Wafer backside cleaning method

Abstract

Disclosed is a wafer backside cleaning method, comprising: using a wafer clamping part to hold a wafer, a gap being formed between the wafer clamping part and the wafer; injecting a protective gas into the gap at a first flow rate; adjusting the flow rate of the protective gas from the first flow rate to a second flow rate, and rotating the wafer under the drive of the first rotational speed of the wafer clamping part to clean the backside of the wafer; adjusting the rotational speed of the wafer clamping part from the first rotational speed to a second rotational speed, so that the wafer is driven by the wafer clamping part to rotate for the drying process; stopping rotating the wafer, adjusting the flow rate of the protective gas to the first flow rate again from the second flow rate, and then taking out the wafer; and stopping injecting the protective gas after the wafer is taken out. According to the present invention, adjusting the switching logic and flow rate of the protective gas can ensure that the front side of the wafer is not prone to adsorption of external impurities during a wafer backside cleaning process, thereby improving the wafer backside cleaning stability.

Claims

1. A wafer backside cleaning method, comprising: step S1, using a wafer clamping part to hold a wafer so that a backside of the wafer faces up and a front side of the wafer faces down, a gap being formed between the wafer clamping part and the front side of the wafer, a rotational speed of the wafer clamping part being 0 rpm; step S2, injecting a protective gas into the gap at a first flow rate to fill the gap with the protective gas; step S3, gradually adjusting the flow rate of the protective gas from the first flow rate to a second flow rate, starting to rotate the wafer clamping part to drive the wafer to rotate and the rotational speed of the wafer clamping part reaching a first rotational speed, and spraying cleaning liquid to the backside of the wafer for a backside cleaning process; step S4, adjusting the rotational speed of the wafer clamping part from the first rotational speed to a second rotational speed, so that the wafer is driven by the wafer clamping part to rotate for a drying process; step S5, after the drying process is completed, adjusting the wafer clamping part from the second rotational speed to 0 rpm to stop the wafer from rotating, adjusting the flow rate of the protective gas to the first flow rate from the second flow rate, and then taking the dried wafer out from the wafer clamping part; and step S6, stopping injecting of the protective gas after the wafer is taken out from the wafer clamping part.

2. The wafer backside cleaning method as claimed in claim 1, wherein the wafer clamping part is a mechanical clamping table, which directly acts on the wafer to hold the wafer.

3. The wafer backside cleaning method as claimed in claim 1, wherein the protective gas is an inert gas.

4. The wafer backside cleaning method as claimed in claim 1, wherein the wafer clamping part is a Bernoulli clamping table, and second through-holes are provided on the Bernoulli clamping table, which are used to inject a Bernoulli gas to keep a floating state of the wafer.

5. The wafer backside cleaning method as claimed in claim 1, wherein the first flow rate is greater than the second flow rate.

6. The wafer backside cleaning method as claimed in claim 1, wherein the second rotational speed is greater than the first rotational speed.

7. The wafer backside cleaning method as claimed in claim 1, wherein the first rotational speed is 300 rpm-1200 rpm.

8. The wafer backside cleaning method as claimed in claim 1, wherein the second rotational speed is 1500 rpm-4000 rpm.

9. The wafer backside cleaning method as claimed in claim 2, wherein a first through-hole is provided on the mechanical clamping table, which is used to inject the protective gas into the gap.

10. The wafer backside cleaning method as claimed in claim 4, wherein third through-holes are provided on the Bernoulli clamping table, which are used to inject the protective gas into the gap.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a schematic structural view of a wafer clamped by a mechanical clamping table provided in embodiment 1 of the invention.

(2) FIG. 2 is a schematic view of the rotational speed adjustment of a wafer clamping part provided by the invention.

(3) FIG. 3 is a schematic view of the flow rate adjustment of the protection gas N.sub.2 provided by embodiment 1 of the invention.

(4) FIG. 4 is a schematic structural view of a wafer clamped by a Bernoulli clamping table provided by embodiment 2 of the invention.

(5) FIG. 5 is a schematic view of the flow rate adjustment of Bernoulli N.sub.2 and lift N.sub.2 provided by embodiment 2 of the invention.

DETAILED DESCRIPTION OF EMBODIMENTS

(6) The following illustrates the embodiment of the invention by means of particular specific examples, and other advantages and effects of the invention can be readily understood by those skilled in the art from the contents disclosed in this specification. The invention may also be implemented or applied in various other specific embodiments, and various details in this specification may be modified or changed based on different views and applications without departing from the spirit of the invention.

(7) Referring to FIGS. 1 to 5, it should be noted that the diagrams provided by this embodiment are only schematically illustrate the basic concept of the invention. Although only components related to the invention are shown in the diagrams rather than being drawn according to the number, shape, and size of components in actual implementation, the shape, quantity, and proportion of each component can be changed arbitrarily during actual implementation, and the layout of the components may be more complex.

Embodiment 1

(8) Referring to FIGS. 1 to 3, embodiment 1 provides a wafer backside cleaning method in which a wafer w is placed on a wafer clamping part during a wafer backside cleaning process. As shown in FIG. 1, the wafer clamping part is a mechanical clamping table 1, which directly acts on the wafer w to clamp the wafer w, so that the backside (non-device side) of the wafer w faces up and the front side (device side) of the wafer w faces down, and a gap G is formed between the wafer w and the mechanical clamping table 1. A first through-hole 101 is provided at the center of the mechanical clamping table 1, which is used to inject a protective gas into the gap G, so as to realize the protection of the front side (device side) of the wafer w during the wafer backside cleaning process. The protective gas is an inert gas, among which the inert gas includes: N.sub.2 or helium, neon and other rare gases.

(9) As shown in FIGS. 2 and 3, the wafer backside cleaning method includes the following steps: Step S1, the manipulator places the wafer w to be cleaned on the mechanical clamping table 1 in a stationary state. The mechanical clamping table 1 clamps the wafer w so that the backside (non-device side) of the wafer w faces up and the front side (device side) of the wafer w faces down. Wherein, as shown in FIG. 2, the rotational speed of the mechanical clamping table 1 in the stationary state is 0 rpm. Step S2, as shown in FIG. 3, the protective gas is injected into the interior of the gap G between the wafer w and the mechanical clamping table 1 via the first through-hole 101 in accordance with the first flow rate, so that the interior of the gap G is rapidly filled with the protective gas. That is, when the backside (non-device side) of the wafer w in the cleaning process, the front side (device side) of the wafer w is in the protective gas all the time to protect the front side of the wafer w. In this embodiment 1, the protective gas is N.sub.2. Step S3, after the gap G is filled with protective gas, the flow rate of the protective gas through the first through-hole 101 is gradually adjusted from the first flow rate to the second flow rate, and the mechanical clamping table 1 starts to rotate and the rotational speed reaches the first rotational speed. Wafer w is rotated by the first rotational speed of the mechanical clamping table 1, at which time a cleaning liquid is sprayed onto the backside (non-device side) of the wafer w to clean wafer w backside.

(10) As shown in FIG. 3, the first flow rate of the N.sub.2 is greater than the second flow rate. In this embodiment 1, the first flow rate is 200 L and the second flow rate is 50 L.

(11) Wherein, in this embodiment 1, before the wafer w is cleaned, protective gas N.sub.2 with a relatively large flow rate is used to quickly fill the interior of the gap G between the front side of the wafer w and the mechanical clamping table 1.

(12) Step S4, as shown in FIG. 2, a rotational speed of the mechanical clamping table 1 is adjusted from the first rotational speed to the second rotational speed, and the wafer w is rotated under the second rotational speed of the mechanical clamping table 1 to dry wafer w. The first rotational speed is less than the second rotational speed.

(13) Wherein, the first rotational speed of the mechanical clamping table 1 is 300 rpm-1200 rpm; the second rotational speed of the mechanical clamping table 1 is 1500 rpm-4000 rpm. In embodiment 1, the first rotational speed is 500 rpm, and the second rotational speed is 2000 rpm.

(14) Step S5, after the wafer w is dried, the mechanical clamping table 1 is adjusted from the second rotational speed to a static state. That is, as shown in FIG. 2, a rotational speed of the mechanical clamping table 1 is gradually reduced from 2000 rpm to 0 rpm, so that the rotation of the high-speed rotating the wafer w gradually stops. As shown in FIG. 3, a flow rate of the protective gas N.sub.2 is adjusted from the second flow rate to the first flow rate again. Then, the manipulator takes the dried wafer w from the mechanical clamping table 1.

(15) Wherein, in this embodiment 1, before the manipulator takes the wafer w, a flow rate of the protective gas N.sub.2 is increased from the second flow rate to the first flow rate again. The purpose is to quickly dry the cleaning liquid remaining at the edge of the wafer w by increasing the gas flow rate, so as to avoid polluting the front side (device side) of the wafer w with the cleaning liquid remaining at the edge of the wafer w during the subsequent taking the wafer w by the manipulator.

(16) Step S6, as shown in FIG. 3, after the wafer w is taken out, turn off the protective gas N.sub.2 to stop injecting protective gas N.sub.2 into the gap G between the mechanical clamping table 1 and the wafer w.

(17) Wherein, during the entire cleaning and drying process of the wafer w, the protective gas N.sub.2 is filled with the front side (device side) of the wafer w. This can avoid the negative pressure on the front side of the wafer w being enhanced by the high-speed rotation of the wafer during the cleaning and drying process, which is easy to adsorb external impurities, thus achieving the protection of the front side of wafer w.

Embodiment 2

(18) Referring to FIGS. 2, 4, and 5, this embodiment 2 also provides a wafer backside cleaning method in which wafer w is placed on a wafer clamping part during a wafer backside cleaning process. As shown in FIG. 4, the wafer clamping part is a Bernoulli clamping table 2, which suspends and holds the wafer w, so that the backside (non-device side) of the wafer w faces up, the front side (device side) of the wafer w faces down, and a gap G is formed between the suspended wafer w and the Bernoulli clamping table 2. Second through-holes 201 are provided at the periphery of the Bernoulli clamping table 2, which is used to inject a Bernoulli gas to the front side of the wafer w, so as to keep a floating state of the wafer w by the Bernoulli clamping table 2. Third through-holes 202 are provided at the middle of the Bernoulli clamping table 2, which is used to inject a protective gas into the gap G between the suspended wafer w and the Bernoulli clamping table 2, so as to protect the front side of the wafer w, but also to adjust the height of the wafer w suspension during a wafer backside cleaning process.

(19) Wherein, in embodiment 2, both the Bernoulli gas and the protective gas are N.sub.2, or inert gases, such as helium, neon and other rare gases.

(20) As shown in FIGS. 2 and 5, a wafer backside cleaning method includes the following steps: Step S1, as shown in FIG. 4, the manipulator places the wafer w to be cleaned on the Bernoulli clamping table 2 in a stationary state, and supply the Bernoulli gas into the second through-holes 201. The Bernoulli clamping table 2 clamps the wafer w so that the backside (non-device side) of the wafer w faces up and the front side (device side) of the wafer w faces down. Wherein, as shown in FIG. 2, a rotational speed of the Bernoulli clamping table 2 in the stationary state is 0 rpm. Step S2, as shown in FIG. 5, the protective gas is injected into the interior of the gap G between the suspended wafer w and the Bernoulli clamping table 2 by the third through-holes 202 in accordance with the first flow rate, so that the interior of the gap G is rapidly filled with the protective gas. That is, when the backside of the suspended wafer w in the cleaning process, the front side (device side) of the wafer w is in the N.sub.2 atmosphere all the time to protect the front side of the wafer w. Step S3, after the gap G is filled with protective gas, the flow rate of the protective gas through the third through-holes 202 is gradually adjusted from the first flow rate to the second flow rate, and the Bernoulli clamping table 2 starts to rotate and the rotational speed reaches the first rotational speed. The suspended wafer w is rotated by the first rotational speed of the Bernoulli clamping table 2, at which time a cleaning liquid is sprayed onto the backside (non-device side) of the wafer w to clean the wafer w backside.

(21) As shown in FIG. 5, the first flow rate of the protective gas is greater than the second flow rate. In this embodiment 2, the first flow rate is 200 L and the second flow rate is 50 L.

(22) Wherein, in this embodiment 2, before the wafer w is cleaned, protective gas N.sub.2 with a relatively large flow rate (the first flow rate) is used to quickly fill the gap G between the suspended wafer w and the Bernoulli clamping table 2.

(23) During wafer w cleaning and drying process, the flow rate of the protective gas N.sub.2 is reduced (from the first flow rate to the second flow rate) in order to avoid the excessive flow rate of N.sub.2 affecting the height adjustment of the suspended wafer w by the Bernoulli clamping table 2.

(24) Step S4, as shown in FIG. 2, a rotational speed of the Bernoulli clamping table 2 is adjusted from the first rotational speed to the second rotational speed, and the wafer w is rotated under the second rotational speed of the Bernoulli clamping table 2 to dry the wafer w. The first rotational speed is less than the second rotational speed.

(25) Wherein, as shown in FIG. 2, the rotational speed of the Bernoulli clamping table 2 in the wafer w drying process greater than that of in the wafer w cleaning process. The reason is that the drying process of the wafer w needs to increase the rotational speed of Bernoulli clamping table 2 so as to quickly dry the cleaning liquid on the surface of the wafer w.

(26) Wherein, the first rotational speed of the Bernoulli clamping table 2 is 300 rpm-1200 rpm; the second rotational speed of the Bernoulli clamping table 2 is 1500 rpm-4000 rpm. In embodiment 2, the first rotational speed is 500 rpm, and the second rotational speed is 2000 rpm.

(27) Step S5, after the suspended wafer w is dried, the Bernoulli clamping table 2 is adjusted from the second rotational speed to a static state. That is, as shown in FIG. 2, a rotational speed of the Bernoulli clamping table 2 is gradually reduced from 2000 rpm to 0 rpm, so that the rotation of the high-speed rotating wafer w gradually stops. As shown in FIG. 5, a flow rate of the protective gas is adjusted from the second flow rate to the first flow rate again. Then, the manipulator takes the dried wafer w from the Bernoulli clamping table 2.

(28) Wherein, in this embodiment 2, since the gap G between the suspended wafer w and the Bernoulli clamping table 2 is small, the front side (device side) of the wafer w is easily destroyed when the manipulator takes the wafer w from the Bernoulli clamping table 2. Therefore, before the manipulator takes the wafer w, the flow rate of the protective gas N.sub.2 is increased again from the second flow rate to the first flow rate, which is used to increase the height of the gap G between the suspended wafer w and the Bernoulli clamping table 2, so as to facilitate the manipulator to taking the wafer w smoothly.

(29) Step S6, as shown in FIG. 5, after the wafer w is taken out, turn off the Bernoulli gas and at the same time turn off the protective gas.

(30) In the invention, during the entire cleaning and drying process of wafer w, the protective gas N.sub.2 is filled with the front side (device side) of the wafer w, so as to avoid the negative pressure on the front side of the wafer w being enhanced by the high-speed rotation of the wafer w during the cleaning and drying process, which is easy to adsorb external impurities, thus achieving the protection of the front side of the wafer w.

(31) Although the contents of the invention have been described in detail by the above preferred embodiments, it should be recognized that the above description should not be considered a limitation of the invention. Various modifications and substitutions that may be apparent to those skilled in the art are intended to be included within the scope of the protection of this invention as defined by the accompanying claims.