TWI232592B - LOCOS Schottky barrier contact structure and its manufacturing method - Google Patents

Abstract

A LOCOS Schottky barrier contact structure of the present invention comprises a raised diffusion guard ring being surrounded by an outer LOCOS field oxide layer a recessed semiconductor substrate being surrounded by the raised diffusion guard ring, a metal silicide layer being formed over the raised diffusion guard ring and the recessed semiconductor substrate, and a patterned metal layer being formed over a portion of the outer LOCOS field oxide layer and the metal silicide layer, wherein the raised diffusion guard ring is formed between an inner LOCOS field oxide layer and the outer LOCOS field oxide layer and the recessed semiconductor substrate is formed by removing the inner LOCOS field oxide layer. The LOCOS Schottky barrier contact structure offers the raised diffusion guard ring to eliminate the junction curvature effect on the reverse breakdown voltage and the outer LOCOS field oxide layer with a much better metal step coverage.

Description

1232592 V. Description of the invention (1) [Technical field to which the invention belongs The present invention relates to a Schottky barrier diode and a method for manufacturing the same, and in particular to a local silicon oxide (LOCOS) Schottky barrier The contact structure and its manufacturing method are related. [Prior art]

A Schottky barrier diode containing at least one Schottky contact metal layer formed on a semiconductor substrate is recognized as a majority carrier diode and thus acts as a high-speed exchange diode or a high-frequency rectifier. For a Schottky screen used as a switching power diode, its main design problems are concentrated on reverse breakdown voltage (VB), reverse leakage current (IR), and forward current ( Iρ) and forward voltage (Vf).

Figure 1 shows a schematic cross-sectional view of a Schottky barrier contact structure of the prior art, in which a p + diffusion guard ring 1 0 5 is transmitted through a diffusion window formed between two forming field oxide layers 1 02 a ( (Not shown) is formed in a designed surface portion of an n- / n + epitaxial semiconductor substrate 10 1/1 00; a metal silicide layer 103 is formed as a Schottky contact metal layer system Over the P + diffusion guard ring 105 and a surface exposing an n-7 n + stupid semiconductor substrate 1 0 1/1 0 0 surrounded by a forming step glass (BSG) layer 106a; a The forming metal layer 1 0 4 a is formed on a part of the surface of the forming field oxide layer 10 2 a, the forming step glass layer 106 a and the metal oxide layer 10 3 ′, and one is Edge metal layer (not

Page 7 1232592 V. Description of the invention (2) (illustrated as an ohmic contact metal layer) is formed on the n + semiconductor substrate 100. It can be clearly seen here that the fabrication of the Schottky barrier diode shown in Figure 1 requires three mask photoresist steps, one of which is the first mask photoresist step to define the ρ + diffusion protection ring. A diffusion window; a second mask photoresist step is used to remove the forming field oxide layer 10 2a (not shown) and part of the step boro glass layer 10 6 (not shown) To form the metal silicide layer 103; and a third mask photoresist step is used to form the

形 金属 层 10 0a. Obviously, a wet etching solution (for example: buffered hydrofluoric acid) is used to remove the forming field oxide layer 1 0 2 a and the step stone glass layer 106 simultaneously without serious undercutting. It was quite difficult. Similarly, a non-isotropic dry etching method is used to remove the forming field oxide layer 1 2 a and the step boro glass layer 1 0 simultaneously without generating the ρ + guard ring and the exposed semiconductor substrate 1 0 1 / The severe groove engraving of 100 is not easy. Therefore, the width of the diffusion window using the wet etching method must be kept large (10 micrometers or more) and the junction depth of the P + diffusion guard ring 1 0 5 using the non-isotropic dry etching method must be Keep it deep (greater than or equal to 2 microns). Therefore, the size of this Schottky barrier diode cell will increase and its stray series resistance will increase by 0 for a specified breakdown voltage.

Therefore, a main object of the present invention is to provide a local silicon oxide Schottky barrier contact structure with a protruding (r a s d) diffusion protection ring to obtain a higher reverse breakdown voltage and a lower forward voltage. Another object of the present invention is to provide a local silicon oxide Schottky screen.

111 country | 11 Page 8 1232592 V. Description of the invention (3) The barrier contact structure has a better metal step coverage. A further object of the present invention is to provide a locally-oxidized Schottky barrier contact structure having a minimized diffusion guard ring area and an optimized cell area. [Summary of the Invention]

The invention discloses a local silicon oxide Schottky barrier contact structure and a manufacturing method thereof. The local silicon oxide Schottky barrier contact structure includes at least a semiconductor substrate of a first conductivity type having a lightly doped epitaxial silicon layer formed on a highly doped silicon substrate; a protrusion of a second conductivity type A diffusion guard ring is formed between an external local silicon oxide field oxide layer and an internal local silicon oxide field oxide layer; a recessed semiconductor substrate is surrounded by the convex diffusion protection ring; a metal silicide layer is formed on the outer portion A semiconductor surface surrounded by a locally oxidized silicon field oxide layer includes the protruding diffusion protection ring and the semiconductor substrate surrounded by the protruding diffusion protection ring; and a formed metal layer is formed on the external local oxidation silicon field to oxidize A part of the surface of the material layer and the metal silicide layer, wherein the internal local silicon field oxide layer is passed through a mask photoresist step after completing a diffusion process to form the protruding diffusion protection ring. Plus to remove. The local silicon oxide Schottky barrier contact structure of the present invention provides the protruding diffusion protection ring to eliminate the influence of the junction curvature effect on the reverse breakdown voltage, and the recessed semiconductor substrate to form a Schottky barrier contact to reduce

Page 9 1232592 V. Description of the invention (4) The stray series resistance and the external local silicon field oxide layer have a better metal step coverage. [Embodiment] Referring now to FIGS. 2A to 2G, the process steps for manufacturing a partially-oxidized Schottky barrier contact structure of silicon oxide according to the present invention and a schematic cross-sectional view thereof are disclosed.

FIG. 2A shows that a pad oxide layer 202 is formed on a semiconductor substrate 2 01/200 of a first conductivity type; then, a silicon nitride layer 2 0 3 is formed on the pad oxide layer. 2 0 2 above. The pad oxide layer 2 0 2 is a thermal silicon dioxide layer grown on the semiconductor substrate 2 0 1/2 0 0 in a dry oxygen environment and has a thickness between 100 angstroms and 50 angstroms. . The silicon nitride layer 230 is formed by a low pressure chemical vapor deposition (LPCVD) method, and its thickness is between 500 angstroms and 150 angstroms. The semiconductor substrate 2 0 1/2 0 0 comprises at least a lightly doped epitaxial silicon layer 2 0 1 on a highly doped silicon substrate 2 0 0, wherein the lightly doped epitaxial silicon layer 2 0 1 The dopant concentration is between 1 014 / cm3 and 1017 / cm3 and the thickness of the epitaxial layer is between 3 microns and 35 microns, which is determined by the specified breakdown voltage; The dopant concentration of the doped semiconductor substrate 2000 is between 1 019 / cm3 and 5 X 102G / cm3, and its thickness is determined according to the size of the wafer. Figure 2B shows a first step photoresist (PR1) step (not shown) used

Page 10, 1232592 5. Description of the invention (5) ^^-To pattern the nitride nitride layer 203, the silicon nitride layer 203 in one of the protection ring regions uses an anisotropic dry type #etching method. To remove, and the formed (pa 11 erned) nitride nitride layer 2 0 3 a of the protection ring area is shown in FIG. 2C, the pad located outside the formed silicon nitride layer 2 0 3 a The oxygen layer 202 is removed by using buffered hydrofluoric acid or diluted hydrofluoric acid; then, a partial oxidation of silicon (LOCOS) process is performed in a steam or wet oxygen environment to form An internal partial oxidation; ^ Xi J ^ two compound layer 2 0 4 b and an external local oxide silicon field oxide layer 2 0 4 a. The thickness of the 3 / external localized silicon field oxide layer 2 0 4 b / 2 0 4 a is between 60,000 angstroms and 1,000 angstroms, and the oxidation temperature is between 丨 〇 〇〇 and 丨 2 C. It is worth noting here that the local silicon oxide process does not need to remove the pad oxide layer 202 other than the shaped silicon nitride layer 203a to perform rod oxidation. τ Figure 1D shows that the formed nitrided layer 203a is added and removed by hot-filled acid or anisotropic dry-etching method. ^ Figure 2E shows ion implantation in an automatic alignment method. A second conductivity type dopant is exaggerated over the forming pad oxide layer 202a and is implanted on the semiconductor substrate 2 0 1/2 0 0 Within a surface portion of the substrate; then, an impurity drive-in process is performed to form a protruding diffusion protection ring 205a; then, the hafnium oxide layer 202a is added with diluted hydrofluoric acid or buffered hydrofluoric acid. Pre-removal 'and the external / internal local silicon oxide field oxide layer 204a / 204b is also etched at the same time; after that, a second mask photoresist (p R 2) step is performed on the external local silicon oxide Field oxide layer 2 0 4 a and the protruding diffusion protection ring 2 0 5 a

1232592 V. Part of the description of the invention (6) is covered by the surface. It is worth noting here that a 埶 j, a liquid source, a solid source, or a gaseous source can be used to plant 2 Λ ... It is worth highlighting here that the protruding diffusion protection ring constraint is equal to the external / internal local silicon oxide The level of one of the bottom surfaces of the field emulsion layer 20 4a / 20 4b. The protruding guard ring 2 0 5 a may be a highly doped diffusion guard ring, a moderately doped (moderate 1 y-doped) diffusion guard ring, or a highly doped diffusion guard ring formed in a moderately doped diffusion guard ring. Within the protection ring. FIG. 2F shows that the internal local silicon field oxide layer 204b is buffered and removed by hydrofluoric acid; then, the second mask photoresist is removed, and then a semiconductor substrate cleaning process is performed; then, a The lithium oxide layer 2 0 6 a is formed on an exposed silicon surface by a conventional self-aligning lithography (se 1 ^ a & 1 丨 η ”silicidation) process. Δ 蒦 ring 2 0 5 a and a recessed semiconductor substrate surrounded by the protruding diffusion protection ring 2 0 $ a. The metallization = 206a is a refractory metallization layer , Such as · Ni Si (Ni Si 2), Shi Xihua Gu (C0Si 2), Shi Xihua titanium (Ti S i 2), Shi Xi 4 Shi Xi (MoSi2), silicidation Button (TaSi2), platinum silicide (ptSi22), dagger steel (PdSi2) or tungsten silicide (WSi2), etc. 2 metal layers of this metal layer; Figure 2G shows a shaped metal layer 2 0 7a series oxidation A part of the surface of the silicon field oxide layer 2 0 4 a and 206 a is formed by a third mask photoresist (PR3). The formed metal layer 207 a Containing at least over a barrier metal (barrier metal) layer

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1232592 V. Description of the invention (7) Less aluminum (A1), silver (Ag) or gold (Au). The barrier metal layer includes at least one refractory metal layer or one refractory metal nitride layer. It is worth noting here that the highly doped silicon substrate 200 is ground (not shown) to a predetermined thickness to reduce stray series resistance; then, a back ohmic contact is formed (not shown) . Based on this, the characteristics and advantages of the local silicon oxide Schottky barrier contact structure of the present invention can be summarized as follows: (a) The local silicon oxide Schottky barrier contact structure of the present invention can provide a protruding diffusion protection ring to eliminate Or reduce the effect of the curvature of the junction on the reverse breakdown voltage, so a higher reverse breakdown voltage can be easily obtained. (b) The local silicon oxide Schottky barrier contact structure of the present invention provides a recessed semiconductor substrate surrounded by the protruding diffusion protection ring to form a Schottky barrier metal contact to reduce a known reverse breakdown voltage by the The stray series resistance generated by the lightly doped epitaxial silicon layer, so a smaller forward voltage under a known forward current can be obtained without increasing the cell area. (c) The local silicon oxide Schottky barrier contact structure of the present invention has an external local silicon oxide field oxide layer and an internal local silicon oxide field oxide layer removed to provide a better metal step coverage.

Page 131232595. Description of the invention (8) (d) The local silicon oxide Schottky barrier contact structure of the present invention can provide a smaller size under the known reverse breakdown voltage, forward voltage and forward current. The cell area has a reduced protruding diffusion protection ring and an optimized Schottky barrier contact area. Although the present invention is particularly illustrated and described with reference to the attached examples or connotations, it is only a representative statement and not a limitation. Furthermore, the present invention is not limited to the listed details. Those skilled in the art can also understand that changes of various shapes or details can be made without departing from the true spirit and scope of the present invention, but also belong to the present invention. Invented Fan Bee.

Page 14 1232592 Brief Description of Drawings Figure 1 shows a schematic cross-sectional view of a prior art Schottky barrier contact structure with a diffusion guard ring. FIG. 2A to FIG. 2G show the manufacturing steps and a schematic cross-sectional view of the method for fabricating a local silicon oxide Schottky barrier contact structure of the present invention. Representative drawing number description: 2 0 0 highly doped semiconductor substrate 201 lightly doped epitaxial semiconductor layer 2 0 2 pad oxide layer 2 0 2a forming pad oxide layer 2 0 3 silicon nitride layer 2 0 3 a forming nitride Silicon layer 2 0 4a External partial oxide field oxide layer 2 0 4b Internal partial oxide field oxide layer 2 0 5 a Protruding diffusion protection ring 2 0 6 High temperature resistant metal layer 206a Metal silicide layer 207 Metal layer 207a Forming Metal layer

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Claims (1)

1232592 VI. Scope of patent application 1. A local silicon oxide Schottky barrier contact structure including at least: a semiconductor substrate of a first conductivity type, wherein the semiconductor substrate includes at least a lightly doped epitaxial silicon layer formed on a high Doped silicon substrate; a protruding diffusion protection ring of a second conductivity type is formed between an external local silicon oxide field oxide layer and an internal local silicon oxide field oxide layer, wherein the internal local silicon oxide field oxide layer The oxide layer is removed to form a recessed semiconductor substrate surrounded by the protruding diffusion protection ring; a metal silicide layer is formed on the protruding diffusion protection ring surrounded by the external local silicon field oxide layer And on the recessed semiconductor substrate surrounded by the protruding diffusion protection ring; and a forming metal layer is formed on a part of the surface of the external partial silicon field oxide layer and the metal oxide layer. 2. The local silicon oxide Schottky barrier contact structure described in item 1 of the scope of the patent application, wherein the external and internal local silicon oxide field oxide layers are processed by a local silicon oxide (LOC0S) in a water vapor or A wet oxygen environment is formed. 3. The locally oxidized Schottky barrier contact structure according to item 1 of the scope of patent application, wherein the protruding diffusion guard ring includes at least one highly doped diffusion guard ring, a moderately doped diffusion guard ring, or a A highly doped diffusion guard ring is formed within a moderately doped diffusion guard ring. 1232592 6. Scope of patent application 4. The local silicon oxide Schottky barrier contact structure described in item 1 of the scope of patent application, wherein the above-mentioned protruding diffusion protection ring system uses ion implantation in an automatic alignment manner to mix the dopant Impurities are formed across a pad oxide layer between the outer local silicon oxide field oxide layer and the inner local silicon oxide field oxide layer. 5. The locally oxidized Schottky barrier contact structure described in item 1 of the scope of the patent application, wherein the above-mentioned protruding diffusion protection ring system is in an automatically aligned manner by a liquid source, a solid source or a gaseous state. A source of a thermal diffusion process is formed through a diffusion window between the outer local silicon oxide field oxide layer and the inner local silicon oxide field oxide layer. 6. The locally oxidized Schottky barrier contact structure described in item 1 of the scope of the patent application, wherein the above-mentioned metal silicide layer includes at least a high-temperature-resistant metal silicide layer formed by an automatic alignment silicidation process. 7. The local silicon oxide Schottky barrier contact structure described in item 1 of the scope of the patent application, wherein the above-mentioned formed metal layer includes at least one metal layer on top of a barrier metal layer. 8. A local silicon oxide Schottky barrier contact structure, comprising at least: a semiconductor substrate of a first conductivity type, wherein the semiconductor substrate includes at least one lightly doped epitaxial silicon layer formed on a highly doped silicon substrate ; Page 171232592 6. Scope of patent application A protective ring is formed between an external local silicon oxide field oxide layer and an internal local silicon oxide field oxide layer by a local silicon oxide (LOCOS) process, wherein the protective ring It is doped with ion implantation in an automatic alignment manner to form a protruding diffusion protection ring of a second conductivity type; a recessed semiconductor substrate is formed by removing the internal local silicon field oxide layer; A high temperature resistant metal silicide layer is formed on the protruding diffusion protection ring surrounded by the external local silicon field oxide layer and the recessed semiconductor substrate surrounded by the protruding diffusion protection ring; and a formed metal A layer is formed on a part of the surface of the outer local silicon oxide field oxide layer and the high temperature resistant metal silicide layer. 9. The local silicon oxide Schottky barrier contact structure as described in item 8 of the scope of patent application, wherein the lightly doped epitaxial silicon layer has a dopant concentration between 1014 / cm3 and 1017 / cm3. And a thickness between 3 microns and 35 microns. I 0. The local silicon oxide Schottky barrier contact structure described in item 8 of the scope of the patent application, wherein the external and internal local silicon field oxide layers are formed by the local silicon oxide (LOCOS) process. A water vapor or wet oxygen environment grows to a thickness between 60 and 100 angstroms. II. The local silicon oxide Schottky barrier connection as described in item 8 of the scope of patent application Page 18, 1232592 6. The patent application scope touch structure, in which the protruding diffusion protection ring is a highly doped diffusion protection ring, a moderately doped diffusion protection ring or a highly doped diffusion protection ring formed in a medium Doped inside the diffusion guard ring. 1 2. The local silicon oxide Schottky barrier contact structure as described in item 8 of the scope of patent application, wherein the above-mentioned high temperature resistant metal silicide layer is formed by an auto-aligned silicidation process. 1 3. The local silicon oxide Schottky barrier contact structure according to item 8 of the scope of the patent application, wherein the above-mentioned formed metal layer includes at least one metal layer and is placed on an obstacle metal layer. 1 4. A locally-oxidized Schottky barrier contact structure including at least: a semiconductor substrate of a first conductivity type, wherein the semiconductor substrate includes at least a lightly doped epitaxial silicon layer formed on a highly doped silicon substrate on; A guard ring is formed between an external local silicon oxide field oxide layer and an internal local silicon oxide field oxide layer by a local silicon oxide (LOCOS) process under a water vapor or wet oxygen environment. The protective ring It is doped by a thermal diffusion process in an automatic alignment manner to form a protruding diffusion protection ring of a second conductivity type; a recessed semiconductor substrate is formed by removing the internal local silicon field oxide layer; A high temperature resistant metal silicide layer is formed from the external local silicon oxide Page 19, 1232592 6. The range of patent application: the protruding diffusion protection ring surrounded by the field oxide layer and the recessed semiconductor substrate surrounded by the protruding diffusion protection ring, wherein the high temperature resistant metal silicide layer is used An automatic alignment silicidation process is used to form it; and a forming metal layer is formed on a part of the surface of the external local silicon field oxide layer and the high temperature resistant metal silicide layer. 15. The local silicon oxide Schottky barrier contact structure described in item 14 of the scope of the patent application, wherein the external and internal local silicon field oxide layer has a thickness between 6 0 0 0 angstroms and 10 0 0 0 Angstroms. 16. The locally-oxidized Schottky barrier contact structure described in item 14 of the scope of patent application, wherein the thermal diffusion process includes at least a high-temperature doping process using a liquid source, a solid source, or a gaseous source. 17. The local silicon oxide Schottky barrier contact structure as described in item 14 of the scope of the patent application, wherein the protection ring described above places a nitrided layer on a frame through a first mask photoresist step. (Pad) is defined by preforming on the oxide layer. 18. The local silicon oxide Schottky barrier contact structure described in item 14 of the scope of patent application, wherein the internal silicon oxide field oxide layer described above uses a second mask photoresist after doping the protection ring. Steps to add removal. Page 20, 1232592 6. Scope of patent application 19. The local silicon oxide Schottky barrier contact structure described in item 14 of the scope of patent application, wherein the above-mentioned formed metal layer contains at least one silver (Ag), aluminum (A1) Or an Au layer is placed on top of a barrier metal layer and formed using a third mask photoresist step. 20. The local silicon oxide Schottky barrier contact structure as described in item 14 of the scope of the patent application, wherein the above-mentioned high-temperature metal petroxide layer at least comprises nickel petrochemical (NiSi2), cobalt silicide (CoSi2), Choose one of titanium silicide (TiSi2), molybdenum silicide (MoSi2), tantalum silicide (TaSi2), platinum silicide (PtSi2), palladium silicide (PdSi2), and tungsten silicide (WSi2). Page 21