A cleaning method for improving the quality of epitaxial layers

Abstract

The application relates to the field of semiconductor technology, and relates to a cleaning method for improving epitaxial layer defects.The cleaning machine is cleaned, and the cleaning machine is arranged with a first deionized water tank, a first reagent tank, a second reagent tank, a second deionized water tank, a third deionized water tank, a fourth deionized water tank and a fifth deionized water tank which are sequentially connected from left to right; the first reagent tank and the second reagent tank are provided with heating mechanisms; the cleaning steps of the cleaning machine include the following steps: after deionized water is injected into the first reagent tank and the second reagent tank, the deionized water is heated; when the deionized water is heated to 60-90 DEG C, the deionized water in the first reagent tank and the second reagent tank is injected into the second deionized water tank, the third deionized water tank, the fourth deionized water tank and the fifth deionized water tank; and the cleaning time is 0.5-2 h.The cleaning process of the cleaning machine is optimized, the cleaning machine is cleaned after being heated, and the problem of silicon wafer epitaxial layer defects is solved.

Description

Technical Field

[0001] This invention relates to the field of semiconductor technology, specifically a cleaning method. Background Technology

[0002] Currently, the standard semiconductor silicon wafer cleaning process used in the market is the RCA standard cleaning method invented by Kern in 1970. This method uses SC1 cleaning solution in combination with SC2 cleaning solution or DHF (diluted hydrogen fluoride) in a cleaning process, and has been in use ever since. However, with the continuous development of the semiconductor industry and the development of chips with smaller linewidths, higher requirements have been placed on the surface cleanliness of the substrates used in chip processing, especially for 6-inch wafers. <111> Crystalline products, due to their atomic structure, <111> Crystalline surface micro-roughness compared to <100> Larger crystal orientations make it easier for tiny particles to be adsorbed and retained on the surface. Given the current technological limitations, it is difficult to completely remove these tiny particles adsorbed on the silicon wafer surface. Furthermore, conventional particle detection equipment like the SP1 can only detect particles larger than 0.12µm. These particles, exceeding the SP1 detection limit, remain attached to the silicon wafer surface. <111> Large particle anomalies often appear on the substrate surface after epitaxy of crystal-oriented products, and stacking faults occur during etching, resulting in a high epitaxial stacking fault rate.

[0003] The surface condition of the silicon wafer after epitaxy is an important indicator in the production and processing of semiconductor silicon wafers, and it often directly affects the performance of downstream chip and device production.

[0004] Currently, there is a lack of methods to improve epitaxial stacking faults. Summary of the Invention

[0005] In view of the problems existing in the prior art, the present invention provides an improved cleaning method for epitaxial stacking faults to solve at least one of the above-mentioned technical problems.

[0006] To achieve the above objectives, the present invention provides a cleaning method for improving epitaxial stacking faults, characterized in that a cleaning machine is cleaned; the cleaning machine has a primary deionized water tank, a primary reagent tank, a secondary reagent tank, a secondary deionized water tank, a tertiary deionized water tank, a quaternary deionized water tank, and a quinary deionized water tank arranged sequentially from left to right.

[0007] Both the primary and secondary reagent tanks are equipped with heating mechanisms;

[0008] The cleaning steps of the washing machine include injecting deionized water into the primary reagent tank and the secondary reagent tank, heating the deionized water, and when the deionized water temperature rises to 60-90℃, injecting the deionized water from the primary and secondary reagent tanks into the secondary, tertiary, quaternary, and quinary deionized water tanks. The cleaning time for the secondary, tertiary, quaternary, and quinary deionized water tanks is 0.5-2 hours.

[0009] Traditionally, after silicon wafers are placed into the final cleaning machine, they pass through different tanks in sequence for cleaning. After one cycle, the cleaning machine tanks themselves need to be cleaned. Currently, the industry standard is to use room temperature DIW to rinse each tank and pipe.

[0010] This invention optimizes the cleaning process of the washing machine, and the washing machine that cleans after heating solves the problem of epitaxial layer faults on silicon wafers.

[0011] Further preferably, the cleaning time for the secondary deionization tank, tertiary deionization tank, quaternary deionization tank, and quinary deionization tank is 1 hour.

[0012] More preferably, the washing machine is used for 6-inch... <111> Cleaning after polishing of crystal-oriented products and before epitaxy.

[0013] More preferably, the time for deionized water in the primary and secondary reagent tanks is 0.5-2 hours.

[0014] Further preferred, the secondary deionization water tank, tertiary deionization water tank, quaternary deionization water tank, and quinary deionization water tank use soaking overflow circulation for cleaning.

[0015] Soaking overflow circulation refers to a water tank consisting of an inner tank and an outer tank. Deionized water in the outer tank is continuously pumped into the inner tank from the bottom of the outer tank by a diaphragm pump. When the inner tank is full of deionized water, the deionized water overflows from the top of the inner tank and returns to the outer tank. Then, it continues to be pumped into the inner tank from the outer tank, continuously circulating and overflowing for cleaning.

[0016] More preferably, when cleaning the epitaxial silicon wafer in the primary and secondary reagent baths, the reagent is SC1.

[0017] A further preferred formulation of SC1 is: NH4OH:H2O2:H2O=1:2:(5-20).

[0018] More preferably, after the deionized water in the primary reagent tank and the secondary reagent tank is heated to 60-90°C, the deionized water is transported to the secondary deionized water tank and the tertiary deionized water tank for cleaning for 1 hour.

[0019] Deionized water is injected into the primary and secondary reagent tanks and heated to 60-90℃. The deionized water is then transferred to the fourth and fifth deionized water tanks for 1 hour of cleaning.

[0020] Beneficial effects:

[0021] The washing process, employing 60-90℃ hot water combined with 0.5-2 hours of circulating overflow, more effectively removes minute organic matter adhering to the inner wall of the washing tank, improving the cleanliness of the silicon wafer surface being cleaned, especially for 6-inch wafers. <111> The improved surface cleanliness of the silicon wafer with crystal orientation solves the problem of stacking faults in epitaxy caused by the presence of tiny particles on the substrate surface that have not been cleaned properly, reducing the stacking fault rate to ≤0.5%. Attached Figure Description

[0022] Figure 1 This is a comparison chart of particle test results after four embodiments of the present invention;

[0023] Figure 2 This is a comparison chart of the preferred corrosion results after four embodiments of the present invention. Detailed Implementation

[0024] The present invention will now be further described with reference to the accompanying drawings.

[0025] With 6 inches <111> Taking crystal-oriented products as an example, the washing machine tank is cleaned with hot water. The condition of small particles on the silicon wafer surface and the incidence of stacking faults at the epitaxial ends are observed to see if there is any improvement after cleaning. The washing machine consists of a primary deionized water tank, a primary reagent tank, a secondary reagent tank, a secondary deionized water tank, a tertiary deionized water tank, a quaternary deionized water tank, and a quinary deionized water tank, arranged sequentially from left to right. The primary and secondary reagent tanks are equipped with heating mechanisms. The washing machine is used for 6-inch wafers. <111> Cleaning after polishing of crystal-oriented products and before epitaxy.

[0026] Example 1: Use room temperature deionized water to rinse each tank and pipe, without circulating the deionized water.

[0027] Example 2: The cleaning steps of the washing machine include injecting deionized water into the primary reagent tank and the secondary reagent tank. The deionized water is at room temperature. The deionized water in the primary reagent tank and the secondary reagent tank is injected into the secondary deionized water tank, the tertiary deionized water tank, the quaternary deionized water tank and the quinary deionized water tank. The cleaning time is 0.5-2 hours.

[0028] Example 3: The cleaning steps of the washing machine include injecting deionized water into the primary reagent tank and the secondary reagent tank, heating the deionized water, and when the deionized water temperature rises to 60-90℃, injecting the deionized water in the primary reagent tank and the secondary reagent tank into the secondary deionized water tank, the tertiary deionized water tank, the quaternary deionized water tank and the quinary deionized water tank, without circulation, and the cleaning time is 0.5-2 hours.

[0029] Example 4: The cleaning steps of the washing machine include injecting deionized water into the primary reagent tank and the secondary reagent tank, heating the deionized water, and when the deionized water temperature rises to 60-90℃, injecting the deionized water in the primary reagent tank and the secondary reagent tank into the secondary deionized water tank, the tertiary deionized water tank, the quaternary deionized water tank and the quinary deionized water tank for circulation cleaning, and the cleaning time is 0.5-2 hours.

[0030] "Circulation" refers to the overflow of deionized water, while "non-circulation" refers to the static soaking of deionized water.

[0031] After implementing the above four examples, the results are as follows:

[0032]

[0033] Specifically, that is to say:

[0034] 1. After four examples, the polished disc was cleaned, and the particle size distribution results measured by SP1 are as follows:

[0035] 1) For the number of particles of 0.16um, 0.2um, and 0.3um, the four sets of examples were at a similar level with no significant difference.

[0036] 2) For the number of small particles of 0.065um and 0.12um, Example 4 < Example 3 < Example 2 < Example 1, the data shows that the polished sheet processed by the washing process of 60-90℃ hot water circulation for 0.5-2h has a significantly reduced number of small particles on its surface compared with the product of conventional washing process, especially the number of small particles of 0.12um and 0.065um, which is almost reduced by half.

[0037] II. After four examples, the epitaxial wafers were cleaned, and the particle test results are as follows:

[0038] Example 1: The particle test image after epitaxy confirmed that the abnormal area of ​​large particles on the silicon wafer after epitaxy was 2-3%. (See...) Figure 1 (a) in the middle.

[0039] In Example 2, the range of large particle abnormality areas on the epitaxial silicon wafer was 1-2%, see [example missing]. Figure 1 (b) in the middle.

[0040] In Example 3, the range of large particle abnormality area on the silicon wafer after epitaxy was 0.5-1%, see [reference needed]. Figure 1 (c) in the middle.

[0041] In Example 4, the range of large particle abnormalities on the epitaxial silicon wafer was 0-0.5%. (See...) Figure 1 (d) in the middle.

[0042] III. After four examples, the epitaxial wafer was cleaned, and the preferred etching results are as follows:

[0043] Example 1 shows that preferential corrosion results indicate the presence of stacking faults at abnormal particle locations, with a stacking fault incidence rate of 2-3%. Figure 2 (a) in the middle.

[0044] Example 2 shows that preferential corrosion results indicate the presence of stacking faults at abnormal particle locations, with a stacking fault incidence rate of 1-2%. Figure 2 (b) in the middle.

[0045] Example 3 shows that preferential corrosion results indicate the presence of stacking faults at abnormal particle locations, with a stacking fault incidence rate of 0.5-1%. Figure 2 (c) in the middle.

[0046] Example 4, the preferential corrosion results, showed stacking faults at the abnormal particle locations, with a stacking fault incidence rate of 0-0.5%. (See...) Figure 2 (d) in the middle.

[0047] The steps of selective corrosion:

[0048] Basic principle of preferential corrosion:

[0049] 1) Defect areas are prone to crystal deformation, stress concentration, and the accumulation of impurities such as dopants, metals, oxygen, and carbon. They are more chemically reactive than non-defect areas, and after corrosion, corrosion pits will form in the defect areas.

[0050] 2) The morphology of corrosion pits generally corresponds to specific defects. By observing the morphology and distribution of corrosion pits, we can determine the type and cause of the defects.

[0051] Preferred corrosion method steps:

[0052] according to <111> Prepare the appropriate Sirtl etching solution according to the crystal orientation, etch for 2 minutes, and observe the surface morphology of the sample under a microscope.

[0053] Wright's fluid 100 Heavy doping Secco liquid 100 Lightly mixed Sirtl liquid 111 Light and heavy mixing

[0054] Beneficial effects: The conventional cleaning process for the washing machine tank is a room temperature DIW rinsing process. This method cannot completely remove the organic residues attached to the inside of the washing machine tank, mainly polishing wax residues. Polishing wax is mainly composed of a natural resin mixture of rosin and fatty acid glycerides. It does not have a fixed melting point and boiling point and easily melts into a liquid state in hot water. Using hot water to clean the tank can more effectively remove the tiny organic substances attached to the inner wall of the washing machine tank.

[0055] The above are merely preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A cleaning method for improving epitaxial stacking faults, characterized in that, Clean the washing machine; the washing machine has a series of sequentially connected deionized water tanks, reagent tanks, reagent tanks, deionized water ... Both the primary and secondary reagent tanks are equipped with heating mechanisms; The cleaning steps of the cleaning machine include injecting deionized water into the primary reagent tank and the secondary reagent tank, heating the deionized water, and when the deionized water temperature rises to 60-90℃, injecting the deionized water in the primary reagent tank and the secondary reagent tank into the secondary deionized water tank, the tertiary deionized water tank, the quaternary deionized water tank and the quinary deionized water tank. The washing machine is used for 6-inch <111> Cleaning after polishing and before epitaxy of crystal-oriented products; The time for deionized water in the primary and secondary reagent tanks is 0.5-2 hours; The secondary deionization water tank, the tertiary deionization water tank, the quaternary deionization water tank and the quinary deionization water tank are cleaned by soaking overflow circulation. Deionized water is used for rinsing in the primary reagent tank and the secondary reagent tank by immersion overflow circulation. Soaking overflow circulation refers to a water tank consisting of an inner tank and an outer tank. Deionized water in the outer tank is continuously pumped into the inner tank from the bottom of the outer tank by a diaphragm pump. When the inner tank is full of deionized water, the deionized water overflows from the top of the inner tank and returns to the outer tank. Then it continues to be pumped into the inner tank from the outer tank, continuously circulating and overflowing for cleaning. When cleaning the epitaxial silicon wafers in the primary and secondary reagent baths, the reagent used is SC1. The SC1 ratio is: NH4OH:H2O2:H2O = 1:2:(5-20); After the deionized water in the primary and secondary reagent tanks is heated to 60-90℃, the deionized water is transferred to the secondary and tertiary deionized water tanks for 1 hour of cleaning. Deionized water is injected into the primary and secondary reagent tanks and heated to 60-90℃. The deionized water is then transferred to the fourth and fifth deionized water tanks for 1 hour of cleaning.

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