News Column

Patent Issued for Techniques for Bonding Substrates Using an Intermediate Layer

August 20, 2014



By a News Reporter-Staff News Editor at Electronics Newsweekly -- A patent by the inventors Ruben, David A. (Mesa, AZ); Sandlin, Michael S. (Chandler, AZ), filed on December 23, 2010, was published online on August 5, 2014, according to news reporting originating from Alexandria, Virginia, by VerticalNews correspondents.

Patent number 8796109 is assigned to Medtronic, Inc. (Minneapolis, MN).

The following quote was obtained by the news editors from the background information supplied by the inventors: "The semiconductor and electronics industry uses material bonding techniques to bond different substrates together during semiconductor/circuit fabrication. Direct bonding is one type of bonding technique that is frequently used to bond different materials together. Direct bonding involves bonding different materials together without the aid of a specific bonding agent such as, for example, adhesive, wax, solder, or the like. Direct bonding techniques may be used to form component packages that house electronic components. A component package may be useful to protect the electronic components from different environmental conditions such as, e.g., pressure changes, moisture, bodily fluids, or the like.

"In some examples, component packages may be placed in an oven after bringing the substrates of the component package in close contact to cause covalent bonds to form between the different substrates. Because this heating process included in forming a direct bond may involve heating the bond to an elevated temperature, temperature-sensitive components of the package may experience thermal damage when placed in a package that is subsequently sealed using direct bonding techniques. Moreover, because the process of forming a direct bond may involve one or more cycles of heating and cooling, mismatches between coefficients of thermal expansion for different substrates being bonded may cause warping and thermal stress fractures to develop between the different substrates. Warping and thermal stress fractures may weaken the bond between the different substrates and may reduce the hermeticity of a component package formed using direct bonding techniques."

In addition to the background information obtained for this patent, VerticalNews journalists also obtained the inventors' summary information for this patent: "A laser bonding process according to the present disclosure fuses two substrates together using an intermediate layer. The laser bonding process may include the following procedures. First, the substrates to be bonded may be polished and cleaned. The intermediate layer may then be deposited as a thin film on one or both of the substrates. Subsequently, the substrates may be brought together such that the intermediate layer is sandwiched between the two substrates. Electromagnetic (EM) radiation, e.g., output from a laser device, may then be directed through one of the substrates and onto the intermediate layer in order to heat the intermediate layer. This heating of the intermediate layer may form an enhanced bond between the substrates. The enhanced bond formed between the substrates may be transparent, mechanically strong, corrosion resistant, and may be used to form a hermetically sealed cavity, in some examples.

"The parameters of the laser bonding process, e.g., the wavelength of EM radiation, the substrate materials used, and intermediate layer materials used, may be selected such that the substrates are transparent to the EM radiation while the intermediate layer absorbs the EM radiation. Thus, the parameters of the process may be selected such that EM radiation may be transmitted through one of the substrates and absorbed by the intermediate layer sandwiched between the substrates. The heat generated in the intermediate layer due to the absorption of the EM radiation by the intermediate layer may fuse the two substrates together.

"The heat generated in the intermediate layer may heat only a localized region of the substrates, and therefore the laser bonding process according to the present disclosure may be a low temperature processing technique that is suitable for forming hermetically sealed enclosures including temperature sensitive electronic components. Additionally, since similar substrate materials may be used to form the enclosures and since the process is performed at room temperature, the enclosures produced may not incur stress fractures due to generalized wafer heating and cooling that may adversely affect the hermeticity of the enclosure.

"Such hermetically sealed enclosures fabricated according to the present disclosure may be used to house a broad range of electronic components, including, but not limited to, solar cells, electronic display devices, microelectronics, and micro-electromechanical systems (MEMS) components. Additionally, the materials used as substrates for the enclosures may be biocompatible (e.g., glass), and therefore the enclosed electronic devices may be implantable. Accordingly, in some examples the hermetically sealed enclosures may house implantable medical device electronics such as sensors, electrical stimulation devices, and physiological measurement devices. For example, the enclosed electronic devices may, via conductive feedthroughs in the enclosure, provide electrical stimulation (e.g., cardiac pacing or neuorstimulation) and measure electrical activity of the heart, nerves, or muscles.

"In one example according to the present disclosure, a method comprises depositing a thin film on a first surface of a first substrate and moving a second surface of a second substrate into contact with the thin film such that the thin film is located between the first and second surfaces. The method further comprises generating electromagnetic (EM) radiation of a first wavelength, the first wavelength selected such that the thin film absorbs EM radiation at the first wavelength. Additionally, the method comprises directing the EM radiation through one of the first and second substrates and onto a region of the thin film until the first and second substrates are fused in the region.

"In another example according to the present disclosure, a device comprises a first glass substrate, a second glass substrate, and a bonding region between the first and second glass substrates. The first and second glass substrates are fused together in the bonding region and the bonding region comprises silicon.

"In another example according to the present disclosure, a method comprises depositing a thin film on a first surface of a first wafer and moving a second surface of a second wafer into contact with the thin film such that the thin film is located between the first and second surfaces and such that the first and second wafers at least partially define a plurality of cavities. The method further comprises generating electromagnetic (EM) radiation of a first wavelength, the first wavelength selected such that the thin film absorbs EM radiation at the first wavelength. Additionally, the method comprises directing the EM radiation through one of the first and second wafers and onto a region of the thin film until the first and second wafers are fused in the region.

"In another example according to the present disclosure, a method comprises forming a stack of N substrates. At least one of a plurality of intermediate layers is disposed between each of the N substrates. The method further comprises generating electromagnetic (EM) radiation of a first wavelength, the first wavelength selected such that each of the plurality of intermediate layers absorbs EM radiation at the first wavelength. Additionally, the method comprises directing the generated EM radiation through the stack of N substrates and the plurality of intermediate layers until each of the N substrates are fused to another one of the N substrates. N is an integer greater than 2.

"The details of one or more examples are set forth in the accompanying drawings and the description below. Other features, objects, and advantages will be apparent from the description and drawings, and from the claims."

URL and more information on this patent, see: Ruben, David A.; Sandlin, Michael S.. Techniques for Bonding Substrates Using an Intermediate Layer. U.S. Patent Number 8796109, filed December 23, 2010, and published online on August 5, 2014. Patent URL: http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1&u=%2Fnetahtml%2FPTO%2Fsrchnum.htm&r=1&f=G&l=50&s1=8796109.PN.&OS=PN/8796109RS=PN/8796109

Keywords for this news article include: Electromagnet, Semiconductor, Medtronic Inc., Electronic Components.

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Source: Electronics Newsweekly


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