I am a customer of universitywafer.com, saw on your website you provide wafer bonding service; wonder what kind of wafer bonding you provide; and if you provide adhesive wafer bonding.
What is Silicon Bonding?
Wafer Bonding Service
A PhD candidate requested a qutoe for the following:
Question:
Answer:
YES, we can provide "wafer bonding" of various kinds.
In the Semiconductor Industry one does different kinds of bonding of wafer.
- One uses "Wax Mounting" between semiconductor wafers or wafers and metal plates. Such bonding is reversible, in that subsequently, the wax can be dissolved and the wafer separated. Some such "Waxes" can maintain the bond up to about 200ºC.
- One uses Epoxy bonding between ingots or wafers and metal or graphite parts, and to bond electronic components to printed circuit cards. Although Epoxy bonds break down above certain temperature limits (about 100ºC) they are not considered a reversible bond.
- Most often, wafer bonding refers to molecular bonding. In this case, wafers of the same or compatible substances, are very well polished, protected from Oxidation and/or moisture and then pressed together. When done well this forms a permanent bond essentially as strong as the bonded materials. One often bonds silicon wafers, or metal blocks in this way.
An important form of bonding involves the making of Silicon on Insulator (SOI) wafers. In this case one grows an SiO2 film on a polished Silicon wafers. Then one presses together the SiO2 covered faces to form a molecular bond that is so strong that one of the so bonded wafers can then be ground with an abrasive wheel to a thickness of less than 10µm. This type of bonding is also used in the making of MEMS devices.
We do all of above forms of bonding, and others as well.
If you describe your application in more detail, specifying the nature and size of the wafers to be bonded and the conditions under which the bond is to remain, then we will be able to recommend a process and quote a price. Do specify how many wafers you will need bonded because most of the work is in the setup of the operation so the unit cost strongly depends on the number of wafer processed.
Reference #139836 for specs and pricing.
Get Your Quote FAST! Or, buy online and start researching today!
Bonding Silicon to Fabricate Devices
A postdoc requested help with the following:
We are seeking to design a silicon-based devices to fabricate evenly-distributed polymer microparticles. I have several questions regarding that:
- Which thickness is the best for the silicon wafer in designing this kind of device? Is that 500μm?
- We plan to do the anodic bonding of the silicon wafer with glass wafer. And may buy your Borofloat 33 wafers. Can I ask if the wet oxidization is necessary before this bonding?
- Do you have any companies recommended for anodic bonding? Or do you provide this kind of service?
Reference #265416 for specs and pricing.
How do you Bond Silicon Wafers?
Silicon bonding refers to the type of chemical bond that forms between silicon atoms in a silicon molecule or compound. Silicon has four valence electrons, which allows it to form strong covalent bonds with other elements, such as oxygen, carbon, and hydrogen. The covalent bonds result in a tetrahedral arrangement of the atoms in a silicon molecule, giving it a distinct chemical structure. In solid silicon, these covalent bonds are further strengthened by the sharing of electrons between adjacent silicon atoms, leading to the formation of a continuous network of covalent bonds, known as a covalent crystal lattice.
Silicon wafers can be bonded using various techniques, including:
-
Direct Wafer Bonding: This process involves bringing the two wafers into direct contact and applying pressure and heat to bond the wafers together.
-
Anodic Bonding: This process uses an electrical voltage to bond the wafers together, rather than pressure and heat.
-
Fusion Bonding: This process uses heat and pressure to bond the wafers, and can be performed in a high-pressure and high-temperature furnace.
-
Adhesive Bonding: This process involves applying a thin layer of an adhesive material between the two wafers and then curing the adhesive under heat and pressure.
The choice of bonding method depends on the specific application, desired bonding strength, and other factors such as substrate compatibility and process cost.
How to Bond Silicon Wafers Together
Wafer bonding is a very important technology in the development of sensors and other micromachined devices. It enables a much smaller, less expensive, and more reliable way to package such devices.
There are a number of different ways to bond silicon wafers together, depending on the application and the specific requirements. This article explains some of these methods and provides basic suggestions for verifying that the wafers are bonded correctly.
Surface bonding
When mirror-polished, flat and clean wafers of almost any material are brought into contact at room temperature, they are locally attracted to each other by van der Waals forces. This phenomenon is referred to as surface bonding, and it can be used to adhere or bond wafers together to create devices such as silicon-on-insulator (SOI) technology, sensors, actuators, optical devices and others.
The basic principles of surface bonding are based on the chemistry that happens when two surfaces come into contact and form chemical bonds between the molecules on each of the surfaces. These chemical bonds have a relatively high energy, which is measured in dynes per centimeter. Materials with a high surface energy are very liquid-friendly, and they flow easily when they get wet.
In addition to forming chemical bonds, a high-energy surface may also attract water molecules. This can happen if the two surfaces are not completely smooth or if one surface has been treated with something to make it hydrophilic, such as one or more monolayers of oxygen or water.
A low-energy surface, on the other hand, may not be as liquid-friendly, or it may not have enough water to "wet out" the surface to make a strong bond. In this case, adhesives are used to stick the two surfaces together.
The adhesives used in surface bonding are typically a combination of water and an organic solvent. The water helps to wet out the high-energy surface, while the organic solvent is responsible for removing any contaminants.
There are several methods to bond silicon wafers together, and each method has its own set of advantages. These include ease of use, cost-effectiveness and speed.
Generally, the first step is to prepare the two wafers. These steps will vary depending on the type of device you are making, but it's essential that the substrates are properly prepared for the process.
After the preparation is completed, it's time to bond the two wafers together. These processes require precision and high-quality products, so it's important to do them correctly.
After the bonding has been completed, it's essential to test it to ensure that it's successful. There are a number of ways to do this, but the most common is to dip the bonded wafers in buffered HF for an hour to see if they stay bonded. It's also a good idea to cleave the bonded silicon wafer pair to see how easily they cleave together and whether there are any voids or unbonded areas.
Adhesive bonding
Adhesive bonding is an important step in semiconductor manufacturing. Its aims are to create reliable electrical, thermal and mechanical connections between wafers or other components. It is used in many industries, including aerospace, lighting, electrical and electronics, and automotive.
A wide range of adhesives is available to bond silicon wafers. These can be permanent or temporary, depending on the needs of the application. In order to be successful, the adhesives must have high shear bonding strength and be able to resist backgrinding. They also need to conform to bumps and features of the device wafer without stress.
The bonding process is a chemical reaction between the two substrates. This causes them to adhere to each other and form a strong bond. The adhesive is then cured using a light source or heat treatment, depending on the type of material.
There are several different types of adhesives that can be used to bond silicon wafers, each with its own advantages and disadvantages. One of the most common adhesives is a polymer. This is an inexpensive and easy to use bonding method that provides good bond strength.
Another type of adhesive is a wax film. This type of adhesive is able to hold high shear bonding strength up to 60oC, protecting sensitive wafer materials from fracture during backgrinding.
Unlike most adhesives, this type of adhesive does not have an aqueous phase, which means it can be applied to a wide variety of surfaces. It is also compatible with clean room processing and provides a very good bond quality.
The adhesive is cured by using a light source or heat treatment, but it can also be cured using chemical debonding. This method allows for a 99% bonding yield and 4.8 MPa of bond strength.
In addition to its high bond strength, this type of adhesive is also resistant to corrosion and oxidation. This makes it a popular choice for microelectronics applications.
There are a number of methods for bonding silicon wafers, including surface bonding, thermal bonding and direct bonding. These methods all have their advantages and disadvantages, but they all produce a strong, durable and long-lasting bond.
High-temperature bonding
High-temperature bonding is a process used to join semiconductor wafers together. It is a popular method for manufacturing microelectronic devices because it allows for higher throughput and easier alignment of the components. However, it is a delicate process that requires careful attention to the materials and processes involved.
This method involves placing silicon and glass wafers above one another and then applying an electrode. This electrode may be a needle, full-area cathode electrode, or a chuck.
The glass and silicon substrates are then heated to a high temperature and an electric field is applied to the substrates. The resulting shear-thickening effect can strengthen the bond between the two surfaces, but it is also capable of cracking the surface.
A second type of high-temperature bonding involves the use of a liquid-phase eutectic alloy as the bonding layer. This is a more durable bonding process than direct wafer bonding because it is less sensitive to scratches and other surface irregularities. It is also able to control temperature distribution across the bonded stack, which helps reduce residual stresses that can occur during thermal cycling.
This process is ideal for high-volume production of electronic devices because it can be used with a wide range of standard integrated circuit materials, including photonic devices. It can also produce crack-free wafers, which is a key requirement for MEMS applications.
The first step in this process is to grow a wet oxide layer on the two silicon wafers. This can be done using a bruce furnace at a temperature of around 200°C.
After the wet oxide layer has formed, both silicon wafers must be cleaned thoroughly. This is important to prevent bubbles from forming.
An SU-8 coating can be applied to the top of the silicon wafers through spin-on or spray-on processes. This coating is very effective for planar wafers, but it can cause problems with non-planar or free-standing structures.
Alternatively, a chemical bonding process can be used to create a strong bond between the silicon and gold substrates. This process is more complicated than a liquid-phase eutectic bonding process, but it can be used to create hermetic seals between silicon and gold at low temperatures.
Thermal annealing
Thermal annealing is a common technique used to strengthen materials by raising them from room temperature to a higher temperature, and then reducing them back to normal. This is done in order to improve a material's strength, ductility, and hardness. It also helps to remove structural imperfections that may otherwise degrade a product's quality.
Thermal annealing can be done in several different ways. One method is to heat up a wafer to a specific temperature and then hold it there for a certain amount of time, usually for just a few seconds. The temperature can then be lowered, and the process can be repeated until the desired level of hardness is reached.
Another method involves exposing a wafer to a gas atmosphere at a specific temperature. This process, called rapid thermal annealing, causes the vacancies in a wafer to diffuse out of the crystal lattice and into an oxide layer that is formed on the surface of the wafer.
During this process, the vacancies in the wafer begin to disperse and then become annihilated. This process reduces the vacancy concentration in the silicon wafer, which will eventually result in an increased carrier lifetime for the silicon.
According to a study, thermal annealing at low temperatures can enhance the bonding energy of bonded bare silicon wafers. This is because it causes the fluorine in the chemically grown SiO2 to promote the formation of covalent bonds.
This type of bonding has a wide range of applications, including high-temperature microelectronics. In addition, it is an effective way to increase the bonding yield of a silicon wafer.
The bonding of a silicon wafer can be improved by adding a coating that helps to prevent it from breaking down during the annealing process. The coating can be made from metal or a polymer.
If the coating is metallic, it can be created with a laser or an electron beam. However, the metal needs to be in a good state of purity before it can be used. The metal needs to have a low impurity content so that it is not harmful to the silicon.