CN114388350B - Wafer cleaning method and device - Google Patents

Abstract

The invention belongs to the technical field of semiconductor manufacturing, and discloses a method and a device for cleaning wafers. The method includes: S1, placing a wafer to be cleaned after laser grooving and plasma cutting in a vacuum chamber, Introduce nitrogen or inert gas to clean the particles on the surface of the wafer to be cleaned; S2, maintain the vacuum environment of the vacuum chamber, and inject water vapor into it to clean the laser protective glue on the surface of the wafer to be cleaned; S3, maintain the vacuum chamber In the vacuum environment, the plasma formed by the ionization of the oxidizing gas is passed into it to clean the polymer on the surface of the wafer; S4, the vacuum environment of the vacuum chamber is maintained, and the plasma formed by the ionization of the reducing gas is passed into it to reduce the crystal Copper oxide with round surface. The method of the invention simply relies on gas to clean the wafer after cutting step by step, so as to ensure that various impurities on the surface of the wafer are completely removed without damaging the carrier film and the surface structure of the wafer. The method simplifies the process and is efficient and environmentally friendly.

Description

Wafer cleaning method and device

technical field

The invention belongs to the technical field of semiconductor manufacturing, and more particularly, relates to a wafer cleaning method and device.

Background technique

As semiconductor technology enters the post-Moore era, in order to meet the needs of high integration and high performance, the chip structure is developing in a three-dimensional direction. Among them, the realization of "heterogeneous mixing" through bonding technology is one of the important technologies of "Super Moore's Law". The hybrid bonding process can interconnect chips of different process nodes with high density to achieve smaller size and higher System-level integration for performance and lower power consumption. Existing hybrid bonding methods usually include wafer-to-wafer bonding (wafertowafer, W2W), chip-to-chip bonding (chipto chip, C2C) and chip-to-wafer bonding (chiptowafer, C2W). For the C2W hybrid bonding process, the wafer needs to be fixed on a carrier film (such as UV film or blue film) for laser grooving and plasma dicing before bonding, but the wafer after dicing There are a large number of particles, laser protective glue and polymers generated during the cutting process remaining on the surface. If the wafer surface is not cleaned, the bonding will fail, which will affect the yield of chip-to-wafer bonding. Therefore, the diced wafer needs to be effectively cleaned before bonding.

At present, chemical reagents are usually used to clean the wafer, or even a combination of various chemical reagents, which brings great challenges to the solvent resistance and high temperature resistance of the carrier film. In the process of cleaning the wafer with chemical reagents, it is very likely to cause damage to the UV film, and the chemical reagent may also react with the UV film to contaminate the wafer. Therefore, it is a technical problem to be solved urgently at present to ensure that the surface of the wafer is not damaged without destroying the UV film during the cleaning process.

SUMMARY OF THE INVENTION

In view of the defects of the prior art, the purpose of the present invention is to provide a wafer cleaning method and device, which aims to solve how to ensure that the wafer cleaning process does not damage the carrier film but also enables the wafer in the chip-to-wafer bonding process. The problem with the surface remaining intact.

To achieve the above purpose, the present invention provides a wafer cleaning method, comprising the following steps:

S1, placing the wafer to be cleaned after laser slotting and plasma cutting in a vacuum chamber, and feeding nitrogen or an inert gas into the vacuum chamber to clean the particles on the surface of the wafer;

S2, maintaining the vacuum environment of the vacuum chamber, and feeding water vapor into it to clean the laser protective glue on the surface of the wafer;

S3, maintaining the vacuum environment of the vacuum chamber, and passing the plasma formed by the ionization of the oxidizing gas into it to clean the polymer on the surface of the wafer;

S4. Maintain the vacuum environment of the vacuum chamber, and pass plasma formed by ionization of a reducing gas into the vacuum chamber to reduce the copper oxide on the surface of the wafer.

Preferably, in step S1, the vacuum degree of the vacuum chamber is 50mTorr~150mTorr, the gas flow rate of the nitrogen gas or the inert gas is 50sccm~100sccm, and the cleaning time is 5min~10min.

Preferably, in step S2, the vacuum degree of the vacuum chamber is 50mTorr~150mTorr, the gas flow rate of the water vapor introduced is 50sccm~100sccm, and the cleaning time is 5min~10min.

Preferably, in step S3, the oxidizing gas is a mixed gas of oxygen and nitrogen.

Preferably, the oxygen volume fraction in the oxidizing gas is 10%-30%.

Preferably, in step S4, the reducing gas is a mixed gas of hydrogen and nitrogen or a mixed gas of ammonia and nitrogen.

Preferably, the reducing gas is a mixed gas of hydrogen and nitrogen, wherein the volume fraction of hydrogen is less than 5%.

Preferably, in step S3 and step S4, the vacuum degree of the vacuum chamber is 100mTorr~200mTorr, and the flow rate of the entering plasma is 50sccm~150sccm.

According to another aspect of the present invention, a wafer cleaning device is also provided, comprising:

After vacuuming, a cleaning chamber with a vacuum environment can be formed. The cleaning chamber is provided with a stage for placing and fixing the wafer to be cleaned and a gas shower head opposite to the wafer to be cleaned. The spray hole of the shower head faces the wafer to be cleaned;

an air inlet pipe, communicated with the gas shower head, and used for inputting cleaning gas into the cleaning chamber;

a plasma generator, the output end of which is communicated with the gas shower head, and is used for providing cleaning plasma into the cleaning chamber;

An air extraction device, communicated with the cleaning chamber, is used for extracting the gas inside the cleaning chamber.

Preferably, the area of the area covered by the spray holes of the gas shower head is not less than the area of the bonding surface of the wafer to be cleaned.

In general, compared with the prior art, the above technical solutions conceived by the present invention have the following beneficial effects:

(1) The present invention simply adopts the gas cleaning method for the wafer after laser grooving and plasma cutting, and processes the wafer surface step by step in a certain order to ensure that the impurities on the wafer surface are completely removed without damaging the carrier film and Wafer surface structure, this method does not require wet cleaning and then drying, which simplifies the cleaning process and is efficient and environmentally friendly. At the same time, the traditional method of cleaning the wafer with nitrogen or inert gas is usually only used to remove the residual abrasive particles on the surface of the wafer after chemical mechanical polishing (chemical mechanical polishing), and cannot remove the laser grooving and plasma cutting processes. Laser protective glue and reactive polymer on the surface of the back wafer; and the traditional plasma cleaning process is to ionize plasma in a vacuum chamber to bombard the surface of the wafer, which will inevitably increase the roughness of the wafer surface and affect the subsequent The bonding effect, and the cleaning method of the present invention can overcome the above deficiencies and achieve the purpose of improving the subsequent bonding yield.

(2) The wafer cleaning device provided by the present invention supplies cleaning gas and plasma to the cleaning chamber through the air inlet pipe and the plasma generator, respectively, so as to complete different cleaning steps. The plasma is first prepared and then passed into the cleaning chamber, thereby avoiding the damage caused by the high-pressure bombardment of the wafer surface by the plasma directly in the cleaning chamber, and improving the yield of the chip-to-wafer bonding process.

Description of drawings

FIG. 1 is a process flow diagram of a wafer cleaning method according to an embodiment of the present invention.

FIG. 2 is a schematic structural diagram of a wafer cleaning apparatus according to an embodiment of the present invention.

Detailed ways

In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention, but not to limit the present invention.

Referring to FIG. 1, a wafer cleaning method provided by an embodiment of the present invention includes the following steps:

S1, placing the wafer to be cleaned after laser slotting and plasma cutting in a vacuum chamber, and feeding nitrogen or an inert gas into the vacuum chamber to clean the particles on the surface of the wafer;

S2, maintaining the vacuum environment of the vacuum chamber, and feeding water vapor into it to clean the laser protective glue on the surface of the wafer;

S3, maintaining the vacuum environment of the vacuum chamber, and passing the plasma formed by the ionization of the oxidizing gas into it to clean the surface of the wafer;

S4, maintaining the vacuum environment of the vacuum chamber, and passing the plasma formed by ionization of the reducing gas into the vacuum chamber to clean the surface of the wafer.

The wafer to be cleaned provided in this embodiment is a diced wafer, and the dicing process may include laser grooving and plasma dicing. In step S1, the nitrogen or inert gas introduced can clean the large particles generated during the laser grooving and plasma cutting and the particles dropped during the wafer transfer. Specifically, in the cleaning process, the vacuum degree of the vacuum chamber is adjusted to 50mTorr~150mTorr, the gas flow rate of nitrogen or inert gas is 50sccm~100sccm, and the cleaning time is 5min~10min.

In step S2, according to the water-soluble characteristics of the laser protective glue coated on the surface of the wafer before the laser grooving, water vapor is used to remove the water-soluble laser protective glue on the surface of the wafer to be cleaned, compared with the treatment with liquid water. , it does not need to be dried after treatment, and the treated water vapor can be discharged directly through the air extraction equipment, which is more convenient to operate; and the boiling point of water in the vacuum state will be reduced, which is conducive to maintaining the gas state of water vapor at a lower temperature. Prevent excessively high temperature water vapor from damaging the carrier film. Specifically, in the cleaning process using water vapor, the vacuum degree of the vacuum chamber is 50mTorr~150mTorr, the flow rate of the gas introduced is 50sccm~100sccm, and the cleaning time is 5min~10min.

In step S3, since the plasma will react with the laser protective glue to generate some polymers during the plasma cutting process, the plasma formed by the ionization of the oxidizing gas introduced is adsorbed on the wafer surface, and reacts with the wafer surface polymer to form a gas phase. , thereby causing the polymer to peel off the wafer surface. Specifically, the oxidizing gas is a mixed gas of oxygen and nitrogen, wherein the volume fraction of oxygen is 10%-30%.

In step S4, since the bonding copper pads on the wafer surface in step S3 will be oxidized into copper oxide, the wafer surface is cleaned by high-energy plasma formed by ionization of reducing gas, so that the copper oxide is reduced to copper, so as to prevent the subsequent process from being affected. . Specifically, the reducing gas is a mixed gas of hydrogen and nitrogen or a mixed gas of ammonia and nitrogen, preferably a mixed gas of hydrogen and nitrogen, wherein the volume fraction of hydrogen is less than 5%.

In some embodiments, in step S3 and step S4, the vacuum degree of the vacuum chamber is maintained at 100 mTorr˜200 mTorr, and the flow rate of the incoming plasma is 50 sccm˜150 sccm.

Referring to FIG. 2 , an embodiment of the present invention further provides a wafer cleaning apparatus, including a cleaning chamber 1 , a carrier 3 , a gas shower head 4 , at least one air inlet pipe 5 and a plasma generator 6 .

The cleaning chamber 1 has a space suitable for placing the wafer 2 to be cleaned. The specific shape of the space is not limited. It can be a regular shape, such as a rectangular parallelepiped, or an irregular shape, as long as the wafer 2 to be cleaned can be accommodated. Yes, the entire cleaning process of the wafer 2 to be cleaned is performed in the cleaning chamber 1, and the cleaning chamber 1 is in a vacuum state during the cleaning process. In this embodiment, the cleaning chamber 1 can directly use the chamber in the plasma cutting device. After the plasma cutting, the wafer after cutting is directly cleaned in the chamber without moving the wafer, which saves the process and time. . The cleaning chamber 1 has an air inlet and an air outlet. Preferably, the air inlet and the air outlet are respectively arranged on opposite sides of the cleaning chamber 1, that is, when the air inlet is arranged on the top of the cleaning chamber 1, the outlet is The air port is arranged at the bottom of the cleaning chamber 1 ; when the air inlet is arranged at the bottom of the cleaning chamber 1 , the air outlet is arranged at the top of the cleaning chamber 1 . The gas outlet is used to discharge the gas inside the cleaning chamber 1 .

The wafer to be cleaned 2 provided in this embodiment is a wafer that has been cut. During the cutting process, the wafer needs to be fixedly attached to the carrier film 8. The carrier film 8 can be a UV film or a blue film. The carrier film 8 is attached to the bandage ring 9, which is used to fix the carrier film 8 and stretch it flat. The wafer and the wrapping ring 9 are attached to the same side of the carrier film 8 , and the wafer is located in the inner annular surface of the wrapping ring 9 .

The stage 3 is disposed inside the cleaning chamber 1 for placing and fixing the wafer 2 to be cleaned. Specifically, as shown in FIG. 2 , the cut wafer 2 to be cleaned together with the carrier film 8 and the wrap ring 9 is placed on the carrier 3 , and the side of the carrier film 8 facing away from the wafer 2 to be cleaned faces the surface of the carrier 3 .

The gas shower head 4 is also arranged inside the cleaning chamber 1 and opposite to the wafer 2 to be cleaned. The gas input through the air inlet of the cleaning chamber 1 is sprayed to the wafer 2 to be cleaned through the gas shower head 4 . The gas shower head 4 has an inlet surface and an outlet surface, the outlet surface faces the wafer 2 to be cleaned, the inlet surface and the outlet surface are connected, and the outlet surface is evenly arranged with a plurality of spray holes, and the gas entering from the inlet surface passes through The spray holes on the air outlet surface spray evenly. The shape of the gas shower head 4 is not limited in the present invention, and it is preferably circular, which is the same as the shape of the wafer 2 to be cleaned; , the area covered by the plurality of spray holes is not less than the bonding surface area of the wafer 2 to be cleaned, so as to ensure that all parts of the surface of the wafer 2 to be cleaned are thoroughly cleaned.

The present invention does not limit the specific position of the gas shower head 4 in the cleaning chamber 1 . When the gas shower head 4 is arranged on the top of the cleaning chamber 1 , the gas outlet of the gas shower head 4 faces downwards, the carrier 3 is located at the bottom of the cleaning chamber 1 , and the wafer 2 to be cleaned is fixedly placed on the carrier 3 The upper surface of the wafer 2 to be bonded is cleaned by the gas sprayed downward from the gas outlet surface of the gas shower head 4 . The gas shower head 4 can also be arranged at the bottom of the cleaning chamber 1, the gas outlet surface of the gas shower head 4 faces upward, the wafer 2 to be cleaned is located above the gas shower head 4 and the surface to be bonded faces downward, from The surface of the wafer 2 to be cleaned is cleaned by the gas sprayed upward from the gas outlet surface of the gas shower head 4 .

One end of the air inlet pipe 5 is connected to the clean gas source, and the other end is communicated with the air inlet surface of the gas shower head 4 through the air inlet of the cleaning chamber 1, and is used to input clean gas (including nitrogen, inert gas or water vapor). When the number of intake pipes 5 is one, nitrogen or inert gas is first introduced through the intake pipe 5 , then the gas source is replaced, and then water vapor is introduced through the intake pipe 5 . As a preferred embodiment, the number of intake pipes 5 can be set to two, including a first intake pipe and a second intake pipe. The first intake pipe is connected to a nitrogen or inert gas source and is specially used for conveying nitrogen or inert gas ; The second air inlet pipe is connected with the water vapor source, which is specially used to transport water vapor.

The output end of the plasma generator 6 is communicated with the air inlet surface of the gas shower head 4, and the oxidizing gas or reducing gas is inputted from the input end thereof, and ionized inside the generator to form plasma and then passed into the cleaning chamber 1, A cleaning plasma is provided for the wafer 2 to be cleaned. In traditional plasma processing equipment, the cleaning chamber is used as a reaction chamber, gas is introduced into the chamber, and a high-frequency electric field is generated between the shower head and the stage, thereby generating plasma to bombard the surface of the wafer, causing the wafer The surface roughness increases, and the bonding process has strict requirements on the surface roughness of the wafer. Generally, the roughness is required to be less than 2nm, which will eventually affect the bonding yield. In the present invention, the plasma is generated and then passed into the cleaning chamber 1 , which is more friendly to cleaning the surface of the wafer 2 .

The output end of the plasma generator 6 and the air inlet pipe 5 can be connected to the gas shower head 4 through their respective pipelines. More preferably, the two pipelines are combined and then connected to the gas shower head 4, that is, in FIG. 2 . In the shown structure, the merging pipeline is located in the center of the gas shower head 4, so that the gas passing through the gas shower head 4 can be uniformly dispersed and sprayed from the middle to the periphery. Valves are provided on the connecting pipeline of the output end of the plasma generator 6 and on the air inlet pipe 5 to control the start and stop of different ventilation processes.

The wafer cleaning device of the present invention may include an air extraction device 7 connected to the air outlet of the cleaning chamber 1 , or an existing device capable of realizing air extraction may be externally connected when the wafer cleaning device is used. In this embodiment, the pumping device 7 can be a molecular pump or a dry pump. Clean the vacuum environment of chamber 1.

The specific operation of using the above-mentioned wafer cleaning device to clean the wafer after cutting is as follows:

(1) Place the wafer 2 to be cleaned on the stage 3 and fix it, vacuum the cleaning chamber 1, and then introduce nitrogen or inert gas into the cleaning chamber 1 through the air inlet pipe 5 and the gas shower head 4, After cleaning for a period of time, during the ventilation process, the air extraction device 7 is simultaneously turned on for air extraction, the reaction by-products in the cleaning process are removed and a certain degree of vacuum in the cleaning chamber 1 is maintained, and the following steps are synchronized with this step;

(2) After the cleaning in step (1) is completed, replace the gas source, and pass water vapor into the vacuum cleaning chamber 1 through the air inlet pipe 5 and the gas shower head 4 for cleaning for a period of time;

(3) After the cleaning in step (2) is completed, the plasma generator 6 is turned on, and the oxidizing gas is introduced into the plasma generator 6, and the plasma of the generated oxidizing gas is sprayed to the to-be-cleaned through the gas shower head 4. The surface of wafer 2 is cleaned;

(4) After the cleaning in step (3) is completed, a reducing gas is introduced into the plasma generator 6, and the plasma of the reducing gas is sprayed to the surface of the wafer 2 to be cleaned through the gas shower head 4 to remove the copper oxide. reduced to copper.

Those skilled in the art can easily understand that the above are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention, etc., All should be included within the protection scope of the present invention.

Claims (8)

1. a wafer cleaning method, is characterized in that, comprises the steps: S1, placing the wafer to be cleaned after laser slotting and plasma cutting in a vacuum chamber, and feeding nitrogen or an inert gas into the vacuum chamber to clean the particles on the surface of the wafer; S2, maintaining the vacuum environment of the vacuum chamber, and feeding water vapor into it to clean the laser protective glue on the surface of the wafer; S3, maintaining the vacuum environment of the vacuum chamber, and passing the plasma formed by the ionization of the oxidizing gas into it to clean the polymer on the surface of the wafer; S4. Maintain the vacuum environment of the vacuum chamber, and pass plasma formed by ionization of a reducing gas into the vacuum chamber to reduce the copper oxide on the surface of the wafer. 2. The wafer cleaning method according to claim 1, wherein in step S1, the vacuum degree of the vacuum chamber is 50mTorr～150mTorr, and the gas flow rate of the nitrogen gas or inert gas introduced is 50sccm～100sccm , the cleaning time is 5min~10min. 3. The wafer cleaning method according to claim 1, characterized in that: in step S2, the vacuum degree of the vacuum chamber is 50mTorr～150mTorr, and the gas flow rate of the water vapor introduced is 50sccm～100sccm, and the cleaning The time is 5min~10min. 4. The wafer cleaning method according to claim 1, wherein in step S3, the oxidizing gas is a mixed gas of oxygen and nitrogen. 5 . The wafer cleaning method according to claim 4 , wherein the oxygen volume fraction in the oxidizing gas is 10% to 30%. 6 . 6 . The wafer cleaning method according to claim 1 , wherein in step S4 , the reducing gas is a mixed gas of hydrogen and nitrogen or a mixed gas of ammonia and nitrogen. 7 . 7 . The wafer cleaning method according to claim 6 , wherein the reducing gas is a mixed gas of hydrogen and nitrogen, wherein the volume fraction of hydrogen is less than 5%. 8 . 8. The wafer cleaning method according to claim 1, wherein in step S3 and step S4, the vacuum degree of the vacuum chamber is 100mTorr～200mTorr, and the flow rate of the plasma is 50sccm～150sccm.

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