Patent Application
20150340274
The technical field generally relates to methods for producing integrated circuits, and more particularly relates to method of producing integrated circuits with an insulating layer while adhering to a thermal budget for the integrated circuit.
Silicon dioxide is used as an insulator in many integrated circuits, and the quality of the silicon dioxide increases as the density increases. High quality silicon dioxide is more resistant to certain etchants, and may be etched at a more consistent rate than low quality silicon dioxide, so high quality silicon dioxide can simplify downstream processing operations. Some existing processes deposit an insulating layer within trenches, and the aspect ratio of the trenches tends to increase as the size of the integrated circuit decreases. Many insulating layer deposition processes are designed to fill high aspect ratio trenches, but such insulating layer deposition processes may not produce dense, high quality silicon dioxide insulation. For example, some flowable chemical vapor deposition (FCVD) processes are capable of filling trenches with high aspect ratios, but the insulating material is a silicon and nitrogen containing film. Some high aspect ratio processes (HARP) are capable of depositing silicon oxide within trenches having high aspect ratios, but the silicon oxide is generally not a high quality, dense material.
Historically, the FCVD or HARP materials have been exposed to a steam anneal at a temperature of about 500 degrees centigrade (° C.) to convert silicon/nitrogen bonds to silicon oxide bonds, and to begin the densification process. The steam anneal is followed by a dry anneal at an anneal temperature of about 1,000° C. or more, and the high anneal temperature can produce dense, high quality silicon dioxide. However, some substrates have a thermal budget, and the substrate can be degraded by annealing processes that exceed the thermal budget temperature. For example, many substrates that include germanium have a thermal budget of less than 1,000° C., where the thermal budget tends to decrease as the percentage of germanium in the substrate increases. Some III-V substrates, such as gallium arsenide or indium gallium arsenide, have a thermal budget of about 600° C., or about 400° C., and other thermal budget temperature limits exist for other substrates or components in an integrated circuit.
As the size of integrated circuits decreases, the size of components in the integrated circuit also decreases. Fins are formed in the substrate of many integrated circuits, and the strength of the fins decreases as the size of the fin decreases. When the fin becomes small, the densification process tends to bend or break the fins from the substrate, especially when the integrated circuit is annealed at high temperatures. Silicon dioxide has a different coefficient of thermal expansion than the material of some fins, so the higher the temperature of the anneal, the more stress is transferred to the fins when the anneal is performed.
Accordingly, it is desirable to provide methods of producing integrated circuits with an insulating material that is capable of filling high aspect trenches, where the insulating material can be densified at low temperatures. In addition, it is desirable to provide methods of forming integrated circuits with narrow fins, where the fins are not bent or damages when insulating material between adjacent fins is densified. Furthermore, other desirable features and characteristics of the present embodiment will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.
Integrated circuits and methods for producing the same are provided. In an exemplary embodiment, a method for producing an integrated circuit includes forming an insulating layer overlying a substrate, where the insulating layer is formed within a trench. The insulating layer is infused with water, and the insulating layer is annealed while being irradiated. The insulating layer is annealed at a dry anneal temperature of about 800 degrees centigrade or less.
A method for producing an integrated circuit is provided in another embodiment. An insulating layer is formed overlying a substrate and within a trench, where the insulating layer includes a silicon and nitrogen containing film. The silicon and nitrogen containing film is converted to silicon dioxide, and densified with a dry anneal while being irradiated. Densifying the insulating layer increases a density of the insulating layer by about 0.05 grams per cubic centimeter or more.
A method of producing an integrated circuit is provided in yet another embodiment. A plurality of fins are formed in a substrate, where a trench is defined between adjacent fins. The fins have a fin width of about 10 nanometers or less, and the fins are within about 1 degree of vertical. The trench has an aspect ratio of about a height of 10 or more to a width of 1. An insulating layer is formed within the trench, where the insulating layer fills about 95 volume percent or more of the trench. The insulating layer is densified such that the fins are within about 2 degrees of vertical.
The present embodiments will hereinafter be described in conjunction with the following drawing figures, wherein like numerals denote like elements, and wherein:
The following detailed description is merely exemplary in nature and is not intended to limit the various embodiments or the application and uses thereof. Furthermore, there is no intention to be bound by any theory presented in the preceding background or the following detailed description.
An insulating layer is formed overlying a substrate, and the insulating layer is a “gap fill” layer that fills a trench. Flowable type insulating layers are typically used for gap fill applications, so essentially the entire gap is filled with the insulating layer. Many flowable type insulating layers are good at filling gaps, even those with a high aspect ratio, but the high temperature anneals required to convert the insulating material to high quality, dense silicon dioxide may exceed the thermal budget for the substrate, and thermal expansion issues may damage delicate structures on the substrate, as mentioned above. An FCVD insulating layer is good at filling high aspect ratio gaps, but forms a silicon and nitrogen containing film. The silicon and nitrogen containing film can be converted to silicon oxide by infusing the silicon and nitrogen containing film with water and/or annealing it in the presence of steam. The silicon oxide formed may not be as dense as desired, and it can be densified with another anneal. The densification anneal is a dry anneal that removes water and further crosslinks the film, and the temperature of the densification anneal can be reduced by irradiating the insulating layer during the anneal to provide extra energy for the densification. After the insulating layer is densified, additional manufacturing steps may be used to produce the integrated circuit.
Reference is made to
Germanium has a melting point of about 937° C., and the thermal budget of silicon germanium substrates 12 is often less than about 1,000° C. The thermal budget may be designed to prevent germanium from melting within the substrate matrix. The “thermal budget” is a limitation on the temperature, or on the exposure time at certain temperatures, that a substrate 12, integrated circuit 10, or other structure can be exposed to without causing unacceptable harm or damage. In some instances, it is desirable to stay as far below the maximum temperature allowed by the thermal budget as possible, because damage may begin at lower temperatures and increase with the temperature. The thermal budget may be set at a point where the damage is considered too severe, but keeping processing temperatures below the thermal budget may reduce damage that is undesirable but may still produce a workable product. The thermal budget for silicon germanium substrates 12 may depend on the concentration of germanium in the substrate 12. Some exemplary thermal budgets include maximum temperatures not to exceed about 1,000° C., or not to exceed about 800° C., or not exceed about 600° C. Some III-V semiconductor materials may have a thermal budget not to exceed about 600° C., or not to exceed about 500° C., or not to exceed about 400° C. in various embodiments. For example, arsenic in some III-V semiconductors may outgas when the thermal budget is exceeded, so the composition of the substrate 12 can change.
In an exemplary embodiment, a plurality of fins 14 are formed in the substrate 12, where the fins 14 are formed by methods and techniques well known to those skilled in the art. A trench 16 is defined between adjacent fins 14, where the trench 16 has a trench height indicated by the double headed arrow labeled 18 and a trench width indicated by the double headed arrow labeled 20. The trench 16 has an aspect ratio that is the trench height 18 relative to the trench width 20, and the aspect ratio may be about 5 or more to 1 in some embodiments, about 10 or more to 1 in other embodiments, and about 20 to 1 in yet other embodiments. In general, the higher the trench aspect ratio, the more difficult it is to fill the trench 16. The fins 14 have a fin width indicated by the double headed arrow labeled 22, and the fin width 22 may be about 10 nanometers or less in some embodiments, or about 20 nanometers or less in other embodiments, or about 30 nanometers or less in yet other embodiments. The smaller the fin width 22, the easier it is to damage the fin 14 because thin fins 14 are more delicate than thicker fins 14 of the same material. The fins 14 may also be essentially vertical, such as within about 1 degree of vertical. Vertical fins 14 are incorporated into many integrated circuits 10.
In an exemplary embodiment illustrated in
The insulating layer 30 may be formed by depositing a silicon and nitrogen containing film using a flowable chemical vapor deposition (FCVD) process. Not to be bound by theory, but the FCVD process may form an oligomer in the gas phase, where the oligomer is flowable such that is flows into the trench 16, and the oligomer may then further polymerize after flowing into position. In an exemplary embodiment, the FCVD is a plasma chemical vapor deposition process that can use a low carbon or carbon-free silicon containing precursor that includes silicon along with a nitrogen containing precursor. The silicon precursor may be trisilylamine amine, disilylamine, monosilylamine, silane, or other precursors, and the nitrogen containing precursor may be ammonia, nitrogen gas, or other compounds. Other FCVD processes may also be used in alternate embodiments. In alternate embodiments, a high aspect ratio process (HARP) may be used to form the insulating layer 30 overlying the substrate 12 and within the trench 16. In an exemplary embodiment, the HARP may form a silicon dioxide insulating layer 30 using ozone and tetraethyl orthosilicate (TEOS) as precursors in a chemical vapor deposition at less than atmospheric pressure, but other precursors or processes may be used in alternate embodiments. Other methods of producing the insulating layer 30 include spin-on glass (SOG) and spin-on dielectrics (SOD). SOG and SOD are applied as a liquid, and the substrate 12 is spun to distribute the SOG or SOD. The SOG may include silicon-oxygen bonds, as well as silicon-hydrogen bonds. SOG is commercially available, such as ACCUGLASS® T-12B, available from HONEYWELL® Electronic Materials, 1349 Moffett Park Drive, Sunnyvale, Calif. 94089, USA. SOD may be liquid compounds including a silazane compound and optionally a solvent, where the SOD is applied to form a nitrogen and hydrogen containing insulating material. Some SODs include a catalyst to help convert the SOD to include silicon dioxide. SODs are commercially available, such as SPINFIL® 100, available from AZ Electronic Materials USA Corp, 70 Meister Ave., Branchburg, N.J. 08876, USA.
The insulating layer 30 is infused with water, as illustrated in an exemplary embodiment in
Referring to the exemplary embodiment illustrated in
Higher dry anneal temperatures 36 tend to produce denser, higher quality silicon dioxide for the insulating layer 30, as discussed above. The insulating layer 30 may be irradiated during the dry anneal to add energy to the annealing process, and to aid in densifying the insulating layer 30 without exceeding the thermal budget. The dry anneal and irradiation of the insulating layer 30 may last from about 30 seconds to about 30 minutes in some embodiments, but different times can also be used. In an exemplary embodiment, a radiation source 38 may be used to expose the insulating layer 30 to irradiating energy during the dry anneal process. The radiation source 38 may be an ultra violet lamp in some embodiments, but the radiation source 38 may also be an infra-red lamp, a visible light lamp, a microwave source (if enough water is left in the insulating layer 30), or an electron beam source in various embodiments. The anneal time can be determined by the dry anneal temperature 36 and the intensity and type of the radiation source 38 used. In some embodiments, the upper surfaces of the insulating layer 30 may initially be densified at a faster rate than lower layers, because the upper surfaces receive more irradiating energy at first. However, the irradiating energy may pass through densified layers more easily than lower density layers, so the densification rate for lower layers may increase as the upper layers are densified. The densification process may include one or more dry anneals, and the same or different radiation sources, or no radiation source, can be used for different steps during the dry anneal.
The relatively low temperature of the dry anneal reduces the thermal cycle intensity over dry anneal processes with higher temperatures. The reduced thermal cycle intensity reduces stresses produced by different coefficients of expansion for the substrate 12 and the insulating layer 30, and this reduces stress on the walls of the trench 16. In embodiments where the trench 16 is formed between adjacent fins 14, the reduced stress reduces the likelihood of bending or breaking fins 14, such that the fins 14 are generally within about 2 degrees of vertical after the densification process. In embodiments where the trench 16 is formed in structures other than between adjacent fins 14, the reduced stress can help prevent damage or changes from differences in the coefficient of expansion between the walls of the trench 16 and the insulating layer 30.
The insulating layer 30 may be used to form a shallow trench isolation in some embodiments, as understood by those skilled in the art, but the insulating layer 30 may also be used as an insulating layer 30 between adjacent fins in finned field effect transistors FinFETS. The insulating layer 30 can also be used for other “gap fill” operations in the manufacture of an integrated circuit 10. Many additional processing steps may then be used to add components and develop the integrated circuit 10, as understood by those skilled in the art.
While at least one exemplary embodiment has been presented in the foregoing detailed description, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration of the application in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing one or more embodiments, it being understood that various changes may be made in the function and arrangement of elements described in an exemplary embodiment without departing from the scope, as set forth in the appended claims.
