A cleaning method for silicon substrates in the field of semiconductor integrated circuit manufacturing

Abstract

The present invention relates to the field of integrated circuit manufacturing technology, and particularly to a method for cleaning a silicon substrate in the field of semiconductor integrated circuit manufacturing. On the one hand, the present invention uses a mixed solution of ammonium fluoride and ammonium bifluoride with a certain concentration as a cleaning solution to highly chemically selectively remove surface contaminants and silicon oxide on the silicon substrate. On the other hand, a rapid thermal annealing treatment is adopted to more effectively peel the oxide film layer on the silicon substrate surface through the stress difference and crystallization effect between the silicon substrate and the contaminants. The process is simple and suitable for large-scale mass production.

Description

Technical Field

[0001] The present application relates to the field of integrated circuit manufacturing technology, and more specifically, it relates to a method for cleaning a silicon substrate in the field of semiconductor integrated circuit manufacturing. Background Art

[0002] Due to its excellent semiconductor properties, silicon materials have been widely used in the field of semiconductor integrated circuit production for a long time. At present, silicon substrates (components with a certain structure made of silicon materials), such as silicon top ring, showerhead, Si target material, wafer, etc., have always been the core components in the manufacturing of chips and optoelectronic devices in semiconductor integrated circuits because of their high purity and good chemical stability.

[0003] In traditional cleaning processes, a certain proportion of hydrofluoric acid is used for immersion to remove contaminants and oxides on the surface of silicon materials, but it is likely to cause problems such as "spike defects" and difficult-to-control corrosion, affecting the loss of the silicon substrate and the change of the profile size. Especially in the semiconductor integrated circuit manufacturing process below 65nm, the defects of the silicon substrate material caused by hydrofluoric acid immersion will seriously affect the surface structure and electrical properties of the device. Summary of the Invention

[0004] In order to solve the above technical problems of the traditional cleaning process, the purpose of the present invention is to provide a method for cleaning a silicon substrate in the field of semiconductor integrated circuit manufacturing.

[0005] To achieve the above purpose, the present invention adopts the following technical solutions:

[0006] A method for cleaning a silicon substrate in the field of semiconductor integrated circuit manufacturing, comprising the following steps:

[0007] S1: Add ammonium fluoride solution and ammonium bifluoride solution into an immersion tank, control the water bath heating temperature at 25 - 30°C, and then slowly place the silicon substrate into the first immersion tank for immersion;

[0008] S2: Rinse the silicon substrate immersed in step S1 in deionized water for 1 - 2 minutes to dilute and reduce the residual liquid medicine on its surface;

[0009] S3: Place the silicon substrate rinsed in step S2 into a second immersion tank pre-filled with ammonia water solution and hydrogen peroxide solution, and control the water bath heating temperature at 45 - 50°C;

[0010] S4: Repeat step S2 to remove the residual liquid medicine on the surface of the silicon substrate, and then place it into an overflow pure water tank for immersion for 30 - 40 minutes;

[0011] S5: Blow dry the silicon substrate cleaned in step S4;

[0012] S6: Place the silicon substrate dried in step S5 into an annealing furnace to facilitate the removal of surface contaminants on the silicon substrate;

[0013] S7: Repeat steps S1 - S6 until the surface contaminants on the silicon substrate are completely removed.

[0014] Optionally, in step S1, mix a 1 mol / L ammonium fluoride solution and a 1 mol / L ammonium bifluoride solution in a volume ratio of 1:2.

[0015] Optionally, in step S1, control the soaking time of the silicon substrate to be 10 - 15 min.

[0016] Optionally, in step S3, mix a 1 mol / L ammonia water solution and a 3 mol / L hydrogen peroxide solution in a volume ratio of 1:1.

[0017] Optionally, in step S3, control the soaking time of the silicon substrate to be 10 - 15 min.

[0018] Optionally, in step S5, use nitrogen to blow dry the silicon substrate.

[0019] Optionally, in step S6, the temperature in the annealing furnace undergoes high - low temperature alternating cycles within the range of 25 - 250 °C.

[0020] Optionally, in step S6, the heating rate of the annealing furnace is 70 - 80 °C / min.

[0021] Optionally, in step S6, the cooling rate of the annealing furnace is 70 - 80 °C / min.

[0022] The chemical reaction equations involved in the present invention are as follows:

[0023] NH4F or NH4HF2 + H2O + SiO2 → SiF4 + NH3·H2O

[0024] NH4F or NH4HF2 → NH3 + HF, HF + Si → SiF4 + H2

[0025] According to the principle of chemical reaction, ammonium fluoride or ammonium bifluoride can directly react with silicon dioxide to strip the oxide layer on the surface of the silicon substrate. The reaction of silicon with ammonium fluoride or ammonium bifluoride is actually the reaction of silicon with hydrofluoric acid generated after the decomposition of ammonium fluoride or ammonium bifluoride. This reaction process is affected by temperature, concentration, and reversible conditions, and the actual reaction generated is very weak, which can ensure the surface structure and electrical properties of the silicon substrate material to a great extent.

[0026] On the other hand, the acidity of ammonium bifluoride is between that of ammonium fluoride and hydrofluoric acid. It can not only avoid the problem of difficult-to-control corrosiveness caused by the direct addition of hydrofluoric acid solution, but also control the reaction rate under different production conditions by adjusting the ratio between ammonium fluoride and ammonium bifluoride, with stronger production applicability.

[0027] In summary, the present application has the following beneficial effects: on the one hand, a mixed solution of ammonium fluoride and ammonium bifluoride with a certain concentration is used as the cleaning solution to highly chemically selectively remove surface contaminants and silicon oxide on the silicon substrate; on the other hand, by means of rapid thermal annealing treatment, due to the stress difference and crystallization effect between the silicon substrate and the contaminants, a more effective peeling effect on the silicon oxide film layer on the surface of the silicon substrate is achieved. The process is simple and suitable for large-scale production. Description of the Drawings

[0028] Figure 1 It is the temperature curve graph of the annealing furnace in the present invention. Detailed Embodiments

[0029] The following further details the present application in conjunction with the drawings and embodiments.

[0030] Embodiment 1

[0031] A cleaning method for a silicon substrate in the field of semiconductor integrated circuit manufacturing includes the following steps:

[0032] S1: Add a 1 mol / L ammonium fluoride solution and a 1 mol / L ammonium bifluoride solution into the soaking tank at a volume ratio of 1:2, heat the temperature of the tank solution to 25°C by water bath, and then slowly place the silicon substrate into the soaking tank and soak for 15 min;

[0033] S2: Rinse the silicon substrate soaked above in deionized water for 2 min to dilute and reduce the residual liquid medicine on the surface of the silicon substrate;

[0034] S3: Add a 1 mol / L ammonia water solution and a 3 mol / L hydrogen peroxide solution into another soaking tank at a volume ratio of 1:1, heat the temperature of the tank solution to 45°C by water bath, and place the silicon substrate rinsed above into the soaking tank and soak for 15 min;

[0035] S4: Repeat step S2 to remove the residual liquid medicine on the surface of the silicon substrate, and then place it into the overflow pure water tank and soak for 40 min;

[0036] S5: Blow dry the silicon substrate cleaned above with nitrogen;

[0037] S6: Place the silicon substrate dried above into the annealing furnace at Figure 1Perform rapid thermal annealing on the temperature curve therein. The purpose is to stimulate the interfacial effect between the silicon substrate and the stubborn surface contaminants without affecting the crystallization effect of the silicon substrate, causing the interfacial structure between the silicon substrate (component) and the contaminants to change, and promoting the cleaning and removal effect of the contaminants;

[0038] S7: Repeat steps S1 - S6 until the surface contaminants of the silicon substrate are completely removed.

[0039] Example 2

[0040] A cleaning method for a silicon substrate in the field of semiconductor integrated circuit manufacturing, comprising the following steps:

[0041] S1: Add a 1 mol / L ammonium fluoride solution and a 1 mol / L ammonium bifluoride solution to the soaking tank in a volume ratio of 1:2, heat the bath liquid temperature to 30 °C by water bath, and then slowly place the silicon substrate into the soaking tank and soak for 10 min;

[0042] S2: Rinse the above - soaked silicon substrate in deionized water for 1 min to dilute and reduce the residual liquid medicine on the silicon substrate surface;

[0043] S3: Add a 1 mol / L ammonia water solution and a 3 mol / L hydrogen peroxide solution to another soaking tank in a volume ratio of 1:1, heat the bath liquid temperature to 50 °C by water bath, and place the above - rinsed silicon substrate into the soaking tank and soak for 10 min;

[0044] S4: Repeat step S2 to remove the residual liquid medicine on the silicon substrate surface, and then place it in an overflow pure water tank and soak for 30 min;

[0045] S5: Dry the above - cleaned silicon substrate with nitrogen;

[0046] S6: Place the above - dried silicon substrate into an annealing furnace and perform rapid thermal annealing according to the Figure 1 temperature curve therein. The purpose is to stimulate the interfacial effect between the silicon substrate and the stubborn surface contaminants without affecting the crystallization effect of the silicon substrate, causing the interfacial structure between the silicon substrate (component) and the contaminants to change, and promoting the cleaning and removal effect of the contaminants;

[0047] S7: Repeat steps S1 - S6 until the surface contaminants of the silicon substrate are completely removed.

[0048] Example 3

[0049] A cleaning method for a silicon substrate in the field of semiconductor integrated circuit manufacturing, comprising the following steps:

[0050] S1: Add ammonium fluoride solution at 1 mol / L and ammonium bifluoride solution at 1 mol / L into the soaking tank in a volume ratio of 1:2. Heat the solution in the tank to 25°C by water bath, and then slowly put the silicon substrate into the soaking tank and soak for 12 minutes.

[0051] S2: Rinse the silicon substrate soaked above in deionized water for 2 minutes to dilute and reduce the residual liquid medicine on the surface of the silicon substrate.

[0052] S3: Add ammonium hydroxide solution at 1 mol / L and hydrogen peroxide solution at 3 mol / L into another soaking tank in a volume ratio of 1:1. Heat the solution in the tank to 45°C by water bath, and put the silicon substrate rinsed above into the soaking tank and soak for 12 minutes.

[0053] S4: Repeat step S2 to remove the residual liquid medicine on the surface of the silicon substrate, and then put it into the overflow pure water tank and soak for 30 minutes.

[0054] S5: Dry the silicon substrate cleaned above with nitrogen.

[0055] S6: Put the silicon substrate dried above into the annealing furnace and perform rapid thermal annealing treatment according to the temperature curve in Figure 1 . The purpose is to stimulate the interfacial effect between the silicon substrate and the stubborn surface contaminants without affecting the crystallization effect of the silicon substrate, so that the interfacial structure between the silicon substrate (component) and the contaminants changes, and promote the cleaning and removal effect of the contaminants.

[0056] S7: Repeat steps S1 - S6 until the surface contaminants of the silicon substrate are completely removed.

[0057] Example 4

[0058] A cleaning method for a silicon substrate in the field of semiconductor integrated circuit manufacturing, comprising the following steps:

[0059] S1: Add ammonium fluoride solution at 1 mol / L and ammonium bifluoride solution at 2 mol / L into the soaking tank in a volume ratio of 1:1. Heat the solution in the tank to 25°C by water bath, and then slowly put the silicon substrate into the soaking tank and soak for 15 minutes.

[0060] S2: Rinse the silicon substrate soaked above in deionized water for 2 minutes to dilute and reduce the residual liquid medicine on the surface of the silicon substrate.

[0061] S3: Add ammonium hydroxide solution at 1 mol / L and hydrogen peroxide solution at 2 mol / L into another soaking tank in a volume ratio of 1:1.5. Heat the solution in the tank to 45°C by water bath, and put the silicon substrate rinsed above into the soaking tank and soak for 15 minutes.

[0062] S4: Repeat step S2 to remove the residual liquid medicine on the surface of the silicon substrate, and then immerse it in an overflow pure water tank for 40 min;

[0063] S5: Use nitrogen to blow dry the silicon substrate after the above cleaning;

[0064] S6: Put the above blow-dried silicon substrate into an annealing furnace. First, increase the temperature in the annealing furnace from 25 °C to 250 °C at a rate of 80 °C / min, and then decrease the temperature in the annealing furnace from 250 °C to 25 °C at a rate of 70 °C / min. Take this as one cycle and repeat 5 cycles;

[0065] S7: Repeat steps S1 - S6 until the surface contaminants of the silicon substrate are completely removed.

[0066] In Examples 1 - 4, the bath liquid in step S1 and the bath liquid in step S3 can also be heated to the required temperature by other heating methods such as electric heating rods; in step S6, the temperature in the annealing furnace undergoes high and low temperature alternating cycles within the range of 25 - 250 °C. Among them, the heating rate in the heating stage is 70 - 80 °C / min, preferably 75 °C / min; the cooling rate in the cooling stage is 70 - 80 °C / min, preferably 75 °C / min.

[0067] The technical features of the above embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered to be within the scope described in this specification.

[0068] The above specific embodiments are only explanations of the present application, and they are not limitations of the present application. Those skilled in the art can make modifications without creative contributions to this embodiment after reading this specification, but as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A cleaning method for a silicon substrate in the field of semiconductor integrated circuit manufacturing, characterized in that, It includes the following steps: S1: Add ammonium fluoride solution and ammonium bifluoride solution into the first soaking tank, control the water bath heating temperature at 25 - 30 °C, and then slowly put the silicon substrate into the soaking tank for soaking; S2: Rinse the silicon substrate soaked in step S1 in deionized water for 1 - 2 min to dilute and reduce the residual liquid medicine on its surface; S3: Put the silicon substrate rinsed in step S2 into the second soaking tank pre-filled with ammonia water solution and hydrogen peroxide solution for soaking, and control the water bath heating temperature at 45 - 50 °C; S4: Repeat step S2 to remove the residual liquid medicine on the surface of the silicon substrate, and then put it into an overflow pure water tank for soaking for 30 - 40 min; S5: Dry the silicon substrate cleaned in step S4; S6: Put the silicon substrate dried in step S5 into an annealing furnace to promote the removal of surface contaminants of the silicon substrate; S7: Repeat steps S1 - S6 until the surface contaminants of the silicon substrate are completely removed; In step S6, the temperature in the annealing furnace undergoes high and low temperature alternating cycles within the range of 25 - 250 °C. Specifically, the heating rate of the annealing furnace is 70 - 80 °C / min, and the cooling rate of the annealing furnace is 70 - 80 °C / min.

2. The cleaning method according to claim 1, wherein, In step S1, mix 1 mol / L ammonium fluoride solution and 1 mol / L ammonium bifluoride solution in a volume ratio of 1:

2.

3. The cleaning method according to claim 1, characterized in that In step S1, control the soaking time of the silicon substrate at 10 - 15 min.

4. The cleaning method according to claim 1, characterized in that In step S3, mix 1 mol / L ammonia water solution and 3 mol / L hydrogen peroxide solution in a volume ratio of 1:

1.

5. The cleaning method according to claim 1, wherein In step S3, control the soaking time of the silicon substrate at 10 - 15 min.

6. The cleaning method according to claim 1, characterized in that, In step S5, use nitrogen to dry the silicon substrate.

Images