US3645229A

US3645229A - Rotational mechanism

Info

Publication number: US3645229A
Application number: US63351A
Authority: US
Inventors: Richard R Phinney
Original assignee: International Business Machines Corp
Current assignee: International Business Machines Corp
Priority date: 1970-08-13
Filing date: 1970-08-13
Publication date: 1972-02-29
Anticipated expiration: 1989-02-28
Also published as: GB1348708A; DE2135564B2; DE2135564A1; JPS5035627B1; DE2135564C3; CA953099A; FR2101512A5

Abstract

A rotational mechanism is used, e.g., in a vacuum deposition apparatus, for suspending a substrate holder above its stationary supports for rotation free of any bearings within a heated portion of a vacuum chamber. At the beginning of the vacuum deposition cycle a shaft in the rotational mechanism is rotated to enable the mechanism to engage the substrate holder and lift it above its stationary supports due to inertia of the substrate holder. The substrate holder is then rotated during the vacuum deposition, after which the direction of rotation of the shaft is reversed, and the substrate holder is lowered onto its support member, again due to inertia, thus eliminating bearing contact among the rotational mechanism, the substrate holder, and the stationary supports during the vacuum deposition.

Description

Unite States Patent Phinlney [451 Feb. 29, 1972 [54] ROTATIONAL MECHANISM [72] Inventor: Richard R. Phinney, Milton, Vt.

[73] Assignee: International Business Machines Corporation, Armonk, N.Y.

[22] Filed: Aug. 13, 1970 [21] Appl. No.: 63,351

Richison et al. ..l92/94 X Primary Examiner-Morris Kaplan A ttorneyI-Ianifin and Jancin [57] ABSTRACT A rotational mechanism is used, e.g,, in a vacuum deposition apparatus, for suspending a substrate holder above its stationary supports for rotation free of any bearings within a heated portion of a vacuum chamber. At the beginning of the vacuum deposition cycle a shaft in the rotational mechanism is rotated to enable the mechanism to engage the substrate holder and lift it above its stationary supports due to inertia of the substrate holder. The substrate holder is then rotated during the vacuum deposition, after which the direction of rotation of the shaft is reversed, and the substrate holder is lowered onto its support member, again due to inertia, thus eliminating bearing contact among the rotational mechanism, the substrate holder, and the stationary supports during the vacuum deposition.

14 Claims, 3 Drawing Figures ROTATIONAL MECHANISM BACKGROUND OF THE INVENTION 1. FIELD OF THE INVENTION The invention relates to the field of rotational systems adapted for use within, e.g., vacuum environments and more particularly to rotational systems for use within vacuum deposition systems. More particularly, it relates to a rotation mechanism in which inertia of a member to be rotated is utilized to raise and lower the member with respect to stationary supports.

2. DESCRIPTION OF THE PRIOR ART In the semiconductor industry many depositions are performed in vacuum. These depositions are of varying materials, but often involve vacuum evaporation of metals to form interconnection metallurgy on integrated circuits. The deposition material is deposited on relatively large silicon wafer substrates containing many individual integrated circuits. In order to produce deposits with the desired characteristics it is generally necessary to heat the substrates as well as the source of the deposition material. Because of the time and costly equipment involved, it is common practice to process many substrates at one time.

In order to obtain deposits having a uniform thickness over each substrate and of the same thickness from one substrate to another, it is the general practice to mount the substances on a large substrate holder which is rotated during the deposition process. The rotation of the substrate holder provides even deposition over all substrates from a much smaller and more controllable deposition source than would be possible without the rotation. However, the rotation of the substrate holder is not without problems.

Because of the high heat required for proper vacuum evaporation, and contamination of bearings by the deposition material, bearings within the vacuum chamber for subject to a rapid wear rate and a consequent short lifetime. Because of the rapid wear rate, excessive maintenance is required to maintain system operation.

Although reduced bearing life is a problem, a more serious problem is the introduction of contaminating impurities into the integrated circuits. If the bearings are not lubricated, the heat and vacuum conditions quickly lead to particles being rubbed off the bearings. These particles in contact with the substrates form impurities in the integrated circuits. If the bearings are lubricated to prevent bearing wear, then the lubricant evaporates under the high heat and vacuum conditions and deposits on the substrates as a contaminating impuritv.

For these reasons, bearing wear and contamination present serious quality control problems, as well as being significant factors in the cost of maintaining production equipment in usable condition.

OBJECTS A primary object of the present invention is to enable uniform vacuum deposition to be performed in an uncontaminated environment without requiring frequent maintenance of the vacuum deposition system.

Another object of the invention is to improve the manner of supporting a rotatable substrate holder so as to result in substantially no wear, without the introduction of contaminating lubricants.

Still another object of the invention is to provide a mechanism for rotating a member which will raise the member to be rotated from stationary supports as a result of the inertia ofthe member to be rotated.

Yet another object of the invention is to eliminate bearing contact in all heated areas of a vacuum deposition apparatus in which a substrate holder is rotated.

SUMMARY The above objects are accomplished by providing a novel suspension and rotation or pickup mechanism as described herein. As in prior art systems a vacuum chamber contains a heated deposition source and means for heating the substrates for proper deposition. The substrates are mounted on a substrate holder which rests on a stationary support means attached to the vacuum housing. The suspension and rotation mechanism includes a rotatable housing mounted within the vacuum chamber and connected by a shaft to a suitable rotational drive means. A retraction means responsive to the inertia of the substrate holder is coupled to the rotatable housing. A releasable latch means has a latch member attached to the retraction means and an engaging member attached to the substrate holder. The retraction means provides for axial movement of the latch member toward and away from the substrate holder support means.

The rotational mechanism is operated by rotating the shaft and housing to cause the releasable latch means to engage, thus coupling the rotational mechanism to the substrate holder. Continued rotation of the shaft and the housing causes the retraction means to raise the substrate holder from its supports, due to the inertia of the substrate holder and friction between the substrate holder and its supports while they are still in contact. Once the inertia of the substrate support has been overcome, it stops raising and rotates at the same speed as the shaft and housing. When it is no longer desired to rotate the substrate holder, the direction of rotation of the shaft and housing is reversed. Due to the rotational inertia of the rotating substrate holder, the retraction means lowers the substrate holder back onto its supports, and the releasable latch means disengages to separate the rotational mechanism and the substrate holder.

When the substrate holder is picked up and rotating at full speed, there is no bearing contact among the rotational mechanism, the substrate holder, or the supports for the substrate holder. This makes the rotational mechanism especially suited for use in a vacuum environment, where bearing contact is a problem. However, the rotational mechanism should find application in a wide variety of other environments as well.

The above and other objects and advantages of the invention will be apparent from the following more particular description of the preferred embodiment of the invention, as illustrated in the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a partial section of a preferred embodiment of the invention in perspective showing the rotational mechanism in a vacuum deposition system prior to engagement with a substrate holder;

FIG. 2 is a view of the rotational mechanism similar to FIG. 1, but with the mechanism in the initial stage of engagement of the substrate holder; and

FIG. 3 is a view of the rotational mechanism as in FIG. 2, but with the substrate holder fully engaged and raised by the mechanism.

DETAILED DESCRIPTION A vacuum deposition system including a preferred embodiment of a rotational mechanism 130 are shown in partial section and perspective in FIG. I. A vacuum chamber is shown generally at and is used for performing the vacuum deposition process. Within the chamber is a support means 108 for supporting a substrate holder 300. Also mounted in the chamber is a deposition source 110 and a heating means 112 for heating substrates (not shown) mounted on substrate holder 300 to obtain proper deposition. The rotational mechanism is attached to shaft 128 which is rotatably mounted through a vacuum seal or rotary feedthrough (not shown) in the top of the chamber 100 and is connected to suitable drive means such as a motor (not shown). The function of drive shaft 128 is to support and rotate the mechanism 130. The vacuum seal tightly grips the shaft 128 to prevent leakage to the inside of the vacuum chamber 100. The seal is not subject to much load because the support bearings i.e., the bearings which support the weight of the shaft and constrain it to rotate about its axis, are outside the vacuum chamber. Thus, the seal is not subject to significant wear. The vacuum seal is the only bearing surface contacting the inside of the vacuum chamber 100 during rotation of the substrate holder 300, and it may be suitably shielded to protect it from heat and to keep contaminants from it from reaching substrates on the substrate holder 300.

The mechanism 130 has a generally cylindrical housing 140 rigidly mounted to the drive shaft 128. The housing 140 has a generally cylindrical cavity 145 within it.

A retraction means 165 is disposed in the cavity 145 for raising and lowering a releasable latch means 210. The retraction means includes a nut 170 and a screw 190. The nut 170 is generally cylindrical in shape except for a keyway 176 which engages key 152 mounted on the wall of housing 140 within cavity 145. The key and keyway forces the nut 170 to rotate with housing 140, but allows the nut 170 to slide up and down inside the cavity 145. Bottom plate 154 disposed at the lower end of cavity 145 acts as an abutment to prevent nut 170 from coming out of the cavity 145.

The nut has an inner threaded surface 172 which mates with an outer threaded surface 192 of screw 190. The screw 190 has a reduced diameter section 194 slidably fitted in passageway 155 in bottom plate 154. Screw 190 is dimensioned so that shoulder 200 of the screw will rest on bottom plate 154 when the screw is in the position shown.

Compression coil spring 290 is located in the cavity 145 and exerts pressure between the top of the nut 170 and a surface 291 of housing 140 at the top of cavity 145 at all times. Thus, the spring urges nut 170 downward, assuring that shoulder 200 of screw 190 rests on bottom plate 154 when the nut is backed up, so as to provide resistance to turning the screw.

Releasable latch means 210 includes a rod 212 supported by and positioned perpendicular to the axis of screw 190 and hook-shaped dogs 214 on substrate 300 adapted to be engaged by rod 212 to couple the rotational mechanism 130 to the substrate holder 300 which is to be rotated.

A means for activating the releasable latch means 210 is provided by the retraction means 165, the housing 140, the substrate holder 300 and the spring 290. When shoulder 200 of screw 190 rests on bottom plate 154, the rod 212 and dogs 214 are in an engageable position. Rotation of housing 140 in a clockwise direction turns nut 170, which turns screw 190 until the rod 212 strikes the dogs 214, as shown in FIG. 2, which remain stationary because of the inertia of substrate holder 300 and friction between it and its support means 108. The nut then continues to turn with housing 140 which raises the rod 212 into the hook portions of dogs 214. Upon continued rotation of member 140 after engagement of rod 212 and dogs 214, the substrate holder is raised from its support means because the combination of continued friction between it and the support means 108, and its inertia, prevents screw 190 from rotating with nut 170, and screw 190 therefore moves upward within nut 170. Substrate holder 300 continues to be raised until its inertia is overcome and it is rotating at the same speed as housing 140, and screw 190 no longer moves upward within nut 170. The housing 140, retraction means 165, the releasable locking means 210 and the substrate holder 300 now rotate as a single unit, in the position shown in FIG. 3.

In order to increase the efiective weight of the substrate holder 300 prior to raising it, a lifting resistance means 230 is provided for resisting the lifting of the substrate holder 300 in order to assist in raising the substrate holder 300 to a precisely predetennined extent each time it is raised. The lifting resistance means includes a bearing 232, a spring 240, and a checking sleeve 250. The bearing 232 has an upper bearing member 234 mounted on the upper surface of housing 140. The upper bearing member 234 is attached to housing 140 so that it must rotate at the same speed as the shaft 128 and the housing 140. The bearing 232 has a lower bearing member 236 which is free to rotate with respect to the housing 140 to that the spring 240 and checking sleeve 250 will remain stationary with respect to the substrate holder 300 at all times. The spring 240 has its upper end pressing against the lower surface of the lower bearing member 236 and its lower end pressing against the top of the checking sleeve 250. The checking sleeve 250 is a hollow stepped cylinder having a large diameter section 252 at the bottom and a reduced diameter section 254 at the top. The step forms a lower shoulder 258 and an upper shoulder 260. The spring 240 presses on shoulder 260 at all times and shoulder 258 rests on outer support shoulder 158 of housing 140 when the mechanism is not in contact with the substrate holder. The reduced diameter cylindrical portion 254 is adjacent to the outer cylindrical surface of housing 140 and serves to guide checking sleeve 250 and to retain its vertical orientation. The lower surface of section 252 of checking sleeve 250 presses against the substrate holder 300 to apply the lifting resistance to the substrate holder. The lifting resistance means 230, by constantly pressing down on the substrate holder 300, assures that the releasable latch means 210 will remain locked as long as substrate holder 300 is not resting on support means 108 and helps to determine the height to which the substrate holder is raised above support means 108.

Substrate holder 300 has a flat shape near its center and a thin dome shaped portion upon which the substrate holding locations (not shown) are arranged. Although the embodiment shown is dome shaped because of the pattern of the deposition source, it could be flat if the pattern of the deposition source required a flat surface.

OPERATION Succeeding stages in an operation cycle are shown in FIGS. 1 through 3. The mechanism 130, mounted with shaft 128 through vacuum chamber 100, is adjusted by turning screw 190 so that its shoulder 200 rests on plate 154 and rod 212 is positioned to clear dogs 214. FIG. 1 shows the rotational mechanism 130 in contact with the substrate holder. As the chamber and the mechanism is lowered into the position shown in FIG. 1, the checking sleeve 250 makes contact along its lower surface with the substrate holder 300. Further lowering of the top of the housing compresses spring 240 as the mechanism 130 is pressed down toward the substrate holder. When fully lowered into engageable relationship as shown in FIG. 1, the top of the rod 212 is lower than the hookshaped openings in the dogs 214 on the substrate holder 300. With the vacuum chamber 100 now in position, conventional vacuum deposition pumpdown is carried out.

The drive means (not shown) is now started to rotate the drive shaft 128 and the rotatable support member in a clockwise direction at a slow speed, preferably at about 8 rpm. to preventjarring of the substrates. The checking sleeve 250, the spring 240 and the lower bearing member 236 remain stationary with the substrate holder 300. Nut is constrained to rotate with the housing 140 because of the key 152 and the keyway 176. As shown in FIG. 2, the screw turns with the nut 170 until the rod 212 strikes the back of the opening in dogs 214. Once the rod 212 strikes the dogs 214 the screw 190 stops turning because of the inertia of the substrate holder 300 and the friction between the substrate holder and its supports 108. Continued rotation of housing 140 turns the nut 170 downward on the screw 190 until the nut 170 strikes bottom plate 154. Until nut 170 strikes bottom plate 154, a rotational force to screw 190 is applied to assure that rod 212 remains firmly seated in dogs 214.

The check sleeve 250, the spring 240, and the lower bearing member 236 now remain stationary, while the nut continues to advance on screw 190, thereby raising the screw 190 through nut 170, and therefore raising the rod 212 up into the hook-shaped portion of the dogs 214, as shown in FIG. 2.

Referring to FIG. 3, once the rod 212 has fully engaged the dogs 214 the continued advance of the nut 170 on screw 190 raises the substrate holder 300 off support means 108.

Since the substrate holder is no longer in frictional contact with supports 108 and the inertia of the substrate holder begins to decrease, the screw 190 will start to rotate with the nut 170. If the screw advances, the substrate holder is lifted and if the screw turns with the nut, the substrate holder must also turn with the nut. The combination of the weight of the substrate holder 300 and the force exerted through checking sleeve 250 by spring 240, resists the vertical movement of the substrate holder 300. Thus, the height to which the substrate holder is raised depends on a combination of the strength of spring 240, and the inertia or weight of the substrate holder 300. Therefore, if a different height is desired, the strength of spring 240 is merely changed. As the screw advances and raises the substrate holder, the substrate holders rotational speed increases until it is the same as that of the housing 140. When the substrate holder 300 reaches the speed of the housing the screw will have stopped advancing and the entire pickup mechanism rotates as a single unit with the substrate holder. Vacuum deposition now can take place.

If it is desired to do so, substrate holder 300 could be raised further from supports 108 than shown in FIG. 3 by merely increasing the rotation of shaft 128 from, for example 8 rpm, to 16 r.p.m. The rotational inertia of substrate holder 300 would cause screw 190 to advance further in nut 170 until the rotation of substrate holder 300 again matched that of shaft 128. After deposition has been completed, it is desired to return substrate holder 300 on supports 108. The drive means (not shown) for shaft 128 is reversed, preferably at a high speed such as 40 rpm. for a short time, such as one-half second, to start the screw 190 lowering the substrate holder. The motor is then run backward at a slower speed, such as 8 r.p.m., until the nut is retracted and the apparatus returned to the position shown in FIG. 2. The particular speeds depend on the characteristics of the spring 240 and are best determined experimentally.

in further explaining what takes place when the motor is reversed, rotational inertia keeps the substrate holder 300 rotating in the forward direction when the motor is first reversed. Thus, screw 190 starts downward toward supports 108. As the screw advances downwardly, the inertia of the substrate holder is overcome and it desirably stops rotating just before it comes to rest on its supports 108.

While the motor is still running backward and after the substrate holder is resting on its supports as shown in FIG. 2 the screw 190 continues to move downward until the rod 212 disengages from the dogs 214. After the rod disengages from the dogs, the screw 190 turns until the rod 212 strikes the back sides of the adjacent dogs. Once the rod 212 hits the backs of the dogs 214, the screw stops turning and the screw advances downwards until its shoulder 200 rests on the bottom plate 154, as shown in FIG. 1. From there on, the nut 170 retracts upwards through the cavity 145 until the drive shaft 128 stops, thus providing lost motion to allow time to stop the motor.

Now, returning to the deceleration step in the deposition cycle, the substrate holder 300 is decelerated to return to its sup port means 108 without rotational motion. This prevents jarring, scraping of the support means 108 or displacement ofthe substrates (not shown) on the substrate holder 300. The deceleration is accomplished by the reverse drive applied to the drive shaft 108. The reverse drive, combined with the force applied by spring 240, determines the rate of deceleration of the substrate holder, and should be experimentally determined so that the substrate holder 300 is not rotating when returned to its support means 108.

The entire engaging, lifting, lowering and disengaging operations consume a small proportion of the total time the system operates during a vacuum deposition run, and is the only time that bearing contact exists in the rotational mechanism T30. These operations, as well as rotation of the dome when engaged and lifted, may therefore be carried out under vacuum deposition conditions without causing substantial wear to the rotational mechanism. If desired, the engaging, lifting, lowering and disengaging operations may be carried out under atmospheric conditions, but this is not necessary.

This substrate holder pickup mechanism results in permitting a large number of runs to be performed before rebuilding of the deposition equipment becomes necessary. With the pickup device of the invention, 700 production runs have been achieved without rebuilding the equipment, thereby representing a significant advance over other known vacuum deposition systems.

While the invention has been particularly shown and described with reference to a preferred embodiment thereof, it will be understood by those skilled in the art that various changes in form and details may be made without departing from the spirit and scope of the invention.

1 claim:

1. An article rotational mechanism comprising:

rotatable retraction means responsive to the inertia of an article to be rotated to move the article to be rotated from an initial position, then to rotate the article, and

means for coupling the article to be rotated to said retrac' tion means.

2. The apparatus of claim 1 wherein the retraction means is a nut and screw which are constrained to rotate with respect to one another by the rotational inertia of the article to be rotated to move the article to be rotated from the initial position, then which rotate together to rotate the article.

3. The apparatus of claim 1 wherein said retraction means is responsive to the rotational inertia of the rotating article when the article is rotating in a forward direction and a portion of the rotatable retraction means is rotating in a reverse direction so as to return the article to its initial position.

4. The apparatus of claim 1 wherein said means for coupling the article to be rotated to said retraction means is releasable and comprises a latch member coupled to said retraction means and a means engageable with said latch member coupled to the article to be rotated.

5. The apparatus of claim 1 additionally comprising: means tending to restrain the retraction of said rotatable retraction means.

6. An article suspension and rotation apparatus comprising:

a rotatable housing;

retraction means, responsive to the rotational inertia of an article to be rotated which rests on a stationary support for the article from its support, coupled to said rotatable housing;

a latch member coupled to said retraction means; and

means, releasably engageable with said latch member, coupled to the article to be rotated.

7. The apparatus of claim 6 wherein the retraction means is a nut and screw which are constrained to rotate with respect to one another by the rotational inertia of the article to be rotated to move the article from its support, then rotate together to rotate the article.

8. The apparatus of claim 7 wherein said retraction means is responsive to the rotational inertia of the rotating article when the article is rotating in a forward direction and part of the retraction means is rotating a reverse direction so as to return the article to be rotated to its support.

9. A vacuum deposition system comprising:

a vacuum chamber;

a deposition material source mounted in the vacuum chamber;

a substrate holder in the vacuum chamber;

support means in the vacuum chamber for supporting the substrate holder; and a mechanism in said vacuum chamber for suspending and rotating the substrate holder, said mechanism having;

a rotatable housing;

retraction means rotatable with said rotatable housing; and

releasable latch means engageable by rotation of said retraction means for coupling the substrate holder to said retraction means;

said retraction means being responsive to the inertia of the article to be suspended when the rotatable housing is rotated so as to suspend the article prior to its being rotated, then rotate together with said rotatable housing said first member and adapted for engagement with an arso that said mechanism and substrate holder rotate ticle having a velocity different from that of said rotating together. means.

10. A system as in claim wherein said releasable lat h 12. A mechanism as set forth in claim 11 wherein said first means comprises a latch member and an engaging member; 5 member is a nut and said second member is a screw adapted to and rotation of said retraction means brings the latch and encooperatively engage Said gaging members im engagemem 13. A mechanism as set forth in claim 12 wherein said nut is 11 A i l rotation mechanism comprising; adapted to slide along the axis of said rotating means.

14. A mechanism as set forth in claim 11 wherein said artirotating means; and

l0 cle 1s a stationary article.

retraction means having a first member rotatable by said rotating means and a second member threaded within

Claims

1. An article rotational mechanism comprising: rotatable retraction means responsive to the inertia of an article to be rotated to move the article to be rotated from an initial position, then to rotate the article, and means for coupling the article to be rotated to said retraction means.

6. An article suspension and rotation apparatus comprising: a rotatable housing; retraction means, responsive to the rotational inertia of an article to be rotated which rests on a stationary support for the article from its support, Coupled to said rotatable housing; a latch member coupled to said retraction means; and means, releasably engageable with said latch member, coupled to the article to be rotated.

9. A vacuum deposition system comprising: a vacuum chamber; a deposition material source mounted in the vacuum chamber; a substrate holder in the vacuum chamber; support means in the vacuum chamber for supporting the substrate holder; and a mechanism in said vacuum chamber for suspending and rotating the substrate holder, said mechanism having; a rotatable housing; retraction means rotatable with said rotatable housing; and releasable latch means engageable by rotation of said retraction means for coupling the substrate holder to said retraction means; said retraction means being responsive to the inertia of the article to be suspended when the rotatable housing is rotated so as to suspend the article prior to its being rotated, then rotate together with said rotatable housing so that said mechanism and substrate holder rotate together.

10. A system as in claim 5 wherein said releasable latch means comprises a latch member and an engaging member; and rotation of said retraction means brings the latch and engaging members into engagement.

11. An article rotation mechanism comprising: rotating means; and retraction means having a first member rotatable by said rotating means and a second member threaded within said first member and adapted for engagement with an article having a velocity different from that of said rotating means.

12. A mechanism as set forth in claim 11 wherein said first member is a nut and said second member is a screw adapted to cooperatively engage said nut.

13. A mechanism as set forth in claim 12 wherein said nut is adapted to slide along the axis of said rotating means.

14. A mechanism as set forth in claim 11 wherein said article is a stationary article.