Metallization of semiconductor wafers

Abstract

The present invention relates to a method for manufacturing a semiconductor wafer, comprising the steps of: i) applying a MOD ink composition to a semiconductor wafer, thereby forming a precursor layer; and ii) curing the precursor layer. In one embodiment, the application in step i) is performed by inkjet printing. Inkjet printing of the MOD ink offers low equipment cost, low power consumption, no material waste, print-on-demand, and easy selective deposition / design flexibility (no etching required). Additionally, the method of the present invention improves the adhesion and conductivity of metallization layers on the backside of the wafer.

Description

[Technical Field]

[0001] This invention relates to a method for manufacturing semiconductor wafers. In particular, this invention relates to a method for manufacturing semiconductor wafers by metallizing semiconductor wafers.

[0002] During the manufacturing of semiconductor devices, it is usually necessary to metallize semiconductor wafers. A metallization scheme should typically meet the following requirements: First, layers directly placed on the wafer should be bonded to the wafer. Second, the outer surface of the metallization structure should be solderable so that the semiconductor device can be bonded to a lead frame or the like. Third, the metallization structure itself should be crack-free. In addition, metallization requires effective stress control of the stack to reduce further wafer warping, and low ohmic contact resistance and good adhesion are also important requirements for the metallization process.

[0003] Conventional methods for wafer metallization are sputtering / deposition, and typically multiple stacked layers such as Ti / Ni / Ag, Al / Ti / NiV / Ag, or Ti / Au are used.

[0004] For example, U.S. Patent No. 4,946,376 discloses a metallization scheme for a semiconductor device comprising a vanadium layer having a thickness of 500 to 3,000 Å placed on the back surface of a wafer, and a silver layer having a thickness of 10,000 to 20,000 Å placed on the vanadium layer, wherein the vanadium layer and the silver layer are applied by vapor deposition or sputtering.

[0005] U.S. Patent No. 6,790,709 (B2) discloses a microelectronic device and a method for manufacturing the same. The microelectronic device comprises a microelectronic die having an active surface, a back surface, and at least one side surface, the microelectronic die comprising a slanted sidewall and a channel sidewall, and a metallization layer disposed on the back surface and the slanted sidewall of the microelectronic die. The metallization layer can be formed by any method known in the art, including but not limited to chemical vapor deposition, sputtering deposition (PVD), and electroplating, preferably by sputtering deposition.

[0006] U.S. Patent Application Publication 2008 / 0083611(A1) discloses a method for improving adhesion between a wafer and a deposited metal film. This method involves colliding metal ions with a deposited film at a temperature below 200°C, where the energy of the metal ions is high enough to achieve interfacial mixing between the metal atoms and wafer atoms, and low enough to prevent stress damage to the wafer. The deposited film in this literature is manufactured by sputtering.

[0007] The main drawbacks of the conventional technology described above are the high equipment cost, low material utilization rate, and the need for additional hardware (shielding / masking) to accommodate variations in wafer size (e.g., 200mm to 300mm).

[0008] In addition, the conventional technology also discloses a method of metallization using printing technology.

[0009] For example, U.S. Patent No. 10763230(B2) discloses a method for back-side metallizing an integrated circuit, comprising the steps of forming a wet layer by inkjet printing a pattern of nanosilver particle conductive ink onto a first surface of a silicon wafer, and then curing the wet layer by heating the wafer in an oven to evaporate the solvent and other materials in the ink.

[0010] International Publication No. 2020 / 094583(A1) discloses a method for manufacturing a semiconductor package at least partially covered with an electromagnetic interference shielding layer, the method comprising at least the steps of: i. providing a semiconductor package and an ink composition, the ink composition comprising at least the following components: a) a compound comprising at least one metal precursor and b) at least one organic compound; ii. applying at least a portion of the ink composition to the semiconductor package to form a precursor layer; and iii. treating the precursor layer with electromagnetic radiation having a peak wavelength in the range of 100 nm to 1 mm. In this method, the ink composition is applied to the semiconductor package, i.e., epoxy, rather than the silicon wafer itself, for the purpose of providing an electromagnetic interference shielding layer rather than metallizing the wafer.

[0011] Conventional metallization techniques using printing have several drawbacks, and the adhesion and conductivity of the metallization layer still require further improvement. [Overview of the Initiative]

[0012] The object of the present invention is to overcome the shortcomings of the prior art and to provide a method for manufacturing semiconductor wafers, particularly a method for manufacturing semiconductor wafers by metallizing semiconductor wafers, wherein the resulting metallized layer has improved adhesion and conductivity.

[0013] Specifically, the object of the present invention is a method for manufacturing semiconductor wafers, i) A step of applying a MOD ink (Metal-Organic Decomposition ink) composition to a semiconductor wafer to form a precursor layer, ii) To provide a method comprising the step of curing a precursor layer.

[0014] Another object of the present invention is to provide a semiconductor wafer obtained by the method of the present invention.

[0015] A further object of the present invention is to provide a semiconductor device comprising the semiconductor wafer of the present invention.

[0016] A further object of the present invention is to provide a semiconductor wafer precursor comprising a) a semiconductor wafer and b) an uncured MOD ink layer. [Modes for carrying out the invention]

[0017] In one aspect of the present invention, the present invention is a method for manufacturing a semiconductor wafer, i) A step of applying the MOD ink composition to a semiconductor wafer to form a precursor layer, ii) A method comprising the step of curing a precursor layer is provided.

[0018] The method of the present invention enables metallization of the back surface and / or front surface of a semiconductor wafer, preferably the back surface. The metal used may be Ag, Ag / Sn, or Au. The thickness of the resulting metallization layer may be determined as desired, for example, about 100 nm to about 3000 nm, preferably about 300 nm to about 2000 nm, and particularly preferably about 300 nm to about 1000 nm. The resulting metallization layer has good electrical and thermal conductivity and good solderability to externally attached materials.

[0019] The semiconductor wafer may be a Si wafer, SiC wafer, GaN wafer, GaAs wafer, or Ga2O3 wafer, preferably a Si wafer. The semiconductor wafer may also be a power electronics wafer or a logic IC wafer.

[0020] Step i) In one embodiment of the present invention, the application in step i) is carried out by spraying, spin coating, dip coating, or inkjet printing, preferably by inkjet printing.

[0021] Inkjet printing is a layer forming process that reduces material waste and does not require masks or etching steps. Further, inkjet printing can handle large wafers (e.g., 300 mm wafers), thereby reducing the need for expensive metal deposition equipment for such wafers and thus reducing manufacturing costs.

[0022] Inkjet printing can be performed in a patterned manner. Inkjet printing can be performed by any type of inkjet printer, such as a piezoelectric inkjet printer. The number of layers applied by inkjet printing can be one or more layers, preferably 1 to 10 layers, to obtain a desired layer thickness. The layer thickness of inkjet printing can be adjusted by adjusting the printing resolution and the number of layers. The DPI range X / Y of inkjet printing can be 300 to 3000.

[0023] The MOD ink composition used in the present invention includes a metal precursor compound to be applied and a solvent. In order to form a film of the metal to be applied (especially silver), the organic solvent needs to be removed so that the metal precursor compound can be converted into a solid structure by a decomposition reaction.

[0024] However, during the removal of the solvent, especially when the film is thick, bubbles may be formed inside or on the surface, which ultimately results in a film having a high porosity. Therefore, MOD ink has conventionally been considered suitable only for the preparation of thin films, otherwise quality problems may occur. Further, metal films prepared by MOD ink are considered to have inferior adhesion to the substrate compared to those prepared by other methods such as CVD or PVD. The only way to reduce the bubble density is considered to be to slowly remove the solvent by simply changing the heating rate. Therefore, this method is too slow to be applied to the modern semiconductor industry.

[0025] As a result, MOD inks are currently used only in the semiconductor industry, for example, to fabricate circuits (i.e., create conductive paths) on polyimide (PI) or polyethylene terephthalate (PET) in flexible printed circuit (FPC) applications. In these applications, the metal layer should be thin and uniform and should be used in relatively favorable environments. In other applications, such as back-side metallization, MOD inks are considered unsuitable because the back-side metallization layer should be relatively thick and strong to ensure good adhesion to the wafer so that the metallization layer does not peel off when the temperature changes significantly or when high current densities occur frequently.

[0026] However, surprisingly, it has been found that when MOD ink is used in the method of the present invention, a thick, dense layer with low porosity can be obtained quickly in a single application and curing cycle by completely curing it in the curing step after application (referred to as the application and curing cycle). On the other hand, it is also possible to perform multiple application and curing cycles, forming a layer with a thickness of 100 nm to 800 nm, preferably 150 nm to 500 nm, more preferably 200 nm to 300 nm, in each cycle, thus enabling the rapid acquisition of a thick, dense layer with low porosity and large grain size (up to 1000 nm). The resulting layer has good adhesion and conductivity, thus enabling the use of MOD ink for backside metallization of wafers and thus overcoming the biases of the prior art. The layer obtained by the method of the present invention using MOD ink has a porosity equivalent to or smaller than that of the PVD method.

[0027] One of the advantages of MOD inks over other inks, such as nanoparticle inks, is their ability to form more uniform, flatter, and denser films. Layers obtained with inks containing metal nanoparticles are typically very sparse, i.e., have high porosity. In contrast, layers obtained by the method of the present invention using MOD inks have much lower porosity. Unlike nanoparticle inks, MOD inks are solutions rather than mixtures (suspensions), do not settle over time, and are less prone to problems during application (e.g., less likely to clog nozzles). The viscosity of MOD inks can be easily adjusted to control atomization and annealing temperature. In addition, MOD inks are environmentally friendly, do not contain nanoparticles, are more readily available, and may ultimately be cheaper than nanoparticle inks.

[0028] The MOD ink composition used in the present invention comprises the following components: a) at least one metal precursor, and b) a solvent.

[0029] The metals in the MOD ink composition are Ag, Ag / Sn, or Au.

[0030] The metal precursor has a decomposition temperature of 80°C to 500°C, for example, 80°C to 500°C, or 150°C to 500°C, or 180°C to 350°C, or 150°C to 300°C, or 180°C to 270°C.

[0031] Metal precursors are a) at least one metal cation, b) comprising at least one anion selected from the group consisting of carboxylates, carbamates, nitrates, and halide ions, and an oxime.

[0032] A combination of two or more metal precursors may be used, where the two or more metal precursors have the same metal cation but the same or different types of anions, or have different metal cations but the same type of anion. Examples of such combinations include a combination of silver carboxylate and tin carboxylate, a combination of two different silver carboxylates, and a combination of silver carboxylate and silver carbamate.

[0033] A carboxylate is a salt comprising one or more metal cations and one or more carboxylate anions. The carboxylic acid portion of the carboxylate anion may be linear or branched, or may have cyclic structural units, and may be saturated or unsaturated. More preferred types of carboxylates are monocarboxylates and dicarboxylates, or cyclic carboxylates. In one embodiment, linear saturated carboxylates, such as carboxylates having 1 to 20 carbon atoms, are preferred. Linear carboxylates can be selected from the group consisting of acetate, propionate, butyrate, valerate, hexanoate, heptanoate, octanoate, nonanoate, decanoate, undecanoate, dodecanoate, tetradecanoate, hexadecanoate, or octadecanoate. In another embodiment, saturated isocarboxylates and saturated neocarboxylates having 1 to 20 carbon atoms may be used. In one embodiment, saturated neocarboxylates having five or more carbon atoms, such as neopentanoate, neohexanoate, neoheptanoate, neooctanoate, neononanoate, neodecanoate, and neododecanoate, are preferred.

[0034] The halide ion is selected from the group consisting of fluoride ions, chloride ions, bromide ions, and iodide ions.

[0035] The metal content of MOD ink compositions is calculated based on the total weight of the ink composition, as is typically determined by thermogravimetric analysis (TGA), and is approximately 1% to 60% by weight, for example, approximately 1% to 50% by weight or approximately 10% to 40% by weight.

[0036] The MOD ink composition further comprises a solvent. In any case, the MOD ink composition contains about 0.1% to about 90% by weight, preferably about 20% to about 90% by weight, of the solvent based on the total weight of the MOD ink composition.

[0037] As a solvent, a solvent selected from the group consisting of glycol ethers, terpenes, aliphatic hydrocarbons, aromatic hydrocarbons, ketones, aldehydes, or combinations thereof can be used.

[0038] Glycol ethers are organic substances having at least one diol unit. Examples of glycol ethers include ethylene glycol ether, diethylene glycol ether, triethylene glycol ether, tetraethylene glycol ether, propylene glycol ether, and dipropylene glycol ether. Commercially available examples include DOWANOL PNP (propylene glycol n-propyl ether) and DOWANOL PNB (propylene glycol n-butyl ether), DOWANOL DPNB (dipropylene glycol n-butyl ether), and DOWANOL DPNP (dipropylene glycol n-propyl ether).

[0039] Terpenes are naturally occurring unsaturated hydrocarbons that can be isolated from natural materials, and their structure can be traced down to one or more isoprene units. Some terpenes are also industrially and artificially available. Terpenes are preferably acyclic or cyclic terpenes. Among cyclic terpenes, monocyclic terpenes are preferred. Preferably, terpenes are selected from orange terpenes, limonene, and pinene, or combinations thereof.

[0040] Other suitable solvents, such as aliphatic hydrocarbons, aromatic hydrocarbons, ketones, and aldehydes, are well known in the art.

[0041] The MOD ink composition may optionally contain one or more other components, such as adhesion promoters, viscosity enhancers, and other additives.

[0042] In one embodiment, the MOD ink composition may contain an adhesion promoter, preferably the amount of the adhesion promoter being about 0.1% to about 5% by weight, based on the total weight of the MOD ink composition.

[0043] In one embodiment, the MOD ink composition may contain one or more viscosity enhancers in a weight ratio of about 5% to about 30% by weight, more preferably about 10% to about 20% by weight, based on the total weight of the ink composition.

[0044] Rosin resin or its derivatives are suitable viscosity enhancers for ink compositions. A particularly preferred commercial product is balsam resin, available from H. Reynaud & Fils GmbH (Hamburg).

[0045] In one embodiment, the MOD ink composition may contain other additives in any proportion of about 0.05% to about 3% by weight, more preferably about 0.05% to about 1% by weight, based on the total weight of the ink composition. All chemical substances known to those skilled in the art as suitable as ink additives can be used as other additives. Particularly preferred are siloxane-containing additives such as polyether-modified polydimethylsiloxane.

[0046] In one embodiment, the MOD ink composition contains less than 1% by weight, less than 0.5% by weight, or less than 0.2% by weight of metal particles, based on the total weight of the MOD ink composition. Most preferably, the composition of the present invention is substantially free of metal particles.

[0047] The MOD ink composition may have a viscosity suitable for application, such as an ink composition having a viscosity of about 0.1 to about 100 mPa·s, for example, about 5 to about 30 mPa·s, when measured at a temperature of 20°C and an ambient pressure of 1013 hPa.

[0048] The components of the MOD ink composition can be mixed in any way known to those skilled in the art and considered suitable. Mixing can be carried out at a slightly higher temperature to facilitate the mixing process. Typically, the temperature during mixing does not exceed 40°C. The ink composition can be stored at room temperature or in a refrigerator.

[0049] Step II) In step ii), the precursor layer obtained in step i) is cured. During curing, the solvent in the wet layer evaporates, inducing nucleation within the layer.

[0050] Since the metals Ag, Ag / Sn, or Au in the MOD ink used in step i) are not easily oxidized, curing can be performed in air. Of course, curing can also be performed in an inert atmosphere. Examples of inert atmospheres include, but are not limited to, nitrogen, helium, argon, and neon.

[0051] The curing in step ii) may be carried out by heating and / or electromagnetic radiation. In one embodiment of the present invention, heating and electromagnetic radiation may be carried out simultaneously, or electromagnetic radiation may be carried out after heating, or heating may be carried out after electromagnetic radiation.

[0052] If curing is performed by heating, this may be done in an oven. The heating temperature may be about 50°C to about 250°C, preferably about 80°C to about 200°C, more preferably about 150°C to about 200°C, and the heating time may be about 1 to about 60 minutes, preferably about 5 to about 40 minutes.

[0053] When curing is performed by electromagnetic radiation, electromagnetic radiation having a wavelength of approximately 100 nm to approximately 1 mm, preferably approximately 100 nm to approximately 2000 nm, and more preferably approximately 100 nm to approximately 800 nm, may be used. The radiation intensity is approximately 100 W / cm². 2 ~Approx. 1000W / cm 2 Preferably about 100 W / cm² 2 ~about 500W / cm 2 More preferably, about 100 W / cm² 2 ~about 400W / cm 2 The radiation rate may be about 0.01 mm / sec to about 1000 mm / sec, preferably about 0.1 mm / sec to about 500 mm / sec, and more preferably about 0.1 mm / sec to about 50 mm / sec. The radiation may be performed 1 to 100 times, preferably 1 to 50 times.

[0054] In one embodiment of the present invention, a cycle including steps i) and ii) is performed one or more times, and in each cycle, step i) is performed one or more times, and step ii) is performed one or more times. For example, the cycle may be performed 1 to 10 times, preferably 1 to 5 times, more preferably 1 to 3 times, and in each cycle, step i) is performed 1 to 10 times, preferably 1 to 5 times, more preferably 1 to 3 times, and step ii) is performed 1 to 10 times, preferably 1 to 5 times, more preferably 1 to 3 times.

[0055] When multiple cycles are performed, a layer having a thickness of 100 nm to 800 nm, preferably 150 nm to 500 nm, and more preferably 200 nm to 300 nm, is formed in each cycle.

[0056] Other steps The method of the present invention may further include step iii), i.e., the step of annealing the layer obtained in step ii).

[0057] The annealing temperature is related to the melting point of the metal, with higher annealing temperatures used for metals with higher melting points. The annealing temperature may be about 120°C to about 500°C, preferably about 150°C to about 460°C. The annealing time is also related to the melting point of the metal, with longer annealing times used for metals with higher melting points. The annealing time may be about 1 to about 60 minutes, preferably about 5 to about 40 minutes, more preferably about 5 to about 30 minutes.

[0058] Since the metals Ag, Ag / Sn, or Au in the MOD ink used in step i) are not easily oxidized, annealing can be performed in air. Of course, annealing can also be performed in an inert atmosphere. Examples of inert atmospheres include, but are not limited to, nitrogen, helium, argon, and neon.

[0059] Annealing can be carried out in any suitable apparatus, such as a tubular furnace.

[0060] The method of the present invention may also include other steps, such as cleaning a semiconductor wafer.

[0061] In one embodiment of the present invention, the semiconductor wafer may be cleaned to remove any possible oxides on its surface before each layer (e.g., a MOD ink composition layer) is applied to the semiconductor wafer, or before each layer (e.g., a MOD ink composition layer) is applied to any other layers already present on the semiconductor wafer. The presence of oxides can increase contact resistance and affect adhesion, which in turn can affect product performance. In addition, cleaning can enhance film adhesion by activating chemical bonds on the surface, as well as remove residual contaminants from the surface. Alternatively, the oxide layer on the surface may be retained during the cleaning process.

[0062] Possible cleaning methods include plasma cleaning and chemical cleaning. Preferably, cleaning is performed using plasma. Examples of plasma cleaning include Ar plasma cleaning, air plasma cleaning, or vacuum plasma cleaning. The plasma cleaning time may be about 1 to about 60 minutes, preferably about 1 to about 10 minutes. Suitable chemical cleaning methods are well known in the art.

[0063] After cleaning the semiconductor wafer, a base layer can be applied to it. Suitable base layers may be an adhesive layer and a barrier layer. The adhesive layer is in direct contact with the silicon wafer surface, and the barrier layer is placed on top of the adhesive layer to prevent oxidation of the adhesive layer and to prevent interdiffusion between the adhesive layer and subsequent Ag, Ag / Sn, or Au layers (as described above). Of course, layers having both adhesive and barrier functions can also be applied.

[0064] Specifically, the method of the present invention involves the following steps performed before step i): 1) The step of forming an adhesive layer and a barrier layer on a semiconductor wafer, 2) Further includes the step of forming a layer having both adhesive and barrier functions on a semiconductor wafer.

[0065] Surprisingly, wafers equipped with layers possessing both adhesive and barrier functions, as well as Ag, Ag / Sn, or Au layers, were found to have excellent thermal and electrical conductivity.

[0066] The base layer may be applied by chemical vapor deposition, sputter deposition, electroplating, spraying, spin coating, dip coating, or inkjet printing, preferably by inkjet printing. When spraying, spin coating, dip coating, or inkjet printing is used, a MOD ink composition containing a precursor of the metal to be applied is also preferably used. The MOD ink compositions used are those described above for Ag, Ag / Sn, or Au layers, the difference being that the metal used is the same as that used for the base layer.

[0067] The inkjet printing of the base layer can also be performed in a patterned manner. Inkjet printing is carried out by an inkjet printer, preferably a piezoelectric inkjet printer. The number of layers applied by inkjet printing may be one or more layers, preferably 1 to 10 layers. The layer thickness of the inkjet print can be adjusted by adjusting the print resolution and the number of layers. The DPI range X / Y of the inkjet print may be 300 to 3000.

[0068] After the application of the base layer, the resulting base layer may be cured and annealed as described above. In this invention, the curing and annealing processes may be collectively referred to as "post-treatment" in some cases.

[0069] When applying adhesive layers and barrier layers to a semiconductor wafer, this can be done by (i) applying one or more adhesive layers, curing and / or annealing the adhesive layers, then applying one or more barrier layers, curing and / or annealing the barrier layers, or (ii) applying one or more adhesive layers, then applying one or more barrier layers, and then curing and / or annealing the resulting composite layer together. In case (i), when multiple adhesive layers are applied, it is possible to apply each adhesive layer, then cure and / or anneal it, then apply the next adhesive layer, then cure and / or anneal that next adhesive layer, and so on, until the desired thickness is obtained. It is also possible to cure and / or anneal all of the applied adhesive layers together after multiple adhesive layers have been applied. Similarly, in case (i), when multiple barrier layers are applied, it is possible to apply each barrier layer until the desired thickness is obtained, then cure and / or anneal that barrier layer, then apply the next barrier layer, then cure and / or anneal that barrier layer, and so on. It is also possible to cure and / or anneal all the applied barrier layers together after multiple barrier layers have been applied.

[0070] The curing is carried out by electromagnetic radiation and / or heating. When the curing is carried out by heating, the heating temperature is about 50°C to about 250°C, preferably about 80°C to about 200°C, more preferably about 150°C to about 200°C, and the heating time is about 1 to about 60 minutes, preferably about 5 to about 40 minutes. When the curing is carried out by electromagnetic radiation, electromagnetic radiation having a wavelength of about 100 nm to about 1 mm, preferably about 1000 nm to about 2000 nm, more preferably about 100 nm to about 800 nm may be used. For the curing of the adhesive layer and the barrier layer, the radiation intensity is about 1 W / cm 2 ~ about 100 W / cm 2 、 preferably about 10 W / cm 2 ~ about 50 W / cm 2 may be. The radiation speed may be about 0.01 mm / second to about 1000 mm / second, preferably about 0.1 mm / second to about 500 mm / second, more preferably about 0.1 mm / second to about 50 mm / second. The radiation may be performed 1 to about 100 times, preferably 1 to about 50 times.

[0071] When the metal in the MOD ink used for the base layer is easily oxidized, for example, in the case of Ti and Ni, it tends to be converted to an oxide during curing, so annealing in an inert atmosphere is necessary to prevent the oxidation of the metal. When the metal in the MOD ink used for the base layer is not easily oxidized, for example, in the case of Pt, Ag, and Au, the curing can be carried out in air. Of course, curing in an inert atmosphere is also possible. Examples of the inert atmosphere include, but are not limited to, nitrogen, helium, argon, and neon.

[0072] The annealing temperature may be about 120°C to about 500°C, preferably about 150°C to about 460°C. The annealing time is also related to the melting point of the metal, and a longer annealing time is used for metals having a higher melting point. The annealing time may be about 1 to about 60 minutes, preferably about 5 to about 40 minutes, more preferably about 5 to about 30 minutes. As described above, depending on the metal used, the annealing of the base layer may be carried out in a reducing atmosphere or an inert atmosphere.

[0073] The base layer can also be applied by PVD (Photovoltaic Vatification). Specific PVD process conditions are well known in the art.

[0074] The metal used in the adhesive layer may be titanium (Ti), bismuth (Bi), tin (Sn), aluminum (Al), chromium (Cr), vanadium (V), yttrium (Y), cerium (Ce), silicon (Si), tin (Sn), zinc (Zn), or mixtures thereof. The metal used in the barrier layer may be nickel (Ni), vanadium (Vi), chromium (Cr), or mixtures thereof such as nickel-vanadium (NiV). For layers having both adhesive and barrier functions, preferred metals are bismuth (Bi), nickel-vanadium (NiV), or tungsten (W), more preferably Bi.

[0075] The thickness of the adhesive layer may be 50 nm to 500 nm, preferably 50 nm to 100 nm. The thickness of the barrier layer may be 100 nm to 500 nm, preferably 100 nm to 200 nm. The thickness of the layer having both adhesive and barrier functions may be 30 nm to 500 nm, preferably 50 nm to 100 nm.

[0076] In the context of this invention, the adhesive layer and the barrier layer are clearly defined, but it should be noted that in actual manufacturing processes, the adhesive layer and the barrier layer may fuse at the interface to form an interfacial layer.

[0077] Embodiments of the Method of the Present Invention Figure 1 shows (i) A step of compounding MOD (metal precursor + solvent), (ii) A step of inkjet printing a wet layer onto the back surface of a wafer using MOD ink filled in a piezoelectric press, wherein the layer thickness can be adjusted by adjusting the printing resolution and the number of layers. (iii) The step of curing the wet-printed layer by electromagnetic radiation to evaporate the solvent and nucleate it, (iv) The step of annealing the hardened layer in a tubular oven, Steps (ii) and (iii) together can be performed one or more times to obtain a desired layer thickness, illustrating one embodiment of the method of the present invention.

[0078] In a preferred embodiment, the present invention is a method for manufacturing a semiconductor wafer, 1) A step of plasma cleaning the wafer, 2) The step of inkjet printing the adhesive layer, 3) A step of post-treatment of the adhesive layer, 4) The step of inkjet printing the barrier layer, 5) A step of post-processing the barrier layer, 6) A step of inkjet printing an Ag, Ag / Sn, or Au layer, 7) A method comprising the step of post-processing the silver layer.

[0079] The post-treatment conditions for the adhesive layer / barrier layer are as follows: Curing: Radiation intensity 1W / cm 2 ~100W / cm 2 Wavelength 100nm~1mm, and speed 0.1mm / sec~1000mm / sec, 1~100 times. Annealing: 120°C to 500°C for 1 to 30 minutes.

[0080] The post-treatment conditions for Ag, Ag / Sn, or Au layers are as follows: Curing: radiation intensity 100W / cm 2 ~1000W / cm 2 Wavelength 100nm~1mm, and speed 0.1mm / sec~100mm / sec, 1~100 times. Annealing: 120°C to 500°C for 1 to 30 minutes.

[0081] Advantages of the method of the present invention The present invention utilizes MOD ink to deposit different thin film layers on the back surface of a silicon wafer, and is intended for wafer metallization applications in semiconductor devices. This can save equipment costs and reduce material waste. In particular, in preferred embodiments of the present invention, inkjet printing is used to apply the MOD ink, which makes it possible to manufacture films using an industrial-scale piezoelectric inkjet press, which is an additive manufacturing process and has the following main advantages. 1. Low equipment cost and low power consumption (no vacuum required). 2. No material waste. 3. On-demand printing facilitates selective deposition / design flexibility (no etching required).

[0082] Wafers obtained by inkjet printing with MOD ink and post-processing according to the present invention have a different layer microstructure compared to layers produced by PVD or nanoparticle ink. Conventional PVD results in a very dense layer, while the use of conventional inks containing nanometal particles typically results in a layer with small aggregates and high porosity. In contrast, the MOD layer of the present invention has a dense structure containing large crystal grains after annealing, and the shape of each layer can be easily adjusted by adjusting the post-processing conditions. This results in the excellent conductivity of the Ag, Ag / Sn, or Au layers of the present invention. In particular, the conductivity of the Ag, Ag / Sn, or Au layers obtained by the method of the present invention is higher than that of layers obtained using conventional nanometal inks and is equivalent to that of layers obtained using conventional PVD methods.

[0083] Other aspects of the present invention In another aspect of the present invention, a semiconductor wafer obtained by the method of the present invention is provided.

[0084] In yet another aspect of the present invention, a semiconductor device comprising a semiconductor wafer of the present invention is provided.

[0085] In a further aspect of the present invention, a semiconductor wafer precursor is provided, comprising a) a semiconductor wafer and b) an uncured MOD ink layer. [Brief explanation of the drawing]

[0086] [Figure 1] A schematic diagram of the method of the present invention is shown. [Figure 2] The electron microscope image of the cross-section of the bismuth oxide / silver stack from Example 2 is shown. [Examples]

[0087] The following embodiments are intended to further illustrate the present invention, but are not intended to limit its scope.

[0088] Test method Square resistivity A four-point probe obtained from Ossila (Sheffield, UK) was used to measure the square resistivity of the layer obtained by the method of the present invention.

[0089] Peel test The adhesion of the metallization layer to the wafer was characterized by a peel test. The peel test standard used was ASTM D3359-09.

[0090] Example 1 In this embodiment, the Ti / Ni layers, which serve as the adhesive and barrier layers, were produced using PVD (obtained from Shanghai Yuquan Trading Co., Ltd.), and the silver layer was produced by inkjet printing using MOD ink, with the following parameters for each layer. Adhesive layer: Ti, 50nm Barrier layer: Ni, 100nm Silver layer: Ag, 300nm

[0091] The process flow was as follows: Clean with Ar plasma for 1.5 minutes. 2. PVD coating is applied to Ti to a thickness of 50nm. 3. Apply PVD to Ni to a thickness of 100 nm. 4. Using a Heraeus inkjet printer, printhead model: RICOH MH5421F, MOD silver ink was inkjet printed at a DPI of 1200 x 1600, in a single layer. The MOD silver ink consisted of 15 wt% silver neodecanoate and 85 wt% limonene (DL-limonene, CAS number 138-86-3, obtained from Merck KGaA, catalog number 814546), based on the total weight of the ink. 5. The silver ink layer is cured using the Heraeus UV curing device Heraeus Semray 4103 (wavelength: 395nm, speed: 1mm / sec, 1 pass, radiation intensity 250W / cm²). 2 ). 6. Annealing is performed using the SG-XL1200 annealing apparatus under the different conditions shown in the table below.

[0092] The resulting metallization layer was tested, and the results are shown in the table below. [Table 1]

[0093] The adhesion performance of the entire metallization layer (Ti+Ni+Ag layer) on the wafer was tested, yielding good results and passing the 4B / 5B standard. The square resistance of the Ag layer was approximately 64 mΩ / sq. There was no essential difference in the peel test or square resistance under different annealing conditions.

[0094] Example 2 In this example, MOD ink was used, and all layers were applied by inkjet printing. The parameters for each layer were as follows: Printed layer having both adhesive and barrier functions: bismuth oxide, 60 nm, Printed silver layer: Ag, 590nm.

[0095] The process flow was as follows: 1. Inkjet printing of the adhesive and barrier layers: A Heraeus inkjet printer, printhead model: RICOH MH5421F was used, MOD bismuth ink, DPI: 564 x 564, 1 layer. The MOD bismuth ink consisted of 15 wt% bismuth neodecanoate and 85 wt% Dowanol PNP (propylene glycol n-propyl ether, CAS number 1569-01-3, obtained from The Dow Chemical Company, Inc. (Maryland, USA)), based on the total weight of the ink. 2. Using the SG-XL1200 annealing device, dry at 100°C for 10 minutes, then anneal at 450°C for 10 minutes. 3. Printhead Model: A Heraeus inkjet printer equipped with a RICOH MH5421F inkjet printer was used to print MOD silver ink at a DPI of 1270 x 1270, in three layers. The MOD silver ink consisted of 15 wt% silver neodecanoate and 85 wt% limonene (DL-limonene, CAS number 138-86-3, obtained from Merck KGaA, catalog number 814546), based on the total weight of the ink. 4. Using the SG-XL1200 annealing device, dry at 100°C for 10 minutes, then anneal at 450°C for 10 minutes.

[0096] When the adhesion performance of the entire metallization layer (bismuth oxide + silver layer) on the wafer was tested, good results were obtained, passing the 5B standard, and the square resistance of the Ag layer was approximately 42 mΩ / sq.

[0097] Figure 2 shows an electron microscope image of a cross-section of the bismuth oxide / silver stack layer in this embodiment. From Figure 2, it can be seen that the bismuth oxide layer was in good contact with the substrate, as was the silver layer, and the film structure was very dense with low porosity.

Claims

1. A method for manufacturing semiconductor wafers, The back surface of the semiconductor wafer is metallized by the above method, i) The step of applying the MOD ink composition to a semiconductor wafer to form a precursor layer, ii) The step of curing the precursor layer, The MOD ink composition in step i) is a solution comprising a) at least one metal precursor and b) a solvent, wherein the MOD ink composition does not contain metal particles constituting the metal precursor, or contains less than 1% by weight of metal particles constituting the metal precursor based on the total weight of the MOD ink composition, and the metal in the MOD ink composition is Ag, Ag / Sn, or Au. In step ii), the curing is carried out by electromagnetic radiation and / or heating at a temperature of 150°C to 300°C. The above method is performed in the step preceding step i): 1) A step of forming an adhesive layer and a barrier layer as a base layer on the semiconductor wafer, and curing and annealing the obtained base layer. or 2) The process further includes forming a base layer on the semiconductor wafer having both adhesive and barrier functions, and curing and annealing the obtained base layer. A method wherein the formation of the base layer in step 1) and 2) is performed by inkjet printing.

2. The method according to claim 1, wherein the application in step i) is performed by spraying, spin coating, dip coating, or inkjet printing.

3. The method according to claim 1 or 2, wherein a cycle including steps i) and ii) is performed one or more times, and in each cycle, step i) is performed one or more times and step ii) is performed one or more times.

4. The method according to claim 3, wherein, when multiple cycles are performed, a layer having a thickness of 100 nm to 800 nm is formed in each cycle.

5. The radiation intensity is 100 W / cm². ２ ~1000W / cm ２ The method according to claim 1 or 2, wherein the radiation wavelength is 100 nm to 1 mm.

6. iii) The method according to claim 1 or 2, further comprising the step of annealing the precursor layer obtained after curing.

7. The method according to claim 6, wherein the annealing in step iii) is performed at a temperature of 120°C to 500°C.

8. The method according to claim 1 or 2, wherein the back surface and the front surface of the semiconductor wafer are metallized by the method described above.

9. The semiconductor wafer is a Si wafer, a SiC wafer, a GaN wafer, a GaAs wafer, or Ga ２ O ３ The method according to claim 1 or 2, wherein the material is a wafer.

10. The method according to claim 1 or 2, wherein the metal precursor has a decomposition temperature of 80°C to 500°C.

11. The aforementioned metal precursor a) At least one metal cation, b) The method according to claim 1 or 2, comprising at least one anion selected from the group consisting of carboxylates, carbamates, nitrates, and halide ions, and an oxime.

12. The method according to claim 1 or 2, wherein, when the formation of the precursor layer is carried out by spraying, spin coating, dip coating, or inkjet printing, the ink used is a MOD ink composition.

13. The method according to claim 1 or 2, wherein the MOD ink composition is a bismuth-containing MOD ink composition.

14. The method according to claim 1 or 2, wherein after forming each base layer in step 1) or 2), the obtained wafer is cured and / or annealed.

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