International Business Machines Corporation

Jacob Riseman

Irving T Ho

Seiki Ogura

Nivo Rovedo

William A Pliskin

Joseph F Shepard

Harsaran S Bhatia

Paul J Tsang

Klaus D Beyer

Narasipur G Anantha

Anthony J Dally

Eric Mendel

Satyapal S Bhatia

Emmanuel A Valsamakis

Karen A Nummy

William L Guthrie

William J Patrick

Karanam Balasubramanyam

Ronald N Schulz

Wei-Kan Chu

Paul M Schaible

Charles L Standley

Stanley R Makarewicz

James S Makris

Kathleen A Perry

A method is disclosed for producing coplanar metal/insulator films on a substrate according to a chem-mech polishing technique. In one example, a substrate having a patterned insulating layer of dielectric material thereon, is coated with a layer of metal. The substrate is then placed in a parallel polisher and the metal is removed elsewhere except in the holes where it is left intact. This is made possible through the use of an improved selective slurry which removes the metal much faster than the dielectric material. The insulating layer may then be used as an automatic etch stop barrier. In a second example a substrate having a patterned metallic layer is coated with an insulating layer and then subjected to chem-mech polishing. The structure is coplanarized by the chem-mech removal of the insulating material from the high points of the structure at a faster rate than from the lower points. Optional etch stop layers also may be used.

Chem-mech polishing method for producing coplanar metal/insulator films

A method for forming fully recessed (planar) isolation regions on a semiconductor for the manufacture of CMOS integrated circuits, and the resulting semiconductor structure, comprising in a P doped silicon substrate with mesas formed therein, forming low viscosity sidewall spacers of borosilicate glass in contact with the sidewalls of those mesas designated to have N-channel devices formed therein; then filling the trenches in the substrate adjacent to the mesas with TEOS; and heating the structure until the boron in the sidewall spacers diffuses into the sidewalls of the designated mesas to form channel stops. These sidewall spacers reduce the occurrence of cracks in the TEOS by relieving internal mechanical stress therein and permit the formation of channel stops via diffusion, thereby permitting mesa walls to be substantially vertical.

Sidewall spacers for CMOS circuit stress relief/isolation and method for

A method and resulting structure for making contact to a narrow width PN junction region in any desired semiconductor body is described. A substantially vertical conformal conductive layer is formed over the desired PN junction region. The body is heated at a suitable temperature to cause a dopant to diffuse from the vertical conductive layer into the semiconductor body to form the narrow width PN junction region. A substantially horizontal conductive layer makes contact to the substantially vertical layer so as to have the horizontal conductive layer in electrical contact to the PN junction region. Electrical contact can be made to the horizontal conductive layer at any convenient location. A lateral PNP transistor is one type of very small device that can be made using the method of the present invention.

Structure for contacting a narrow width PN junction region

Disclosed is a process of forming high density, planar, single- or multi-level wiring for a semiconductor integrated circuit chip. On the chip surface is provided a dual layer of an insulator and hardened photoresist having various sized openings (grooves for wiring and openings for contacts) therein in a pattern of the desired wiring. A conductive (e.g., metal) layer of a thickness equal to that of the insulator is deposited filling the grooves and contact openings. A sacrificial dual (lower and upper component) layer of (hardened) photoresist is formed filling the metal valleys and obtaining a substantially planar surface. The lower component layer is thin and conformal and has a higher etch rate than the upper component layer which is thick and nonconformal. By reactive ion etching the sacrificial layer is removed leaving resist plugs in the metal valleys. Using the plug as etch masks, the exposed metal is removed followed by removal of the remaining hardened photoresist layer and the plugs leaving a metal pattern coplanar with the insulator layer. This sequence of steps is repeated for multilevel wiring. When only narrow wiring is desired, a single photoresist layer is substituted for the dual photoresist sacrificial layer.

Process for forming planar chip-level wiring

A chemical-mechanical (chem-mech) method for removing SiO.sub.2 protuberances at the surface of a silicon chip, such protuberances including 'bird's heads'. A thin etch stop layer of Si.sub.3 N.sub.4 is deposited onto the wafer surface, which is then chem-mech polished with a SiO.sub.2 water based slurry. The Si.sub.3 N.sub.4 acts as a polishing or etch stop barrier layer only on the planar portions of the wafer surface. The portions of the Si.sub.3 N.sub.4 layer located on the top and at the sidewalls of the 'bird's heads' and the underlying SiO.sub.2 protuberances are removed to provide a substantially planar integrated structure.

Method for removing protuberances at the surface of a semiconductor

In the process of sidewall image transfer, a vertical step is etched in some material and then a conformal layer of some other material is deposited over the step. By reactive ion etching the conformal material can be anisotropically etched which results in a sidewall spacer of the second material on the vertical surfaces of the step material. By removing the step material, the free standing spacer can then be used as a mask. One area in which improvement is desired is in the selectivity of the etch of the spacer to the material immediately below it. Because of the limited number of materials and reactive ion etching gases it is difficult to avoid an etch in the underlying layer as the sidewall spacer is formed. A suitable etch stop is employed beneath the step material to avoid the problem. Because of the usual technology, the spacer material is plasma deposited silicon nitride and the step material is photoresist. Polysilicon, aluminum or similar metal is employed as an etch stop, since it is not by a CF.sub.4 based gas which is used to form the spacer.

Method of preventing asymmetric etching of lines in sub-micrometer range

An integrated circuit structure which includes small area lateral bipolar and method for making the same is described. A semiconductor body, such as a monocrystalline silicon wafer, having surface regions thereof isolated from other such regions by a pattern of dielectric isolation is provided. At least two narrow widths PN junction regions are located within at least one of the surface regions. Each PN junction has a width dimension substantially that of its electrical contact. Substantially vertical conformal conductive layers electrically ohmic contact each of the PN junction regions. The PN junction regions are the emitter and collector regions for a lateral bipolar transistor. A base PN junction base region of an opposite conductivity is located between and contiguous to the emitter and the collector junctions. Substantially horizontal conductive layers are in electrical contact with an edge of each of the vertical conductive layers and separated from the surface regions by a first electrical insulating layer. A second insulating layer covers the conformal conductive layers. The horizontal conductive layer is patterned so as to have electrically separated conductive lines from one another. A third electrical insulating layer is located over the patterned horizontal conductive layers. An electrical ohmic contact is made to each of the horizontal conductive layers through an opening in the third electrical insulating layer which effectively makes electrical contacts to the emitter and collector regions through the patterned horizontal conductive layers and the vertical conductive layers. An electrical ohmic contact is made to the centrally located base region which contact is separated from the vertical conductive layers by the second insulating layer.

Self-aligned lateral bipolar transistors

The lateral transistor is described which has both its base width and the emitter region of the transistor minimized. This minimization of the elements of the lateral transistor gives high performance. The lateral transistor which may be typically PNP transistor is formed in a monocrystalline semiconductor body having a buried N+ region within the body. A P type emitter region is located in the body. An N type base region is located around the side periphery of the emitter region. A P type collector region is located in the body surrounding the periphery of the base region. A first P+ polycrystalline silicon layer acting as an emitter contact for the emitter region is in physical and electrical contact with the emitter region and acts as its electrical contact. A second P+ polycrystalline silicon layer is located on the surface of the body to make physical and electrical contact with the collector region. A vertical insulator layer on the edge of the second polycrystalline silicon layer isolates the two polycrystalline silicon layers from one another. The N base region at its surface is located underneath the width of the vertical insulator layer. An N+ reach-through region extending from the surface of the body to the buried N+ region acts as an electrical contact through the N+ region layer to the base region. The width of the vertical insulator has a width which is equal to the desired base width of the lateral PNP transistor plus lateral diffusions of the collector and emitter junctions of the lateral PNP. The preferred structure is to have the emitter formed around the periphery of a channel or groove which has at its base an insulating layer such as silicon dioxide. The parasitic transistor is almost totally eliminated by this buried oxide isolation.

Fabrication methods for high performance lateral bipolar transistors

A semiconductor body having surface regions thereof isolated from other such regions by a pattern of dielectric isolation is provided. At least two narrow widths PN junction regions are located within at least one of the surface regions. Each PN junction has a width dimension substantially that of its electrical contact. Substantially vertical conformal conductive layers electrically ohmic contact each of the PN junction regions. The PN junction regions are the emitter and collector regions for a lateral bipolar transistor. A base PN junction region of an opposite conductivity is located between and contiguous to the emitter and the collector junctions. Substantially horizontal conductive layers are in electrical contact with an edge of each of the vertical conductive layers and separated from the surface regions by a first electrical insulating layer. A second insulating layer covers the conformal conductive layers. The horizontal conductive layer is patterned so as to have electrically separated conductive lines from one another. A third electrical insulating layer is located over the patterned horizontal conductive layers. An electrical contact is made to each of the horizontal conductive layers through an opening in the third electrical insulating layer which effectively makes contacts to the emitter and collector regions through the patterned horizontal conductive layers and the vertical conductive layers. An ohmic contact is made to the base region which is separated from the vertical conductive layers by the second insulating layer.

Method for making self-aligned lateral bipolar transistors

The lateral transistor is described which has both its base width and the emitter region of the transistor minimized. This minimization of the elements of the lateral transistor gives high performance. The lateral transistor which may be typically PNP transistor is formed in a monocrystalline semiconductor body having a buried N+ region within the body. A P type emitter region is located in the body. An N type base region is located around the side periphery of the emitter region. A P type collector region is located in the body surrounding the periphery of the base region. A first P+ polycrystalline silicon layer acting as an emitter contact for the emitter region is in physical and electrical contact with the emitter region and acts as its electrical contact. A second P+ polycrystalline silicon layer is located on the surface of the body to make physical and electrical contact with the collector region. A vertical insulator layer on the edge of the second polycrystalline silicon layer isolates the two polycrystalline silicon layers from one another. The N base region at its surface is located underneath the width of the vertical insulator layer. An N+ reach-through region extending from the surface of the body to the buried N+ region acts as an electrical contact through the N+ buried layer to the base region. The width of the vertical insulator has a width which is equal to the desired base width of the lateral PNP transistor plus lateral diffusions of the collector and emitter junctions of the lateral PNP. The preferred structure is to have the emitter formed around the periphery of a channel or groove which has at its base a insulating layer such as silicon dioxide. The parasitic transistor is almost totally eliminated by this buried oxide isolation.

Deep dielectric isolation zones in a substrate are achieved by forming trenches using reactive ion etching. A glass having a coefficient of thermal expansion closely matching that of the substrate is deposited onto the trench to entirely or partially fill the trench. Deposition can be by sedimentation, centrifugation or spin-on techniques. The structure is then fired until the glass particles fuse into a continuous glass layer and final smoothing if necessary can be accomplished.

Deep dielectric isolation by fused glass

A metal silicide contact to silicon devices which has broad application to almost all of the variety of silicon semiconductor devices is described. This contact with a substantial side component has particular advantage as the base contact for a bipolar transistor. However, contacts can be made to regions of any desired device regions with a variety of P+, N+, P, N, P-, N- and so forth conductivity types. Further, the contact can be an ohmic or Schottky contact.

Method of making integrated circuits using metal silicide contacts

A method for making contact to a narrow width PN junction region in any desired semiconductor body is described. A substantially vertical conformal conductive layer is formed over the desired PN junction region. The body is heated at a suitable temperature to cause a dopant to diffuse from the vertical conductive layer into the semiconductor body to form the narrow width PN junction region. A substantially horizontal conductive layer makes contact to the substantially vertical layer so as to have the horizontal conductive layer in electrical contact to the PN junction region. Electrical contact can be made to the horizontal conductive layer at any convenient location. A lateral PNP transistor is one type of very small device that can be made using the method of the present invention.

Method for contacting a narrow width PN junction region

A method is described for forming the recessed dielectric isolation in a silicon substrate involves first forming trenches which may be less than about 1 micron in depth in areas of one principal surface of the silicon substrate where isolation is desired. Where, for example, an NPN bipolar transistor structure is planned to be formed it is usually necessary to have a P+ region underneath the recessed dielectric isolation to allow full isolation between the various bipolar transistor devices. A PNP transistor uses an N+ region underneath the isolation. Where a field effect transistor is planned a channel stop can be substituted for the P+ region. Under the circumstance of bipolar devices, the P+ region is formed in the substrate prior to the deposition of an epitaxial layer thereover. The trench formation is caused to be formed through the epitaxial layer and into the P+ regions therein. The surface of the trenches are then oxidized in an oxidizing ambient to form a silicon dioxide layer thereon. A glass is deposited over this principal surface. The glass used has a thermal coefficient of expansion that approximates that of silicon and has a softening temperature of less than about 1200.degree. C. The structure is then heated to a temperature that allows the flow of the deposited glass on the surface so as to fill the trenches. The glass on the principal surface above the trench can be removed by a reactive ion etching method. Alternatively and preferably, the glass is removed from areas other than the immediate area of the trench by lithography and etching techniques followed by a second heating of the structure to cause the glass flow to result in surface planarization.

Method for forming recessed isolated regions

A method is given for forming a planarized integrated circuit structure just prior to the formation of metallurgy interconnection lines on the integrated circuit. The method begins with the integrated circuit intermediate product having devices formed therein but before interconnection metallurgy has been formed on the principal surface of the product. A glass layer is deposited in a non-conformal way onto the principal surface of the integrated circuit. The glass is chosen to have a thermal coefficient of expansion that approximates that silicon and has a softening temperature of less than about 1200.degree. C. The thermal coefficient of expansion approximates that of silicon to reduce stress problems in the integrated circuit structure. The relatively low softening temperature is required for the next step of heating the structure to cause the flow of glass on the surface of the integrated circuit product to fill in the irregularities therein and to thereby planarize the integrated circuit surface. Openings are then formed through the glass down to the device elements of the integrated circuit. The interconnection metallurgy is formed over the surface of the glass and through the openings of the glass to interconnect the device elements of the integrated circuit. The glass may be deposited by various methods which include the sedimentation methods of spraying, centrifuging and spin-on plus sputtering or evaporation methods.

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Poughkeepsie, NY, United States of America

Jacob Riseman