JP2014022678A - Wafer etching method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wafer etching method capable of etching the surface to be etched of a wafer to a uniform state.SOLUTION: A wafer etching method comprises the steps of: rotatably holding a wafer by a rotation holding device 10; and supplying an etchant to at least a central part of a wafer 1 by etchant supply means 20 and etching the wafer 1 by rotating it. The etching step etches an outer periphery of the wafer 1 at a higher temperature than a temperature of the central part of the wafer 1.

Description

  The present invention relates to a method for etching a wafer such as a semiconductor wafer.

  In the process of manufacturing a semiconductor device, wet etching may be performed on a semiconductor wafer such as a silicon wafer on which a large number of devices are formed. For example, when the back surface of the wafer is ground and thinned, the surface to be ground is wet-etched to remove distortion caused by grinding. In addition, in a TSV (Through Silicon Via: Si through electrode) wafer in which a plurality of through electrodes made of copper posts or the like are embedded in the wafer, the back surface is exposed to protrude from the back surface of the wafer. In some cases, wet etching may be performed.

  In performing wet etching on a wafer, a spin coating method is known in which an etching solution is dropped and supplied to the center of a rotated wafer, and the etching solution is spread over the entire surface to be etched by centrifugal force. (Refer to patent document 1 etc.).

JP 2000-217733 A

  In the etching process by the above spin coating method, when an etching solution having a high reactivity with respect to the wafer is used, a reaction (dissolution reaction or corrosion reaction) by the etching solution starts immediately after the supply. There is a problem that the etching amount is larger in the central portion than in the outer peripheral portion, and the etched surface is difficult to be etched in a uniform state.

  The present invention has been made in view of the above circumstances, and a main problem thereof is to provide a wafer etching method capable of etching a surface to be etched of the wafer in a uniform state.

  The method for etching a wafer according to the present invention includes a holding step for holding the wafer by a holding means for rotatably holding the wafer, an etching solution supplying means for supplying an etching solution to at least the central portion of the wafer, and rotating the wafer to rotate the wafer. An etching step for performing etching on the wafer, wherein the etching is performed in a state where the outer peripheral portion of the wafer is at a higher temperature than the central portion of the wafer.

  The present invention is an etching method by a spin coating method in which an etching solution is supplied to the central portion of a wafer while rotating the wafer by rotating the holding means with respect to the wafer held by the holding means. In the conventional spin coating method, the etching amount tends to be larger in the central portion of the wafer than in the outer peripheral portion as described above. Here, the etching process has a characteristic that the higher the temperature, the faster the etching reaction rate. Therefore, when the outer peripheral portion of the wafer is etched at a higher temperature than the central portion of the wafer as in the present invention, the etching reaction rate by the etching is faster in the outer peripheral portion than in the central portion. For this reason, as a result, the etching reaction between the central portion and the outer peripheral portion can be made equal, and the surface to be etched can be etched in a uniform state.

  In the etching step, in order to etch the outer peripheral portion of the wafer at a higher temperature than the central portion of the wafer, the following method is specifically mentioned.

  That is, as a first method, the etching supply means includes a first supply port that supplies the etching solution to the central portion of the wafer at a first temperature, and the etching solution is supplied to the outer peripheral portion of the wafer at the first temperature. By having a second supply port for supplying at a higher second temperature, the etching step is performed so that the outer peripheral portion of the wafer is hotter than the central portion of the wafer.

  Alternatively, as a second method, the holding means holds the wafer in a state in which the surface to be etched of the wafer is exposed and at least the outer peripheral portion of the back surface of the surface to be etched is exposed. By heating and injecting a fluid inert to the etching reaction to the outer peripheral portion of the back surface, the outer peripheral portion of the wafer is etched at a higher temperature than the central portion of the wafer.

  In addition, although said 1st method and said 2nd method may each be performed independently, they can also be performed simultaneously.

  In the present invention, the wafer is made of silicon, and the etching solution contains tetramethylammonium hydroxide (TMAH).

  According to the present invention, it is possible to provide an etching method for a wafer that can etch a surface to be etched of the wafer in a uniform state.

It is a perspective view which shows the holding | maintenance step of the processing method of the wafer which concerns on one Embodiment of this invention. It is a perspective view which shows the etching step of one Embodiment. It is a side view which shows the etching step of one Embodiment. It is a side view which shows the etching step of the processing method of the wafer which concerns on other embodiment of this invention.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
In one embodiment, first, a disk-shaped wafer 1 to be wet-etched is placed and held on a plurality of support plates 11 provided in the rotation holding device (holding means) 10 shown in FIG. 1 (holding step). . The wafer 1 is a semiconductor wafer 1 made of, for example, silicon, and one surface is an etched surface 1b. The rotation holding device 10 is accommodated in an etching chamber (not shown).

  The wafer 1 placed on the plurality of support plates 11 is held horizontally and rotatably. In this case, three support plates 11 are arranged at equal intervals in the circumferential direction, and rollers 12 that contact the outer peripheral surface of the wafer 1 are arranged between the support plates 11. A convex portion 11a protruding upward is formed at the center of the support plate 11, and the wafer 1 is positioned by the outer peripheral surface coming into contact with the side surface of the convex portion 11a. In this state, the entire surface to be etched 1b of the wafer 1 is exposed upward, and the outer peripheral portion of the back surface 1a, which is the lower surface, is exposed downward except for the mounting portion on the support plate 11.

  Each roller 12 has a rotating shaft 13 extending downward, and a driving belt 14 is wound around the rotating shaft 13. A driving roller 16 that is rotationally driven by a driving motor 15 is installed in pressure contact with the outer peripheral surface of the driving belt 14. When the driving roller 16 is rotationally driven in the direction of arrow A, the driving belt 14 is driven in the B direction. The rotation of the drive belt 14 is transmitted from the rotary shaft 13 to the roller 12 so that the wafer 1 rotates in the direction of arrow C.

  The wafer 1 is set on the support plate 11 with the surface to be etched 1b facing upward, and the outer peripheral surface is set in contact with the peripheral surface of each roller 12. Then, each roller 12 that rotates by rotating the drive motor 15 sends the outer peripheral surface of the wafer 1 in the circumferential direction by frictional force, whereby the wafer 1 is rotated.

  Next, while rotating the wafer 1 with the rotation holding device 10, the etching solution is supplied to the central portion of the etching target surface 1b of the wafer 1, and the etching solution is supplied to the entire etching target surface 1b by spin coating to perform etching. Apply (etching step).

  In the etching step, the etching is performed in a state where the outer peripheral portion is at a higher temperature than the central portion of the wafer 1. For this purpose, as shown in FIGS. 2 and 3, a first supply port 21 for supplying an etching solution L <b> 1 having a first temperature to the central portion of the wafer 1 as an etching supply means 20 above the wafer 1 and the wafer 1. And a second supply port 22 for supplying an etchant L2 having a second temperature higher than the first temperature is disposed on the outer peripheral portion of the first supply port. In this case, the second supply port 22 is positioned on both sides of one first supply port 21, and the three supply ports 21, 22, and 22 are arranged in a straight line.

  Regarding the temperature of the etching solution, for example, the first temperature, that is, the temperature of the etching L1 is set to about 60 to 70 ° C., and the second temperature, that is, the temperature of the etching L2 is set to about 75 to 90 ° C. Further, tetramethylammonium hydroxide (hereinafter referred to as TMAH) is used as the etching solutions L1 and L2. Further, as shown in FIG. 3, on the lower side of the wafer 1, a fluid G1 that is inert to the etching reaction is sprayed toward the central portion of the back surface 1a of the wafer 1 so that the etching solution L wraps around the back surface 1a. A central injection port 31 is provided for prevention. As the inert fluid G1, pure water, nitrogen gas, or the like is used.

  In the etching step, while rotating the wafer 1 as described above, the etching liquids L1 and L2 set at the above temperatures are dropped and supplied from the first supply port 21 and the second supply port 22, respectively. An inert fluid G <b> 1 is sprayed from the central spray port 31 to the center of the back surface 1 a of the wafer 1.

  The etching L1 supplied from the first supply port 21 is supplied dropwise to the central portion of the etching target surface 1b of the rotating wafer 1, and spreads to the outer peripheral side by centrifugal force. The central portion of the etching target surface 1b supplied with the etching L1 is etched by an etching reaction corresponding to the first temperature.

  On the other hand, the etching L2 supplied from the second supply port 22 drops on the outer peripheral portion of the surface 1b to be etched of the rotating wafer 1, and further spreads to the outer peripheral side by centrifugal force. The outer peripheral portion of the etching target surface 1b supplied with the etching liquid L2 is etched by an etching reaction corresponding to the second temperature. In this way, the entire surface to be etched 1b is etched by the etching liquids L1 and L2.

  Etchings L1 and L2 fall from the outer peripheral edge of the wafer 1, but the pressure of the inert fluid G1 sprayed to the back surface 1a side of the wafer 1 causes the etching liquid L1. L2 does not wrap around, and unnecessary portions such as the surface 1a and the side surface are prevented from being etched. Note that it is preferable to heat the inside of the etching chamber to about 50 ° C. during etching because the etching rate is increased and the processing speed is improved. When a predetermined etching time elapses, the etching process ends, the supply of the etching liquids L1 and L2 and the rotation of the wafer 1 are stopped, and the wafer 1 is unloaded from the rotation holding device 10.

  According to the present embodiment, since the temperature of the etching liquid L2 supplied to the outer peripheral part is higher than that of the etching liquid L1 supplied to the central part of the wafer 1, the etching reaction rate at the outer peripheral part is higher than that at the central part. Get faster. For this reason, the etching reaction between the central portion and the outer peripheral portion becomes equal, and as a result, the effect that the etched surface 1b is etched in a uniform state is exhibited.

  In particular, when the wafer 1 is made of silicon and the etching solutions L1 and L2 are the TMAH, an etching reaction occurs immediately after the supply of the etching solutions L1 and L2, so this embodiment is effective.

  In the above embodiment, the etching is performed by changing the temperature of the etching solution as a method for etching the outer peripheral portion at a higher temperature than the central portion of the wafer 1. In addition to this, the central portion and the outer peripheral portion of the wafer 1 itself are used. By giving a temperature difference to the above, the above-mentioned effect can be obtained more accurately, and it is extremely effective when a silicon wafer is etched with TMAH as described above.

  As a method of giving a temperature difference to the wafer 1 itself, as shown in FIG. 4, outer peripheral injection ports 32 are provided on both sides of the central injection port 31 on the back surface 1 a side of the wafer 1 held by the rotation holding device 10. The fluid G2, which is inert to the etching reaction, is heated and sprayed from the outer peripheral injection ports 32 toward the outer peripheral portion of the back surface 1a of the rotating wafer 1 from these peripheral injection ports 32.

  In this case, the temperature of the fluid G1 ejected from the central portion ejection port 31 is not heated and is set to a temperature equivalent to the atmosphere in the etching chamber, and the fluid G2 ejected from the outer peripheral portion ejection port 32 is ejected from the central portion. The temperature is higher than the temperature of the fluid G <b> 1 ejected from the port 31. As a result, the wafer 1 has a higher temperature at the outer peripheral portion than at the central portion, and the etching reaction rate is higher at the outer peripheral portion. Therefore, the etching reaction between the central portion and the outer peripheral portion becomes equivalent, and the etched surface 1b is etched in a uniform state.

  Further, the fluid G2 is jetted obliquely upward from the outer peripheral injection port 32 toward the outer peripheral direction, and therefore, it is possible to reliably obtain an effect of preventing the etching solution from flowing into the wafer back surface 1a. .

  In the form in which the temperature difference between the central portion and the outer peripheral portion is given to the wafer 1 itself by the inert fluids G1 and G2 injected from the respective injection ports 31 and 32 on the back surface 1a side shown in FIG. Even when the supply of the etching solution L2 from the second supply port 22 is stopped and the normal temperature etching solution L1 is supplied from the first supply port 21 in the central portion, the outer peripheral portion of the wafer 1 compared to the central portion of the wafer 1 Can be etched at a high temperature.

  DESCRIPTION OF SYMBOLS 1 ... Wafer, 1a ... Back surface of wafer, 1b ... Etching surface of wafer, 10 ... Rotation holding device (holding means), 20 ... Etching liquid supply means, 21 ... First supply port, 22 ... Second supply port, G1 , G2 ... fluid, L1, L2 ... etching solution.

Claims (4)

A wafer etching method comprising:
A holding step for holding the wafer with holding means for holding the wafer rotatably;
An etching step of supplying an etching solution to at least a central portion of the wafer by an etching solution supply means and rotating the wafer to etch the wafer; and
In the etching step, etching is performed in a state where the outer peripheral portion of the wafer is hotter than the central portion of the wafer.   The etching supply means supplies a first supply port for supplying the etching solution to the central portion of the wafer at a first temperature, and supplies the etching solution to the outer peripheral portion of the wafer at a second temperature higher than the first temperature. 2. The wafer according to claim 1, wherein the etching step is performed in a state where the outer peripheral portion of the wafer is at a higher temperature than the central portion of the wafer. Etching method. The holding means holds the wafer in a state where the etched surface of the wafer is exposed and at least the outer peripheral portion of the back surface of the etched surface is exposed,
In the etching step, etching is performed in a state where the outer periphery of the wafer is at a higher temperature than the central portion of the wafer by heating and spraying a fluid inert to the etching reaction on the outer periphery of the back surface of the wafer. The method for etching a wafer according to claim 1, wherein: The wafer is made of silicon,
The method for etching a wafer according to claim 1, wherein the etching solution contains tetramethylammonium hydroxide.

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