JP2840198B2 - Quartz glass jig for heat treatment of semiconductor device and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a jig for heat treatment of a semiconductor element used for manufacturing a semiconductor element, and more particularly to a quartz glass jig for heat treatment of a semiconductor element used in a heat treatment step of a silicon wafer and a method of manufacturing the same.

[0002]

2. Description of the Related Art Quartz glass has been used as a jig for heat treatment of silicon semiconductor devices because it has higher purity than other refractory materials and can be fused by welding. However, with the recent increase in the degree of integration of semiconductor devices and the emergence of devices that extremely dislike impurities, such as flash memories, higher purity is required, and in order to satisfy this requirement, high-purity natural quartz powder and synthetic quartz glass powder are used. It has been developed. In particular, in the synthetic quartz glass powder, the total amount of metal impurities is 0.1%.
Synthetic silica glass with a remarkably high purity not exceeding 1 ppm has been industrially manufactured.

A conventional quartz glass jig for heat-treating a semiconductor element uses the above high-purity raw material, for example, British Patent No. 40
No. 0,472, etc., a circular nozzle is extruded into a round bar, which is fixed on a steel platen 13 with wax 14 as shown in FIG. 5, and a rotating diamond blade 15 is used to precisely cut the wafer mounting portion. In addition, it is formed on a silicon wafer mounting member, and is integrally assembled by welding a support member formed of a round bar and an oxyhydrogen flame as a heat source.
Since such machining can perform precision machining, it has become possible to automatically load a silicon wafer and transfer a jig to a heat treatment furnace.

However, since quartz glass is a brittle material, micro cracks are formed on the cut surface during machining.
Sometimes it occurs to a depth of 100 μm or more, and impurities such as sodium, potassium, lithium, calcium, copper, iron, nickel etc. generated from machine tools and coolant liquid are taken in there, There is a problem that the wafer is contaminated during the heat treatment. Cleaning can be performed by etching off a surface layer of 100 μm or more of the member, but dimensional accuracy is sacrificed.
In some cases, it may be difficult to find a compromise between dimensional accuracy and surface purity. In particular, when processing with a dimensional accuracy of ± 5/100 (mm) necessary for automatic mounting of a silicon wafer, it was not easy to satisfy the dimensional accuracy by avoiding the generation of microcracks and the incorporation of impurities.

[0005]

In view of the current situation,
As a result of extensive studies, the present inventors have obtained a quartz glass jig for heat treatment of a semiconductor device without the above-mentioned defects by forming a silicon wafer mounting portion of the quartz glass jig for heat treatment of a silicon semiconductor device by laser processing. The present invention has been completed, and the present invention has been completed. Ie

SUMMARY OF THE INVENTION An object of the present invention is to provide a quartz glass jig for heat-treating a semiconductor device having industrially advantageous dimensional accuracy and surface cleanliness. Another object of the present invention is to provide a method for manufacturing the above quartz glass jig for heat treatment of a semiconductor element.

[0007]

According to the present invention, there is provided a quartz glass jig for heat-treating a silicon wafer, comprising a silicon wafer mounting member and a supporting member for supporting the silicon wafer mounting member. The present invention relates to a quartz glass jig for heat-treating a semiconductor device, wherein the member for use is a quartz glass plate having a wafer mounting portion formed by laser processing, and a method of manufacturing the same.

The above quartz glass treatment for heat treatment of silicon wafers
As shown in FIG.
A supporting member 7 for supporting the member,
The wafer mounting member 5 is provided with grooves and claws serving as a wafer mounting portion.
Have been killed. A silicon wafer is placed on this jig and
Transfer into furnace and heat to high temperature around 1000 ℃ to form oxide film
And so on .

[0009] In the above processing, if an alkali element such as sodium or potassium, or an impurity element such as iron element, nickel element or calcium element is present in the quartz glass surface layer, these are released and the silicon wafer is contaminated. Therefore, the content of sodium element is 0.4 ppm or less, the content of potassium element is 0.2 ppm or less, the content of iron element is 0.4 ppm or less, and the content of calcium element is 0.1 ppm or less from the surface layer of the quartz glass forming the jig to at least 30 μm. 8pp
m or less. Therefore, in the present invention, the raw materials having the above-mentioned purity are used, and the material of each member is manufactured by an extrusion molding method. It is not preferable to increase the thickness of the plate material and adjust the thickness later by grinding or the like, or to cut out the plate material from a large block because microcracks are formed on the surface. Machining is also not preferred in terms of attaching metal powder, which is a coolant for the diamond tool, to the glass surface. It is good to extrude to the required thickness from the beginning. Here, the term “extrusion molding” does not simply mean a method in which a melt is pressed and extruded from an opening. A method of pulling out the plate-like material that comes out with a feed roller or a method of lowering it at a constant speed with a `` feed roller '' that generates a torque that sends it upward to prevent the plate-like material from falling by gravity Including. Further, there may be various variations such as a method of pulling the plate material upward and a method of pulling the plate material in a lateral direction, and any method may be used as long as the plate is directly formed and does not require cutting or grinding later.

The silicon wafer mounting member 5 is made of a quartz glass plate because the laser processing is difficult if the thickness is not uniform. By using a quartz glass plate, processing with high dimensional accuracy can be performed by a laser processing method as shown in FIG. 1, and automatic insertion of a wafer and automatic loading of a jig can be performed.
As a method for manufacturing a quartz glass plate, see Japanese Patent Application Laid-Open No. 4-5533.
The production method described in Japanese Patent Publication No. 2 and the method described in International Publication No. 94/3404 can be employed. A method appropriate for the design of the jig and the number of jigs to be manufactured may be adopted. It is preferable in terms of work efficiency that the support member for supporting the silicon wafer mounting member is made of a round bar. These parts are welded to assemble a jig such as a silicon wafer boat shown in FIG. In FIG. 2, 5 is a silicon wafer mounting member, 7 is a support member,
8 is a wafer insertion groove. The laser processing method shown in FIG. 1 is most suitable for the processing of the grooves. The quartz glass plate 2 is placed on the laser transfer table 3 and the wafer insertion groove 8 is cut out by the carbon dioxide laser 1. The argon assist gas 4 is blown so that fumes do not remain in the wafer insertion grooves 8 during the processing.
The output of the laser for processing selects the power which makes the cut surface smooth. If the positioning control of the processing is performed in units of μm, it is possible to perform cutting with an accuracy of ± 0.05 mm. Even if the argon assist gas 7 is sprayed, fumes remain in the vicinity of the contact cross section to such an extent that the fumes become slightly cloudy, so that they are immersed in dilute hydrofluoric acid and removed. By employing the laser processing method, cracks do not occur in the jig and the surface becomes smooth. It is not easy to cut a groove in a round bar by laser processing because the thickness varies from place to place. Although the thickness of the extruded plate may vary by about ± 0.3 mm, the thickness of the extruded plate is not so large as to make the laser processing non-uniform, so that the extruded plate can be suitably used in the present invention.

The above laser processing is sufficient in a range within 2 cm from the point of contact with the silicon wafer. If the area exceeds 2 cm from the contact point of the silicon wafer, the silicon wafer is not contaminated even if it is cut by diamond processing.

An example of the manufacturing method of the present invention will be described with reference to the drawings. A high-purity quartz powder 12 is supplied to the electric furnace 9 shown in FIGS. 3 and 4, and after being heated and melted, extruded from a nozzle 10 to produce a quartz glass rod 11 and a quartz glass plate 2. The quartz glass plate material 2 is set on the laser beam machine shown in FIG. 1, a silicon wafer insertion groove 8 is formed, and the supporting member 7 manufactured from the quartz glass round bar 11 is welded by electric welding to form a silicon wafer shown in FIG. Assemble the boat.

The above-described manufacturing method is an example of a boat for a horizontal furnace, but a boat for a vertical furnace can be similarly prepared by providing wafer insertion grooves or claws in a plate material.

[0014]

[Example] After the raw material quartz powder was subjected to flotation and magnetic separation, it was washed with hydrofluoric acid and nitric acid, purified at 1100 ° C with a mixed gas of chlorine and hydrogen chloride, and had an iron element content of 0.05 pp.
m or less, sodium element content 0.05 ppm or less,
Crystal powder having a potassium element content of 0.05 ppm or less and a calcium element content of 0.5 ppm or less was obtained. The raw material was heated at 2200 ° C. in an electric furnace 9 having a crucible made of molybdenum.
3 mm, a round bar 11 having a diameter of 15 mm, a thickness of 4 mm, and a width of 3 mm.
A 5 cm plate 2 was produced.

The above-mentioned plate material is processed into a wafer insertion groove 8 by a laser processing method shown in FIG.
The silicon wafer boat was assembled by welding as shown in FIG. The silicon wafer boat was treated with 4.5% hydrofluoric acid for 3 hours.
Minutes to remove fumes and surface contamination. The wafer insertion groove 8 of the obtained jig had a smooth surface. The jig was etched with hydrofluoric acid to a depth of 30 μm from the surface layer to measure the average purity of the entire surface layer. as a result,
Iron element content is 0.05ppm or less, sodium element content is 0.05ppm or less, potassium element content is 0.05ppm or less, calcium element content is 0.5p
pm or less, the purity of the raw material was maintained. When the wafer was oxidized using the wafer boat, all the wafers had a uniform and high-quality oxide film.

Comparative Example 1 As shown in FIG.
A wafer boat was prepared by a conventional method of cutting at 5 and washed in the same manner as in the example, and the purity at a depth of 30 μm from the surface was analyzed. As a result, the iron element content was 0.55 ppm, the sodium element content was 0.50 ppm, and the potassium element content was 0.1 ppm.
Contamination remained at 35 ppm and calcium element content of 1.2 ppm. When this wafer boat was used for the oxidation treatment, a wafer having a high-quality oxide film was obtained only after so-called high-temperature gas purification in which the wafer boat was exposed to hydrogen chloride gas at 1000 ° C. for 20 hours.

Comparative Example 2 A wafer boat manufactured in the same manner as in Comparative Example 1 was subjected to etching treatment with hydrofluoric acid while monitoring the purity of the surface by analyzing the etching solution until the surface became clean. The surface was cleaned by the second etching process, but the groove width was widened by about 0.1 mm or more, and the shape of the groove was disturbed, so that it could not be used as a wafer boat for automatic loading.

Comparative Example 3 (Experiment) A wafer boat was prepared in the same manner as in the embodiment except that only one end of the wafer mounting groove was cut out with a diamond cutter, and a wafer was loaded and an oxide film was formed. Was carried out. As a result, the wafer within 2 cm from the first groove had a too large film thickness, resulting in a defective product.

[0019]

The quartz glass jig for heat treatment of a silicon semiconductor device of the present invention has no micro-racks on its wafer mounting member, and contamination by impurity elements can be caused even in the heat treatment of a silicon semiconductor device using the jig. And good processing was possible. Moreover, the method for manufacturing a jig for heat treatment of a semiconductor element of the present invention is an industrially advantageous manufacturing method because it is a simple method of using an extruded member and laser processing it.

[Brief description of the drawings]

FIG. 1 is a schematic perspective view of a laser processing apparatus for producing a wafer mounting member of the present invention.

FIG. 2 is a perspective view of a quartz glass jig for horizontal heat treatment of the present invention.

FIG. 3 is a schematic sectional view of an apparatus for manufacturing a round bar material forming a jig of the present invention.

FIG. 4 is a schematic sectional view of an apparatus for manufacturing a plate material forming the jig of the present invention.

FIG. 5 is a schematic view of a conventional apparatus for manufacturing a quartz glass jig for heat treatment of a semiconductor element.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Carbon dioxide laser 2 Quartz glass plate material 3 Laser transfer table 4 Argon gas assist gas 5 Silicon wafer mounting member 6 Silicon wafer 7 Support member 8 Silicon wafer insertion groove 9 Electric furnace 10 Nozzle 11 Quartz glass round bar 12 Raw material powder 13 Iron Surface plate 14 Fixed wax 15 Diamond blade 16 Coolant

──────────────────────────────────────────────────続 き Continuation of the front page (51) Int.Cl. ⁶ identification code FI H01L 21/324 H01L 21/324 Q (58) Investigated field (Int.Cl. ⁶ , DB name) H01L 21/31 C03B 20 / 00 C03C 3/06 H01L 21/22 511 H01L 21/324

Claims (4)

(57) [Claims] 1. A member for mounting a silicon wafer and supporting the member.
Quartz wafer for heat treatment of silicon wafer, comprising
In the glass jig, the silicon wafer mounting member is
Laser processing within 2cm from the contact point of Eha
Quartz glass plate material with a silicon wafer mounting part
A quartz glass jig for heat treatment of a semiconductor element, characterized by comprising: 2. The quartz glass sheet has a thickness at least from the surface layer.
Up to 30 μm, the iron element content is 0.4 ppm or less,
Thorium element content is 0.4 ppm or less, potassium element
Content is 0.2ppm or less, calcium element content is
An average purity of 0.8 ppm or less
Item 4. A quartz glass jig for heat treatment of a semiconductor element according to Item 1 . 3. The laser is within 2 cm from the contact point of the wafer.
Quartz gas with silicon wafer mounting part formed by processing
The lath plate and the support member are welded together.
Of manufacturing a quartz glass jig for heat treatment of a semiconductor device . 4. A sodium element content of 0.4 ppm or less.
Below, potassium element content is 0.2 ppm or less, iron element
The content is 0.4 ppm or less, and the calcium element content is 0.4 ppm.
Extrusion molding by melting 8ppm or less of silicon dioxide in a crucible
Forming a quartz glass plate material by performing
3. Manufacturing method of quartz glass jig for heat treatment of semiconductor element described in 3.
Law .