CN110600363A - Method for removing silicon oxide and method for manufacturing semiconductor device - Google Patents

Abstract

The invention provides a method for removing silicon oxide and a method for manufacturing a semiconductor device, wherein the method for removing the silicon oxide comprises the following steps: providing a wafer, wherein the surface of the wafer is provided with a silicon oxide layer to be removed; soaking the wafer in a first etching solution to remove most of the silicon oxide layer; and taking the wafer out of the first etching solution, placing the wafer in a rotating state, and flushing the surface of the wafer by adopting a second etching solution to remove the residual silicon oxide layer. The technical scheme of the invention can completely remove the silicon oxide layer, and avoids influencing the electrical property of the product, thereby avoiding reducing the yield of the product.

Description

Method for removing silicon oxide and method for manufacturing semiconductor device

technical field

The invention relates to the field of integrated circuit manufacturing, in particular to a method for removing silicon oxide and a method for manufacturing semiconductor devices.

Background technique

In the existing 55nm MCU (Micro Controller Unit, MCU) production process, the height of the storage area is greater than the height of the peripheral area, and in order to avoid causing the storage area to be ground in the subsequent chemical mechanical polishing process, the A certain thickness of silicon oxide is deposited on the peripheral area to balance the height difference between the storage area and the peripheral area. After the chemical mechanical polishing process, silicon oxide needs to be removed to avoid affecting the electrical parameters of subsequent devices.

At present, silicon oxide is usually etched and removed by soaking batches of wafers in a hydrofluoric acid bath for a long time. However, the surface of the wafer soaked in hydrofluoric acid is hydrophobic, highly active and unstable, so that the by-product (fluorosilicic acid) of the reaction between hydrofluoric acid and silicon oxide is easily adsorbed back to the wafer surface. round surface, and as the immersion time in the hydrofluoric acid tank increases, the amount of by-products sticking back to the wafer surface will also increase, and the residue of this by-product of the silicon oxide reaction will have a negative impact on the device. The electrical parameters of the chip will be affected, resulting in an increase in the defect rate of the chip.

Therefore, how to completely remove silicon oxide and by-products after the reaction between silicon oxide and hydrofluoric acid to avoid affecting product yield has become an urgent problem to be solved at present.

Contents of the invention

The object of the present invention is to provide a method for removing silicon oxide and a method for manufacturing a semiconductor device, so that the silicon oxide layer can be completely removed, and avoid affecting the electrical properties of products, thereby avoiding a decrease in product yield.

To achieve the above object, the invention provides a method for removing silicon oxide, comprising:

providing a wafer, the surface of the wafer has a silicon oxide layer to be removed;

immersing the wafer in a first etching solution to remove most of the silicon oxide layer;

The wafer is taken out from the first etching solution and placed in a rotating state, and the surface of the wafer is rinsed with a second etching solution to remove the remaining silicon oxide layer.

Optionally, both the first etching solution and the second etching solution are acidic solutions.

Optionally, the first etching solution and the second etching solution are acidic solutions with the same composition and concentration.

Optionally, the acidic solution includes a hydrofluoric acid solution, and the volume ratio of HF to H ₂ O in the hydrofluoric acid solution is 1:100˜1:20.

Optionally, when the wafer is immersed in the first etching solution, it is accompanied by ultrasonic vibration.

Optionally, after taking the wafer out of the first etching solution and before rinsing with the second etching solution, and/or, after rinsing with the second etching solution, A hydrophilic treatment is applied to the surface of the wafer to remove by-products sticking back to the surface of the wafer.

Optionally, the surface of the wafer is washed with SC1 solution or SC2 solution or sequentially with SC1 solution and SC2 solution to perform hydrophilic treatment on the surface of the wafer, wherein the SC1 The solution is a mixture of NH ₄ OH, H ₂ O ₂ and H ₂ O, and the SC2 solution is a mixture of HCl, H ₂ O ₂ and H ₂ O.

Optionally, the volume ratio of NH ₄ OH, H ₂ O ₂ and H ₂ O in the SC1 solution is 1:2:100-1:2:40; the HCl, H ₂ O ₂ in the SC2 solution The volume ratio to H ₂ O is 1:2:100 to 1:2:40.

The present invention also provides a method for manufacturing a semiconductor device, comprising: removing the silicon oxide layer on the surface of a wafer by using the method for removing silicon oxide provided by the present invention.

Optionally, the wafer includes a core area and a peripheral area, the top surface of the core area is higher than the top surface of the peripheral area.

Optionally, the silicon oxide layer is formed on the wafer, and the wafer is chemically mechanically polished to expose the top surface of the core area, and the top surface of the core area is connected to the surface of the peripheral area. The top surface of the silicon oxide layer is flush.

Optionally, the semiconductor device includes a storage array, and the core area is a storage area where the storage array is located.

Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

1. In the method for removing silicon oxide of the present invention, the wafer having the silicon oxide layer to be removed on the surface is soaked in the first etching solution to remove most of the silicon oxide layer; After the wafer is taken out from the first etchant, it is placed in a rotating state, and the surface of the wafer is rinsed with a second etchant to remove the remaining silicon oxide layer, so that the silicon oxide layer can be Complete removal to avoid affecting the electrical properties of the product, thereby avoiding a decrease in product yield.

2, the manufacturing method of semiconductor device of the present invention, owing to adopting the method for removing silicon oxide provided by the present invention, removes the silicon oxide layer on the surface of a wafer, has both avoided the core area of wafer in semiconductor device manufacturing process Being damaged, the silicon oxide layer can be completely removed, so as to avoid affecting the electrical performance of the semiconductor device, thereby avoiding a decrease in the yield rate of the semiconductor device.

Description of drawings

FIG. 1 is a flowchart of a method for removing silicon oxide according to an embodiment of the present invention.

Detailed ways

In order to make the purpose, advantages and features of the present invention more clear, the method for removing silicon oxide and the manufacturing method of the semiconductor device proposed by the present invention will be further described in detail below with reference to FIG. 1 . It should be noted that all the drawings are in a very simplified form and use imprecise scales, and are only used to facilitate and clearly assist the purpose of illustrating the embodiments of the present invention.

An embodiment of the present invention provides a method for removing silicon oxide. Referring to FIG. 1, FIG. 1 is a flowchart of a method for removing silicon oxide according to an embodiment of the present invention. The steps of the method for removing silicon oxide include:

Step S1, providing a wafer, the surface of the wafer has a silicon oxide layer to be removed;

Step S2, immersing the wafer in the first etching solution to remove most of the silicon oxide layer;

Step S3, taking the wafer out of the first etchant and placing it in a rotating state, and washing the surface of the wafer with a second etchant to remove the remaining silicon oxide layer .

The method for removing silicon oxide provided in this embodiment will be described in more detail below.

According to step S1, a wafer is provided, and a silicon oxide layer to be removed is provided on the surface of the wafer. Wherein, the wafer may include a substrate and a film layer structure formed on the substrate. The substrate can be any suitable substrate known to those skilled in the art, for example, it can be at least one of the following materials: silicon (Si), germanium (Ge), silicon germanium (SiGe), carbon Silicon (SiC), silicon germanium carbon (SiGeC), indium arsenide (InAs), gallium arsenide (GaAs), indium phosphide (InP) or other III/V compound semiconductors, including multilayer structures composed of these semiconductors, etc. , or silicon-on-insulator (SOI), silicon-on-insulator (SSOI), silicon-germanium-on-insulator (S-SiGeOI), silicon-germanium-on-insulator (SiGeOI), and germanium-on-insulator (GeOI), or it can also be Double Side Polished Wafers (DSP), can also be ceramic substrates such as alumina, quartz or glass substrates, etc. The film layer structure formed on the wafer is, for example, a gate structure or a dielectric layer, and the gate structure may be a polysilicon gate or a metal gate. It should be noted that the present invention does not limit the structure of the wafer, and a suitable wafer can be selected according to the device to be formed.

The silicon oxide layer plays an auxiliary role in the manufacturing process of the semiconductor device. After the semiconductor structure is manufactured, the silicon oxide layer needs to be removed to avoid affecting the electrical performance of the semiconductor device, thereby avoiding a decrease in the yield of the product .

According to step S2, the wafer is soaked in a first etching solution to remove most of the silicon oxide layer. A batch of wafers may be soaked in the first etching solution to improve production efficiency.

The first etching solution may be an acidic solution, and the acidic solution may include a hydrofluoric acid solution. Wherein, when the hydrofluoric acid solution is soaked to remove the silicon oxide layer, the silicon oxide layer will react with HF in the hydrofluoric acid solution to produce fluosilicic acid as a by-product. At the same time, due to the immersion in the hydrofluoric acid solution, the silicon on the outermost layer of the surface of the wafer is almost terminal with a hydrogen bond, so that the surface of the wafer is hydrophobic, and It has strong activity and instability, so that the produced by-products are easy to stick back to the surface of the wafer; and, when the hydrofluoric acid solution is soaked, the wafer and the hydrofluoric acid The solution is almost at rest, making it easier for by-products to attach to the surface of the wafer. If the by-products are not removed, they will also affect the electrical performance of the wafer, thereby reducing the yield of the product.

The concentration of the hydrofluoric acid solution can be 1:100 to 1:20 (for example, 1:80, 1:50, etc.) by volume ratio of HF to H ₂ O, and the temperature of the hydrofluoric acid solution can be 20°C ~25°C. In addition, the concentration of the hydrofluoric acid solution is not limited to the above concentration range, and the volume ratio of HF can be less or more, and an appropriate concentration can be selected according to production needs. The smaller the volume ratio of HF in the hydrofluoric acid solution, the longer the wafer needs to be soaked in the hydrofluoric acid solution, so that the amount of the silicon oxide layer removed is more , but the longer the immersion time, the more by-products produced by the reaction between the silicon oxide layer and HF; The more by-products produced by the reaction, therefore, it is necessary to comprehensively select the hydrofluoric acid solution with an appropriate concentration.

Most of the thickness of the silicon oxide layer can be removed by soaking in the hydrofluoric acid solution, for example, when the thickness of the silicon oxide layer is , the thickness of the silicon oxide layer removed by soaking in the hydrofluoric acid solution can be at least The remaining thickness of the silicon oxide layer can be removed in other subsequent process steps, so as to avoid the increase of by-products attached to the surface of the wafer caused by soaking in the hydrofluoric acid solution for too long.

And, when soaking batches of the wafers in the hydrofluoric acid solution in order to improve production efficiency, the silicon oxide layer reacts with HF to produce more by-products, and the by-products in the hydrofluoric acid solution The concentration of the product increases, resulting in more by-products adhering to the surface of the wafer.

In addition, when the wafer is soaked in the first etchant, it may be accompanied by ultrasonic vibrations, so as to enhance the strength of the immersion etching to remove the silicon oxide layer, so that the particles of the silicon oxide layer are more easily removed from the silicon oxide layer. The surface of the wafer is detached.

After the wafer is taken out from the first etchant and before being rinsed with the second etchant, the surface of the wafer may be subjected to a hydrophilic treatment to remove sticking back by-products on the surface of the wafer. The step of performing a hydrophilic treatment on the surface of the wafer may include: cleaning the surface of the wafer with an SC1 solution or an SC2 solution or sequentially using an SC1 solution and an SC2 solution, so as to treat the wafer The surface is subjected to hydrophilic treatment, wherein the SC1 solution is a mixture of NH ₄ OH, H ₂ O ₂ and H2O, and the SC2 solution is a mixture of HCl, H ₂ O ₂ and H ₂ O. The temperature of the SC1 solution may be 30°C-80°C, and the volume ratio of NH ₄ OH, H ₂ O ₂ and H ₂ O in the SC1 solution may be 1:2:100-1:2:40 (for example 1:2:80, 1:2:50, etc.); the temperature of the SC2 solution can be 65°C to 85°C, and the volume ratio of HCl, H ₂ O ₂ and H ₂ O in the SC2 solution can be 1:2:100～1:2:40 (for example, 1:2:80, 1:2:50, etc.).

In the process of cleaning the surface of the wafer with the SC1 solution, the SC1 solution makes the surface of the wafer continuously maintain hydrophilicity, so that the surface of the wafer adheres back By-products can be removed. Specifically, due to the action of H ₂ O ₂ , a hydrophilic natural oxide film (SiO ₂ ) will be formed on the surface of the wafer, so that the surface of the wafer and the by-product can be soaked by the SC1 solution; and, since the natural oxide film of the surface of the wafer and the silicon of the surface of the wafer are corroded by NH ₄ OH, the The by-products on the surface fall into the SC1 solution, thereby achieving the purpose of removing the by-products; and, while NH ₄ OH corrodes the surface of the wafer, H ₂ O ₂ is on the surface of the wafer A new hydrophilic natural oxide film is formed, so that the surface of the wafer remains hydrophilic.

In the process of using the SC2 solution to clean the surface of the wafer, since the SC2 solution is an acidic solution with strong oxidizing properties, it will also form a hydrophilic natural oxide film on the surface of the wafer, Thus, the space between the surface of the wafer and the by-products can be saturated by the SC2 solution, thereby allowing the by-products to be cleaned and removed.

In addition, the SC1 solution can also remove other impurity particles on the surface of the wafer, and the SC2 solution can also remove metal contamination such as sodium, iron, and magnesium on the surface of the wafer.

According to step S3, the wafer is taken out from the first etching solution and placed in a rotating state, and the surface of the wafer is rinsed with a second etching solution to remove the remaining silicon oxide Floor. The second etching solution can also be an acidic solution, and the second etching solution can be an acidic solution with the same composition and concentration as the first etching solution, that is, the second etching solution can also be A solution of hydrofluoric acid may be included. For the concentration of the hydrofluoric acid solution, refer to the above step S2, which will not be repeated here.

After rinsing with the hydrofluoric acid solution of the second etchant, the problem of by-product sticking back to the surface of the wafer may also arise. However, the rest of the silicon oxide layer is removed by rinsing, and the wafer is in a rotating state, so that most of the by-products will be removed from the wafer under the action of rinsing and the centrifugal force of rotation. The surface is carried away. Therefore, the amount of by-products sticking back on the surface of the wafer caused by rinsing the surface of the wafer with the hydrofluoric acid solution of the second etching solution is far less than that with the first etching solution. An amount of by-products sticking back on the surface of the wafer caused by soaking the wafer in the hydrofluoric acid solution of the etchant.

In order to avoid too long soaking time in the hydrofluoric acid solution of the first etching solution causing too much by-products attached to the surface of the wafer, and in order to make the remaining oxidation on the surface of the wafer The silicon layer can be completely removed by the hydrofluoric acid solution of the second etching solution, and the thickness of the silicon oxide layer removed by the hydrofluoric acid solution of the second etching solution can be controlled to be no more than

Moreover, the hydrofluoric acid solution of the second etching solution can also remove the natural oxide film produced when the SC1 solution and the SC2 solution in the above step S2 perform hydrophilic treatment on the surface of the wafer, and inhibit Formation of a new natural oxide film.

In addition, the hydrophilic treatment may not be performed on the surface of the wafer after the above step S2, and the surface of the wafer may be treated directly after rinsing with the second etching solution in step S3. The surface is subjected to a hydrophilic treatment to combine the by-products sticking back on the surface of the wafer in the above step S2 and the by-products sticking back on the surface of the wafer in step S3 remove. Alternatively, after the wafer is taken out of the first etching solution in the above-mentioned step S2 and after being rinsed with the second etching solution in the step S3, all parts of the wafer may be Hydrophilic treatment is carried out on the above-mentioned surface to avoid the problem of slow removal rate and incomplete removal caused by excessive accumulation of by-products.

The step of hydrophilically treating the surface of the wafer after rinsing with the second etching solution may also include: cleaning the wafer with an SC1 solution or an SC2 solution or sequentially using an SC1 solution and an SC2 solution. rounding the surface to remove by-products sticking back to the surface of the wafer. Wherein, the SC1 solution is a mixture of NH ₄ OH, H ₂ O ₂ and H ₂ O, and the SC2 solution is a mixture of HCl, H ₂ O ₂ and H ₂ O. For the concentration of the SC1 solution and the SC2 solution and the principle of removing by-products, refer to the above step S2, which will not be repeated here.

In addition, placing the wafer in a rotating state and rinsing the surface of the wafer not only enables the silicon oxide layer and by-products at each position of the surface of the wafer to be is cleaned, and under the action of the rotating centrifugal force, the particles of the silicon oxide layer and the particles of the by-products are more likely to detach from the surface of the wafer and fall out, further making the silicon oxide layer and by-products The product can be completely removed.

In addition, each step in the above method for removing silicon oxide is not limited to the above formation sequence, and the sequence of each step can be adjusted adaptively.

In summary, the method for removing silicon oxide provided by the present invention includes: providing a wafer, the surface of the wafer has a silicon oxide layer to be removed; immersing the wafer in the first etching solution , to remove most of the silicon oxide layer; taking the wafer out of the first etching solution and placing it in a rotating state, and using a second etching solution to rinse the surface of the wafer, to remove the remaining silicon oxide layer. The method for removing silicon oxide provided by the present invention enables the silicon oxide layer to be completely removed, avoiding affecting the electrical properties of products, thereby avoiding a decrease in product yield.

An embodiment of the present invention provides a method for manufacturing a semiconductor device, comprising: removing the silicon oxide layer on the surface of a wafer by using the method for removing silicon oxide provided by the present invention (that is, the above step S1 to step S3). The wafer includes a core region and a peripheral region, the top surface of the core region being higher than the top surface of the peripheral region. In order to avoid damage to the core region during the subsequent semiconductor device manufacturing process (for example, chemical mechanical polishing of the semiconductor device may cause damage to the high core region), a layer of silicon oxide with a certain thickness will be deposited on the peripheral region, To balance the height difference between the core area and the peripheral area. The silicon oxide layer plays a role in assisting the manufacture of the semiconductor structure during the manufacturing process of the semiconductor device, and the silicon oxide layer needs to be removed after the semiconductor structure is manufactured.

The silicon oxide layer is formed on the wafer, and the wafer is chemically mechanically polished to expose the top surface of the core area, so that the top surface of the core area is in contact with the surface of the peripheral area. The top surface of the silicon oxide layer is flush.

Specifically, on the one hand, the silicon oxide layer can be formed on the peripheral region, so that the top surface of the core region is lower than the top surface of the silicon oxide layer or flush with the top surface of the silicon oxide layer . When the top surface of the core area is lower than the top surface of the silicon oxide layer, before immersing the wafer in the first etchant, first use a chemical mechanical polishing process on the peripheral area The silicon oxide layer is thinned so that the top surface of the core area is flush with the top surface of the silicon oxide layer on the peripheral area. On the other hand, the silicon oxide layer can be formed on both the peripheral region and the core region, and before the wafer is immersed in the first etching solution, the chemical mechanical polishing process is first used to polish the silicon oxide layer. The silicon oxide layer on the core area and the peripheral area is thinned until the top surface of the core area is exposed, and the layer under the silicon oxide layer in the core area may be a film of the core area layer structure.

In this embodiment, the semiconductor device may include a storage array, and the core area is a storage area where the storage array is located. After performing the process step of forming a film structure on the core area and/or the peripheral area, the silicon oxide layer on the surface of the wafer is removed by using the above steps S1 to S3, so that silicon oxide The layer can be completely removed, so as to avoid affecting the electrical performance of the semiconductor device, thereby avoiding a decrease in the yield rate of the semiconductor device.

The above description is only a description of the preferred embodiments of the present invention, and does not limit the scope of the present invention. Any changes and modifications made by those of ordinary skill in the field of the present invention based on the above disclosures shall fall within the protection scope of the claims.

Claims (12)

1. A method of removing silicon oxide, comprising:

providing a wafer, wherein the surface of the wafer is provided with a silicon oxide layer to be removed;

soaking the wafer in a first etching solution to remove most of the silicon oxide layer;

and taking the wafer out of the first etching solution, placing the wafer in a rotating state, and flushing the surface of the wafer by adopting a second etching solution to remove the residual silicon oxide layer.

2. The method for removing silicon oxide according to claim 1, wherein the first etching liquid and the second etching liquid are both acidic solutions.

3. The method for removing silicon oxide according to claim 2, wherein the first etching liquid and the second etching liquid are acidic solutions having the same composition and concentration.

4. The method for removing silicon oxide according to claim 2 or 3, wherein the acidic solution comprises a hydrofluoric acid solution in which HF and H are contained₂The volume ratio of O is 1: 100-1: 20.

5. The method for removing silicon oxide according to claim 1, wherein the wafer is immersed in the first etching solution accompanied by ultrasonic vibration.

6. The method for removing silicon oxide according to claim 1, wherein the surface of the wafer is subjected to hydrophilic treatment after the wafer is taken out of the first etching solution and before rinsing with the second etching solution, and/or after rinsing with the second etching solution, to remove by-products that are back-adhered to the surface of the wafer.

7. The method of claim 6, wherein the surface of the wafer is subjected to a hydrophilic treatment by cleaning the surface of the wafer with a solution SC1, a solution SC2, a solution SC1 and a solution SC2 in sequence, wherein the solution SC1 is NH₄OH、H₂O₂And H₂O, the SC2 solution is HCl and H₂O₂And H₂And (3) a mixed solution of O.

8. The method for removing silicon oxide according to claim 7, wherein NH in the SC1 solution₄OH、H₂O₂And H₂The volume ratio of O is 1:2: 100-1: 2: 40; HCl and H in the SC2 solution₂O₂And H₂The volume ratio of O is 1:2: 100-1: 2: 40.

9. A method of manufacturing a semiconductor device, comprising: removing the silicon oxide layer on the surface of a wafer by using the method for removing silicon oxide according to any one of claims 1 to 8.

10. The method of manufacturing a semiconductor device according to claim 9, wherein the wafer comprises a core region and a peripheral region, a top surface of the core region being higher than a top surface of the peripheral region.

11. The method of claim 10, wherein the silicon oxide layer is formed on the wafer, and the wafer is subjected to chemical mechanical polishing to expose a top surface of the core region, the top surface of the core region being flush with a top surface of the silicon oxide layer on the peripheral region.

12. The method for manufacturing a semiconductor device according to claim 10 or 11, wherein the semiconductor device includes a memory array, and the core region is a memory region in which the memory array is located.