Wafer grinding method

Abstract

The invention discloses a wafer grinding method which adopts thinning equipment to grind a wafer, a soft grinding wheel is adopted as a grinding wheel of the thinning equipment, and the method comprises the following steps: S1, fixing the wafer to be ground on a wafer bearing table of the thinning equipment; s2, the position of a grinding wheel of the thinning equipment is adjusted in place; s3, the rotating speed of the grinding wheel and the rotating speed of the wafer bearing table are adjusted, so that the grinding wheel and the wafer bearing table rotate at the low rotating speed; and S4, a grinding wheel is adopted to feed and grind the to-be-ground wafer in multiple stages until the to-be-ground wafer completes the corresponding removal amount. According to the scheme, on one hand, the soft grinding wheel is used, so that energy brought by end jump of the grinding wheel is adsorbed, and vibration transmitted to the surface of a wafer due to end jump is reduced; on the other hand, by adjusting the rotating speed of the grinding wheel and the rotating speed of the wafer bearing table, the grinding wheel and the wafer bearing table both rotate at a low rotating speed, so that the end jumping frequency of the grinding wheel and the wafer bearing table is reduced, the probability that grains are generated on the surface of the wafer is reduced, thinning and grinding grains on the surface of the wafer can be reduced, and the yield of the wafer can be improved.

Description

Technical Field

[0001] The invention relates to the technical field of semiconductor substrate processing, and in particular to a wafer grinding method. Background Art

[0002] Silicon carbide wafers (SiC wafers) have attracted much attention as power device substrates because of their superior properties to silicon. However, SiC wafers have a hardness second only to diamond and excellent chemical resistance, making them difficult to process.

[0003] The steps of thinning silicon carbide wafers (SiC wafers) are to adsorb the wafer to be processed on the thinning equipment (such as Figure 1 The wafer stage is placed on the wafer carrier (as shown in the figure), and then the inner and outer circular axis center lines of the working surface of the diamond grinding wheel (grinding wheel) of the thinning equipment are adjusted to the center position of the silicon carbide wafer. Then the wafer carrier and the grinding wheel rotate around their respective axes, and the cutting grinding is achieved by feeding the grinding wheel. Among them, the grinding includes two stages: rough grinding and fine grinding.

[0004] However, due to the problem of end face runout of the grinding wheel spindle of the thinning equipment, thinning lines (grinding lines) will remain on the wafer after the grinding process is completed, such as Figure 2 As shown, even if polishing or chemical mechanical polishing is performed after grinding, the texture cannot be effectively removed. Summary of the invention

[0005] In view of this, the present invention provides a chip grinding method, which can reduce the generation of thinning grinding lines on the chip surface, and can effectively alleviate the problem of end jump of thinning equipment causing lines on the chip surface, thereby helping to improve the yield of the chip.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] A wafer grinding method, wherein a wafer is ground using a thinning device, the grinding wheel of the thinning device is a soft grinding wheel, and the method comprises the following steps:

[0008] S1, fix the wafer to be ground on the wafer holding table of the thinning equipment;

[0009] S2. Adjust the position of the grinding wheel of the thinning equipment into place;

[0010] S3, adjusting the rotation speed of the grinding wheel and the wafer table so that both the grinding wheel and the wafer table rotate at a low speed;

[0011] S4, using a grinding wheel to feed and grind the wafer to be ground in multiple stages until the wafer to be ground has completed a corresponding amount of removal.

[0012] Preferably, the grinding wheel is a ceramic grinding wheel or a resin grinding wheel.

[0013] Preferably, in step S3, the rotation speed of the grinding wheel is 1203-1216 rpm, and the rotation speed of the wafer table is 61-79 rpm;

[0014] In the step S4, the grinding wheel is used to feed and grind the wafer to be ground in multiple stages, including:

[0015] The grinding wheel is used to feed and grind the wafer to be ground in three stages; wherein the feeding speed of the grinding wheel in the first stage is 0.2-0.3 μm / min, the feeding speed in the second stage is 0.2-0.1 μm / min, and the feeding speed in the third stage is 0.1 μm / min.

[0016] Preferably, in step S3, the rotation speed of the grinding wheel is 1217-1296 rpm, and the rotation speed of the wafer table is 53-83 rpm;

[0017] In the step S4, the grinding wheel is used to feed and grind the wafer to be ground in multiple stages, including:

[0018] The grinding wheel is used to feed and grind the wafer to be ground in three stages; wherein the feeding speed of the grinding wheel in the first stage is 0.2-0.3 μm / min, the feeding speed in the second stage is 0.2-0.1 μm / min, and the feeding speed in the third stage is 0.1 μm / min.

[0019] Preferably, in step S3, the rotation speed of the grinding wheel is 1297-1314 rpm, and the rotation speed of the wafer table is 67-103 rpm;

[0020] In the step S4, the grinding wheel is used to feed and grind the wafer to be ground in multiple stages, including:

[0021] The grinding wheel is used to feed and grind the wafer to be ground in three stages; wherein the feeding speed of the grinding wheel in the first stage is 0.2-0.3 μm / min, the feeding speed in the second stage is 0.2-0.1 μm / min, and the feeding speed in the third stage is 0.1 μm / min.

[0022] Preferably, in step S4, the amount of material removed from the wafer to be ground in the first stage is greater than the amount removed in the second stage, the amount of material removed from the wafer to be ground in the second stage is greater than or equal to the amount removed in the third stage, and the sum of the amount of material removed from the wafer to be ground in the second stage and the amount of material removed in the third stage is greater than or equal to 5 μm.

[0023] Preferably, the grinding wheel of the thinning device is arranged obliquely relative to the wafer stage; wherein the edge of the grinding wheel close to the center of the wafer stage is at a large distance from the wafer stage, and the middle part is at a small distance from the wafer stage.

[0024] Preferably, the fixed value of the inclination angle of the center point of the grinding wheel relative to the wafer stage is 0, the calculated inclination angle threshold of the middle point relative to the wafer stage is -4 to -6 μm, and the calculated inclination angle threshold of the edge point relative to the wafer stage is -35 to -40 μm.

[0025] Preferably, before step S1, the method further includes:

[0026] The grinding wheel is trimmed so that the height of each tooth of the grinding wheel is the same.

[0027] Preferably, before step S1, the method further includes:

[0028] Place the wafer to be polished in an ethanol solution and ultrasonically clean it for 5 minutes;

[0029] After step S4, the method further includes:

[0030] The ground wafer was placed in an ethanol solution and ultrasonically cleaned for 5 minutes.

[0031] It can be seen from the above technical scheme that the chip grinding method provided by the present invention, on the one hand, uses a soft grinding wheel to absorb the energy brought by the end jump of the grinding wheel, so that the vibration caused by the end jump is transmitted to the chip surface less; on the other hand, by adjusting the rotation speed of the grinding wheel and the wafer stage, the grinding wheel and the wafer stage are rotated at a low speed to reduce the frequency of the end jump of the grinding wheel and the wafer stage, thereby reducing the probability of the generation of surface lines on the chip, and further reducing the generation of thinning grinding lines on the chip surface, which can effectively alleviate the problem of end jump of the thinning equipment causing the generation of lines on the chip surface, thereby helping to improve the yield of the chip. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0033] Figure 1 Schematic diagram of grinding silicon carbide wafers for existing thinning equipment;

[0034] Figure 2 This is a channel diagram for detecting defects on the surface of silicon carbide wafers after processing using existing technology;

[0035] Figure 3 A flow chart of a wafer grinding method provided by an embodiment of the present invention;

[0036] Figure 4 A schematic diagram of the rotation of the grinding wheel and the wafer stage of the thinning device provided in an embodiment of the present invention;

[0037] Figure 5 A schematic diagram of the distribution of the inclination angles of the wafer carrier and the grinding wheel provided in an embodiment of the present invention;

[0038] Figure 6 The surface shape of the silicon carbide wafer after processing using the parameters in Table 1 provided in the embodiment of the present invention;

[0039] Figure 7 Another side profile of a silicon carbide wafer processed using the parameters in Table 1 provided in an embodiment of the present invention;

[0040] Figure 8 The surface shape of the silicon carbide wafer after processing using the parameters in Table 2 provided in the embodiment of the present invention;

[0041] Fig. 9 Another side profile of a silicon carbide wafer processed using the parameters in Table 2 provided in an embodiment of the present invention;

[0042] Fig.10 The surface shape of the silicon carbide wafer after processing using the parameters in Table 3 provided in the embodiment of the present invention;

[0043] Fig.11 Another side profile of a silicon carbide wafer processed using the parameters in Table 3 provided in an embodiment of the present invention;

[0044] Fig.12 A channel diagram of surface defect detection of a silicon carbide wafer after processing using the parameters in Table 1 provided in an embodiment of the present invention;

[0045] Fig.13 Another detection channel diagram of surface defects of a silicon carbide wafer after processing using the parameters in Table 1 provided in an embodiment of the present invention;

[0046] Fig.14 A channel diagram of surface defect detection of a silicon carbide wafer after processing using the parameters in Table 2 provided in an embodiment of the present invention;

[0047] Fig.15 Another detection channel diagram of surface defects of a silicon carbide wafer after processing using the parameters in Table 2 provided in an embodiment of the present invention;

[0048] Fig.16 A channel diagram of surface defect detection of a silicon carbide wafer after processing using the parameters in Table 3 provided in an embodiment of the present invention;

[0049] Fig.17 Another detection channel diagram of surface defects of a silicon carbide wafer after processing using the parameters in Table 3 provided in an embodiment of the present invention;

[0050] Fig.18 A surface diagram of a silicon carbide wafer after being processed using an unimproved process provided by an embodiment of the present invention;

[0051] Fig.19 Another side profile of a silicon carbide wafer after being processed by an unimproved process provided by an embodiment of the present invention;

[0052] Fig. 20 A channel diagram for detecting surface defects of a silicon carbide wafer after processing using an unimproved process provided by an embodiment of the present invention;

[0053] Fig.21 Another detection channel diagram of surface defects of a silicon carbide wafer after processing using an unimproved process provided by an embodiment of the present invention;

[0054] Fig. 22 A surface diagram of a silicon carbide wafer after being processed using the unimproved process provided by an embodiment of the present invention;

[0055] Fig.23 Another side profile of a silicon carbide wafer after being processed by the unimproved process provided by an embodiment of the present invention;

[0056] Fig.24 A channel diagram for detecting surface defects of a silicon carbide wafer after processing using the unimproved process provided by an embodiment of the present invention;

[0057] Fig.25 Another detection channel diagram of surface defects of a silicon carbide wafer after being processed using an unimproved process provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0058] In the above background technology, the end face runout of the grinding wheel spindle refers to the stability of the grinding wheel spindle during rotation, which is generally expressed by the up and down vibration amplitude of the outermost edge; the end face runout of the wafer stage is the same; among them, the grinding wheel spindle and the wafer stage of the thinning equipment will produce a certain degree of tiny end face runout due to the precision relationship, so a certain windmill-shaped pattern will be produced on the outermost side of the wafer (i.e. the thinning pattern mentioned above). The main reason is the precision problem of the thinning equipment, that is, the dynamic balance of the grinding wheel spindle is poor, the grinding wheel will jump up and down during the process of grinding the wafer, and the influencing conditions of the pattern are rotation. speed and grinding wheel (grinding wheel) hardness; among them, high speed will lead to an increase in the frequency of end jump, greatly increasing the probability of windmill texture; low-wear grinding wheels have strong rigidity, and the end jump during the grinding process will not be easily absorbed by the grinding wheel teeth, and the vibration caused by the end jump will be directly transmitted to the wafer surface, thereby causing windmill-shaped texture; in this regard, the generation of wafer surface texture can be alleviated by reducing the speed of the grinding wheel spindle and the wafer table, and using a grinding wheel with a softer bond. For this reason, the wafer grinding method provided in this scheme can improve the problem of wafer surface texture from the above two aspects.

[0059] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0060] The wafer grinding method provided by the embodiment of the present invention uses a thinning device to grind the wafer, and the grinding wheel of the thinning device uses a relatively soft grinding wheel, such as Figure 3 As shown, the method comprises the following steps:

[0061] S1, fix the wafer to be ground on the wafer holding table of the thinning equipment;

[0062] S2. Adjust the position of the grinding wheel of the thinning equipment into place;

[0063] S3, adjusting the rotation speed of the grinding wheel and the wafer table so that both the grinding wheel and the wafer table rotate at a low speed;

[0064] S4, using a grinding wheel to feed and grind the wafer to be ground in multiple stages until the wafer to be ground has completed a corresponding amount of removal.

[0065] It should be noted that the original grinding wheel of the thinning equipment uses a metal grinding wheel; in this solution, the thinning equipment uses a softer grinding wheel, such as a resin grinding wheel or a ceramic grinding wheel, so as to absorb the energy brought by the end jump, alleviate the vibration caused by the end jump, and make the vibration caused by the end jump less transmitted to the surface of the wafer, thereby reducing the generation of lines on the surface of the wafer; of course, although the thinning equipment uses a soft grinding wheel, the strength and rigidity of the grinding wheel must also be ensured;

[0066] In addition, in step 1 of the wafer grinding method provided in the present scheme, the wafer to be ground is adsorbed on the wafer holding table of the thinning equipment; in step S2, the center line of the inner and outer circular axes of the working surface of the grinding wheel (grinding wheel) is adjusted to the center position of the silicon carbide wafer; in step S3, the rotation speed of the grinding wheel and the wafer holding table is adjusted so that the grinding wheel and the wafer holding table both rotate at a low speed, that is, the rotation speed of the grinding wheel and the wafer holding table is lowered to reduce the frequency of the end jump of the grinding wheel and the wafer holding table, thereby reducing the probability of the generation of surface lines on the wafer, thereby inhibiting the generation of thinning lines on the wafer during the grinding process, thereby helping to improve the surface quality of the wafer; in step S4, the grinding wheel is used to feed and grind the wafer to be ground in multiple stages until the wafer to be ground has completed the corresponding removal amount, thereby completing the entire grinding process of the wafer to be ground; wherein, the grinding wheel can be fed and ground to the wafer to be ground in three stages, and the grinding wheel maintains a certain low rotation speed, the wafer holding table also maintains a certain low rotation speed, and the grinding wheel completes the corresponding removal amount of the wafer to be ground at the corresponding feed speeds of the three stages in turn, as described below for details.

[0067] That is to say, this scheme provides a new grinding method for thinning semiconductor substrates (silicon carbide wafers). On the one hand, by using a soft grinding wheel to absorb the energy brought by the end jump of the grinding wheel, the vibration caused by the end jump is transmitted to the surface of the wafer less; on the other hand, by adjusting the rotation speed of the grinding wheel and the wafer stage, the grinding wheel and the wafer stage are rotated at a low speed to reduce the frequency of the end jump of the grinding wheel and the wafer stage, thereby reducing the probability of the generation of surface lines on the wafer, and further reducing the generation of grinding lines on the wafer surface due to thinning, which can effectively alleviate the problem of end jump of the thinning equipment causing lines on the wafer surface, thereby helping to improve the yield of the wafer.

[0068] In this scheme, as also mentioned above, the grinding wheel of the thinning equipment can be a ceramic grinding wheel or a resin grinding wheel, which has a lower hardness than the original metal grinding wheel. This makes it easier to absorb the energy brought by the end jump, alleviate the vibration caused by the end jump, and reduce the vibration caused by the end jump transmitted to the surface of the chip, thereby helping to reduce the generation of surface texture of the chip.

[0069] In one embodiment of the present solution, that is, in step S3, the rotation speed of the grinding wheel is 1203-1216 rpm, and the rotation speed of the wafer table is 61-79 rpm;

[0070] In the step S4, the grinding wheel is used to feed and grind the wafer to be ground in multiple stages, including:

[0071] The grinding wheel is used to feed and grind the wafer to be ground in three stages; wherein the feeding speed of the grinding wheel in the first stage is 0.2-0.3 μm / min, the feeding speed in the second stage is 0.2-0.1 μm / min, and the feeding speed in the third stage is 0.1 μm / min.

[0072] It should be noted that in the above-mentioned implementation mode of the present scheme, that is, in step S3, the rotation speed of the grinding wheel can be 1203~1216rpm, and the rotation speed of the wafer table can be 61~79rpm, which can reduce the frequency of the grinding wheel and the wafer table end jumping, and then reduce the probability of the generation of surface lines on the wafer, that is, it can suppress the generation of thinning lines on the wafer during the grinding process, thereby helping to improve the surface quality of the wafer, and in step S4, the grinding wheel can be used to feed and grind the wafer to be ground in three stages; wherein, the feed speed of the grinding wheel in the first stage is 0.2~0.3μm / min, the feed speed in the second stage is 0.2~0.1μm / min, and the feed speed in the third stage is 0.1μm / min, which can enable the wafer to obtain a better grinding effect.

[0073] In another embodiment of the present invention, that is, in step S3, the rotation speed of the grinding wheel is 1217-1296 rpm, and the rotation speed of the wafer table is 53-83 rpm;

[0074] In the step S4, the grinding wheel is used to feed and grind the wafer to be ground in multiple stages, including:

[0075] The grinding wheel is used to feed and grind the wafer to be ground in three stages; wherein the feeding speed of the grinding wheel in the first stage is 0.2-0.3 μm / min, the feeding speed in the second stage is 0.2-0.1 μm / min, and the feeding speed in the third stage is 0.1 μm / min.

[0076] It should be noted that in the above-mentioned implementation mode of the present scheme, that is, in step S3, the rotation speed of the grinding wheel can be 1217~1296rpm, and the rotation speed of the wafer table can be 53~83rpm, which can also help to reduce the frequency of the grinding wheel and the wafer table end jumping, and thus can also help to reduce the probability of the generation of surface textures on the wafer, that is, it can help to suppress the generation of thinning textures on the wafer during the grinding process, thereby helping to improve the surface quality of the wafer, and in step S4, the use of the grinding wheel can be divided into three stages to feed and grind the wafer to be ground; wherein, the feed speed of the grinding wheel in the first stage is 0.2~0.3μm / min, the feed speed in the second stage is 0.2~0.1μm / min, and the feed speed in the third stage is 0.1μm / min, which can enable the wafer to obtain a better grinding effect.

[0077] In yet another embodiment of the present invention, that is, in step S3, the rotation speed of the grinding wheel is 1297-1314 rpm, and the rotation speed of the wafer table is 67-103 rpm;

[0078] In the step S4, the grinding wheel is used to feed and grind the wafer to be ground in multiple stages, including:

[0079] The grinding wheel is used to feed and grind the wafer to be ground in three stages; wherein the feeding speed of the grinding wheel in the first stage is 0.2-0.3 μm / min, the feeding speed in the second stage is 0.2-0.1 μm / min, and the feeding speed in the third stage is 0.1 μm / min.

[0080] It should be noted that in the above-mentioned implementation mode of the present scheme, that is, in step S3, the rotation speed of the grinding wheel can be 1217~1296rpm, and the rotation speed of the wafer table can be 53~83rpm, which can also help to reduce the frequency of the grinding wheel and the wafer table end jumping, and thus can also help to reduce the probability of the generation of surface textures on the wafer, that is, it can help to suppress the generation of thinning textures on the wafer during the grinding process, thereby helping to improve the surface quality of the wafer, and in step S4, the use of the grinding wheel can be divided into three stages to feed and grind the wafer to be ground; wherein, the feed speed of the grinding wheel in the first stage is 0.2~0.3μm / min, the feed speed in the second stage is 0.2~0.1μm / min, and the feed speed in the third stage is 0.1μm / min, which can enable the wafer to obtain a better grinding effect.

[0081] Of course, among the above three groups of process parameters, any one group of parameters can be used to suppress the generation of thinning lines on the wafer during grinding.

[0082] Specifically, in step S4, the amount of removal of the wafer to be ground in the first stage is greater than the amount of removal in the second stage, the amount of removal of the wafer to be ground in the second stage is greater than or equal to the amount of removal in the third stage, and the sum of the amount of removal of the wafer to be ground in the second stage and the amount of removal in the third stage is greater than or equal to 5μm. In other words, the wafer to be ground must meet the following conditions during grinding: the amount of removal in the first stage > the amount of removal in the second stage ≥ the amount of removal in the third stage, and the amount of removal in the second stage + the amount of removal in the third stage ≥ 5μm. In this way, the grinding is made from fast to slow, which not only ensures efficiency but also ensures quality, and the significance of the amount of removal in the second stage + the amount of removal in the third stage ≥ 5μm is to prevent the situation where the amount of grinding is too small and the surface is not completely ground.

[0083] Furthermore, the grinding wheel of the thinning device is arranged at an inclination relative to the wafer stage; wherein the edge of the grinding wheel close to the center of the wafer stage is at a large distance from the wafer stage, and the middle part is at a small distance from the wafer stage. In other words, the inclination of the grinding wheel relative to the wafer stage is as follows: the edge of the grinding wheel close to the center of the wafer stage is high, and the middle part of the grinding wheel is low, that is, the distance between the grinding wheel and the wafer stage gradually increases from the center point to the outside (the edge close to the center of the wafer stage), so that the center of the wafer can be slightly convex after grinding, which is convenient for subsequent polishing; in addition, the slightly convex center of the wafer after grinding also has the following benefits:

[0084] Stress concentration relief:

[0085] 1. After thinning, the wafer becomes extremely thin and brittle. The slightly convex shape can reduce stress concentration and reduce the risk of wafer breakage;

[0086] 2. Optimize machining residual stress;

[0087] 3. Adjust the internal residual stress distribution and improve the mechanical properties of the wafer;

[0088] Improve machining accuracy:

[0089] 1. Convenient for subsequent grinding and polishing;

[0090] 2. The slightly convex shape facilitates the control of the amount of material removed from the wafer surface, making the polished or ground surface more uniform and improving the surface finish;

[0091] 3. Higher processing tolerance.

[0092] Of course, the grinding wheel does not grind past the center of the wafer table during grinding, that is, the grinding wheel rotates along the radius on the wafer table to avoid uneven force on the grinding wheel.

[0093] Furthermore, if Figure 5 As shown in the figure, the fixed value of the inclination angle of the center point of the grinding wheel (the lower end face of the grinding wheel) relative to the wafer stage is 0, the calculated inclination angle threshold of the middle point relative to the wafer stage is -4 to -6μm, and the calculated inclination angle threshold of the edge point relative to the wafer stage is -35 to -40μm. After grinding at this angle, the surface shape of the wafer can present a good effect, and the final result can meet the TTV (total thickness deviation) ≤3μm, LTV (local thickness deviation) ≤1μm; among them, the inclination angle of each point of the grinding wheel relative to the wafer stage can be measured by the micrometer installed on the main shaft of the grinding wheel, and because the center point of the grinding wheel is 0, when the micrometer measures from the center to the outside, the distance between the grinding wheel and the wafer stage increases, the micrometer rises, and its value becomes negative.

[0094] In this solution, before step S1, the following steps are also included:

[0095] The grinding wheel is trimmed to make each tooth of the grinding wheel have the same height. In other words, the grinding wheel needs to be trimmed before grinding the wafer to be ground to ensure that each tooth of the grinding wheel has the same height, to ensure that each tooth can participate in the grinding in the initial stage, so that the grinding effect of the grinding wheel can be maximized.

[0096] Specifically, before step S1, the method further includes:

[0097] Place the wafer to be ground in an ethanol solution and perform ultrasonic cleaning for 5 minutes to remove dirt on the surface of the wafer to be ground and ensure the thinning and grinding accuracy;

[0098] After step S4, the method further includes:

[0099] The ground wafer was placed in an ethanol solution and ultrasonically cleaned for 5 minutes to remove the trace amount of coating remaining on the surface.

[0100] The present invention is further described below in conjunction with specific embodiments:

[0101] This solution mainly discloses a new grinding method for semiconductor substrate thinning, which relates to the field of semiconductor substrate processing technology. The processing parameters in the following three tables can effectively alleviate the grain problem caused by the grinding wheel of the thinning equipment and the end jump of the wafer stage, and the processing parameters in the table can be set by the numerical control system of the thinning equipment, and the processing parameters in Table 1, Table 2, and Table 3 are as follows:

[0102] Fine grinding spindle grinding wheel speed rpm 1203-1216 Table speed rpm 61-79 First stage feed speed μm / min 0.2-0.3 Second stage feed speed μm / min 0.2-0.1 The third stage feed speed μm / min 0.1 Wafer removal μm ＞15 Wafer polishing time s 6 Escape velocity μm / s 3 Escape distance μm 3～5 Processing materials SiC size inch 6 or 8

[0103] Table 1

[0104] Among them, under this processing parameter, the outer linear speed range of the grinding wheel spindle is: 18.88m / s~19.11m / s, and the outer linear speed range of the 8-inch wafer is: 0.64m / s~0.82m / s;

[0105] Fine grinding spindle grinding wheel speed rpm 1217-1296 Table speed rpm 53-83 First stage feed speed μm / s 0.2-0.3 Second stage feed speed μm / s 0.2-0.1 The third stage feed speed μm / s 0.1 Wafer removal μm ＞15 Wafer polishing time s 6 Escape velocity μm / s 3 Escape distance μm 3～5 Processing materials SiC size inch 6 or 8

[0106] Table 2

[0107] Among them, under this processing parameter, the outer linear speed range of the grinding wheel spindle is: 19.11m / s~20.35m / s, and the outer linear speed range of the 8-inch wafer is: 0.42m / s~0.65m / s;

[0108] Fine grinding spindle grinding wheel speed rpm 1297-1314 Table speed rpm 67-103 First stage feed speed μm / s 0.2-0.3 Second stage feed speed μm / s 0.2-0.1 The third stage feed speed μm / s 0.1 Wafer removal μm ＞15 Wafer polishing time s 6 Escape velocity μm / s 3 Escape distance μm 3～5 Processing materials SiC size inch 6 or 8

[0109] Table 3

[0110] Among them, under this processing parameter, the outer linear speed range of the grinding wheel spindle is: 20.36m / s~20.63m / s,

[0111] 8-inch wafer outer line speed range: 0.53m / s~0.81m / s.

[0112] Select any of the processing parameters in the above table to set, and then use the fine grinding spindle (grinding wheel) of the thinning equipment to process the silicon carbide wafer, so that the grinding wheel maintains a certain speed, the wafer maintains a certain speed, and the corresponding removal amount is completed at the set feed speed, and the entire wafer grinding process can be completed (such as Figure 4 as shown).

[0113] Among them, the above grinding process includes the following important points:

[0114] 1. The height and correction of the fine grinding wheel. The grinding wheel needs to be trimmed before processing to ensure that each tooth of the grinding wheel has the same height and that each tooth can participate in grinding in the initial stage.

[0115] 2. The inclination angle between the spindle plane (lower end face of the grinding wheel) and the wafer table is as follows: Figure 5 As shown, the center point: 0, the middle point: -4~-6μm, the edge point: -35~-40μm. After grinding at this angle, the wafer surface can present a good effect, and the final result can meet TTV≤3μm, LTV≤1μm.

[0116] 3. When grinding the wafer, the first stage removal amount must be greater than the second stage removal amount ≥ the third stage removal amount, and the second stage removal amount + the third stage removal amount must be greater than 5μm;

[0117] 4. Before and after grinding, the wafer must be placed in an ethanol solution and ultrasonically cleaned for 5 minutes to remove residual particles on the surface.

[0118] In addition, if Figure 6 and Figure 7 As shown in the figure, the 8-inch wafer ground using the parameters in Table 1 has TTV: 1.49μm, LTV: 0.83μm, Bow: 1.71μm, and Warp: 12.39, and the final results are all better than the product shipping standards; where TTV is the total thickness deviation, LTV is the local thickness deviation, Bow is the curvature, and Warp is the warpage.

[0119] like Figure 8 and Fig. 9 As shown in the figure, the 8-inch wafer ground using the parameters in Table 2 has TTV: 1.46μm, LTV: 0.82μm, Bow: 0.54μm, and Warp: 5.59, and the final results are all better than the product shipping standards.

[0120] like Fig.10 and Fig.11 As shown in Table 3, the 8-inch wafer ground using the parameters has TTV: 1.45μm, LTV: 0.83μm, Bow: 1.29μm, and Warp: 9.34, and the final results are all better than the product shipping standards.

[0121] In addition, after processing using the parameters in Table 1, the ScN & SZrO channels were observed using the Candela CS920 equipment. Fig.12 and Fig.13 As shown, there is no Figure 2 Same grinding texture.

[0122] After processing using the parameters in Table 2, the ScN & SZrO channels were observed using the Candela CS920 equipment. Fig.14 and Fig.15 As shown, there is no Figure 2 The same grinding lines, the white part on the right is a growth defect and has nothing to do with the processing effect.

[0123] After processing using the parameters in Table 3, the ScN & SZrO channels were observed using the Candela CS920 equipment. Fig.16 and Fig.17 As shown, there is no Figure 2 Same grinding texture.

[0124] Comparative Example 1:

[0125] Thinning of SiC wafers using unmodified process 1:

[0126] 1. Put it in ethanol solution and perform ultrasonic cleaning for 5 minutes to remove surface dirt and ensure the thinning and grinding accuracy;

[0127] 2. Specific processing parameters are: fine grinding spindle speed (grinding wheel speed) 2803-2903rpm, wafer table speed 241rpm, grinding wheel first stage feed speed 0.3μm / s, second stage feed speed 0.2μm / s, third stage feed speed 0.1μm / s, first stage removal 6μm, second stage removal 5, third stage removal 4μm, total removal 15μm;

[0128] 3. Fine grinding spindle inclination angle, center point: 0, middle point: -5μm, edge point: -40μm;

[0129] 4. Put it in ethanol solution and ultrasonically clean it for 5 minutes to remove the trace amount of paint remaining on the surface;

[0130] 5. After the subsequent double-sided CMP and single-sided CMP, send it for cleaning and then inspection.

[0131] like Fig.18 and Fig.19 As shown, the 8-inch silicon carbide single crystal polished wafer processed by the above method can achieve the following indicators: TTV: 3.2μm, LTV: 1.45μm, Bow: 1.25μm, Warp: 3.51;

[0132] After the 8-inch wafer is processed under this process route, there are obvious grinding lines, such as Fig. 20 and Fig.21 As shown, this poses certain risks to the back-end process.

[0133] Comparative Example 2:

[0134] Thinning of SiC wafers using unmodified process 2:

[0135] 1. Put it in ethanol solution and perform ultrasonic cleaning for 5 minutes to remove surface dirt and ensure the thinning and grinding accuracy;

[0136] 2. Specific processing parameters are: fine grinding spindle speed (grinding wheel speed) 2503rpm, wafer table speed 231rpm, grinding wheel first stage feed speed 0.3μm / s, second stage feed speed 0.2μm / s, third stage feed speed 0.1μm / s, first stage removal 5μm, second stage removal 4, third stage removal 3μm, total removal 12μm;

[0137] 3. Fine grinding spindle inclination angle, center point: 0, middle point: -6μm, edge point: -38μm;

[0138] 4. Put it in ethanol solution and ultrasonically clean it for 5 minutes to remove the trace amount of paint remaining on the surface;

[0139] 5. After the subsequent double-sided CMP and single-sided CMP, send it for cleaning and then inspection.

[0140] Among them, the wafer surface effect using the unimproved process 2 is as follows Fig. 22 and Fig.23 As shown, the surface damage effect of the wafer using the unmodified process 2 is as follows Fig.24 and Fig.25 As shown, under this process route, there are obvious grinding lines on the wafer after processing, which poses certain risks to the back-end process.

[0141] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0142] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A wafer grinding method, using a thinning device to grind a wafer, characterized in that: The grinding wheel of the thinning device adopts a soft grinding wheel, and the method comprises the following steps: S1, fix the wafer to be ground on the wafer holding table of the thinning equipment; S2. Adjust the position of the grinding wheel of the thinning equipment into place; S3, adjusting the rotation speed of the grinding wheel and the wafer table so that both the grinding wheel and the wafer table rotate at a low speed; S4, using a grinding wheel to feed and grind the wafer to be ground in multiple stages until the wafer to be ground has completed a corresponding amount of removal.

2. The wafer grinding method according to claim 1, characterized in that: The grinding wheel adopts a ceramic grinding wheel or a resin grinding wheel.

3. The wafer grinding method according to claim 1, wherein: In step S3, the rotation speed of the grinding wheel is 1203-1216 rpm, and the rotation speed of the wafer table is 61-79 rpm; In the step S4, the grinding wheel is used to feed and grind the wafer to be ground in multiple stages, including: The grinding wheel is used to feed and grind the wafer to be ground in three stages; wherein the feeding speed of the grinding wheel in the first stage is 0.2-0.3 μm / min, the feeding speed in the second stage is 0.2-0.1 μm / min, and the feeding speed in the third stage is 0.1 μm / min.

4. The wafer grinding method according to claim 1, wherein: In step S3, the rotation speed of the grinding wheel is 1217-1296 rpm, and the rotation speed of the wafer table is 53-83 rpm; In the step S4, the grinding wheel is used to feed and grind the wafer to be ground in multiple stages, including: The grinding wheel is used to feed and grind the wafer to be ground in three stages; wherein the feeding speed of the grinding wheel in the first stage is 0.2-0.3 μm / min, the feeding speed in the second stage is 0.2-0.1 μm / min, and the feeding speed in the third stage is 0.1 μm / min.

5. The wafer grinding method according to claim 1, wherein: In step S3, the rotation speed of the grinding wheel is 1297-1314 rpm, and the rotation speed of the wafer table is 67-103 rpm; In the step S4, the grinding wheel is used to feed and grind the wafer to be ground in multiple stages, including: The grinding wheel is used to feed and grind the wafer to be ground in three stages; wherein the feeding speed of the grinding wheel in the first stage is 0.2-0.3 μm / min, the feeding speed in the second stage is 0.2-0.1 μm / min, and the feeding speed in the third stage is 0.1 μm / min.

6. The wafer grinding method according to any one of claims 4 to 6, characterized in that: In step S4, the amount of material removed from the wafer to be ground in the first stage is greater than the amount removed in the second stage, the amount of material removed from the wafer to be ground in the second stage is greater than or equal to the amount removed in the third stage, and the sum of the amount of material removed from the wafer to be ground in the second stage and the amount of material removed in the third stage is greater than or equal to 5 μm.

7. The wafer grinding method according to claim 1, wherein: The grinding wheel of the thinning device is arranged obliquely relative to the wafer stage; wherein the edge of the grinding wheel close to the center of the wafer stage is at a large distance from the wafer stage, and the middle part is at a small distance from the wafer stage.

8. The wafer grinding method according to claim 7, characterized in that: The fixed value of the inclination angle of the center point of the grinding wheel relative to the wafer stage is 0, the calculated inclination angle threshold of the middle point relative to the wafer stage is -4 to -6 μm, and the calculated inclination angle threshold of the edge point relative to the wafer stage is -35 to -40 μm.

9. The wafer grinding method according to claim 1, wherein: Before step S1, the method further includes: The grinding wheel is trimmed so that the height of each tooth of the grinding wheel is the same.

10. The wafer grinding method according to claim 1, wherein: Before step S1, the method further includes: Place the wafer to be polished in an ethanol solution and ultrasonically clean it for 5 minutes; After step S4, the method further includes: The ground wafer was placed in an ethanol solution and ultrasonically cleaned for 5 minutes.

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