Wet etching method for semiconductor substrate

Abstract

The present invention discloses a wet etching method for a semiconductor substrate, comprising: measuring the previous thickness value of each point on the nth substrate; measuring the subsequent thickness value of each point on the nth substrate after etching, calculating the etching amount of each point on the nth substrate, establishing an etching amount topography map of the nth substrate according to the etching amount, and the etching amount topography map can reflect the etching amount distribution on the nth substrate; adjusting the moving speed of the liquid spraying swing arm according to the etching amount distribution of the nth substrate to perform etching processing on the (n + 1)th substrate. According to the film thickness difference before and after etching of the nth substrate, the present invention establishes an etching amount topography map and adjusts the moving speed of the liquid spraying swing arm of the (n + 1)th substrate according to the etching amount distribution of the nth substrate, so as to adjust the etching amount of the (n + 1)th substrate, improve the etching uniformity of the substrate, and enhance the yield of the product.

Description

Technical Field

[0001] The present invention relates to the field of integrated circuit manufacturing, and more particularly, to a wet etching technique for semiconductor substrates. Background Art

[0002] As the semiconductor feature size gradually becomes smaller, the wet etching process can precisely control the removal amount of the thin film or metal layer. Due to many advantages of wet etching, such as: low consumption of raw materials, strong adaptability, good surface uniformity, small damage to the silicon wafer, and applicability to most metal materials and substrate materials, wet etching is playing an increasingly important role in semiconductor manufacturing.

[0003] In the wet etching process, due to equipment reasons (precise control of etching time or etching solution temperature) or the lifespan of the etching chemical itself, the etching amount of the etching chemical will change, resulting in excessive undercut of the substrate metal cylinder or metal residue on the substrate surface, seriously affecting the product quality.

[0004] Reliability is one of the important reference indicators for inspecting product yield. Among them, uniformity is a very important parameter, which directly reflects the etching amount difference between each point within the wafer and is a basic parameter for ensuring the consistency of the etched pattern on the silicon wafer. Its calculation formula is:

[0005]

[0006] Among them, Unif refers to uniformity; X1, X2... Xn refer to the etching amounts at different points within a substrate wafer, usually 13 points or 49 points need to be measured; Mean refers to the average value.

[0007] At present, immersion etching machines and single-wafer etching machines are mainly used in the industry. During the processing with an immersion etching machine, the substrate is completely immersed in the chemical solution tank. The amount of chemical solution contacted by each point on the substrate surface is the same, the temperature of the chemical solution contacted by each point on the substrate surface is the same, and the time of contact of each point on the substrate surface with the chemical solution is the same. Therefore, the uniformity of the substrate surface processed by the immersion etching machine process is better. However, during the processing with an immersion etching machine, there are risks of generating micro mechanical scratches and over-etching, which affect the device performance, and the equipment compatibility is not high, which is likely to cause cross-contamination of the equipment and the process, directly affecting the subsequent process processing and product quality. Therefore, in many cases, a single-wafer etching machine is still used to process the substrate. Due to the inherent deficiencies of the single-wafer etching machine process, the etching of the spraying arm at each point on the substrate is not carried out at the same time, and the linear velocity of each point from the center to the edge of the substrate during etching is also different. The residence time of the chemical solution at each point on the substrate may be different, resulting in different etching amounts at each point on the substrate, and the uniformity of the entire substrate wafer does not meet the process requirements, and the yield is poor. Therefore, achieving precise control of the etching amount and improving the yield of the product are major problems faced by the current wet etching process. Summary of the Invention

[0008] The present invention provides a wet etching method for a semiconductor substrate. During the etching process, the moving rate of the spraying arm in different regions of the substrate during the etching of the (n + 1)-th substrate is adjusted according to the etching amount of the n-th substrate, so that the etching amounts within the substrate wafer are the same, thereby improving the uniformity within the wet-etched substrate wafer and increasing the yield.

[0009] According to an embodiment of the present invention, the pre-etching thickness value of each point on the n-th substrate is measured; the post-etching thickness value of each point on the n-th substrate is measured, and the actual etching amount of each point on the n-th substrate is calculated. According to this etching amount, an etching amount topography map of the n-th substrate is established. The etching amount topography map can reflect the distribution of the etching amount on the n-th substrate; the moving rate of the spraying arm is adjusted according to the etching amount distribution of the n-th substrate, and the (n + 1)-th substrate is etched at this moving rate.

[0010] Preferably, the etching amount distribution refers to comparing the actual etching amount of the n-th substrate with the target etching amount, and dividing the etching amount topography map into a low etching amount region and a high etching amount region. The low etching amount region refers to the region where the actual etching amount is lower than the target etching amount, and the high etching amount region refers to the region where the actual etching amount is higher than the target etching amount.

[0011] Preferably, according to the low etching amount region shown in the etching amount topography map of the n-th substrate, the moving rate of the spraying arm is adjusted to be slower in the low etching amount region during the etching of the (n + 1)-th substrate.

[0012] Preferably, according to the areas with higher etching amounts shown in the etching amount topography map of the nth substrate, the moving speed of the liquid spraying swing arm is increased when etching the (n + 1)th substrate in the areas with higher etching amounts.

[0013] The wet etching method of the semiconductor substrate of the present invention uses the film thickness difference before and after etching at each point on the nth substrate to establish an etching topography map, and adjusts the moving speed of the liquid spraying swing arm when etching the (n + 1)th substrate according to the measured etching amount, so as to ensure that the etching amounts in different areas of the (n + 1)th substrate are the same, improve the etching uniformity of the substrate, and increase the yield of the product. Description of the Drawings

[0014] Figure 1 Discloses a flowchart for wet etching a substrate according to the present invention.

[0015] Figure 2 Discloses a measurement trajectory distribution diagram of a substrate thickness measuring instrument.

[0016] Figures 3 to 4 Discloses an etching amount topography map according to an embodiment of the present invention. Detailed Embodiments

[0017] The present invention provides a wet etching method for a semiconductor substrate. During the etching process, the moving speed of the liquid spraying swing arm during the etching process of the (n + 1)th substrate is adjusted according to the etching amount of the nth substrate, so that the etching amounts within the substrate are the same, thereby improving the in-substrate uniformity of the wet etching and increasing the product yield.

[0018] In the wet etching process, as the consumption of the liquid medicine amount and the continuous recycling of the liquid medicine, under normal circumstances, the concentration of the liquid medicine will increase in sequence, resulting in an increase in the etching rate and the etching amount; if the concentration of the liquid medicine decreases in sequence, the etching rate will decrease and the etching amount will decrease. At the same time, it does not exclude the situation where the concentration of other liquid medicines is inversely proportional to the etching rate. To solve the above problems, in the embodiments proposed by the present invention, the etching conditions of the (n + 1)th substrate are determined by the etching amount of the previous substrate of the (n + 1)th substrate, that is, the nth substrate.

[0019] In the first embodiment, a substrate etching device is proposed, including a wet etching chamber, a substrate thickness measuring instrument, a central processing unit, a liquid medicine tank, a liquid spraying swing arm, and a substrate conveying device.

[0020] Reference Figure 1 As shown, discloses a flowchart for wet etching a substrate according to an embodiment of the present invention. A wet etching method for a semiconductor substrate includes the following steps:

[0021] In step 101, first, the thickness before value of each point on the nth substrate is measured by a substrate thickness measuring instrument.

[0022] In step 102, the nth substrate is transferred to the wet etching chamber by the substrate transfer device for the etching process. After the etching process is completed, the nth substrate is returned to the substrate thickness measuring instrument by the substrate transfer device to measure the post-etching thickness value of each point on the nth substrate. The central processing unit calculates the etching amount of each point on the nth substrate, and an etching amount topography map of the nth substrate is established based on this etching amount.

[0023] The etching amount topography map can reflect the distribution of the etching amount on the nth substrate. The etching amount distribution refers to comparing the actual etching amount on the nth substrate with the target etching amount, and dividing the etching amount topography map into a low etching amount region and a high etching amount region. The low etching amount region refers to the region where the actual etching amount is lower than the target etching amount, and the high etching amount region refers to the region where the actual etching amount is higher than the target etching amount.

[0024] To more intuitively display the distribution of the etching amount, colors can be used for distinction. For example, the region where the actual etching amount is higher than the target etching amount is marked as red, and the region where the actual etching amount is lower than the target etching amount is marked as blue. Of course, other colors can also be used for marking. Similarly, the deviation degree between the actual etching amount and the target etching amount in this region can be qualitatively judged according to the depth of the color. Of course, the specific measured value of the etching amount of each point can also be marked on the etching amount topography map to characterize the etching amount distribution on the substrate.

[0025] In step 103, the (n + 1)th substrate is transferred to the wet etching chamber by the substrate transfer device. According to the etching amount topography map of the nth substrate, the moving speed of the liquid spraying swing arm is adjusted to perform the etching process on the (n + 1)th substrate. Specifically, in the low etching amount region, the moving rate of the liquid spraying swing arm when etching the (n + 1)th substrate in this region is reduced to increase the residence time of the liquid medicine in this region, increase the action time of the liquid medicine and the material to be etched, so that the etching amount of the (n + 1)th substrate in this region increases relative to the nth substrate, improving the etching uniformity; in the high etching amount region, the moving rate of the liquid spraying swing arm when etching the (n + 1)th substrate in this region is increased to reduce the residence time of the liquid medicine in this region, reduce the action time of the liquid medicine and the material to be etched, so that the etching amount of the (n + 1)th substrate in this region decreases relative to the nth substrate, improving the etching uniformity.

[0026] Reference Figures 2 to 4 As shown, an etching amount topography map according to an example of the present invention is disclosed. Figure 2Disclosed is a measurement trajectory distribution diagram of a substrate thickness measuring instrument. The substrate is divided into three regions in a concentric circle structure, which are the central measurement area 201, the transition measurement area 202, and the edge measurement area 203 from the inside to the outside. The measurement points within each measurement area have been preset. Generally, 49 points are selected in each measurement area to measure the etching amount. Of course, the measurement trajectory and measurement points can be adjusted accordingly according to specific measurement requirements. This embodiment only illustrates with a measurement trajectory in a concentric circle structure. Figure 3 Disclosed is an etching amount topography map established after etching the nth substrate. According to Figure 3 the specific numerical values of the etching amount at each point marked in the figure, it can be seen that the etching amount of the nth substrate gradually decreases from the center to the edge. In particular, the etching amount at the edge of the substrate is much lower than the target etching amount. This is because compared with the central area of the substrate, the linear velocity at the edge of the substrate is larger, resulting in too little residence time of the chemical solution in the edge area of the substrate and too little accumulation of the chemical solution. Therefore, the reaction time between the chemical solution and the material to be etched is short, causing the etching amount of the substrate to gradually decrease from the center to the edge. Therefore, when etching the (n + 1)th substrate, adjust the moving speed of the liquid spraying swing arm so that the liquid spraying swing arm reduces the moving speed when approaching the edge of the (n + 1)th substrate, in order to extend the residence time of the liquid spraying swing arm at the edge of the substrate and increase the etching amount at the edge of the substrate.

[0027] Figure 4 Disclosed is an etching amount topography map of the (n + 1)th substrate. From Figure 4 it can be seen that the etching amount at the edge of the (n + 1)th substrate has increased relative to the nth substrate, obtaining better etching amount uniformity. Through the above method, the overall etching uniformity of the substrate has been improved. According to the aforementioned uniformity calculation formula, Unif has changed from 2.84% to 0.73%. Similarly, for the area where the substrate has excessive etching, when etching the corresponding area of the (n + 1)th substrate, the moving speed of the liquid spraying swing arm can be increased to reduce the residence time of the liquid spraying swing arm in the over-etched area, so that the etching amount in this area is relatively decreased compared with the nth substrate, in order to obtain better etching uniformity for the whole substrate.

[0028] As can be seen from the above, a wet etching method for a semiconductor substrate proposed by the present invention establishes an etching amount topography map based on the film thickness difference before and after etching the nth substrate, and obtains the etching amount distribution on the nth substrate from the etching amount topography map. Then, according to the etching amount distribution of the nth substrate, adjust the moving speed of the liquid spraying arm of the (n + 1)th substrate, so as to adjust the etching amount of the (n + 1)th substrate, improve the etching uniformity of the substrate, and improve the yield of the product.

[0029] In summary, through the above embodiments and related diagrams, the present invention has specifically and in detail disclosed the related technologies, enabling those skilled in the art to implement accordingly. The above-described embodiments are only used to illustrate the present invention, rather than to limit the present invention. The scope of the rights of the present invention should be defined by the claims of the present invention. As for the change in the number of elements described herein or the substitution of equivalent elements, etc., they should still fall within the scope of the rights of the present invention.

Claims

1. A wet etching method for a semiconductor substrate, characterized in that, Including the following steps: Measure the pre-etching thickness value of each point on the nth substrate; Measure the post-etching thickness value of each point on the nth substrate, calculate the actual etching amount of each point on the nth substrate, and establish an etching amount topography map of the nth substrate according to the etching amount. The etching amount topography map can reflect the distribution of the etching amount on the nth substrate; Adjust the moving speed of the liquid spraying swing arm according to the etching amount distribution of the nth substrate, and perform etching processing on the (n + 1)th substrate at this moving speed; The etching amount distribution of the nth substrate refers to comparing the actual etching amount on the nth substrate with the target etching amount, dividing the etching amount topography map into a low etching amount area and a high etching amount area. The low etching amount area refers to the area where the actual etching amount is lower than the target etching amount, and the high etching amount area refers to the area where the actual etching amount is higher than the target etching amount.

2. The substrate etching method according to claim 1, wherein According to the low etching amount area shown in the etching amount topography map of the nth substrate, adjust the moving speed of the liquid spraying swing arm to slow down when etching the (n + 1)th substrate in the low etching amount area.

3. The substrate etching method according to claim 1, characterized in that, According to the high etching amount area shown in the etching amount topography map of the nth substrate, adjust the moving speed of the liquid spraying swing arm to speed up when etching the (n + 1)th substrate in the high etching amount area.

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