JPS62241894A - Wafer holder - Google Patents

Abstract

PURPOSE:When a thin film of single crystal is allowed to grow on a wafer by the molecular ray epitaxy method, the wafer holder is constituted from heating part, a uniformly heating material which is fixed through an adhesive layer to the heating part and a ring for holding the wafer to ensure the fixation of the wafer to the holder. CONSTITUTION:When a thin film of single crystal of compound semiconductor such as GaAs or the like is allowed to grow on a wafer as a base plate by the molecular ray epitaxy method, the wafer holder is constituted from a heater 1 which is made of a material of high thermal conductivity and heat resistance such as Mo or the like, a uniformly heating material 5 made of elements of groups V and VI of the periodic table such as Ga or As which is welded to the heater with In adhesive layer 3 and a ring press 9 which is made of BN, Si3N4, SiO2 and the wafer is held between the uniformly heating material 5 and the ring 9. The ring 9 is fixed by setting several male screws on its periphery to the female screws on the circular depression to hold the wafer with its projection on the ring edge without contamination of the wafer with the adhesive of In.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a wafer holder, and more particularly to a wafer fixing device for growing a single crystal thin film on a wafer by molecular beam epitaxy.

BACKGROUND OF THE INVENTION Conventional Technology High-speed integrated circuits are becoming increasingly miniaturized and have higher degrees of integration. Under these circumstances, there is a demand for higher performance, higher speed devices. For example, there is a need to develop ultrahigh speed devices using multilayer heterostructure crystals made of different 1ff-V group compound semiconductors with high electron mobility. -Currently being actively carried out.

To fabricate the above-mentioned ultra-high-speed devices, highly accurate control over film thickness, composition ratio, impurity doping, etc. is required in the thin film growth of I[[-V group compound semiconductors, and the most effective method for this is molecular beam growth. Epitaxy method is attracting attention.

Furthermore, when the dimensions of the device become smaller than the average electron density of electrons in the solid, 1 + f: 1i (of the order of 1 (15)), a previously unobserved effect, namely a quantum effect, appears, creating a completely new Create a device based on physical phenomena and complete 11 tests.

Molecular beam epitaxy is a method that can create such extremely thin layers periodically and uniformly, and is the only method that can realize, for example, superlattice devices that apply the quantum effect of multilayer films with good reproducibility. It is no exaggeration to say that it is.

As mentioned above, molecular beam epitaxy is a method that not only allows the required devices to be fabricated with high precision, but also enables the development of new devices. This has great significance for the semiconductor industry.

Molecular beam epitaxy is a type of vacuum deposition method. That is, in an ultra-high vacuum, the constituent elements on each side of the crystal are placed in separate evaporation crucibles, the crucible is heated to evaporate the constituent elements, and the evaporated vapor is irradiated in the form of molecular beams onto the heated substrate. In this method, a single crystal film is grown on the substrate.

Taking the crystal growth of a thin film on Ga8 as an example, as shown in the attached Figure 4, there is a
An rL crystal substrate 13, a crucible 15 containing a and a crucible 17 containing an 8s are placed at the bottom thereof, respectively. After evacuating the inside of the vacuum bell 11, the crucible 15.17 is heated, and Ga and 8S are evaporated toward the heated substrate 13.

If the molecular beam of As is made sufficiently strong compared to Ga, first 6
A is attached to the substrate 13, and then the same number of 8s as the attached Ga is bonded to Ga and attached to the substrate 13. Further, the excess ΔS is separated from the substrate and carried away through the exhaust pipe 19 to the pump system.

In this way, a Ga8 compound semiconductor single crystal film is formed on the substrate, but as mentioned above, the molecular beam epitaxy method uses vapor from sublimation from a solid phase or evaporation from a liquid phase as a molecular beam. It is.

However, these evaporated raw materials cannot be held in the crucible against gravity. Therefore, the placement of the crucible is subject to significant restrictions. If there are restrictions on the placement of the crucible, the substrate will inevitably be restricted in its position. For example, in the vertical type, which was used from the earliest times due to the relative relationship between the molecular beam emitted from the crucible and the substrate, the substrate surface should face downward. It is held and fixed. Furthermore, in the horizontal type, tilted type, etc., the substrate is supported right sideways or diagonally downward.

In addition, in order to grow a high-quality single-crystal film with uniform thickness, it is necessary to orient the substrate in the optimal position relative to the molecular beam.
and it is necessary to perform in-plane rotation of the substrate. Therefore, recently, manipulators that can precisely position and in-plane rotate the attached substrate have come into use.

However, if the substrate is not reliably held and fixed by the manipulator, it is impossible to accurately position or rotate the substrate even if the manipulator has high operating accuracy.

Conventionally, the wafer, which is the substrate, has been fixed by brazing the wafer to a wafer holder (often a molybdenum plate) with In (indium) and mounting the wafer holder on a manipulator. Although In was in a liquid state at the single crystal film growth temperature, the wafer and wafer holder were bonded together by surface tension.

Problems to be Solved by the Invention As mentioned above, wafers have traditionally been fixed using In, but this is not necessarily the best method;
This is because no other suitable method has been developed. For example, the conventional fixing method using In has the following problems.

That is, when the wafer is fixed and detached, since In is in a molten state, droplets of molten In may adhere to the substrate surface. As a result, there was a problem in that the quality of the grown single crystal film was extremely degraded.

In addition, after film formation, the substrate is subjected to various processing, which requires great effort to remove In remaining on the back surface of the substrate.

Furthermore, the substrate is fixed by the surface tension of the molten In during single crystal film growth as described above. However, there was a drawback that the fixation was not performed reliably and the substrate often peeled off from the wafer holder during single crystal film growth.

Additionally, during single crystal film growth, volatile elements escape from the backside of the wafer, causing problems such as roughening of the backside of the wafer and changes in the wafer composition ratio, but no countermeasures have been taken in the past. There wasn't.

An object of the present invention is to solve the above-mentioned problems in the prior art as explained above. That is, the object of the present invention is to develop a wafer holder that can reliably hold and fix a substrate without leakage of volatile elements from the substrate or contamination by 1n.

Means for Solving the Problems In order to solve the above-mentioned problems of the prior art, the inventor of the present invention has made various studies and has discovered that it is possible to hold and fix wafers such as single crystal substrates without directly brazing them with molten In. The present invention was completed based on the finding that it is very advantageous in achieving the above object of the present invention.

That is, the present invention provides a wafer holder used in molecular beam epitaxy, which includes a heating member, a heating member fixed to the upper surface of the wafer via an adhesive layer and in contact with the wafer, and a heating member fixed to the upper surface of the wafer holder in contact with the wafer; The wafer is characterized by having a supporting protrusion and comprising an annular member that supports and fixes the wafer together with the heating member.゛The material for the heating member is preferably a material that has good thermal conductivity and one level of heat resistance, such as molybdenum.

Further, as the adhesive layer, 10 can be cited as a preferable example.

Furthermore, preferable examples of the material for the annular member include nitrided glass, silicon nitride, and silicon oxide.

Furthermore, the fixing of the wafer by the annular member and the heating member is such that the annular member is reliably fixed to the heating member, and
The wafer support portion of the annular member may be finely adjusted so as to be able to support the wafer without destroying it, and the following various methods can be cited as preferred examples.

That is, an annular convex portion having an inner diameter larger than the diameter of the wafer is provided on the upper peripheral edge of the heating member, and a female thread is provided on the inner circumferential wall of the annular protrusion, and a male thread is provided on the outer circumferential wall of the annular member.
By screwing the annular member into the annular projection, the wafer can be pressed and supported by the support protrusion.

Further, the same effect can be obtained by providing a male thread on the outer circumferential wall of the annular protrusion and a male thread on the inner circumferential wall of the annular member, and screwing the annular protrusion into the annular member.

Furthermore, either an annular member having an inner diameter slightly larger than the outer diameter of the annular protrusion or an annular member having an outer diameter slightly smaller than the inner diameter of the annular protrusion is fitted into the annular protrusion, and both of these are fitted. It is also possible to screw it along its axial direction.

Alternatively, the heating member may be in the shape of a disk, a male thread may be provided on the outer circumferential portion of the heating member, and a female thread may be provided on the inner circumferential wall of the annular member, and the heating member may be screwed into the annular member, or the heating member may be screwed into the annular member. An annular member with a large inner diameter,
The purpose can also be achieved by fitting the heating members and screwing them together along the axial direction.

The wafer supporting protrusion may be in any shape as long as it can contact the wafer in a line or plane, can press and support the wafer without destroying it, and can form a closed space between the wafer, the heating member, and the annular member. For example, a preferable example is an annular protrusion provided at one end of the annular member and having an inner diameter slightly smaller than the diameter of the wafer.

In addition, in order to clarify the installation position of the heat equalizing member and to make the work of holding and fixing the wafer easier and more accurate, a central recess with a diameter slightly larger than the diameter of the heat equalizing member is provided in the center of the heating member. Is possible.

Furthermore, another major feature of the present invention is prevention of volatile elements from being removed from the substrate. That is, the above wafer is
In the case of a -■ group or TI-VI group compound semiconductor single crystal, the escape of group V or group II elements can be prevented by making the heat-uniforming member contain an element of group II or group II.

In order to prevent volatile elements from leaking out from the wafer, it is preferable that the heat equalizing member has an uneven upper surface.

As the above-mentioned heat-uniforming member, it is preferable to use a group (Ⅰ) or VI group element itself, a +n-v group or [■] group compound semiconductor itself, a surface coated with any of these, or a porous material containing these. This can be cited as an example.

As a specific example, when growing a single crystal film on a GaAs single crystal substrate, Δs, a GaAs soaking member, or 8s.

A heat absorbing part coated with GaAs or the like can be suitably used.

In order to solve the problems of the prior art, to obtain a wafer holder that can securely fix a single crystal substrate and prevent contamination by (7) In, it is preferable to configure the wafer holder as described above.

That is, in conventional wafer holders, the wafer is brazed directly to the heating member using In, so that contamination of the wafer by 10, for example, when the wafer is attached or detached, In droplets may adhere to the wafer surface or the wafer may be There was a problem in that In remained on the wafer surface after the wafer was removed.

In the wafer holder according to the present invention, the wafer is placed on a heat equalizing member fixed to the heating member via an adhesive layer such as In, and is further pressed and supported from above by the wafer supporting protrusion of the annular member.

Therefore, the wafer does not directly contact the adhesive layer, e.g.
In is not attached to the front or back surface of the wafer.

Furthermore, conventionally, during film formation, the wafer is connected to the heating member by a surface tension of 1n, so that detachment of the wafer during film formation has been a problem. However, in the wafer holder of the present invention, since the wafer is firmly and delicately pressed and supported by the annular support portion, the wafer does not separate from the holder during single crystal film growth.

In the wafer holder of the present invention, a heat equalizing member is placed between the wafer and the heating member. Since this heat equalizing member is fixed to the heating member by the metal, a sufficient contact area with the heat equalizing member is obtained, so that a uniform temperature distribution is obtained. Further, the surface of the heat equalizing member is provided with irregularities, and the substrate is fixed thereon by the wafer fixing protrusion of the annular member.

Since the wafer is uniformly heated by heat conduction and heat radiation from the heat equalizing member, a uniform temperature distribution within the substrate surface is achieved.

Furthermore, conventionally, no measures have been taken to prevent the escape of volatile elements during film formation. In the present invention, in the closed space formed by the annular member, the wafer, and the heating member, there is a heat equalizing member containing volatile elements in the substrate composition, so that volatile elements are prevented from escaping from the wafer. be able to.

Since the temperature of the soaking member is higher than that of the single crystal substrate, sufficient volatile element vapor can be provided. Further, the heat equalizing member has irregularities on its upper surface, thereby increasing the contact surface between the back surface of the wafer and the vapor of the volatile element, thereby enhancing the effect of preventing the volatile element from escaping.

Taking these into consideration, it is desirable that the annular member be made of a material that is highly heat insulating and capable of achieving appropriate airtightness at the interface with the wafer or heating member.

The wafer holder having the above structure has a heating member fixed to a manipulator, is held in a vacuum chamber with the wafer surface facing in a predetermined direction, that is, downward, right sideways, or diagonally downward, and is subjected to internal rotation during film formation. If the heating member is securely fixed to the manipulator with screws, etc., the heating member,
Wafers and the like do not come off or shift during film formation.

EXAMPLES The wafer holder according to the present invention will be explained in more detail by way of examples. However, the scope of the present invention is not limited to this example.

Example 1 A first example of the present invention will be described with reference to the attached FIG. 1. As shown in the figure, the wafer holder of this embodiment has a heating member 1 made of molybdenum and an In adhesive layer 3 which is used to braze a Ga 8 heat equalizing member 5, and a Ga 8 heat equalizing member 5 on an IjJ heat equalizing member 5 being brazed onto the molybdenum heating member 1. The structure is such that the wafer 7 is pressed and supported by the annular member 9.

The upper surface of the heat equalizing member 5 is provided with unevenness, and is further brazed to the heating member 1 by a 1N adhesive layer 3, so that the upper wafer 7 is heated by its radiant heat and conductive heat. Can be heated evenly.

Further, in the closed space constituted by the heating member 1, the wafer 7, and the annular member 9, the vapor of 8S volatilized from the heat equalizing member 5 exists, and the 8S vapor is prevented from slipping out from the wafer 7.

Further, the annular member 9 presses and supports the substrate 7 by a male thread on the outer periphery and a female thread on the inner periphery of the annular convex portion of the heating member 1, so that the substrate 7 is held securely without being damaged. can do.

The annular member 9 has a male thread on its outer periphery, and is screwed into a mochi screw on the inner periphery of an annular convex portion that protrudes upward at the periphery of the heating member l, and the supporting protrusion allows the wafer 5 to be Hold and fix.

Example 2 Example 2 has a male thread on the outer periphery of the annular convex portion projecting upward on the circumference of the upper surface of the heating member I, and a female thread on the inner periphery of the annular member 9. The structure is similar to Example 1.

The soaking plate 5 is brazed to the heating material 1 by an adhesive layer 3 of In, and the wafer 7 placed thereon is held and fixed by screwing the heating material 1 into the annular member 9. Ru.

Example 3 Example 3 has the same structure as Example 2, except that the heating member 1 is disc-shaped and has a central recess for positioning.

The soaking plate 5 is brazed onto the central recess of the heating member 1 by an In adhesive layer 3, and the wafer placed thereon is held and fixed by screwing the heating member 1 into the annular member 9. .

In both Example 2 and Example 3, the same effects as in Example 1 can be expected.

Effects of the Invention Thus, the present invention provides a wafer holder that can reliably hold and fix a wafer and prevent it from being contaminated by In.

That is, since the substrate does not come into direct contact with the melted material, there is no contamination on the surface of the substrate. In addition, when attaching and detaching the board, it can be done reliably and without the need for a high level of skill.
Moreover, damage to the board can be reduced.

Also, for example, by making the back side of the GaAs substrate a closed space and further inserting a heat equalizing member made of GaAs into the space, it is possible to prevent ^S from coming off the substrate.

[Brief explanation of drawings]

The attached FIGS. 1, 2, and 3 are cross-sectional views showing examples of the present invention, and the attached FIG. 4 is a schematic diagram for explaining the molecular beam epitaxy method. (Main reference numbers) 1...Heating member, 3...In adhesive layer, 5...G
aAs heat equalizing member, 7...GaAs substrate, 9...annular member, 11...vacuum bell, 13...substrate,
15.17... Crucible, patent applicant Sumitomo Electric Industries Co., Ltd. Agent Masahiko Arai Figure 1 1... Heating member 3... Sister-in-law 1 eyebrow 5...
... Soaking member 7 ... Wafer 9 ...
・Ring 4 Taibe Sue 11...Vacuum bell 13...Platform board, 15...Ruppo 17...Ruppo 19...Exhaust pipe

Claims (16)

[Claims] (1) A wafer holder used in molecular beam epitaxy, which includes a heating member, a heating member fixed to its upper surface via an adhesive layer and in contact with the wafer, and a protrusion at one end for supporting the wafer. The wafer holder includes a ring-shaped member that supports and fixes the wafer together with the heating member. (2) The wafer holder according to claim 4, wherein the adhesive layer is made of indium. (3) The wafer holder according to claim 1 or 2, wherein the heating member has an annular convex portion having an inner diameter larger than the diameter of the wafer at the upper peripheral portion. (4) The annular protrusion of the heating member has a female thread on the inner circumferential wall, and the annular member has a male thread on the outer circumferential wall, and the annular member is screwed into the annular protrusion, and the supporting protrusion The wafer holder according to claim 3, wherein the wafer is supported by pressure. (5) The annular protrusion has a male thread on its outer circumferential wall, and the annular member has a female thread on its inner circumferential wall, and the annular protrusion is screwed into the annular member, and the supporting protrusion allows the wafer to be Claim 3, characterized in that the
Wafer holder described in section. (6) The annular member has a large-diameter portion with an inner diameter slightly larger than the outer diameter of the annular convex portion of the heating member, and when the annular portion is fitted into the large-diameter portion, both of them are connected. The wafer holder according to claim 3, wherein the wafer holder is screwed along the axial direction and the wafer is supported by the supporting protrusion. (7) The annular member has a small diameter portion having an outer diameter slightly smaller than the inner diameter of the annular convex portion of the heating member, and when the small diameter portion is fitted into the annular portion, both of them are connected to the axis thereof. 4. The wafer holder according to claim 3, wherein the wafer holder is screwed along the direction and the wafer is supported by the supporting protrusion. (8) The wafer holder according to claim 1 or 2, wherein the heating member is disc-shaped. (9) The heating member has a male thread on its outer circumferential portion, and the annular member has a female thread on its inner circumferential wall, and the heating member is screwed into the annular member, and the supporting protrusion presses the wafer. Claim 8 characterized in that it supports
Wafer holder described in section. (10) The annular member has a large-diameter portion with an inner diameter slightly larger than the diameter of the heating member, and when the heating member is fitted into the large-diameter portion, both of them are connected along the axial direction. 9. The wafer holder according to claim 8, wherein the wafer is fixed with a screw, and the wafer is supported by the supporting protrusion. (11) The wafer supporting protrusion is located at one of the annular members.
The wafer holder according to any one of claims 1 to 10, characterized in that the wafer holder is an annular projecting portion provided at an end and having an inner diameter slightly smaller than the diameter of the wafer. (12) According to any one of claims 1 to 11, wherein the heating member has a central recess in the center having a diameter slightly larger than the diameter of the heat equalizing member. Wafer holder as described. (13) The wafer holder according to any one of claims 1 to 12, wherein the heat equalizing member has irregularities on its upper plane in contact with the wafer. (14) The wafer according to claim 13, wherein the wafer is a III-V group or II-VI group compound, and the heating member contains a corresponding group V or VI element. holder. (15) The wafer holder according to claim 14, wherein the heat equalizing member is a porous material containing a group V or group VI element. (16) The above-mentioned heat equalizing member is a group V element, a group VI element, a III-
15. The wafer holder according to claim 14, wherein the wafer holder is coated with one selected from the group consisting of Group V compounds and Group II-VI compounds.