Manufacturing method of wafer back metal layer

Abstract

The invention provides a method for manufacturing a back metal layer of a wafer, which comprises the following steps of: providing a semiconductor device wafer to be subjected to a back process and wet processing equipment for processing the back morphology of the wafer, a treatment tank of the wet treatment equipment contains a corrosive liquid at least comprising a first component, a second component, a third component and a fourth component, and the proportion range of the first component, the second component and the third component in the corrosive liquid is (6-8): (1-3): 1; placing the wafer in a processing tank and processing the wafer at a preset temperature for a preset time; and forming a back metal layer on the back surface of the processed wafer. According to the method, the back metal layer is formed after the back surface of the wafer is treated by the corrosive liquid with the proportion range of the first component, the second component and the third component being (6-8): (1-3): 1, so that the problem of stripping of the back metal layer is solved, and the reliability and the yield of the semiconductor device are improved.

Description

Technical Field

[0001] The invention belongs to the field of semiconductor integrated circuit manufacturing and relates to a method for manufacturing a wafer back metal layer. Background Art

[0002] With the development of electronic technology, semiconductor devices are widely used in electronic devices. However, in the current production process of high-voltage semiconductor devices such as metal oxide semiconductor field effect transistors (MOS) and insulated gate bipolar transistors (IGBT), there is a problem of easy peeling of the back metal layer of the device, resulting in a low yield of the device. In addition, during the use of the device by customers, the back metal layer will also peel off, seriously affecting the reliability of the device. According to statistics, a mixed solution of nitric acid, hydrofluoric acid and distilled water is used as an etching solution for treating the back of the wafer, and the volume ratio of nitric acid, hydrofluoric acid and distilled water in the etching solution is 7:1:2 (wherein the concentration of nitric acid is 69% and the concentration of hydrofluoric acid is 49%), and the back metal layer is deposited after the etching solution is used to treat the back of the wafer. The number of back metal layer peeling of the semiconductor device accounts for about 1% of the actual output, affecting the market share of the product.

[0003] Therefore, there is an urgent need to find a method for manufacturing a wafer back metal layer that can improve back metal layer peeling and enhance the reliability of semiconductor devices. Summary of the invention

[0004] In view of the above-mentioned shortcomings of the prior art, an object of the present invention is to provide a method for manufacturing a wafer back metal layer, so as to solve the problem in the prior art that the back metal layer of semiconductor devices is severely peeled off, resulting in poor reliability of the devices.

[0005] To achieve the above-mentioned object and other related objects, the present invention provides a method for manufacturing a wafer back metal layer, comprising:

[0006] A semiconductor device wafer to be processed on the back side and a wet processing device for processing the back side morphology of the wafer are provided, wherein a processing tank of the wet processing device contains an etching liquid comprising at least a first component, a second component, a third component and a fourth component, wherein the ratio of the first component, the second component and the third component in the etching liquid is in the range of (6-8):(1-3):1;

[0007] Placing the wafer in the processing tank and treating it at a preset temperature for a preset time;

[0008] A back metal layer is formed on the back side of the processed wafer.

[0009] Optionally, the first component includes sulfuric acid; the second component includes nitric acid; and the third component includes hydrofluoric acid.

[0010] Optionally, the etching liquid further contains a fifth component, and the ratio of the amount of the third component to the amount of the fifth component in the etching liquid is not less than 1.

[0011] Optionally, the fifth component comprises acetic acid.

[0012] Optionally, the processing tank is further provided with a diffusion pipeline which enables the exhaust speed of the gas generated by the reaction between the etching solution and the wafer to reach a preset diffusion speed.

[0013] Optionally, the preset diffusion rate ranges from 4 L / min to 6 L / min.

[0014] Optionally, the process of processing the wafer also includes a step of shaking the wafer.

[0015] Optionally, the frequency range of shaking the wafer is 18 times / min to 22 times / min.

[0016] Optionally, the preset temperature ranges from 16°C to 24°C; and the preset time ranges from 2min to 5min.

[0017] Optionally, after processing the back side of the wafer and before forming the back metal layer, the method further includes detecting the roughness of the back side of the wafer and retaining the wafers whose back side roughness is less than a preset roughness.

[0018] As described above, the method for manufacturing the back metal layer of the wafer of the present invention improves the process for manufacturing and processing the back side of the wafer, and uses the etching solution including the first component, the second component, the third component and the fourth component to process the back side of the wafer, wherein the ratio of the first component, the second component and the third component in the etching solution is in the range of (6-8):(1-3):1, and the temperature for processing the wafer is the preset temperature. At the same time, during the processing of the wafer, the diffusion speed of the generated gas is controlled to the preset diffusion speed, and the wafer is shaken, thereby improving the roughness of the back side of the wafer, and improving the bonding strength between the back metal layer and the back side of the wafer, thereby improving the problem of peeling of the back metal layer in the semiconductor device, improving the yield and reliability of the semiconductor device, and having a high industrial utilization value. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Shown is a process flow chart of the method for manufacturing a wafer back metal layer of the present invention.

[0020] Figure 2 The table shows the corrosion effects of the etching solutions of several combinations of components in the method for making the wafer back metal layer of the present invention.

[0021] Figure 3 Display as Figure 2 A local microscopic image of the back side of the wafer after being treated with the fifth group of etching solutions.

[0022] Figure 4 Display as Figure 2 The appearance of the back side of the wafer after being treated with the fifth set of etching liquid.

[0023] Figure 5 Shown is a partial microscopic image of the back side of the wafer after treatment with a universal etching solution.

[0024] Figure 6 Shown is the appearance of the back side of the wafer after being treated with a general-purpose etching solution.

[0025] Figure 7 The method for manufacturing the wafer back metal layer of the present invention is shown as follows: Figure 2 Statistical table of thrust and film inversion test results of wafers treated with the fifth group of etching solutions and general etching solutions. DETAILED DESCRIPTION

[0026] The following describes the embodiments of the present invention through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention.

[0027] See also Figures 1 to 7 It should be noted that the illustrations provided in this embodiment are only used to illustrate the basic concept of the present invention in a schematic manner, and the drawings only show components related to the present invention rather than being drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component may be changed arbitrarily, and the component layout may also be more complicated.

[0028] This embodiment provides a method for manufacturing a wafer back metal layer. Figure 1 FIG. 1 is a process flow chart of a method for manufacturing a wafer back metal layer, comprising the following steps:

[0029] S1: providing a semiconductor device wafer to be processed on the back side and a wet processing device for processing the back side morphology of the wafer, wherein a processing tank of the wet processing device contains an etching liquid comprising at least a first component, a second component, a third component and a fourth component, wherein the ratio of the first component, the second component and the third component in the etching liquid is in the range of (6-8):(1-3):1;

[0030] S2: placing the wafer in the processing tank and treating it at a preset temperature for a preset time;

[0031] S3: forming a back metal layer on the back side of the processed wafer.

[0032] Specifically, please perform the steps S1 and S2: provide a semiconductor device wafer to be processed on the back side and a wet processing device for processing the back side morphology of the wafer, wherein the processing tank of the wet processing device contains an etching liquid including at least a first component, a second component, a third component and a fourth component, and the ratio of the first component, the second component and the third component in the etching liquid is in the range of (6-8):(1-3):1; place the wafer in the processing tank and process it at a preset temperature for a preset time. The ratio here refers to the volume ratio of the first component, the second component and the third component used to prepare the etching liquid.

[0033] Specifically, the semiconductor device in the wafer is a wafer to be processed by a back metal process, and the semiconductor device may be a MOS device, an IGBT device, a diode device, a triode device or other suitable semiconductor devices.

[0034] Specifically, the size and shape of the wafer are related to the front-end process and will not be elaborated here.

[0035] Specifically, the material of the back surface layer of the wafer includes silicon, silicon carbide or other suitable materials. In this embodiment, the material of the back surface layer of the wafer is silicon.

[0036] Specifically, the wet processing equipment is a wet etching equipment commonly used in the semiconductor device manufacturing process, which will not be described in detail here.

[0037] Specifically, the amount of the etching solution in the processing tank can be selected according to actual conditions while ensuring the morphology of the back side of the wafer, and is not limited here. Preferably, the back side of the wafer in the processing tank is immersed in the etching solution.

[0038] As an example, the first component includes sulfuric acid or other suitable acidic corrosive components; the second component includes nitric acid or other suitable acidic corrosive components; the third component includes hydrofluoric acid or other suitable acidic corrosive components. In this embodiment, the first component is concentrated sulfuric acid with a concentration of 98%, the second component is fuming nitric acid with a concentration of 69%, and the third component is hydrofluoric acid with a concentration of 49%.

[0039] Specifically, the fourth component is an activator, which is used to enhance the dispersion characteristics of the first component, the second component and the third component, so that the first component, the second component and the third component in the etching solution are distributed more evenly.

[0040] Specifically, under the condition of ensuring the performance of the etching liquid, the material of the fourth component and the amount of the fourth component in the etching liquid can be selected according to actual conditions, and are not limited here.

[0041] As an example, the etching solution further contains a fifth component, and the ratio of the amount of the third component to the amount of the fifth component in the etching solution is not less than 1. The amount here refers to the volume of the corresponding component used to prepare the etching solution.

[0042] As an example, the fifth component includes acetic acid or other suitable acidic etchant components. Preferably, 100% acetic acid is used as the fifth component.

[0043] Specifically, the method of placing the wafer in the processing tank includes mechanical transfer or other suitable methods. In this embodiment, the wafer is transferred to the processing tank by a wafer rack, and the wafer rack does not react with the etching solution during the processing.

[0044] As an example, the preset temperature ranges from 16° C. to 24° C. Preferably, the preset temperature is 20° C.

[0045] Specifically, by setting the temperature of the etching liquid at the preset temperature, the etching liquid can have a better treatment effect.

[0046] As an example, the processing tank is further provided with a diffusion pipeline which enables the exhaust speed of the gas generated by the reaction between the etching solution and the wafer to reach a preset diffusion speed.

[0047] Specifically, the material, size and shape of the diffusion pipeline can be selected according to actual conditions while ensuring that the diffusion pipeline does not react with the corrosive liquid and the exhaust effect during the wafer processing process is ensured, and no limitation is imposed here. Preferably, a pipeline made of Teflon is used as the diffusion pipeline.

[0048] As an example, the preset diffusion speed ranges from 4L / min to 6L / min. Preferably, the preset diffusion speed is 5L / min. The diffusion speed here refers to the diffusion speed of the gas generated during the processing of a batch of wafers.

[0049] Specifically, by setting up the diffusion pipeline, the discharge speed of the gas generated by the reaction between the etching solution and the wafer can be increased to avoid the untimely discharge of the gas generated during the processing, which affects the processing effect on the back of the wafer.

[0050] As an example, the process of processing the wafer also includes a step of shaking the wafer.

[0051] Specifically, in the process of processing the wafer, by shaking the wafer, it can be ensured that the concentration of each component of the etching liquid at the point where the back side of the wafer contacts the etching liquid is within a preset range, so as to avoid the concentration of the etching liquid in this area being slightly lower than the concentration in other areas due to the reaction between the back surface of the wafer and the etching liquid.

[0052] As an example, the frequency of shaking the wafer ranges from 18 times / min to 22 times / min. Preferably, during the processing of the wafer, the frequency of shaking the wafer is 20 times / min.

[0053] Specifically, a shaking device is also provided on the carrier that carries the wafer, so as to achieve small-amplitude shaking of the wafer and control of the shaking frequency of the wafer during processing of the wafer.

[0054] Specifically, under the condition of ensuring the processing effect on the back side of the wafer, the structure and size of the shaking device can be selected according to actual conditions and are no longer restricted here; the shaking method of the wafer implemented by the shaking device can be selected according to actual conditions. For example, the shaking device can be used to control the small rise and fall of the wafer to make the wafer produce a shaking effect.

[0055] Specifically, the wafer carrier is also provided with a safety device to prevent the wafer from slipping, so as to avoid the wafer from slipping off the wafer carrier during shaking. The structure and shape of the safety device can be selected according to actual conditions.

[0056] As an example, the preset time ranges from 2 minutes to 5 minutes.

[0057] Specifically, the preset time is related to the processing temperature, the concentration of each component in the etching solution and the roughness requirement of the back side of the wafer during the processing of the wafer. While ensuring the processing effect of the back side of the wafer, the preset time can also be other suitable time.

[0058] Specifically, the back side of the wafer is processed so that the roughness of the back side of the wafer reaches a preset value, thereby facilitating the formation of a metal film layer on the back side of the wafer, while at the same time ensuring that there is better bonding between the back side of the wafer and the metal film layer, thereby preventing the metal film layer from falling off and affecting the yield and reliability of semiconductor devices.

[0059] See also Figures 2 to 7 , executing step S3: forming a back metal layer on the back side of the processed wafer.

[0060] As an example, after processing the back side of the wafer and before forming the back metal layer, the method further includes detecting the roughness of the back side of the wafer and retaining the wafer whose back side roughness is less than a preset roughness.

[0061] Specifically, by performing roughness detection on the back side of the wafer after processing and before forming the back metal layer, and intercepting the wafer whose back side roughness does not meet the standard, the wafer that does not meet the standard is prevented from flowing into the process of forming the back metal layer, thereby ensuring the yield of subsequent processes.

[0062] Specifically, after the back side of the wafer is processed, the roughness of the back side of the wafer is not less than 0.17 μm.

[0063] Specifically, Figure 2 As shown, it is a statistical table of the corrosion effects of several combinations of etching solutions, wherein the amount of etching solution in each group is the same and the wafers processed are all from the same batch, the number of wafers processed by each group of etching solution is the same, the parameters in the processing process are the same, and the concentration of sulfuric acid used in each group is 98%, the concentration of nitric acid is 69%, the concentration of acetic acid is 100%, and the concentration of hydrofluoric acid is 49%. The values ​​in the table are the volume ratios of each component. It can be seen from the statistical table that the roughness of the back of the wafer after being processed by the etching solution in each group meets the standard, but the back of the wafer after being processed will have an abnormal appearance. In the process of each group of etching solution processing the back of the wafer, the diffusion pipeline is added and the wafer is shaken 20 times / min, and the flow rate of the diffused CO2 gas is 5L / min. After the etching solution in the fifth group is processed, no abnormal appearance occurs, and the roughness of the back of the wafer after being processed is between 0.3μm and 0.5μm, and the line mark TTV is less than 0.2μm.

[0064] Specifically, Figure 3 , Figure 4 , Figure 5 and Figure 6 As shown, they are Figure 2 The local microscopic image of the back of the wafer after being treated with the fifth group of etching solutions. Figure 2 The appearance of the back of the wafer after being treated with the fifth group of etching solutions, the local microscopic picture of the back of the wafer after being treated with the universal etching solution, and the appearance of the back of the wafer after being treated with the universal etching solution. Among them, the main components of the universal etching solution are nitric acid, hydrofluoric acid and distilled water (nitric acid: hydrofluoric acid: water = 7:1:2, where the ratio is the volume ratio, wherein the concentration of nitric acid is 69%, and the concentration of hydrofluoric acid is 49%). In the process of treating the back of the wafer, all processing parameters are the same, and the processed wafers are from the same batch of wafers. It can be seen from the figure that the corrosion marks on the back of the wafer after being treated with the fifth group of etching solutions are evenly distributed, there are no grinding knife marks, and the appearance color is uniform, and Figure 4 The corrosion marks on the back of the wafer are unevenly distributed, have grinding knife marks, and the appearance color is uneven.

[0065] Specifically, the method of forming the back metal layer includes magnetron sputtering, evaporation, physical vapor deposition, chemical vapor deposition, metal compound vapor deposition, molecular beam epitaxy, atomic vapor deposition, atomic layer deposition or other suitable methods.

[0066] Specifically, the material of the back metal layer includes titanium, titanium nitride, silver, gold, copper, aluminum, nickel, tungsten, platinum or other suitable conductive materials.

[0067] Specifically, under the condition of ensuring the performance of the semiconductor device, the thickness of the back metal layer can be selected according to actual conditions and is not limited here.

[0068] Specifically, Figure 7 As shown, after the back metal layer is formed Figure 2 The thrust and film inversion test results of the wafers treated with the etching solution and the general etching solution in the fifth group are shown in the statistical table. During the treatment process, a diffusion pipeline is added and the wafer is shaken 20 times / min. The flow rate of the diffused CO2 gas is 5L / min. The test positions are the upper, middle, lower, left and right areas of the wafer. It can be seen from the statistical table that Figure 3 The thrust strength of the wafer in Figure 5 The thrust of the wafer, and during the film inversion test, Figure 3 The back metal layer on the back of the wafer did not fall off, indicating that the peeling problem of the back metal layer of the wafer was improved.

[0069] Specifically, the back side of the wafer is treated with the etching liquid, and during the treatment process, the diffusion rate of the generated gas reaches a preset diffusion rate, and the wafer is shaken at the same time, so that the concentration of the etching liquid in each area on the back side of the wafer changes less, thereby making the roughness fluctuation of the back side of the wafer smaller and the appearance color uniform.

[0070] Specifically, by using the etching solution to process the back side of the wafer and then forming the back metal layer, the probability of the back metal layer peeling off is reduced to one millionth, thereby improving the yield of semiconductor devices.

[0071] Specifically, by using the etching solution including the first component, the second component, the third component and the fourth component to treat the back side of the wafer, and the ratio of the first component, the second component and the third component in the etching solution is in the range of (6-8):(1-3):1, the roughness of the back side of the wafer is improved, and the bonding strength between the back metal layer and the back side of the wafer is improved, thereby improving the problem of peeling of the back metal layer of the semiconductor device and improving the reliability of the semiconductor device.

[0072] In summary, the method for making a wafer back metal layer of the present invention improves the back side treatment process before forming the back metal layer, uses a etching solution including a first component, a second component, a third component and a fourth component to treat the back side of the wafer, and the ratio of the first component, the second component and the third component in the etching solution is in the range of (6-8):(1-3):1, and at the same time, in the process of treating the back side of the wafer, the diffusion speed of the generated gas is controlled to a preset diffusion speed, and the wafer is shaken, thereby improving the roughness of the back side of the wafer, improving the bonding strength between the back metal layer and the back side of the wafer, and reducing the probability of the back metal layer peeling off to one in a million, thereby improving the problem of the back metal layer peeling off of the semiconductor device, and improving the yield and reliability of the semiconductor device. Therefore, the present invention effectively overcomes the various shortcomings in the prior art and has a high industrial utilization value.

[0073] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. A method for manufacturing a wafer back metal layer, characterized in that: The following steps are involved: A semiconductor device wafer to be processed on the back side and a wet processing device for processing the back side morphology of the wafer are provided. The processing tank of the wet processing device contains an etching liquid including at least a first component, a second component, a third component and a fourth component. The ratio of the first component, the second component and the third component in the etching liquid is in the range of (6 to 8): (1～3):1； Placing the wafer in the processing tank and treating it at a preset temperature for a preset time; A back metal layer is formed on the back side of the processed wafer.

2. The method for manufacturing a wafer back metal layer according to claim 1, characterized in that: The first component includes sulfuric acid; The second component includes nitric acid; and the third component includes hydrofluoric acid.

3. The method for manufacturing a wafer back metal layer according to claim 1, characterized in that: The etching liquid further contains a fifth component, and the ratio of the amount of the third component to the amount of the fifth component in the etching liquid is not less than 1.

4. The method for manufacturing a wafer back metal layer according to claim 3, characterized in that: The fifth component includes acetic acid.

5. The method for manufacturing a wafer back metal layer according to claim 1, characterized in that: The processing tank is also provided with a diffusion pipeline which enables the exhaust speed of the gas generated by the reaction between the etching solution and the wafer to reach a preset diffusion speed.

6. The method for manufacturing a wafer back metal layer according to claim 5, characterized in that: The preset diffusion rate ranges from 4 L / min to 6 L / min.

7. The method for manufacturing a wafer back metal layer according to claim 1, characterized in that: The process of processing the wafer also includes a step of shaking the wafer.

8. The method for manufacturing a wafer back metal layer according to claim 7, characterized in that: The frequency range of shaking the wafer is 18 times / min to 22 times / min.

9. The method for manufacturing a wafer back metal layer according to claim 1, characterized in that: The preset temperature ranges from 16°C to 24°C; the preset time ranges from 2min to 5min.

10. The method for manufacturing a wafer back metal layer according to claim 1, characterized in that: After processing the back side of the wafer and before forming the back metal layer, the method further includes the steps of detecting the roughness of the back side of the wafer and intercepting the wafer whose back side roughness is less than a preset roughness.

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