JP3994390B2 - Alkaline solution for semiconductor wafer processing and its manufacturing method - Google Patents

Description

【００１８】
表１から明らかなように、ボロンまたはボロンを含むシリコンを溶解させた試験例１〜７は、これらが含まれない比較例１に比べて、ニッケルの汚染量が低いことが分かった。
【００１９】
【発明の効果】
この発明によれば、アルカリ溶液中にボロンを溶解したので、低コストで、アルカリ溶液中に溶解した金属不純物による半導体ウェーハの汚染を、効果的に防止することができる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a semiconductor wafer alkali treatment technique, and more particularly to a semiconductor wafer alkali treatment technique for preventing contamination of a semiconductor wafer by metal impurities dissolved in the alkali solution when the semiconductor wafer is treated using an alkali solution.
[0002]
[Prior art]
In conventional silicon wafer manufacturing, a silicon wafer is manufactured by slicing an ingot, and then the silicon wafer is sequentially subjected to chamfering, lapping, acid etching, mirror polishing, and finish cleaning.
Among these, in the acid etching process, the lapped silicon wafer is immersed in an acidic etching solution such as mixed acid (hydrofluoric acid, nitric acid, acetic acid) to remove the processing damage at the time of lapping and the processing damage at the time of chamfering. Acid etching has the advantage of high reactivity with a silicon wafer and a relatively high etching rate, while a large amount of bubbles are generated during the etching. Waves of about 20 mm and heights of several tens to several hundreds of nanometers occurred, and the flatness of the wafer surface was reduced.
[0003]
In order to solve this problem, alkali etching using a high-concentration alkaline etching solution has been adopted in recent years in place of the acidic etching solution.
However, nickel, chromium, iron, copper and the like are easily dissolved in the alkaline etching solution. Therefore, at the time of etching, metal impurities dissolved in the alkaline etching solution are adsorbed on the exposed surface of the silicon wafer, and the metal impurities diffuse to the inside of the wafer to deteriorate the quality of the wafer.
[0004]
Conventionally, as a method for solving this problem, for example, the one disclosed in Patent Document 1 is known. In the conventional method, metal ions are deionized by dissolving a reducing agent (such as dithionite) that has a base oxidation potential lower than the reversible potential of the metal ions present in the alkaline etching solution. It is a method to do. Thereby, metal impurities in the alkaline etching solution are removed, and deterioration of the quality of the silicon wafer due to metal impurities during etching is prevented.
[Patent Document 1]
Japanese Patent Laid-Open No. 10-310883
[Problems to be solved by the invention]
However, even when such a conventional method is adopted, in recent years, it has not been possible to sufficiently meet the demand for high cleanliness for wafers from device manufacturers due to high integration of devices. That is, it has been difficult to say that the conventional method effectively prevents the diffusion of metal impurities such as nickel into the wafer.
[0006]
OBJECT OF THE INVENTION
SUMMARY OF THE INVENTION An object of the present invention is to provide a semiconductor wafer alkali treatment technique that can effectively prevent contamination of a semiconductor wafer by metal impurities dissolved in an alkaline solution at low cost.
[0007]
[Means for Solving the Problems]
According to the first aspect of the present invention, in an alkaline solution for semiconductor wafer processing used for alkali treatment of a semiconductor wafer, boron is added to 500 to 2000 ppb, silicon in a sodium hydroxide solution having a concentration of 20 wt% or more Is an alkaline solution for processing semiconductor wafers containing 0.25 g / liter or more.
Examples of the alkali treatment of the semiconductor wafer include etching with an alkaline etching solution and etching with a mixed acid of an alkaline etching solution and an acidic etching solution. In addition, cleaning with a cleaning solution containing an alkaline etching solution can be given.
[0008]
Examples of the impurity metal that can suppress adsorption to the semiconductor wafer by adding boron include nickel, copper, chromium, and iron. Among these, removal of nickel having a high diffusion rate in the silicon crystal is most important for improving the quality of the silicon wafer.
[0009]
If it is less than 0.25 g / liter, adsorption and diffusion of impurity metals on the semiconductor wafer cannot be suppressed. A preferable silicon content is 1 to 80 g / liter.
[0010]
When the concentration of the sodium hydroxide solution is less than 20% by weight, the roughness of the front and back surfaces of the silicon wafer increases. A preferred concentration of the sodium hydroxide solution is 43% by weight or more.
[0011]
The invention according to claim 2 is the alkaline solution for semiconductor wafer processing according to claim 1, wherein the silicon content is 1 to 80 g / liter.
[0012]
The invention according to claim 3 is used when a semiconductor wafer is alkali-treated by containing boron in a concentration of 20% by weight or more in a sodium hydroxide solution of 500 to 2000 ppb and silicon of 0.25 g / liter or more. This is a method for producing an alkaline solution for semiconductor wafer processing, in which a silicon material doped with boron at a predetermined concentration is dissolved in the sodium hydroxide solution.
The silicon material may be, for example, a silicon wafer doped with a predetermined amount of boron, or a piece of silicon ingot serving as the base material.
[0013]
If it is less than 20% by weight, the roughness of the front and back surfaces of the semiconductor wafer when etched using the solution increases, and therefore a separate concentration treatment is required.
[0014]
[Action]
According to the present invention, when an alkali solution in which boron is dissolved is used and a semiconductor wafer is processed (for example, etching), contamination of the semiconductor wafer by metal impurities dissolved in the alkali solution is low-cost and effective. To be prevented.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the present invention will be described below with reference to Table 1.
A predetermined amount of p-type silicon wafer doped with boron (Test Examples 1 to 7) was dissolved in a commercially available high-concentration sodium hydroxide solution (51 wt%, 5 liters, 80 ° C.). Then, this sodium hydroxide solution was used as an alkaline etching solution, and the p-type silicon wafer (resistivity 0.01 to 0.02 Ωcm) with a surface orientation (100) that was pulled up and processed by the CZ method was subjected to alkaline etching for 10 minutes. Alkaline etching was performed while stirring the liquid. After etching, the silicon wafer was rinsed in running water for 5 minutes.
[0016]
After rinsing, the amount of nickel contamination of the silicon wafer was analyzed and evaluated by the total dissolution method. The total dissolution method uses a mixed solution of hydrofluoric acid and hydrogen peroxide solution to remove metal impurities adhering to the outermost surface of the silicon wafer, and then dissolves the entire silicon wafer using vapors of hydrofluoric acid and nitric acid. Then, by analyzing the residue, the metal contaminant adsorbed and diffused on the silicon wafer is evaluated. The results are shown in Table 1.
Test Examples 1 to 4 differ in boron dope amount with respect to the silicon wafer used for dissolution. In Test Examples 5 to 7, the boron dope amount for the silicon wafer used for dissolution is the same, but the silicon wafer dissolution amount is different. As Comparative Example 1, a similar test was performed using a sodium hydroxide solution containing neither boron nor silicon.
[0017]
[Table 1]

[0018]
As is clear from Table 1, it was found that Test Examples 1 to 7 in which boron or silicon containing boron was dissolved had a lower amount of nickel contamination than Comparative Example 1 in which these were not included.
[0019]
【The invention's effect】
According to this invention, since boron is dissolved in the alkaline solution, contamination of the semiconductor wafer by the metal impurities dissolved in the alkaline solution can be effectively prevented at low cost.

Claims (3)

In the alkaline solution for semiconductor wafer processing used when alkali treating semiconductor wafers,
  An alkaline solution for semiconductor wafer processing, in which boron is contained at 500 to 2000 ppb and silicon is contained at 0.25 g / liter or more in a sodium hydroxide solution having a concentration of 20% by weight or more. The alkali solution for semiconductor wafer processing according to claim 1, wherein the silicon content is 1 to 80 g / liter. An alkali solution for processing a semiconductor wafer used when alkali treatment of a semiconductor wafer is carried out by containing boron in a concentration of 20% by weight or more in a sodium hydroxide solution of 500 to 2000 ppb and silicon of 0.25 g / liter or more. A manufacturing method,
  A method for producing an alkaline solution for semiconductor wafer processing, wherein a silicon material doped with boron at a predetermined concentration is dissolved in the sodium hydroxide solution.