respectively, mount them into the mold after fixing, and use a vacuum pump to vacuumize and seal the mold;

Step S4: placing the well-sealed mold in the high-pressure cylinder of the isostatic pressure bonding machine, locking the high-pressure cylinder, and filling it with a liquid pressure medium, so that the mold is completely immersed in the liquid pressure medium and is in direct contact with the liquid pressure medium;

Step S5 : setting the bonding pressure and bonding time, and bonding the wafers to be bonded. After the bonding is completed, the pressure is released and the bonded wafers are taken out to complete the room temperature isostatic metal bonding of the wafers.

In the embodiment of the present disclosure, the preparation material of the wafer includes: any one of Si, GaAs, InP, GaN, SiC, AlN or Ga ₂ O ₃ based structural materials.

In the embodiment of the present disclosure, in step S1, a chemical cleaning method is adopted.

In the embodiment of the present disclosure, in step S2, the deposition method of the metal intermediate layer includes at least one of sputtering, chemical vapor deposition, evaporation, electroplating or laser metal deposition.

In the embodiment of the present disclosure, in step S2, the metal intermediate layer includes:

The adhesion layer metal, the preparation material includes: at least one of Ti, Ni or Cr; and

For bonding the intermediate layer, the preparation material includes: at least one of Au, Cu, Ag, In, Ti, Sn, Pt, Cr, Ge or Ni.

In the embodiment of the present disclosure, the metal thickness of the adhesion layer is 5-100 nm.

In the embodiment of the present disclosure, the thickness of the bonding intermediate layer is 100-500 nm.

In the embodiment of the present disclosure, in step S5, the bonding process of the wafer is performed at room temperature.

In the embodiment of the present disclosure, in step S5, the bonding pressure is 30-200 MPa, and the bonding time is 30-120 min.

In the embodiment of the present disclosure, the effective bonding area of the wafer accounts for more than 95%.

(3) Beneficial effects

It can be seen from the above technical solutions that the room temperature isostatic pressing metal bonding method of the wafer of the present disclosure has at least one or a part of the following beneficial effects:

(1) Reduce the thickness of the metal intermediate layer by an order of magnitude, which helps to reduce the interface thermal resistance;

(2) Wafer bonding of ultra-thin metal intermediate layers can be realized at room temperature, avoiding the impact of high temperature on the performance of materials and devices;

(3) The requirements for the surface state of the wafer are not high, and there is no need to perform additional polishing and modification treatments on the surface of the material, the process is simplified, the cost is greatly reduced, and the bonding efficiency is improved;

(4) Ensure that the sample is uniformly stressed, will not cause physical damage to the wafer, and ensure that the performance of materials and devices is not affected;

(5) It is not limited by the size and shape of the sample, and can meet the bonding of wafers of multiple sizes.

Description of drawings

FIG. 1 is a schematic flowchart of a room temperature isostatic metal bonding method for wafers according to an embodiment of the present disclosure.

Figure 2 is a schematic diagram of the system composition of the isostatic pressing machine.

FIG. 3 is a schematic diagram of a test result of an ultrasonic scanning microscope of a wafer bonded by a room temperature isostatic pressing metal bonding method according to an embodiment of the present disclosure.

4 is a schematic diagram of an electron microscope scanning result of wafers bonded by a room temperature isostatic metal bonding method according to an embodiment of the present disclosure.

[Description of Symbols of Main Elements of the Embodiments of the Present Disclosure in the Drawings]

1-upper cover; 2-seal ring; 3-liquid pressure medium; 4-sample basket; 5-sample; 6-lifting system; 7-high pressure cylinder; 8-screw; 9-lower cover; 10-pressure medium pipeline; 11-pressure gauge; 12-support frame.

Detailed ways

The present disclosure provides a room temperature isostatic metal bonding method for wafers, which still belongs to the category of metal bonding, and can be used in the fields of integrated circuit manufacturing, micro-electromechanical system (MEMS) packaging, and multi-functional chip integration. Eutectic bonding is fundamentally different. It not only reduces the thickness of the metal intermediate layer by an order of magnitude, but also realizes wafer bonding of ultra-thin metal intermediate layers at room temperature, avoiding the impact of high temperature on the performance of materials and devices; The surface state of the wafer is not required to be high, and additional polishing and activation treatment of the surface is not required; during the bonding process, the high-pressure cylinder applies a higher pressure to the wafer from all directions through the liquid pressure medium equally, which will not cause any damage to the wafer. The wafer causes physical damage to ensure that the material and device performance are not affected.

In order to make the objectives, technical solutions and advantages of the present disclosure clearer, the present disclosure will be further described in detail below with reference to the specific embodiments and the accompanying drawings.

In an embodiment of the present disclosure, a method for metal bonding by room temperature isostatic pressing of wafers is provided. With reference to FIGS. 1 to 4 , the method for metal bonding by room temperature isostatic pressing of wafers includes:

Step S1: cleaning the wafer to be bonded to remove impurities on the surface of the wafer;

Step S2: depositing a metal intermediate layer on the cleaned wafer surface;

Step S3: align the front faces of the two wafers on which the metal intermediate layer deposition has been completed respectively, mount them into the mold after fixing, and use a vacuum pump to vacuumize and seal the mold;

Step S4: placing the well-sealed mold in the high-pressure cylinder of the isostatic pressure bonding machine, locking the high-pressure cylinder, and filling it with a liquid pressure medium, so that the mold is completely immersed in the liquid pressure medium and is in direct contact with the liquid pressure medium;

Step S5 : setting the bonding pressure and bonding time, and bonding the wafers to be bonded. After the bonding is completed, the pressure is released and the bonded wafers are taken out to complete the room temperature isostatic metal bonding of the wafers.

In the step S1, the wafer to be bonded is cleaned. First, the wafer to be bonded is ultrasonically cleaned with acetone, ethanol and deionized water for 10-60 min, then rinsed with deionized water, and then washed with HCl:H ₂ O The solution of =1:1~10 is ultrasonically cleaned for 5-30min of the bonded wafer, then rinsed with deionized water, and finally dried with a nitrogen gun;

In the step S2, a metal intermediate layer is deposited on the cleaned wafer surface, and the metal intermediate layer is a Ti/Au bimetallic layer, wherein the metal Ti is used as the adhesion layer, the thickness of the metal Ti is 5-50 nm, and the sputtering power is 100-300W, the thickness of Au is 100-500nm, the sputtering power is 100-300W; the metal of the adhesion layer is one of Ti, Ni or Cr, and the bonding intermediate layer is one of Au, Cu or Al, prepared The method is one of magnetron sputtering, electron beam evaporation or electroplating; preferably, magnetron sputtering equipment is used to perform DC sputtering and radio frequency sputtering of Ti and Au metal targets on the wafer respectively;

In the step S3, the front faces of the two wafers on which the metal intermediate layer has been deposited are aligned and bonded, and after being fixed, they are loaded into the mold, the mold is evacuated with a vacuum pump, and the mold is sealed after the air in the mold is discharged;

In the step S4, as shown in FIG. 2, the high-pressure cylinder 7 is fixed on the support frame 12 by the screws 8, which is provided with the lifting system 6; the well-sealed mold is placed in the high-pressure cylinder of the isostatic pressing machine, Close the upper cover 1, the lower cover 9, lock the high-pressure cylinder 7, the high-pressure cylinder is provided with a sealing ring 2, fill the liquid pressure medium 3 through the pressure medium pipeline 10, and place the mold into the sample basket 4, so that the mold is completely immersed in the liquid pressure medium 3, and directly contact with the liquid pressure medium, use high-pressure equipment to apply a certain pressure to the pressure medium in the cylinder, and apply the pressure to the wafer to be bonded equally in all directions through the pressure medium; the isostatic pressure bonding machine works When the sample 5 sealed in the mold is put into the high-pressure cylinder, the liquid pressure medium is injected into the high-pressure cylinder along the pressure medium pipeline 10 by the high-pressure oil pump, and is in direct contact with the mold, so that the isotropy can be applied to the sample. The pressure is monitored by the pressure gauge 11 in real time;

In the step S5, enter the control system of the isostatic pressure bonding machine, set the bonding pressure and bonding time, and bond the to-be-bonded wafers. The pressure is 30-200MPa, and the bonding time is 30min-120min.

As shown in Figure 3, the ultrasonic scanning microscope image after bonding shows that the effective bonding area of the wafer can reach 96.37%, and the unbonded rate is 3.63%.

4 is a scanning electron microscope image of a cross-section of a bonded wafer according to the present disclosure. It can be seen from the figure that the bonding interface is clear and the thickness of the metal intermediate layer is uniform.

So far, the embodiments of the present disclosure have been described in detail with reference to the accompanying drawings. It should be noted that, in the accompanying drawings or the text of the description, the implementations that are not shown or described are in the form known to those of ordinary skill in the technical field, and are not described in detail. In addition, the above definitions of various elements and methods are not limited to various specific structures, shapes or manners mentioned in the embodiments, and those of ordinary skill in the art can simply modify or replace them.

Based on the above description, those skilled in the art should have a clear understanding of the room temperature isostatic metal bonding method of the wafers of the present disclosure.

To sum up, the present disclosure provides a method for metal bonding by room temperature isostatic pressing of wafers. The isostatic pressing technology is used to ensure that the sample is uniformly stressed, on the one hand, physical damage is avoided, and on the other hand, the metal intermediate is minimized. The thickness of the layer helps to reduce the thermal resistance of the interface; it lowers the requirements for the state of the wafer surface, and does not require additional polishing and modification of the material surface, which greatly reduces the cost and improves the bonding efficiency; it is not affected by the sample size Shape constraints, can meet multi-size wafer bonding.

It should also be noted that the directional terms mentioned in the embodiments, such as "up", "down", "front", "rear", "left", "right", etc., only refer to the directions of the drawings, not used to limit the scope of protection of the present disclosure. Throughout the drawings, the same elements are denoted by the same or similar reference numbers. Conventional structures or constructions will be omitted when it may lead to obscuring the understanding of the present disclosure.

Moreover, the shapes and sizes of the components in the figures do not reflect the actual size and proportion, but merely illustrate the contents of the embodiments of the present disclosure. Furthermore, in the claims, any reference signs placed between parentheses shall not be construed as limiting the claim.

Unless known to the contrary, the numerical parameters set forth in this specification and attached claims are approximations that can vary depending upon the desired properties sought to be obtained from the teachings of the present disclosure. Specifically, all numbers used in the specification and claims to indicate compositional contents, reaction conditions, etc., should be understood as being modified by the word "about" in all cases. In general, the meaning expressed is meant to include a change of ±10% in some embodiments, a change of ±5% in some embodiments, a change of ±1% in some embodiments, and a change of ±1% in some embodiments. Example ±0.5% variation.

Furthermore, the word "comprising" does not exclude the presence of elements or steps not listed in a claim. The word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements.

The ordinal numbers such as "first", "second", "third", etc. used in the description and the claims are used to modify the corresponding elements, which themselves do not mean that the elements have any ordinal numbers, nor do they Representing the order of a certain element and another element, or the order in the manufacturing method, the use of these ordinal numbers is only used to clearly distinguish an element with a certain name from another element with the same name.

Furthermore, unless the steps are specifically described or must occur sequentially, the order of the above steps is not limited to those listed above, and may be varied or rearranged according to the desired design. And the above embodiments can be mixed and matched with each other or with other embodiments based on the consideration of design and reliability, that is, the technical features in different embodiments can be freely combined to form more embodiments.

Those skilled in the art will understand that the modules in the device in the embodiment can be adaptively changed and arranged in one or more devices different from the embodiment. The modules or units or components in the embodiments may be combined into one module or unit or component, and further they may be divided into multiple sub-modules or sub-units or sub-assemblies. All features disclosed in this specification (including accompanying claims, abstract and drawings) and any method so disclosed may be employed in any combination, unless at least some of such features and/or procedures or elements are mutually exclusive. All processes or units of equipment are combined. Each feature disclosed in this specification (including accompanying claims, abstract and drawings) may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Also, in a unit claim enumerating several means, several of these means can be embodied by one and the same item of hardware.

Similarly, it will be appreciated that in the above description of exemplary embodiments of the disclosure, various features of the disclosure are sometimes grouped together into a single embodiment, figure, or its description. However, this method of disclosure should not be interpreted as reflecting an intention that the claimed disclosure requires more features than are expressly recited in each claim. Rather, as the following claims reflect, disclosed aspects lie in less than all features of a single foregoing disclosed embodiment. Thus, the claims following the Detailed Description are hereby expressly incorporated into this Detailed Description, with each claim standing on its own as a separate embodiment of the present disclosure.

The specific embodiments described above further describe the purpose, technical solutions and beneficial effects of the present disclosure in detail. It should be understood that the above-mentioned specific embodiments are only specific embodiments of the present disclosure, and are not intended to limit the present disclosure. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present disclosure should be included within the protection scope of the present disclosure.

Claims (10)

1. A room temperature isostatic pressing metal bonding method of a wafer comprises the following steps:

step S1: cleaning a wafer to be bonded, and removing impurities on the surface of the wafer;

step S2: depositing a metal intermediate layer on the surface of the cleaned wafer;

step S3: aligning and attaching the front surfaces of two wafers respectively subjected to metal intermediate layer deposition, fixing the two wafers, then placing the wafers into a mold, and vacuumizing and sealing the mold by using a vacuum pump;

step S4: placing the well-sealed die in a high-pressure cylinder of an isostatic pressing bonding machine, locking the high-pressure cylinder, and filling a liquid pressure medium into the high-pressure cylinder to ensure that the die is completely immersed in the liquid pressure medium and is directly contacted with the liquid pressure medium;

step S5: and setting bonding pressure and bonding time, bonding the wafer to be bonded, releasing pressure after bonding is finished, and taking out the bonded wafer to complete room-temperature isostatic pressing metal bonding of the wafer.

2. The room temperature isostatic pressing metal bonding method of a wafer as claimed in claim 1, the preparation material of the wafer comprising: si, GaAs, InP, GaN, SiC, AlN, or Ga₂O₃Any one of the base structure materials.

3. The method for bonding metals according to claim 1, wherein in step S1, a chemical cleaning method is used.

4. The method for bonding metals to wafers according to claim 1, wherein the step S2 is a method for depositing a metal intermediate layer comprising: at least one of sputtering, chemical vapor deposition, evaporation, electroplating, or laser metal deposition.

5. The room temperature isostatic pressing metal bonding method of wafer as claimed in claim 1, wherein in step S2, said metal intermediate layer comprises:

the adhesion layer metal is prepared from the following materials: at least one of Ti, Ni or Cr; and

bonding the intermediate layer, preparing a material comprising: at least one of Au, Cu, Ag, In, Ti, Sn, Pt, Cr, Ge or Ni.

6. The method for bonding the metals on the wafer by isostatic pressing at room temperature according to claim 5, wherein the thickness of the metal of the adhesion layer is 5-100 nm.

7. The method as claimed in claim 5, wherein the bonding intermediate layer has a thickness of 100-500 nm.

8. The method for bonding metals according to claim 1, wherein the bonding process is performed at room temperature in step S5.

9. The method for bonding metals according to claim 1, wherein in step S5, the bonding pressure is 30-200MPa and the bonding time is 30-120 min.

10. The room temperature isostatic metal bonding method of a wafer as claimed in claim 1, wherein the effective bonding area ratio of the wafer is greater than 95%.

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