A semiconductor silicon wafer thinning etching solution, preparation method and application thereof

Abstract

The present invention provides a semiconductor silicon wafer thinning etching solution, a preparation method and application thereof, wherein the semiconductor silicon wafer thinning etching solution comprises the following components in weight proportion: 10-15 parts of hydrofluoric acid; 5-10 parts of nitric acid; 2-4 parts of a negatively charged complexing agent; 0.1-1 parts of a positively charged organosilicon surfactant; 15-30 parts of ultrapure water, wherein the positively charged organosilicon surfactant is a pyridine-modified organosilicon surfactant. The present invention also discloses a preparation method and application of the semiconductor silicon wafer thinning etching solution. The semiconductor silicon wafer thinning etching solution of the present invention has the characteristics of fast etching rate, moderate and uniform surface roughness of the semiconductor silicon wafer after etching, and strong adhesion to electroplated copper, and can be widely used in the semiconductor manufacturing industry, and is particularly suitable for thinning the back of P-type silicon.

Description

Technical Field

[0001] The invention relates to etching liquid technology, in particular to a semiconductor silicon wafer thinning etching liquid, and a preparation method and application thereof. Background Art

[0002] Backside thinning of silicon wafers is an important semiconductor manufacturing process that aims to remove excess material from the back of silicon wafers to reduce the packaging volume of silicon wafers, reduce thermal resistance, improve the heat dissipation performance of devices, and reduce the risk of chip cracking due to uneven heating after packaging, thereby improving product reliability. The backside thinning of silicon is divided into mirror thinning and rough surface thinning. Mirror thinning is for better contact between the upper and lower wafers for technical interconnection such as through silicon vias; while rough surface thinning is for the subsequent electroplating of metal layers to make the metal have better adhesion on the silicon surface.

[0003] Thinned silicon wafers have many advantages, such as significantly improved mechanical and electrical properties. The thinner the silicon wafer, the better its flexibility and the less stress caused by external impact. In addition, the thinned chip has better thermal conductivity, which helps to improve the chip's heat dissipation efficiency, thereby extending the chip's service life.

[0004] Silicon wafer backside thinning technologies include grinding, polishing, dry polishing, electrochemical etching, wet etching, plasma-assisted chemical etching, and atmospheric pressure plasma etching. Among them, grinding technology is a high-efficiency, low-cost thinning technology that thins silicon wafers by rotating a grinding wheel on the surface of the silicon wafer to apply pressure, damage, break, and remove. However, the damage introduced by this method may reduce the reliability and stability of the device. In addition, during the thinning process, the back of the silicon wafer may be damaged, resulting in a rough surface or even warping.

[0005] With the advancement of semiconductor technology, thinning technology is also constantly being updated and optimized. For example, modern thinning systems mostly use silicon wafer self-rotation grinding technology. This method rotates a single wafer and feeds the knife vertically downward for grinding, which can more finely control the thinning process and reduce the occurrence of edge collapse.

[0006] Silicon wafer backside thinning is a key semiconductor manufacturing technology that not only helps improve chip performance and reliability, but also promotes the development of thinner and shorter microelectronic products. With the advancement of technology, thinning technology needs to continue to evolve to meet higher performance requirements and market demands. Summary of the invention

[0007] The purpose of the present invention is to provide a semiconductor silicon wafer thinning etching solution in response to the increasing demand for silicon wafer thinning technology. The etching solution has the characteristics of fast etching rate, moderate and uniform surface roughness of the semiconductor silicon wafer after etching, and strong adhesion to electroplated copper. The etching solution can be widely used in the semiconductor manufacturing industry, especially suitable for P-type silicon back thinning.

[0008] It should be noted that, in the present invention, unless otherwise specified, the specific meaning of "including" in relation to composition limitations and descriptions includes both open-ended "including", "comprising" and similar meanings, and closed-ended "consisting of..." and similar meanings.

[0009] To achieve the above object, the technical solution adopted by the present invention is: a semiconductor silicon wafer thinning etching solution, comprising the following components in weight proportions:

[0010] 10-15 parts of hydrofluoric acid;

[0011] 5-10 parts of nitric acid;

[0012] 2-4 parts of a negatively charged complexing agent;

[0013] 0.1-1 part of positively charged silicone surfactant;

[0014] 15-30 parts of ultrapure water;

[0015] The positively charged organosilicon surfactant is a pyridine-modified organosilicon surfactant.

[0016] Furthermore, the hydrofluoric acid is 10-12 parts.

[0017] Furthermore, the nitric acid is 6-8 parts.

[0018] Furthermore, the negatively charged complexing agent is one or more of ammonium thiocyanate, potassium thiocyanate, sodium thiocyanate and potassium bifluoride.

[0019] Furthermore, the negatively charged complexing agent is preferably potassium bifluoride.

[0020] Furthermore, the negatively charged complexing agent is 2.5-3.5 parts.

[0021] Furthermore, the ultrapure water is 20-25 parts.

[0022] Furthermore, the positively charged organosilicon surfactant is 0.2-0.6 parts.

[0023] Furthermore, the structural formula of the pyridyl-modified silicone surfactant is as shown in Formula I:

[0024]

[0025] Formula I;

[0026] In Formula I, n is an integer of 1000-2000, and m is an integer of 10-100.

[0027] Organosilicon surfactants are usually composed of organosilicon chains containing silicon atoms, which can be modified by different methods, including the introduction of organic groups. However, there are no reports of organosilicon surfactants that directly carry positive charges, because silicon atoms themselves are neutral and organic groups usually do not carry enough positive charges to make the entire molecule positively charged. The present invention introduces a pyridine group, an organic group with positive charge, into the organosilicon chain through a chemical reaction to make the entire molecule positively charged.

[0028] The synthesis method of the pyridine-modified organosilicon surfactant is as follows:

[0029] S1. Add allyl polyether, chloroplatinic acid, pyridine and hydrogenated silicone oil into a container filled with nitrogen, and stir the reaction at room temperature for 1-3 hours;

[0030] S2. Raise the temperature to 80-100° C. and continue the reaction for 5-8 hours to obtain an organosilicon surfactant containing a pyridine group, i.e., a pyridine-modified organosilicon surfactant.

[0031] Furthermore, the molar ratio of the pyridine, hydrogen-containing silicone oil, allyl polyether and chloroplatinic acid is 6.5-13.5:1:1:0.2-0.5.

[0032] Furthermore, the molar ratio of pyridine, hydrogen-containing silicone oil, allyl polyether and chloroplatinic acid is preferably 9.5:1:1:0.25.

[0033] Furthermore, the hydrogen-containing silicone oil is methyl hydrogen-containing silicone oil.

[0034] Furthermore, the viscosity of the methyl hydrogen silicone oil is 5-100 cst.

[0035] Furthermore, the S1 is stirred and reacted at room temperature for 1 hour.

[0036] Furthermore, the temperature of S2 is raised to 80° C. and the reaction is continued for 5 hours.

[0037] Another object of the present invention is to disclose a method for preparing a semiconductor silicon wafer thinning etching solution, comprising the following steps:

[0038] Nitric acid, hydrofluoric acid and a negatively charged complexing agent are sequentially added to ultrapure water, and after the negatively charged complexing agent is completely dissolved, a positively charged organic silicon surfactant is added and stirred evenly to prepare a semiconductor silicon wafer thinning etching solution.

[0039] Another object of the present invention is to disclose an application of a semiconductor silicon wafer thinning etching solution in the field of semiconductor silicon wafer thinning.

[0040] Furthermore, the semiconductor silicon wafer thinning etching solution is particularly suitable for thinning the back side of P-type silicon.

[0041] Furthermore, a method for etching a semiconductor silicon wafer using the semiconductor silicon wafer thinning etching solution comprises the following steps:

[0042] Step 1: Immerse the semiconductor silicon wafer in the semiconductor silicon wafer thinning etching solution at room temperature for 3-10 minutes;

[0043] Step 2: Rinse the soaked semiconductor silicon wafer in ultrapure water, and then blow dry the surface with N2 to complete the etching of the semiconductor silicon wafer.

[0044] Furthermore, the soaking time in step 1 is 5 minutes.

[0045] Furthermore, in step 2, the soaked semiconductor silicon wafer is rinsed in ultrapure water at least twice.

[0046] The principle of etching semiconductor silicon wafers by the semiconductor silicon wafer thinning etching solution of the present invention is as follows:

[0047] Si + 4HNO3 → SiO2 + 4NO2 + 2H2O

[0048] SiO2 + 4HF → SiF4 + 2H2O

[0049] The etching roughening principle of the semiconductor silicon wafer thinning etching solution of the present invention (taking etching of P-type silicon as an example) is as follows Figure 1 As shown. Since a small amount of impurities, such as boron, are doped into P-type silicon, this will cause the number of electrons in silicon to decrease, so that the silicon as a whole presents a positive charge. When etching is performed using the semiconductor silicon wafer thinning etching solution of the present invention, the negatively charged complexing agent will be adsorbed on the surface of the silicon, randomly covering some points, so that the point will not continue to react. Microscopic uneven etching is formed on the entire silicon surface, forming a rough surface; and the positively charged silicone surfactant will stay away from the silicon surface as much as possible due to the principle of charge attraction and mutual repulsion, and attract each other with the negatively charged complexing agent. At the same time, both have Si-O-Si bonds, which provides a greater possibility for the combination of the two, and reduces the situation where the silicone surfactant molecules cover the silicon surface, thereby affecting the etching reaction.

[0050] The semiconductor silicon wafer thinning etching solution of the present invention, its preparation method and application have the following advantages compared with the prior art:

[0051] 1) The negatively charged complexing agent and the positively charged organosilicon surfactant of the present invention can be dynamically and orderly arranged in the etching solution, so that the positively charged organosilicon surfactant will not cover the surface of the P-type silicon, thereby effectively controlling the quality of the etched rough surface.

[0052] 2) The etching rate of the semiconductor silicon wafer thinning etching solution of the present invention is fast. After the P-type silicon surface attracts the negatively charged complexing agent, the positively charged organic silicon surfactant can further reduce the surface tension, better bring the etching solution to the silicon surface, and will not cover the silicon surface and affect the etching of the silicon.

[0053] 3) The surface roughness of the semiconductor silicon wafer etched by the semiconductor silicon wafer thinning etching solution of the present invention is moderate and uniform, and the adhesion of the subsequent process of electroplating copper on the rough surface is relatively large, which can reach 30N / cm 2 , significantly improving the quality of subsequent processes.

[0054] Therefore, the semiconductor silicon wafer thinning silicon etching solution of the present invention has very good application prospects and large-scale industrial promotion potential in the field of semiconductor silicon wafer thinning, especially in the field of P-type silicon back thinning. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Figure 1 The etching roughening principle of the semiconductor silicon wafer thinning etching solution of the present invention;

[0056] Figure 2 This is the infrared spectrum of the pyridine-modified silicone surfactant;

[0057] Figure 3 The SEM images are of the rough morphology of the silicon surface after etching, with a magnification of 10,000 times, wherein a) is the rough morphology of the surface after etching of Comparative Example 1; and b) is the rough morphology of the surface after etching of Example 1. DETAILED DESCRIPTION

[0058] The present invention is further described below in conjunction with embodiments:

[0059] Examples 1-6

[0060] Examples 1-6 disclose a variety of semiconductor silicon wafer thinning etching solutions, the components and weight ratios of which are shown in Table 1. The preparation method is as follows: nitric acid, hydrofluoric acid and a negatively charged complexing agent are sequentially added to ultrapure water, and after the negatively charged complexing agent is completely dissolved, a positively charged organic silicon surfactant is added, and the mixture is stirred evenly to prepare a semiconductor silicon wafer thinning etching solution.

[0061] Table 1 Components and weight ratios of semiconductor silicon wafer thinning etching solutions of Examples 1-6

[0062]

[0063] In the semiconductor silicon wafer thinning etching solution of Example 1-6, the positively charged organic silicon surfactant is a pyridine-modified organic silicon surfactant, and its preparation method is as follows:

[0064] In a three-necked flask equipped with a stirrer and a reflux condenser, nitrogen was filled for 30 minutes, and 0.1 mol of allyl polyether (APEG-1000, CAS No.: 27274-31-3), 0.025 mol of chloroplatinic acid, 0.95 mol of pyridine and 0.1 mol of methyl hydrogen silicone oil (CAS No.: 63148-57-2) were added into the three-necked flask. The reaction was stirred at room temperature for 1 hour, and the temperature was raised to 80°C. The reaction was continued for 5 hours to obtain an organosilicon surfactant containing a pyridine group, i.e., a pyridine-modified organosilicon surfactant.

[0065] Figure 2 This is the infrared spectrum of the pyridine-modified silicone surfactant. It can be seen that at 1080.1cm -1 The absorption peak of Si-OC stretching vibration was detected at 1570.14 cm -1 Nearby is the absorption peak of the stretching vibration of the pyridine aromatic ring, 1600.1cm -1 The main peak is the characteristic peak of aromatic ring C=C, 2974.65 cm -1 The absorption peak at is the stretching vibration of methyl group, which proves that the organosilicon surfactant containing pyridine group is synthesized.

[0066] Comparative Examples 1-5

[0067] Comparative Examples 1-5 disclose a variety of etching solutions, the components and weight ratios of which are shown in Table 2. The preparation methods are the same as those of Example 1, and the positively charged organic silicon surfactant is also the same as that of Example 1.

[0068] Table 2 Components and weight ratios of etching solutions in comparative examples 1-5

[0069]

[0070] The etching solutions of Examples 1-6 and Comparative Examples 1-5 were tested respectively, and the test results are shown in Table 3.

[0071] Table 3 Performance test

[0072]

[0073] As shown in Table 3, in Examples 1-6, the use of a negatively charged complexing agent and a positively charged surfactant enables the etching solution to have a faster silicon etching rate and a higher adhesion of copper on the silicon surface after etching. Compared with Example 1, in Comparative Example 1, due to the lack of a negatively charged complexing agent, the positively charged surfactant and the surface of the P-Si sheet repel each other, making it difficult to have a difference in etching rate, resulting in insufficient surface roughness after etching and decreased adhesion; in Comparative Example 2, due to the lack of a positively charged surfactant, the etching uniformity is reduced, resulting in severe etching and insufficient etching on the P-Si sheet, affecting the adhesion; in Comparative Example 3, since both the complexing agent and the surfactant are positively charged, the two molecules repel each other, and it is difficult to reach a dynamic equilibrium state when etching the P-Si sheet, which can easily cause uneven etching; in Comparative Example 4, since both the complexing agent and the surfactant are negatively charged, both have the ability to adsorb on the surface of the P-Si sheet, affecting the etching rate, and it is difficult to form an etching rate difference; in Comparative Example 5, the surfactant is adsorbed on the P-Si sheet, while the complexing agent is adsorbed on the surfactant. Due to the lack of complexing ability, the adsorption performance of the surfactant molecules is far from sufficient. The final result is that the surfactant spreads the reaction substances all over the surface, the surface roughness is low, and the adhesion is poor.

[0074] like Figure 3 It can be seen that the left figure a is the P-Si surface with poor etching effect in Example 1. It can be observed that its surface is relatively smooth, which is not conducive to the subsequent electroplating metal layer process; the right figure b is the P-Si surface with better etching effect in Example 1. Its surface roughness is relatively large, which can provide good adhesion for the subsequent electroplating metal layer process.

[0075] in:

[0076] Method for etching silicon surface using etching solution:

[0077] Step 1: Soak the silicon wafer in etching solution at room temperature for 5 minutes;

[0078] Step 2: Rinse the soaked silicon wafer in ultrapure water twice, and then blow dry the surface with N2 to complete the etching of the silicon wafer.

[0079] Performance 1 Test method for adhesion of copper to silicon surface after etching:

[0080] Step 1: Electroplating copper on the etched silicon surface, preparing the ingot for the pull-off adhesion test, gluing it to the surface with two-component glue, and waiting for it to dry completely;

[0081] Step 2: Use a rotary cutter to remove the electroplated copper around the ingot to ensure that the adhesion test will not be affected;

[0082] Step 3: Use a pull-off adhesion tester to test the adhesion of the electroplated copper and record the actual value of the instrument.

[0083] Performance 2 Test method for P-type silicon etching rate:

[0084] The depth of the cross section photographed by SEM was measured, and the etching rate was obtained by dividing the depth by the reaction time.

[0085] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A semiconductor silicon wafer thinning etching solution, characterized in that: The composition includes the following components in weight ratio: 10-15 parts of hydrofluoric acid; 5-10 parts of nitric acid; 2-4 parts of a negatively charged complexing agent; 0.1-1 part of positively charged silicone surfactant; 15-30 parts of ultrapure water; The positively charged organosilicon surfactant is a pyridyl-modified organosilicon surfactant; The negatively charged complexing agent is one or more of ammonium thiocyanate, potassium thiocyanate, sodium thiocyanate and potassium bifluoride; The structural formula of the pyridyl-modified organosilicon surfactant is shown in Formula I: ； Formula I; In formula I, n is an integer of 1000-2000, and m is an integer of 10-100.

2. The semiconductor silicon wafer thinning etching solution according to claim 1, characterized in that: The synthesis method of the pyridine-modified organosilicon surfactant is as follows: S1. Add allyl polyether, chloroplatinic acid, pyridine and hydrogenated silicone oil into a container filled with nitrogen, and stir the reaction at room temperature for 1-3 hours; S2. Raise the temperature to 80-100°C and continue the reaction for 5-8 hours to obtain a pyridine-modified silicone surfactant.

3. The semiconductor silicon wafer thinning etching solution according to claim 2, characterized in that: The molar ratio of pyridine, hydrogen-containing silicone oil, allyl polyether and chloroplatinic acid is 6.5-13.5:1:1:0.2-0.

5.

4. A method for preparing a semiconductor silicon wafer thinning etching solution according to any one of claims 1 to 3, characterized in that: The following steps are involved: Nitric acid, hydrofluoric acid and a negatively charged complexing agent are sequentially added to ultrapure water, and after the negatively charged complexing agent is completely dissolved, a positively charged organic silicon surfactant is added and stirred evenly to prepare a semiconductor silicon wafer thinning etching solution.

5. An application of the semiconductor silicon wafer thinning etching solution according to any one of claims 1 to 3 in the field of semiconductor silicon wafer thinning, wherein the semiconductor silicon wafer thinning etching solution is suitable for thinning the back side of P-type silicon.

6. The use according to claim 5, characterized in that: The method for etching a semiconductor silicon wafer using the semiconductor silicon wafer thinning etching solution comprises the following steps: Step 1: Immerse the semiconductor silicon wafer in the semiconductor silicon wafer thinning etching solution at room temperature for 3-10 minutes; Step 2: Rinse the soaked semiconductor silicon wafer in ultrapure water, and then blow dry the surface with N2 to complete the etching of the semiconductor silicon wafer.

7. The use according to claim 6, characterized in that: Step 2: Rinse the soaked semiconductor silicon wafer in ultrapure water at least twice.

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