DE102004045447B4 - Mobile, electrostatic substrate holder and method for mounting a substrate on a mobile, electrostatic substrate holder - Google Patents

Abstract

Method for mounting a substrate (2) on a mobile, electrostatic substrate holder (1), wherein by means of a combination of at least one on the edge region of the boundary region between the substrate (2) and the substrate holder (1) on the side facing the substrate (2) a sealing ring (13) incorporated in the substrate holder (1) and drainage passages (12) introduced in the immediate vicinity thereof a liquid (11) penetrating between the substrate (2) to be supported and the substrate holder (1) along the inner edge of the at least one sealing ring (13) discharged through the drainage passages (12) and discharged outside the substrate holder (1).

Description

The This invention relates to a mobile, electrostatic substrate holder and to a method for mounting a substrate on a mobile, electrostatic substrate holder.

In contrast to stationary electrostatic substrate holders, mobile, transportable electrostatic substrate holders are used as mechanical carriers for thin substrates. These are detailed in EP 1 217 655 A1 . US 2002/0 110 449 A1 such as WO / 02 11 184 A1 described. By means of this subcarrier technology, the processing and handling of thin substrates on existing production facilities is greatly facilitated. Thin (<150 μm) and ultrathin (<50 μm) substrates are clamped on mobile chucks using electrostatic forces. The size and thickness of the combination of mobile electrostatic chuck and thin substrate is similar in size, dimensionally stable and thick as a normally thick substrate. As a result, production equipment can be used both for normally thick substrates and for thin substrates. The practical implementation of the methods for mobile electrostatic handling has led to the development of first mobile electrostatic substrate holders, so-called transfer ESC (see DE 203 11 625 U1 ). Electrostatic chucks are used in processes for the production of chips on silicon substrates (wafers). The use of stationary, electrostatic chucks is widespread in the plants, especially in production steps that take place under reduced pressure. These include etching, CVD and PVD processes. The use of alternative mounts, such as vacuum or Bernoulli chucks, is as in US 4,733,632 A or DE 100 62 011 A1 described, because of the lack of back pressure not possible here.

Thin wafers with functional Chips are typically made by finishing processed, abraded thick wafers at the end of the component process and wet or etched plasmachemisch be that the bare wafer back metallized and with a tempering step the manufacturing process is completed. The transfer ESC Technology avoids the problems of handling the fracture-prone and partly heavily bent or discarded wafers in that the still thick, not discarded wafer before grinding on one Transfer ESC is clamped and in all subsequent transport and processing steps of the thin Wafer always remains connected to a transfer ESC. That has to Result that now also processes and equipment can be used on which so far no thin Wafers were workable.

The previous solutions meet some technical and economic requirements for such mobile, electrostatic substrate holder only insufficient. Thus, the deficiency of the prior art design is that moisture enters between the transfer ESC and the substrate held, although at the edge of the transfer ESC special sealing rings are introduced, as in US Pat DE 203 11 625 U1 is described. Extensive wetting of the interfaces with the moisture reduces the holding force and can lead to premature detachment of the substrate from the transfer ESC.

When using the previously used transfer ESC on spin-etching systems, this can also lead to unwanted etching of the substrate surface as well as damage to the transfer ESC. Spin etchers are used for post-grinding relaxation or additional chemical thinning of the wafers. For this purpose, highly corrosive liquids are used. In 1 shows the basic structure of the known prior art. The wafers 2 be this on rotating supports 3 held and from above becomes liquid 4 fed by itself through rotation 7 evenly distributed on the wafer. These carriers often use a combined holding action. A centrally located seal 6 is for an effective vacuum mount 5 used and a ring nozzle 8th allows according to the Bernoulli principle (aerodynamic paradox) holding the discs on the edge, as in EP 0 611 273 B1 and EP 0 611 274 B1 described. That through these ring nozzles 8th outgoing gas 9 At the same time, it is used to blow off the liquid flowing out of the edge of the wafer, keeping it away from the back. For non-optimal settings of the gas pressure at the ring nozzles 8th or else, as in AT 407 312 B introduced steps in the discharge channel of the carrier can lead to a wetting of the wafer back through the liquid.

At the relaxation sets typically takes a material removal of about 5-15 microns and the thinning of Silicon wafers are typically removed 20-60 microns. Next to the relaxation etching is also when grinding with suspensions or during cleaning steps in rinsing baths or the like Ingress of moisture is problematic.

Of the Invention is based on the object, inexpensive mobile electrostatic Chucks (Transfer-ESC) produce the ingress of moisture in combination transfer ESC prevent with the wafer or influence so that continues to have a high holding power over a long period of time is preserved and no damage to the finished processed wafer or transfer ESC occurs.

This task is solved by a procedure for holding a substrate on a mobile, electrostatic substrate holder with the features of claim 1 and a mobile, electrostatic substrate holder with the features of claim 5.

preferred and advantageous embodiments are the subject of the dependent claims.

The use of seals associated with stationary electrostatic chucks has heretofore been considered primarily in the context of sealing cooling gases to cool the chucks in etching or deposition processes. So are in US 2004/0 055 540 A1 . US 2003/0 021 077 A1 and JP 09-275101 A various sealing solutions for cooling the chuck back of temperature-resistant ceramic chucks shown. But there are also conventional O-rings (see EP 0 669 644 B1 ), as well as temperature-resistant silicone rubber (see JP 2004 031 938 A ) to connect individual components of the Chucks together gas or liquid-tight. In US 5,761,023 a zone with higher gas pressure is used for temperature control. For electrostatic chucks with polyimide film systems, when used in plasma etching processes, the problem of film destruction by aggressive etching gases is a factor that determines the lifetime of these systems (see US Pat EP 0 693 771 B1 ). Numerous proposals exist to prevent the penetration of the etching gases into the space between the wafer and the electrostatic chuck. So come guard rings (see DE 298 13 326 U1 and EP 0 948 042 A1 ) as well as in the metallic body incorporated recesses (see EP 0 669 644 B1 ). Despite all efforts to prevent the penetration of moisture into the gap (wafer to transfer ESC) when using conventional transfer ESC on spin-etch systems by means of optimized seals, it is sometimes several millimeters (3-50 mm) wider Area where moisture penetrates. This phenomenon is much more pronounced in processed, processed wafers than in uncoated, unstructured wafers. This can be explained by the fact that a surface structure forms on the front side of the wafer during processing in the component process. This surface structure (relief) is designed differently at the edge of the wafer than in the middle of the wafer. Depending on the size and arrangement of the chips, different edge structures are created. Considering that often several types of different chips are produced on the production lines, one arrives at a large number of different reliefs. These different reliefs can not be completely sealed with just one universal seal. Whether the shape of the edge rounding of the wafers (see Semi Standards, eg MI 9-0699) has an influence here has not been investigated. Also, planarization of the surfaces by CMP (Chemical Mechanical Polish), as well as a large number of other devices, is not used.

It is known from test series that transfer ESC 1 with only 0.5 mm wide edge seal 13 similar sized, wetted areas we have transfer ESC without seal. Also, the closing of special, centrally located through holes 10 in the transfer ESC showed no improvement in wetting. Only through the combination of integrated seal 13 and introduced drainage ducts 12 a satisfactory solution has been achieved.

Further Details and advantages of the invention will become apparent from the following Description of preferred embodiments of substrate holder according to the invention based on the drawings.

1 shows the state of the art for holding standard thick, standard wafers on Bernoulli chucks.

2 Figure 11 shows the effect of moisture penetration into the interface between the thin wafer and the prior art transfer ESC.

3 represents the limited penetration of moisture into a narrow edge region of the substrate holder according to the invention.

4 shows the cross section of a typical structure of a transfer ESC according to the invention with drainages and buried back contacts.

5 shows the top view of a segment of a transfer ESC, wherein the arrangement of the drainage ducts according to the invention is shown.

In the first embodiment, the solution according to the invention of the problem is based on 3 described. A transfer ESC 1 holds the already ground wafer 2 , To perform a relaxation etch on a spin etch line, the transfer ESC 1 with electrostatically held wafer 2 on the carrier 3 stored. The transfer ESC is held 1 by means of applied vacuum 5 , Subsequently, the carrier 3 in rotation 7 added. To hold the edge areas is by means of an annular nozzle 8th a gas under the transfer ESC 1 directed. A nitrogen flow of 120 to 180 liters / minute leads to the formation of a further holding force according to the Bernoulli principle. The etchant introduced from above 4 spreads homogeneously on the wafer and within 30 seconds about 7 microns of thin wafer 2 etched. Due to capillary forces (due to large surface tensions) moisture is allowed to enter 11 between wafers 2 and transfer ESC 1 , By means of introduced drainage ducts 12 in the immediate vicinity of the seal 13 The penetrated moisture can be dissipated again. It is the through the ring nozzles 8th directed gas flow 14 according to the Venturi principle for generating a negative pressure in the drainage passages 12 used to the liquid 11 through the drainage passages 12 suck. A similar accelerated withdrawal of the liquid can also be achieved if instead of the described carrier a vacuum carrier is used.

In the following, second exemplary embodiment, the production of a 6 "transfer ESC will now be described in more detail. By means of multilayer technology, a plate capacitor assembly (inlay) with a diameter of 150.4 mm is produced. For this purpose, different thickness, copper-clad laminates and bonding layers (Pre-Preg) are combined so that multi-layer, high voltage resistant capacitor and electrode structures 15 result. The different layers are electrically connected to one another by means of galvanized plated-through holes. In 4 a typical cross section of a structure thus produced is shown. To ensure mechanical stability, fiberglass reinforced laminate is used 19 used. In the back of the transfer ESC 1 In addition, 100 to 300 microns deep holes are introduced, which is used to form the buried backside contact 17 to be used. Subsequently, a 1.2 mm wide sealing ring 13 as edge seal, z. B. as a polyimide ring applied. The structured electrodes and the applied edge seal result in a depression in the surface relief 20 , This depression is exploited to the penetrating liquid 11 merge immediately behind the sealing ring. In addition, drainage grooves (not shown here) can also be milled. Subsequently, the drainage ducts 12 produced by laser and / or drilling, by 240 holes at a distance of 1.5 ° with a diameter of 0.6 mm directly on the sealing ring 13 be introduced. At the same time, the through holes become 10 generated. This is followed by viscous isolation gel 16 on the backside contacts 17 applied. The cover dielectric 18 is then applied to both the front and the back by laminating one or more layers of 10 to 25 microns thick polyimide films. By means of another laser processing the closed drainage ducts become 12 and through holes 10 opened again. In principle, it is also possible to keep individual drainage passages and through-holes closed so that systems or process-specific modifications to the transfer ESC in the last production step are possible. That between the backside contact 17 and the polyimide film introduced viscous isolation gel, z. As silicone, allows a moisture insensitive sealing of the contacts. The contact pins pierce when contacting first the polyimide film, penetrate through the insulation gel 16 and then contact the backside contacts 17 , When pulling out the contact pins, the isolation gel flows back together and any adhering gel residues are stripped off the polyimide film.

For transfer ESC with increased Flatness requirements will become an additional sub-step, Grinding on a grinding or polishing machine, in the manufacturing process inserted. The Thus prepared transfer ESC's are typical for 500 V to 1500 V withstand voltage designed and are about 450-550 microns thick.

In 5 shows the top view of a segment of a transfer ESC, which has been optimized especially for use on spin etch systems with Bernoulli holders.

In summary can be determined by the combination of seals and drainage channels a cost-effective Transfer ESC can be made using an insert on conventional Spin-etching equipment allows. As moisture penetration between transfer ESC and wafer not completely by means of seals can be prevented, this is a solution for the use of the transfer ESC Technology arose, the penetration of liquid limited in only a small border area. A border area of 2 up to 3 mm can for the vast majority of processed wafers are tolerated. These is shown solution also transferable to other processes of chip manufacturing, where unwanted moisture can penetrate.

1

mobile, electrostatic substrate holder = transfer ESC

2

wafer, substratum

3

Carrier (vacuum / Bernoulli holder)

4

liquid from above

5

vacuum

6

seal of the carrier for the vacuum

7

rotation

8th

Ring nozzle gas flow → Bernoulli effect

9

gas flow for blowing off the liquid flow

10

Through Hole through the transfer ESC

11

penetrating Liquid / moisture between wafer and transfer ESC

12

drainage passage

13

Sewn seal

14

derived liquid (Drainage)

15

Capacitor- and electrode structure

16

viscous Insulation gel

17

Back contact

18

covering dielectric

19

glass fiber reinforced laminate

20

deepening in the surface relief

Claims (14)

Method for mounting a substrate ( 2 ) on a mobile, electrostatic substrate holder ( 1 ), wherein by means of a combination of at least one at the edge region of the boundary region between the substrate ( 2 ) and the substrate holder ( 1 ) on the substrate ( 2 ) facing side of the substrate holder ( 1 ) incorporated sealing ring ( 13 ) and in its immediate vicinity introduced drainage corridors ( 12 ) one between the substrate to be supported ( 2 ) and the substrate holder ( 1 ) penetrating liquid ( 11 ) on the inner edge of the at least one sealing ring ( 13 ) along the drainage passages ( 12 ) and discharged outside the substrate holder ( 1 ) is derived. Method according to claim 1, characterized in that the drainage of the penetrating liquid ( 11 ) from between the substrate ( 2 ) and substrate holder ( 1 ) is accelerated by generating a negative pressure by the substrate holder ( 1 ) on a Bernoulli holder ( 3 ) is held. Method according to claim 1, characterized in that the drainage of the penetrating liquid ( 11 ) from between the substrate ( 2 ) and substrate holder ( 1 ) by generating a negative pressure ( 5 ) is accelerated by the substrate holder ( 1 ) on a vacuum holder ( 3 ) is held. Method according to one of claims 1 to 3, characterized in that for a carrier ( 3 ) for holding the substrate holder ( 1 ) with back gas flow, the Venturi principle for generating a negative pressure ( 5 ) in the drainage ducts ( 12 ) is applied. Mobile, electrostatic substrate holder ( 1 ) on a support ( 3 ) for holding the substrate holder ( 1 ), wherein in an edge region of the boundary region between a substrate ( 2 ) and the substrate holder ( 1 ) on the substrate ( 2 ) facing side of the substrate holder ( 1 ) at least one sealing ring ( 13 ) and in its immediate vicinity drainage passages ( 12 ) which are substantially perpendicular to a front side of the substrate holder ( 1 ) are arranged so that when a negative pressure in the drainage passages ( 12 ) in the immediate vicinity of the at least one sealing ring ( 12 ) penetrating liquids ( 11 ) on the inner edge of the at least one sealing ring ( 13 ) along the drainage passages ( 12 ) and outside the substrate holder ( 1 ) are derivable, wherein the carrier ( 3 ) an annular nozzle ( 8th ) to form a holding force according to the Bernoulli principle. Substrate holder ( 1 ) according to claim 5, characterized in that the drainage passages ( 12 ) on the inside of the sealing ring ( 13 ), wherein the distance between the drainage passages ( 12 ) to the inside of the sealing ring ( 13 ) is smaller than 2 mm. Substrate holder ( 1 ) according to one of claims 5 to 6, characterized in that the distance between the drainage passages ( 12 ) is between 1 mm to 40 mm. Substrate holder ( 1 ) according to one of claims 5 to 7, characterized in that the width of the drainage passages ( 12 ) is between 0.1 to 2 mm. Substrate holder ( 1 ) according to one of claims 5 to 8, characterized in that the drainage passages ( 12 ) are formed as concentric holes. Substrate holder ( 1 ) according to one of claims 5 to 9, characterized in that the drainage passages ( 12 ) are formed as a slot. Substrate holder ( 1 ) according to any one of claims 5 to 10, characterized in that via buried backside contacts ( 17 ) of the substrate holder ( 1 ) a 5 to 30 μm thick cover dielectric ( 18 ) is applied from polyimide film. Substrate holder ( 1 ) according to claim 11, characterized in that between the backside contacts ( 17 ) and the deck dielectric ( 18 ) of the substrate holder ( 1 ) a viscous isolation gel ( 16 ) is introduced, which allows piercing with contact needles for contacting and closes again after pulling out the contact pins. Substrate holder ( 1 ) according to one of claims 5 to 12, characterized in that an integrated plate capacitor structure of the substrate holder ( 1 ) comprises structured, copper-clad laminates connected by means of connecting layers, and an internal electrical contacting by means of galvanized plated-through holes is provided. Substrate holder ( 1 ) according to claim 13, characterized in that the surfaces of the plate capacitor structure of the substrate holder ( 1 ) are isolated by one or more 5 to 50 microns thick laminated films.